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OSP Hall A - Jefferson Lab

1. ok oe Nee on i 66 joco Le 67 2 83 List of Authorized 67 CONTENTS 25 Compton Pomme ei ba eo RR OE RE Ob OA USD EEE ES 3 Targets Ad OWN o Shee eee oS eR 3 2 Cryogenic Hydrogen and Deuterium Targets Ql Gas ss oe eee FE Se El ctrical Installatl n o 264 44 xA 6 4 koe Ren Flammable Gas Detectors Ud a s s hw ES dodo e a a Target CES cari uou e db uo dog ane Ttg are RUE ene Pressure Relief 222754 ee eG ES Se RCRUM E Scattering Chamber Vacuum Failure 3 23 Temperature Target Freezing o og s 4p o9 x eek RBS ee Be Ou 33 Authorized Personnel lt e so eco we 3o R OX Mace E Re oa ss 34 The Watertall Target iuis ec boe ei eo E m ees oad The hydraulic systemi e 6 0525 4 Rem RE IR Re 2 12 Cle nb ou ok Rr wea 55 4 3 13 The movement System suo dont eS 344 The slow vontrel system lt s es 2st o kx RR 34 5 Jiulhonzed Personnel 2 2 bose RRR Se x GS RE X 3 3 4 6 Safety Assessments aL Operating procedure 222 26 222 4 34 8 Troubleshooting s sc eor eea oh
2. Mode Spot Size Dispersion Position Size A ony n Stability Stability Achromat 140um 0 50um 50um Dispersive x n 4m to 12m 50m 50um Defocussed 0 to 3mm 0 10 10 Table 2 2 Line A Optics and Beam Requirements at Target Mode Spot Size Dispersion Position Size A ony n Stability Stability Energy eP d gt 100um 0 50um 50um Moller Pol d gt 250 0 50um 50um Compton Pol 801m 0 50m 50um Energy arc d 15m 50um 50um Table 2 3 Notes Line A Optics and Beam Requirements at Other Locations Build dispersion in arc section with all magnetic elements except dipoles turned off d Destructive measurements CHAPTER 2 BEAMLINE 26 Hall A BPM Readout 1495 45 MHz 0 or Q gt 1 MHz 20 dB 2 4 BW CN Filter 2 Mixer Beampipe Looking Downstream Multiplexer 125 kHz 40 to Demultiplexer 60 dB Y HAPPEX 30 kHz H Y CDDA 30 kHz 5 Y HAPPEX 30 kHz Y SL H a Y CODA 30 kHz 5 Filter 62 5 kHz Detector Multiplexer XY to EPICS Xo Figure 2 4 Schematic of the BPM readout electronics 2 2 Beam Position Monitors 4 To determine the position and the direction of the beam on the experimental target point two Beam Position Monitors BPMs are located at distances 7 524 m IPM1H03A and 1 286 m IPM1H03B upstream of the target position The BPMs consist of a 4 wire antenna array of open ended thin wire stripline
3. Rx ed ee s 159 Detectors Map of Pre shower 160 Detectors Map of shower detector 161 Aeropellayoub 4 4 e ako Rho o RR RARO RR Rn 168 Aerogel mirrors 169 Aerogel structure a aoao 170 Aerogel middle PMT 171 Aerogel reflectivity gt ue Rok erara ok eek de wt 172 Aerogel Upper Mirror lt s sotoa de Ob HE Rer 3 a o 173 Aerogel amplification chain e gt s soci ok Rex RO oH 174 Detectors Hadron Arm 177 Detectors FPP HV Termination 179 Detectors FPP Readout Board 180 Detectors FPP Readout Board i23 43 63 180 Detectors FPP Level Shifter Receiver 181 Detectors Hadron Arm Gas Panel 184 Detectors FPP Carbon Door GUI cam men SEG 189 shed diagrami uou dg we ES RE Y RE 195 Gas mass soe RERO Ed RACE RAE RE oe dnd 196 Gas Vapor 2 225 ORES LEERY b EE OR QE Re 197 Gae Dial AA uade EEG ERE AEE EES ouch dde de ded 201 Controls Schematic lt z a ra da RR deese ee RR Wood 214 Controls Hall A Main Control Screen 215 Data Acquisition Electron Arm Trigger 222 Data Acquisition Hadron Arm 223 Data Acquisition
4. ee ee e 200 250 300 290 400 450 500 nm FIG gt Figure 5 21 Typical reflectivity curve of a mirror as a function of the wavelength A of the incident light CHAPTER 5 HRS DETECTORS 173 Figure 5 22 photograph showing the upper mirror section with the planar parabolic mirrors The mirror surface is protected by a vinyl film in this picture The mirror ridge separating the counter into two halves is clearly seen This section fits over the open top of the counter in Fig 5 19 CHAPTER 5 HRS DETECTORS 174 Figure 5 23 Schematic diagram of the electronic amplification chain The total re sistance of 600 between the cathode and the first dynode is shown as three 200 resistors for sake of clarity In the actual PC boards the arrangement is of six resistors of 100 kQ each in order to keep the voltage across each resistor low and avoid surface discharge between the closely packed resistors CHAPTER 5 HRS DETECTORS 175 base It is strongly recommended to ground the aluminum exoskeleton of the counter at several spots to a common ground with the HV and signal cable ground This will further enhance safety and eliminate potential ground loops in the unlikely event of a slow and otherwise difficult to diagnose dielectric breakdown from the p metal shield to the aluminum structure or the aluminized mylar in the interior 5 5 4 Operating Procedure Operating Voltage The operating voltag
5. 192 DTI oe oS ncs eR 192 5 7 2 Gas Alarms 192 HRS Gas Supply System for Wire Detectors 193 a o deed SUR es i Bete Ne dem uou 193 Bulk Gas SUpply 525552455445 Se 56 4 a 193 Qus Ming Sta e e a e Rx exem RE Se eRe ee 194 Mass Flow Control System 194 Alcohol Bubpler ses s book ee disop aikee Fes 196 Delivery Pressure 198 5 5 9 Delivery into s es stea ka eK e 199 Distribution in the Shield Houses 199 Waste Gas Collection and Venting 200 5 84 Autherized Persontiel a s cc ooo o oo REGES 200 5 8 5 Safety and Device Protection 200 205 0 System DEPO o ROTER ROME RRR ara Brada 202 Pre Startup 222522242555 655 202 Startup Procedur ss 644454 4464 4464444040444 202 Normal Operation uu ud aus oen GE aee ERE doe es 204 Changing gas bottles 24k Rx GR Mw Rn 204 Adding Alcdh l odd BOR a 205 Setting Flow Rate 205 5 8 7 Troubleshooting Things to Check 206 Resetting a closed Excess Flow 208 Restarting flow after a power failure sls 208 Oe Maintenances Qo xoxo de ek Now deg 208 Periodic Inspections ro 6
6. gt Lh ies ma gt F D r P 1455 150 9 EN 1384 20 9 1275 gt heed gt sa me in is 1 pey gt 1575 1415 1415 1380 1600 1540 1480 1395 1400 1465 1455 1440 um gt gt gt pn m H H L ff Ls EN LN EN LN 1410 is gt gt 0 10 0 11 1 1 pe Du fae pe pe e e o n LN m Ln jej A EN rt 1 1440 A 2 p 1370 e To els _ A m m 1700 1440 1435 10 550 11 1400 a fee fe a za ue _ 2s ue a m we e mu e P IJ n z3 a gt A 1495 t3 A _ A Ed A las gt gt Lh Uh gt Figure 5 14 Typical values of the total absorption counterhigh voltages CHAPTER 5 HRS DETECTORS PreShower detector map effective from May 1997 Yorkanian vorkania ccbhaf_gov 1 4 22 3 1 1 2 0 ot 145 22 4 1A2 22 1 at 146 22 4 144 22 2 4 184 22 9 181 2 6 st 185 22 10 1B2 6L 1B6 22 11 1B3 244 22 15 241 2 12 al 245 22 16 2A2 22 13 91 2a6 22 17 243 22 14 101 2B4 22 21 2B1 285 22 22 2B2 02 19
7. 28 Dad ZI Oe uuu e ee Owe ee Ed 28 2 3 2 Authorized Personnel gt s sieca risco ow oS 30 2 4 Arc Energy Measurement 31 2 4 1 Computers and softwares used by scanners and integral 31 242 Summary of ARO operations oes s ise 32 2 4 3 Preliminary details about MEDM 33 244 Details on pulser check 2 222 222 ea tdia Ewi 33 240 HV check occ 44 9 4 d eca EERE 565 33 2 4 6 Details on EPICS check scanners 33 CONTENTS 2 2 5 2 6 2 8 24 7 Details on ioe reboot scanners o o or 2 34 2 4 8 Details on disk space check scanners 34 24 90 Details on running 222 22 222 22456 ee x E 34 2 4 10 Details on MEDM window print 35 24 11 Details on profile gt s se s serce xx eii x Ge xS 35 2 4 12 Details on gain adjustment scanners 36 2 4 13 Details on file save scanners 37 2 4 14 Detailson trip handline cs e crases anedd Bee wes 39 2 4 15 Detail on encoder change scanner 39 2 4 16 Detail on encoder re mount scanner 39 2 4 17 De tails on scanner expert task 40 2 4 18 Detail on theodolite survey of a bench 41 2 4 19 More on the theodolite menu 45 2 4 20 Summary of field integral 46 24 21 Shed access
8. Check Adjust the Purge gas pressure regulator PR 301 to insure that the delivery pressure of the inert gas taken from gas supply 3 nominally Argon is about 15 psig as registered on pressure gauge PG 301A Slowly open gas shed outlet valves MV 302 A B C to bring up the pressure in the supply lines to the spectrometers After pressure has equalized open these three valves fully Note that one or more Excess Flow Valves will trip close if the total gas flow through the three rotameters associated with these valves exceeds roughly 150 units full scale on one rotameter At each of the Hadron and Electron shield house gas distribution racks verify the presence of supply pressures gauges PG401A B and PG501A B C and set gas selection valves and needle valves to desired gasses and flow rates for each chamber Normal Operation Changing gas bottles Warning High pressure gas bottles contain significant stored energy and are potentially hazardous Handling of gas bottles should be done only by qualified trained personnel For smoothest operation used gas bottles should be replaced before their internal pressure drops below the desired regulator output pressure 1 The sequence of steps for replacing an empty gas bottle is as follows Make sure that the backup bottle is full then open its bottle valve and its manifold valve The in line check valves will prevent back filling of the empty bottle As a precaution
9. 118 Spectrometers NMR Gradient Compensation 119 Spectrometers Control Voltage Calibration for Electron Dipole 120 Spectrometers Control Voltage Calibration for Hadron Dipole 121 Spectrometers NMR Probe DAC Calibration 122 Spectrometers Collimator Box Schematic 129 Spectrometers Sieve Slit 130 od Detectors VDC Geometry e ce sarp vat eae nee OE 136 LIST OF FIGURES 9 5 2 5 3 5 4 5 9 5 6 9 7 5 8 5 9 5 10 5 11 5 12 5 13 5 14 5 15 5 16 2 17 5 18 5 19 5 20 5 21 5 22 5 28 5 24 5 25 5 26 5 27 5 28 5 29 5 30 5 31 5 32 5 33 5 34 6 1 6 2 Tl 1 2 7 3 Detectors VDC Geometry gt o esta AEE REE 5 OY ee 137 Detectors Gas Flow Schematic 139 Detectors VDC Overview gt crapa X Eo ee X X Oe YE 140 Detectors 51 e s srs si eda Ho 589 Rh e aes 144 Detectors HRSR Summary 146 Detectors HV Screen for Single 147 Detectors Average Amplitudes of HA Trigger Counters 148 Detectors 2 PMT Base 2235 boo xXx 33 OR Rn 150 Detectors 2 PMT Base oe i serek 6 5 151 Detectors 5 PMT BASS 2o 4 bod hGH EG EERE DRG 55 152 Detectors 9 PMT BAS i e o c e xe RUE REGES 154 Detectors Pre shower Counter HV 158 Detectors Shower Counter HV
10. CHAPTER 5 HRS DETECTORS 181 Figure 5 28 Circuit diagram for the level shifter receiver board boards is located at the bottom of the same rack The boards convert the signals to ECL standard levels The level shifter outputs are connected to the starts of LeCroy Model 1877 FASTBUS TDCs located in the lower electronics level on the beam left side The TDCs measure both leading and trailing edge times to allow demultiplexing The TDCs are subsequently stopped by the overall event trigger and are read out by the CODA acquisition software The data are histogrammed online by the DHIST software In depth offline data analysis requires the ESPACE software The chamber gas is presently a combination of argon and ethane about 63 and 37 by weight The Hall A gas shed is outside next to the entrance of the Hall A truck ramp Gas is routed from the Hall A gas shed mixing system to the gas panel located on the lower electronics level of the space frame and subsequently to the FPP chambers The gas system is shared with the VDCs A detailed description of the system has been written by Howard Fenker In addition the chambers are outfitted with a test pulser capability A pulse is introduced into an 8 channel 16 wire twisted pair cable on each chamber which connects to the high voltage boards at the opposite ends of each straw from the readout boards The pulse is resistively coupled through a 20 kQ resistor to the ground leg of a 1500 pF
11. ORES EZ ES 25 Polerived He Tamel 25253 RU aS es 3e 8 e e RO 4 High Resolution Spectrometers HRS CV LL uc s P dC ede ded pe eA dre BUE NIRE RU 4 11 Safety with Regards to the Spectrometer 4 1 2 Hall A Vacuum coupon sk xo 9 Rom n RU OR EUR REA Spectrometer Vacuum System Target Vacuum Magnet Vacuum System Beam Line Vacuum System Beam Exit Vacuum Sys i o ooo 9 ox Re Rx 5 Hazards of Vacuum Systems 4 1 3 The High Resolution Spectrometer HRS Magnets and Power Personnel acr ERR Ee OR D Quadr pole Magnets V s ii cu kso o o Re eG Cryogenic Procedures isra sa oe eos CONTENTS 4 First Time Check Liste 2 44 44 4244 4 4429 Rx 112 Dipole Magnet s san paa HOP oe 112 114 Operation of the HRS Magnets s scicca siio 28 ee RR es 113 ssq ere ee ed ee 117 4 2 1 Simple Spectrometer Field Setting Autopilot Mode 117 4 2 2 Dipole Field Monitoring Electron 118 22 Authorized Personnel a 44 coe or dee EO 119 424 NMR Operating Procedure lt o scs i854 o Rn 123 125 Powering Up Dipole Magnets 126 42
12. These consist of dipoles quadrupoles sextupoles and beam correctors with their standard girders and stands Starting from the beam switchyard there are eight dipoles in the arc section which along with five other smaller beam deflectors bend the beam 37 5 degrees into the hall Each dipole has a quadrupole and a pair of steering magnets correctors associated with it After the shield wall at the entrance to the tunnel into the hall the beam is essentially undeflected onto the target and into the dump The beamline optics elements are designed to deliver various optical tunes of the beam on to the physics target as well as simultaneously deliver various optical tunes at other locations along the beamline These requirements are listed in Table 2 2 For the basic beamline we are able to deliver beam onto the hall A target in the achromatic mode 3 Beam Diagnostic Elements These consist of beam position monitors BPMs beam current monitors wire scan ners superharps and beam loss monitors The wire scanners are fabricated by Saclay French collaboration and four have been installed along the beamline two before the arc section and two after the arc section They are essential for the beam energy deter mination by the arc method Another two wire scanners are installed on the bench just before the target to determine the beam position and direction of the beam at the target point with high precision and also measure the emmitance of the i
13. turbo valve open at rack 1H75B09 channel 1 _ gages operational convectron 0 millitorr at rack 1H75B09 cold cathode 5x10 4 at rack 1H75B08 actual cold cathode reading __________ Exit beam tube backing pump on at pump and operational RS valve open controlled at rack 1H75B09 channel temp manual at pump turbo on at rack 1H75B09 _ gages operational APPENDIX A HALL CHECKLIST 232 convectron j5 millitorr at rack 1H75B09 actual convection reading ________ diffuser cooler on diffuser water level ok Entrance beam tube insure that Moller turbo is on and running insure that M ller target cooler is on and operational insure that there is cooling water flow to the Moller Dipole insure that ep turbo is on and running beam line vacuum valves open visually checked instrument air compressor functioning normally all interlocks in rack 1H75B08 indicate green check 3 M ller power supplies for on lights flashing at magnets check location and operational readiness of Ion chambers correct LCW flow and pressure 100 psi supply and 60 psi return cctv cameras on and focused cctv monitors at X terminal off clear of unnecessary equipment Man lift and Forklift in truck ramp perform pre sweep of run safe boxes unnecessary personnel exit Hall move Electron spectrometer stairs clear of lower balcony ensure polar crane is positioned over the entrance beam pipe and that pow
14. 129 57 188 20 type hp sun login under gougnaud gougnaud password see Arun see Arun Disk mounted on CUE yes use cp for transfer no use ftp or rcp adl files directory arc2 adl EPICS adl standard adl file ARC6 adl arc_integral adl arc_master ad1 expert adl file expert adl arc nmr adl arc pdi adl Directive files dir arc2 ARC EPICS ioc mg standard directive file datal234 data56 magnet dir output file arc2 ARC scan_nnn data EPICS integral integral_nnn data analysis code arc2 ARC pascal arc scan sun pascal arc integral result file arc2 ARC scan_nnn data log ioc name arcioc IP 129 57 188 24 arcioc2 IP 129 57 188 21 ioc login name None target ioc password None password ioc iam gougnaud gougnaud ioc type and RAM size MVME162 8Mo MVME162 8Mo ioc boot file arc2 ioc up EPICS ioc mg up 7 OVS revision Id arc tex v 1 3 2003 06 06 15 19 02 gen Exp 8Authors A Saha mailto saha jlab org CHAPTER 2 BEAMLINE 32 2 4 22 Summary of ARC operations Six scanners of the same type called ARC scanner and labelled from scanner 1 to 6 are installed on the Hall A beamline Scanners 1 to 4 are used for the ARC energy measurement and they are located on the Hall A arc 1 and 2 just upstream of the arc in the BSY and 3 and 4 in the Hall A tunnel just upstream the Compton polarimeter Scanners 5 and 6 are located between the M
15. 2 low main supply pressure 3 high delivery pressure 4 high exhaust line pressure 5 forced airflow in gas shed 6 over temperature in gas shed or a shield house and 7 house fire alarm The Kill Gas buttons in the counting room and in the gas shed also feed into this interlock system When a fault condition occurs power to the solenoid valves controlling gas flow into the gas shed is turned off closing the valves An audible alarm sounds in both the gas shed and the counting room and one or more red lights on the interlock panels in both locations indicate the specific fault detected The audible alarm may be silenced by pressing the Alarm Override button Note that this does not restore gas flow or clear a fault After the fault is cleared it is necessary to activate the Low Pressure Override circuit by pressing the corresponding button on the interlock panel in the gas shed This CHAPTER 5 HRS DETECTORS 201 Figure 5 34 Gas Distribution inside Hall A CHAPTER 5 HRS DETECTORS 202 circuit temporarily disables the Low Pressure fault circuit allowing the solenoid valves to open up and restore gas pressure to the inlet pressure switches When pressure is restored this circuit automatically resets itself Note that the Excess Flow Valves will almost always trip immediately after the solenoid valves are re opened This is because of the sudden high flow rate which occurs when the pressure in the gas line downstream of a
16. Can 60 0 0038 long V acuum D Can 85 0 0039 long V D Window 110 0 028 J D Window 125 0 028 J D Window 125 0 028 J D Window 115 0 028 J D Window 147 0 028 J D Window 150 0 028 J D Complete Blocks 85 V Non Destructive Table 3 1 A summary of the early cell block pressure test data In the event that the pressure in the system begins to rise there are multiple vent paths to release it The first line of defense is the recovery tank The second line of defense is a small orifice solenoid valve which is slaved to a pressure transducer This valve CSV28 for and CSV57 for Dg is normally controlled by the limit output of the computer via a VME based relay readout of the pressure transducer that views the target relief line PT131 for and PT140 for D The valve itself is mounted in the fill line relief assembly The separation of the valve from its controlling pressure gauge should provide some dampening of the response and the small orifice of the valve also ensures that it will be able to make pressure adjustments gently if need be There is a separate relief valve on the fill side of the target CRV30 for and CRV59 for D This relief is mounted in parallel with the small orifice solenoid valve Right on top of the cryocan on the return side of the target there is a large size one in relief valve All target pressure reliefs are connected to the nitrogen vent line of
17. Coincidence Trigger 224 Chapter 1 Introduction 1 1 General This document contains the following information concerning the Hall A base equip ment safety assessment It is assumed that the reader of this document has been through all the required Jefferson Lab safety training Hence the material covered in those courses is for the most part not repeated here End station specific safety items are covered in The Experiment Safety Assessment Document for the Hall A Base Equipment which is required reading for all shift personnel This document also contains some safety information when deemed appropriate 1 2 The Personnel Safety System Users and staff working on the accelerator site are protected from the dangers as sociated with the prompt ionizing radiation that the accelerator beam produces by the Personnel Safety System or PSS The PSS keeps ionizing radiation out of areas where people are working and keeps people out of areas where ionizing radiation is present There are a total of five states for the Hall A Personnel Safety System Restricted Access Sweep Controlled Access RF Power Permit and Beam Permit 1 2 1 Restricted Access Restricted Access is the PSS system state when delivery of beam and or RF power is not permitted and entry to and exit from the hall is not controlled by the Personnel Safety System This is the normal state of the hall when the accelerator is off and no
18. Hadron Q1 APPENDIX A HALL CHECKLIST 236 ensure 0 current status on local power meter ensure that the set to and ADC readouts all equal 0 A turn off Q1 LCW supply valve slowly and lock it in the off position A ensure 0 current status on local power meter A ensure that the set to volts readout equals 0 A ensure that the set to current readout equals 0 J Switch off input power at power supply Switch off power at safety disconnect and lock switch in the off position ENS ensure 0 current status on local power meter A ensure that the set to volts readout equals 0 J ensure that the set to current readout equals 0 _ switch off input power at power supply _ switch off power at safety disconnect and lock switch in the off position Dipole ensure 0 current status on local power meter _ switch off input power at power supply switch off power at safety disconnect and lock switch in the off position Entrance beam tube NOTE LOOK FOR RADIATION AREA SIGN and OBEY A beam line vacuum valves closed _ turbo valve closed _ turbo off backing pump off and vented to atm _ M ller turbo valve closed M ller turbo off Meller backing pump off and vented to atm instrument air compressor functioning normally Exit beam tube NOTE LOOK FOR RADIATION AREA SIGN OBEY _ A beam tube valve closed
19. Ses qe i rf f bd i i 200 jauuey ii 2 b i EE kgj V IEH i f i CEP gm D y E gt i a See T 59 E a TET m cm x 52 od 5 O Wi it O O Y im c BS x tien GD GH Gs 71 114 i Gs i i i i i i i ot P 9ueui3 Z 2 i ii pai pe Ee Qum Hj i i i i Yy E ge n SE RU 9 cars 59 0 ES e RE 50 X V V i Q v d O O eunsseld i i A Vv c i i 1908109 i i i i uofuy i JeuueuS V E E ol i 5 i cO 8 i CUM 6 Shed Schematic Diagram Figure 5 31 CHAPTER 5 HRS DETECTORS 196 o FLOW A ORATIO move step get ser 1 1 1 i 8 e ooo 9 RAMP TIME BEHOTE 62 E 9 CAL LOCK 9 ORATIO BASE AUTO ZERO ENABLE RANGE y PROGRAM SELECT H H H 2 on e GIE 1 1 1 1 1 1 LL 1 1 D y ese cidade noces eee ee zu n gena zmLLLA5ltusetussseeseddszsc5m5nnilcd Channel 1 Channel 3 Channel 2 TYLAN GENERAL FC 280A MASS CONTRQ TYLAN GENERAL FC 280AV MASS
20. The hydraulic system that operates the vertical positioning system VPS and the horizontal positioning system HPS operates at high pressure 3000 5000 psi Therefore one should be careful when operating those systems The cryogenic system operates at elevated pressure at 4K One must guard against cold burns and take the normal precautions with pressure vessels when operating this system Only WBS7 are permitted to install and take out U tubes The magnets have a great deal of stored energy as they are large inductors Always make sure people are clear of them and that the dump resistor is attached to the magnet There are several major safety concerns with regards to the detectors namely 1 flammable gas located in the VDC and FPP 2 hazard due to in the Cerenkov CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 107 counter 3 high voltage due to the photo multipliers on the various detectors and 4 a thin vacuum window separating the detector array from the vacuum system in the spectrometers The clean agent fire suppression system while installed to suppress fires can also be a safety hazard It is possible for an individual to drop down alongside the box beam to the gantry roof inside the shield house This area although technically not a confined space could conceivably become one in the event that the clean agent system was attached Personnel should have a 5 minute air pack with them in the event they must enter the area al
21. _ beam tube turbo valve closed APPENDIX A HALL CHECKLIST 237 _ exit beam tube turbo off exit beam tube backing pump off and vented to atm cold cathode gage off convectron gages on Dump _ NOTE LOOK FOR RADIATION AREA SIGN and OBEY turn off diffuser cooler Inspect visible areas for water leaks NOTE LOOK FOR RADIATION AREA SIGN and OBEY Inspect power supply platforms spectrometers and the rest of the Hall looking for water leaks and cryogenic plumes cctv cameras off _ clear of unnecessary equipment _ Man lift and Forklift removed from truck ramp Doors unlocked CVS Id postBEAM_extended tex v 1 2 2003 06 05 23 29 59 gen Exp CVS Id all tex v 1 2 2003 06 05 23 29 59 gen Exp Bibliography 10 11 12 18 14 W Barry Pr 90 009 Technical report CEBAF 1990 26 C Hyde Wright et al Beam position studies for e93050 private communication 26 T Powers private communication 27 R D Mc Carty Hydrogen technology survey Thermophysical properties Technical Report N76 11297 NBS 1975 70 W Schmitt and C Williamson Boiloff rates of cryogenic targets subjected to catas trophic vacuum failure Technical Report 90 02 Bates Internal Report Sept 1990 76 F Duncan K McCormick and J Goity A user s guide to the hall a cryotarget control system Technical report Jefferson Lab Hall A Sept 1997 78 81 F Garibaldi et a
22. case select the Dac 5 option compute the approximate field as explained above estimate the corresponding DAC value from the table above depending on field value and probe set this estimated value in the arc nmr adl screen correct this setting by using the and buttons up to have the OUT IN T value close to the field you computed and then wait for the lock It should work you have 100s to get the lock at the begining and at the end of the integral sequence The best is to get the lock by this way before starting the integral sequence 2 4 24 Details on integral run To run the integral measurement sequence call the arc integral adl medm screen on pascall see Details on integral system check above then push start to start the full sequence look at the results displayed after the before NMR measurement the before data set after the forward integral pass the forward velocity profile and the forward voltage after gain profile after the backward integral pass the backward velocity profile and the backward voltage after gain profile after the after NMR measurement the after data set if BAD NMR or PDI saturation flags are set or if something is obviously wrong in the data or plots fix the problem see Details on integral error below and start a new integral run data are ready to be saved see Details on integral data save below 2 4
23. station This comes only at a price as the mass flow controllers deliver a fixed flow rate regardless of pressure within practical limits If the detectors in Hall A consume less gas than the mixer supplies the pressure in the supply lines will increase Similarly if less gas is mixed than is consumed the pressure will decrease To provide a usefully constant pressure of about 15 psig in the supply line a pair of pressure switches has been installed in the mixing station outlet The first of these the Primary Pressure Control Switch is set to open at 16 psig and close again at 14 psig or below When the pressure is low this switch is closed and the Flow Control System is commanded to use the flow rates set into its PROGRAM C high flow When the Primary Pressure Control Switch opens PROGRAM D zero flow is selected By setting PROGRAM C to provide just a little more gas than required by the detectors the supply pressure can be maintained at between 14 and 16 psig with a cycle time of several minutes This pressure variation CHAPTER 5 HRS DETECTORS 199 will result in a flow rate variation of no more than about 15 which should be of no consequence for the detectors A second pressure switch the Overpressure Alarm Switch is calibrated to open at 18 psig and re close at 14 psig or below If the delivery line pressure manages to exceed the 18 psig threshold it indicates a system failure of some sort and the gas interlock system is t
24. the pulses to demultiplex the wire hit Within each group of eight wires the widths are set to about 25 45 35 55 90 65 105 and 75 ns The TDCs are located in the upper FASTBUS crate located on the lower electronics level of the spectrometer space frame in the detector hut The FPP rack containing level shifter cards is located opposite the FASTBUS crates on the lower electronics level It shifts signals sizes from the reduced 50 mV readout card output levels to ECL standard levels for input to the TDCs The connections between the readout cards and the level shifter cards as well as between the level shifter cards and the TDCs are made with 16 conductor twisted pair cables A wiremap detailing the cabling is posted on the side of the FPP rack Power up Procedure 1 Ensure that gas flow has been established in the chambers as outlined in the previ ous section If it has not STOP RIGHT HERE Gas flow must be well established and steady state BEFORE the HV may be enabled CHAPTER 5 HRS DETECTORS 187 2 Ensure that all power supplies as well as the FASTBUS crate are off and the LV HV and TDC cables are connected 3 Turn on the threshold and LV power supplies Use EPICS to turn the threshold voltages up to correct values about 4 0 V for front chambers 1 and 2 and 7 V for rear chambers 3 and 4 4 Use HACI3 to turn up the chamber voltages Standard values are 1875 V for front and rear chambers It is probably best to raise
25. 0 time width 10s level 2 5V on 50 load 5V on 1 MQ polarity TTL 2 4 5 Details on HV check The energy measurement uses scanners 1 to 4 with PMT read out One PMT PMTO is in the BSY reading scanners 1 and 2 One other is in the Compton region PMT1 reading scanners 3 and 4 They both are energized by the beam line HV module card 1 channel 0 and channel 1 PMT1 under EPICS control of the general Hall A control Both voltages must be 1200V make sure that Meas V indicates this voltage If needed push on enable disable or edit the SET V field 2 4 6 Details on EPICS check scanners login as gougnaud on hac you need to know the password ask Arun Saha If you connect by cd gougnaud you will not be able to edit the command file nor save the data hac cd arc2 adl hac medm amp on the medm access window click on file and then open in the open file window select ARC6 adl the ARC window must appear then on the medm access window click on execute if then the ARC window remains partly blank or if you have some doubt about the identity of the program running in the ioc go to the reboot ioc section below CHAPTER 2 BEAMLINE 34 2 4 7 Details on ioc reboot scanners Reboot arcioc by pushing the Beamline Arc Measurement VME Reset green button middle counting room the arcioc is loaded from the up file If the ARC window execute mod
26. 10 12 The Hall A electron spectrometer is equipped with a 2 layer segmented shower counter The first layer the so called pre shower counter is made of 48 blocks of TF1 lead glass Each block is nominally 10 cm by 10 cm by 35 cm long The second layer the so called total absorber counter is nominally 15 cm by 15 cm by 35 cm viewed head on by the beam Operation of the shower counter requires the application of High Voltage HV across 5 OVS revision Id shower tex v 1 3 2003 06 06 17 00 27 gen Exp CHAPTER 5 HRS DETECTORS 157 the photomultiplier tubes and bases which are mounted on the back of the shower counter blocks for the total absorber and on the sides of the shower counter in the case of the pre shower within the confines of the protective aluminum support frame As charged particles pass through the lead glass of the shower counter they pro duce electron positron particle antiparticle pairs These particles in turn both produce additional particles and Cerenkov light which is collected in the phototubes The pulses are then amplified delayed and sent to ADCs which are gated by the overall event trigger The ADCs are read out by the CODA acquisition software The data are his togrammed online by the DHIST software In depth offline data analysis requires the ESPACE software 5 4 2 Operating Procedures Power Supplies and Electronics Procedures HV power supplies and readout electronics associated with the
27. 121 286 22 23 aA4 02 27 141 22 28 151 3A6 22 29 16 384 02 33 02 35 191 386 02 34 191 444 22 39 4A1 22 36 ans 211 446 02 41 4A 22 18 AMPSAMP Ch Slot Chan Figure 5 15 Map of the Pre shower counter detectors 18 28 aR 4R 5R 6R TR aR 9R 10R 11R 12R 13R 14R 15R 16R 17R 18R 19R 20R 21R 22R 23R 24R 15 17 19 21 23 25 27 29 31 33 34 37 39 41 43 45 47 160 161 CHAPTER 5 HRS DETECTORS Shower detector map effective from May 1997 Voskanisn vosksnis 2 ccbaf zov Gc m TA 1 rs a 1 5 ncm lt S 1L gt alas evo 6 n e T Hot as 1 E gt a LEUR m _ ncc wales a T a 7 a uw SHIL amp m 8212212 z r ADC Slot m a a m 5 ES a a ao AMP AMP Ch gt n Te 52441 m t a 21851821824 Aun le als mime se 5 z m 8 7213 g a 5261 2m ae is as Figure 5 16 Map of the shower counter detectors CHAPTER 5 HRS DETECTORS 162 e Before turning on the high voltage for the shower counters HAC5 for the preshower and HAC6 for the total absorber check
28. 25 Details on integral error BAD NMR flag is set if at least one of the 4 NMR status locked and stable before and after is wrong the full NMR field measurement is made of 3 successive elementary measurements separated by a 5s delay the lock status is set to wrong if at least one of the NMR measurements did not lock before a 100s timeout The measurement sequence is aborted as soon as a measurement does not lock so the maximum time one has to wait for a full NMR measurement is about 100s in case of a zero current measurement for example the stable status is set to wrong if the 2nd or the 3rd field values differs from the 1st by more than 5 10 4 relative In any case the field value returned is the last one In position is set to false if the probe position was outside 1604 0 0 1mm at NMR measurement time PDI saturation the PDI Mertolab s Precision Digital Integrator consists in a programmable amplifier and a VFC integrator working in the 5V 4 5V input range The PDI gain is the result of an automatic selection in the 1 2 5 10 1000 range similar CHAPTER 2 BEAMLINE 51 to the NMR probe selection In case of a wrong gain selection maximum voltage after gain as plotted in the MEDM screen outside the 1 5V 5V range call the arc_pdi ad MEDM screen to switch the gain selection mode from auto to manual and then select manuallay the gain Return to auto mode before leaving the integral measur
29. 3 2m long downstream optic limit switch for Zdj3200 8mm downstream electric limit switch for Zdj3212 3mm downstream energy damper for Zd in 3214 3238 mm The current status of the 4 limit switches is given in the arc master adl screen Optical limit switches are used for the encoder initialization procedure see Summary of field integral above Electric limit switches should never be activated But if this happens then the motor control stops the motor raises an error flag the letted d for defect is displayed inside the power box the usual display being a vertical segment waits for a manual repositioning of the probe inside its allowed range and for a reboot of the VME The manual repositioning of the probe inside its allowed range can be done safely by manipulating the motor shaft while the motor power is off according to the above procedure 2 4 81 Details on detailed field mapping The main use of the integral setup is to measure the integral of the 9th dipole along a straight line located on the axis of the pole tips By moving manually the dipole in the transverse direction and then performing the integral sequence one will measure the integral along different axes and hence extract the gradient of the dipole integral used to determine the dipole positionning tolerances By inserting a jumper short on one of the pick up coils and reducing the gain of the PDI the same sequence as for the integral will pro
30. 3 5 For the calculation of the boil off rate the target was split into two pieces the cells plus cell block both aluminum and the heat exchangers plus the connecting plumbing all steel The mass evolution rates for the two pieces were then added in order to find the total mass flow rate Fluid and Phase Property Symbol Value Hydrogen Liquid Temperature T K 22 Density p kg m 67 67 Specific Heat C J kg K 11520 Enthalpy of Vaporization H J kg 428 500 Hydrogen Vapor Temperature T K 22 Density p kg m 2 4991 Viscosity kg sm 1 29 10 9 Specific Heat C J kg K 13 550 Thermal Conductivity k W K m 0 02 Volume Expansivity BK 0 00366 Air Temperature T K 273 Pressure P Torr 760 Density p kg m 1 224 Viscosity kg sm 1 8410 Specific Heat C J kg K 1005 Thermal Conductivity k W K m 0 0244 Volume Expansivity Bk 0 00367 Table 3 3 The properties of the gases used to calculate the heat transferred to the target during a catastrophic vacuum failure CHAPTER 3 TARGETS Quantity Cell Block Piping Heat Exchanger Total D 2 5 in 0 063 m 1 5 in 0 038 m 0 1778 m k 55 W K m 6 5 W K m 6 5 W K m A 0 146 m 0 185 m 0 216 m 0 510 m V 0 001 m 0 0019 m 0 002 m 0 0054 m x 0 004 in 0 0001 m 0 065 in 0 00165 m 0 12 in 0 003 m q
31. 3 5 7T 0 2 8B 1 0 8T 0 1 9B 0 5 Table 5 4 As in table 5 3 but for the center hit location configuration the pins during movement it also helps seal the interior of the counter from the outside environment and reduces leakage rate Reverse the process for installation Installation and Removal of the SiO Tray PLEASE NOTE The SiO aerogel panels are extremely fragile and sensitive to water and chemical vapour Do not handle with bare hands use clean cotton or other fabric type gloves instead Surgical gloves often are contaminated with lubricants and are not suitable for this purpose The tray is secured to the main section by hex bolts Removal of the bolts results in the straightforward removal of the tray There is minimum clearance between the tray walls and the main section as a result the tray has to be removed and installed in a uniform translation with respect to the main body The frame supporting the fish net or tennis racket can be removed from the tray proper by removal of the two small screws in the middle of the tray walls and a tool hook is provided for this operation The SiO aerogel panels can now be removed or replaced Reverse the procedure for installation The securing bolts do not need to be tightened very much and although spacers are inserted between the rubber strips to prevent damage care and common sense should be exercised Light and gas sealing is provided by the rubber strips NOT by brute f
32. 4 3 2 1 0 2m 1000 1200 Dpde Figure 4 9 Control Voltage calibration for Electron Dipole CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS Hacron vs Bus Figure 4 10 Control Voltage calibration for Hadron Dipole 121 CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 4500 4000 t 3500 4 3000 2500 4 K DAC 2000 t x a 3 Hp 2 m 4 Fit 4 1000 Type 5 Fit 5 500 4 ji I 7 0 4 0 0 5 1 1 5 B Tesla DAC Cy CyB Cp B C4 B Probe type Co C3 Group 0 Probes Group 1 Probes 3 5157 04 E 48 o 57 82559 35 0 3 4 5157 39 22514 30 23920 73 10320 28 1 4 5 5156 74 11255 70 5979 12 128979 2 5 Figure 4 11 DAC Calibration for manual operation of NMR probes 122 CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 123 4 2 4 NMR Operating Procedure When running in Autopilot mode see Simple Spectrometer Field Setting the compen sating coil voltage is set automatically and the probe appropriate for the field desired is selected The gaussmeter is placed in SEARCH Mode and the dipole power supply regulator is turned on In this case the dipole current is adjuste
33. A Trip Voltage 1 2V value Coil B Trip Voltage 1 2V value Magnet Lead A Trip 1 2V Magnet Lead B Trip 70mV value Magnet lead A must be connected to the PS Level Trip 7096 value Magnet Flow A Trip 60 SLPM value Magnet Flow B Trip 60 SLPM value Operational Test of trips PS overcurrent trip 2000A See manual for voltage setting and gain 4V 800A Magnet Ready for Operation Table 4 1 Hall A Dipole Magnet Check List 15 August 1996 114 signature date Magnet Leads are not bipolar and only work in the PS forward polarity CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 115 Circuit Parameters Rext 0 075 Q L 25 mH Tau 0 3 s Vthreshold 1V Imax 3250A Magnet Circle one Q1 Arm Circle one Electron Arm Hadron Arm Visual inspection walk through Set water pressure at 100 psi inlet Coil A Trip Voltage value_25mV Coil B Trip Voltage value_25 mV Magnet Lead A Trip Voltage_80 mV __ Magnet Lead B Trip Voltage_80 mV Level Trip percent 98096 Magnet Flow A Trip 30 SLPM4 setting Magnet Flow B Trip 30 SLPM setting Operational test of trips Magnet Ready for Operation Table 4 2 Hall A Q1 Quadrupole Magnet Check List 15 August 1996 Circuit Parameters Rext 125 Tau 3 s Quench Vthreshold 1V Imax 1850A Magnet Circle one Q2 Q3 Arm Circle one
34. Even though the diffusion length in silica aerogel can be quite short for low A light generated in the 510 radiator 13 enough directionality remains in the visible region where the selected PMTs have good quantum efficiency to make light collection with mirrors an attractive and practical al ternative An effective segmentation of the aerogel Cerenkov counter matching the segmen tation of the trigger scintillators can be used to separate multiple tracks through the focal plane and will allow an additional element of selectivity and track sensitivity in the focal plane instrumentation This means that specific sections of the focal plane can be physically disabled from the trigger if the experimental conditions require it It will also provide the capability of identifying and separating pions and protons traversing the focal plane trigger scintillators and the vertical drift chambers VDCs within the resolving time of the system double hits For example in the offline analysis the aerogel counter PMT with the highest number of photoelectrons can be matched with the trigger counter and VDC information to identify the actual path of a pion thus separating it from a simultaneously detected proton which has no Cherenkovsignature Such a capability of double hit resolution is not possible with diffusion Cherenkovcounter designs because the photon collection efficiency does not have a strong correlation with the incident particle track wit
35. HRS VDCs are all commercially designed The reader is directed towards the manuals made available by the manufacturer for the detailed information not provided here The LeCroy HV power supply provides 1500 V nominal to the total absorber and 1200 V to the preshower The power supply is located in the detector hut in a NIM bin on the upper level of the space frame This unit may be controlled either manually or remotely via the EPICS control software and also provides a monitor of the current drawn by each phototube to which it is attached Connections from the power supply to the base are made using standard SHV connectors mounted on red RG 59 U HV cable good to 5 kV Typical values of the high voltages are shown in the tables for both the pre radiator and the total absorber If at all possible the HV and LV power supplies should be left on continuously This allows the tube noise to quiet down after high voltage is applied and the temperature of the base components stabilizes Signal Handling Summing Amplification and the Multiplexer The upstairs electronics racks hold two NIM bins containing the summing modules of the multiplexer The output of these is sent to the ADCs Both the individual channels and the sum of every six channels is sent into an ADC where it can later be analyzed by the software The operations manual for the multiplexer was written by Breuer UMd and is available from him upon request The detector signals are physic
36. LL ul 400 22 200 Ea 0 4 6 HS2L HS2R Figure 5 8 Average Amplitudes of HA Trigger Counters CHAPTER 5 HRS DETECTORS 149 The actual base with the socket and the dynode chain is a separate part actually an assembly of parts 09 19 The rear tubular housing 07 completes the assembly and encloses the dynode chain and wiring The three main sections join at the coupling nut 14 which threads partly inside the front tubular housing while the rear tubular housing threads on the remaining part The PMT and the electronic amplification components are mounted on a P C board 15 which is enclosed in an aluminum Faraday cage This assures rigidity and protection from stray RF fields The mu metal shield is at cathode potential to minimize the dark current due to capacitive discharge in the photo cathode glass window 5 3 6 Handling Considerations Assembly Instructions Unscrew the rear tubular housing from the coupling nut and then unscrew the front tubular housing from the coupling nut Remove the mu metal shield 10 from the retainer ring 12 by loosening the nylon locking set screw 11 After insertion of the PMT in the socket install the mu metal shield and make sure it sits squarely in the bottom of the socket base 13 WARNING The mu metal shield should NEVER be assembled in the base without the plastic insulator ring 09 Electrical shock may result if someone touches the ou
37. Non Invasive Hall A BCM Calibration Procedure The extended calibration procedures involving the Faraday Cup 2 and the OLO2 monitor at the Injector are presently per formed by A Saha The Accelerator AES group performs the maintenance of the BCM monitors These include 1 The Unser calibration Every 3 months 2 Resonant Cavities Tuning Every Downtime 3 Multi meters Autocalibration Every Downtime 4 Connectors Cleaning Every year 5 Unser Keithley Current Source Calibration Yearly 6 Digital Multi meters HP3458A and HP 34401A Calibration Yearly System Contacts Arun Saha x 7605 Jean Claude Denard x 7555 CHAPTER 2 BEAMLINE 2 4 Arc Energy Measuremen t 78 3l The ARC energy measurement is under EPICS control through a MEDM display Two independent control systems are used the beam bend angle measurement through the arc scanners and the field integral of the arc integral To measure the energy e perform several angle measurements e perform an integral measurement e analyze the integral measurement and note the value of the arc field integral e analyze the angle measurements average the results proposed by the software then ask for the energy calculation enter the above arc field integral and you will get the beam energy computed from the average angle 2 4 1 Computers and softwares used by scanners and integral SCANNERS INTEGRAL Computer hac pascall IP
38. SRAY S1 S2 C A ee SRAY S1 C G C A to SCALERS GRAY 1 1 4518 100 SRAY S2 C G C A 4564 C A OR DELAY FO OR 17 20 to SCALERS 4518 100 DELAY FO LeCroy Model Number modular to TDC FUNCTION fixed imes used blank if 1 dela fixed to ADC able delay CAMAC CRATE SLOT CAMAC Module Notation to ADCs AMPLIFIER SHOWER 1 96 HALL A ELECTRON PROMPT TRIGGER DESIGN 11 13 97 Figure 7 1 Electron Arm Trigger Circuit CHAPTER 7 DATA ACQUISITION AND TRIGGER 223 Must be added to allow S1R to be included in strobe but maintain tch 1 1 to ADC PES row ed 2 S2R timing able dela 1 13 to SCALER to TDC S1R OR ECL 1 12 14 oR S2R OR Phillips NIM 4413 200 4518 100 4518 100 4518 100 rear panel out to S1R 1 6 gt 1 6 ECL gt NIM fixed DISCR DELAY FO DELAY FO DELAY FO able dela NIM S2R 1 6 7 12 1 12 14 j hie 1 22 23 Hl 1 4 1 1 H1 17 pulsersi4 RETIMING DELAY to SCALERS ABC1 ENABLE 1 gt 8 4518 100 2373 2 gt 51 AND DELAY FO MLU 3 gt 52 08 1 52 7 12 1 8 1 10 INPUT B pulser 14 1 12 14 7 S1 OR OR S2 OR to SCALERS ABC2 4413 200 4518 100 S1L 1 6 gt 1 6 DISCR DELAY FO to SCALERS ABCO S2L 1 6 7 12 1 12 14 pulser gt 14 H1 14 H1 12 1 12 14 1 12 14 modular to TDC 860 ns PROMPT TRIGGER T3 to ADC SRAY ixed patch 1 row 2E2ble dela to SCALERS ABC6 iy 8 100 2373 4518 1 7 ANALOG SUMP1l 4413 200 C G SUM 52 DELAY FO MLU DISCR Al A10 1 11 1i 1 10 H2 2 H2 4 C
39. VDC on the frame and location of the Thompson rails is surveyed relative to the Hall center The rest of the detectors are mounted on a detector frame which can be moved out of the Shielding Hut for detector maintenance 5 1 1 Geometry of the Spectrometer Detector Packages Tables 5 1 and 5 2 give geometry information for the electron arm and hadron arm detector packages The values in the tables indicate the position of the central point of the detector The origin of coordinate system 0 0 0 is located at the intersection of the mid plane of the spectrometer and the nominal focal plane middle of the Bottom VDC detector location location width width BEAM ENVELOPE actual IDEAS model X Y X X VDCI 0 1942 271 843 R24 57 VDC2 572 1942 271 932 911 85 51 1311 1321 1718 356 696 1022 163 AERO 1646 199 414 709 888 182 GAS 2535 2200 650 886 1110 279 52 3858 3878 2197 540 897 1124 285 preSHOW 3502 3546 2400 700 925 1158 301 SHOW2 3780 3912 2400 900 964 1207 322 Table 5 1 Locations of the detectors on Electron Arm in mm CHAPTER 5 HRS DETECTORS 135 detector location location width width BEAM ENVELOPE actual IDEAS model X Y X X Y VDC1 0 1942 271 843 824 57 VDC2 500 1942 271 932 911 85 S1 1287 1760 360 675 845 163 AERO 1617 1872 414 709 888 182 1837 1780 480 738 924 198 GAS 2409 2200 650 857 1073 263 SC2 2952 20
40. VPS and a portion of the shield house load through the inboard legs of the gantry the gantry which supports the shield house and the magnet power supplies and the bogies which support the cradle gantry assembly and slide on the floor plates and provide the driving power to move the two spectrometer arms The detector package is supported on the box beam and is surrounded by the shield house It must perform two functions tracking and particle identification PID The most important capability of focusing spectrometers is measuring precisely the momenta and entrance orientations of the tracks Momenta resolution of 1074 is obtainable consistent with the resolution of the incident beam A particle traversing the detector stack Figure 4 3 encounters two sets of horizontal drift chambers x y with two planes of 368 wires in each chamber The track resolution is 100 From the chamber information both positions and angles in the dispersive and transverse directions can be determined The information from these chambers is the principal input of the tracking algorithms The chambers are followed by a scintillator hodoscope plane designated S1 This plastic scintillator array provides the timing reference for the drift chambers and is also used in trigger formation and in combination with a second hodoscope pair it can provide time of flight particle identification These scintillators can also be used to perform crude tracking CHAPTER 4 H
