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Scattering Chamber User's Manual V2

1. 200 SMTR1610 4 122 04 Auto Hdw 0 381972 0 286479 0 286479 10 200 kr emrisigd 122 05 Auto Haw 75 50 15 10 20 Y SMIR1610 4 122 06 autoHdw 75 50 15 10 20 Z ISMTR1610 4122 07 Auto Hdw 75 50 15 10 20 Dettectorz_ SMTR1610 4 122 08 autoHdw 75 50 15 10 200 Slit Wheel SMTR1610 4122 09 autoHdw 300 300 90 10 20 Cryo SMTR1610 4 122 10 AutoHdw 36 3 0 06 10 25000 Analyzer Low 1 I CT AnalyzerThetyy 1 fom 1 1 1 7 gt 0 200 0 089524655 0 095492966 0 500 0 500 0 500 0 500 3 000 3 600 0 000125 0 001 0 000447623 0 001 Backlash Direction Yes Increase Page 19 REIXS Beamline RSXS Endstation User s Manual June 15 2012 4 0 Detectors There are four detectors and a slit filter wheel on the Two Theta arm 4 1 4 1 1 Figure 6 Detector assembly Photodiode The photodiode detector can be used for scattering reflectivity and x ray absorption measurements over a very large dynamic range extending from measuring the direct beam 2 A or 20n A to currents in the picoamp range 0 1 A or 0 1pA The photodiodes installed in the scattering chamber are AXUV100EUT from International Radiation detectors Inc It has a 10mm x 10mm square detection area The eutectic mount EUT was chosen for greater ultrahigh vacuum compatibility The diode can be baked to 200 C and operated to 70 C The photo
2. the scattering chamber is connected to a load lock chamber designed by David Hawthorn and manufactured by Nor Cal Products Inc via a manual 4 5 CF gate valve The load lock chamber is pumped by an 80 L s turbopump that is backed by a Varian IDP 3 Scroll pump Stabillon convectron gauge gauge convectron gauge Del G Pfieffer HiPace80 turbopump load lock chamber Q Stabillon convectron gauge gauge 4 5 manual EN gate valve MDC differentially differentially pumped pumped Scattering chamber rotary rotary feedthrough feedthrough stage 1 Thermionics AIP 2 ion pump 10 pneumatic gate valve VAT CTI CryoTorr 8F O cryopump C convectron gt Y Ke Ka Kc Varian TS 300 Triscroll to connect pump to turbocart Figure 14 Schematic diagram of the scattering chamber vacuum system 5 1 Pressure Measurement The chamber pressure is measured using Granville Phillips 370 Stabil Ion vacuum gauges for low pressure 107 10 Torr and 275 Convectron gauges for high pressure http n c com 1 http www brooks com June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 31 1000 10 Torr These gauges are controller by 370 Stabil Ion gauge controllers which each operates one Stabil Ion gauge and up to two Convectron gauges A cold cathode ion gauge is also installed on the scattering chamber which is used during the measurements when visible light o
3. 4 Polarization Analyzer The analysis of linear polarization is based on the principle of Brewster s angle Four multilayers were fabricated by Fraunhofer IOF for the four wavelengths energies of interest 1 OK edge E 530 eV d 1 658 0 002 nm reflectivity 3 0 2 Mn L edge E 645 eV d 1 362 0 002 nm reflectivity 1 8 3 Ni Ledge E 860 eV d 1 020 0 002 nm reflectivity 0 52 4 CuL edge E 940 eV d 0 933 0 002 nm reflectivity 0 15 The multilayer coating material is W Si with 200 400 periods each The ideal incident angle is 45 Two Attocuber rotary actuators are used to position the multilayers One actuator will orient the multilayers for analyzing either horizontal or vertical polarization The angular range required is about 90 The other actuator is used to switch between the four multilayers as well as to position the multilayer at correct Bragg angle 45 Two AXUV100EUT photodiodes one for each polarization are used to measure the reflected light from the multilayers The wiring of the photodiode is similar to the one described in Section 4 1 1 The current is measured by two Keithley 6514 Electrometers 4 5 Slit Filter Wheel In front of the channeltron and photodiode detectors is a slit wheel that can position one of ten slit filter combinations in front of either the channeltron or photodiode detectors The slits and filters are mounted on stainless steel rings that can be attached
4. Customized SPEC macros for REIXS RSXS endstation and a Quick Reference for frequently used SPEC commands 2 2 Choosing Detectors Filters and Slits The scattering chamber has many degrees of freedom Some advice is useful to choose the best detector and slit for your experiment 2 2 1 Detectors E June 15 2012 The photodiode is the first detector that should be used for any experiment It has a large dynamic range that is suitable for measuring the direct beam and for measuring weak signals Most experiments will begin with an alignment procedure that involves measuring with the direct beam The direct beam on the photodiode should have a magnitude of 25yA at 600eV with Beamline exit slit at 25 micron The dark current on the AXUV100 photodiode is lt 1pA The photodiode is light sensitive A larger dark current with the beam off may indicate light leaking into the chamber The Granville Phillips hot cathode ion gauge in the scattering chamber should be off during measurements with the photodiode The noise level on the photodiode should be of order 0 1pA Photodiode electrometer typical settings Autorange digital filter of 5 moving average of 5 measurements dwell 5 power line cycles 5 60Hz 0 083 s The channeltron detector has a maximum count rate of 1x10 counts sec at which point it becomes non linear The channeltron has worse quantum efficiency relative to the photodiode but has no dark current and provide