41. also indicated locally by a mechanical pressure gauge attached to a two stage regulator A pressure regulator for each type of gas reduces the pressure to approximately 45 psig This is the pressure at which gas is supplied to the gas shed It may be monitored by the outlet pressure gauges PG 021 022 023 on the pressure regulators and inside the gas shed on gauges PG 131 132 133 Prior to entering the shed the gas passes through manual valves MV 031 032 033 Excess Flow Valves XF 041 042 043 and Solenoid Valves AV 051 052 053 The Excess Flow Valves automatically close if the flow rate exceeds about 4 slpm at 45 psig These valves must be manually reset after they trip Refer to the section Resetting a closed Excess Flow Valve for this procedure The solenoid valves are electrically operated 24 VDC normally closed valves Power must be supplied to the solenoids in order for gas to flow Valve power is supplied when interlock conditions are satisfied 23 CV S revision Id gas full tex v 1 2 2003 06 06 21 41 39 gen Exp Authors J Segal mailto segal jlab org CHAPTER 5 HRS DETECTORS 194 by the Gas Interlock System Note that one of the required interlock conditions is that there be ample gas pressure downstream of the solenoid valves System operators must use the manual Low Pressure Override pushbutton on the interlock panel in the mixing room in order to initially bring up the 45 psig supply pressure The
42. and 3 5 The three foils are parallel and identical Each foil is 12 mm wide guided by two poles each of 2 mm by 2 mm cross section In the direction normal to the target the foils are 22 mm apart The normal direction of each foil is 30 with respect to beam line and the normal direction points towards H arm The center of each foil is shifted 1 mm along the foil direction and towards E arm see Figure 3 3 The tolerance of the machining is less than 0 2 mm CHAPTER 3 TARGETS Layout of the Target 1660 330 Be window 25ym of stainless steel window Kapton Figure 3 2 A cutaway of the waterfall target cell Beam Direction Figure 3 3 Detailed view of the 3 waterfoils geometry 84 CHAPTER 3 TARGETS 85 Aff s ya af f f Ms gt 47 gt NOT IN SCALE Figure 3 4 Cutaway view of the waterfall target container Figure 3 5 Side view of the waterfall target container CHAPTER 3 TARGETS 86 A solid target ladder is attached to the bottom of the waterfall target container which holds up to 5 solid targets The water coming back to the container goes through two cylinders in contact with the side of solid target holders providing some cooling for solid targets 3 4 1 The hydraulic system The hydraulic system is a closed circuit loop see Fig 3 1 and 3 6 Water is pumped from a stainless steel wa
43. and safety 48 2 4 22 Details on integral system check 48 24 23 Details on NMR lock sss seos uuo RR RE RE 48 24124 Details on integral 2 50 2 4 25 Details on integral error 50 24 26 Details integral data bave 2 2 2 2 51 2127 mteri ioc FOhOOL 24 9 dw 24 4 52 2 4 28 Details on temperatures 2 c eco Rom RE RR ARR y c9 ke 53 2 4 29 Details on AC power integral 54 24130 Details mechanics integral 4 5 2 sor REX s 54 2 4 81 Details on detailed feld mapping 55 eo ee Ree Cc 58 Torpet Chamber cscs 2 oe pw b Rem ee ee eee OLE ee 59 Target Chamber Spectrometer Coupling 60 Stress Analysis of the Middle Ring 60 Vacuum Pumping System osca 929g ox 61 Bremsstrablung Radiator lt sora rec 4 6 RRR RR 62 ZI VERVIEW 2 264 RS Sy ROE Se Glee ee 62 212 Salety Ieeues 6444246349 a 62 20 2 255 ee ow aee ee Hw ek 62 2 1 1 Special Instructi ng s s ra e ie ao p aea e p 55 4 64 M ller Polarimeter 2 22 4 244999 o RR EE ee 65 241 Purpose and Layout 65 2 8 2 Safety Assessment 66 T 66 Vacuum Syste e ple eo eee Mak 66 High
44. are labeled MV 411 412 in the Electron Arm and MV 511 MV 516 in the Hadron Arm The three way valve associated with each detector may be used to select either operating or purge gas independently of the other detectors The selected gas is supplied to the inlet of a needle valve rotameter combination labels MV 42x and MV 52x which is to be used to set and observe the gas flow to each detector The rotameters are sized for reasonably accurate metering of 5 slph Argon Ethane and purging at about ten times this rate Note that the gas mixer will supply a total of only 60 slph Argon Ethane limited by the capacity of the Ethane mass flow controller On its way from the rotameter to the detector the gas passes by an overpressure relief bubbler which is basically a manometer filled with mineral oil The overpressure bubblers are set to release at a pressure greater than about 30 mm of water 33 mm mineral oil This pressure is sufficient to allow purging at the desired rate Gas returning from the detector passes through an electronic mass flow meter and through a low pressure CHAPTER 5 HRS DETECTORS 200 oil bubbler This bubbler prevents backstreaming of waste gas into the detectors The flow meter reading is indicated locally on a LCD display and is available as an analog signal for connection to the slow controls computer Note that these digital flowmeters are factory calibrated for Nitrogen To correct the readings for Argon multiply by 1
45. at NMR measurement time are recorded before and after To perform an integral field measurement 1 check if the system works see details on integral system check below 2 run the above integral sequence see details on integral run below 3 fix the error s if any see details on integral errors below 4 save the data in a file see details on integral data save below 5 analyze the data see Arun Saha CHAPTER 2 BEAMLINE 48 2 4 21 Shed access and safety For safety reasons the access to the shed is limited to authorized persons which are listed in the ESAD To be added to the list ask the Hall A leader The standard operation mode of the integral measurement setup is the remote mode through the network from the counting house In case of problem needing an access in the shed unauthorized users must contact Arun Saha 2 4 22 Details on integral system check First from any workstation or X terminal connected by telnet to pascall workstation run MEDM with arc master adl data file see Arun for the password of gougnaud on pas call and the first subsection for the path of arc_master adl If pascall is not responding go in the shed and check UPS see Details on AC power integral below If the UPS is not beeping check the room temperature If the temperature is above 35C the thermal protection of the workstation is probably activated see detail on temperatures below If the temperature is below 35
46. at target 234 APPENDIX A HALL CHECKLIST 235 turbo off at rack turbo valve closed at rack switch backing pump off and bled up at pump gages operational windows functional Spectrometers NOTE LOOK FOR RADIATION AREA SIGN and OBEY turbo valves closed at valve controller in rack 1H71 72B08 switch turbo off at turbo controller in rack 1H71 72B08 blower off at controls under spectrometer pump valves closed at valve controller in rack 1H71 72B08 switch convectron gages on cold cathode gages off at gage in rack windows functional Electron Ql ensure 0 current status on local power meter ensure that the set to and ADC readouts all equal 0 turn off Q1 LCW supply valve slowly and lock it in the off position ensure 0 current status on local power meter ensure that the set to volts readout equals 0 ensure that the set to current readout equals 0 switch off input power at power supply switch off power at safety disconnect and lock switch in the off position ensure 0 current status on local power meter ensure that the set to volts readout equals 0 ensure that the set to current readout equals 0 switch off input power at power supply switch off power at safety disconnect and lock switch in the off position Dipole ensure 0 current status on local power meter switch off input power at power supply switch off power at safety disconnect and lock switch in the off position
47. at the Vacuum System equipment rack located on the Balcony Selective equipment will also be monitored from the Hall A counting house All control is by Accelerator in the MCC Beam Exit Vacuum System Vacuum for the target chamber is supplied by an Alcatell 880 s Turbo pump backed by an Alcatell 21 cfm 2 stage vane pump which maintains a 121074 vacuum on the exit beam pipe Between the target chamber and the exit beam pipe there is a 007 in kapton window that has 0375 in hole in it at the beam spot This window acts as a differential pumping station Also between the target chamber and the exit beam pipe is 8 in air actuated gate valve that is operated from the MCC Vacuum readouts and interlocks outputs are supplied by an HPS 7 Series 275 mini Convectron and an HPS series 421 Cold Cathode gauge which are located near the balcony Controls are interlocked to the beam CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 110 The chamber is made of a low mass aluminum corrugated vacuum tube of 1 m diameter At the exit point of the exit beam pipe is a beam diffuser that consists of 2 025 in beryllium windows with a water filled cavity between them for cooling The water is circulated through the cavity by a water cooling system located on the Hall floor and is interlocked through the FSD system with 2 flow switches one on the supply and one on the return line Due to high radiation levels at the exit beam pipe all seals in this a
48. battery 2 autocollimation batteries and chargers are stored in the shed make sure the batteries are charged push the ON Enter button the bottom display prompts V zero 1 release the V break small knob of the top pair of knobs initialize the V Vertical angle encoder by turning slowly and continuously the optics around the horiz axis in a direction until you get a beep and V zero 2 displayed Then turn in the opposite direction until you get a beep and A zero displayed in the top display release the A break small knob of the bottom pair of knobs initialize the A Horizontal angle encoder by turning slowly and continuously the whole theodolite around its vertical axis until you get beep and Theo displayed in the top display Push ON Enter button to accept the proposed theodolite menu from this point V and A angles will be permanently displayed in their own displays in units of decimal degrees from 0 0000 to 359 9999 If the decimal part is not displayed correct the levelling Note the origin of the A angles is arbitrary this is not the case for the V angles so you may decide to set it to zero for example at the first autocollimation measurement this way the measured angles will be more intuitive To do this from the THEOD menu push on means go to the next menu called SET SET A menu is proposed push enter to accept you have a WAIT displayed after which the a
49. be stored in gougnaud arc2 ARC As the file is big 2 7000 channel histogram per scanner purge or compress your own data files gougnaud belongs both to hac and the CUE thanks to Javier So you do not need ftp to copy it inside the CUE the cp command works as far as you have the good file access Write in the e logbook the final path of the file in the CUE Example of scan file scan 159 data version 2 ITHU MAY 27 12 55 25 1999 ICW CW 60Hz beam time structure 5 000 Microamp beam current in microamp ACHRO DISPersif ACHROmatique arc optics tuning data1234 Command Filename 1 P 1 5 Current Command Line ITHA1CO7A a p TJ_Device_Name 1 1 p Displacment X dimensionless X beam left 10 p Displacment Y dimensionless Y top vertical Z beam 1 Serial Number 1235360 p Fiducial To Beam Micron at survey scanner position 1 Cartridge Serial Number 181270 a p Cartridge Range Micron 120 Wire Diameter Micron IW Wire Material p Number Of Wire 120 p Survey_Wire_Diameter_Micron Wire used for above data 1284375 257840 234730 p Fidicial To Wire Micron 1 707 0 5 p Differential Fiducial Wire per micron of wire diam 144 97 45 04 0 06 p Angle Degree around Z axis 0 when perp to displ 10 0 00315 0 p Differential Angle Degree Per Micron of wire diam 14096 Home 1118405 p Encoder Survey Survey of 11 Aug 98 11 a p Encoder Sign 1 if increase a
50. block is split in the middle 17 OVS revision Id tex v 1 3 17 00 27 gen Exp CHAPTER 5 HRS DETECTORS 178 so that it may be moved into or out of the proton paths so that the total thickness of scattering carbon may be adjusted The block thicknesses from front to rear are 9 22 9cm 6 15 2cm 3 7 6cm 1 5 3 8cm and 0 75 1 9cm The block positions are controlled through EPICS the controls may be reached through the Hall A hadron spectrometer detectors menus Particles passing through the carbon analyzer can be absorbed in it The straw chamber planes are designated as X U and V planes The central ray defines the z axis X wires measure position along the dispersive direction The UV coordinate system is created by a 45 degree rotation in the transverse plane of the XY coordinate system with U between the X and Y axes and V between the Y and X axes The straw chamber operation is described in the following paragraphs When a charged particle passes through the chamber in typical Jefferson Lab operat ing conditions there will be about 30 primary ionizations of gas molecules Positive high voltage of about 1 8 1 9 kV is applied to the wire in the center of each straw Electrons from the ionizations drift towards the wire When the electrons get within about 100 of the wire the gain in energy between collisions with gas molecules is sufficient that gas molecules are further ionized in co
51. breaker boxes in the hall 3http hallaweb jlab org news minutes walkschd html CHAPTER 1 INTRODUCTION 16 Figure 1 2 Schematic of the Hall A showing the location of the circuit breaker panels Chapter 2 Beamline 2 1 General Description 2 1 1 Introduction The control and measurement equipment along the Hall A beamline consists of various elements necessary to transport beam with the required specifications onto the reaction target and the dump and to simultaneously measure the properties of the beam relevant to the successful implementation of the physics program in Hall A The resolution and accuracy requirements in Hall A are such that special attention is paid to the following 1 Determination of the incident beam energy 2 Control of the beam position direction emittance and stability 3 Determination of the beam current total charge and polarization Table 2 1 gives a listing of all the various elements along the Hall A beamline from the switch yard to the dump Figures 2 1 2 2 2 3 show a schematic of the Hall A line starting at the shield wall The basic Hall A beamline consists of the following 1 The Beam Entrance Channel The beam entrance channel consists of stainless steel tubing connected with conflat type flanges The usual opening is 2 5 inches for better vacuum conductance except through magnetic and beam diagnostic elements where it is usually 1 inch Sections are isolated by vacuum valves and
52. capacitor and thence into the straws After propagating through the straw the pulse enters the readout board A pulse of about 1 V amplitude in the twisted pair cable is sufficient to provide a few mV signal into the readout boards resulting in a logical output signal The system may be used to test the functionality of each readout channel and or the continuity of the high voltage wire in each straw The system currently is only implemented for manual operation except that data may be read out through CODA This procedure requires some familiarity with trigger logic and setup should only be done by experts and is not documented here http www jlab org Hall A document HAWGS HAWGS_OpMan html CHAPTER 5 HRS DETECTORS 182 5 6 2 Operating Procedure Gas Flow Operating Procedures The chamber gas is mixed 63 37 by weight Ar ethane The gas is mixed in the Hall A gas shed which is located next to the entrance to the Hall A truck ramp One needs key 8 which is located in a key box in the Hall A counting house to get inside the shed where the gas mixing is done The argon and ethane bottles which feed the gas mixing system are located outside the shed and can be exchanged when they are empty The mixed gas is sent down into Hall A and to each of the detector huts There are two each of argon and ethane bottles connected to the gas system and a Matheson 8590 controller switches between the two bottles when the gas pressure in the bottle
53. computer CODA name where computer is the internet name and the CODA name is the name runcontrol calls it hallasfil ROC1 hallasfi2 ROC2 hallasfi3 ROC3 halladaq1 TSO halladag4 TS1 hallavme2 ROC15 and hallavmel ROC14 Note for 1 TS mode you don t use ROC15 and sometimes ROC3 which has FPP is left off for good reasons You can check if the ROCs are up by looking on the Components work space at the telnet session if it s not logged try to telnet in If the ROCs don t talk to runcontrol you can type reboot at the arrow prompt gt gt If you don t get this arrow prompt or if you can t telnet in the computer is hung up so press for a full 5 seconds the labeled green button corresponding to this ROC in the middle room of the counting room After the ROC comes back 2 minutes telnet back in to verify it s up e Start runcontrol interactively by typing runcontrol Iconize and ignore the win dow from which you started runcontrol e In runcontrol press the Connect button After connect wait 10 seconds and press Run Types You may also press the Reset button in the upper left corner Indeed sometimes reset is all that s needed to fix CODA Choose the run type from the dialog box see section on Running CODA for descriptions of run types e After you configure and download the Run Type you can Start Run to start a new run CHAPTER 7 DATA ACQUISITION AND TRIGGER 22
54. counting room using the PGA Controller knobs Near these knobs is also located an oscilloscope X Y trace of the current in the raster A fast shutdown FSD shuts the beam down within 0 1 msec if the raster fails thus affording some protection of the target NOTE If you are unsure of the status of the raster measure the spot size with very low current lt 24A or with the target out of the beam An unfortunately common and potentially fatal error is to check the beam spot size with high current on target by the time you check it the target might already be destroyed The rastered beam spot on target can be checked with plots in ESPACE or by using the stand alone code called spot Spot is probably already running somewhere it runs on the Linux or Sun computers in the counting room if it s not running type spot When a new CODA run is started spot automatically clears its histograms and displays in a window the X Y beam position monitor coordinates from the first few thousand events from the start of the run For more details on usage type spot h help OVS revision Id raster tex v 1 3 2003 06 06 15 19 03 gen Exp 10 Authors 7 mailto 0jlab org CHAPTER 2 BEAMLINE 59 2 6 Target Chamber 1 The Hall A target chamber is a large evacuated multistaged can that contains the target struck by the CEBAF electron beam The chamber was designed to isolate the beam line vacuum from each HRS so that each HRS co
55. current to the Q1 quadrupole coils is provided by Danfysik System 8000 power supplies which can operate up to 3500 A current and 5 V The power supplies will be cooled with a combined maximum water flow of 45 liters per minute In addition to the main quadrupole windings all quadrupoles have multipole wind ings To further optimize focusing properties of the HRS magnet system it was intended to operate including some of these multipole trim coils in order to reduce higher order aberrations The operating current for these multipole corrections is small only the mul tipole corrections are typically less than 2 of the main quadrupole field of order 50 A and will be provided by thirty two Lakeshore power supplies These power supplies can operate up to 100 A current and 30 V voltage Since the sextupoles were inadvertently installed rotated 90 from their correct orientation these trim coils are now considered useless and there are at present no plans to use them Cryogenic Procedures All cryogenics control is handled by WBS7 The cryo control coordinator can be reached at the CHL x7405 or by calling the MCC First Time Startup Check List See attached check lists for all quadrupole and dipole magnets Tables 4 1 4 2 and 4 3 Dipole Magnet The dipole by virtue of its field index provides both dispersion and focusing The present operations envelope states that the supply for the electron dipole may not be operated at a curre
56. data 6 CVS revision Id online analysis tex v 1 1 2003 06 06 15 38 43 gen Exp Authors R Michaels mailto rom jlab org CHAPTER 7 DATA ACQUISITION AND TRIGGER 226 7 3 22 Dataspy and Dhist Dataspy and Dhist are online diagnostic programs whose purposes are 1 To print out randomly sampled detector data and 2 To automatically plot to the screen histograms of online data Dhist is actually a shell script which runs the executable dplot For some online help simply type dataspy or dplot These codes analyze a random sample of of raw uncut data in real time from the CODA computer The data are distributed on the network by a server which obtains data from shared memory This paragraph assumes you are on shift and wish to run dhist While dplot can run in several ways let s be definite Log in to adaqh2 or s3 as account If dhist isn t running type dhist Now you will see a reminder of what directory to go to and that you should type dhist there There are optional interfaces dopte and dopth for turning on off the histogram pages The dopte h interfaces also show an alarm status for the histograms by statistical comparison to a set of reference histograms To start these interfaces type dopte or dopth for the E arm and H arm respectively dhist makes about 20 pages of plots which pop up on the workstation screen and remain for a few seconds in succession Each pa
57. detector gas sys tems Unexpected maintenance requirements should be handled by contacting Jack John Segal pager and phone are both extension 7242 Hall A Technician on call 5 7 2 Gas Alarms In Counting Room A there are two alarm panels associated with the gas systems for the detectors They are located on the far left end of the control console mounted one above the other The upper panel is a Gas Master flammable gas monitoring system The lower panel is a gas systems status indicator The Gas Master system will go into alarm if elevated levels of flammable gas are present in either of the Detector Shielding Huts or the Gas Shed The Gas Master system will also go into alarm if the magnets vent cryogens The gas systems status will alarm if any of a number of faults are detected in the Hall A Wire chamber Gas System The led for the specific fault will turn red to indicate which fault caused the alarm Response to an alarm should be to contact either of the personnel listed above 21 CVS revision Id gas tex v 1 3 2003 06 06 17 00 27 gen Exp 22 Authors J Segal mailto segal jlab org CHAPTER 5 HRS DETECTORS 193 5 8 HRS Gas Supply System for Wire Detectors 77 24 5 8 1 Overview The detector systems in both HRS s FPP and VDC are expected to use a mixture of Argon and Ethane in roughly equal proportions plus about 1 ethanol The Argon and Ethane are supplied from high pressure gas bottles They are combined in the desired
58. drops below a certain level At this point the one bottle can be replaced while the other is being used The procedure for changing gas bottles is outlined below 1 Warning High pressure gas bottles contain significant stored energy and are poten tially hazardous Handling of gas bottles should be done only by qualified trained personnel 2 For smoothest operation used gas bottles should be replaced before their internal pressure drops below the desired regulator output pressure 3 Two possible cases exist in which a gas bottle needs to be replaced only one empty gas bottle on a system or both bottles empty on a gas system 4 For case 1 the sequence of steps is as follows a Check in the Hall A Gas Shed If all bottles have sufficient pressure each of the Matheson 8590 controllers will have one green RUN LED lit and one yellow READY LED lit A red EMPTY LED lit indicates a bottle with low pressure the corresponding bottle needs to be replaced If a red EMPTY LED is lit the central ALARM LED should also show red Nothing further needs to be done here go outside to the Gas Bottle Pad b Visually verify that the corresponding pressure gauge on the flex line is showing a low pressure A low pressure is not necessarily zero Close the bottle valve for the empty bottle c Disconnect the empty bottle from the high pressure flex line The in line check valves will prevent gas escaping from the manifold Replace
59. for Nitrogen The system controlling them is field programmed to compensate for different gasses Flow channel 1 currently assigned for CO has a mass flow controller calibrated to deliver a maximum of 100 sccm standard cubic centimeters per minute 74 sccm Flow channels 2 and 3 have controllers with a full scale range of 1000 sccm With the calibration factors taken into account the maximum flows are 500 sccm Ethane channel 2 and 1450 sccm Argon channel 3 Manual valves MV 201 amp 221 etc are provided which allow one to bypass the mass flow controllers and use a needle valve rotameter set MV 211 212 213 if desired The needle valve must be closed during normal operation using the mass flow controllers The mass flow valves are controlled by a Dynamass Flow Control System Vacuum General Inc model DM 2401 This unit is outfitted with four flow control channels two model FM 8 two channel modules and could be upgraded to eight flow channels if desired Refer Figure5 32 for a diagram of this system Currently HAWGS has only three of the four channels instrumented The FM 8 receives a flow measurement from its associated flow controller adjusts it by the calibration factor for the gas being used and displays the result on the front panel If the measured flow differs from the desired flow as 195 CHAPTER 5 HRS DETECTORS I i i ii tf i M NA ped
60. identified The low voltage system The system is supplied by 220Vac and 110Vac There is a magneto thermic and differential switch at the very first entrance of the power supply All the lines at these voltages are kept inside the racks and the plugs satisfy the European CE rules for these voltages The supply for the single devices inside the racks is all at 5VCC 12VCC 24VCC except for the pump which needs 110VCC and for the Motor Drivers which need a special 80VCC voltage A custom power supply unit has been built for this pur pose and this unit is kept in the so called Power Supply Unit at the bottom of the left rack together with the other supply units The signal lines are low voltage lt 12VCC the digital lines 0 5V or 4 20mA loops the analog ones and kept separated from the supply lines by using different connectors and separated cables Optocouplers have been used for the microswitch line in isolated input lines have been used for the analog lines A potential hazard outside of the racks is the motor cables which must be touched only by AUTHORIZED PERSONNEL and with the power supply switched off An 80VCC 2A square wave duty cycle 0 5 current flows in these cables when motors are in stand by mode This current goes up to 7A square wave duty cycle 0 5 when motors are moving these high power lines are everywhere kept separated from the low voltage lines The pump power supply line is kept inside the racks and in a position t
61. in 2 TS mode PEDRUNE To do a pulser run for E arm in 1 TS mode PEDRUNH To do a pulser run for H arm in 1 TS mode A note about pedestal runs They have the exclusive purpose of obtaining pedestals used for pedestal suppression For details about what is done and hints for getting pedestals for ESPACE which does not want the PEDRUN result see home adev ped README Some Frequently Asked Questions about DAQ e Q Where is the data Use a command find_run 1745 to find where run 1745 has been written on disk and MSS The data are first written to disk Files are automatically split with suffixes 0 1 2 etc Splitting occurs at 2 Gbytes to avoid problem of system file size limit Files are archived automatically to tape in the MSS tape silo Two tape copies are made Data are purged from disk automatically Users should never attempt to copy move or erase data e Q How to adjust prescale factors Edit the file home adev prescale prescale dat One common problem is putting typographical errors here which then leads to no triggers getting accepted e Q What is the deadtime The deadtime is displayed in the datamon window which normally is running next to the runcontrol window but if this window is not up type datamon to bring it up This window also shows the full path name of the file being written by CODA for the present run CHAPTER 7 DATA ACQUISITION AND TRIGGER 219 e Why is the deadtime so high
62. in general not achieved for from 15 to 30 minutes after reaching the nominal desired field This settling time depends on the magnet Hadron is slower than Electron and the magnitude of the field change small changes settle faster than big changes Experimenters are advised to observe both the field reading and current reading on the magnet in question and verify that things are stable to their satisfaction before proceeding 4 2 2 Dipole Field Monitoring Electron Arm see special instructions for running the Hadron Dipole in field regulation mode Basic Setup Each spectrometer dipole magnet is equipped with a Metrolab PT 4025 NMR Tes lameter several field probes and multiplexers to allow switching between the probes Details of the operation and theory of operation for the Teslameter can be found in its user manual a copy of which is available in the the counting house The basic layout is shown in Figure 4 7 The Probes Group 0 in the controls are located in two groups of three one CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 119 Coil Pack Coil Pack 3 coils 3 coils Variable P S 10 VDC Max Control Signal Figure 4 8 Gradient Compensating Circuit Table 4 4 Dipole NMR probe field ranges Probe Type Field Range T 3 0 17 0 52 4 0 35 1 05 5 0 70 2 10 group on the low field side of the gap and the other on the high field side of the gap The groups of three
63. machine and follow the instructions of the program accept the proposed mirror calibration angle and ask for an average of all your measurements If only one bench was measured encoder change BSY closed use for the other bench the most recent file available in gougnaud arc2 ARC angles analyze individual measurements and compare them to the above average The reproducibility of the reference angle measures several times on the same day should be lt 10 3 deg 17 urad 3 10 5 on the energy compare the new average to the previous one if nothing changed in the scanners and if only the downstream angle changed this can be interpreted as a motion of the arc the code gives the detail of the 3 angles upstream downstream and reference the files used today 01 07 99 are upstream 250699 dat 1 meas and down stream 250699 dat 2 meas They result in a reference angle of 34 32322 deg aver aged write the new reference angle in the arc scan source code include file arc incl plot f parameter Reference Angle Degree compile and test the arc scan code report in the e logbook about the changes and results file names CHAPTER 2 BEAMLINE 44 Example of upstream file upstream_250699 dat 1 meas UPSTREAM BENCH MEASUREMENT DE FE KK KKK KK 2K 2K KKK KK OK OK OK KK KK K K Used unit decimal degrees Enter data in this order e Autocollimation e Fiducial upstream of upstream bench 1 e Fiducial downstream
64. magnet are ready to go From here you can return to Autopilot Mode type in desired PO on control screen and wait or proceed as described below For Electron dipole type in desired current in I Set and the power supply will respond For Hadron dipole go to HRS HADRON DIPOLE NMR control panel Press RESET Press Reg Enable YES Press Search ON should already be on but it doesn t hurt to check Type desired field into Field Set field 5 Wait for field to reach the desired value In general it s a good idea to wait about 15 minutes after first reaching the desired field before taking data See Hadron Dipole Field Setting for more details and help with trouble shooting WN 4 2 6 Starting Q1 Power Supply Do this when a fault causes the power supply to shut off Wait for fault to clear watch He levels 1 Push RESET check all faults cleared 2 Select desired polarity 3 Push ON 4 Type in ISET yellow field or re enter PO in Autopilot Mode 4 2 7 Starting Q2 3 Power Supply Do this when a fault causes the power supply to shut off 1 Wait for cause of fault to clear e g low Helium level 2 Press RESET 3 Select polarity CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 127 4 Press ON 5 Type in ISET yellow field or re enter PO in Autopilot Mode CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 128 4 3 Collimators and Sieve Slits Both spectrometers have front end devices for cal
65. makes resonance hard to find Search for the resonance manually by adjusting the DAC in manual mode until you see the resonant signal It helps if you know what field you expect so you ll know where to look You find resonance manually Check probe polarity but still can t get a lock Try decreasing and increasing DAC number by 1 Optimize signal by adjusting compensating coils Can t find resonance manually Try a different probe Use readings from other probes to tell you where to look for the resonance with the probe that s giving you trouble Make sure compensating coils are energized properly Make sure magnet is on Hadron Dipole Field Setting Instructions Turn on power supply contact Mark Stevens John LeRose or Javier Gomez for assistance Turn on field regulation mode Type desired field value into FieldSet yellow field Wait for field to reach the desired value read from the blue field After reaching the desired field wait 15 minutes to assure stable field Pay attention to the current and field readings If the NMR is locked the NMR is locked if the field reading in the blue field has a positive number and is updating itself don t worry it will get there If the NMR is not locked negative but updating number in the blue field but the CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 125 current appears to be going in the right direction don t worry it will get there and th
66. mechanisms before removing the motor Be extremely careful when performing this procedure Now connect the new encoder to the cable and turn on the power supply to the system Check the value of the encoder position which readout is displayed at the bottom of the left rack this value must match with 27361 rotation or 17301 up down If values do not match then turn MANUALLY the encoder axis until the display value is at the desired one When done you can remount the encoder on top of the scattering chamber Switch off the system Put the stainless steel ring back on the encoder as it was mounted before Re check the encoder value and realign it if it is changed On top of the scattering chamber in the place where the encoder must be mounted you will see two pairs of cog wheels Turn gently the two wheels of the upper pair one CW the other CCW in order to charge the small spring among them then keeping this spring in charge position the encoder back on its place and fix it by putting back its screws Connect the cable The reference position must be detected once when installing the target and once when checking the alignments of the reference points with the metric rulers on the top of the scattering chamber Here we use the reference position the waterfall target position and at zero degrees angle Changing the target block a new reference point must be detected One single encoder step error means an offset e
67. monitor s output signal drifts significantly on a time scale of several minutes it cannot be used to continuously mon itor the beam current However this drift is measured during the calibration runs by taking a zero current reading and removed in calibrating the cavities The more stable cavities are then used to determine the beam current and charge for each run We also use the OLO2 Cavity Monitor and the Faraday Cup 2 at the Injector section to provide an absolute reference during calibration runs The two resonant rf cavity monitors on either side of the Unser Monitor are stainless steel cylindrical high Q 3000 waveguides which are tuned to the frequency of the beam 1 497 GHz resulting in voltage levels at their outputs which are proportional to the beam current Each of the rf output signals from the two cavities are split into two parts One part of the signal is converted to 10 kHz signals by the downconverters and fed into an RMS to DC converter board consisting of a 50 kHz bandpass filter to eliminate noise amplified and split to two sets of outputs which after further processing are recorded in the data stream These two paths to the data stream leading to the sampled and integrated data will now be described The other part of the split signal is downconverted to 1 MHz signals and represents the old system pre Jan 99 Only the HAPPEX collaboration presently uses these signals For the sampled or EPICS or Slow d
68. need to be interlocked for protection of human life and or equipment monitored for operational status and commanded to perform various operations so that the system as a whole is able to perform the desired measurement or function Most of these sub systems have an infrastructure role they are essential for the correct operation of the major system of which they are part but in themselves are irrelevant for the experimental physics data being acquired An example could be the cryogenics of one of the spectrometer magnets proper cryogenics filling of the magnets is absolutely essential for the magnets to operate but for a given experiment the relevant quantities are the spectrometer momentum and optics produced by the various active magnets and not the cryogenics levels of each magnet The task of monitoring and commanding the infrastructure of the various Hall A systems falls on a distributed computer system loosely referred to as slow controls or Hall A Controls HAC 6 0 3 Hall A Controls Overview The Hall A distributed control system is based on the Experimental Physics and Indus trial Control System EPICS 17 architecture The basic components of the system are CVS revision Id HacOps tex v 1 4 2003 06 06 17 19 22 gen Exp Authors J Gomez mailto gomez0jlab org http www aps anl gov asd controls epics EpicsDocumentation WWWPages EpicsDoc html 210 CHAPTER 6 SLOW CONTROLS 211 e Operator Interfaces OPI T
69. nut until the light guide cannot be moved in or out Replace the rear tubular housing by screwing it all the way into the coupling nut Insert the foam plastic light stop 02 between the collet nut and the light guide The mechanical assembly is now complete The Electronic Amplification Chain The arrangement of the resistor dynode chain is shown in Figure 5 10 The cathode is connected to the mu metal shield through a 10 CHAPTER 5 HRS DETECTORS 150 Figure 1 2 inch PMT Base Assembly Figure 5 9 The 2 PMT base used in 51 and 92 trigger scintillators CHAPTER 5 HRS DETECTORS 151 resistor in addition to the 1 resistor between the cathode and the negative HV The dynode chain incorporates an adjustable potentiometer 0 500 to allow a match between the PMT and the external load in order to eliminate after pulse ringing This potentiometer should be adjusted at first to 250 and then make fine adjustments as needed by observing the anode pulses on the oscilloscope for critical matching It is not advisable to do the adjustments with HV on Instead the process should be done with HV off remove the rear tubular housing adjust the potentiometer replace the rear housing and then turn the HV on again Iterate until the matching is accomplished In addition to the obvious safety concerns one does not want to remove the light sealing rear housing from an active PMT and induce a large light leak which could destroy the P
70. of all their work e The person with supervisory responsibility has approved the buddy After completion of the trial period undergraduates maybe approved for work in the halls under the standard guidelines Physics Division EH amp S personnel should be contacted to obtain the current policy for conducting tours in the experimental areas 1 3 4 The Hall A Safety Walk through In order to improve user awareness of the systems in the hall users are required to complete a self guided safety walk through the experimental area Information about CHAPTER 1 INTRODUCTION 15 RM WN RS 85 RM M Detector Stack Personnel Saf pee Shutoff 0850 Status Display PS f lower level Magnet Power ch MPS lower level RS 9 lower level t Power Switch MPS level ui d lower a Ac d LH Beem Line pem 1 m if 7 RS 93 if upper level 2 Hall A Safety Walkthrough Items Plan View Figure 1 1 Schematic of the Hall A showing the location of various safety system com ponents The abbreviations are Radiation Monitor RM Run Safe Box RS Fire Alarm Pull Box PB the walk through can be found on the web John Lerose is the JLab staff member responsible for the administration of the Hall A safety walk through Figure 1 1 shows the location of many of the safety related items in Hall A while figure 1 2 shows the location of all the circuit
71. of upstream bench 2 Horizontal Distance point A up fiducial 1996 00 mm 1 Horizontal Distance point A down fiducial 1975 00 mm 2 FKK KK KK KKK K KK KK e 25 06 99 Andrew Tim Mesur Nb 1 First measurement on 25 06 Encoder reading for upstream scanner of upstream bench 118406 1 Encoder reading for downstream scanner of upstream bench 118406 2 H1 H2 V1 V2 0 000100 179 995500 90 002100 270 003500 Autocoll 359 977700 179 973900 250 509900 109 498800 1 179 970000 359 967100 250 382500 109 619700 2 Example of downstream file downstream_210699 dat 2 meas DOWNSTREAM BENCH MEASUREMENT FORK Used unit decimal degrees Enter data in this order e Autocollimation e Fiducial upstream of down bench 3 e Fiducial downstream of down bench 4 Horizontal Distance point A up fiducial 1870 00 mm 3 Horizontal Distance point A down fiducial 1840 00 mm 4 2 KKK KK KKK KKK KK K K K K 21 06 99 Pascal Mesur Nb 1 CHAPTER 2 BEAMLINE First measurement on 21 06 Encoder reading for upstream scanner of downstream bench 118405 3 Encoder reading for downstream scanner of down bench 118408 4 Hl H2 V1 V2 0 000100 179 998050 90 001400 270 000000 Autocoll 6 100100 186 10110 110 667500 249 336900 3 6 176100 186 175700 249 129900 110 876300 4 F
72. on mechanics integral The probe is capable of a fast motion 1m s and it is hazardous to access or to introduce something inside the device under the altuglass covers or to dismount a cover It is also hazardous to manipulate the motor shaft see Shed access and safety above To do it safely the user must first turn off the motor power box The power box is located under the motor It has two external switches one controlling the logics and one controlling the power Logics switch TOP VIEW Power switch CHAPTER 2 BEAMLINE 59 It is important NOT to switch off the logics some data in memory will be lost but to switch off the motor power see the exact Power switch location above prior to any intervention on the mechanics The detailed procedure is the following turn OFF the power switch wait for lmin to empty its buffer capacitor you can work safely on the mechanics make sure that the path of the probe is free tools and the covers are in position turn the power switch back ON reboot the VME see Integral ioc reboot above The above procedure may be necessary if for some reason the probe went outside its allowed range limited by a pair of electric limit switches The probe range is limited by the following set of devices upstream energy damper for Zd in 40 14 mm upstream electric limit switch for Zd lt 7 5mm upstream optic limit switch for Zd 3 8mm operation range
73. orientation 3 4 4 The slow control system The slow control system consists of two Macintosh computers two VME crates an ADC a DAC and an electronic circuit It handles both the data acquisition and the control of the target system The layout is shown in Figure 3 7 Each Macintosh computer is hosted by one VME crate The two computers are interconnected via an optic ethernet line Fig 3 8 3 9 The first one also called MacA is in the hall This is the Master It controls the electronics directly with the slow control program H2OCEBAF97 written in Labview The second one called MacB CHAPTER 3 TARGETS 87 Le Hydraulic Subsystem from DAC to Figure 3 6 The Hydraulic system a schematic view CHAPTER 3 TARGETS 88 MacB Counting Figure 3 7 Schematic view of the whole system is a slave and is located in the counting house where it controls the target system through MacA Some of the controls and monitoring can also be done manually This provides an independent way of controlling the target in case the computer control fails The pump control and the display of the flowmeter and pump speed are duplicated in the counting house The reading of the optical encoder can also be seen in the counting house through a camera manual command of step motors is in the Hall 3 4 5 Authorized Personnel One of the following people can be contacted for any waterfall target problem Name Home Institut
74. per Turn 110 Motor Micro Step Per Step 200 Motor Step Per Turn 12500 a p Screw Pitch Micron 11 a Motor Polarity used for forward displacment begin forward 2 Time Stamp s 0 CHAPTER 2 BEAMLINE 39 4092 0 0 007 4092 0 0 017 4090 0 0 032 4090 0 0 129 lend backward 4 Time Stamp s 1305529 2 4 14 Details on trip handling Trips are frequent at 54A caused by scanners 3 and 4 and triggered by the Compton ion chamber or BLM even with chicane OFF They are invasive for the other halls If a trip occurs write in the e logbook which scanner forward backward for this you have to monitor the beam current during the scan beam current arc tuning mode which diagnostic tripped ask MCC get a strip chart of this diagnostic MCC Contact the beamline coordinator Arun Saha or the hall leader Kees de Jager to allow MCC to mask the diagnostic But in any case start with unmasked diagnostics to have all safety systems responding If masking is impossible or not sufficient reduce the beam current down to 14A but the quality of the energy measurement will then be affected by the poor signal noise ratio If the trip occurred from scanner 3 or 4 during the preliminary test in achromatic mode leave this step and ask for dispersive mode In this mode due to the dispersion of the beam the luminosity will be reduced and hopefully the trip will not occur Nev ertheless the test in achromatic mode is useful t
75. procedures during Research Opera tions depend on the number of individuals who will be entering the hall and the length of time they are expected to be there A controlled access is used when a few individuals require entry for a short period of time If the hall must be open for an extended period and many people will enter then you should use the restricted access procedure instead of the controlled access procedure Normally when requesting a controlled access the CHAPTER 1 INTRODUCTION 13 hall will be in either the Beam Permit or RF Permit State for example if the beam has been on or it could be shortly If the hall is not already in the Controlled Access state when you wish to access it you must request a change to that state from the Machine Control Center at extension 7050 and indicate that you intend to make a Controlled Ac cess The MCC will then send an Assigned Radiation Monitor to survey the hall Before anyone enters the hall the ARM will carry out a radiation survey and post radiation areas Subsequent entry by individuals during the same Controlled Access period does not require an ARM survey 1 3 1 Controlled Access Procedure To make a controlled access when the hall is in the controlled access state first contact the MCC The MCC will unlock the first gate at the entrance to the hall Once inside the MCC will release the master key Remove the master key and insert it into the right most slot of the row of keys below i
76. quasi regular intervals typically every two to five seconds For the integrated or VTOF or Fast data the other amplifier output is sent to an RMS to DC converter which produces an analog DC voltage level This level drives a Voltage To Frequency VTOF converter whose output frequency is proportional to the input DC voltage level These signals are then fed to Fastbus scalers and are finally injected into the data stream along with the other scaler information These scalers simply accumulate during the run resulting in a number which is proportional to the time integrated voltage level and therefore more accurately represents the true integral of the current and hence the total beam charge The regular RMS to DC output is linear for currents from about 5 pA to somewhere well above 200 A Since it is non linear at the lower currents we have introduced a set of amplifiers with differing gains x3 and x10 allowing the non linear region to be extended to lower currents at the expense of saturation at the very high currents Hence there are 3 signals coming from each BCM Upx1 Upx3 Upx10 Dnx1 Dnx3 Dnx10 All 6 signals are fed to scaler inputs of each spectrometer E arm and H arm Hence we have a redundancy of 12 scaler outputs for determining the charge during a run During calibration runs we calibrate each of these scaler outputs 2 3 2 Authorized Personnel All Hall A members are authorized to take BCM calibration data using the Standard
77. rear chamber cards use a 1 5 kQ resistor external to the board to limit current drawn in case of a short on the board Board threshold circuitry also has a 1 5 kQ to ground which with the external 1 5 kQ makes a voltage divider Therefore the rear threshold supplies are typically set to a voltage which is a factor of two larger than the front threshold supplies to give the same threshold voltage at the readout board Initial tests indicate that at least a 1 5 V threshold must be applied to the cards to prevent oscillations this level will stop oscillations that arise when the voltage applied is reduced to about 1 0 V In practice it has been found that the front chambers should be operated at 4 V and the rear at 7 V Efficiency studies show that the chamber threshold could be raised by 50 with minor loss in efficiency The HP supplies are also mounted in the hadron arm detector stack on an aluminum panel located beneath the two upper high current supplies Each straw wire contains a 25um Au plated tungsten rhenium wire The num ber of wires per plane varies from 176 to 272 Wires are multiplexed 8 wires into one electronics channel leading to a required 636 TDC channels In practice a few extra channels are used so that each 34 wire 16 differential signal channels plus one ground pair twisted pair cable contains only signals from one of the four chambers LeCroy 1877 multihit FASTBUS TDCs are used to measure the leading edge time and width of
78. small amount the A V angle then the A V coincidence between both crosses must be destroyed If it is not the case you are focusing on one of the two wrong patterns Then change the main focusing towards infinity counter clockwise to get another patern fine adjust the autocollimation power potentiometer to get the best vertical line of the autocollimation cross fine adjust A and V angles record their values in the Shed logbook change both angles by 180 000 deg WITHOUT CHANGING THE MAIN FOCUS ING and redo the previous step close the light tube turn OFF the autocollimation power switch on the battery Note the above mea surement is easy from upstream more tricky from downstream long distance autocolli mation New operators should start with the upstream measurement measure the scanner 2 3 the one which is on the autocollimation side remove the scanner cover unplug the connexion of the encoder to the VME plug the control box on the fiducial lamp and on the encoder record the encoder reading in the logbook It should be 118407 2 adjust the main focusing on the fiducial wire adjust the V angle to the middle of the aperture across which the wire appears fine adjust the A angle record A and V values in the Shed logbook change both angles by 180 000 deg WITHOUT CHANGING THE MAIN FOCUS ING and redo the previous step record the encoder reading in the logbook It should give the previous reading 1 encoder
79. solenoid valve is low and the solenoid valve is opened with full inlet pressure To reset the Excess Flow Valves refer to the section Resetting a closed Excess Flow Valve 5 8 6 System Operation Pre Startup Checklist Before initial use with a flammable gas or after a significant down time the following checks should be made to insure the safety and integrity of the HAWGS 1 Leak Check the entire gas system using a safe gas such as Argon or Nitrogen 2 Calibrate over pressure relief valves RV121 122 123 should release at 55 65 psig RV271 must release at 20 25 psig 3 Check calibration of Excess Flow valves should close at 4 5 slpm 4 Check proper operation of each interlock circuit and that interlock system shuts off gas supply 5 Measure the detectors leak rates and verify that each is below 7 slph or current administrative limit note that current physical limit is 500 sccm Ethane and 1450 sccm Argon based on flow controller full scales for and correction factors for Ethane and Argon 6 Verify that flammable gas leak sensors are appropriately calibrated Startup Procedure 1 Close gas shed outlet valves MV 302 A B C to isolate the mixing delivery system from the spectrometer detectors 2 Activate the Kill Gas crash button Interlock panel should alarm Silence the alarm by pressing Alarm Silence Reset the Crash Button by pulling outward If any fault conditions red LED other than Low Pressure a
80. temperature will presumably not undergo worrisome pressure changes Each target contains four quality temperature measurements two Cernox resistors and two hydrogen vapor pressure thermometers The primary temperature regulation is done with a dedicated temperature controller an Oxford ITC 502 which slaves a heater the low power heater to the temperature read by one of the Cernox resistors This is a three parameter control loop Proportional Integral and Differential Control or PID In addition the return temperature of the target systems coolant gas is used to regulate the supply of coolant from ESR Finally the heat load from the beam will be compensated in the active target loop by use of the high power heater This is not a true regulation but rather a one for one replacement of the beam load should the beam disappear for whatever reason The beam load is calculated from the target length the beam current as read from a current monitor and the target material Excursions of the target temperature outside acceptable limits will cause the control system to take action Finally the redundancy of temperature measurements can be used by the control system to pick up the failure of a sensor or its readout channel A more complete discussion of target temperature regulation is available in Reference 6 CHAPTER 3 TARGETS 79 Target Freezing Solid hydrogen is more dense than the liquid phase so freezing does not endanger the mechan
81. the Hall A superconducting magnets This is a 3 5 in diameter copper pipe which is filled with nitrogen gas at atmospheric pressure Thus any vented target gas is placed in an inert environment until it is released outside of Hall A Each gas tank has one relief valve and one rupture disk CRV43 and CRD44 for hydrogen and CRV72 and CRD143 for deuterium In addition to the reliefs on the gas handling system described above the scattering chamber itself has a four in one PSIG relief VRV01 This is the path that the hydrogen will take in the event of a cell failure The target pressure reliefs are summarized in Table 3 2 Scattering Chamber Vacuum Failure The scattering chamber will be leak checked before service but obviously the possibility of vacuum loss cannot be eliminated The most likely sources of vacuum failure are CHAPTER 3 TARGETS 75 Name Target Location Diameter in Pressure PSIG CSV28 0 125 40 CRV30 FRA 0 5 AO CRV82 RL 1 AO CRV43 TANK 1 55 CRD44 TANK 1 55 CSV57 D2 FRA 0 125 40 CRV59 D2 FRA 0 5 40 CRV64 D RL 1 AO CRV72 D TANK 1 55 CRD143 D TANK 1 55 CRV35 He RL 1 40 CRV01 SC 4 2 Table 3 2 A summary of the pressure relieving devices on the hydrogen deuterium targets and the scattering chamber FRA is an abbreviation for Fill Line Relief Assembly and RL is an abbreviation for Relief Line SC stands for Scattering
82. the desirable steady state operating condition 5 6 3 Carbon Doors Four of the five doors operate remotely the fifth needing further testing before it is certified reliable The doors use the EPICS control system to activate and read back the various components Each layer of carbon doors has one relay board Each board is identical in operation and there is one spare in the event one of them should fail The global purpose of the relay board is as follows 1 Turn on the 12V to power to rest of circuit board 2 Set the polarity on the 90V used to power the motors 3 Turn the 90V on CHAPTER 5 HRS DETECTORS 188 4 Cut off the 90V to a motor if the appropriate limit switch is hit 5 Read back the status of the limit switches The 12V used to power the circuit board runs through this relay and it is activated via an EPICS relay in VME crate 4 hallasc4 Relay 1 turns on the 90V and it too is activated by an EPICS relay in VME crate 4 Relay 2 switches the polarity of the 90V being fed to the driving motors When activated it reverses the polarity to the motors and it is controlled by a relay in VME crate 4 Relays 3 and 5 are activated by the inner limit switches of the carbon doors When these switches are depressed the relay activates and the 90V is cut off Relays 4 and 6 are activated by the outer limit switches of the carbon doors and like relays 3 and 5 cut off the 90V when activated Relays 4 and 6 activate when opene
83. the maximum pressure in the chamber stay near one atmosphere it is necessary to vent one half of the target mass in approximately one half of the total expansion time Therefore the relief valve for the scattering chamber should be capable of venting about three grams per second at a low pressure difference say two PSIG If one considers the case where all three targets fail at once the vent must be capable of handling three times that amount A four in diameter relief valve placed near the top of the scattering chamber should be capable of handling this rate A rise in the chamber vacuum will stop the beam FSD and cause the gate valves on either side of the scattering chamber to close In the unlikely event that a line which carries helium coolant were to rupture the four in chamber relief valve is capable of handling the full coolant flow rate CHAPTER 3 TARGETS 78 Inner Diameter Length Kerf 0 44in tube 108 4 64 31 5 0 88 in tube 10 2 32 0 98 Quantity Value Minor Losses 7 4 40 Average Diameter 0 71 in xmax 0 890 Wsonic 0 065 Ibs s m 0 323 x 0 748 P2 14 7 PSIA 58 3 PSIA 43 6 PSIG Table 3 5 Tubing sizes and other information needed to analyze relief line response The mass flow rate was 0 03 Ibs s 3 2 8 Temperature Regulation This is really more an issue of target stability than one of safety However a target with a carefully regulated
84. the proper location of the insulating plastic sleeve may result in electrical shock The Electronic Amplification Chain The dynode amplification chain is mounted on a PC board as is the case of the 2 base A schematic diagram of the resistor chain is shown in Figure 5 12 As in the case of the 2 base it incorporates an adjustable potentiometer 0 500 and the nominal critical matching value is 90 Q It has in addition a 51 resistor in series with the 14th dynode to further improve the shape of the anode pulse A safe HV to start with is 1 8 kV it provides the best timing resolution with adequate pulse height for electrons during beam testing 5 3 8 Safety Assessment WARNING The bases are high voltage devices and should only be handled by competent people who can exercise common sense The maximum voltage for both the PMTs and dynode chain is 3 kV In actual use however there should be no need to exceed the 1 8 2 1 kV operating parameters since both PMTs and dynode chain have high gain Nevertheless the bases are high voltage CHAPTER 5 HRS DETECTORS 154 BURLE 8854 PHOTOMULTIPLIER TUBE DYNODE CHAIN K G di de 93 94 05 4 97 499 di4 Sia 01 Hf 0t i OSuF Si 10M 1 100k 100k 100k 100k 100k 100k 100k 00k 100k 100k 100k 100k 100k 100k 100k 100k 100k 10k A Signal netal HV DYNODE CHAIN shield 7 M resistors 6 Watt Metal Fim Alt Capacitors gt 20 UNIVERSITY
85. the same as the one for the CEBAF machine and beamline The Hall A staff liaison with the MCC are Primary Contact A Saha x7605 Secondary Contact J P Chen x7413 The Liaison between Accelerator Division and Physics Division is Liaison H Areti x7187 2 1 8 Additional Safety Information Additional safety information is available in the following documents EH amp S Manual PSS Description Document contact K Mahoney for a copy Accelerator Operations Directive contact T Oren for a copy OSP CEBAF Beam Operations updated annually CHAPTER 2 BEAMLINE 21 2 1 4 Machine Beamline protection system The MPS system is composed of the fast shutdown system FSD beam loss monitor BLM and gun control system The FSD system is a network of permissive signals which terminate at the electron gun and chopper 1 The permissive to the gun and chopper 1 may be inhibited by any device connected to an FSD mode Devices connected to the FSD system include vac uum valves RF systems Beam loss systems beam current monitors beam dumps and particular to Hall A the target motion mechanism and the raster value and derivative The gun control system includes software program which monitors beam operating conditions and the state of the FSD and BLM systems the program will warn the operators if a potential for beam damage exists Potential for damage exists when running high average current beam when FSD nodes are masked and when the beam po
86. the shower counter log book located in the Hall A counting house for the latest values of the high voltage e Never disconnect or connect all the high voltage to the bases with the high voltage power turned on Doing so will damage the bases the zener diodes are destroyed e Never service the lead glass with the high voltage on The high voltage poses a safety hazard e Never drop anything onto the bases and tubes they are extremely fragile They should not be used as support or to hold any weight Also do not drop the lead glass blocks They will be damaged or destroyed e When ramping the HV keep an eye on the current drawn by the individual bases A light leak in the wrapping will produce a large current gt 1uA at low voltages 1 kV If the tubes draw an excess amount of current turn them off and check for leaks in the wrapping 5 4 4 Safety Assessment The following potential hazards have been clearly identified The High Voltage System The LeCroy 1443 HV crate equipped with LeCroy 1461N negative high voltage cards supplies provides up to 3 3 kV of low current power Red HV RG 59 U cable good to 5 kV with standard SHV connectors is used to connect the power supply to the photomultiplier tube voltage divider bases A given base on the TA draws typically 500 600 uA of current with the high voltage on at between 1400 and 1500 V The PS bases typically draw 900 A with the high voltage on at between 1100 and 1200 V The Lead Gla
87. the system is monitored and alarm states are generated if a transducer returns a value that is outside user defined limits High pressures will cause the small orifice solenoid valve to open and cause an FSD Temperature Monitoring The temperature of the target is read from resistors and vapor pressure bulbs and alarm states are activated when any temperature sensor returns a value outside the user defined limits High temperatures will cause an FSD to occur Temperature Regulation The control system allows the target temperature to be regulated In the default operating scenario this regulation is performed by a stand alone temperature controller Solenoid Valve Control The gas systems have a number of solenoid valves that must be switched J T Valve Control The flow of coolant through the heat exchangers is controlled by a set of J T valves These valves control the coolant helium flow through the three loop heat exchangers and the precool heat exchanger Circulation Fan Monitoring and Control The fans which circulate the target fluid are monitored current voltage frequency The voltage supplied to the fans is adjustable and alarm states can be set on out of range frequency voltage or current values Vacuum Monitoring The scattering chamber vacuum is monitored by the control sys tem Unacceptable values will generate an FSD and close the upstream and down stream scattering chamber valves Target Lifter The target lifting mechanis
88. the target chamber is supplied by an Alcatell 880 5 Turbo pump backed by an Alcatell 21 cfm 2 stage vane pump The Turbo is mounted on the lower ring of the Target Chamber to one side so as not to interfere with the Target Chamber windows The same instrumentation is used here as on the spectrometer Powered valves instrumentation and pumps will be controlled and powered at the Vacuum System equipment rack located on the access Balcony Selective equipment will also be controllable from the Hall A counting house Magnet Vacuum System Vacuum for the magnet insulating vacuum is provided by the Cryo pumping effects of each individual magnet All controls for the Magnets are manual as we expect no problem after initial pump down The insulating vacuum for each magnet is self contained within the magnet Beam Line Vacuum System Vacuum for the entrance beam line is supplied by 65 2 6 Balzers turbo pumps the first of which is located on the E P chamber and the second located 3 m upstream of the target chamber Both turbos are equipped with a HPS 7 Series 275 mini Convectron gauge and a HPS series 421 Cold Cathode gauge located near the balcony Vacuum readouts and relay outputs for interlocks are supplied by HPS series 421 Cold Cathode gauges In addition to these there will also be Convectron gauges Most of this instrumentation will be located on the Turbo pump manifold Powered valves instrumentation and pumps will be controlled and powered
89. these are listed in Table 2 1 Each section has a roughing port and is pumped with an ion pump The pressure is about 1079 Torr There are several sections along the beamline where users interface their equipment Their individual systems are tested leak tight to lt 107 Atm CVS revision Id beam tex v 1 3 2003 06 06 15 19 02 gen Exp Authors A Saha mailto saha jlab org 17 CHAPTER 2 BEAMLINE 18 ENTRANCE TO HALL A ELECTRON 2 MINI DETECTOR RN WALL COMPTON E CALORIMETER GRAPHIC SCALE FEET COMPTON POLARIMETER Figure 2 1 Schematic of the Hall A beamline starting at the shield wall to end of alcove MOELLER RAST DETECTOR ER TARGET CHAMBER EP ENERGY MEASUREMEN MOELLER TARGET 0 5 10 20 nu GRAPHIC SCALE FEET Figure 2 2 Schematic of the Hall A beamline from the end of the alcove to the target chamber CHAPTER 2 BEAMLINE 19 DIFFUSER EXIT BEAM PIPE GRAPHIC SCALE FEET BEAMLIN Figure 2 3 Schematic of the Hall A beamline from the target chamber to the dump diffuser 2 The Beam Optics Channel
90. unit unplug the control box CHAPTER 2 BEAMLINE 43 plug the connexion of the encoder to the VME cover the scanner Note in case of scanner 2 a foil closing the apertures in the mirror support must de removed prior to the survey and reinstalled after measure the scanner 1 4 as for 2 3 re measure the autocollimation angle turn OFF the theodolite push simultaneously the and buttons release both breaks mount the handle dismount the theodolite dismount the battery and the autocollimation cable store the theodolite in its box store the theodolite box and the control box in the Shed charge the battery ies Note in case you have to change the battery during the measurement redo the complete measurement with the new battery A battery in good shape can provide 2h of work with autocollimation ON The survey of a bench will take between 1h and 1 2h If possible discharge the battery before charging it analyze the angle in the directory gougnaud arc2 ARC angles edit a plain ASCII file named up stream_ddmmyy dat or downstream ddmmyy dat depending on the bench where ddm stands for the date of the survey Use upstream 270798 dat or downstream 270798 dat as a model Units are encoder unit and decimal degrees If several measurements of the same quantity were done enter the average If the full measurement of a bench was done twice edit both sets of data as in the model run angle on a Sun
91. 0 Table 7 1 Terminal Service for DAQ Port Service Device Function 1 HACI halladaq1 E arm Trig Super TSO 2 HAC2 hallasfil E arm Fastbus ROC1 3 HACO9 halladaq4 H arm Trig Super TS1 4 HACII hallasfi2 H arm Fastbus ROC2 B HAC12 hallasfi3 H arm Fastbus ROC3 6 HAC5 LeCroy 1450 E arm HV control 7 HAC6 LeCroy 1450 E arm HV control 8 HAC13 LeCroy 1450 H arm HV control 7 1 4 Electronic Logbook and Beam Accounting Two tools are available for logging information by the shift workers 1 The Electronic Logbook halog and 2 The Hall Beam Time Accounting Table The electronic logbook is a web based repository of logbook data There are two ways to make entries One can use the halog GUI type halog and make your entry or one may use a script to insert a file Some data from EPICS and scalers among other things are inserted automatically into halog on each start of run and each end of run These data also get written into files with the run number in their name in home adev epics runfiles Data appear on the web at a certain URL It is recommended that one software expert from the experiment be assigned to modify the logging scripts as he or she sees fit The Hall Beam Time Accounting Table is the mechanism to summarize and record how the beam time in a shift was spent These data are logged automatically in a database and are e mailed to various people like the run coordinat
92. 0 GeV region 11 The Hall A electromagnetic shower counter is meant to offer rejection ratios better than 100 1 12 The limitation in using a shower counter comes from separating the tails of the distributions and is therefore dependent on energy resolution At higher energy the relative resolution of a shower counter improves leading to better separation between distributions Conversely other techniques perform worse at higher energy The TOF separation for a given path length decreases and above 4 GeV c pions can trigger a threshold Cerenkov counter operated at standard temperature and pressure STP 11 The threshold for a Cerenkov counter at STP is 34 1 meaning that for an electron the threshold is just over 17 MeV while for a pion the threshold is just over 4 GeV c momentum A Cerenkov counter is routinely capable of pion rejection of the order of 1000 1 at CEBAF energies 11 A combination of successive Cerenkov counters might achieve higher rejection ratios However this only works if the backgrounds in the two devices are uncorrelated A knock on electron which triggers the first Cerenkov counter and travels forward through both detectors will also trigger the second Independent PID provided by a measurement of the particle energy in a shower counter offers a solution to this problem of correlated backgrounds Used in conjunction with a threshold Cerenkov counter the combination can achieve rejection ratios of 5 x
93. 0 Starting Q1 Power Supply gt ea 2 m denga iwa cai 126 42T Sterne Q2 3 Power Supply s ierra perrie eee Pee 126 43 Collimators and 128 LOI Authorized Personnel c xoc xd gee BS 128 482 Safety Assessmenb 128 4218 Procedur 2 2 2229 ran ee amo RUE RR 131 4 4 Spectrometer Alignment 132 141 Personnel Responsible 132 5 HRS Detectors 133 Ql INPUNE be be ioi e Eq 3d xy ons ER 133 5 1 1 Geometry of the Spectrometer Detector Packages 134 pe Vertical Dritt s cs os soos hono awe Y ADS 135 Dal se eu ecu Pur xr wok SEDER GREC 135 5 2 2 Operating PROGBOUE 2 ku koe oe Ro Roy Ro 138 5 2 2 Handling Consderabllolig amp ses ss lt 2 edo wo dee aos 142 Det Other Documentation td innii 142 5 2 5 Safety Assessment 143 5 2 6 Responsible Personnel 143 meo Trigger Scintilator 2o x RU ORO e RE Rw Ux xx ex 144 Ql auos xo Rob ORO hok 4o d EE dodo Pod RIO RE 144 5 9 2 regime and time resolution o o gn 145 5 3 3 PMT operation monitoring cs csr seseg agaaa das 145 5 3 4 PMT replacement 224 255458258555 5 145 5 3 5 2 PMT Bases for 51 and 82 Trigger Counters 145 5 35 6 Handling Considerations se 55 4 om Rs 149 5 4 7
94. 02 6611 Mil nam OL UD 4 11 wy 2 wj sos 9 9s 0 oss ossz zo 1201 1 01 11 wy 2 99 vos 9s 95 ossz 2 esol 01 141 y 2 94 6 5 sg 0 552 ossz L ooi 0021 z 24S 01 1 w 2 94 9 gs 0 0s ossz 1 os oss s 949 021 8 2 so 904 sj 96 0 oss ossz z 6961 t SUD ozte C 4 i 4 2 ver 94 ss 0 ossz ossz z 0022 ooee z ozie C 4 i wy 2 g eos 9s 0 905 0652 z ooee z 4S ozie C 4 Li 4 2 534 eos 99 0 905 ossz L 22 1022 z mmmm 25 01 141 wy 2 sd sep 5 sg 0 osse ogsz L 90 ooz z meme 19 015 141 wy 2 94 9 54 ss 0 05 ossz z 0021 z meme 04D 185242 z uuna 198 201 2 0 1 5 N dWvu 13504 dndWyg snivis 145 1 YENI gno v3 AlS ASV3W 39v9N3 13NNvH2 vn 0L 0 135 202 S A 0002 06 13S 0992 lt 01 10 01 lt 0862 135 HH121 S A 0002 lt 08 13S j AO0 0 13S ZAA 000 0 10 A 000 0 A 19S sabuey Figure 5 7 HV screen for a single card CHAPTER 5 HRS DETECTORS 148 200 99 04 03 20 32 Lo qm 02 600 re bsec aec iani iun c e 7o 5 05 400 be S 200 0 200 400 2 4 6 HS1L mW RM ERE X 1000 NE E M ME Ee 800 A MM CEU MN 600 cS
95. 1 3 2003 06 06 15 19 03 gen Exp 12 Authors mailto 0jlab org CHAPTER 2 BEAMLINE 60 Target Chamber Spectrometer Coupling The aluminum middle ring will support a flange on each side for each high resolution spectrometer Four flanges will be available Two flanges will contain a 6 in window opening which will be covered with a thin foil e g 10 mil aluminum These two flanges will be used for experiments utilizing extended targets that do not require optimum momentum resolution The other two flanges will have two fixed ports with a 8 in x 6 in opening which will be mainly used for calibration of the spectrometers Fixed ports are centered at 16 11 and 45 for one flange and at 16 11 and 90 for the second flange For a point beam on target a vertical opening in the walls of the chamber of height 57 15 cm x 0 065 x 2 7 43 cm is required so that the scattered beam is within full acceptance of the spectrometer If the beam is rastered on target 0 5 cm in the vertical direction then the opening in the outer side of the chamber must be at least 8 5 cm for full acceptance From consideration of the angular range of the spectrometers in the standard tune the scattered beam acceptance envelope the effects of an extended gas target on accep tance and the effects of a rastered beam 5 mm on acceptance the target chamber requires a window of at least 8 5 cm high in the aluminum ring extending from 6 33 2 48 in from th
96. 1 in FLOW MODE set up flow program C to provide the desired mixture at about 1096 higher total flow than the detectors are expected to consume Return the DM 2401 to gt NO MODE Select Auto pressure control using toggle switch on panel in rear of mixing station behind flow controller Actuate the Low Pressure Override on interlock panel Main Relay light should become green Set Excess Flow Valves and Manual valves at regulators to full OPEN wait about ten 10 seconds for supply lines to come up to pressure then set all three Excess Flow Valves to AUTO SHUTOFF Low Pressure interlock circuit should go to green during this step Verify proper operation of flow mix control system and outlet pressure regulation by observing flow rates on the mixer control and outlet pressure at the supply rack pressure gauges 301B 301C If the alcohol bubbler loop is valved on it may take several minutes for its volume to fill with gas and come up to pressure Be CHAPTER 5 HRS DETECTORS 204 15 16 17 patient When the pressure indicated on gauges PG301 B C reaches about 15 psig the DM2401 system should cycle to flow program D To bleed down the outlet pressure in order to cause the pressure loop to cycle you may crack valve MV 299 located in the rear of the mixer rack When the pressure drops back to about 13 psig the control system should switch back to program C Re close valve MV 299 when tests are complete
97. 14903 W m 10526 W m 11235 W m ty 26 78 s 28 29 s 23 89 s 26 3 s w 0 0038 kg s 0 0045 kg s 0 0056 kg s 0 014 kg s 0 03 Ibs s Table 3 4 The geometric quantities needed for and the results of calculations of the mass evolution rate after a catastrophic vacuum failure The calculation of the pressure drop includes all the plumbing up to the large relief valve The calculation assumes that all the mass flow is carried out the relief side of the target gas handling system no flow out of the fill line reliefs The friction factor for each diameter was taken from a Moody plot A typical value was f 0 017 The effective K values Ke f were adjusted to the average tube inner diameter which was taken to be 0 71 in The final Keff value was 40 The minor losses are from bends expansions and contractions in piping The final result shows the cells subjected to 58 PSIA during the boil off which is comparable to the 75 PSIA pressure that the assembled cell blocks were tested at and is significantly below the tested pressure of the cell components The scattering chamber has a volume of about 2 100 with perhaps an additional 200 of volume in the bellows and the cryo can If one target cell were to rupture and the chamber were unrelieved the chamber pressure would rise to about 2 Atm It takes approximately 150 seconds to bring 5 l of 22 K hydrogen to room temperature by conductive heat transfer with the scattering chamber walls In order that
98. 300 ns TDC 1875 START 4518 100 4518 300 VXI 4518 300 to SCALERS ABC3 h 1 13 delay FO delay FO ATES delay FO to SCALERS ABC4 4 Level 1 Hadron ACCEPT Arm T3 22 10 to SCALERS ABC5 h H2 14 NIM MLU 4518 300 16 4 Level 1 oes ies m 0 gt 1 delay FO ACCEPT NIM A Level 1 EXT NIM 11 NIM 11 H2 10 4 TS Trigger accept gt LEVEL Super a TRANS TS to SCALER Accumulated NIM 12 VXI VXI NIM T2 delay is 136 ns up to 6 Fixe this point 4518 100 4518 300 Triggers Triggers TS1 TIS TS T 5 plus hela delay FO Clock TS8 Y 2 9 2 9 Fixed Delay E1 gt 1 NIM Logic DISCR Module NIM Phillips Phillips actum get nm transit from transit from ND HRS2 to HRS1 HRS2 to HRS1 H1 22 23 H1 22 23 Hadron Arm 237 ns 340 ns TD Electronics Belden 9907 ES TC RG 213 E ARM Trigger cable T3 transit from HRS1 to HRS2 transit from HRS2 to HRS1 Electron Arm 237 ns 237 ns Electronics Belden 9907 Belden 9907 cable T1 cable T2 Phillips Phillips ECL gt NIM ECL gt NIM E2 6 7 E2 18 19 STOP to TDC Electron Arm TDC 1875 START Accumulated Tl delay is ADC 1881 GATE Phillips 116 ns up to TDC 1877 STOP this point ECL gt NIM Level 1 E2 6 7 ACCEPT SCINT ADC GATE START for TDC Delayed S2R from E Retiming Delay Det Monitor gt 15 Phillips Phillips T1 MLU out 2 1 gt 1 ECL gt N
99. 44 o9 4e9 oko 208 CONTENTS 6 Slow Controls 601 Hall A Slow Controls 2 s s s ca zx gx ee 002 Tutrod ction 225255 mox Se eae ee ee we 6 0 3 Hall A Controls Overview 60 4 Personnel Responsible lt o soes ke EE 7 Data Acquisition and Trigger 7 1 Spectrometer Data Acquisition 7 1 1 General Computer Information 7 1 2 Beginning of Experiment Checkout AEN 0 CODA TM Some Frequently Asked Questions about DAQ Cold Start 2 7 1 4 Electronic Logbook and Beam Accounting 7 1 5 Terminal Servers 7 2 Trigger Hardware and Software ta Online Analysis Data Checks coso cs 55529 xe Rx x Scaler Display and Scaler Events Tok Analysis sing ESPACE lt a o soos deem 9 pade Ow fone Dataspy and Diet e edis ea 6 3 3 xx x 3 55 5 9 Hall Checklist A 1 Pre Beam and Cryo Target Checklist A 2 Post Beam Checklist for Maintenance Post Beam Checklist for an Extended Time List of Tables 2 1 2 2 2 3 2 4 2 5 2 6 3 1 3 3 3 4 3 5 3 6 4 4 2 4 3 4 4 4 5 5 1 5 2 5 3 5 4 fad Beamline Hall A Beamline Elements 25 Beamline Optics Requirements T
100. 45 for Ethane multiply by 0 5 for multiply by 0 74 Waste Gas Collection and Venting Gas coming from the chamber exhaust bubblers is collected in a manifold and routed back to the gas shed through a large 1 inch OD polyethylene tube There are separate manifolds and exhaust lines for the VDC and FPP systems Back pressure in the exhaust manifolds is monitored by PHOTOHELIC A pressure switches If more than about 1 inch H2O backpressure develops an exhaust manifold the gas supply interlock system is tripped turning off the gas supply at the solenoid valves outside the gas shed The purpose of this particular interlock is to protect the detector windows from overpressure 5 8 4 Autherized Personnel The following personnel are responsible for problems concerning the gas system Howard Fenker x7431 Jack Segal x7242 5 8 5 Safety and Device Protection There are a number of monitor points which provide signals to the gas interlock panel and which can cause the supply of gas to be interrupted The primary purpose of this system is to facilitate the safe handling of a flammable gas A secondary but equally important function is protection of the detector hardware Finally this system serves to help insure the integrity of the data collected by Hall A experiments by alerting the experimenters on shift if a condition arises which might affect the detector gas quality The conditions monitored are 1 flammable gas leak detection
101. 46 foil 3 0 436 2 179 foil 4 0 603 3 013 foil 5 0 769 3 847 foil 6 0 936 4 681 in limit 0 966 4 831 The only operational control consists of moving the ladder in and out Radiator position is determined by the ratio of the readback voltage from a linear encoder to the voltage applied to it Table 2 gives the radiator position as a function of this ratio The foil thicknesses are set so that the thickness in percent of a radiation length equals the foil number except that no foils are mounted in position 1 Software controls of the ladder position are under development radiator position is changed by calling MCC and requesting that the radiator be set to some foil position or to the out limit The position may be changed with beam on A manual control backup system also exists Both software and manual backup systems control an Oregon Micro Systems MH10DX step motor driver which drives a Slo Syn M063 LS09 stepper motor The MH10 driver power supplies and other control circuitry are in a custom built box located in the hall in rack 1H75B10 The linear encoder voltage ADC is in slot 5 of the CAMAC crate in rack 1H75B02 radiator inputs use channels 15 and 16 and are connected through a patch panel to block 30 in rack 1H75B08 When the radiator is not being used the system should be set to the out limit CHAPTER 2 BEAMLINE 64 position so that it is clear of the beam Power to the control box in the hall may be turned off with a
102. 5 PMT Bases for 52 Counters 152 5 3 8 Safety Assessment 153 5 3 9 Responsible Personnel 155 5 4 Lead Glass Shower 156 VEIEN e nd ieu Moe AATE HR E AR Ta See d OR OE EIE 156 5 52 Operating Procedures 222 52 222 Ba oe Hu d 903 dona 157 542 Handling Considerations x s a bosom X eo Ok X are ox cy 157 5414 Safety Assess 24444 o oko ok OR 9 Rok BERS 162 CONTENTS 5 5 9 5 6 5 7 5 8 bola Authorized Personnel s 0 0 6 RR ox RE RED ROLE 162 5 4 6 Software Algorithms 2 44 lt 64 x o o 163 Aerogel 165 mol TOUSPUMS auos oce Roe wok dew 4m 5 8 123 RH 165 5 0 2 Responsible Personnel eces 2 43 169 0 0 0 Safety ASSESSMENT cu so oo E o e o RR ER SRR 169 Dod Operating Procedure i soa e eae 555 DS Le yoke os 175 5 5 0 Handling Considerations css 59 44024464888 Roe GE 175 The Focal Plane Polammeter 2 93 tdr 9k 24 9o x S 177 caca dur ERS d AGRE SEEKERS 177 5 0 2 Protege lt lt so 4 lt 9 toer re rie 642 igi 182 ag Carbon DONE s Lk PRS EE o4 de EE DRE ZEEE 187 5 04 Handlme Considerations oca x doe we SS eR ee 188 5 6 5 Safety Assessment 1 s 190 5 6 6 Responsible Personnel 190 The Hall Gas System
103. 80 640 865 1083 268 82 3141 2220 640 877 1099 274 Analyzer 3495 2190 680 916 1147 296 SC3 3907 2540 1000 1099 1343 457 SC4 4264 3170 1500 1382 1645 705 S3 4477 3600 1550 1437 1704 752 Table 5 2 Locations of the detectors on Hadron Arm in mm 5 2 Vertical Drift Chambers 5 2 1 Overview The High Resolution Spectrometer Vertical Drift Chambers provide a precise 125 measurement of the position and angle of incidence of both recoil electrons in the HRSe and knockout protons in the HRSh at the respective spectrometer focal planes This information may be combined with the knowledge of the spectrometer optics to determine the position and angle of the particles in the target Each Hall A spectrometer boasts its own VDC detector package These packages are located on permanent rails mounted on the spectrometer decks in the shielding huts above the outrun windows but beneath the space frames The packages consist of two VDCs and are identical in all aspects The VDCs have been constructed without guard wires Each VDC is composed of two wire planes in a standard UV configuration the wires of each plane are oriented at 90 to one another and each plane is oriented at 45 with respect to the nominal particle trajectories see Figures 5 1 5 2 Operation of the VDCs requires the application of both High Voltage HV across the chambers themselves and Low Voltage LV across the preamp disc cards whic
104. A GAS CERENKOV 82 7 Y 1 11 modular to TDC 840 ns B1 B10 1 11 fixed to ADC able dela patch 2 row 1 patch 2 row 2 ed to ADC able dela PROMPT TRIGGER T4 modular to TDC No SRAY but all other fixed Note both Cerenkov detectors are removed possible combinaations dels from the detector stack for the D e e d with one missing experiment This does not affect logic since both serve as vetoes to the logic SRAY S1 4413 200 4518 100 SRAY S2 DISCR DELAY FO I171331713 2 18 to SCALERS to SCALERS 1 13 4564 AEROGEL 4518 100 C A OR OR CERENKOV 17 30 to SCALERS These must be added to put AEROGEL 4413 200 4518 100 into logic 1 13 gt 1 19 prscr DELAY FO H2 20 H2 22 LeCroy Model Number modular to TDC FUNCTION fixed imes used blank if 1 fixed able dela to ADC patch 2 row 3 CAMAC CRATE SLOT CAMAC Module Notation Note The FPP is not included in TRIGGER LOGIC Note The modular delays are NIM LD1200 HALL A HADRON PROMPT TRIGGER DESIGN 11 13 97 Figure 7 2 Hadron Arm Trigger Circuit CHAPTER 7 DATA ACQUISITION AND TRIGGER 224 711 from H ARM RETIMING DELAY NIM DISCR RETIMING Upstream BCM V F NIM 10 NIM gt L1 T2 Downstream BCM V F Hadron Arm T4 hadron delay 2 FIM 300 0 ns variable delay TDC 1877 STOP FPP hadron delay 1 y delay 2 delay 1 300 ns AND TDC 1877 STOP VDC 0 300 ns variable delay delay hTOF
105. Bases for 51 and S2 Trigger Counters A schematic diagram of the 2 PMT Base is shown in Figure 5 9 The Base consists of three main components These are the front tubular housing 06 which encloses the PMT part of the scintillator counter s light guide 01 and the mu metal shield 10 146 CHAPTER 5 HRS DETECTORS 92 22 81 1001 6011 5401 6 2202 1012 Lyo ar S2 02 9901 8801 8011 6211 1202 1202 LOSZ bz 6l 6901 4011 6 01 2011 2002 1061 2682 1982 ita 8L 9601 8201 90L 6201 1802 61 16 2 4 lige 8901 1 41 2701 2611 2461 1981 182 62 02 60L 80L CULES 6l 1404 94d 0052 22 02 LLOL 201 80LL 1812 1022 9 10 2 Lea 8L 9801 4901 LILL 1801 002 L 02 1042 02 I OZSL Ezol ZO 5901 0461 2461 10 2 A 8L 1401 686 2901 8601 1402 1012 2088 Zev2 6L 6L 1801 0601 8PLL EASES 0002 10 2 0z 12 80L 288 0901 brol 1802 1002 04d je jo je je AOYUSIID AOYUTIID AOYUTIID JAMOYSIIY 12 ousaJg JAMOYSAlg Ja ousalg 431 rx Set jebolsay 8 1015 2 015 S 1015 1015 25 15 25 15 do uu Figure 5 6 EPICS HV HRSR summary screen 147 CHAPTER 5 HRS DETECTORS oze JE L z og tog 5 95 25552 ossz 1 o oozi 1 ozre 4 1 wy 2 99 eos oss ossz ols 09 00
106. C ask the computer center to restart pascall Second check if the 4 temperatures and the 3 currents are stable in agreement between them and if the beam energy computed from the current is realistic compared to what you know from MCC In not call Arun If the IOC is dead all displays on arc master adl are blank reboot the ioc see integral ioc reboot below Note the current field ratio is about 1000 1 98T and the energy field ratio is 12 03 GeV T The current used by MCC for the accelerator tuning is the set current The readback can be different from the set by 0 1A The local current can be different from the set by 5A For the temperatures see detail on temperatures below Third check if the NMR is locked If not see details on NMR lock below Forth check if the NMR reading is stable within 10 5 relative P S stability If not inquire about a recent or running setting change by the MCC If necessary call Arun Saha 2 4 23 Details on NMR lock check if the dipole current is above 22A The integral setup can t work for lower currents 22A 043T 517MeV due to the NMR probe limitation check if the probe is at a central position corresponding to Zd 1604mm It should be at this position if no special motion was ordered since the previous integral measure ment If not enter 1604 RETURN in the set Zd position input field wait for the end of the motion look at cursor and position readback labelled out and w
107. C17 49 411 Quad MQA1C17 49 100 1C18 BPM IPM1C18 48 650 Quad MQA1C18 48 300 CHAPTER 2 BEAMLINE 24 BC MBC1C18H 47 957 BC MBCICIS8V 47 761 French Scanner 8 47 381 Bench Scanner IHA1CISB 43 673 1C19 Quad MQAIC19 43 000 1C20 BPM IPM1C120 42 550 Quad MQA1C20 42 200 BC MBC1C20H 41 857 BC MBC1C20V 41 661 Ion Pump VIP1C20 41 450 COMPTON Polarimeter Region 41 000 25 500 Ion Pump VIP1C20A 34 500 Ion Pump VIP1C20B 29 500 Current 00 IUN1HO00 24 500 IBC1H00A Fast Raster MRA1H00H 23 000 MRA1H00H Valve VBV1H00 22 053 eP Energy Target V TP1H00A 21 650 Ion Pump VIP1H00A 20 000 1 01 Valve VBV1HO01 19 020 TV View ITV1H01 18 938 BPM IPM1H01 18 650 Quad MQA1H01 18 300 BC MBC1H01H 17 957 BC MBC1H01V 17 761 Moller target 17 5000 1H02 Quad MQM1H02 16 500 VRV1H02A VTC1H02A 1H03 Quad MQO1H03 15 415 1H03 Quad MQO1H03A 14 758 Moller Dipole MMA1H01 13 272 Ion Pump VIP1H03A 11 955 Bench BD MBD1H03H 8 132 BLM IBC1H03A 7 906 Valve VBV1H03A 7 786 BPM 7 524 Scanner IHA1H03A 7 353 Ion Pump VIP1H03B 4 486 VTC1H03A CHAPTER 2 BEAMLINE 25 BPM IPM1H03B 1 286 Scanner IHA1H03B 1 122 Valve VBV1H03B 0 953 Radiator ERR1H 0 726 TARGET TV Viewer 0 000 DUMP Face 50 000 All distances are from the center of each element to the target in meters Table 2 1 Hall A beamline elements from switchyard to Hall A beam dump revised 2 2 98
108. CE software 5 2 2 Operating Procedure Gas Flow Operating Procedures Chamber gas is delivered to a given VDC detector package via HAWGS the Hall A Wire chamber Gas System Complete details of this system are presented elsewhere in this manual Each VDC detector package consists of two VDCs connected in parallel see Figure 5 3 All gas connections are made using Polyflo tubing and Jefferson Lab specified connectors Gas enters the chamber assembly after bypassing an overpressure bubbler containing 15 mm of edible mineral oil Gas is exhausted from the VDC package through a second bubbler containing 5 mm of mineral oil Each chamber has a volume of approximately 30 and is operated slightly above atmospheric pressure Standard flow rate set points are clearly labeled next to the control panel flow meters The gas flow through the chambers may be independently varied and is typically set to 7 hr A typical chamber leakage rate measured against the 5 mm mineral oil load is lt 3 hr The flow rate of 7 hr when combined with the leak rate of lt 3 hr ensures a complete exchange of gas in the chambers roughly every 8 hours When a bottle is nearly empty say 90 it should be changed since the quality of the gas at the bottom tends to be low Gas bottles may only be changed by authorized personnel The status of the gas handling system should be monitored carefully as well as logged every shift Any substantial deviation from the media
109. Chamber Spectrometer Windows Initially the scattering chamber will have two aluminum win dows one for each side of the beam line Target Cell Failure This is a multiple loop system If a target cell fails the remaining targets will have their insulating vacuum spoiled The two spectrometer windows are both made from aluminum Each window is seven in high and subtends 170 on the 43 in outer diameter of the scattering chamber This window is made of 0 016 in thick 5052 H34 aluminum foil The scattering chamber was evacuated and cycled several times with both windows covered by the same 0 016 in material The foil forms regularly spaced vertical ridges when placed under load The window had an inter ridge spacing of 3 inches If the window is treated as a collection of smaller rectangular windows which have the full vertical height of 7 inches and the inter ridge spacing as a width then stress formulas predict that the 0 016 in material would reach ultimate stress at a pressure higher than 35 PSI There is a gate valve between the scattering chamber and the beam entrance exit pipe Both valves will be closed automatically in the event that the chamber vacuum begins to rise and an FSD will be caused this is done via a relay output of the scattering chamber vacuum gauge If either valve is closed an FSD will result In the unlikely event of a catastrophic vacuum failure it is important that the relief line of the targets be sized such tha
110. Collimator g p b 1 1 1 1 1 1 1 1 1 1 1 1 1 4 200 300 400 500 600 700 800 2 cm Figure 2 6 Layout of M ller polarimeter The origin of the coordinate frame is at the center of the polarimeter target which is 17 5 m upstream of the Hall A target The Moller polarimeter consists of see Fig 2 6 e a magnetized ferromagnetic foil used as a polarized electron target placed 17 5 m upstream of the central pivot point of the Hall A High Resolution Spectrometers e a spectrometer consisting of three quadrupole magnets and a dipole magnet used to deflect the electrons scattered in a certain kinematic range towards the M ller detector 15 CVS revision Id moller tex v 1 6 2003 06 06 21 41 39 gen Exp 16 Authors E Chudakov mailto gen jlab org CHAPTER 2 BEAMLINE 66 e detector and its associated shielding house e stand alone data acquisition system e off line analysis software which helps to extract the beam polarization from the data immediately after the data are taken The beam polarization is measured by measuring the difference in the counting rates for two beam helicity samples There are also external resources of information 2 8 2 Safety Assessment Magnets Particular care must be taken in working in the vicinity of the magnetic elements of the polarimeter as they
111. DIATION AREA SIGN and OBEY Inspect power supply platforms spectrometers and the rest of the Hall looking for water leaks and cryogenic plumes Man lift and Forklift removed from truck ramp CVS Id postBEAM for maint tex v 1 2 2003 06 05 23 30 00 gen Exp A 3 Post Beam Checklist for an Extended Time Last revised 2 22 99 This checklist will be completed prior to extended restricted accesses to Hall A People checking list _________________________________ APPENDIX A HALL CHECKLIST Power supplies from the control room Electron Ql set current to 0 amps by remote control turn output off by remote control Q2 current to 0 amps by remote control _ A turn output off by remote control Q3 current to 0 amps by remote control turn output off by remote control Dipole current to 0 amps by remote control turn output off by remote control Hadron Q1 current to 0 amps by remote control turn output off by remote control Q2 current to 0 amps by remote control turn output off by remote control Q3 __ set current to 0 amps by remote control _ turn output off by remote control Dipole current to 0 amps by remote control from the Hall Target NOTE LOOK FOR RADIATION AREA SIGN and OBEY Install protective shields over vacuum windows if Cryo target is installed target light off at target cctv cameras off
112. Electron Arm Hadron Arm Visual inspection walk through Meggelr Magnet 250 V DC Set water pressure at 100 psi inlet Coil A Trip Voltage value Coil B Trip Voltage value Magnet Lead A Trip Voltage Magnet Lead B Trip Voltage Magnet Lead Trip trim Voltage Level Trip percent 80 Magnet Flow A Trip 50 SLPM setting Magnet Flow B Trip 50 SLPM setting Magnet Flow trim Trip 3 6 SLPM setting Operational test of trips Magnet Ready for Operation Table 4 3 Hall A Q2 Q3 Quadrupole Magnet Check List 15 August 1996 CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 116 Type HAC_xt or HAC_hp as per instructions when you log on A Hall A Main Control Window pops up and all subsystem control windows can be accessed via pull down menus from there CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 117 gt Helium Fields PO GeVic Amp O 1 Flow SET Figure 4 6 Magnet Portion of Main Hall Control Screen 4 2 Field Monitoring 4 4 2 1 Simple Spectrometer Field Setting Autopilot Mode All you need when everything is working and power supplies are turned on and ready to go On the Hall A main control screen there is a rectangular box for each spectrometer that looks similar to the illustration see Figure 4 6 This box displays a brief summary of the status of the spectrometer magnets and their cryogenic systems The blue fields wit
113. FLOW CONTROLLER Figure 5 32 Block Diagram of Mass Flow Control System set in the FM 8 by an operator a correction signal is sent to adjust the valve in the flow controller The DM 2401 FM 8 system allows the user to define up to four mixture flow settings Refer to the Dynamass System manual and to section 3 3 3 Setting a Flow Rate for more detail on operating the flow controllers The measured flows of the three component gasses are combined in a small blending tank in the back of the mixing station The resulting mixture is delivered to the alcohol bubbler through a line which is teed to an overpressure relief valve RV 271 set for 25 psig This prevents overpressuring of the blending tank the bubbler or the delivery lines Alcohol Bubbler Because the interesting alcohols for use in wire chambers have a feeble vapor pressure at room temperature it is not convenient to purchase bottled gas with alcohol already added A practical means of adding alcohol vapor to a gas is to pass the gas through a reservoir of the liquid alcohol which is maintained at a specified temperature At a given temperature the vapor pressure of the alcohol may be known and this vapor pressure represents directly the partial pressure of the vapor in the gas mixture The vapor pressures of organic compounds may be calculated from information in the CRC Handbook of Chemistry and Physics where it has been parameterized as
114. Gas pressure out of mixer bubbler rack is gt 18 psi eReset Dynamass Controller elf needed vent excess pressure using MV 299 Pressure switch in rear of Mixing Station mixer bubbler rack CHAPTER 5 HRS DETECTORS 208 Resetting a closed Excess Flow Valve Each Excess Flow Valve automatically closes if the flow rate through it exceeds about 4 slpm at 45 psig The exact flow threshold varies somewhat depending upon the delivery pressure These valves must be manually reset after they trip This is done by rotating the red handle 90 CW to OPEN RESET and then 90 CCW back to AUTO SHUTOFF It will be necessary to keep the valve in the OPEN RESET position for about 10 seconds until nominal pressure builds up downstream The excess flow valves must be returned to the AUTO SHUTOFF setting to insure system safety Restoring flow after a Low Supply Pressure shutdown If the gas pressure in any enabled supply line to the mixer rack drops below about 40 45 psig the interlock will sound an alarm and close all of the solenoid valves This prevents the system from delivering a bad mixture to the detectors After restoring the gas supply for example after replacing an empty gas cylinder perform the following steps to restart the flow of gas 1 Verify that no faults other than Low Pressure and Main Relay are indicated on the gas interlock panel 2 Insure that all high pressure manifolds are pressurized a
115. IGH RESOLUTION SPECTROMETERS HRS 104 Shield House Shower Counter Preshower Counter Scintillator 2 co 2 Cerenkov Aerogel Cerenkov Scintillator 1 Vertical Drift Chambers 1 7 96 Figure 4 3 The electron spectrometer detector stack The next element encountered by a particle is a gas threshold Cerenkov detector This is used for particle identification In the hadron spectrometer this gas threshold Cerenkov detector can be swapped against an Aerogel detector with a similar function The second hodoscope plane 92 is located directly behind the gas Cerenkov Its function is essentially the same as that of S1 In the hadron spectrometer an option exists to have this hodoscope pair be preceded by a third chamber to improve tracking Each of the two spectrometers have gas and Aerogel Cerenkov detectors which can be used when they are in electron detection mode The final elements in the detector stack on HRSE are the pre shower and the lead glass shower calorimeter T his is used for energy determination and PID The hadron detector is shown schematically in Figure 4 4 It consists of two sets of x y vertical drift chambers identical to those of the electron arm The remaining part of the detection system is used to define the level 1 trigger as well as for particle identification and timing It consists of three minimally segmented planes of scintillation counters equipped with photomultipliers at both ends and it includes Cerenk
116. IM ECL gt NIM T2 MLU out 5 E2 18 19 E2 18 19 Upstream BCM gt 14 ECL gt NIM Upstream BCM V F Downstream BCM gt 16 to SCALER 4 Phillips Downstream BCM V F ECL gt NIM E2 6 7 Coincidence Trigger 11 14 97 Figure 7 3 Coincidence Trigger Circuit CHAPTER 7 DATA ACQUISITION AND TRIGGER 225 is in the H arm and that the E arm has an electron with respect to which the H arm must be delayed Then trigsetup loads the correct default setup file and starts XTrigMang which pops up At this point you simply press the Download All button in XTrigMang to setup the trigger If individual modules need to be modified for test purposes etc e g to change thresholds one may press on the buttons in the XTrigMang GUI and pop up the com ponents in an obvious way Each component has four buttons which it is essential to understand 1 The Set button One must enter the choice and then press Set This loads your choice into memory on the workstation not on the CAMAC crate 2 The Down button This sends whatever choice is in memory to the CAMAC crate 3 The Show button This reads back from CAMAC what is actually in the module 4 The Read button This shows what is in memory on your workstation Note that read is quite different from show A typical operation to modify a trigger module would be to Set the value Download it and then Show to check that the value is
117. If it occurs again force the probe selection by opening arc nmr adl medm screen then switch to man ual selection mode click on the probe you want to select and wait for NMR lock Don t forget to return to the auto selection mode before leaving the integral measurement Report about the problem in the e logbook expert users can also use nonstandard search modes and DAC values as proposed by the arc nmr adl screen Dac Value Dac4 596 and All Probes Range Note that Dac Value needs a scope They are asked to restore the standard mode SeLected Probe Range at the end The DAC to field relationship used by the software is linearly interpolated in the table from file magnet dir dac 0 dac 1000 dac 2000 dac 3000 dac 4095 Probe T T T T T 040362 05388 07443 104184 182404 1 080718 107771 148845 208340 264790 2 161430 215539 207680 416680 529570 3 322870 431112 595471 833455 1 059210 4 Note as the 9 dipole has a uniform field there is no gradient coil around the probes and the lock is in general easier to obtain than with the HRS dipoles Nevertheless some difficulties may occur at low field due to the hysteresis gradient The NMR system is the same as for the HRS Metrolab but the EPICS implementation is different The CHAPTER 2 BEAMLINE 50 field polarity is Some lock problems may apear in the 60 70 range In this
118. Introduction Location of Hall Safety Items 15 Introduction Location of Circuit Breakers 16 Beamline Hall A Beamline Overview 18 Beamline Hall A Beamline Overview 18 Beamline Hall A Beamline Overview 19 Beamline BPM Readout Electronics 26 Beam Current Measurement Schematic 29 M ller va so x p hoe Re Dee ee GES Se OE OEE 65 Waterfall Target System 82 Waterfall Target Cutaway of Target 84 Waterfall Target Three Foil Geometry 84 Waterfall Target Target 85 Waterfall Target Side 85 Waterfall Target Hydraulic Schematic 87 Waterfall Target 5 88 Waterfall Target Slow Controle ss pocs sop x Ro R3 y 3s 89 Waterfall Target Signal Layout 2022 22 22 ooo Rs 90 Spectrometers Elevation View of Hall A HRS 102 Spectrometers Plan View 103 Spectrometers Electron Arm 104 Spectrometers Hadron Arm Detectors 105 Spectrometers HRS Vacuum System 108 Spectrometers Magnet Controls 117 Spectrometers NMR System Layout
119. KK KKK KK OK 2K e KKK KK K K K K 21 06 99 Pascal Mesur Nb 2 Second measurement on 21 06 Encoder reading for upstream scanner of downstream bench 118405 3 Encoder reading for downstream scanner of down bench 118408 4 H1 H2 V1 V2 0 000100 179 998100 90 003800 270 003000 Autocoll 6 100800 186 100400 110 667600 249 338500 3 6 176000 186 176100 249 130700 110 875600 4 45 2 4 19 More on the theodolite menu It is a 2 level menu the entry point after power ON and indexes initialization is at the 2nd level Theodolite the buttons are used to navigate among several choices the enter button to validate the currently proposed choice In the above list will move to the next option down to the previous one up and enter will answer yes to the proposition In some cases SET A the choice is just yes no Then enter means yes and or means no 1st level menu e gt M Measure e A Adjust e U Unit 2nd level menu M Measure e gt M 0 Return to 1st level e M 2 THEODOLITE theodolite e M 5 Zero angle gt A 0 Set angle gt Set A to value e M 7 Hold angle gt Hold angle CHAPTER 2 BEAMLINE 46 2nd level menu A Adjust e gt 0 Return to 1st level e 1 Adjust V index gt Adjust V index e A 2 Adjust A col
120. L while 40 LEL activates the high level alarm Each channel has a relay output for both low and high level alarm states and there is also a set of common relays for both alarm levels these common relays respond to the logical or of the sensor inputs The common relays will be connected to the Fast Shut Down System FSD which removes the beam from the hall by disabling a grid bias at the injector 3 2 2 Pressure The most important aspect of hydrogen safety is to minimize the possibility of explosive mixtures of hydrogen and oxygen occurring Therefore the gas handling system has been made of stainless steel components wherever possible and as many junctions as possible have been welded The pressure in the gas handling system is monitored in numerous places Most importantly the absolute pressure of the target is viewed by two pressure transducers one on the fill line 127 for and PT136 for and one on the return line 131 for H and PT140 for D These pressures are also measured by manual gauges The fill line gauges are PI126 for and PI135 for D The return line gauges are designated PI130 and 139 Ds The gas tanks are viewed with both pressure transducers PT133 for hydrogen and PT142 for deuterium and pressure gauges PI123 for hydrogen and PI112 for deuterium Target Cells The target cells themselves represent the most likely failure point in the hydrogen system The outer walls and downst
121. Logl0P 0 2185A K B 5 1 where P is the pressure in Torrs K is the temperature in Kelvin and A and B are parameters provided in the Handbook for a number of compounds For isopropanol CHAPTER 5 HRS DETECTORS 197 Vapor Pressures 1 0000 sopropanol Ethyl Alcohol 0 1000 0 9 5 0 0100 9 gt 0 0010 20 00 10 00 0 00 10 00 20 00 30 00 40 00 Temperature Figure 5 33 Vapor Pressures of Isopropyl and Ethyl Alcohols calculated using the CRC Handbook parameterization CHAPTER 5 HRS DETECTORS 198 within the temperature range 26 1 C to 232 0 C the parameters given are A 10063 5 and B 8 996156 For Ethyl Alcohol the parameters are A 9673 9 B 8 827392 At 0 C for example this formula gives the vapor pressure of isopropanol as 0 0115 Atm 1 Atm 760 Torr If the gauge pressure of the bubbler gas vapor is 1 atmosphere 2 Atm absolute pressure as intended for Hall A then the fraction of alcohol vapor by partial pressure is about 0 57 Figure 5 33 shows the vapor pressures of these alcohols as a function of temperature Note that the bubbler temperature defines the vapor pressure and thus the dew point for the vapor in the gas If the gas comes in contact with any surface which is colder than the dew point the temperature of the bubbler the alcohol vapor will condense on that surface This is why it is important that all components of the ga
122. MT BURLE 8575 PHOTOMULTIPLIER TUBE DYNODE CHAIN 9 dS 906 47 98 99 A0 011 02 05 500 10M 1 100 100k 100k 100k 100k 130k 100k 100k 100k 100k 100k 100k 100 100k 100k 100k 10k M Q Q Q O Mu metai HV internal shield Signat shield resistors 6 Watt Metal Film Capacitors gt 200 V Values In microfoarads UNIVERSITY of REGINA Facuity of Science Electronics Shop Trtte Burle 6854 Tube Dynode Cham Figure 2 Date 17 Dec 90 version L Wirth matching pot Fite 8575 Note Figure 5 10 The 2 PMT base used 51 and 52 trigger scintillators Both 2 and 5 bases have been extensively tested under beam conditions They have several safety related features but these cannot protect anyone who is bent on violating operating procedures and common sense They allow the removal of the PMT Base assembly for repairs of the electronics or replacement of a PMT without decoupling the housing and collets from the light guide Thus replacement of PMTs can be done in minutes without the need to remove the scintillator counters from their subframes CHAPTER 5 HRS DETECTORS 152 5 3 7 5 PMT Bases for S3 Counters The general layout of the 5 bases is similar to that of the 2 bases described above It consists of a front tubular housing and a rear tubular housing both made out of aluminum They join at a coupling nut as shown in the schematic diagr
123. OC hallasc16 Gochla H motion IOC BPM IOC hallasc7 iocse 10 Hadron Spectrometer Beam Line HALL A Figure 6 1 Schematic of the Hall A controls system 214 NYV TJoresgja00V CHAPTER 6 SLOW CONTROLS Hall A General Tools HELIUM mj 1 FLW ERATI EZ 1 7202 2146547 eeu K SEO 587 A FIELDS ml GeVic PO SET fizan GeV c 6 Degrees HELIUM Sf FIELDS 8 P A 19 FLW ih B_VDC BRE lh FPP1 FPP2 i LEFT COLLIMATORS RIGHT Emm Beamline Set Energy op total E MBSY1C Current ERA MBsvicBd mE ESSEN BPMB v EE on RF Off E Mode REL RMS beam motion um 0000 GAS SHED ARGON Ps ETHANE Ps EM ps 215 MISCELLANEOUS FPP m Moller _ amp f Crate Resets m ALIGNMENT cents YPM cnts Over Range hp vp LEFT p L vp RIGHT Tilt X V Tilt Y V Tilt T C FRONT 9 gt m gt CAMERA _move ROLL mrad PITCH mrad Horz Pt mm Angle deg ERROR Fir Mrk deg Vernier mm RIGHT VDC DISC LVL LEFT VDC DISC LVL Figure 6 2 Hall A Main Control Screen Cha
124. ODA WWW page http coda jlab org 216
125. Q3 where a particle first traverses Q1 then Q2 and the dipole magnet and finally traverses Q3 The magnet system is followed by a large steel and concrete detector hut in which all detector elements reside Most of the detector elements have been built by universities involved in the Hall A physics program The HRS magnet system is the cornerstone of the Hall A activities Many of the experiments approved in Hall A center on physics at high resolution and other short range phenomena and rely on a spectrometer able to momentum analyze charged particles up to very high momenta The design value for the maximum momentum accessible to the HRS magnet system is 4 GeV c CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 111 Magnets and Power Supplies The HRS magnet s are all superconducting and hence their coils must be maintained at cryogenic temperatures during operations The LHe required by the magnets is supplied by the End Station Refrigerator ESR All the HRS magnets cryogenic services are supplied through the overhead cryogenic lines The distribution network begins at the distribution box over the pivot This box is connected to the rest of the network via the flexible transfer lines over the pivot The network is adjacent to the upstairs catwalk of the HRS Cryogenic information about each magnet is available on the control screens in the counting house one for each magnet Normally during run periods the control screens are sent upstai
126. TJNAF Hall A Experimental Equipment Safety Assessment Info Level 0 The Hall A Collaboration Editor E A Chudakov June 6 2003 Thomas Jefferson National Accelerator Facility Contents 1 Introduction 10 LI General eu OR BR S Ee ERE eee Rub AB ee 10 12 The Personnel Safety System 10 1 2 1 Restricted Access rca ecri 90 33e ey ow ox on 10 A o E ON PPP 11 1 2 3 Controlled 11 LAT RF Power Permit Oe doe ata eee Nee ew og 12 Beam Permit auod Ru Wd X e ee 12 126 ie pale BORES i o eee ORE RO 12 13 Hal A ROG Lus oes Sek her KE Roe Rehd CEO DEVE 12 1 3 1 Controlled Access 13 1 3 2 Restricted Access 18 1 8 8 Access Requirements 14 1 8 4 The Hall A Safety Walk through 14 2 Beamline 17 2 1 General Description uuu e ook om RR RE EROR GRUT ee 17 211 Introduction 13 3 2 333 3 43 OSA 17 2 1 2 Authorized Personnel 20 2 1 8 Additional Safety Information 20 2 1 4 Machine Beamline protection system 21 2 1 5 Personnel Safety System lt s a scoa rrara ror a ta Goa s 21 22 Deam Position Monitos lt lt 0 pek pa AT ee a E wee RE 26 2 3 Beam Current Measurement
127. Vv 8 2 MQ field lines Wh 10kQ U signal wires 6kV HV plane 3 ay 8 2 MQ WWII 10 KQ Figure 5 4 VDC overview CHAPTER 5 HRS DETECTORS 141 control software and also provides a monitor of the current drawn nominally 70 nA by the VDCs to which it is attached Connections from the power supply to the Hammond splitter box as well as from the Hammond splitter box to the VDCs are made using standard SHV connectors mounted on red RG 59 U HV cable good to 5 kV A Kepco ATE 15 3m discriminator power supply provides 3 0 V 92 cards draw lt 2 A and the Kepco ATE 6 100m pre amp power supply provides 5 V nominal to the LeCroy 2735DC pre amp discriminator cards used to instrument the chambers via a heavy duty fuse panel The precise voltages provided are 5 0 V 92 cards draw 22 A and 5 2 V 92 cards draw 58 A These LV supplies are located in the detector hut on the main level of the space frame for the HRS and on the upper level of the space frame for the 5 Complete connection schematics and instructions for making or breaking the connections are located on the aluminum Faraday cage protective plates covering the respective interface nodes between the power supplies and the VDCs Each VDC wire plane consists of 400 20 wm Au plated tungsten wires The first 16 wires on each end of the wire plane are connected to ground f
128. acB user were using the MacA BE CAREFUL the performance is reduced due to the connection Be patient wait for the screen to refresh after any action Startup of the system The system startup depends on the history of the shutdown After a normal shutdown In the hall e Go to the right side of the right rack and push the green start button of the right box you will hear a beeping sound e Go to the front of the left rack and push the green button near the emergency one e Wait for the MacA to be operative e Click on the HROCEBAF97 icon the slow control program for the water target at CEBAF which is almost in the center of the MacA desktop The LabView application will run automatically and the slow control main window will be shown e Push the arrow button on the top left side of this window in order to start the program The first time the program is run after MacA power on it initializes the electronic modules Every time the program is run it asks for a new initialization of the electronic modules Answer YES a small window with 4 buttons appears Press all the buttons in order from top to bottom When the initialization is done the main window comes back After an emergency shutdown e Recognize the cause of the emergency and fix it e Release the emergency button in the hall or in the counting house depending on which one was used for the emergency shutdown in order to restore its operation The system will be ener
129. ach door Blue switches then to turn on the 12V power to each door to see where it is located in the stack in vs out If you wish to change the status of a door in out then simply toggle the IN OUT switch appropriately and turn on the 90V It takes some time for the doors to move the entire range so be patient When the limit switches have been reached the appropriate indicators will light up You should then turn the 90V off The important aspect of this procedure is to make sure that you do not change the polarity of the 90V while the doors are moving This place undue stress on the motors and the power supply as well 5 6 4 Handling Considerations The FPP straw chambers are very delicate devices which are absolutely essential to many Hall A physics experiments Thus extreme care must be taken whenever they are moved or used Also extreme care must be taken that other objects are not moved into them CHAPTER 5 HRS DETECTORS 189 0 HacH_DTC_Carbon_status adl nx HRS HADRON SYSTEMS FPP Carbon Doors FPP Carbon Door Control 12V OFF ON OUT IN 30V OFF ON 3 4 inch Not working 1 5 inch Door sable nable sable nable 3 inch Door sable nable sable nable 6 inch Door sable nable sable nable 9 inch Door sable nable sable nable FPP Carbon Door Status Left limit Right limit Door status 3 inch Door Closed Door operation 1 Turn door circuit on by clicking 12V ON 2 Check status indicators Door Status o
130. ack into the reservoir All parts in contact with the water are made of stainless steel In the target zone the water pressed through a system of slits and holes and guided by the stainless steel bars forms one or more flat rectangular films which are stable due to the surface tension and to the adherence to the guiding bars The thickness of the foil s is to some extent a function of the pump speed which determines the flow rate Once the foil is formed there is a minimum value of the pump speed flow rate for this depending on the particular target the thickness increases with the pump speed The maximum pump speed depends essentially on the dimensions of the slits and holes the water passes through An absolute calibration of the target thickness as a function of the pump speed needs to be done before the experiment One way of measuring the absolute target thickness is to measure the raw counting rate in the spectrometer The target used for E89003 and E89033 was at a fixed angle during the experiments Therefore the waterfall target container is designed as a box with dimension of 630 x 68 x 8 mm The entrance and exit windows of the target cell are circular 40 mm in diameter and are made of gold plated Be 75 jum thick Fig 3 2 3 3 Scattered particles go through the lateral windows made of stainless steel 25 jum thick dimension of 320 X 8 mm Some schematic views of the target container are shown in Figures 3 2 3 3 3 4
131. aels mailto rom jlab org CHAPTER 7 DATA ACQUISITION AND TRIGGER patch row 1 fixed able dela 1 12 14 4413 200 DISCR S1R 1 6 gt 1 6 S2R 1 6 gt 7 12 pulser gt 14 E1 2 S1L 1 6 gt 1 6 4413 200 DISCR S2L 1 6 gt 7 12 pulser gt 14 E1 14 1 12 14 4413 200 DISCR 1 16 AEROGEL CERENKOV 4413 200 17 26 DISCR PRE SHOWER ANALOG 1 48 MIXER 1 12 14 222 to ADC to SCALER modular to TDC S1R OR 870 ns OR S2R OR NIM 1 12 14 RETIMING rear panel out i 4518 300 DELAY to 4518 100 Phillips 4518 100 6 gt 1 4518 100 DELAY FQ E1 18 in E ARM DELAY FO DELAY FO X5 ECL gt NIM E1 4 E2 12 E2 6 7 RETIMING DELAY o SCALERS CEBl to SCALERS CEB2 ENABLE S RAY gt 1 4518 100 2373 DELAY FO MLU E1 6 34 7 14 E1 8 E1 10 INPUT B pulser 14 S1 OR OR 1 12 14 S2 0R 7 4518 100 to SCALERS CEBO DELAY FQ 1 12 14 E1 12 1 12 14 modular to TDC 880 ns PROMPT TRIGGER Tl _ to ADC SRAY fixed patch row 2 able dela to SCALERS CEB3 2373 Y crs 4413 200 4518 100 NIM ANALOG SUM gt 11 C G SUM 52 MIO LINEAR DISCR DELAY FO FAN IN 1 11 11 gt 1 10 2 2 2 4 C A A E2 8 1 11 modular to TDC 880 ns dela 1 11 fixed to ADC able dela patch row 3 fixed to ADC able dela modular to TDC PROMPT TRIGGER T2 fixed No SRAY but all possible combinations of S1 S2 C G C A with one missing 4518 100 S1 S2 DELAY FO SRAY S1 S2 C G 1 16
132. ait for the NMR lock for up to 1 minute Note due to the software the position readback may be updated 10 seconds after the real probe motion Zd 0mm is for the upstream position 1604mm for the central position and 3208mm for the downstream position If the probe does not obey call Arun If Arun is not available reboot the ioc see integral ioc reboot below CHAPTER 2 BEAMLINE 49 check if the NMR probe selected is the good one The system has 4 probes to cover the field energy range 0 043T 0 517GeV 1 05T 12 63GeV The software selects automatically the probe from an estimated field and the following range table from file magnet dir mini maxi probe T T 0 043 0 1254 1 0 1250 0 250 2 0 177 0 470 3 0 338 1 06 4 The estimated field is computed from the set current and the coefficients given above Note that there is an overlap between the range of each probe In the standard mode auto selection two selection algorithms are used initial selection select the probe in which the estimated field will be the most centred routine check change the probe only if the estimated field is outside the selected probe range Initial selection is executed at boot time at each integral start and when you leave the manual selection optional mode The routine check is performed periodically In some cases in the past this algorithm did not select the best probe
133. al was obtained from exposed negative film used in the cartographic industry and is of high smoothness and uniformity One side was aluminized at CERN while the other side remains in its exposed negative black state further adding to the successive light penetration barriers into the enclosure A representative reflectivity curve as a function of A for these mirrors is shown in figure 5 21 The upper section of the counter containing the mirrors is mounted on its own 13DuPont Canada Inc Box 2200 Streetsville Mississauga ON L5M 2H3 Canada National Metalizing P O Box 5202 Princeton NJ 08540 USA CHAPTER 5 HRS DETECTORS 167 aluminum subframe which is bolted to the main frame that houses the PMTs The upper section on its own is shown in the photograph of figure 5 22 while its configuration when mounted on the main section is shown in figure 5 19 The light and gas sealing action is provided by continuous twin parallel rubber strips along the joint area and by Tedlar film of 0 025 mm thickness covering the top of the outer planar parabolic area The third major component of the counter consists of a removable tray where the silica aerogel is placed The tray occupies the bottom part of the counter and has inside dimensions of 195 x 41cm where the SiO silica aerogel is placed It is formed by a frame with twin aluminum panels which in turn secure the removable frame strung with fishing line in a criss cross pattern to hol
134. all A Gas Shed alongside of the truck ramp for Hall A The gas cylinders in use are along the outside of the Gas Shed in a fenced area There are racks next to the Gas Shed for storage of full gas cylinders On the other side of the truck ramp there are racks for storage of both full and empty cylinders Hall A currently uses ethane argon ethanol two grades of CO2 and nitrogen One system uses two cylinders of SFC grade CO2 without a helium head This is for the gas Cerenkov counters in the HRS detector arrays One system uses two cylinders of Coleman grade CO2 This is for flushing the aerogel Cerenkov counters in the HRS detector arrays One system uses a single cylinder of Coleman grade CO2 This is for the gas Cerenkov counter in the e p setup in the beamline One system uses two cylinders of Zero grade argon and two cylinders of Chemically Pure grade of ethane This is for all the HRS wire chambers of both arms The two gases are mixed inside the Gas Shed and bubbled through ethyl alcohol Details of this system can be found in the Hall A Wire chamber Gas System HAWGS manual A copy of the current manual is in Counting Room A and on the Hall A web page One cylinder of Industrial grade nitrogen is used to provide pressurized gas for a few automatic cylinder switch overs in the systems Maintenance of the gas system is routinely performed by the Hall A technical staff Shift personnel are not expected to be responsible for maintaining the
135. ally plugged into the ADC channels and connected to the signal wires labelled as shown in the diagrams below for both the preshower counter and the total absorber counter 5 4 3 Handling Considerations The shower counters are very delicate devices which are easily damaged Thus care must be exercised whenever they are moved or used CHAPTER 5 HRS DETECTORS Nominal High Voltage Settings for Electron Arm PreShower Table 1 Oct 10 1997 Pre Sh HACI RV v slot Block chan uu usd bo en tem gt li r gt T um f rt HACS chan HY V BER 1180 72 1075 1180 Um 1140 1105 LN LN m 198 7 0 7 1 7 2 7 3 7 4 TA T 6 77 TA T 9 81 87 11 1274 1174 1100 1174 ao 1160 at 1180 2 1144 Em 1180 1180 1094 a6 1200 1165 1204 ao 1160 1155 amp 1240 Figure 5 13 Typical values of the preshower counter high voltages 158 CHAPTER 5 HRS DETECTORS 159 Nominal High Voltage Settings for Electron Arm Shower Table 1 Oct 10 1997 ke pen HY HV idi HY egi HY du ua chan 47 1470 fiso to 1800 1115 y gt c 1440 1550 395 per pera uer Ec rares Ee Cal ds num CZ Ee m gt
136. alues belong to a parallel electronics chain whose constants have to be retrieved by calibrations to the EPICS or scanner data CHAPTER 2 BEAMLINE 28 2 3 Beam Current Measurement 6 The Beam Current Monitor BCM is designed for stable low noise non intercepting beam current measurements It consists of an Unser monitor two rf cavities the elec tronics and a data acquisition system The cavities and the Unser monitor are enclosed in a box to improve magnetic shielding and temperature stabilization The box is located 25 m upstream of the target You can recognize it as a grey object on the stands about 2 m downstream from where the beam enters the hall The DC 200 down converters and the Unser front end electronics are located in Hall A The temperature controller the Unser back end electronics and its calibration current source cavity s RF unit housing the RMS to DC converter board and all multi meters VME crate and computers are located in Hall A control room 2 3 1 System Layout The schematic diagram of the BCM system is presented in figure 2 5 The Unser monitor is a Parametric Current Transformer designed for non destructive beam current measurement and providing an absolute reference The monitor is cal ibrated by passing a known current through a wire inside the beam pipe and has a nominal output of 4 mV yA It requires extensive magnetic shielding and temperature stabilization to reduce noise and zero drift As the Unser
137. am of Figure 5 11 The actual base where the PMT p metal shield and the electronic dynode amplification chain are located is different The corresponding middle section incorporating the above components is made out of a moulded structure used in both the 5 bases and the aerogel Cerenkov counters The PMT socket is moulded integral to the section and it is also spring loaded The collets are different due to the size of the light guide but the method of assembly is very similar to that of the 2 base MAR 03 1994 FRONT FRONT 2 057 5 INCH FaMi T BASE dim in Willimeters MAX COLLET SIZE 120MM DIA 7 7 Pa MIN COLLET SIZE 10MM MAX EXTENSION OF COLLET Figure 3 Figure 5 11 The 5 PMT base used in 53 trigger scintillators CHAPTER 5 HRS DETECTORS 153 Assembly Instructions The collet assembly consists of several expanding rings one set of solid tapered and the other a spring collet They are placed on top of each other alternating between the two kinds with a spring collet on the top facing the scintillator and the collet nut As the collet nut is screwed in it presses against the assembly and the spring collets slide inward against the tapered solid ones thus clamping against the light guide Care should be taken when placing these two different kind of collets inside each other so as not to align the gaps in the plastic and create light leaks The collets are not continuous ring
138. and related Search for answers among the following The standard lore is that 30 deadtime is tolerable but you should ask your analysis team to decide Sometimes people seeing large deadtimes have forgotten to observe that the beam is in pulsed mode Another possibility is that the workstation is overloaded The computer used for CODA should not be used for much else Do not attempt to read or write rapidly to the same physical disk to which CODA is writing Sometimes it is observed that the workstation itself is very sluggish This could be due to a foreign mounted disk having gone away and there are other possible reasons If a Cold Start of CODA doesn t solve this you may try rebooting the workstation see computer section Also if the event size changes substantially e g due to noise conditions the deadtime as a function of rate will change especially in the regime of high rates Cold Start of CODA If CODA is not running or if it gets hung up you can do a cold start Frequently a subset of these steps is sufficient to recover from a hangup but it takes some experience to realize the minimum of steps that are necessary so the simplest thing is to do them all it takes a few minutes e Kill off all CODA processes on the workstation by typing kcoda This stops runcontrol the event builder and other processes and allows for a clean start e Make sure the fastbus and VME crates are running The crates are named below as
139. are made up of one each of the manufacturer s type 3 4 amp 5 probes designed to cover different field ranges see Table 1 The six Purcell Gap Probes Group 1 in the controls are located in the Purcell gap of the magnet and consists of two each of the above types Note Since the fall of 1998 the multiplexer multiplexer in the electron arm MUX 2032 has been bypassed and hence the Purcell Gap Probes are currently unavailable There are no plans to fix this multiplezer in the immediate future The Gap Probes are equipped with coils which provide a field gradient that can cels out the field gradient of the magnet in the vicinity of the probe These gradient compensating coils are part of a simple circuit that is completely independent of the Teslameter The basic circuit for the compensating coils is shown in Figure 4 8 The following graphs see Figures 4 9 and 4 10can be used to determine optimum values for the compensating coil control voltage It should be noted that the setting of the compensating coil current is not very critical in most cases In general if you re within 1096 of the correct value everything should work fine 4 2 3 Authorized Personnel The following individuals are responsible for NMR operation problems J Gomez x7498 J LeRose x7624 CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 120 Comp Coil Voltage Bectron Dipole optimizedforthe lowfield probe 1 16 8 7 90009 4 38 16 0 F 9 9901 5
140. arget 25 Beamline Optics Requirements Other 25 Bremsstrahlung Radiator Raster 63 Bremsstrahlung Radiator Encoder Calibration 63 Moller Polarimeter authorized personnel 67 Cryotarget Cell Pressure Test 74 Cryotarget Relief Device 75 Cryotarvet Gas Properties 24 6423 ee dace ee E Eg 76 Cryotarget Volumes and 77 Cryotarget Relief Line Information 78 Contact Personel for the Cryogenic Targets and Scattering Chamber 81 Spectrometers Dipole Checklist 00008 114 Spectrometers 1 115 Spectrometers Q2 Q3 115 Spectrometers Dipole NMR Probe Field Ranges 119 NMR troubleshhoting sacose RSet eee eee Re eee Rom ea 125 Detectors Electron ARM Detector Locations 134 Detectors Hadron Arm Detector Locations 135 Aerogel the number of photoelectrons 176 Aerogel photoelectrons 176 Data Acquisition Terminal Service for DAQ 220 List of Figures Lil 1 2 2 1 2 2 2 3 2A 2 5 2 6 3 1 3 2 3 3 3 4 3 5 3 6 3 7 3 8 2 9 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 4 10 4 11 4 12 4 13
141. ata one of the amplifier outputs is sent to a high precision digital AC voltmeter HP 3458A Each second this device provides a digital output which represents the RMS average of the input signal during that second 5 OVS revision Id bcm tex v 1 3 2003 06 06 15 19 02 gen Exp Authors A Saha mailto saha0jlab org CHAPTER 2 BEAMLINE 29 KEITHLY lt 554 1 L DCx1 to V2F Y 10 kHz roo DCx3 to V2F ic L d i A 5 5 DCx10 to V21 i Pi 1 i DCx1 to V2F i 10 kHz DCx3 to V2F i Downstream i L BCM i DCx10 to V21 DCxl to V2F DCx3 to V2F DCx10 to V2I e Beam DCxl to V2F Hall A BCM System 3 r i gt i D i i i i i Upstream Exp Hall Counting House Figure 2 5 Schematic of the Hall A beam current measurement system CHAPTER 2 BEAMLINE 30 The resulting number is proportional to the beam charge accumulated during the cor responding second or equivalently the average beam current for that second Signals from both cavity s multi meters as well as from the multi meter connected to the Unser are transported through GPIB ports to the HAC computer where they are recorded every 1 to 2 seconds via the data logging process which is described in the calibration proce dure They are also sent through EPICS to CODA and the data stream where they are recorded at
142. ation LeCroy HV 1460 modules are used to supply HV power for the trigger counters The HV can be controlled from a VT100 terminal connected through a terminal server or through the EPICS system based on the HAC computer Current HV settings for the trigger counters should be found from a printout of the EPICS control in the last experimentallogbook Figures 5 6 and 5 7 give examples which are included for guidance only The settings used in the plots may be not correct 5 3 3 PMT operation monitoring There are two ways to monitor PMT detector performance The first is based on a scaler display program which provides information about PMT counting rates and coincidence counting rates A large variation of the rates between paddles is an indication of a possible problem The second technique is to use the analysis code ESPACE and the kumac files developed by Takahashi kazu files This analysis provides amplitude spectra for events with good tracks in the VDC Histograms of amplitudes and average amplitudes for each PMT are accumulated For high efficiency of the trigger it is important to keep the average amplitude above 600 channels Sample spectra are shown in Fig 5 8 5 3 4 PMT replacement Because of a large contamination of He in the air around the detectors the quantum efficiency of the PMTs slowly decreases about 5 10 per month in case of high rate operation The replacement of a PMT takes about 15 20 minutes 5 3 5 2 PMT
143. can have large currents running in them Only members of the Meller polarimeter group are authorized to work in their immediate vicinity and only when they are not energized The quadrupole magnets and the leads for the dipole mag net are protected with Plexiglas shields As with all elements of the polarimeter which can affect the beamline the magnets are controlled by MCC There are four red lights which indicate the status of the magnets The dipole has two lights which are activated via a magnetic field sensitive switch placed on the coils of the dipole One light is placed on the floor on beam left and the other is placed on the raised walkway on beam right The quadrupoles have similarly placed lights one on the floor on beam left and one on the walkway and are lit up when any one of the Moller quads is energized The status of the quadrupole power supplies is on the checklist for closing up Hall A Lock and tag training is required of all personnel working in the vicinity of the Moller magnets The power supply for the dipole is located in the Beam Switch yard Building Build ing 98 The maximum current for the dipole is 450A The quadrupole power supplies are located in Hall A electronics rack 13 2 supplies connected in parallel per one quadrupole The maximum current per one power supply is 60A at about 20V Vacuum System One must be careful in working near the downstream side of the dipole magnet as there are two 2 by 16 cm 4 mil
144. chamber requires 5 0 V 92 cards draw 22 A 5 2 V 92 cards draw 58 A and 4 3 0 V 92 cards draw lt 2 A Explosive Gas The Ar chamber gas is explosive and must be handled accordingly Further gas flow should be maintained for at least 24 hours prior to the enabling of HV High Pressure Gas Bottles The gas used in the chambers is supplied in high pressure gt 2000 psi gas bottles This confined high pressure gas represents a tremendous potentially lethal amount of stored energy 5 2 6 Responsible Personnel The following individuals are responsible for chamber problems Chai Zhengwei x5923 pager 849 5441 Fissum Kevin x7325 pager 849 7325 Liyanage Nilanga x7254 pager 849 7254 Rvachev Marat x7325 pager 849 7013 Segal Jack x7242 pager 849 7242 Wojtsekhowski Bogdan x7191 pager 849 7191 CHAPTER 5 HRS DETECTORS 144 5 3 Trigger Scintillator Counters 7 5 3 1 Overview On each HRS the detector system has two planes of trigger scintillators S1 and 2 The HA detector stack includes an optional third plane S3 The mounting schemes of these planes are different S1 is clamped to the detector frame through an additional Al channel while S2 is assembled on a sub frame which can slide on rails into the detector frame 53 has strong a heavy sub frame which can be mounted on the top of the HA detector frame Figure 5 5 shows the mounting scheme for 51 Figure 5 5 51 mounting 51 and 52 each con
145. chamber but this target is not usually connected to a full gas handling system This third loop is used as a helium target The hydrogen and deuterium targets present a number of potential hazards such as the fire explosion hazard of the flammable gas as well as the hazards connected with the vacuum vessel and the of handling cryogenic liquids ODH and high pressure In this document the hydrogen target will be referred to but the deuterium target is essentially identical and almost all comments apply to both targets 3 2 1 Flammable Gas Hydrogen and deuterium are colorless odorless gases and hence not easily detected by human senses Hydrogen air mixtures are flammable over a large range of relative con centrations from 4 to 75 by volume Detonation can occur with very low energy input less than i that required by mixtures of air and gasoline At temperatures above 250 C hydrogen gas is lighter than STP air and hence will rise At atmospheric pres sure the ignition temperature is approximately 1000 F but air H2 mixtures at pressures of 0 2 to 0 5 Atm can be ignited at temperatures as low as 650 F Hydrogen mixtures burn with a colorless flame 4 The total volume of liquid hydrogen in the heat exchanger is about 2 The target cells and their associated plumbing hold an additional 3 4 l Thus the total volume of hydrogen in the target is approximately 5 4 1 The volume changes between the liquid state and gas at STP by a
146. d rather than when depressed It would be nice in the future to have relays 3 and 5 also activated by an open limit switch condition and deactivated when the switch is closed This way the 12V could be off to one of the switches and the doors would stop moving As it is now a broken wire short while the doors are closing could cause the doors to continue moving risking possible damage The status of the limit switches is readout via an ADC in VME crate 4 If the switches are closed a 4V is seen at the ADC input This is effected via a voltage splitter of 3 6 resistors The readouts are plugged in via telephone jacks PJ6 and PJ7 A temporary fix has been put in place which sends the signals through a capacitor first to block voltage spikes going into the ADC These voltage spikes caused the ADC to trip off line which can only be fixed by resetting the VME crate The operation of the carbon doors is done via a GUI style control panel This panel is located under the detector screen of the hadron arm FPP Carbon Doors The 3 4 carbon door has been disconnected at the 90V power supply and is not implemented in the software GUI This door had what may have been some sliding problems Since it may take a great deal of force to remove this door if it should jam it will need to be tested so it can be removed easily if it should jam The normal operating procedure with the GUI is to first make sure all the 90V power is off to e
147. d the aerogel panels in place This fishnet frame is secured by screws and is easily removed without disturbing the aerogel panels or requiring restringing The bottom of the tray is formed out of a single layer of carbon fiber epoxy skin 0 127 mm thick and a layer of aluminized mylar of equal thickness Externally it is covered by a single layer of Tedlar film to assure integrity from light penetration further environmental isolation is provided by two parallel strips of rubber gasket seals enclosing the circumference of the tray and containing the feed through spacers for the retaining bolts The tray is equipped with SMA type fiber optic feed through connectors for the gain and timing monitor system which utilizes fiber optic cables Each fiber illuminates two adjacent PMTs except the last PMT on either side 13T and 13B in figure 5 17 which have their own dedicated fiber The light is generated in a gas plasma discharge unit and duplicates the spectrum expected from Cerenkov radiation In addition the fibers terminate beneath the silica aerogel thus the light reaching the PMTs will have the absorption characteristics of real Cerenkov light produced in the aerogel radiator Due to the nature of Cherenkovdetectors where few photoelectrons PEs are emit ted by the photocathodes in the PMTs any extraneous light entering the enclosure is very troublesome As a result of the small number of PEs expected the PMTs operate either near to
148. d to achieve the desired field If the NMR gaussmeter is not locked a backup Hall Probe is used until the NMR locks The user should just stand back and let it work What follows are instructions for using the NMR gaussmeter in situations where Autopilot doesn t work or some special supplemental measurements are required In principle it is possible to make the field measurements using the SEARCH mode in the Teslameter In this mode you select a probe and the meter explores the whole field range of the probe until it finds and locks on the resonant signal indicating that it has a field measurement A lock is indicated on the controls display by positive field values This has the advantage of simplicity but in practice can be time consuming and doesn t always work The problem being in situations where there is a lot of noise mixed in with the signal the circuitry has problems distinguishing the signal from the noise and gets lost before it ever finds a lock The problem is exacerbated when the field being measured is at the high end of the probe s range In this case the search starts at the low end and keeps getting hung up on the noise and never gets to the field range of interest The solution to this problem is to tell the device approximately what field it s looking for and use the AUTO mode to find the lock In the procedure below that is what we will be doing In any case for gap probes group 0 you must energize and adjust
149. e NMR should lock when you get into the vicinity of the desired field If you re worried anyway and want to watch the field change push SEARCH The NMR will search over the full range of the probe rather than just in the vicinity of the desired field The NMR should lock in a minute or two If the NMR is not locked and the current is going in the wrong direction This can happen if you ask for a new field before you reach a stable setting you must push SEARCH The NMR will search over the full range of the probe rather than just in the vicinity of the desired field The NMR should lock in a minute or two and the software will correct the current setting appropriately but slowly If the NMR doesn t lock you may have to ask for a field value appropriate for the present current 1 1 x 107 T Amp The NMR will only search in the limited region of the requested field and should find a lock more easily After getting the lock let things settle in for a few minutes and then ask for the field you want again In extreme cases you may have to nurse it through the transition by asking for multiple small increments If you ask for a change of less than 5 the NMR should not lose its lock To shut down Set FieldSet to 18 Let current run down to just over 100 Amps Then push stop on Dipole control screen Problems Explanation Action NMR not locked but Normal operation for Wait see above current is changing in large fie
150. e was not blank it becomes blank then wait for 1 minute and it returns to grey the scanner is then operational If the ioc is not dead you can also reboot it by software through the network hac gt rlogin arcioc gt reboot the rlogin connection is then broken by the reboot 10 98 The hard reboot green button labelled ARC is temporarily connected also to another VME crate e p energy measurement use it only if e p is not running 2 4 8 Details on disk space check scanners Run the quota UNIX command under gougnaud arc2 ARC Filesystem usage quota limit timeleft files quota limit timeleft u home 119308 512000 512000 924 1 1 Do it several times sometimes the answer is crazy In the above example you have about 400Mo free a scan file of scanners 1 to 4 energy measurement occupies about 1Mo when unzipped and 300Ko when zipped so you have room for 400 unzipped files or 1200 zipped files 2 4 9 Details on running a scan On the MEDM screen load datal234 as Command File Content of data1234 1 P 5 2 P 5 3 P 5 4 P 5 1 P 5 2 P 5 3 P 5 4 P 5 means use scanners 1 to 4 do first the 4 forward pass and then the 4 backward ones to give the wires time to cool down at 5 turns s 12 500 mm s Warning lower velocity may cause the wire to melt An error message will be edited if the velocity is outside 0 6 1 t s P is for PMT readout S for Secondary emission for scann
151. e a good reading strongly fasten the coupler 2 Note the encoder is absolute over 64 turns with 4096 units per turn So starting from 0 and turning it clockwise one should read 4096 after one turn 8192 after two turns up to 262143 just one puls before 64 turns 0 again one puls after 4096 after one turn 2 4 17 De tails on scanner expert task The path of the expert task MEDM file is given in the first subsection Use this task to set the encoder in any position between the limit switches to dismount the wire cartridge to set the encoder Call this task in MEDM You get a small window with a blue button Left click on it it gives you a choice between the 4 ARC scanners Select the scanner you are interested in then release the left mouse button An Expert task bigger window appears In this new window left click on the blue button click to initialize Then the designated scanner name is displayed on the top of the window Edit the motion you want in the First goal input field This is an ABSOLUTE position i e not an increment from an origin which can be arbitrary in unit of motor micro step 2000 microstep 1 turn 4096 encoder units so one has 2 048 encoder units per microstep push on Pos gt 0 to set to zero the Motor current position register The current scanner position becomes the new origin of the motor positions once the motor position is entered push
152. e beam exit point to 8 83 3 47 in from the beam entrance point on one side and a similar window on the other side of the beam For future considerations e g using a third arm or sliding seal the width of the window on the middle ring was actually constructed to be 17 78 cm 7 in Stress Analysis of the Middle Ring Since the middle ring has an extensive cut across the midplane on both sides as well as entrance and exit holes and loaded with about 25 000 lbs calculations of the stresses and deformation of the midplane support area of the middle ring and deflection of the window opening were made using the finite element analysis code ANSYS The work was conducted by a graduate student in the Department of Civil Engineering at the University of Virginia and a REU student A scaled down model of the middle ring was constructed and then tested by applying forces to it using the Materials Testing Service of the Department of Transportation at the University ANSYS was first checked by comparing calculations of the test model deflections to the actual data Agreement was within 10 Results of ANSYS for the target chamber showed that the maximum deflection of the opening of the window in the middle ring varied from 0 007 in to 0 015 in depending on how the middle ring was loaded This was decided to be a safe limit In the final design several movable 7 in long 2 in diameter aluminum support rods are placed in the window for added support In add
153. e on the PMTs is 2 950 V This is a near maximum rated voltage and it has been shown to combine high efficiency good P V ratio and long PMT life The overall gain of the PMT is not maximum as is measured by BURLE since the dynode chain of the 13 dynodes 2nd dynode to 14th dynode is kept at 2 600 V equivalent with the original 300 kQ resistor value between Cathode and Ist dynode However the gain is more than sufficient to separate the one PE from the pedestal of all ADCs we have used so far It should not be necessary to increase the voltage above the recommended one 5 5 5 Handling Considerations It is generally not advised to open up the counter if the persons involved are not thor oughly familiar with the assembly and specific component function Routine operation does not require any hands on modifications to the detector as along as the following operating principles are followed Installation and Removal of PMTs replacement of a PMT or repairs of the electronic amplification chain can be accomplished by removal of that specific PMT Base combination Turn the HV off on all PMTs and remove the rubber hood covering the base and housing interface region Now remove the three small screws attaching the base to the integral housing Note that the base can only be secured to the housing in one specific orientation Carefully slide out the base with the PMT and p metal shield mounted as one unit Remove the elastomeric ring positioned be
154. e phone E Mail Evaristo Cisbani 39 6 49902847 Cisbani vaxsan iss infn it Franco Garibaldi 39 6 49902243 Garibaldi Vaxsan iss infn it Stefano Colilli 39 6 49902832 Colilli vaxsan iss infn it Maurizio Lucentini 39 6 49902232 Lucentini vaxsan iss infn it Fabio Santavenere 39 6 49902232 Santavenere vaxsan iss infn it Massimo Gricia 39 6 49902232 Gricia vaxsan iss infn it Mauro Iodice 39 6 49902235 Mauro Gvaxsan iss infn it Guido Urciuoli 39 6 4457165 Urciuoli vaxsan iss infn it Salvatore Frullani 39 6 49902234 Frullani vaxsan iss infn it Roberto Perrino 39 832 320504 Perrino Le infn it Antonio Leone 39 832 320504 Leone Le infn it CHAPTER 3 TARGETS HEMME CRATE COUNTING ROOM engine OONN EJ COOLER POWER SUPPLY MODULE Figure 3 8 Layout of the slow control system 89 CHAPTER 3 TARGETS SMALL SIGNALS GENERAL LAYOUT Tachometer Display and 4 20 output Pressure Display and 4 20mA output Flowmeter Display 48 Flowmeter 420 Output OptoCouplers 4 Encoder Displays Interface 4 Level Adapter Motor Drivers EN 0 57 to 4 201044 2 Rack Zone eS m Figure 3 9 Signals layout CHAPTER 3 TARGETS 91 The phone at Jefferson Lab is x5794 In absence of the forementioned people please contact Meme Liang Arun Saha Ed Folts James Proffitt or Mark Stevens all of them at Cebaf gov 3 4 6 Safety Assessments The following potential hazards have been
155. e position inside the magnet Zm where you want to measure the field inside the 1500mm 4 1500mm range The software will compute the probe position Zd depending on the NMR probe selected automatic or manual selection You have to define 3 regions where the steps may differ Edit the fields STARTING Zm region 1 NUMBER OF STEPS and STEP SIZE then the intermediate position Zm is computed automatically by the software as a result of the above input region 2 NUMBER OF STEPS and STEP SIZE then the intermediate position Zm is computed as above region 3 NUMBER OF STEPS and STEP SIZE then the final position Zm is computed as above Then push Start It takes about 20s per point unless there is a lock problem where it can take up to 100s timeout If the NMR does not lock even far from the ends push Stop Map here use the DAC 5 lock mode see detail on NMR lock and start a new map Note after Stop Map here the incomplete map can still be saved Use Stop in case of emergency and then reboot the VME see detail The measured fields are displayed on the screen as a function of Zm The sequence is a measurement at Zm 0 called Bref1 the list of measurement you entered a measurement at Zm 0 called Bref2 When done save the data by pushing Save The file is numbered automatically the name is of the type mapping_nnn data where nnn stands for the map number The directory is given by the MEDM sc
156. e switch is in front of Power Supply Module at the bottom of left rack 4 Turn the remote manual knob to manual position the knob is in front of Motor Drive module at the center of left rack 5 Select the direction opposite to the one which caused the alarm the switches are in front of Motor Drive Module 6 Handle the joystick carefully get ready to switch off the manual motor power supply if anything goes wrong T As soon as the trouble has been fixed restore the security turning on the switch on the left side of the left rack the corresponding red light must be on This is the same switch of step number 2 If you forget this step the security microswitches will be disabled and you risk serious damage to the movement system Emergency Use of Movement System with the Cranks If it is not possible for any reason to use the motors to move the target there is the chance of moving it manually using some cranks This procedure can be performed ONLY BY AUTHORIZED PERSONNEL because of the RISKS TO THE TARGET The procedure is the following e Remove the motors from their seats e Take the two cranks which are in the wooden box number 1 near the wall in Hall e Mount the cranks instead of the motors e If the encoders are working one can position the target by reading the encoder values on the display and matching the values with the look up table which is in the manual e If encoders are not working the alignme
157. ection 1C08 BPM IPM1C08 93 42465 Quad MQA1COS 93 05000 BC MBC1C08H 92 70685 Sext 5 1 08 92 40500 TV View ITV1C08 92 21180 Ion Pump VIP1C08 1CB5 Dipole 3m MBA1C05 90 30000 1C09 Quad MQA1CO9 87 85000 BC MBC1C09H 87 50685 Sext MSA1C09 87 20500 1CB6 Dipole 3m MBA1C06 85 10000 1C10 BPM IPM1C10 83 02465 Quad 10 82 65000 BC MBC1C10H 82 30685 CHAPTER 2 BEAMLINE 23 Sext 5 1 10 82 00500 Ion Pump VIP1C10 81 81180 1CB7 Dipole 3m 1 07 79 90000 1 11 Quad MQAICII 1 1 45000 BC MBCIC11V 77 10685 Sext MSA1C11 76 80500 Covectron VTCICII1 16 61180 1CB8 Dipole 3m MBA1C08 74 70000 1C12 BPM IPM1C12 72 62465 Quad MQAIC12 72 25000 BC MBC1C12H 71 90685 Sext 5 1 12 71 60500 Ion Pump VIP1C12 71 41180 1CB9 Dipole 3m MBA1C09 69 50000 1013 Quad MQAIC13 67 05000 BC MBCI1C13V 66 70685 Sext MSA1C13 66 40500 1CB10 Dipole 3m MBA1C10 64 30000 1C14 BPM IPM1C14 62 22465 Quad MQA1C14 61 85000 BC MBC1C14H 61 50685 Sext 5 1 14 61 20500 Ion Pump VIP1C14 61 01180 1CB11 Dipole 3m 11 59 10000 1 15 Valve VBV1C15 Rough Pump VRV1C15 Quad 15 56 65000 BC MBCI1C15V 56 30685 Sect 5 1 15 56 00500 1CB12 Dipole 3m 1 12 53 90000 1616 Ion Pump VIP1C16 Convectron 16 BPM 6 51 82465 Quad 16 51 45000 BC MBC1C16H 51 10685 Valve VBV1C16 Shield Wall Hall A SHIELD WALL entrance surface 50 70700 SHIELD WALL exit surface 49 651 1C17 Viewer ITV1
158. ed equipment that they control If necessary hallasc9 can be rebooted by pressing the RESET push button located in the IOC front panel Such operation does not have any effect on the Hall A cryogenics distribution itself hallasc9 does not control any hardware it is simply a signal repeater If a magnet cryogenics problem develops in Hall A the Hall A on call technical staff should be notified The controls layout of each High Resolution Spectrometer HRS is similar each consists of three IOCs which monitor and control the detector package infrastructure general spectrometer functions and spectrometer motion In the case of the hadron HRS these IOCs are hallasc4 hallasc16 and hallasc7 Hallasc4 and hallasc16 are lo cated inside the detector hut Hallasc4 is in the second floor of the detector electronics racks while hallasc16 is located under the Box Beam supporting the detectors and de tector electronics Access to 16 is through a manhole located at the back of the detector hut The IOC in charge of the hadron HRS motion is located right at the back of the dipole power supplies level In the case of the electron HRS the IOCs are hallasc11 hallasc14 and 18 respectively Their location is similar to their hadron spectrometer counterparts The tasks assigned to IOCs hallasc7 and 18 are well defined and unique spectrometer motion Hallasc4 monitors controls the Vertical Drift Chambers VDCs Hi
159. either of the two buttons labeled LEFT BANK and RIGHT BANK The lit LED above the button you pressed will change from yellow READY to green RUN You will most likely need to reset the Low Supply Pressure shutdown at this point The four FPP straw chambers are connected in parallel to the gas system see Figure 5 29 The FPP chambers are also in parallel with the VDC chambers All gas connections are made using POLYFLO tubing and TJNAF specified connectors The chamber volumes range from approximately 120 to 220 Gas pressure in the chambers is typically a few Torr above atmospheric pressure The gas flow through the chambers may be independently varied and is typically set to 7 hr leading to a replacement of the chamber volumes about every 15 30 hours Gas is exhausted from the FPP chambers through a bubbler containing lt 1 mm of mineral oil A typical chamber leakage rate at this flow rate is 25 50 96 The flow rate of 7 hr when combined with the leak rate of lt 3 hr results in a complete exchange of gas in the chambers roughly every 1 2 days At this level of consumption a full gas bottle connected to the FPP system lasts approximately 10 days When a bottle is nearing empty 90 it should be changed since there may be heavy contaminants in the gas Gas bottles may only be changed by authorized personnel Gas handling Procedures 1 Typically gas is continually flowing though the chambers If at all pos
160. ement before and after data must be very close lt 0 1 C difference for the tempera tures of a given probe j0 1A for the currents and 10 5 for the field plots the blue curves are from forward pass yellow ones for backward pass the top plot gives the probe velocity in m s as function of its position in mm The forward velocity should be 0 6m s everywhere except at the center where it is reduced to 0 06m s The backward velocity plot should be the mirror image of the forward ons 0 6 and 0 06m s the bottom plot gives the coil voltage after gain in V as function of the probe position in mm It should be a null voltage everywhere except a set of oscillation at the center The backward voltage plot should be the mirror image of the forward one V gt V See PDI saturation above to zoom a MEDM plot see Details on gain adjustment scanners above 2 4 26 Details on integral data save The procedure to save the datafile from arc integral adl is the sane as for the scan ners see Details on file save scanners above with an independent integral run number The file name will be of the type integral nnn data stored on pascall in gougnaud EPICS integral As pascall disk is not mounted on the CUE use ftp or rcp to move the file to the CUE The size of a file is 207Ko The data file is made of a header containing basically the before and after data the forward integral data the bac
161. entiometers within the boxes adjustment information is given in the FPP logbooks The low current supplies are Hewlett Packard 6111A supplies The 6111As can provide up to 1 A for voltage from 0 to 20 V The supplies are currently hooked up through the rear panel to a DAC in the data acquisition panel front panel controls on the supplies are disabled except for the on off switch The voltage is controlled through an EPICS FPP threshold window that is accessed through the Hall A hadron spectrometer detectors menus The high current supplies are not computer controlled supplies are mounted in the detector stack The multiplexed logical signals from the chambers have amplitudes smaller than ECL levels to prevent noise at the chamber These signals are fed to level shifter boards see Figure 5 28 located in the FPP rack on the lower electronics level of the detector stack on the beam right side A high current 5 V power supply for the level shifter CHAPTER 5 HRS DETECTORS 180 CI I 9 1500p 3Kv Figure 5 26 Circuit diagram for the amplifier discriminator section of the readout board zb ZN cw OUT 5 AAA c105 lt J2 0 1 00 8 2 1 10109 R71 R68 510 ci 510 C101 ina 0 1 R70 453 R72 453 04 1 ouTL 4 NYN 0 1 n 92 UAM 0255 0072 Figure 5 27 Circuit diagram for the logical multiplexing section of the readout board
162. er is off at the power disconnect switch ensure spectrometer entrance window guards are removed ensure target window guards are removed CVS Id hallacryo tex v 1 2 2003 06 05 23 29 59 gen Exp A 2 Post Beam Checklist for Maintenance Period Revised 2 22 99 This checklist will be completed prior to every restricted access to Hall A during which maintenance is performed People checking Spectrometers APPENDIX A HALL CHECKLIST 233 NOTE LOOK FOR RADIATION AREA SIGN and OBEY Install yellow covers on inlets to spectrometers Target _ NOTE LOOK FOR RADIATION AREA SIGN and OBEY _ A Install protective shields over vacuum windows if Cryo target is installed Power supplies from a computer console Electron _ set current to 0 amps by remote control on Q1 current to 0 amps by remote control on Q2 current to 0 amps by remote control on Q3 TR set current to 0 amps by remote control on Dipole Hadron TER set current to 0 amps by remote control on Q1 current to 0 amps by remote control on Q2 current to 0 amps by remote control on Q3 current to 0 amps by remote control on Dipole Entrance beam tube _ NOTE LOOK FOR RADIATION AREA SIGN and OBEY Exit beam tube _ NOTE LOOK FOR RADIATION AREA SIGN and OBEY Dump _ NOTE LOOK FOR RADIATION AREA SIGN OBEY _ Inspect visible areas for water leaks Hall NOTE LOOK FOR RA
163. ers 5 and 6 The file is in gougnaud arc2 ARC In pulsed mode 60Hz use a velocity of 0 3 turn s You need to edit a special file setting this velocity On the MEDM screen update CW 60Hz beam current and DISPersive ACHROmatic for the record Push START when ready you can follow the operations by looking at running command the line of the Command file currently executed the cursor position of the scanners CHAPTER 2 BEAMLINE 39 voltage versus position plot The location of the 6 scanners on the MEDM window is the following 1 2 73 4 35356 The forward plot is green the backward one is red In case of saturation redo the scan with lower gain see details below The only peak used for energy measurement is the rightmost one H profile produced by the V wire focus on this peak to adjust the gain the 2 other peaks may saturate the names on the top of the plots are the CEBAF device names of the scanners WARNING operating at too high a beam current or too small a velocity may cause the wire to melt with no opportunity to repare it before the next shutdown The total travel time is about 15 s per scanner During the travel have a look at the beam current If the beam trips inquire why correct if it was caused by the scan set masks and redo the scan see details on trips below Save the data see details below Print the MEDM window see details below you can plot the profile see detai
164. experiments are running Access is restricted only in the sense that the hall is not 10 CHAPTER 1 INTRODUCTION 11 open to the general public 1 2 2 Sweep Sweep is the state of the PSS when delivery of beam and or RF power is not permit ted and access is limited to the Jefferson Lab personnel conducting the sweep operation The hall s entrance gates are closed from the inside to ensure that no one can enter be hind the person conducting the sweep During the sweep an Assigned Radiation Monitor or ARM systematically searches the hall to verify the absence of people and to arm the run safe boxes The ARM posts a guard at the entrance to the hall as another method of ensuring that no one enters after him When the Assigned Radiation Monitor is ready to perform a sweep the Machine Control Center or MCC must first place the hall in the Sweep state The Personnel Safety System will read Sweep In Progress Once the hall is placed in the sweep state the sweep monitors enter the first gate to the hall making sure it locks behind them The ARM then notifies the MCC that he is ready to begin the sweep The MCC communicates with the sweep monitors via intercom and video camera Using the video camera the MCC makes sure both sweep monitors are wearing the proper dosimetry At this point the ARM also indicates that he is in possession of the key needed to arm the Run Safe boxes placed throughout the hall Having confirmed that the dosimet
165. extent its acceptance Operating limits imposed on the quads are as follows 1850A for Q2 and Q3 and 3250A for 01 All three quadrupoles for the HRS spectrometer are warm iron superconducting magnets The soft iron around the superconducting coil enhances the field at the coil center and reduces stray fields The basic parameters for the first quadrupole Q1 are an effective length of 0 9 m useful aperture of 0 3 m and a field gradient of 9 5 T m To achieve the lowest possible angle setting of the HRS spectrometer with respect to the beam line the incident electron beam passes through a notch in the outer yoke of Q1 CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 112 when the spectrometer is at its smallest angle of 12 5 The other two quadrupoles Q2 and Q3 are essentially identical with an effective magnetic length of about 1 8 meter a useful aperture of 0 6 m and a field gradient of 3 5 T m The maximum operating currents assuming a 4 GeV c momentum particle for the quadrupoles are about 3000 A 1700 A and 1600 A for Q1 Q2 and Q3 respectively This will render pole field values of 1 2 1 0 and 1 0 T respectively The energy stored in the quadrupole fields is sufficient to cause an unrecoverable quench if all the energy stored is dumped into the magnets Therefore a quench protection circuit is incorporated However a quench can only happen if the cryomagnets have a helium level below the coil 60 during operation The operating
166. f which will be described in sections below The trigger management software is described in the Trigger chapter 7 1 1 General Computer Information In the counting room we have various computers for DAQ analysis and controls The controls subnet which includes the hac computer among others is the responsibility of J Gomez and is documented in Chapter 6 The DAQ computer s names are denoted adaqXN where X s is SunOS X h is HP UX and X l is for Linux PC adaqs1 is the Compton DAQ computer and is normally reserved by the Compton group adaqs2 1 CVS revision Id daq tex v 1 3 2003 06 06 15 38 43 gen Exp 2 Authors R Michaels mailto rom jlab org 216 CHAPTER 7 DATA ACQUISITION AND TRIGGER 217 and s3 are for running the spectrometer DAQ or doing online analysis adaqh2 h3 and h4 are for running the older version 1 4 of CODA still used by some setups adaql1 and 12 are relatively fast Linux PCs available for analysis and are administered by Ole Hansen To reboot the Suns login as adaq and type reboot On HP s adaqh2 4 you cannot reboot but must shutdown For both HPs and Suns here is how to shutdown Login as adaq and type shutdown wait several minutes until the screen indicates it s safe on Suns it goes black and on HPs it will say it s safe then turn off power To reboot the Linux machines first hit Ctrl Alt F1 to switch to a text console then hit Ctrl Alt Del to reboot If power fails fo
167. factor of about 800 Thus filling the target would require about 4 300 STP l of hydrogen The hydrogen target is connected to a 1 000 Gallon about 3 800 recovery tank The normal running condition for hydrogen is 26 PSIA So the total amount needed to fill the target and the tank is about 10 900 STP l For deuterium the target is about 4 300 STP The normal running condition for deuterium is 22 PSIA So the total volume needed to fill the tank is about 5 600 1 The total to fill both the target and the tank is about 9 900 STP J The Hall A inventory of hydrogen and deuterium gas is stored outside the Hall A gas shed adjacent to the counting house The current inventory is two A size cylinders of hydrogen 6 800 STP each and four A size cylinders of deuterium 5 000 STP each One bottle of hydrogen and one deuterium bottle will be kept in the Hall in order to fill the targets These bottles will be placed in a gas rack behind the gas panels The basic idea behind safe handling of any flammable or explosive gas is to eliminate oxygen required for burning and to prevent exposure to any energy source that could cause ignition In the Hall A environment the most likely source of oxygen is of course the atmosphere and the most likely ignition sources are from electrical equipment 3 CVS revision Id cryo c safety tex v 1 3 2003 06 06 17 11 53 gen Exp CHAPTER 3 TARGETS 71 Electrical Installation Hall A contains a lot of electrica
168. figure 4 13 It consists of a plate of roughly 14 cm x 20 cm containing 49 holes positioned in a regular 7x7 pattern This slit is made out of 5 mm thick tungsten The holes have a diameter of 2 mm except for the central one and one positioned off diagonal which have a diameter of 4 mm The horizontal distance between the holes is 12 5 mm while the vertical distance is 25 0 mm To get the latest information on the dimensions and locations of the collimators see the Hall A homepage on the web 4 3 1 Authorized Personnel E Folts x 1857 mechanical and vacuum systems J Gomez x7498 computer controls and electrical systems 4 3 2 Safety Assessment The collimator boxes form part of the vacuum system for each spectrometer All hazards identified in section spectrometer vacuum section applies to the collimator box as well In addition safe access to the top of the collimator boxes is needed during manual operation of the box as outlined below Due to the proximity of the collimator boxes OVS revision Id slit tex v 1 3 2003 06 06 16 13 37 gen Exp Authors J LeRose mailto lerose jlab org Thttp hallaweb jlab org CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 129 Linear bearing behind it is the _ ball screw A Coli a Vacuum throughput Box Open Box Closed Figure 4 12 Schematic layout of the collimator box CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS Sieve Slit o t diam 4mm 25 mm f a
169. for each channel the one shot width is fine tuned by the use of high precision resistors in an RC circuit these resistors are mounted in sockets so as to be easily replaced if the need arises An OR circuit then combines eight individual straw outputs into a single electronics channel Internally within the Faraday cages the high voltage is distributed to stacks of high voltage test pulser boards through which it is connected to each straw via a 1 MQ 1 4 watt resistor The readout cards require a high current low voltage power supply and a low current CHAPTER 5 HRS DETECTORS 179 2 1M R1 X J2 STRW 1500 3KV 30 1K Jl S1G AN 9 R3 X 357 R2 X J1 RET x channel Gilman Straw Termination RUTGERS UNIVERSITY Department of Physics and Astronomy Figure 5 25 Circuit diagram for the high voltage termination board low voltage power supply for a threshold level The readout electronics are mounted on the chamber shielded within Faraday cages The high current power supplies were built by the Rutgers University Department of Physics amp Astronomy Electronics Shop These supplies are set to provide sufficient current at 5 V for the boards to which they are hooked up No adjustments except for turning the supplies on off should be needed in normal operation There are voltage setting current limiting and overvoltage protection pot
170. front panel switch if the radiator will not be used for a long time and should be turned off if work is to be done on the radiator This deactivates the limit switches and the linear encoder but does not affect positioning Additional hard stops should be installed as a safety measure The Hall A technical staff checklist done as part of preparations for closing the Hall for beam includes checking the radiator position the status of the control box and the installation of hard stops 2 7 4 Special Instructions Care must be taken in case any removal or disassembly of the radiator system is needed Disconnecting the stepper motor from the motor driver while power is on can damage the motor motor driver and VME44 board The Cu targets will certainly be activated in the course of an experiment Therefore only remove the Cu target the target ladder and or the whole radiator system in the presence of a Radcon officer Ron Gilman should be informed in case of any problems with the radiator Except for normal operations of the radiator any work on the system hardware requires that RadCon has concurred in the work and either Ron Gilman or David Meekins is present CHAPTER 2 BEAMLINE 65 2 8 Meller Polarimeter 19 2 8 1 Purpose and Layout The Hall A beam line is equipped with a Maller polarimeter whose purpose is to measure the polarization of the electron beam delivered to the hall I 20 Coils Quad 1 Quad 2 Quad3 1
171. ge also results in a postscript file for printing and there is a histogram file dplot his which one can view in PAW Appendix A Hall Checklist A 1 Pre Beam and Cryo Target Checklist Cryo Target Pre Beam Checklist Date time _______ Last revised 3 6 98 This checklist will be completed after every restricted access to Hall A during which maintenance is performed People checking list se ce ee ea ee Electron Arm Spectrometers correct angle not to be used for calculations correct pointing _________ not to be used for calculations collimator operation at positions check spectrometer for obstructions to movement _ check intergen bottles for correct pressure insure that 15 degree stop pin is installed Vacuum _ blower on at controls under spectrometer A turbo on at turbo controller in rack 1H71B01 pump valves open at valve controller in rack 1H71B01 channel 2 gages read 0 millitorr roughing valve closed at rack 1H71B01 channel 4 cold cathode gages on at gage in rack 01 cold cathode 5x10 5 actual cold cathode reading ________ entrance amp exit vacuum windows functional magnet controls Q1 Q1 full of liquid 80 actual APPENDIX A HALL CHECKLIST 228 A open lead flows on Q1 to 80 slm as read from rack Q171Q A actual lead flows B camera on and focused D1 A D
172. gger for forward pass Zd is given by the display at the top of the rack or by the master screen OUT The relationship between Zm Zp and Zd is Zd Zm Zp C where C is a constant given in magnet dir C 1604 000 nomin Example of use to have the probe center at the dipole center one must set Zd 1604 000mm set Zm 0 and Zp 0 in the above formula and solve for Zd The integral measurement sequence is the following from the current position a priori arbitrary move the probe upstream up to a limit optic switch move downstream by a few mm to cross the encoder index encoder initialization move to the central position to measure the central field by NMR the system checks if the NMR locks and if the reading is stable it will be the before field move back to upstream position move to downstream position while integrating the flux through the coil system this measurement will be called the forward integral duration 7s move back to upstream position while integrating the flux through the coil system this measurement will be called the backward integral duration 7s move to the central position to measure the central field by NMR the system checks if the NMR locks and if the reading is stable it will be the after field In addition to the central field 4 probe temperatures a local excitation current measurement the setting of the dipoles P S the readback of the dipoles P S and the probe position
173. gh Voltages HV discriminator threshold levels and the low voltage power supplies for the discriminator cards as well as the Focal Plane Polarimeter FPP tracking cham ber s HVs discriminator levels and low voltage power supplies Hallasc4 also controls the operation of the FPP carbon doors as well as monitoring the gas flow to the FPP tracking chambers and VDCs In the case of the electron HRS the corresponding IOC hallasc11 monitors controls similar quantities for the VDCs only there is no FPP system The general spectrometer infrastructure IOCs hallasc14 and hallasc16 moni tor control magnets power supplies field probes hardware interlock systems and power leads cryogenic cooling collimator motion magnet spectrometer vacuum and spectrom eter horizontal vertical angles If a problem arises all these IOCs can be hardware reset CHAPTER 6 SLOW CONTROLS 213 from the Hall A Counting House through the green buttons panel located in the middle room There is an extra IOC hallasc22 located on the second floor of the electron HRS detector electronics racks inside the detector hut This IOC monitors and controls through a private network various high voltage power supplies Two of these supplies are located in the electron HRS detector hut one in the hadron HRS detector hut and one along the beam line These power supplies are used by various systems like the spectrometer scintillator planes trigger gas Cerenkov and Aerogel counte
174. gized and a beeping sound will be heard CHAPTER 3 TARGETS 94 e Push the green button near the emergency red button The beeping sound will be turned off System shutdown The normal procedure e Go to the experimental hall e Close the program on the MacA shutdown the MacA e Move to the right side of the Right rack and push the red stop button of the right box the left box is not used The emergency procedure This procedure is really an EMERGENCY procedure do not use it for normal op eration Push the emergengy red button in front of the left rack if you are in the hall or the one in the counting room on the top of the computer monitor In order to restart the system follow the startup procedure described above Waterfall activating e Check that the slow control program is running on MacA and optional on MacB e Check if the pump is on and in case it isn t turn it on from the switch in front of the right rack or from the switch in front of Pump Command Module in the counting room e Increase the pump speed to desired value in the main window of MacA or MacB right side e Wait about 20 minutes to stabilize the water flow Empty target procedure From the counting house use the slide on the right of the main window of MacB to set the pump speed to minimum then switch off the pump by turning off the switch on the front panel of the pump Command Module which is located over the MacB monitor Or In the hall
175. h are mounted on the sides of the VDCs within the confines of the protective aluminum Faraday cage The chamber gas is a combination of argon Ar and flammable ethane C2H which is bubbled through alcohol Gas is routed from bottles located in the Hall A gas supply shed to gas supply control panels located on the main level of the space 3 OVS revision Id vdc tex v 1 3 2003 06 06 17 00 27 gen Exp Authors J Segal mailto segal jlab org CHAPTER 5 HRS DETECTORS 136 V2 Upper Chamber U2 nominal 45 particle trajectory Lower Chamber V1 SIDE VIEW Ul TOP VIEW WY nominal 45 particle trajectory 09 09 0 288 m 2118 m Figure 5 1 Relative VDC geometry CHAPTER 5 HRS DETECTORS 137 nominal 45 particle trajectory Figure 5 2 Relative VDC geometry CHAPTER 5 HRS DETECTORS 138 frames in the detector huts As charged particles pass through the chamber gas in the VDCs they produce ionization This ionization drifts along the electric field lines defined by the high voltage planes and the signal wires Ionization is collected in the form of analog pulses on the signal wires The pulses are then amplified discriminated and used to start multihit TDCs which are subsequently stopped by the overall event trigger The TDCs are read out by the CODA acquisition software The data are histogrammed online by the DHIST software In depth offline data analysis requires the ESPA
176. h white numbers give readbacks of the magnetic fields and currents in each magnet The black fields also give readbacks however in this case if the text appears green those parameters are OK while if they are red then that parameter is out of tolerance and may indicate a fault condition For example if the helium level goes below a certain point the magnet will be automatically turned off In some cases it may be desirable to monitor certain critical quantities on a strip chart e g Magnet settings A strip chart tool is available for this purpose from the bottom of the main control screen To set the spectrometers for a given value of central momentum P0 type the desired PO value into the yellow PO SET box and hit return The magnets will be automatically set to the correct values All green numbers in the PO column indicates that the desired field or current settings have been reached Caution Re dipoles in general 3 OVS revision Id nmr 1999 tex v 1 1 2003 06 06 15 44 08 gen Exp Authors J LeRose mailto lerose jlab org CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 118 MUX 2031 Purcell Gap Probes Group 1 Spares Slow Controls Spare Channels Spares Vacuum Gap Probes Group 0 Figure 4 7 Basic layout of NMR system it s a bad idea to assume that at the first instant that the PO display turns green that the desired field has been reached and you can start taking data Stable field is
177. hat cannot be reached unless opening the side panel of the right rack The gas system This system is a potential hazard only if hydrogen is used The volume is 10 liters The pressure is 1 02 atm The target cell for gas tightening has been tested up to 2 bars The gas transport tubes are made of stainless steel 6 mm in diameter The electro valves are anti deflagrant according to the USA regulations working at low voltage 24V AC All the power supplies for this section are kept separate in a different rack The default value for the valves which is at the released position if power supply fails is closed Regulating the pressure on the gas cylinder to 0 2 atm avoids the pressure in the target cell overriding this value even in the case of valve failure Both the manual valve and the remote valve control require the operator to keep pressing the button either on the front panel of the right rack or by using the mouse button on the corresponding icon from the computer in order to keep the valve open If the button is released the valve will go back to the default value i e closed Any leakage from the cell would be immediately detected by the scattering chamber vacuum measuring system Leakages outside of the scattering chamber would spill in the surrounding atmosphere in the Hall However because of the small amount due to small CHAPTER 3 TARGETS 92 gas overpressure this should not represent a potential hazard for the people work
178. he DM 2401 Keyboard module press the MODE switch until the FLOW LED illuminates The window value for channel 1 will begin to flash Select the channel you wish to alter by pressing the STEP button until the window value of the desired channel is flashing Press the UP or DOWN SET buttons to alter the value as desired Legal flow values are 0 0 100 0 sccm for channel 1 0 1000 sccm for channels 2 and 3 If the Red ON LED for the desired channel immediately to the right of the value window is not lit press the ON OFF button for that channel to illuminate this LED Repeat steps 6 8 as necessary to program all desired gas flows Return the DM 2401 to NO MODE as in step 3 Return the Auto Expert pressure control switch rear of mixer rack to AUTO Re Open valves MV201 202 203 if closed in step 1 Observe system flow and pressure control and verify that it is correct 5 8 7 Troubleshooting Things to Check Each of the following monitor points must report a nominal condition to the gas interlock panel in order for the logic to be made up and for gas flow to be enabled CHAPTER 5 HRS DETECTORS 207 Label Meaning Likely Remedy Sensor Low Pressure The seconeary e Check for a closed 3 pressure Note This channel will always indicate a fault after some other problem has caused the solenoid valves to close pressure of one or more of the mixer inlet gas supplies has dropped below the 45 psi threshold E
179. he hall status to Sweep The ARM will then sweep the hall verifying that everyone is out Following a successful sweep the MCC can move the hall through the Controlled Access and RF Permit states to the Beam Permit state While working in the hall you must observe all posted radiation areas Remember work inside a radiation area requires that you obtain an approved radiation permit You must also observe the two man rule and pay attention to the alarms 1 3 3 Access Requirements Normally only registered experimenters authorized contractors or sub contractors and Jefferson Lab employees may enter experimental areas In addition lab policy states that no one under eighteen years of age is allowed access to the experimental halls Lab visitors may work in the halls provided they have completed the full complement of training courses EH amp S Orientation ODH Rad Worker Training and any hall specific training the Hall A safety walk through They must also read sign any appropriate documentation typically the COO and ESAD for the current experiment and the Hall RWP In addition to the above undergraduate students must undergo a three month trial period During this period they may work in the hall provided that e Their work in the hall is directly supervised by a hall authorized buddy who CANNOT be an undergraduate e Either a JLab staff member or a fully trained user has supervisory responsibility for and is fully cognizant
180. hese are UNIX based workstations able to run various EPICS tools like the Motif based Display Editor Manager MEDM used by the operators for display and command of the various systems e Input Output Controllers IOC These are VME based crates containing a single board computer with the real time operating system VxWorks and various I O modules as well as interfaces to other I O busses like serial or GPIB e Boot Servers These are UNIX based workstations from which the IOCs load the various software components they need to perform their functions i e operating system database of signals to be monitored commanded controls algorithms and so on e Local Area Network LAN This is the communication path joining the IOCs OPIs and the Boot Servers Signal monitoring and command is performed by the IOCs At the heart of an IOC is a memory resident database describing each of the signals to be monitored and controlled by the IOC Each database entry record corresponds to a signal When a given record executes it accesses the appropriate I O module to retrieve update the signal value The origin of this record execution request can be local to the IOC i e another database record or remote i e operator intervention through an OPI or a record located in another IOC In all cases access to the record is by name and not by IOC location The general EPICS mechanism to access a record consists of broadcasting the record name in the network U
181. hin the aerogel material The requirement for segmentation in addition to supplementing the information on the individual particle position along the focal plane also couples well with the desir ability of increasing the active solid angle viewed by the PMTs in the counter Although the photon detection probability is not as directly proportional to the solid angle covered by PMTs as in the case of a diffusion box clearly the larger the effective coverage the higher the probability will be that a photon will end up on a PMT Given the divergence of the beam envelope incident on the aerogel and the diffusion of the light in the low region by the aerogel material an increase in the area covered by PMTs results in an increase in the number of photons detected As a result a total of 26 PMTs are used in the counter as shown in figure5 17 with minimal spacing between their jj metal shields 2 8 mm The total area covered by the PMT photocathode windows comprises 72 of the area of the counter opposite the planar parabolic mirrors A cross sectional schematic of the detector is shown in figure 5 18 clearly illustrating the planar parabolic design of the mirror surfaces and their relative orientation with respect to the PMTs and the 11 CVS revision Id aerogel tex v 1 4 2003 06 06 21 41 39 gen Exp 12 Authors G J Lolos mailto gjlolos jlab org CHAPTER 5 HRS DETECTORS 166 orientation of the counter relative to the central axis of the spec
182. hole system before opening and working on the system ONLY AUTHORIZED PERSONNEL are allowed to touch the signal lines The mechanical system There are no particular risks in touching the mechanisms except when the system is in motion In this case one has to beware of the cog wheel s movements by keeping his hands away for this reason it is FORBIDDEN to touch the moving system when motors are moving 3 4 7 Operating procedure All the operations are handled by computers Some of them can also be performed inde pendently by mechanical switches referred to as manually In the following the main window of the slow control program running on the MacA and or MacB display will be referred to simply as the main window Connection of MacB to MacA The MacA and MacB communicate through the Timbuktu package which imple ments the TCP IP protocols over an Ethernet dedicated line To make the connection following procedure outlined below CHAPTER 3 TARGETS 93 e Switch on the MacB computer energize the VME crate e Run Timbuktu on the MacB you can select it in the Apple top left menu e Open the connection selecting the CONTROL button after you entered the TCP IP number 129 57 188 20 e Give the username H20CEBAF and the password WATER The window that appears contains a carbon copy of the MacA screen the user in counting room can control all the operations of MacA by using the MacB mouse and key board as if the M
183. hors E Chudakov mailto gen jlab org CHAPTER 2 BEAMLINE 2 9 Compton Polarimeter 20 CV S revision Id compton tex v 1 3 2003 06 06 15 19 03 gen Exp Authors S Nanda mailto nanda jlab org 68 Chapter 3 Targets 3 1 Overview The physics program in Hall A utilizes a number of different target systems of varying complexity There is a set of cryogenic targets which currently operates with hydrogen and deuterium as target materials and will soon support both helium 3 and helium 4 A variety of solid targets is also provided 0 Carbon or Kapton are typical but other self supporting materials are available if need arises The combination of cryogenic targets and a few solid targets is the standard con figuration In addition there is a large program based on polarized helium 3 This is a special installation and hence is not available at the same time as the cryogenic target system Finally a waterfall target was used during the commissioning of the hall and is still available as a resource This system also requires a special installation Each of these systems is discussed in this chapter or in an appendix CVS revision Id overview tex v 1 3 2003 06 06 17 09 04 gen Exp 69 CHAPTER 3 TARGETS 70 3 2 Cryogenic Hydrogen and Deuterium Targets The Hall A cryogenic target system consists of two completely instrumented targets H and D In addition a third target loop is installed in the scattering
184. ibrating the optical properties of the spectrometers These are known as the collimator boxes These boxes are positioned between the scattering chamber and the first quadrupoles Q1 Each box is carefully aligned and rigidly attached to the entrance flange of the Q1 of the respective spectrom eter The boxes are part of the vacuum system of the spectrometer Inside each box a ladder is mounted which is guided by a linear bearing and moved up and down by a ball screw On this ladder 3 positions are available to insert collima tors Below this ladder a special valve is mounted that can isolate the vacuum in the spectrometer from the target system This valve should be activated when it is moved in front of the holes connecting the box with spectrometer and target chamber A schematic view of the collimator box is shown in Figure 4 12 Vacuum requirement is 10 Torr The material for the box is aluminum It is possi ble to open one side of the box so that collimators can be exchanged The reproducibility of collimator positions after moving the ladder and or after replacing a collimator is bet ter than 0 1 mm in horizontal and vertical direction The dimensions of the box are roughly height 175 cm width 35 cm and depth 15 cm The tolerance in the dimen sion of the 7 msr collimator hole is 0 5 mm in each direction The tolerance in the position of each of the sieve slit holes is 40 1 mm in each direction A typical sieve slit collimator is shown in
185. ical integrity of a closed system The chief hazard is that relief routes out of the system will become clogged with hydrogen ice making the behavior of the system during a warmup unpredictable However since we are using 15 K coolant while the hydrogen freezing point is about 13 8 K the hydrogen target should not get frozen The freezing point of deuterium is higher than that of hydrogen and higher than the temperature of the gas used for cooling 15 K There is a chance that the deuterium target can freeze The coolant flow through the three target heat exchangers is connected in parallel for the three target loops The entire target system will be run so that it represents a constant heat load on the ESR For instance the ESR will deliver a constant mass flow of helium cryogen at a constant temperature about 15 K and the coolant will be returned at an approximately constant but higher temperature usually about 20 K The targets are always temperature regulated by temperature controllers Also a high power heater will be in the PID loop to compensate any large temperature fluctua tions to keep the temperature constant In the unlikely event that the target temperature drops too low an alarm will sound and the target operator will turn down the corre sponding J T valve s 3 2 4 ODH The total volume of the targets is relatively small with the entire scattering chamber containing only 9 000 STP of target fluid when all three targets are f
186. icles The numbers indicate the sections 1 to 13 in the counter Each section is viewed by two PMTs one on the top T and one in the bottom B The labeling carries no significance other than identifying the PMTs during the testing phase as described in the text CHAPTER 5 HRS DETECTORS 169 Mirrors Frame Upper Mirror Middle section Section Tray section for 5102 Incident particles FIG 2 Figure 5 18 Cross sectional drawing of the counter along the particle direction showing the planar parabolic nature of the mirrors and the geometry of the PMTs as well as the final dimensions The joint of the two mirror surfaces in the middle of the counter defines the mirror ridge of electric shock through careless handling this high impedance also limits the current drawn in the unlikely event of a complete dielectric breakdown between the shields and the aluminum parts of the detector A schematic diagram of the electronic amplification chain is shown in figure 5 23 The operation of the aerogel detector is discussed in Ref 16 5 5 2 Responsible Personnel The following individuals are responsible for aerogel Cherenkovproblems Serdarevi Maja x5063 Segal Jack x7242 Wojtsekhowski Bogdan x7191 5 5 3 Safety Assessment The PMTs are under high voltage and care is required when handling any components of the counter As stated ear
187. in the CAMAC module 7 3 Online Analysis Data Checks The following tools are available for checking data online Scaler Display and Scaler Events Scaler rates and values are displayed using a MOTIF based display called xscaler writ ten by C Howell of Duke University Normally this is already running on adaqs2 or s3 It also runs on HP UX but the SunOS version is preferred If it is not running login as adaq and go to the appropriate directory which is home adaq EXPERIMENT electron scaler and home adaq EXPERIMENT hadron scaler for the E arm and H arm respectively where EXPERIMENT is an environment variable like e95001 Then type xscaler there Remember to push the button Start The first several pages are the scaler rates and the next half of the pages are the absolute scaler counts The scalers are cleared at the beginning of each CODA run Scalers are read out at approximately 0 5 Hz and injected into the CODA data stream as event type 140 A file scaler_history dat is maintained which is a complete history of scaler readings at the end of each run that ended normally For 1 TS mode this file is in home adev scaler 7 3 1 Analysis using ESPACE ESPACE is the main offline software package for analyzing Hall A experiments and it is used for rapid near online analysis in the counting room ESPACE is documented in a separate chapter but it is worth mentioning here in a list of essential tools for checking
188. ing in the hall In any case there are two pressure transducers in front of the right rack their values can be seen both in the Hall A directly on the panel and in the Counting House on the computer or on the display through the camera which should reveal immediately if there is any leakage The water system There are about 17 liters of pure water in the circuit The water tank the tubes the target and the cell containing it are made of stainless steel The tubes are joined by swagelok connectors The entrance and exit windows for beam passing through are made of 75 um Be the two side windows are made of 1 mil stainless steel The cell has been tested up to 2 bars for gas leaks No water leakage is expected unless the windows of the target cell break In this case some water carrying some radioactivity goes into the scattering chamber The calculations performed by Geoff Stapleton show that the radiological precautions necessary are rather low The water should not leak into the hall drains Measurements at convenient intervals will be made by the radiation control group on samples to permit determinations of the radionuclides yields In case of water loss or draining water the radiation control group has to be informed to take precautionary measurements The slow control system There are no significant hazards in working with this system due to the low voltages and very small currents However one must switch the power off to the w
189. ion from the median parameters indicates a change in the operational parameters of the FPP and should be immediately investigated Power Supplies and Electronics Procedures The power supplies and readout elec tronics associated with the FPP are a mixture of commercially purchased equipment and equipment designed and or assembled with the Rutgers University Department of Physics amp Astronomy Electronics Shop The reader is directed towards the manuals made available by the manufacturer for the detailed information not provided here for the commercial equipment For the Rutgers constructed equipment further documenta tion is available on the web page and through FPP notebooks try for example contacting R Gilman for notebooks main tained by Rutgers CEBAF Center phone 757 269 7011 The LeCroy 1458 HV control crate houses the Lecroy 1469P modules which control the HV for the FPP chambers The 1469P has 3 master HV channels and each master HV channel controls eight slave channels In slot 7 of the 1458 is the 1469P module which controls chamber 1 and chamber 2 In slot 8 of the 1458 is the 1469P module which controls chamber 3 and chamber 4 The individual slave channels can trip from high current faults or other trip faults but all eight slave channels must be raised and lowered together by setting the master high voltage The HV provides 1 8 1 9 kV nominal to each of the 5100 wires in the four FPP straw chambers The power supply is l
190. ion of the HRS Magnets Introduction This is an abbreviated operating manual for the HRS superconducting magnets specifically designed for Hall A experimenters It provides instructions for setting cur rents invoking NMR field regulation and general system monitoring Curious readers are directed to the references for more in depth operating instructions and other techni cal manuals Copies of the following supporting documents are available in the Hall A Control Room References WANG NMR Dipole Operation Manual Power Supply Dynapower User Manual Appendix NMR Tesla meter Appendix NMR Field REgulation Siemens Fug Q2 Q3 Power Supply Manual Saclay Danfusik Q1 Powersupply Manual TOSP HRS Dipole TOSP HRS Quadrupole Q1 TOSP HRS Quadrupole Q2 Q3 HRS SC Dipole Magnet Safety Review Vol 2 HRS SC Quad Safety Review Vol 1 Starting Hall A Controls The following is an abbreviated operational manual for the magnets supplied by Javier Gomez On hac x terminal Account hacuser Password hacuser CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS Circuit Parameters Imax 1800 A L 2 52H Tau slow 420 s 640 MITS Rdish dump resistor cable resistance total resistance Rtotal 0045 0015 006 Rdump 134 L 2 55 H Tau fast 19 s 29 MITS Magnet Dipole Arm Circle one Electron Arm Hadron Arm Megger check of coil 250 V DC Visual inspection walk through Set water inlet pressure to 100 psi Coil
191. ipole full of liquid 8096 actual open lead flows on Dipole to 80 slm as read from rack D171Q actual lead flows A Born Q2 Q2 full of liquid 80 actual open lead flows Q2 to 60 slm as read from the Q2 instrument rack meter actual lead flows dioe Q3 Q3 full of liquid 80 actual _ open lead flows on to 60 slm as read from the Q3 instrument rack meter actual lead flows Bu Power supplies POWER SUPPLY TURN ON PROCEDURES _ Verify UPSs as operational on all power supply controls with no current on magnets only red rotating beacons on Q1 RE visual inspection of main current leads dump resistor and lead flags for condition visual shorts etc unlock power disconnect switch and turn on AC power _ _ visually check power supply for faults when all faults have been cleared insure that power supply is in remote control Q2 m visual inspection of main current leads dump resistor and lead flags for condition visual shorts etc unlock power disconnect switch and turn on AC power turn on both sets of three pole breakers located on power supply _ _ visually check power supply for faults when all faults have been cleared lift lever on lower right side of supply insure that power supply is in remote control APPENDIX A HALL CHECKLIST 229 VEN visual inspection of main current leads dump resis
192. ition flanges defining the ports and coupling to the spectrometers can be added giving additional support to the middle ring Compressional stresses calculated using ANSYS assuming the middle ring was attached to the top hat and loaded with 25 000 Ibs were less than 3000 psi almost everywhere However stresses over small areas rose to levels 6000 psi near the entrance and exit CHAPTER 2 BEAMLINE 61 holes These calculations indicated that we did not exceed the safety limit of 15 000 psi for aluminum A simple model calculation shown in Appendix A gives the result 1434 psi which represents some average value over the midplane contact area Vacuum Pumping System The vacuum in the target chamber is maintained by an Alcatel 880 1 s turbomolecular vacuum pump The pump is connected to a 6 in port in the stainless steel ring between 130 lt 6 lt 180 The vacuum pump is fastened to a horizontal pipe connected to the chamber The vacuum pressure in the chamber is about 107 mm An additional Alcatel pump connected to an 8 in port should be added to obtain lower vacuum Both pumps may be isolated from the target chamber using gate valves which are remotely operated from the vacuum control rack and interlocked to the FSD system A 2 in all metal gate valve is located between the entrance flange to the chamber and the beam profile monitor An additional gate valve is located 2 m downstream of the target chamber to isolate the chamber from
193. itored in the sight glass on the side of the RESERVOIR Fill until the liquid level is near the top of the sight glass then close MV 242 Do not overfill to or above the top of the sight glass 5 Close valve MV 241 then open valves MV 243 and MV 244 6 Seal the cover on the REFILL CANISTER to prevent contamination Setting a Flow Rate The flow of each individual gas component and therefore the final gas mixture is con trolled by the Dynamass DM 2401 System the FM 8 Flow Ratio Modules and the Tylan General FC 280 Mass Flow Controllers The DM 2401 accepts and stores programs for the set of FM 8 s Each FM 8 controls one or two Mass Flow Controllers To set or alter a flow rate 1 Prevent the mixed gas outlet pressure from exceeding its 18 psig interlock trip level by either a closing valves MV 201 2 3 or b insuring that the detectors are consuming a sufficient quantity of gas to prevent this overpressure from occurring during the time it takes you to perform steps 3 11 below 2 Set the Auto Expert pressure control switch rear of mixer rack to EXPERT 3 Verify that the DM 2401 is in the NO MODE mode indicated by none of the LEDs in the column on the extreme left of the unit being illuminated If necessary press the MODE pushbutton until this condition is achieved 4 Press program select button C and verify that the corresponding LED illuminates CHAPTER 5 HRS DETECTORS 206 5 9 10 11 12 13 At t
194. kward integral data Forward end backward integral data are made of 3200 lines of 3 data each a line per trigger i e per mm of probe motion over the 3 2m of the total motion The first trigger line is missing the first data of the line is the probe position in mm which should be a round value from 1 000mm to 3199 000mm at forward pass and from 3199 000mm to 1 000mm at backward pass the 2nd data are the flux increment measured during the current step i e between the previous trigger and the current one in unit of 10 8Vs corrected from the gain the 3rd data are the time of the trigger since the start in microsecond units These field increments like the scan profiles can be plotted by standard plotters see Details on profile plot above The curve plotted online in arc integral adl is the time derivative of the above flux data multiplied by the gain to get the input VFC voltage after gain CHAPTER 2 BEAMLINE 52 Example of an integral file ARC magnetic measurement integral data file version 1 Idate THU MAY 27 15 28 09 1999 THU MAY 27 15 29 21 1999 llocal current A 142 25 142 25 remote current set A 140 11 140 11 remote current readout A 140 15 140 14 INMR field 0 2752619 0 2752621 NMR locked T T INMR stable INMR in position Zd plate position mm 1604 003 1604 003 Itemperature x z deg C 33 2 33 1 Itemperature x z deg C 32 8 32 7 Itemperature x z deg C 31 1 31 1 Itempe
195. l gt Adjust A coll e A 4 Illumin ON OFF gt Change Illumin mode e A 5 Compensator ON OFF gt Change Compens mode e A 6 Levelling with compensation gt Levelling 2nd level menu U Unit e gt U 0 Return to 1st level e U 1 Reverse A reading gt Reverse A reading 2 Change V display gt Select this V display 7 Sound ON OFF gt Change Sound mode U U e U 3 Change angle unit gt Sel this angle unit U U 8 Select configuration gt Select this configur 2 4 20 Summary of field integral The purpose is to measure absolutely the straight field integral of a BA 3m long dipole called the 9th dipole and located in the Dipole Shed It is of the same type as the 8 arc dipoles and is powered in series with them The ARC integral setup is basically made of 3m long plate the probe which is able to move inside the 9th dipole gap along the beam axis and carrying two field measurement devices a pair of pick up coils connected in series and a set of NMR probes The coils are on both ends of the probe and the NMRs close to the center at the upstream probe position the downstream coil is close to the dipole center the upstream is outside the dipole and the NMRs at one end of the dipole Door lt lt DIPOLE gt ater lt gt at the central probe position each coil is at one e
196. l A waterfall target for electron scattering experiment Nucl Instrum Meth A314 1 1992 SPIRES entry DOI server 82 G Bartozek et al The e760 lead glass calorimeter Design and initial test results Nucl Instrum Meth 10 47 60 1990 156 J A Appel et al Performance of a lead glass electromagnetic shower detector at fermilab Nucl Instrum Meth 127 495 505 1975 156 M Goldberg et al Radiation induced coloring of cerenkov coutner glasses Nucl Instrum Meth 108 119 123 1975 156 T Ferbel editor Experimental Techniques in High Energy Nuclear and Particle Physics Addison Wesley Publishing Co Inc 1991 156 Cebaf conceptual design report cdr 1990 156 C Lippert et al Particle discrimination in medium energy physics with an aerogel cerenkov detector Nucl Instrum Meth A333 413 421 1993 165 L C Alexa et al Empirical tests and model of a silica aerogel cerenkov detector for cebaf Nucl Instrum Meth A365 299 307 1995 167 238 BIBLIOGRAPHY 239 15 16 18 17 G J Lolos et al Performance and design characteristics for the hall a aerogel cerenkov counters Nucl Instrum Meth 385 403 411 1997 167 E J Brash et al Operational performance of the hall a mirror aerogel cerenkov counter Nucl Instrum Meth 487 346 352 2002 169 EPICS documentation can be found http www aps anl gov asd controls epics EpicsDocumentation WWWPages EpicsDoc html 210 C
197. l equipment and almost all of it could serve as an ignition source in the presence of an explosive oxygen and hydrogen mixture We have made an effort to minimize the dangers from the equipment that is most likely to come into contact with hydrogen gas There are a number of electrically powered devices associated with the target gas handling system All the pressure transducers in the system are approved for use in a hydrogen atmosphere The solenoid valves on the gas panels are explosion proof The AC power for the solenoids is carried by wires which are contained in either hard or flexible conduit There are also LEDs on the gas panels that provide an indication as to the status of the valve solenoids These are powered by a 24 V DC supply The readouts for the pressure transducers are mounted on the gas panels and the AC power for these readout units is in conduit All the pressure transducers have 4 20 mA outputs In addition to the electrical devices in the gas handling system there are a number of devices inside of or mounted on the scattering chamber All the devices which are in the scattering chamber must have their power delivered to them by wires in vacuum The insulation of these wires should be radiation resistant so Kapton has been used where available The following electrical items are in close proximity to or are actually in the hydrogen system Axial Circulation Fan The fans which circulate the hydrogen in the target are AC induc
198. lated In the sinusoidal pattern both the X and Y magnet pairs are driven with pure sine waves with 90 relative phase and frequencies which do not produce a closed Lissajous pattern In the amplitude modulated or square root of time mode both the X and Y magnets are driven at 18 kHz with a 90 phase between X and Y producing a circular pattern The radius of this pattern is changed by amplitude modulation at 1 kHz The radius modulation is controlled by a function generator whose function creates a uniform distribution of the area swept out by the beam motion It is not possible to switch on the fly between the two modes of operation as hardware changes are required One can view the status of the raster in the EPICS overview screen called General Accelerator Parameters where the set point for the radius amplitude and the readback of the peak current in the raster are displayed Control of the raster is done by first asking the MCC operators to set up the raster for a particular radius typically 2 5 mm The control software assumes a field free region between the raster and the target so it is only approximately correct because there are four quadrupoles in this region It is important to check the raster spot size and make adjustments if necessary The main adjustment is made by asking MCC to change the radius Relatively small independent adjustments to the gains on the X and the Y raster coils are available in the middle room of the hall A
199. lation and removal as a unit The trigger electronics are located next to the detectors as for the electron arm To reduce the resolution degrading effects of multiple scattering the entire interior of the spectrometer from the pivot to the detector hut is a vacuum vessel The ends of this evacuated volume are capped by relatively thin vacuum windows As mentioned subsystems will be discussed in more detail in the next three sec tions The remainder of this section will describe some features common to the two spectrometers then the following major sections will be devoted to the specifics that are not common 4 1 1 Safety with Regards to the Spectrometer The principle concern with the spectrometers is that they are large and have associ ated vacuum hydraulic cryogenic and magnet systems all of which can be potentially dangerous The bogies which move the massive 1200 ton spectrometers must be carefully op erated Inspection of the wheels to ensure there is no debris which the wheels could ride over is mandatory Similarly personnel need to be aware that the spectrometers are moving so that no one inadvertently gets trapped The vacuum systems associated with the spectrometers are essentially pressure ves sels Care should be exercised so as not to puncture the windows The magnets themselves are installed inside cryostats These vessels are exposed to high pressures and are therefore equipped with safety relief valves and burst discs
200. ld the right direction changes NMR locked but current Normal operation Wait going in the wrong direction NMR locked but field not Field regulation is Check that field regulation correct and current not disabled or software is enabled Enter desired changing is confused field value or one very near the desired value again NMR field display freezes NMR Gaussmeter is not Push RESET Usually but not always communicating with shows 0000000 software Table 4 5 NMR troubleshhoting CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 126 4 2 5 Powering Up Dipole Magnets Use these instructions to recover from loss of a magnet due to a fault e g He level or lead flow fault The order of actions matters Contact Tech on call if anything behaves funny or things don t respond as expected Sometimes after a trip an access to the Hall is required to reset things 1 Wait for Iout 0 you can t and don t want to do anything while the magnet is in emergency fast dump mode 2 While waiting make a log entry re the fault Give details such as time coincident activities and nature of the fault 3 Make sure the fault is cleared e g He level and flow rates returned to normal values and stable 4 In the HRS Hadron Electron Dipole Systems control panel a Press RESET verify that all faults are cleared in the middle column b Press START Display will indicate Power Supply ON and magnet ENGAGED Power supply and
201. le ID for coincidence experiments The focal plane polarimeter on the HA operates with proton momenta up to 3 GeV c with a figure of merit 0 03 The detector packages are installed inside of the Shielding Huts SH Access to the Shielding Huts is via very heavy swinging front doors The main structure of the SH is made from 3 in thick steel plates The side walls and bottom surfaces of the SH are CVS revision Id overview tex v 1 3 2003 06 06 17 00 27 gen Exp 133 CHAPTER 5 HRS DETECTORS 134 covered inside with 1 in thick lead slabs Outside of the steel box concrete is used for neutron protection The front door has about 34 in of concrete and 3 in of lead Side walls are covered with 17 in of concrete The roof of the SH has 10 in of concrete above 3 in of steel The lower half of the side walls facing the beam dump have an additional cover of 15 in of concrete Additional Line of Sight Shielding LSS is installed at a distance of 5m from the target This consists of 2 to 3 m of concrete High energy pions interact in this concrete before decaying The LSS reduces the rate of high energy muons which are produced in pion decay The overall result from SH and LSS is a reduction factor of 10 to 20 in the counting rate of a single scintillator counter according to calculations The 2 VDCs provide accurate tracking information They are mounted on a movable frame which slides along Thompson rails to hard stops The position of the
202. lier on in this report the insulating material between the u metal shield and the aluminum exoskeleton far exceeds the operating voltage In addition the 11 MQ resistor between the u metal shield and the HV source restricts the current flow below the critical 1 mA level The combination of Tedlar film plexiglas composites and injection moulded bases are all safe to handle but care should be exercised when handling the aluminum parts of the counter or touching the metal back plate of the CHAPTER 5 HRS DETECTORS 170 Figure 5 19 Photograph showing the final arrangement of the double sidewall structure and the close spacing of the housings for the PMTs The bottom section of the counter with the tray and the aluminized mylar reflector lining is also shown In this picture the particles would be incident from the bottom toward the top of the counter The upper mirror section has been removed for clarity CHAPTER 5 HRS DETECTORS 171 Figure 5 20 Photograph showing the middle PMT section with the double sidewall structures and the housings for the PMTs with the top mirror section attached The tray has been removed and the white tabs on the mirrors are pieces of tape holding a temporary protective film in place to prevent damage to the mirror surfaces during transportation In this figure the particles would be incident from the top toward the bottom of the picture CHAPTER 5 HRS DETECTORS 172 Reflectivity
203. litorr roughing valve closed at rack 1H71B01 channel 4 cold cathode gages on at gage in rack 01 cold cathode 5x10 5 actual cold cathode reading _ check dipole turbo for on magnet controls Q1 Q1 full of liquid 8096 actual A open lead flows on Q1 to 80 slm as read from rack 301710 APPENDIX A HALL CHECKLIST 230 ES actual lead flows A ci B cctv camera and focused D1 __ Dipole full of liquid 8096 actual _ open lead flows on Dipole to 80 slm as read from rack D171Q actual lead flows AL B Q2 Q2 full of liquid 80 actual open lead flows on Q2 to 60 slm as read from the Q2 instrument rack meter actual lead flows 23 Q3 Q3 full of liquid 80 actual open lead flows on Q3 to 60 slm as read from the Q3 instrument rack meter actual lead flows A Bec Power supplies POWER SUPPLY TURN ON PROCEDURES Verify UPSs as operational on all power supply controls with no current on magnets only red rotating beacons on Q1 E visual inspection of main current leads dump resistor and lead flags for condition visual shorts etc unlock power disconnect switch and turn on AC power _ visually check power supply for faults when all faults have been cleared insure that power supply is in remote control Q2 mE visual inspection of main current leads dump resistor and lead flags for co
204. ll other 2mm 2 gt 12 5 Figure 4 13 Sieve slit collimator for optics calibration 130 CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 131 to the scattering chamber and Q1 quadrupoles all necessary safety precautions with regards to vacuum windows electrical power cables cryogenic transfer lines and high magnetic field should be taken 4 3 3 Operating Procedure Slit position is changed remotely from the standard Hall A control screen CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 132 4 4 Spectrometer Alignment At present the systems implemented to determine the alignment of each spectrome ter roll vertical angle pointing and horizontal angle pointing without the help of the Accelerator Division Survey group are limited to roll vertical angle and horizontal angle A bi axial inclinometer is used to determine the roll and vertical angle also known as pitch of each spectrometer These inclinometers are attached to the back of the dipoles at the power supply platform level The inclinometer measurements are displayed in the main Hall A controls screen alignment mosaic Agreement between the inclinometer readings and survey measurements are better than 0 1 mrad over all presently available history The horizontal spectrometer angle is determined from floor marks set in place by the survey group Floor marks have been placed every 0 5 covering the useful range of both spectrometers The marks are
205. llisions This leads to an avalanche and a gain of about 10 per primary ionization under the conditions in which the FPP is run The movement of the positive and negative ions leads to a voltage drop on the wire or equivalently to a negative analog signal The analog signal is about 20 ns long with a negative peak current of about 40 uA and propagates towards each end of the straw At one end of each straw is a board that supplies high voltage see Figure 5 25 impedance matching on this board with a 1500 pF capacitor and a 370 resistor reduces reflection of the signal The other end of each straw is connected to a readout board that amplifies dis criminates and multiplexes the input signals see Figures 5 26 and 5 27 At the readout end the signal is coupled to ground through a 1500 pF capacitor followed by 310 50 2 resistors In parallel with the 50 resistor are diodes to limit the signal size preventing damage to the readout board circuitry An amplifier samples the signal over the 50 resistor The amp gain is about 10 mV A resulting in a 400 mV signal to a comparator A threshold voltage input to the readout board is put over a voltage divider consisting of 1500 10 resistors For the typical 4 V threshold applied to the board the comparator puts out a logical pulse when the 400 mV peak signal rises above the 4 V 151 26 mV threshold One shots are then used to fix the width of the logical pulse
206. located at a distance of 10 m from the target center A ruler attached to each spectrometer dipole runs over the floor marks and it acts as a vernier to interpolate between marks The location of a given floor mark on the ruler can be viewed from the Hall A Counting House through a TV camera The camera is able to move along the length of the ruler so that any parallax effect can be eliminated The camera motion is controlled from the main Hall A controls screen alignment mosaic through two push buttons Two fields on the same mosaic Flr Mrk Vernier allow one to input the values read from the TV monitor The effective spectrometer angle is then calculated and displayed on the same mosaic A terminal based program setspec is available on the controls computer hac which for a given angle returns the floor mark value and its location on the ruler to which the spectrometer should be set to obtain the desired angle Spectrometer horizontal angle surveys and floor mark determinations agree to 0 2 mrad 4 4 1 Personnel Responsible J Gomez pager 849 7498 8 CVS revision Id AlignmentOps tex v 1 4 2003 06 06 16 15 32 gen Exp 9 Authors J Gomez mailto gomez jlab org Chapter 5 HRS Detectors 5 1 Overview The detector package of each spectrometer has trigger tracking and particle ID compo nents In addition the Hadron spectrometer has a unique proton polarimeter Particles which have passed through the magnetic elements fi
207. ls below After the scan check the peak rightmost quality it must be compact Gauss curve with a good signal noise ratio 75 If scan 1 and 2 are not compact report to MCC and make sure that the fast feedback is ON If scan 3 and 4 are not compact report also to MCC and make sure that the energy feedback and the kresting are ON If the scan seems OK start a field integral measurement and report to sahaQjlab org with as much details as possible at least the file names for data analysis and beam energy determination Record the mail in the e logbook Don t forget to save the files 2 4 10 Details on MEDM window print To print the MEDM window put the mouse cursor somewhere in the background part of the ARC window outside the plots push the mouse right button select print release the button It should go on chalhp if you work from the counting house 2 4 11 Details on profile plot To plot the profile use your favorite curve plotter hvplot xmgr The scan file is a plain ASCII file with a line per acquisition trigger and two float per line position in encoder unit 4096 0 per 2 500 mm or turn and voltage after gain in V First the forward profile with increasing x then the backward one with decreasing x x coordinate transverse to the beam and horizontal Towards beam right for scanners 1 to 4 towards beam left for 5 and 6 Some lines are header lines In this case the 1st character is a
208. m is controlled by the computer This allows one to place the desired target in the beam 3 3 Authorized Personnel The principle contacts for the cryogenic targets are listed in table 3 3 Every shift must have a trained target operator whenever the cryogenic targets contain liquid These operators are trained by one of the experts listed in the table and certified by J P Chen CHAPTER 3 TARGETS Component A Staff jii Outside Group Remark Chamber Vacuum Ed Folts 7857 Or Technician On Call Cryogenic Target J P Chen 7413 M Kuss 5064 J H Mitchell 7851 M Seely 5036 Target Group C Keith 5878 Target Group ESR CHL 7405 Cryo Group ESR Cryo on Call MCC Table 3 6 Contact Personel for the Cryogenic Targets and Scattering Chamber 8l Additional documentation on the targets and the target controls is available from J P Chen In particular reference 6 is highly recommended CHAPTER 3 TARGETS 82 3 4 Waterfall Target 9 The waterfall target system provides a target for experiments on 9O see figure 3 1 The conceptual design of the waterfall target system for Hall A is very similar to the one used at Saclay 7 The thickness of the waterfall target can be modulated by changing the pump speed this adds flexibility to the system and allows the user to choose the best value according to the wanted resolution and luminosity The hydrogen in the water ca
209. mit When delivery of beam and RF power is permitted to the exclusion area the PSS state is Beam Permit Reaching this state requires having passed through the RF Power Permit state 1 2 6 Run Safe Boxes The Personnel Safety System includes Run Safe boxes which are located throughout Hall A and approximately every 100 feet in the linac A run safe box has three positions Safe Operational and Unsafe When the hall is in Restricted Access the run safe box will be in the Safe position While in this position the PSS prevents delivery of beam to the hall Before beam can be delivered the hall must be swept to ensure that no one is left inside During the Sweep each run safe box is moved to the Operational position in preparation for Beam Permit After the sweep has been completed and the hall is placed in the RF Power Permit state the run safe box will show Unsafe Each box has an emergency stop button If you see the box in the Unsafe position you are in danger of receiving high levels of ionizing radiation Immediately press the emergency stop button exit the hall and call the Machine Control Center Crew Chief at extension 7050 1 3 Hall A Access Access to Hall A is governed by the Jefferson Lab Beam Containment Policy and Implementation document This document can be found in the Jefferson Lab ES amp H Manual Section 6310 Appendix T2 Work in designated radiation areas will be gov erned by the Jefferson Lab RadCon Manual Access
210. n be used for calibration purposes Elastic scattering from the hydrogen in the target can be used to measure and monitor the target thickness The counting rate in the elastic peak is directly proportional to both the beam current and the target thickness Pressure f Transducer Manometer Figure 3 1 The target system The waterfall target can be single foil or multi foils according to the need of the particular experiment In fact a modified version of this target has been built and used for experiments at NIKHEF a 150 mg cm single foil and a three foil one 60 x 3 mg cm The target built for Jefferson Lab Hall A for the two commissioning 5 OVS revision Id waterfall target tex v 1 1 2003 06 06 17 09 04 gen Exp CHAPTER 3 TARGETS 83 experiments 190 E89003 and E89033 is three foils one with thickness ranging from 130 200 mg cm for each foil depending on the pump speed The main components of the target system are 1 The waterfall target container also referred to as target cell in this document 2 The solid target ladder and the solid targets 3 The hydraulic system 4 The gas system 5 The movement system 6 T he slow control system The waterfall foils are produced inside the waterfall target container which is mounted in the standard Hall A scattering chamber The water continuously pumped from a reservoir goes through a heat exchanger into the target zone and then b
211. n parameters can result in a change in the operational parameters of the VDCs and should be immediately investigated If at all possible gas flow should be continuously maintained even in no beam time periods This avoids time loss to reconditioning and maintains the desirable steady state operating condition Further it is critical that gas flow has been maintained for 24 hours prior to any power up Power Supplies and Electronics Procedures The power supplies and readout elec tronics associated with the HRS VDCs are all commercially designed The reader is directed towards the manuals made available by the manufacturer for the detailed infor mation not provided here A Bertan 377N HV power supply provides 4 00 kV nominal to each of three HV planes in a given VDC detector package via a 10 MO Hammond splitter box see Figure 5 4 The power supply is located in the detector hut in a NIM bin on the upper level of the space frame This unit may be controlled either manually or remotely via the EPICS CHAPTER 5 HRS DETECTORS 139 regulator valve upper chamber a lower chamber input exhaust bubbler VENE bubbler rotameter Figure 5 3 Gas flow schematic CHAPTER 5 HRS DETECTORS 140 6kV AN HV plane 1 2 8 2 MQ field lines 10kQ V signal wires 0000000000000000000090000000000 4 00 kV 6kV HV plane 2 I e
212. n the iron yoke For a probe in a central position for more than about one hour the Tx z and Tx z sensors should give the yoke temperature i e the shed temperature plus 0 to 5 C depending on the current LCW temperature and CHAPTER 2 BEAMLINE 54 the magnet shed temperature history The 4 temperatures are also displayed inside the shed on the electronics rack These values are digitized by separate ADCs so they may differ from the remote values by 0 1C 2 4 29 Details on AC power integral All the shed electronics and computer except the motor power see details about the Power Switch below are powered through a UPS Uninterruptible Power Supply whose role is to protect the setup from short 1 4 h power outages and to convert the US AC power 60Hz 200V between two phases in a well stabilized AC power of European type 220V 50Hz When working in the shed be careful about the electrical hazard as the setup can remain powered a long time after interrupting the UPS input see Shed access and safety above The UPS unit is located under a table in front of the electronics rack It has a display a small keyboard and a beeper The beeper activated means that some important message about the UPS is displayed In this case use the keys to scan the UPS memory read the messages record them in the e logbook stop the beeper and inform Arun Refer to the UPS manual available in the shed for details of operation 2 4 30 Details
213. ncident beam They are also used to absolutely calibrate the two associated beam position monitors located in front of the target CHAPTER 2 BEAMLINE 20 4 Beam Exit Channel After the target vacuum chamber which was built by the University of Virginia there is an exit beam pipe which transfers the scattered beam onto the dump tunnel under vacuum This exit beam pipe is made of a thin walled aluminum spiral corrugated pipe of welded construction The largest diameter is 36 inches with a 0 164 inches wall thickness and the smallest diameter is 6 inches with a 0 042 inches wall thickness The whole assembly is rather light approximately 800 kg and is supported by H shaped adjustable stands To prevent possible linear collapse of the larger diameter sections under vacuum load four aluminum channels of total cross sectional area of 3 are welded to its side A vacuum of 107 Torr is maintained with a turbomolecular pump The exit face of this pipe has a 12 port and is connected to the diffuser with a Beryllium window 2 1 2 Authorized Personnel All magnets dipoles quadrupoles sextupoles beam correctors and beam diagnostic devices BPMs scanners Beam Loss Monitor viewers necessary for the transport of the beam are controlled by Machine Control Center MCC through EPICS except for special elements which are addressed in the subsequent sections The detailed safety operational procedures for the Hall A beamline should be essentially
214. nd Main Relay are indicated clear them by correcting the indicated fault 3 Check alcohol supply and Bubbler temperature Fill and or adjust as necessary see Adding Alcohol CHAPTER 5 HRS DETECTORS 203 10 11 12 13 14 Check that adequate supply bottles of appropriate gasses are attached to the high pressure supply manifolds and valve one bottle ON for each manifold Verify that all used main pressure regulators outside are set for 45 50 psig Select Manual Expert pressure control using toggle switch on panel in rear of mixing station behind flow controller Note that while in Expert mode there is no automatic delivery pressure control Overpressure is prevented only by the overpressure shutoff switch and the alcohol reservoir relief valve Verify that the Dynamass Flow Control System DM 2401 is in Non VG mode by e Press PROGRAM SELECT pushbutton A e Put the DM 2401 in NO MODE mode if it is not already by pressing the MODE pushbutton until all LEDs in the column of LEDs on the left of the unit are off e Simultaneously press and release PROGRAM SELECT buttons A and C e Press the MODE pushbutton until the OPT 1 LED is lighted Verify that the display for channel 4 reads all zeros e heturn the DM 2401 to NO MODE Set Dynamass Flow Control System to Program D Zero Flow Put the DM 2401 in FLOW MODE and verify that all flow settings are at zero With the DM 240
215. nd of the 3m long dipole and the NMRs close to the dipole center Door lt lt DIPOLE gt Suum Miss tomate e lt PROBE gt at the downstream probe position the upstream coil is close to the dipole center the downstream is outside the dipole and the NMRs at one end of the dipole CHAPTER 2 BEAMLINE 47 DOORS sy cai lt DIPOLE gt RN NN PROBE gt We call upstream the position where the probe is the closest to the shed access door Among the 3 above positions the only one where the NMR can lock on the dipole field is the central one as in the extreme position of the probe the field homogeneity is not sufficient The probe position is controlled by a linear encoder The Z axis refers to the beam direction increasing from upstream to downstream We use three kinds of Z Zm to locate a point inside the magnet The dipole center is at Zm 0 and the yoke ends at 1500 mm Zp to locate a point inside the probe The probe center is at Zp 0 Each of the 4 NMR probes has a Zp given in the file magnet dir At a temperature of 21C the coils are at Zp 1519 815mm from magnet dir Zd to refer to a displacement of the probe w r t the dipole Zd 0 refers to the upstream home position of the probe The integral measurement is performed from Zd 0 000mm 1st PDI trigger to Zd 3199 000mm last PDI tri
216. nd that the secondary pres sures indicated by the gauges above the bottles are at about 40 45 psig normally these should not need adjustment 3 Press the Low Pressure Override button on the interlock panel in the gas shed 4 Reset all Excess Flow Valves by turning their handles to OPEN RESET waiting for about ten seconds then returning their handles to AUTO SHUTOFF 5 Verify that all faults are now cleared on the gas interlock panel Restarting flow after a power failure Normally the gas control system is protected from power outages by an uninterruptable power supply UPS If the system is nevertheless disturbed by a loss of power then perform the steps outlined in section 3 2 Startup Procedure 5 8 8 Maintenance Periodic Inspections Anytime work is done on any part of the gas system or there is an occurrence that could possibly have damaged the gas system the system should be carefully inspected and checked for leaks CHAPTER 5 HRS DETECTORS 209 The flammable gas detector heads and control system should be tested periodically for proper operation in accordance with the manufacturer s recommendations and the TJNAF fire safety program Each sensor feeding the Gas Interlock Panel should be exercised at least annually for proper operation The interlock system itself should be tested at the same time to insure that it interrupts the supply of gas when it is tripped The high pressure manifold and bottle connections sho
217. ndition visual shorts etc unlock power disconnect switch and turn on AC power A turn on both sets of three pole breakers located on power supply _ visually check power supply for faults _ when all faults have been cleared lift lever on lower right side of supply APPENDIX A HALL CHECKLIST 231 insure that power supply is in remote control Q3 26 visual inspection of main current leads dump resistor and lead flags for condition visual shorts etc unlock power disconnect switch and turn on AC power turn on both sets of three pole breakers located on power supply _ visually check power supply for faults A when all faults have been cleared lift lever on lower right side of supply insure that power supply is in remote control Dipole PES visual inspection of main current leads dump resistor and lead flags for condition visual shorts etc unlock power disconnect switch and turn on AC power _ turn on power lever on right upper side of supply _ visually check power supply for faults on supply and at rack when all faults have been cleared insure that power supply is in remote control cctv camera on and focused _ check power supply for proper polarity NMR gradient compensation for on and proper polarity Target A windows functional cctv cameras on and focused target light on _ backing pump on at pump turbo on at rack 1H75B09
218. ngles are displayed again but with A 0 0000 push to proceed the sub menu MEAS P is proposed you must accept en ter you have then the angles displayed push to come back to the THEOD menu then push enter to accept it you should still have A 0 0000 you have a new origin of the A angles CHAPTER 2 BEAMLINE 42 measure the autocollimation angle open the light tube plug the autocollimation light cable turn ON the autocollimation power switch on the battery adjust the autocollimation power potentiometer to half range remove the theodolite handle to let the cable go through adjust the occular small knob on the optics to your vision until you have the cross hairs well focused adjust the main focusing large knob on the optics to infinity turn counter clock wise up to the limit and come back by 1 4 turn adjust the V angle to 90 00 deg first move the optics second fasten the V break and use the V knob adjust the A angle to point in the direction of the light tube first move the theodo lite second fasten the A break and use the A knob using the A knob search for a light signal focus on it main focusing the autocollimation pattern is a yellow green cross adjust A and V angles to get the cross hairs on the autocollimation cross fine adjust both focusings then check if the pattern you have is the good one there are 2 wrong autocollimation patterns when you change by a
219. nly meaningful if 12V is ON Push OUT IN for desired direction Engage the 300 pur supply When the door is moving door status is blank and limit switches read zero When the door reaches it s position the door status will be displayed 7 Turn off S0V Figure 5 30 EPICS GUI for the carbon doors CHAPTER 5 HRS DETECTORS 190 e Before moving a straw chamber ensure that any protective plates are in position e Disconnect and reconnect all TDC HV and LV cables with care e When initiating gas flow pay strict attention to the feedback parameters Straw chambers are not very sensitive to overpressure of perhaps 50 100 Torr but the straw chambers can be easily destroyed by a few Torr underpressure e Never attempt to apply HV to the chambers until gas flow conditions have reached steady state e As the amount of heat generated by the pre amp discriminator cards is substantial always make sure adequate cooling is provided before attempting to run This is mostly ensured by making certain that the various cooling holes through the Faraday shields are not covered The chambers have internally mounted fans where needed which are powered up along with the readout cards e If the leakage current on the high voltage rises linearly with voltage then a wire has broken and is shorted to ground 5 6 5 Safety Assessment The following potential hazards have been clearly identified The High Voltage System The LeCroy 1458 HV lo
220. nt above 1800 A 4 4 GeV c The supply for the hadron dipole may not be operated above 1200 A 3 2 GeV c The dipole for the HRS spectrometer is a superconducting cryostable magnet Its basic parameters are an effective length of 6 6 m a bend radius of 8 4 m and a gap width of 25 cm It is configured to achieve a 45 degree bending angle for 4 GeV c momentum particles at a central field excitation of 1 6 T For the HRS dipole to reach 1 6 T an operating current of about 1500 A is required CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 113 The dipole has been designed to achieve cryostability up to a field of 2 T and this property has been extensively tested up to a field of 1 6 T The cryostable coils are equipped with an energy removal circuit to cover the possibility of an unrecoverable quench However this can only happen if the helium level drops below the coil during operation The current to the coils will be provided by a Dynapower System power supply which can operate up to 2000 A and 10 V This power supply is located on the gantry beside the dipole and will be cooled with a maximum water flow of 35 liters per minute The flow of the magnet cooling water will be regulated by flow meters installed on the floor of Hall A The total water flow needed to cool the 4 power supplies for the HRS magnet system dipole and quadrupoles amounts to 80 liters per minute with a supply pressure of cooling water for Hall A of 100 psi 4 1 4 Operat
221. nt must be done by matching the signals on top of the scattering chamber Encoder substitution procedure First of all consider that the encoders are very delicate mechanisms and must be carefully handled please NEVER use hammers or similar tools unless you want to risk destroying them moreover do not apply torques directly on their axes and turn them only by hand For the substitution execute the following procedure 1 Switch the whole system off 2 Remove the cable from the broken encoder CHAPTER 3 TARGETS 98 10 11 12 13 14 Remove the cylindrical lead shielding which is around the encoder Remove the three screws at the base of the encoder on the stainless steel ring Now you can remove the encoder It has its stainless steel ring fixed on the base Remove this ring from the encoder by unscrewing it Take the spare encoder from the wooden box number 1 near the wall Without remounting the encoder you must realign the target to the reference po sition by turning the top of the scattering chamber with your hands and aligning the reference point with the alignment signs on top of the scattering chamber this can be done manually after removing the motor corresponding to that movement When you remove the vertical movement motor the target could drop down which may severely damage the integrity of the target for this reason you have to block the cog wheels by putting something among the
222. o check the system including the trip protection and to anticipate a gain change for scanners 1 and 2 2 4 15 Detail on encoder change scanner The main screw shaft is coupled to the stepper motor by a bellow coupler bellow 1 and the motor to the encoder by a second bellow coupler bellow 2 If for any reason encoder change motor change one of the bellows slept the angular relationship between the screw and the encoder is lost then these two objects must be linked again in good angular agreement see detail the theodolite survey of the bench must be redone see detail 2 4 16 Detail on encoder re mount scanner The procedure is based on 2 rules the home position is defined by an encoder reading 4096 enc units this home position must be at about 1 2 turn 2048 1 25mm from the Low Limit Switch LLS transition So this transition must happen at encoder reading 2048 CHAPTER 2 BEAMLINE 40 if the Low Limit Switch was also changed then the rule is that the external fiducial must be at 230mm from the beam nominal axis when the encoder reading is 118407 survey position This rule needs the help of a survey The procedure is the following by software see scanner expert task detail or by hand by acting on the bellow 1 set the scanner in the convenient position LLS or survey decouple the bellow 2 connect the encoder to the control box readout by hand turn the encoder shaft up to hav
223. o refill the cell in the case of very small leakages remember that the pressure must be about 1 02 Atm push the pressure bottom of the main window The pressure control window will appear The operation is self explaining Just remember that the gas flows only if you keep the button pressed Calibration of the movement system For normal operation the user does not need any additional information about the movement system The following calibration tables target and angle positions versus encoder values are useful for checking purposes notice that if the target changes the calibration has to be performed again The following values are OK for the waterfall carbon beryllium iron target which was installed in July 96 Target Encoder Position Water 17301 Up Survey 38528 Carbon 42949 Beryllium 47371 Iron 51792 Low Survey 56213 The vertical scale factor is 1 encoder unit 5 74 um The angular correspondence is CHAPTER 3 TARGETS 96 Angle Encoder Position 0 degree 27361 30 533 degree 26479 that means 1 encoder unit 0 035 degree When a new calibration is required only the expert s is are allowed to perform the following steps e Go to the hall e Run the calibration program setlimits vi on MacA in order to allow the com puter to get the limits of the movement ranges up down and rotation if enabled this procedure takes several minutes e Ro
224. ocated in the detector stack at the top of crate 6 in the upper electronics level This unit is controlled through HAC13 Connections from the power supply to the chambers are made using standard SHV connectors mounted on red RG 59 U HV cable good to 5 kV The high current low voltage supply boxes were assembled by Rutgers University They are designed to provide a maximum current of about 1 6 0 6 A at 5 5 V to each of the 318 readout cards on the four chambers There are 63 63 90 102 cards on chambers 1 2 3 4 Typical operating currents are about two thirds of this nominal http www jlab org gilman fpp homepage html CHAPTER 5 HRS DETECTORS 186 maximum value The 5 V power lines are independently fused to each card Each of the eight supply boxes contains two or three power supplies each rated for either 35 or 50 A There are two power boxes for each chamber Six boxes are located at the lower rear end of the detector stack The second boxes for chambers 3 and 4 are located at the top of the detector stack on an aluminum plate just off the upper electronics level These power boxes are monitored through EPICS but turned on off though front panel switches Hewlett Packard 6111A power supplies are used to provide typically 2 3 mA current per readout card Each of the front and rear chambers have their own power supply The front chambers thresholds are fused to limit current drawn in case of a short on the board The
225. of REGINA Faculty of Science Electronics Shop Title Burte 8854 Tube Dynode Chain Figure 4 Gate 17 Dec 90 Page 1 1 Notest HV version 1 With matching pot Fie 5854 070 Figure 5 12 The 5 PMT base used in 53 trigger scintillators devices and care should be exercised during handling and setup The external aluminum parts the front and rear housing and the back plate 17 are all grounded via the ground of the BNC 18 and SHV 19 connectors Since the back plate is connected to the coupling nut via the three steel posts the front plate is also grounded via the coupling nut and the back plate Common sense however dictates that the bases are not to be handled while under high voltage even when multiple grounding connections are provided The mu metal shield is also under high voltage since it is connected to the cathode Electrical isolation between the mu metal shield and the front tubular housing is assured by the high dielectric retainer ring 12 and the plastic insulator 09 at the free end of the mu metal shield The air gap between the mu metal shield and the front tubular housing is 6 mm thus the breakdown value 18 kV far exceeds the maximum 3 0 kV of the PMT In the event that the mu metal shield is inserted without the plastic insulator ring CHAPTER 5 HRS DETECTORS 155 or some oaf decides to operate the base without the outside housings the 11 MQ resistors between the HV and the mu me
226. olerances to fine levels The double walled structure on both sides of the enclosure further increases the rigidity of the exoskeleton by forming a second outer wall on each side very similar in configuration to the inner one and attached to the latter with crossbolt braces as shown in the photograph of figure5 19 Each end plate is made out of the same aluminum alloy as the side walls and also incorporates stiffening lips folded integrally to each plate one at the top and one at the bottom Each end plate has been provided with inlet and outlet gasline connections which will be used to fill the counter enclosure with dry gas to protect the silica aerogel from water vapour absorption figures 5 19 and 5 20 show the bottom tray sections and main plus upper mirror sections respectively The main middle or PMT section in figure 5 20 contains the PMTs and provides the strength and rigidity for the whole counter The one piece aluminum end plates are also shown in both photographs All internal surfaces of the detector except the planar parabolic mirrors themselves are lined with aluminized mylar to increase the overall reflectivity of the counter The mirrors are made in 45 x 20 5cm moulded surfaces formed in one rigid structure The rigidity is provided by two layers of carbon fiber epoxy composite backing with a com bined thickness of 0 28 mm and a single sheet of mylar with thickness 0 127 mm The special mylar materi
227. oller and the target to control the beam geometry on the target and their use will not be discussed here Each scanner has a motor ball screw shaft encoder vacuum penetrator system mov ing accurately a set of 3 tungsten wires through the beam Each time a wire crosses the beam a PMT located a few meters downstream records a signal due to the electromag netic shower induced by the beam in the wire Both forward and backward passes are recorded The motion is a horizontal translation and for a forward pass the translation is from beam left to beam right the two first wire crossing the beam are at 45deg from the vertical the third wire which is the only important for the ARC energy measurement is vertical Recording during the scan the scanner position and the PMT output voltage allows us to determine the beam position at each scanner location Then using calibration data not detailed here we deduce the net beam bend angle through the arc This result measured in dispersive arc tuning along with the field integral of the arc dipoles provides an accurate determination of the beam energy The list of the operations for an ARC energy measurement is given here and will be detailed after 1 check the pulser scanners 2 check the HV scanners 3 check EPICS scanners 4 check space on disk scanners 5 check the integral see Details on integral system check below 6 ask for chicane off put target in a safe position ask 54A ach
228. on 1 WAY to execute the motion If you want to move the scanner fron its current position by 10mm towards the beam and if the current position is 100000 then enter 100000 10 2 500 x2000 108000 and push on 1 WAY If you want to go to the LLS position enter a large negative value like 1000000 and push on IWAY Note Limit switches will not stop the motor at a very reproducible position CHAPTER 2 BEAMLINE 41 2 4 18 Detail on theodolite survey of a bench The goal is to measure the H angle between the segment joining the fiducials of the 2 scanners of the bench in their survey position and the normal to the autocollimation mirror associated with this bench The procedure is the same for both benches except that the upstream one needs a BSY access the downstream one just a Hall A access providing the light tubes were left in straight position the upstream angle is 0 only affected by a change in the scanners the downstream one is 6 deg and it can be affected by a change in the scanners or by a motion of the tunnel the upstream autocollimation is at short distance the downstream one is at long distance through the light tubes and the line of sight is bent by a pair of mirrors both at forward and at backward pass The procedure is using the expert task see detail set both scanners in their survey position encoder 1184074 2 install the theodolite on its support and level it carefully mount the
229. on to the safe position as soon as the door to the shield house opens Unless this box is rearmed with the special key the beam cannot run 1 3 2 Restricted Access Procedure Restricted Access is used when the hall will be open for an extended period of time or a large group will enter to work To drop the hall to the Restricted Access state first notify the MCC that you wish to open the hall in the Restricted Access state The MCC will drop the hall status to Controlled Access and send an ARM to survey the hall Before anyone can enter the hall the ARM will carry out a radiation survey and post radiation areas The hall is placed in Controlled Access during the survey to ensure that no one enters before it has been completed Upon completion of the survey and posting of radiation areas the ARM will leave the hall and notify the MCC that they can drop CHAPTER 1 INTRODUCTION 14 the hall state to Restricted Access With the hall in the Restricted Access state anyone with the appropriate training may enter and work The key release procedure is not required To return the hall to Beam Permit from the Restricted Access state a full inspection must be carried out This is begun by setting all equipment to its operating state fol lowing the Hall A checklist and then clearing all workers out of the hall Next a request is made to the MCC to arrange a sweep of the hall and to restore the Beam Permit state The MCC will send over an ARM and set t
230. one can set the pump speed to minimum either from MacA by using the slide on the right of the main window or use the button on the front panel of the right rack and then turn the pump switch on the right rack to off position The reactivating of the pump needs to be done from the same switch used to deac tivate it see Waterfall Activating Procedure Target movement procedure After the slow control program 2 is activated CHAPTER 3 TARGETS 95 e Press the motor button on the bottom of the main window of the computer a motor control window will appear e Select the type of movement up down rotation e Select the target or the angle the Move button should be activated if everything is O K e Press the Move button a warning message reminds you to be sure of your action Be sure that the beam is off e During the movement watch the two displays showing the current position and the one to be reached e When the final point is reached a message will inform you of the success of the operation Otherwise a warning message will tell you about the faulty status Eventual gas flow operating procedures The gas filling of the target cell when empty has to be done in Hall A on the right rack there is a self explaining panel The washing button has to be pushed for about 15 minutes to open the inlet and outlet valves in order to allow the gas to replace the air which fills the target cell In order t
231. ongside the box beam to the gantry roof inside the shield house 4 1 2 Hall A Vacuum System The Hall A vacuum system consists of 5 separate but interconnected subsystems The largest is designed to supply the Hall A HRS with a self contained 5 x 1076 Torr vacuum that enables both spectrometers to be pumped down from atm in a few hours The target vacuum system is designed to maintain a 1 x 1076 Torr in order to minimize contamination and provide an insulating vacuum for the cryo target Rough insulating vacuum for the 4 superconducting magnets is provided by a 360 cfm Roots type blower that can be connected to each magnet The beam line vacuum is maintained by 12 5 ion pump system used in the accelerator ring and a small turbo pump located near the target The final subsystem is a differential pumping station located near the target exit port Spectrometer Vacuum System The spectrometer vacuum system is shown in Figure 4 5 Vacuum for the HRS is supplied by an Alcatel 880 s Turbo pump backed by a Balzers 360 cfm Roots type Blower This Blower via a special manifold also supplies the roughing vacuum to the HRS at the Dipole Inlet Transition The first Turbo is mounted on the lower side of the Dipole entrance transition The roughing port is also located on this transition on the top side The upper turbo is located on the lower side of the window transition Vacuum readouts and interlock outputs are supplied by five 5 HPS series 421 Cold Ca
232. or at maximum high voltage and thus at maximum gain As such they can suffer damage if a sudden light leak develops In testing we verified the extreme sensitivity to minute light leaks even across the whole length of the structure because of the mirrored surfaces inside the enclosure With 26 PMTs operating at maximum gain and viewing effectively a giant mirror sealing the enclosure against single photon penetration requires extra care during initial testing and operations The PMTs chosen for the counter were Burle model number 8854 127 mm pho tocathode diameter The PMT amplification electronics have been described in Refs 14 15 The dynode chain incorporated a 600 kQ resistance between the cathode and first dynode instead of the nominal 300 kQ This generates Vayn 885V across the cathode to dynode gap thus increasing the photoelectron collection efficiency and peak to valley P V ratio This modification has been proven successful in increasing the PE collection efficiency and the single PE resolution The dynode amplification chain also incorporates a 11 resistor in series with the metal shield to eliminate the possibility 15QOptitron Inc 23206 S Normandie Ave 8 Torrance CA 90502 USA l6Burle Industries Inc 1000 New Holland Ave Lancaster 17601 USA CHAPTER 5 HRS DETECTORS 168 FIG 1 Figure 5 17 Schematic diagram of the aerogel Cerenkov counter as viewed by the incoming part
233. or field shaping purposes There are 368 wires per wire plane which act as signal wires Thus each spectrometer is instrumented with 1472 channels of LeCroy 1877 multihit Fastbus TDCs These TDCs are located in a Kinetic Systems F050 Fastbus crate with a BiRa FB8189 4 power supply located on the main level of the spectrometer space frame in the detector hut The connections between the pre amp discriminator cards mounted on the VDCs and the TDCs are made with 16 conductor twisted pair cables Clip on ferrites are used to filter noise A connection schematic is posted on the side of the rack holding the Fastbus crate on the space frame in the detector hut Power up Procedure 1 ensure gas flow has been established in the chambers as previously outlined If it has not STOP RIGHT HERE Gas flow must be well established and steady state BEFORE the HV may be enabled 2 Ensure that all power supplies as well as the Fastbus crate are off and then connect the LV HV and TDC cables 3 enable the LV Set points are clearly labeled on the face of the power supplies Note that they have overcurrent setpoints and some fine adjustments over the first 30 minutes after a cold start power up may be required Appropriate LEDs should all be active on both the power supplies and the pre amp discriminator cards 4 slowly steps of no more than 300 V ramp the HV to its nominal set point of 4 00 kV using either the manual or the remote controls While the tri
234. or negatively charged particles as needed by any particular experiment The support structure includes all system elements which bear the weight of the various spectrometer components and preserve their spatial relationship as required for 45 vertical bending optics The alignment and positioning system includes all the elements which measure and adjust the spatial relationship The support structure consists of the fabricated steel CVS revision Id hrs 1999 tex v 1 1 2003 06 06 15 44 08 gen Exp Authors J LeRose mailto lerose jlab org 101 CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS Momentum Scattering Angle Transverse Position Shi el d Solid Angle msr House Momentum gt Extended Targets Kinematical Flexibility Momentum Range Angular Range 27 Detector System oo ee 11 5 96 Figure 4 1 A side view of the Hall A HRS spectrometer 102 CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 103 Personnel and Cable Access Truck Access Ramp E 11 5 96 Hadron Arm Figure 4 2 A bird s eye view of the Hall A end station at TJNAF components which support the magnets detector shield house and associated equipment It is composed of the box beam which supports the outer elements in fixed relative position atop the dipole the dipole support bracket upon which the dipole rests on the jacks the cradle upon which the dipole rests through the vertical positioning system
235. orce WARNING After each removal of any components of the counter check for light leaks before turning the HV on at operating values Even a small light leak can destroy the PMTs if they are at 2 950 V Check for light leaks with lights out using a small portable light and reduced voltage around 2 000 V CHAPTER 5 HRS DETECTORS 177 5 6 The Focal Plane Polarimeter 1 5 6 1 Overview The focal plane polarimeter measures the polarization of protons in the hadron spec trometer detector stack When the protons pass through a carbon analyzer the nuclear spin orbit force leads to an azimuthal asymmetry in scattering from carbon nuclei if the protons are polarized The particle trajectories in particular the scattering angles in the carbon are determined by pairs of front and rear straw chambers a type of drift chamber As shown in Figure 5 24 the front straw chambers are separated by about 114 cm and are located before and after the gas Cerenkov detector The second chamber is followed by scintillator 2 which is in turn followed by the polarimeter carbon analyzer The rear chambers chambers 3 and 4 are separated by 38 cm and are immediately behind the carbon analyzer Rear Straw Chambers Gas Cerenkov Aerogel DE Carbon Analyser NA max 51 cm x Front Straw d Chambers Figure 5 24 Schematic of the hadron detector stack The carbon analyzer consists of 5 carbon blocks Each
236. ors and the hall leader When you come on shift the GUI is probably already running If not you may start it by logging onto adaqs2 as the adaq account cd to home adaq ACCOUNT and type atable It is a fairly obvious GUI but there is also a help button which explains everything 7 1 5 Terminal Servers There are four DEC server 200 MC terminal servers in Hall A one in each of the two spectrometer detector huts and two near the beamline These servers allow you check and to modify the detector HV as well as the NVRAM of the frontend DAQ computers The servers may be accessed through dumb terminals connected to any CEBAF terminal server e g the VT100 style terminal in the middle room of the counting house The table entitled Terminal Service for DAQ shows the ports connected for spectrometer and beamline DAQ http www jlab org adag halog html logdir html CHAPTER 7 DATA ACQUISITION AND TRIGGER 221 7 2 Trigger Hardware and Software 2 The Hall A trigger was designed by the University of New Hampshire Here we give a brief overview of the hardware arrangement the logic of the trigger and the usage of the software control Diagrams of the hardware layout are shown in three accompanying figures for the E arm H arm and coincidence circuit Scintillators make the main so called S Ray trigger in each spectrometer arm and a coincidence is formed between the spectrometer arms The S Ray trigger is formed by requiring
237. ov counters gas and Aerogel In addition a proton polarimeter is installed in the back of the detector package to measure the polarization of the proton using a segmented carbon analyzer up to 60 cm in thickness to allow measurements over a wide range of proton energies pair CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 105 Straw Chambers HDC s d M 2 Shield House AQAA SSS DX We rir Carbon Analyzer EELS Scintillator 2 co 2 Cerenkov Aerogel Cerenkov Scintillator 1 Vertical Drift Chambers 1 7 96 Figure 4 4 The hadron spectrometer detector stack CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 106 of front and a pair of rear straw chambers determine the incident and scattered angles respectively The third scintillation counter located at the rear end provides the trigger for the polarimeter The polarimeter detectors are dimensioned to accept a 20 cone of scattered protons Several support systems are necessary in addition to the basic components mentioned above They include gas supply systems for the wire chambers high voltage supplies readout electronics a second level trigger software for data analysis and testing and a remotely controllable mechanical system As for the electron spectrometer all detectors are mounted on a single rigid carriage along with their associated electronics The FPP components are mounted on an FPP subframe for instal
238. p current is set to 10 uA do not allow the chambers to draw more than 1 uA during the ramping procedure or serious damage may result If the power supply trips during the ramping procedure you are moving too fast Rezero things and begin the procedure again NEVER USE THE AUTO RESET FUNCTION If the power supply trips again STOP IMMEDIATELY AND INVESTIGATE CHAPTER 5 HRS DETECTORS 142 5 enable the Fastbus crate Appropriate LEDs should all be active 6 check for poor signal connections evidenced by hot wires wires counting extremely fast or dead wires wires with no counts using the histograming software and cosmic rays Remake any connections as necessary by first powering down the Fastbus crate If at all possible the HV and LV power supplies should be left on continuously if and only if gas is available to the chamber This avoids time loss to reconditioning and maintains the desirable steady state operating condition 5 2 3 Handling Considerations The VDCs are very delicate devices which are absolutely essential to the instrumentation of the Hall A spectrometers Thus extreme care must be exercised whenever they are moved or used e Before moving a VDC detector package ensure that the protective plates are in position Plates include tapped aluminum sheets to be bolted over the entrance and exit aperatures as well as aluminum sheets which slide in between the two chambers e Disconnect and reconnect all TDC cables with e
239. pon receiving the broadcast every IOC in that network searches its database to determine if it contains the record name being sought The IOC holding the requested record responds to the query establishing a connection with the querying process The interface provided by the IOCs to access their record database is geared towards efficiency and not human friendliness Two reasons dictate this choice minimization of CPU overhead due to interface management and the fact that the system is distributed Operator access to the record database of a given IOC is through a Graphical User inter face GUI process executing in a UNIX based computer The standard distribution of EPICS comes with a Motif based implementation of such GUI the so called MEDM It is possible to also implement a GUI to the IOCs using the Tool Command Language TCL with X11 extensions TK i e TCL TK Such implementation is used for example by the Hall A cryotarget system There can be many instances of these GUIs executing in the same computer as well as in several different computers i e the GUI processes are also distributed Each of these GUI processes can access multiple IOCs simultaneously and within each IOC all or a subset of the database records The computers where these GUIs execute are referred to as the OPI Figure 6 1 shows a schematic view of the present Hall A controls layout Exchange of signals between Hall A and other JLab control systems takes place through
240. proportion by a mixing system and this mixture is passed through a bath of isopropyl alcohol which is maintained at a fixed temperature See Figure 5 31 for a schematic diagram of the gas supply mixing system The gas mixture is delivered to gas distribution racks in the Hadron Spectrometer and the Electron Spectrometer The transmission lines and the distribution plumbing have been designed as if the FPPs and VDCs were actually independent systems using different gas mixtures This design was chosen in order to ease the expected transition to such a system in the future Also supplied is a source of purge gas currently pure argon The distribution racks provide for each detector selection of either operating gas or purge gas flow control and metering overpressure relief to protect the detector components exhaust flow measurement and backflow prevention Bulk Gas Supply The bulk gas supply consists of two bottles each of Argon Ethane and Carbon Dioxide Except for fittings which vary by type of gas the three supplies have identical plumbing One bottle of each gas will be on line during system operation while the second bottle serves as a ready reserve connected to the manifold but valved off The two bottles are connected through check valves and manual valves to a high pressure manifold The pressure in this manifold is sensed by a pressure transducer whose signal is available to the slow controls computer for monitoring The pressure is
241. pter 7 Data Acquisition and Trigger 7 1 Spectrometer Data Acquisition The Hall A data acquisition uses CODA 18 CEBAF Online Data Acquisition a toolkit developed at Jefferson Lab by the Data Acquisition Group We have one fastbus crate in the electron spectrometer and two fastbus crates in the hadron spectrometer The fastbus modules are of the following types 1 LeCroy model 1877 TDCs operating in common stop with 0 5 nsec resolution for our drift chambers and straw chambers 2 model 1875 TDCs operating in common start with 0 1 nsec resolution for our scintillators and trigger diagnostics and 3 model 1881M ADCs for signals from scintillators Cerenkov and leadglass detectors Event driven readout of our beam position monitors and raster current is available from VME systems The trigger supervisor is a custom made module built by the data acquisition group Its functions are to synchronize the readout crates to administer the deadtime logic of the entire system and to prescale various trigger inputs We have two trigger supervisors one in each spectrometer This allows us to run the spectrometers independently if needed Use the public account adev for running runcontrol and use adaq for other online software including ESPACE On the directory tree of an experiment is adaq EXPERIMENT which is organized in subdirectories of various tasks such as scaler display ESPACE and other online codes all o
242. pushbutton circuit automatically re arms after ample pressure is detected by the pressure switches PS 111 112 113 These switches are located immediately above gauges PG 131 132 and 133 Just below these gauges are overpressure relief valves RV 121 122 123 which have been set to release if the supply pressure exceeds about 60 psig After passing through check valves which prevent backstreaming the three gas supplies enter the mixing system 5 8 2 Gas Mixing Station The gas mixing system works by metering three gas supplies into a common mixing tank The mixture is then bubbled through alcohol in a tank within a small refrigerator which has been modified for safe operation in a flammable gas system Because the gas flow not the pressure is regulated by the metering system pressure switches have been installed to monitor the mixer outlet pressure and provide feedback to the flow control system The mixing bubbling and pressure control systems are all built into the same relay rack They are collectively referred to as the Gas Mixing Station A flow diagram is shown in Figure5 31 Mass Flow Control System The flow rate of each component gas is controlled by a mass flow controller which delivers a constant mass of gas per unit time Tylan General model FC 280AV The mass flow is independent of pressure although a minimum differential pressure across the controller is required for proper operation The valves are factory calibrated
243. r a prolonged time you must shutdown before the UPS fails For all computer problems you may call Robert Michaels x7410 unless you happen to know another expert who can solve your problem If Michaels is not available call Ole Hansen x7627 or Javier Gomez x7498 7 1 2 Beginning of Experiment Checkout This subsection describes the checkout of DAQ and trigger needed before an experiment can start 1 First ensure that all the fastbus VME CAMAC and NIM crates are powered on They should boot up in a functional state except for heavily loaded fastbus crates that sometimes lose their NVRAM If that happens call R Michaels 2 You may download a default trigger following the directions in the trigger chapter If the hadron momentum changes you may need to set a new delay A trigger expert should do the start of experiment trigger checklist 3 Make sure the HV is on for all detectors and that the values are normal 4 Start the xscaler display following the instructions below and check that the rates from detectors are normal 5 Startup runcontrol CODA using the directions below and start a run With the trigger downloaded and the HV on you are taking cosmics data typically at a rate of 3 Hz per spectrometer Examine the data using dataspy dhist and ESPACE as explained below Compare the plots and printouts to normal values 7 1 3 Running CODA This section describes how to run CODA for the spectrometer DAQ There are
244. r local coordinate system 7 Analyze geometrical position of the golden track point on the detector plane and cluster centers in order to determine the main cluster and to set its parameters and identifier Energy deposition E X and Y coordinates of the shower center are calculated by the formulas B 4 X uwE e icM icM icM where 2 number of detector block included in the cluster M set of blocks numbers included in the cluster e energy deposition in block 7 of detector r y X and Y coordinates of center of block i of detector The shower cluster reconstruction algorithm described above has been implemented by the ESPACE analysis subroutine tot shower A complete description of the program as well as information about the ESPACE routines and kumac files used to perform the analysis photographs of the detectors and more information can be found at the URL 10 D http www jlab org armen sh web page welcome html CHAPTER 5 HRS DETECTORS 165 5 5 Aerogel CherenkovCounter 5 5 1 Overview Each High Resolution Spectrometer detector package includes a single silica aerogel Cherenkovcounter of the compact reflection mirror design which was dictated by the available space 36 3 cm along the incident particle direction In addition the high singles rates expected in Hall A are better handled with segmented detectors covering the focal plane which requires short pulse decay times
245. rature x z deg C 31 1 31 1 gain 10 INMR probe forward data 1 000 100 5138 2 000 200 9695 3 000 100 13830 4 000 150 17611 5 000 0 21096 6 000 200 24340 3198 000 100 7051626 3199 000 150 7058284 lend forward start backward 3199 000 50 5160 3198 000 50 9730 2 000 100 7052428 1 000 50 7059066 lend backward 2 4 27 Integral ioc reboot One of the VME boards PMAC s motor board has its own internal boot process trig gered at power on time So the usual boot procedure red push button on the ioc or reboot command through the network is not sufficient to make sure that the integral VME is correctly initialized Thus boot the VME by switching the AC power of the CHAPTER 2 BEAMLINE 53 VME crate OFF and ON The AC power switch is located in the lower part of the crate front panel 2 4 28 Details on temperatures The AC system of the shed is made of two cooling units a heating unit and a controller connected to two temperature sensors one located in the shed and one located in the BSY This system is programmed in such a way that the temperature of the shed fol lows the BSY temperature within 2C The BSY temperature can be anywhere in the 18C 35C range regardless of the season The BSY temperature and the shed temper ature are given in F by a display panel located close to the workstation on the wall The AC system can be set in manual control by turning from auto to manual a
246. rea are metal Hazards of Vacuum Systems Hazards associated with the vacuum system are due to rapid decompression in case of a window failure Loud noise can cause hearing loss To mitigate the hazard all personnel in the vicinity of the large chamber with a window are required to wear ear protection when the chamber is under vacuum Warning signs must be posted at the area The scattering chamber is equipped with a large 10 mil aluminum window that allows the spectrometers to swing from 12 5 to 165 on the EA and 12 5 to 140 on the HA In order to protect this window when the Hall is open lexan window guards are installed At the inlet of the sieve slit a Moller 8 diameter 7 mil kapton window is provided to separate the target chamber from the spectrometers Finally under the detectors a 4 mil titanium window is provided Eventually this will be replaced with a low mass mylar kevlar window The 1 Z s vac ion and the cold cathode gauges operate at several KV consequently there is also a shock hazard Additionally all vacuum vessels and piping are designed as pressure vessels 4 1 3 The High Resolution Spectrometer HRS The HRS is composed of three superconducting quadrupole magnets Q1 Q2 and Q3 and one superconducting dipole magnet The large quadrupoles were manufactured for TJNAF by SIEMENS the small quadrupole by SACLAY while the dipole was built for TJNAF by WANG NMR The quadrupole magnets are referred to as Q1 Q2 and
247. ream window of the cells are made of 0 03 to 0 045 in thick 3004 aluminum Coors beer cans in a former incarnation all the final ones are above 0 035 in There are two cells soldered to each cell block one 15 cm long and one 4 cm long Both cells have an outer diameter of approximately 2 5 inches The upstream windows of the cells are made from 0 0028 in thick 5052 aluminum These windows are soldered to 1 75 in diameter 0 065 in wall upstream window tubes which are in turn soldered to the cell block Since all the components are made of aluminum it is necessary to plate them before soldering The final components were copper plated before assembly The cell block components have been pressure tested hydrostatically at Jefferson Lab We chose the thinnest beer cans for the pressure burst test Results are listed in the summary table Upstream windows have been tested to similar pressures Finally the entire completed cell block assemblies were pressurized to 85 PSID with helium gas A summary of the testing program to date is presented in Table 3 1 Pressure Relief The gas handling and controls systems have been designed to prevent excessive pressure build up in the system in order to protect the target cells from rupture CHAPTER 3 TARGETS 74 Object P PSIG thickness in size test method Can 55 0 003 short test J ig D estructive Can 80 0 0035 short J D Can 80 0 0035 long J D
248. reen An example of file mapping 7 data is given below EPICS was not responding for the P S readback and set the real current CHAPTER 2 BEAMLINE 57 was 90A ARC magnetic measurement mapping data file version 1 Idate SAT JUN 12 04 49 40 1999 SAT JUN 12 05 41 32 1999 1460 00 50 20 00 460 00 46 20 00 460 00 50 20 00 temperature x z deg C 29 8 30 2 temperature x z deg C 31 7 32 0 temperature x z deg C 28 4 28 2 temperature x z deg C 28 6 28 2 ltal nbr pts 146 linitial amp final NMR probe 2 2 Zm mm B NMR 1 NMR flag local crt Vadc crt set A crt rdt A 0 00 0 1770036 1 1 92 19 0 04 0 00 1460 00 0 1770068 1 1 92 19 0 04 0 00 1440 00 0 1770157 1 1 92 19 0 04 0 00 1439 99 0 1770756 1 1 92 19 0 04 0 00 1460 00 0 1770665 1 1 92 19 0 04 0 00 0 00 0 1770044 1 1 92 19 0 04 0 00 lend Note 1 is the normal status for NMR lock and NMR stability flag The lines 4 5 and 6 of the header give the data entred by the operator The result is a map from 1460 to 1460mm with an uniform 20mm step size This input is the standard one for the needs of ARC CHAPTER 2 BEAMLINE 58 2 5 Fast Raster 1 The beam is rastered on target with an amplitude of several millimeters to prevent overheating The raster is a pair of horizontal X and vertical Y air core dipoles located 23 m upstream of the target The raster has been used in two different modes sinusoidal and amplitude modu
249. ripped by this switch Manual operator intervention is then required to re establish gas flow Pressure control of the inert gas supply used to purge the detectors is provided by a conventional single stage regulator PR 301 mounted inside the delivery rack This regulator receives 45 psig inert gas the same gas delivered to mixer flow channel 3 and provides 15 psig gas to the INERT supply line to Hall A 5 8 3 Gas Delivery into Hall A Between the gas shed and the two Hall A shield houses are several gas line runs of about 700 feet in length These are shown schematically in Figure 5 34 Three gasses inert VDC and FPP are supplied to the Hadron Arm through 1 2 inch OD polyethylene tubing Two similar tubes are teed into these near the beamline entrance to Hall A and they supply VDC and inert gas to the Electron Arm shield house The pressures in all of these lines is nominally 15 psig Distribution in the Shield Houses Inside each shield house there is a gas distribution panel which controls the gas flows to the individual wire chambers in that detector stack Figure 5 34 shows a diagram of the shield house gas systems Each gas supply is first filtered and fed to a visual pressure gauge PG 401 A B and PG 501 A B C so that the supply pressure can be locally verified Inert gas for purging detectors and operating gas either VDC or FPP gas is manifolded to a series of three way valves one for each detector flow circuit These valves
250. romatic 7 perform a scan test in achromatic at 5uA gt solve the trips gt final adjustment of gains of scanners 1 and 2 gt save the last non saturated scan 8 if everything is OK ask for dispersive beam 5uA 9 check dispersive beam CW 5pA Fast Feedback ON Energy Feedback ON important Kresting ON arc s quads and steerers OFF beam stable at entrance and exit Bscope see the test plane of the dispersive mode in MCC 10 perform a scan in dispersive at 5uA see details below solve the trips CHAPTER 2 BEAMLINE 33 finish the 4 gains adjustment perform and save 3 good scans 11 perform a field integral see details below 12 restore beam for the experiment unmask the diagnostics restore achromatic mode and chicane quit MEDM and turn both HV channels OFF 13 analyze scan data dispersive only and integral data 2 4 3 Preliminary details about MEDM To fill or update an input field of MEDM put the mouse cursor in the field do the edit or change and then PRESS CARRIAGE RETURN WHILE THE CURSOR IS STILL INSIDE THE FIELD 2 4 4 Details on pulser check A pulser is used to trigger the scanner acquisition The ARC scanner s pulse generator middle counting room must be adjusted on 1000Hz for CW beam on external trigger in pulsed mode for any scanner Check the output with a scope Settings for CW mode frequency 1KHz delay not important in CW should be always
251. rror of about 0 04 degrees or 0 006 mm CHAPTER 3 TARGETS 99 15 Check again the encoder value reading if it is still 27361 rotation or 17301 up down you are OK otherwise you must remove the encoder and repeat the op erations from the step 9 When the value is correct you can remount the shielding 16 Re connect the cables 17 Turn the system on 18 Check if everything is OK by moving the target up down and CW CCW if ro tation is enabled and watching the encoder reading values which must change consequently if everything is OK then there is no need of a new calibration and the system can work again otherwise you must understand which one of the above steps has failed and go back to that starting point The water pump computer control does not work Check the following items e The switch above the MacB monitor must be in the ON position e The switch on the back of the MacB rack in the counting room must be in the REMOTE position e The pump speed switch in the front of the right rack in Hall A must be in the REMOTE position e The pump speed knob in the front of the right rack in Hall A must be at 60 notice that this knob should not be moved it controls the maximum speed of the water 10 pump 10The scale is in 96 CHAPTER 3 TARGETS 100 3 5 Polarized He Target 7 CVS revision Id pol he3 tex v 1 2 2003 06 06 17 12 31 gen Exp Chapter 4 High Resolution Spectrometers HRS 4 1 O
252. rs electron HRS calorimeter FPP hadron HRS calorimeter when installed and various beam line systems like the ARC energy measurement system The beam line IOC hallasc12 is reserved at this time for Hall A application testing and development There are other specific purpose IOCs located in the group of elec tronics racks next to the beam line The reader is referred to the specific description of those systems and related instructions elsewhere in this OPS manual There are several Hall A controls related IOCs and computer systems outside the hall Some of them are specific purpose systems described elsewhere in this manual like the 9th magnet Bdl IOC and associated ARC workstation located inside the 9th magnet shed and they are described elsewhere in this manual The others are briefly described below Hallascl7 is located in the gas shed It monitors the supply of gas used by the tracking chambers i e VDCs and FPP chambers If necessary 17 can be re booted by pressing the RESET push button located in the IOC front panel Hallasc5 is located in the electronics room of the Hall A Counting House middle room in the same VME crate than hallasc9 Hallasc5 monitors signals associated with Hall A beam current It can be reset by pressing the RESET push button located in the IOC front panel The remaining computers and X terminals associated with the Hall A controls are used as OPI and or boot servers for the IOCs One of
253. rs to the Hall A counting house and information on all the HRS magnets is available on the HRS control screen located in the center of the main console The control of all magnets is described in a following Subsection The power supplies for the magnets are located on the gantry balcony adjacent to the magnets The supplies are all cooled with LCW The front panels of the power supplies are interlocked Under no circumstances should the front panel of any supply be opened by anyone other than authorized per sonnel There is a keyed electrical interlock located in the Hall A counting house main console to prevent the power supplies from being energized at inappropriate times There are also signs posted listing the dangers of high magnetic fields The control interface for the power supplies is available through the HRS control screen in the Hall A counting house Personnel In the event that problems arise during operation of the magnets qualified personnel should be notified This includes any prolonged or serious problem with the source of magnet cryogens the ESR On weekends and after hours there will be a designated individual on call for magnet services Any member of the Hall A engineering group is qualified to deal with unusual magnet situations but in the event of serious problems the technician on call should be contacted Quadrupole Magnets The quadrupoles provide some of the focusing properties of the spectrometer and to a large
254. rst encounter the tracking detectors to minimize the multiple scattering contribution to the angular and energy resolutions of the spectrometer The tracking part consists of two identical vertical drift chambers The trigger detectors include two planes of thin plastic scintillator counters gas and aero gel Cerenkov counters and a shower counter On the hadron spectrometer the shower counter or large scintillator counter can be used in the trigger Particle ID is provided by several techniques For electron identification the electron arm EA has the gas Cerenkov counter and two layers of a segmented lead glass shower counter Because the hadron arm HA also can be used for experiments with electrons it is equipped with a short ver sion of the gas Cerenkov counter and one layer of a segmented lead glass shower counter Pion identification in both spectrometers relies on an aerogel Cerenkov counters which presently have aerogel radiator with a refraction index n of 1 025 Aerogel Cerenkov counter commissioning is not yet completed For particle momenta below 800 MeV c the dE E in the scintillator and shower counters can be used for separation of pions and protons The large distance between planes of the trigger scintillator counters 2 3 m allows a direct measurement of the particle speed with resolution sigma of 0 07 Measurement of the time of flight on the long path from the target to the spectrometer 25m provides another powerful partic
255. ry is adequate the MCC will unlock the second entrance gate allowing the sweep monitors to enter the hall Once the sweep monitors pass through the second gate they close the gate and ensure it is locked The sweep monitors then proceed to the hall entrance where one sweep monitor is left to guard the entrance and the other begins the sweep During the actual sweep the ARM walks through every area and secluded workspace in the hall to ensure that no one could be left inside when the Personnel Safety System moves from the sweep state to controlled access power permit and finally beam permit state Once he checks an area he arms the run safe box in that area After all areas of the hall have been checked and the run safe boxes armed the sweep monitors will return to the entrance where the sweep began Before arming the last run safe box the ARM will contact the MCC Upon contact the MCC will check to see if the sweep has dropped if all is well he will notify the ARM that it is okay to arm the box Once the box is armed the sweep monitors have 30 seconds to exit both gates or the sweep will drop and the entire sweep process will have to be repeated After exiting the ARM must contact the MCC to let them know the Hall can now be moved to the controlled access state 1 2 3 Controlled Access Controlled Access is the state of the PSS when delivery of beam and or RF power is not permitted but the hall is considered a controlled area In this s
256. s otherwise they would not be compressible and the gaps can allow light all the way into the PMT if they are aligned The collet nut is placed first around the light guide and the successive layers of the moulded collets are then placed around the light guide one should make sure that enough free length of exposed light guide remains to enter the housing to slightly compress the PMT and base assembly as in the case of the 2 base Once the slight compression of the spring loaded PMT socket assembly is verified the set of collet rings is moved to enter the housing and rest firmly against the snap stop ring inside the front tubular housing Then the collet ring is screwed in using the special tool until the light guide is firmly bedded in the housing and cannot be moved in or out The remaining procedure is the same as that of the 2 base Due to the two diameter shape of the 5 PMT and its mu metal shield insertion of the PMT pins into the socket is a blind operation It has to be done by feel and experience the pins can only go in a specific PMT socket geometry and it needs experience to learn when the correct alignment has been achieved Let someone who has experience do it bending of the socket pins at the base of the PMT results in destroyed PMTs and they are expensive WARNING The plastic insulator sleeve inside the front tubular aluminum housing should be in place BEFORE the mu metal shield PMT assembly is inserted Failure to assure
257. s system be maintained at a temperature above that of the alcohol bubbler Because gas in the Hall A chambers is at about 1 atmosphere absolute pressure while that in the bubbler is at twice this pressure the dew point for the gas in the chambers is lower than the bubbler temperature The bubbler system consists of a refrigerator a bubbler tank a cold reservoir a warm reservoir and a fill tank A float valve automatically maintains the liquid levels in the bubbler tank and the cold reservoir Alcohol enters the bubbler tank only from the cold reservoir so that its temperature has already been established The warm reservoir sitting above the refrigerator is equipped with a sight glass and serves as the main on line alcohol storage vessel When the level of liquid in this tank becomes low it must be manually refilled from commercially supplied bottles using the fill tank The refrigerator used to maintain the alcohol bubbler temperature has been modified specifically to make it safe for containing flammable gasses and liquids Filling the alcohol reservoir is not trivial Please refer to and carefully follow the procedure detailed in section 3 3 2 Adding Alcohol Delivery Pressure Control Gas will be metered to each detector element through a needle valve To achieve a constant flow through a needle valve a constant differential pressure must be maintained across it so it is necessary to provide a fairly constant supply pressure out of the mixing
258. s tuned to the fundamental RF frequency of 1 497 GHz of the beam 1 The standard difference over sum technique is then used 2 to determine the relative position of the beam to within 100 microns for currents above 1 uA The absolute position of the BPMs can be calibrated with respect to the scanners superharps which are located adjacent to each of the BPMs IHA1H03A at 7 353 m and at 1 122 m upstream of the target The schematic of the readout electronics is shown in Figure 2 4 The position information from the BPMs can be recorded in three different ways CVS revision Id bpms tex v 1 3 2003 06 06 15 19 02 gen Exp Authors A Saha mailto saha jlab org CHAPTER 2 BEAMLINE 27 1 The averaged position over 0 3 seconds is logged into the EPICS database 1 Hz updating frequency and injected into the datastream every 3 4 seconds unsynchronized but with an orientative timestamp From these values we can consider that we know the average position of the beam calculated in the EPICS coordinate system which is left handed 2 Approximately once a shift or more often if requested by the experimenters a B scope procedure 3 can be performed using the same EPICS electronics which then gives the peak to peak variation of the beam 3 Event by event information from the BPMs are recorded in the CODA datastream from each of the 8 BPM antennas 2x4 from which the position of the beam can be reconstructed However these raw v
259. s wrapped on the inside wall of each heat exchanger The maximum power available to each heater is 500 W The heater has a DC resistance of 26 and two heaters in parallel are driven by a 150 V 7 A power supply The current and voltage supplied to this heater are monitored by the control system and there is a software power maximum enforced on the power setting of this heater The heater is connected to the outside world by 18 gauge stranded wire with Kapton insulation Resistors There are two Allen Bradley and four Cernox resistors immersed in each target loop These resistors provide temperature measurements of the target fluid The temperature controllers that read them use a current of less than 30 uA to excite them they are excited with a constant voltage which for our resistors is on the order of 30 mV The Cernox resistors are connected to the outside world with quad strand 36 gauge phosphor bronze wire with Formvar insulation The Allen Bradley resistors are wired with 30 gauge Kapton insulated copper stranded wire Target Lifter There are two AC servo motors which provide the power to lift the target ladder These motors are powered by three phase 208 V power and are equipped with fail safe brakes the brakes are released by a 24 V DC control voltage and 50 to 1 gear reducers On power up there is a delay relay that insures that the motors are always energized before the brakes are released Vacuum Pumps The scattering chamber is evac
260. seen as a comment line by hvplot needs to be changed for other CHAPTER 2 BEAMLINE 36 plotters The rightmost peak high x values was produced by the vertical wire it is a pure horizontal profile the 2 other peaks by the 45deg and 45deg wires 2 4 12 Details on gain adjustment scanners Adjust the gain of the signal amplifier to get 10V 10V at the input of the ADC range 001 002 004 128 256 Gain adjustment in the ARC scanner MEDM window click right button for Arun Saha left one in general on the gain command button located close to the plot of the profile of the scanner you want to adjust Then select a gain and release the mouse After a scan Select higher gain if the rightmost peak is lt 3V in absolute value Select lower gain if the scanner saturates To know if the scanner saturates do not believe the MEDM plot on which several adjacent channels are averaged trust the red diode associated to each scanner close to the plot If you want to know what these diodes look like click on edit on the MEDM access window you will see the diodes Then return to execute Start with the gains dispersive case scanner gain 1 4 3 2 8 3 32 4 32 Note that in dispersive mode the beam is dispersed at scanners 3 and 4 locations so these scanners need a higher gain than 1 and 2 To zoom on a peak change the MEDM parameters of the window edit first de
261. set of switches controlling the cooling units and the heater unit These switch boxes are located on the shed wall If the shed temperature is above 34 4C 94F call Arun Saha the electronics can be damaged and cool down the shed in manual AC mode The 4 temperature sensors of the probe are labelled Tx z Tx z Tx z Tx z depending on their position w r t the following x z frame Door lt Lia D E gt 2 r Saree TZ aS gt Rater are ta gt z PROBE 2 TXx zb 5 4 gt Both x sensors are on the probe edge which is inside the dipole gap and both x sensors on the opposite edge which is outside the dipole gap Both z sensors are at 1 4 of the long dimension of the probe and both z4 at 3 4 of this length The average of the 4 temperatures is used by the analysis program to correct the coil distance from the thermal expansion of the probe so it is important to make sure that the 4 sensors are working well The user can just make sure that the temperatures displayed in arc master adl or recorded in arc integral adl are realistic In arc integral adl they are given in the order Tx z Tx z Tx z Tx z4 Tx z and Tx z4 should be close to the shed temperature Tx z and Tx z depend on the probe position as the gap iron yoke is warmer than the shed and the dipole coil at both ends of the dipole is warmer tha
262. set the corresponding Excess Flow Valve to OPEN RESET wait ten seconds then set the Excess Flow Valve back to AUTO Close both the bottle and manifold valves for the empty bottle Disconnect the empty bottle from the high pressure flex line replace the bottles cap and move the empty bottle to the EMPTIES storage rack Note that ethane bottle fittings type CGA 350 have left handed threads Place a full bottle of gas in the on line rack remove the bottle cap and connect the bottle to the flex line Open the new bottles valve check for leaks at the bottle fitting then re close the bottle valve CHAPTER 5 HRS DETECTORS 205 Adding Alcohol Warning Never open gas flow into the alcohol bubbler without an outlet valve being open As long as the level in the RESERVOIR is such that some alcohol is visible in the sight glass the bubbler will be maintained at its normal fill An effort should be made to prevent the RESERVOIR level from getting too low 1 To fill the RESERVOIR close valves MV 243 and MV 244 to isolate the RESER VOIR from the pressure equalization line 2 Open valve MV 241 to vent the RESERVOIR 3 Remove the cover of the REFILL CANISTER and fill the canister with alcohol Put the cover back on but do not seal it if you seal the cover at this point the flow of alcohol out of the REFILL CANISTER will be impeded 4 Open valve MV 242 to let the alcohol into the RESERVOIR The liquid level can be mon
263. sible gas flow should be continuously maintained even in no beam time periods This avoids time loss to reconditioning and maintains the desirable steady state operating condition If the chambers are not being used in an experiment the flowmeters for the front CHAPTER 5 HRS DETECTORS 184 Ep vac fpp 3 fpp 4 Digital output flowmeters dc flowmeter at side of gas panel for fpp ch3 x planes INput pressure gauges Figure 5 29 Drawing of the gas panel on the hadron detector stack CHAPTER 5 HRS DETECTORS 185 chambers are set to 20 and the flowmeters for the rear chambers are set to 60 When the chambers are used in an experiment the standard setting for the front chambers is 40 and for the rear chambers it is 105 2 Gas pressure at the gas panel on the detector stack should be in the range 13 15 psi With the large leakage rate of the FPP chambers we typically run at near the limit of the capacity of the gas mixer to supply the gas flow demanded by the FPP and VDC chambers Therefore it is possible to demand too much flow rate from the mixer If the gas pressure drops below 13 psi drop the flow to the FPP chambers and contact Jack Segal or Howard Fenker to determine the cause and remedy for the situation The status of the gas handling system should be monitored carefully as well as logged at least once per 8 hour shift Any substantial deviat
264. sion Here we describe the software control of the CAMAC modules involved in the trig ger There are four types of modules that are controlled 1 Discriminators 2 Delay Units 3 Memory Lookup Unit 4 AND OR Modules A graphical user interface called X IrigMang was written by T Smith UNH X TrigMang is used to download the trigger and read back values This GUI reads in a default setup file and with one button called Download All one may load the default setup To start X TrigMang login to adaqh2 as the adaq account then type gotrigger to go to the correct directory which contains the default setup in trigsetup settings and type XTrigMang there For experiments that never change the trigger one only needs to Download All to ensure the trigger is set up after power is turned on for the crates For coincidence experiments it is an ticipated that the only change one needs to make is the delay on the hadron arm to accommodate momentum changes Proton momenta above 360 MeV c are at present accommodated by the hardware it would be a fairly easy hardware change to go lower For coincidence experiments instead of using X TrigMang directly one must download the trigger with a script called trigsetup Login to adaqh2 as adaq account and type trigsetup It asks for the momentum of the H arm under the assumption that a proton CVS revision Id trigger tex v 1 3 2003 06 06 17 19 22 gen Exp 5Authors R Mich
265. sist of six paddles Each S1 paddle has an active area of 29 5 cm by 35 5 cm Each 2 paddle has an active area of 54 0 cm by 37 0 cm The counters are made of 5 mm thick BICRON 408 plastic scintillator and use multi strip adiabatic light guides which end in a long cylindrical spool There is an inlet for optical fiber mounted on the side of the cylindrical light guide Each paddle is viewed by two 2 photo multiplier tubes Burle 8575 The S1 paddles are installed at a small angle to the 6 OVS revision Id scin tex v 1 3 2003 06 06 17 00 27 gen Exp CHAPTER 5 HRS DETECTORS 145 average plane and overlap by 10 mm They are supported from PMT housings The 82 paddles have only 5 mm overlap Paddles are supported right outside the active area to minimize deflection of the plastic scintillator and the torque applied to the mounting of the PMT housing 5 3 2 regime and time resolution High energy electrons passing perpendicular to the S2 detector plane yield about 400 500 photons at the photo cathode of each PMT In a fresh PMT this leads to 80 100 photo electrons On HRS the discriminators have a threshold of 45 mV and a typical PMT has gain 3 109 The HV for a fresh PMT should be in the range 1800 to 2000 V Based on PMT pulse rise time 2 8 ns and photo electron statistics the time resolution is about 0 2 ns The propagation time of the light inside the detector is about 10 ns which needs to be corrected by using track position inform
266. ss Support Structure The lead glass shower counters are mounted on top of the space frame for the detectors Access for servicing the shower counters requires climbing on top of the support frame Only the responsible personnel identified below should attempt to service the shower counter such work requires proper safety precautions and prior training experience The Lead Glass blocks The lead glass shower blocks and tubes weigh approximately 70 80 pounds apiece Lifting replacing or moving such blocks should be done properly to avoid muscle problems and damage to the blocks 5 4 5 Authorized Personnel The following individuals are authorized to work on shower counters Breuer Herbert 301 405 6108 CHAPTER 5 HRS DETECTORS 163 Markowitz Pete x7237 305 348 1710 Segal Jack x7242 Voskanyan Hakob x5105 Wojtsekhowski Bogdan x7191 5 4 6 Software Algorithms The purpose of the shower cluster reconstruction in the Preshower and the Shower de tector is to e Define all clusters of fired blocks which belong to the showers registered in the detector e Calculate parameters of showers in the detector energy deposition of showers X and Y coordinates of the shower center e Set parameters and identifier of the so called main cluster Cluster in the shower detector is determined as follows Cluster is a group of continuous blocks Cluster can occupy a maximum of 6 2 x 3 blocks in the case of Presho
267. ssues The only safety issue concerning the Bremsstrahlung radiator is that of induced radioac tivity in the Cu targets and in the water used for cooling the targets The water cooling system is a closed loop using a portable welding torch water cooler located under the beam line just upstream of the target The cooler is kept in a tray which is intended to provide secondary containment in case of a leak The cooling system must not be breached or drained without concurrence from the RCG Accidental breach or spill con stitutes a radiation contamination hazard A spill control kit capable of containing a system leak or spill is staged by the door to the hall In the event of a spill notify the RCG 2 7 3 Operations Although the radiator foils are water cooled a high current electron beam may melt the foils Beam currents with the radiator will be limited to 30 micro amperes Including a safety factor the raster radii given in Table 1 will limit the temperature rise to 100 C 13 CVS revision Id radiator tex v 1 3 2003 06 06 15 19 03 gen Exp 14 Authors A Saha mailto saha jlab org CHAPTER 2 BEAMLINE 63 Table 2 4 Raster radius as a function of beam current Current uA Minimum raster radius mm 10 not needed 15 0 2 20 0 7 25 1 3 30 2 1 Table 2 5 Encoder voltage calibration See text Position Voltage ratio Vencoder for Vsupply 5 V out limit 0 030 0 15 foil 1 0 102 0 511 foil 2 0 269 1 3
268. t Once the master key is in place each person wishing to gain access must remove a key from this row The MCC will then verify each person s name which key he has and check that each person is wearing the proper dosimetry This key release procedure allows the MCC to keep a count of who has entered the hall After the procedure is complete the MCC will unlock the second gate at the entrance to the hall Please note only one of the entrance gates can be open at a time while in the controlled access state When your work is completed and you are ready to exit return to the entrance gates and press the intercom call switch to notify the MCC Once you have entered and closed the first gate each person must replace his key in the appropriate slot otherwise the Personnel Safety System will not allow the master key to be released When the master key is released place it in its slot and the MCC will unlock the final gate When you have exited the final gate make sure it has closed and locked behind you If circumstances dictate request that the MCC return the hall to the beam permit state and that beam be restored It is important to note that if you need to work in the HRS shield house during the controlled access you must go to the control room in the MCC before the access and get a special key which allows you to arm the run safe box located in the shield house The run safe box inside the shield house will drop from the operational positi
269. t forward 14096 a p Encoder unit per Turn 110 Motor Micro Step Per Step CHAPTER 2 BEAMLINE 38 1200 a p Motor Step Per Turn 12500 a p Screw Pitch Micron 11 a Motor Polarity used for forward displacment begin forward 1 Time Stamp s 0 4093 0 0 002 4093 0 0 007 4093 0 0 007 135163 0 0 002 135163 0 0 002 lend forward 1 Time Stamp s 1305473 1 P 1 5 Current Command Line begin backward 1 Time Stamp s 1305498 135163 0 0 007 135163 0 0 007 4092 0 0 002 4092 0 0 002 lend backward 1 Time Stamp s 1305505 1 2 P 2 5 Current Command Line 1 a p TJ Device Name l 1 p Displacment X dimensionless X beam left 10 p Displacment Y dimensionless Y top vertical Z beam 14 Rod Serial Number 235120 p Fiducial Beam Micron at survey scanner po sition 14 Cartridge Serial Number 181270 a p Cartridge Range Micron 120 Wire Diameter Micron IW Wire Material p Number Wire 120 p Survey Wire Diameter Micron Wire used for above data 1284310 257775 234665 p Fidicial Wire Micron 1 707 0 5 p Differential Fiducial To Wire per micron of wire diam 145 08 44 96 0 p Angle Degree around Z axis 0 when perp to displ 10 0 00315 0 p Differential Angle Degree Per Micron of wire diam 14096 a p Encoder Home 1118407 p Encoder Survey Survey of 11 Aug 98 11 a p Encoder Sign 1 if increase at forward 14096 p Encoder unit
270. t it can handle the mass flow caused by the sudden expansion of its cryogenic contents due to exposure to the heat load A calculation has been performed which models the response of the system to sudden vacuum failure That calculation indicates that the relief plumbing is sized such that the flow remains subsonic CHAPTER 3 TARGETS 76 at all times and that the maximum pressure in the cells remains well below their bursting point The calculation was performed by following methods in an internal report from the MIT Bates laboratory 5 The formulas and algorithm in the report were incorporated in two computer codes and those codes were able to reproduce results in the report hence they represent an accurate implementation of the Bates calculation The calculation can be logically broken into two parts First the mass evolution rate is calculated from geometric information and the properties of both the target material and vacuum spoiling gas The principal results of this first stage are the heat transferred per unit area q the boil off time t and the mass evolution rate w Second the capability of the plumbing to handle the mass flow is checked The principle result of this second step is the maximum pressure in the target cell during the discharge The formula involved will not be repeated readers are referred to the Bates report for detail The information that was used as input to the calculation is given in tables 3 3 3 4 and
271. t the chamber to each HRS The height of the aluminum ring shown is 36 0 in which is designed to accommodate the mounting flanges The stainless steel base ring is 11 50 in in height with one pump out 6 in diameter port and with seven 4 in viewing and electrical feed through ports The base ring will also contain support mechanisms for the solid target ladder assembly a rotisserie for collimating slits radiators and magnetic fingers for removing the solid target vacuum lock can The total height of the top ring middle ring and base ring is 93 81 in This length is partly determined by our desire to include with the cryogenic extended target a solid target vertical ladder secured in an inverted hat through a hole in the base of the chamber The base ring includes an end plate through which the inverted hat will be adapted to fit into the large vertical pipe serving as the pivot post for the Hall A spectrometers The stainless steel cylindrical top hat has 40 0 in inner diameter and is 0 375 in thick and 46 31 in high which is necessary to permit the cryotarget to be withdrawn and to make space available to expose the solid targets to the electron beam The 200 LA electron beam presumably focussed to a 0 1 mm 0 1 mm spot and rastered 5 mm horizontally or vertically on the target enters through a oval hole in the middle ring which is 2 06 in wide and exits through 1 81 in hole connected to the exit pipe 11 CVS revision Id tgtcham tex v
272. tal shield will restrict the current flow through the mu metal shield and the oaf s hands to less than 0 2 mA with 2 1 kV on the base 5 3 9 Responsible Personnel The following individuals are responsible for operation of the trigger counters Segal Jack x7242 Wojtsekhowski Bogdan x7191 CHAPTER 5 HRS DETECTORS 156 5 4 Lead Glass Shower Counters 5 4 1 Overview Electromagnetic shower counters offer a useful means of particle identification PID 8 9 Shower counters complement other means of PID such as time of flight TOF or threshold Cerenkov counters due to the independent physical processes responsible which result in different detector limitations 10 Independent PID allows multiple detectors i e a Cerenkov counter followed by a shower counter to obtain excellent rejection ratios that are the product of the individual rejection ratios Shower counters measure the energy deposited by the incoming particle The de tected light output is linearly proportional to the energy lost by the incoming particle Electromagnetic showers are stopped in the counters whereas hadronic showers due to the longer hadronic mean free path are not Looking at the longitudinal distribution of the energy deposited in the calorimeter differentiates between electromagnetic and hadronic showers and therefore identifies the incident particle Typical pion rejection with a lead glass counter is of the order of 100 1000 1 in the 1 to 1
273. tate people are counted both entering and leaving the hall to ensure that no one is left inside when the Personnel Safety System advances to the RF Permit or Beam Permit states Hall entry during the controlled access state is permitted only to people authorized or qualified CVS revision Id a intro tex v 1 1 2003 06 06 15 26 26 gen Exp Authors J LeRose mailto lerose jlab org CHAPTER 1 INTRODUCTION 12 by Jefferson Lab Entry to and exit from the hall is controlled from the MCC The Hall cannot be placed in the controlled access state without having first been swept 1 2 4 RF Power Permit When the PSS is in RF Power Permit the hall is considered an exclusion area Delivery of RF power is permitted but beam delivery is not Reaching this state requires that the hall has passed through the controlled access state and that no one is left inside the hall This is usually a temporary state bridging the transition from the Controlled Access to the Beam Permit state Once the Personnel Safety System reads Power Permit a steady klaxon sounds in the hall If you are in the hall when this klaxon sounds press the emergency safe button on the nearest run safe box and immediately exit the hall The hall entrance gates are locked at this time but there is an emergency exit button at each gate which will allow you to exit A four minute delay is built in between the transition from RF Power Permit to Beam Permit 1 2 5 Beam Per
274. tate the target to two angles and take note of the encoder values e Write these value on a scrapbook e Select sequentially the 6 targets waterfall and the solid ones and take note of the encoders values e Note ALL the previous and new values in the logbook e Move 3 4 8 Troubleshooting Movement failure automatic shutdown If one of the 4 second level microswitches just after the first level ones is hit during the movement the motor power supply will be turned off immediately If this happens a beeping sound will inform you that the motor movements are stopped and inhibited To restore the operation 1 Recognize the cause of the trouble for example the MacA computer crashed and try to fix it as much as possible in the previous example restart the MacA and the slow control program 2 Remove the inhibit there is a switch in the left side of the left rack switch it in such a way as to turn off the corresponding light then push the green button in the front of the left rack near the emergency button in order to switch off the beeping sound At the same time check that the motors are not moving watch the 2 encoder displays in front of the left rack particularly a new calibration has to be done after the substitution of the complete target castle if the vertical alignment values are changed CHAPTER 3 TARGETS 97 3 Now you can move the motor only manually switch on the 80 volts manual motor power supply th
275. ter reservoir or tank to the target and then back to the tank through stainless steel tubes In order to produce a stable film a gear pump magnetically coupled to a de motor is used A tachometer which is on the pump axis measures the pump speed turn min and a flowmeter which is placed before the entrance of the scattering chamber measures the flow rate The set voltage is also read although it is redundant These parameters can be used to monitor the target thickness stability 3 4 2 gas system The gas system connected with the hydraulic system is designed to pump gas into the waterfall target container to reduce background Normally hydrogen gas is used The gas system is made of a load and discharge tube circuit to allow the removal of the air by flushing the hydrogen into the target cell and the water reservoir Once the system is full the circuit will be closed by electro valves 3 4 3 The movement system The waterfall target and the solid target ladder can by design both be rotated around the central axis of the scattering chamber and be moved vertically to change the target at the beam position This is done by a mechanical system schematically shown in Fig 3 1 which consists of step motors and absolute optical encoders whose precision is 0 1 mm and 0 1 degree For E89003 and E89033 experiments the rotation motion of the target is not required and thus has been disabled to prevent accidental change of the target
276. termine the range in mm on which you want to zoom on the MEDM access window push on edit on the ARC window click anywhere inside the plot you want to change on the Resource Palette go down to Axis Data select it on the Cartesian Plot Axis Data in the X Axis part X means horizontal change Axis Range from auto scale to user specified then edit Minimum Value and Maximum Value to specify the horizontal range you want to look at the unit is mm If you used the edit facility of MEDM it will suggest that you save the changes when killing the window Do not save the changes on the MEDM access window push on execute Short cut push on the right button while the cursor is inside the plot you will access directly to the MEDM axis data menu Other MEDM tricks may depend on the version of MEDM you are running Control middle button vertical drag will scale the plot up or down Shift middle button drag will translate the plot CHAPTER 2 BEAMLINE 37 2 4 13 Details on file save scanners To save the data in a disk file push on Save The software builds automatically a name of the type scan nnn data where nnn is the scan run number incremented automatically The current run number is stored on disk so unless a disk crashes you can reboot the VME or delete a data file without resetting this number Read the run number on the MEDM screen and record the file name in the e logbook The file will
277. that scintillator paddles in planes S1 and 52 both fired and both phototubes in each paddle and that the paddle combinations in 1 and 52 belong to an allowed set A memory lookup MLU decides if the combination is valid The allowed combinations are for S Ray tracks that are at an approximately 45 degree angle with respect to the hall floor with a tolerance of 1 paddle on either S1 or 2 The timing of this trigger is determined by a strobe on the MLU which in most events comes from the right side PMTs of the S2 plane The coincidence is formed in an overlap AND circuit with a 110 nsec window The electron arm singles triggers are called T1 event type 1 in CODA the hadron arm singles are T3 and the coincidences are T5 If T1 doesn t exist a looser trigger called T2 is considered similarly for T3 T4 on H arm This looser trigger requires any hit in 2 out of the following 3 detectors 51 52 and Cerenkov in the case that a Cerenkov detector is used or 1 out of 2 from 51 and 52 if there is no Cerenkov detector in the spectrometer These looser triggers are prescaled and a sample of about 5 Hz from them allows for an accurate measurement of inefficiencies The trigger design is quite flexible and it is relatively easy to add detectors to define new trigger types or to modify existing ones so long as the detector is fast enough The trigger supervisor also allows for the possibility of 2nd level triggers which could be used for a later deci
278. the HV in 300V steps After each step wait for the current to settle below 1 wA then go up to the next level until 1875V is reached Peak currents during turn on should not exceed about 40 uA A 10 V s ramp rate leads to a leakage current of several A Trip levels should be set to 110 LA both for turning on HV and for normal operation so that bad spills do not trip the chambers Current should settle to about a uA or less within a few minutes If the power supply trips during the ramping procedure it is possible that you are moving too fast or that some problem has developed with a chamber Rezero things and begin the procedure again NEVER USE THE AUTO RESET FUNCTION If the power supply trips again STOP IMMEDIATELY AND INVESTIGATE There is probably a problem and expert advice may be needed Some detailed information intended for experts debugging hardware problems is available in the Rutgers web pages 5 Check for poor signal connections evidenced by hot wires wires counting extremely fast or dead wires wires with no counts using the histogramming software and cosmic rays Be careful apparent problems may result from bad demultiplexing rather than from poor signal connections Remake any connections as necessary by first powering down the FASTBUS crate If at all possible the HV and LV power supplies should be left on continuously if and only if gas is available to the chamber This avoids time loss to reconditioning and maintains
279. the X terminals in the counting house is dedicated to the display of accelerator MEDM screens it is automatic no user involvement is required The hac computer is used to gain access to the Hall A control systems Once logged into this computer issue the command HAC_hp if logging was accomplished through a Hewlett Packard computer console or HAC_xt if through an X terminal The Hall A controls main screen shown in Figure 6 2 will appear Follow then the instructions given in the system of your interest 6 0 4 Personnel Responsible If a problem develops with the Hall A controls system page J Gomez at 849 7498 CHAPTER 6 SLOW CONTROLS OPI OPI Xterm 1 Xterm 2 BCM IOC Cryo Monitor IOC hallasc5 hallasc9 Hall A Controls LAN E_detectors IOC 11 Wire Scan E_magnets hallasc 14 BeamLine IOC E_motion IOC hallasc12 hallasc 18 Hall A HV IOC Cryotarget IOC hallasc22 Beam Line Electron Spectrometer JLab LAN Gateway Boot Server hacsbcl OPI Boot Server hac Gas Supply IOC hallasc17 9th Mag Bdl IOC ARC wrkstation 9th Magnet Shed Me ea fad E oh Hall A Gas Shed H_detectors IOC Hall A Cryo IOC hallasc4 iochla2 magnets IOC Hall A Line I
280. the bottle s cap and move the empty bottle to the EMPTIES storage rack Note that ethane bottle fittings type CGA 350 have left handed threads d Place a full bottle of gas in the on line rack remove the bottle cap and connect the bottle to the flex line e Open the new bottle s valve check for leaks at the bottle fitting The corre sponding pressure gauge should now read full bottle pressure CHAPTER 5 HRS DETECTORS 183 f The ALARM state of the Matheson 8590 controller should have automatically reset Check inside the Hall A Gas Shed Each controller should show a green RUN and yellow READY LED lit If not re check the installation of the gas bottle 5 For case 2 the sequence of steps is as follows a Check in the Hall A Gas Shed If all bottles have sufficient pressure each of the Matheson 8590 controllers will have one green RUN LED lit and one yellow READY LED lit If a Matheson 8590 controller shows two red EMPTY LEDs lit and the central red ALARM LED lit both bottles of the corresponding manifold need to be replaced Nothing further needs to be done here go outside to the Gas Bottle Pad b Follow steps 2 through 5 as detailed immediately above for both bottles c The ALARM state of the Matheson 8590 controller should have automatically reset Check inside the Hall A Gas Shed Each controller should show two yellow READY LEDs lit If not re check the installation of the gas bottle Press
281. the exit beam pipe CHAPTER 2 BEAMLINE 62 2 7 Bremsstrahlung Radiator P 2 7 1 Overview The Bremsstrahlung radiator is the last element in the Hall A beam line before the scattering chamber and is about 72 6 cm from the center of the physics targets Its design is based on the Hall C radiator system built by David Meekins and documented in the Hall C operations manual The central component of the system is a U shaped oxygen free copper target ladder with six positions for differing thicknesses of oxygen free Cu foils The ladder is designed so that it never intersects the beam The 3 175 cm wide gap in the ladder is spanned only by the target foils which are 6 35 cm wide 3 175 cm high and 3 332 cm apart center to center A stepper motor moves the target ladder with foils up and down into and out of the beam Hard stops prevent motion of the ladder beyond the limit switches Water cooling of the radiator ladder cools the foils preventing damage from overheating by the beam The interaction of the beam with the foils produces background radiation in the Hall At 3 GeV ion chamber trip levels do not need to be adjusted and increases in detector background rates are minimal further tests are planned for 0 8 GeV No local shielding is installed as calculations indicate that this will not significantly affect dose at the site boundary Any installation and or subsequent modifications must be coordinated with RadCon 2 7 2 Safety I
282. the gradient compensating coils for the field ranges to be measured before trying to make measure ment For studies involving 1096 changes in the field settings the compensating coil current can be set once and left alone Recommended Procedure turn the REGULATOR OFF for all non autopilot field measurements For group 0 probes set compensating coils appropriately see figures Put meter in MANUAL mode with SEARCH OFF Select a probe and polarity Group 0 Probes 0 1 2 negative Probes 3 4 5 posi tive Type in DAC number for the field range being measured see below Select AUTO and wait for a lock positive field reading Verify that you have a good lock by checking the oscilloscope for a clear resonant signal Go back to 2 for the next probe If you have problems see the table listing problems and possible solutions Selecting DAC 7Zs In selecting the DAC to use for the field of interest use either the graph in Fig ure 4 11 or the polynomial below that CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 124 Problems and Solutions Symptom Diagnosis and Cure Weird numbers on displays controls for Need to reboot all magnets fouled up See instructions below NMR Teslameter does not respond to Meter s communications are somehow hung up commands and display shows all zeros Push RESET Will not lock Very high noise level makes resonance hard to find Still will not lock Very high noise level
283. the main Jefferson Lab network JLab LAN Presently the system is in a state of flux as man agement of various portions of the Hall A controls system is being transferred to the CHAPTER 6 SLOW CONTROLS 212 Accelerator Division Controls Group ADCG This might entail future changes in the organization of the Hall A control system like boot servers and IOC task re arrangement A brief description of the present state of the system follows There are three IOCs in Hall A which at the present time are directly managed by the ADCG These IOCs are 10 iochla and iochla2 They are located in the row of racks next to the beam line 10 performs the readout of the Beam Position Monitors BPMs located in Hall A i e those located at Compton region and before the target Iochla handles Hall A beam line tasks like Fast Shut Down FSD logic Moller target motion Beam Loss monitors and ionization chambers Hall A cryogenics distribution and magnet filling level are controlled by iochla2 through a GPIB based network of CAMAC crates This IOC also monitors all spectrometer magnet temperatures during a magnet cooldown The iochla2 signals are available in the Hall A controls network through a dedicated IOC hallasc9 located in the electronics room middle room of the Hall A Counting House Only Accelerator Operations personnel are allowed to reboot and or perform any hardware software changes in iocse10 iochla and iochla2 and the associat
284. thick titanium windows Only members of the Moller polarimeter group should work in this area High Voltage There are 38 photomultiplier tubes within the detector shielding hut with a maximum voltage of 3000 V The detector is serviced by sliding it back on movable rails The high l Home page http www jlab org moller CHAPTER 2 BEAMLINE 67 voltage must be turned off during any detector movement Only members of the M ller group should move the detector Target To avoid damage to the Moller target the target should not be in the beam if the beam current is greater than 5 uA Only MCC can move the target but the experimenters are responsible for ensuring that it is properly positioned 2 8 3 List of Authorized Personnel 18 19 The list of the presently authorized personnel is given in Tab 2 6 Other individuals must notify and receive permission from the contact person see Tab 2 6 before adding their names to the above list Name Dept Telephone e mail Comment JLab Pager Eugene Chudakov JLab 6959 6959 genGjlab org Contact Alexander Glamazdin Kharkov 6378 glamazdiQ jlab org Viktor Gorbenko Kharkov 6378 gorbenko jlab org Roman Pomatsalyuk Kharkov 6378 romanipGjlab org Table 2 6 Moller Polarimeter authorized personnel The primary contact person s name is marked with a slanted font 18 CV S revision Id moller personnel tex v 1 2 2003 06 06 21 12 51 gen Exp 19 Aut
285. thode gauges and seven 7 series 275 Mini Convectron gauges In addition to these there will also be a FIsons Micromass 386 RGA head installed in the system for diagnostic purposes Most of this instrumentation will be located on the Turbo pump manifold for detailed information see Figure 4 5 Powered valves instrumentation and pumps will be controlled and powered at the Vacuum System equipment rack located on each respective spectrometer on the gantry platform Selective equipment will also be controllable from the Hall A counting house Chamber The HRS vacuum chamber consists of an associated vacuum window a sieve slit and Q1 transition Q1 to Q2 transition Spool section Dipole transition Dipole to Q3 transition and the Q3 to exit window assembly The spectrometer vacuum is contained by a 007 kapton window at the entrance and a 004 titanium window at the exit CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 108 ee 4 54 177 VY i ee M DN 7 Interlock 4 X 5 7 69 y 7 I z z z 69 x IPOH X 7 Dipole 7 orm o2 ve P 7 7 SX 71 05 Aw v3 Xo d 5 EAA e f w 72 9 X ES vs o Xo w7 v7 TURBO wb pa Xo w7 ivi Xo w71 v c a orum Figure 4 5 HRS vacuum system CHAPTER 4 HIGH RESOLUTION SPECTROMETERS HRS 109 Target Vacuum System Vacuum for
286. tion motors and therefore contain no brushes and are practically immune to sparking The three phase power for these fans is delivered to them by 18 gauge stranded copper wire with Kapton insulation The maximum current that the fans draw is 5 A for a maximum power consumption of 200 W when pumping liquid hydrogen deuterium The current and voltage drawn by the fans is monitored by the control system Fan Motor Tachometer The fans have tachometer which consist of a coil that views the flux change caused by a permanent magnet attached to the motor rotor The tachometer signals are carried on 22 gauge stranded wire with Kapton insulation This is a low power signal The control system monitors the frequency of the fans Low Power Heater This isa hair dryer style heater it resembles the heater elements found in hair dryers and heat guns that is immersed in the hydrogen The heater is made of 0 0179 in diameter Nichrome wire with a resistance of 1 993 Q per foot wrapped on a G10 carrier board The maximum power available to this heater is 80 W The power for the low power heater is supplied by a Oxford 502 temperature controller The heater lead wire is 18 gauge Kapton insulated copper stranded wire The heaters have a DC resistance of 20 and hence will draw a maximum of 2 A The power supplied to this heater is monitored by the control system CHAPTER 3 TARGETS 72 High Power Heater There are two kapton enclosed incoloy heater foil
287. tor and lead flags for condition visual shorts etc unlock power disconnect switch and turn on AC power turn on both sets of three pole breakers located on power supply visually check power supply for faults A when all faults have been cleared lift lever on lower right side of supply M insure that power supply is in remote control Dipole eS visual inspection of main current leads dump resistor and lead flags for condition visual shorts etc unlock power disconnect switch and turn on AC power turn on power lever on right upper side of supply visually check power supply for faults on supply and at rack when all faults have been cleared insure that power supply is in remote control cctv camera on and focused check power supply for proper polarity NMR gradient compensation for on and proper polarity Hadron Arm Spectrometers cds correct angle not to be used for calculations correct pointing _________ not to be used for calculations collimator operation at 3 positions _ check spectrometer for obstructions to movement check intergen bottles for correct pressure J insure that 15 degree stop pin is installed Vacuum blower on at controls under spectrometer A turbo on at turbo controller in rack 1H71B01 A pump valves open at valve controller in rack 1H71B01 channel 2 gages read 0 mil
288. trometers The close spacing of the shields which is also shown in the photograph of figure 5 19 creates dielectric breakdown problems The j metal shields are at cathode potential 2950 V to avoid the capacitive discharge from a grounded p metal shield to the glass of the photocathode which would contribute to the noise level in the PMT and adversely affect their performance at high operating voltages This necessitates extra precautions in order to avoid dielectric breakdown between adjacent shields and between the shields and the aluminum structure of the counter which is at ground potential The solution was to wrap the outer surfaces of the metal shields with a high dielectric value 12 000 V mm thin 0 254 mm Teflon filmt In addition the PMT housings consist of fiberglass epoxy composites with added inner and outer skins of 0 0254 mm thick Tedlar with a further combined insulating value of 3 000 V Such a combination of insulating materials eliminates any breakdown or small leakage current induced noise and at the same time satisfies all safety requirements The final construction of the counter described in this report is built around the two sides of the main PMT section each consisting of two pieces of aircraft quality aluminum alloy with stiffening aluminum rods formed integrally on the top and bottom The openings for the PMT housings were machined on these structures using CNC milling machines to keep t
289. tside housings under such a condition The plastic insulator ring also serves as a mechanical alignment aid to keep the mu metal shield centered within the front tubular housing Tighten the nylon locking set screw but don t over do it and strip the nylon threads in the process The mu metal shield has a solid friction fit in the copper ring inside the retainer ring to make good electrical contact Screw the base assembly with the PMT and mu metal shield attached back into the front tubular housing up to the half way point of the threads in the coupling nut The PMT socket and dynode chain assembly 15 is spring loaded 16 so one can see how much compression the light guide will induce on this assembly thus assuring a good contact with the PMT without the risk of damage to the latter Insert the collet nut 03 and the inner collet 04 onto the light guide as shown in Figure 5 9 Position the outer collet inside the entrance to the front tubular housing and check that it matches the direction of the cone to that of the outer collet Smear a thin layer of optical grease on the light guide and insert the latter into the inner collet until it makes contact with the PMT This can be verified by observing the movement of the socket against the now slightly compressed springs Insert the outer collet into the inner one and screw the collet nut making sure the springs remain slightly compressed in the process Use the special tool to tighten the collet
290. tween the PMT and the p metal shield Loosen the nut securing the j4 metal shield to the base and carefully apply upward force on the shield while someone else is holding onto the base This will remove the PMT and the p metal shield from the socket and base respectively Replacement of the PMT requires experience because it has to be done with the p metal shield installed in but not secured to the base The PMT pins need to be aligned with the socket pins in a specific geometry thus the insertion has to be done by feel and experience Once the PMT is inserted in the socket the jj metal shield is secured the base with the nut Make sure the shield protrudes past the photocathode as much as the tapered design allows Carefully insert the elastomeric ring between the PMT rim and the p metal shield This ring supports the PMT and prevents it from sliding out of CHAPTER 5 HRS DETECTORS 176 Table 5 3 number of photoelectrons detected as a function of PMT and incident beam location in the end plate proximity configuration X9 P E and X79 P E denotes the measured total number of photoelectrons from six PMTS and the expected total from 26 PMTs respectively The incident electron beam location hit position is represented by x PMT Location and Number of Photoelectrons 1B x 40 1T 0 2 2B 0 8 2T 0 3 3B 0 6 3T 0 1 6 0 7 5 PMT Location and Number of Photoelectrons 5B 0 5 6B 1 0 6T 0 1 7B x
291. two modes 1 The most common is the 1 Trigger Supervisor 1 TS mode which uses one trigger supervisor and is used for coincidence experiments and 2 The 2 Trigger Supervisor 2 TS mode which is used for running the two spectrometers independently The 1 TS mode can also handle single arm triggers but is about 1 2 the aggregate speed of the 2 TS mode When running the 2 TS mode one uses the adev account on CHAPTER 7 DATA ACQUISITION AND TRIGGER 218 adaqs2 for the H spectrometer and the atrig account on adaqs3 for the E spectrometer The 1 TS mode normally uses the adev account on adaqs2 only The information that follows refers to the adev account but the atrig account is quite similar For exam ple for a file like home adev prescale prescale dat there is a corresponding file at home atrig prescale prescale dat Here is how to start and stop a run Normally when you come on shift runcontrol will be running If not see the section on Cold Start below To start and stop runs push the buttons Start Run and End Run in the runcontrol GUI To change configurations use the Run Type button If you have been running you will first have to push the Abort button before you can change the run type Normally the configurations you want are the following TWOSPECT For running the two spectrometers in 1 TS mode PEDRUN To do a pedestal run in 1 T mode ELECTRON For E arm in 2 TS mode HADRON For H arm
292. uated by two Leybold 1000 s turbo pumps that are backed by a Leybold 65 cfm mechanical pump The turbo pumps are powered by 120 V AC power while the backing pump requires three phase 208 V AC power The motor on the backing pump is explosion proof and approved for use in NEC Class 1 Division 1 Group D hydrocarbons but not hydrogen environments An identical mechanical pump is used in the pump and purge system of the gas panels Both the scattering chamber backing pump and the pump and purge system s mechanical pump exhaust to the vent line Vacuum Gauges The chamber vacuum is monitored by an HP cold cathode gauge This gauge has a maximum operating voltage of 4000 V and a maximum current of 133 uA The pressure at the entrance to the roughing pump is measured by convectron gauge Flammable Gas Detectors There are four flammable gas detectors installed one on top of the target one each on top of the hydrogen and deuterium gas panels one on top of the gas tanks to provide early detection of hydrogen deuterium leaks These detectors are sensitive and calibrated over the range from 0 to 50 96 Lower Explosive Limit LEL of hydrogen The electro chemical sensors were manufactured by Crowcon Detection Instruments LTD and the readout four channels was purchased from CEA Instruments Inc The Gas Master Four System The readout unit provides two alarm levels per channel The low level CHAPTER 3 TARGETS 73 alarm is tripped at 20 LE
293. uld be regularly checked for leaks and damage In particular the system CGA 320 uses plastic seals at the bottle connection which must be replaced periodically Flowmeter Calibration The Tylan General mass flow controllers mass flow valves require periodic cleaning and calibration section 5 7 Tylan General Mass Flow Con troller Instruction Manual The first step in this process is to check the operation of the instruments and perform further work as necessary This procedure should be planned and carried out whenever 1 there appears to be a problem with the operation of a flow controller or 2 there is a lengthy break in the Hall A program that would allow the gas system to be taken off line for several weeks If absolutely necessary the needle valve rotameter combinations plumbed in parallel with the mass flow controllers could be used to allow interim operation of the gas system while one or more flow controllers is removed for maintenance Chapter 6 Slow Controls 6 0 1 Hall A Slow Controls 6 0 2 Introduction The Hall A base equipment for experiments consists of two general purpose similar superconducting spectrometers and their associated detector packages as well as several specific function systems i e cryogenic targets He target beam current monitors ARC energy measurement system e p energy measurement systems and so on Each of these major systems is typically composed of several sub system levels which
294. uld rotate around the target without vacuum coupling and without jeapordizing certain desired kinematic and acceptance specifications of both high resolution spectrometers needed for approved experiments It was also designed to simultaneously contain a liquid or gas target and an array of water cooled thin metallic foils both remotely controlled and also be adaptable for the waterfall target The desired kinematic specifications that were considered included momentum and energy resolution in both arms angular range of spectrometers angular acceptance and luminosity The chamber vacuum is isolated from the HRS by using thin aluminum foils The target chamber is designed so that each spectrometer will have continuous cov erage in the standard tune from 0 12 54 to 165 The target chamber is supported by a 24 in diameter pivot post secured in concrete rising about 93 6 in above the Hall A cement floor The Hall A target chamber consists of an aluminum middle ring a stainless steel base ring each with a 41 0 in inner diameter and a stainless steel cylindrical top hat with 40 n inner diameter to enclose the cryotarget and secure the cryogenic connections The aluminum ring with an outer diameter of 45 0 in and wall thickness 2 0 in is necessary for a sturdy support structure and to permit machining of the outside surface to accommodate the flanges for fixed and sliding seals mounted on opposite sides of the ring that vacuum connec
295. ull As the scat tering chamber is located in the middle of Hall A i e not in a confined area and the total Hall A volume is 40 000 m the ODH hazard is minimal 3 2 5 Controls The target controls have been implemented with the EPICS control system and with hardware very similar to that employed by the accelerator The basic control functions reside on a VME based single board computer The graphical interfaces to the control system use a PC and also require the Hall A Hewlett Packard HP computer for control HAC to be present as well All of the instrumentation for the target is downstairs in Hall A Most of the equip ment in fact all of the 120 V AC equipment is on an Uninterruptable Power Supply UPS The items whose power is not on UPS are e The scattering chamber vacuum pumps and the gas panel backing pump e The target lifting mechanism e The target circulation fans CHAPTER 3 TARGETS 80 This is a 7 kVA zero switching time UPS which is dedicated to the target The PC HAC and the counting house target X terminal are on Uninterruptable Power as well The targets dedicated UPS provides 18 minutes of power at full load or 50 min at one half load The status of the UPS online or offline is read by the control system and after ten minutes the control system will initiate an orderly shut down of the targets The principal functions that the control system performs are Pressure Monitoring The pressure at various places in
296. verview The Hall A spectrometers and associated instrumentation are designed to perform high resolution and high accuracy experiments The goal is to achieve a missing mass resolu tion of 200 500 keV to clearly identify the nuclear final state An absolute accuracy of 1 is also required by the physics program planned in the Hall which implies 10 4 accuracy in the determination of particle momenta and 0 1 mr in the knowledge of the scattering angle The instruments needed are a high resolution electron spectrometer HRES and a high resolution hadron spectrometer HRHS both with a maximum momentum capa bility matching the TJNAF beam energy and large angular and momentum acceptance A layout of the 4 GeV c High Resolution Electron Spectrometer is shown on Fig ures 4 2 and 4 1 Its main design characteristics are given in the attached table The spec trometer has a vertical bending plane and 45 bending angle The QQDQ design includes four independent superconducting magnets three current dominated cos20 quadrupoles and one iron dominated dipole with superconducting racetrack coils The second and third quadrupoles of each spectrometer have sufficiently similar field requirements that they are of identical design and construction The overall optical length from target to focal plane is 23 4 m Optically the HRHS is essentially identical to HRES In fact the two spectrometers can be used interchangeably to detect either positively
297. vide after a specific analysis the field profile of the dipole as seen by the other coil T his profile will cover one half of the magnet including one of the two fringing fields Reduce the PDI gain by one step example if the automatic gain is 10 CHAPTER 2 BEAMLINE 56 select manually 5 By inserting the jumper on the other coil one can get the other half profile These two single coil measurements will provide together the complete profile of the dipole including both fringing fields For the central part where the field is uniform more accurate data can be taken using the NMR probes Here there is no change in the hardware but one must use a specific software the mapping MEDM window By combining for a set of transverse positions standard integral measurement upstream profile upstream coil alone downstream profile downstream coil alone NMR map of the plateau one gets a 2D map of the dipole field in its mid plane with an optimum accuracy and redundancy and a minimum time spent by the operator This 2D map is used to get the straight to curved correction to the integral and a set of tolerances Call medmMew and NOT medm then open arc_map adl as this display is written in a new version of MEDM Due to a bug in this Solaris MEDM combination you must enter the name of the display in the open menu you can t just click on the display file name You then get the ARC MAPPING screen You must define th
298. w current power supply provides a nominal 1 80 kV Red HV RG 59 U cable good to 5 kV with standard SHV connectors is used to connect the power supply to the chambers Each HV channel of the 6 per chamber typically will draw a few hundred nA The Low Voltage System LV power supplies are used for the pre amp discriminator multiplexer cards Each card requires up to 1 6 A at 5 V and 0 6 A at 5 V plus a few mA threshold at 4 8 V High Pressure Gas Bottles The gas used in the chambers is supplied in high pressure 2 2000 psi gas bottles This confined high pressure gas represents a tremendous potentially lethal amount of stored energy 5 6 6 Responsible Personnel The following individuals are responsible for chamber problems Generally the non Jefferson Lab people are responsible for FPP detector problems whereas the Jefferson Lab people are responsible for more general data acquisition problems or e g gas voltage supplies shared with other systems Ronald Gilman Rutgers x7011 pager 0161 Mark Jones William amp Mary x5255 pager 849 5045 CHAPTER 5 HRS DETECTORS 191 Charles Perdrisat William amp Mary 221 3572 or 3522 Xiangdong Jiang Rutgers x7011 pager 849 6664 Steffen Strauch Rutgers x7011 Jack Segal Jefferson Lab x7242 Bogdan Wojtsekhowski Jefferson Lab x7191 CHAPTER 5 HRS DETECTORS 192 5 7 The Hall A Gas System 7 5 7 1 Overview The Hall A detector gas systems are located in the H
299. wer approaches the operating envelope limits for a specific beam dump 2 1 5 Personnel Safety System Personnel safety system PSS console equipment is located in the main control room It includes e Access control e Safety interlock e ODH monitoring Radiation monitoring Public address system Girder Diagnostic Optics Valves Element Distance m JE Elements Elements amp Pumps from target Beam Switch Yard TV Viewer ITV2C00 148 12862 1CB2 Dipole 2 3m MLA1C02 146 60000 0 13m shim 1CB3 BD MBD1CO00V 144 18700 Valve VBV1C00A 7 142 18686 Current SBC1C00 136 99564 Beam Stopper SSS1C00 136 53844 Beam Stopper SSS1C00A 136 08124 1 01 IPM1CO1 134 32465 BC 1 01 133 95000 Ion Pump VIP1CO1 133 04195 CHAPTER 2 BEAMLINE 22 1C02 BPM IPM1C02 132 02465 BC MQA1CO2 131 65000 MBC1C02V 131 30685 1C03 BPM IPM1CO03 129 02465 BC MQA1CO3 129 35000 Ion Pump VIP1C03 Rough Pump VRV1C03 128 44195 Convectron VTC1C03 1CB4 Dipole 1m MBN1C04 116 70000 1604 BPM IPM1C04 115 42465 Quad MQA1C04 115 05000 BC MBC1C04H 114 70685 Ion Pump VIP1C04 114 14195 1C05 BPM IPM1C05 112 12465 Quad MQA1CO5 111 75000 BC MBC1C05V 111 40685 Valve VBV1C05A Ion Pump VIP1C05 Rough Pump VRV1C05 110 84195 Convectron VTC1C05 1C06 Valve VBV1C06 BPM IPM1C06 104 82465 Quad MQA1CO6 104 45000 BC MBC1C06H 104 10685 Ion Pump VIP1C06 103 54195 1C07 BPM IPM1C07 99 52465 BC MBCICO7V 98 61076 Ion Pump VIP1C07 98 24195 Arc S
300. wer and 9 3 x 3 blocks in the case of Shower Central block is defined as the block that has maximum energy deposition The main cluster in Preshower Shower is the cluster with the biggest energy which is coincident with the golden track or coincident with some Shower Preshower cluster Coincidence of the cluster with the golden track means that the distance between the shower cluster center and crossing point of golden track with the detector plane is less than a certain magnitude Coincidence of the Preshower and Shower clusters means that distance between the clusters centers is less than a certain magnitude it is assumed that both of these points are on the same Z plane The shower clusters reconstruction in Preshower and Shower is performed by the following steps 1 Sort fired blocks in order of decreasing deposited energy 2 Pick out the block with maximum energy deposition and all fired blocks in its arrangement 2 x 3 blocks for Preshower 3 x 3 blocks for Shower as belonging to one cluster 3 Remove all blocks associated with the found cluster from further consideration 4 Repeat steps 2 and 3 until all of the fired blocks are associated with a cluster CHAPTER 5 HRS DETECTORS 164 5 Calculate energy deposition X and Y coordinates of each cluster and sort clusters by decreasing energy deposit 6 Define coordinates of crossing point of golden track with detector plane in detec to
301. xcess Flow Valve Remedy the cause and reset the valve eReplace empty supply bottle switches located on the Delivery Rack Gas Shed Airflow Gas Shed Exhaust Fan ceiling of Isobutane Room has failed Restore forced ventilation Vane Switch mounted just inside exhaust fan Overtemp Gas Shed Temperature in Gas Shed Too High 110 F eTake action to protect equipment eReduce temperature Klixon mounted in rack Over Pressure FPP Over Pressure VDC Electron Over Pressure VDC Hadron VDC FPP Exhaust manifold pressure at Hadron Or Electron Shield House Gas Rack eliminate exhuast line blockage e Allow Hall A atmospheric pressure to stabilize PHOTOHELIC gauges on gas panels in shld houses Gas Leak Flammable gas detection system has sensed a leak eLocalize leak by referring to readings on GasMaster 4 system in Counting House eFix Leak GASMASTER HydroCarbon Detector heads in Gas Shed and each Shield House Overtemp Electron Temperature in Electron Shield House Too High 110 F eTake action to protect equipment eReduce temperature Klixon mounted in gas rack in Electron Shield House Overtemp Hadron Temperature in Hadron Shield House Too High 110 F eTake action to protect equipment eReduce temperature Klixon mounted in gas rack in Hadron Shield House Post Bubbler Supply Overpressure
302. xtreme care The conductor pins are relatively fragile and should one be broken off repair will be extremely difficult e When initiating gas flow pay strict attention to the feedback parameters Over pressure may damage the chambers e Never attempt to apply HV to the chambers until gas flow conditions have reached steady state e As the amount of heat generated by the pre amp discriminator cards it substantial always make sure adequate cooling is provided before attempting to run Currently this cooling takes the form of four temporary fans which clamp to the aluminum Faraday cage Eventually permanent fans will be installed e When ramping the HV never allow the chambers to draw more than 1 yA instan taneously If they do something is wrong 5 2 4 Other Documentation See the URL Shttp www jlab org fissum vdcs html CHAPTER 5 HRS DETECTORS 143 5 2 5 Safety Assessment The following potential hazards have been clearly identified The High Voltage System The Bertan 377N HV low current power supply provides a nominal 4 00 kV Red HV RG 59 U cable good to 5 kV with standard SHV connectors is used to connect the power supply to a Hammond splitter box and then to connect the splitter box to each of the three high voltage planes in a given VDC A given chamber draws a current from 50 100 nA The Low Voltage System Kepco LV power supplies are used for the the LeCroy 2735DC pre amp discriminator cards Each card 23 per

OSP Hall A - Jefferson Lab

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