5. In the scattering chamber the channeltron is used in a configuration where photons will be directly incident on the channeltron s surface In front of the channeltron is situated an electro formed gold mesh with 85 transmission for repulsion of electrons and ions This grid is electrically isolated from ground by ceramic standoffs The channeltron can be positively or negatively biased by applying appropriate biasing to the grid channeltron front and channeltron back This is accomplished using a high voltage power supply and the appropriate voltage divider see Section 4 2 1 24 http www mcallister com hatwashers html 25 part KAP 1CX sd 60AF875SMAm accuglassproducts com from Huntington Mechanical Laboratories part PTR 24151 CF http www huntvac com 27 www sjuts com 8 SPI part 2199G AB www 2spi com Insulator seal part 9951200 www insulatorseal com June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 21 BI wall E D E E e ga E ee Figure 7 Feedthroughs for detectors The channeltron is housed in the scattering chamber within an aluminum enclosure Electrical connections to the channeltron are made using MHV panel jack receptacles These receptacles are connected to SHV vacuum feedthroughs using Accuglass kapton insulated co axial cables that have MHV connectors on one end and Accufast 500s connectors on the other end suitable for connection to the SHV vacuum feed
6. and DIR CHANGE will only apply a backlash correction if the direction of the move changes For our purposes the appropriate choice of backlash correction is FAVORED INCREASE e PARAMETERS STEPPER ONLY e BRAKE HOLD MODE Brake OFF e CLOSED LOOP OFF To set up the rest of the motor control software return to the SPEC Motors APS Motor Record Control Screens Click on the More button and setup from the drop down menu This will call up another screen motorx setup edl For the chosen motor enter the appropriate values see Table 3 for the e High limit e Low limit e Speed Normal e Speed Backlash e Base speed June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 17 e Acceleration time e Units deg or mm e Steps Rev e Deg rev or mm rev e Readback deg Unit or mm Unit 3 8 2 Spec Control Software To initiate SPEC user command runFOURC Customized SPEC macros for REIXS RSXS endstation and a Quick Reference for frequently used SPEC commands June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 18 Table 3 RSXS Endstation Motor Parameters Sage Base Spd Motor N St R otor ame Motorno Power EGU s Fa eels EGU Rev Encoder Readback Dead EGU Step Band Two Theta__ SMTR1610 4 122 01 orp 30 I 20 oo 20 60m om om 0 001 Theta SMTR1610 4 122 02 On 20 10 00 20 160 ch SMTR1610 4 122 03 Auto Hdw 0 895200 0 358080 0 268560 10
7. to 4200 V from HV power supply grounded to coax outer at power supply Grid Channeltron front 1800V Esch 100 MOhm 25 45 uA Channeltron back 10 Mohm L grounded to 70 115 V chassis Channeltron connector preamp Figure 8 Voltage divider for ve biasing of the channeltron Alternately a positive bias can be used to bias the channeltron In this configuration electrons and negative ions are attracted to the channeltron and positive ions are repelled For this configuration the high voltage divider shown in Figure 9 can be used Note for this divided a high voltage capacitor is used between the anode and the preamp to protect the preamp from the large DC bias voltage Also care should be taken to ensure that the high voltage power supply is delivering the correct polarity of voltage prior to applying voltages to the channeltron In both forward and reverse bias the channeltron bias voltages should be ramped up and down slowly over the course of several minutes to prolong the life of the channeltron HV 2500 to 4200 V from HV power supply grounded to coax outer at power supply Grid 1 25 45 uA 100 Mohm Channeltron front grounded to chassis 1800V 3000V 250 MOhm Channeltron back 10 Mohm 60 100 V 1 Mohm Channeltron Anode bh Preamp 330 pF 6 kV Figure 9 Voltage divider for ve biasing of the channeltron June 15 2012 REIXS Beamline RS
8. to the slit wheel in various combinations using two 0 80 screws 4 5 1 Slits The slits are precision cut slits from National Aperture Inc The slit options are 500 micron x 7 5 mm 100 micron x 7 5 mm 500 micron x 3 mm 100 micron x 3 mm or 100 micron x 1 mm not all sizes are likely to be installed at any given time The slits are formed in 3 8 diameter 12 7 micron thick 302 stainless steel disks These disks are carefully mounted on LS 0 5 stainless steel rings from Lebow Co such that the long part KAP 1CX 60AF500SMAm 4 http www nationalaperture com slits htm http www lebowcompany com June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 26 axis of the slit will be vertical short axis in the scattering plane when the slits are positioned in front of the channeltron or photodiode 4 5 2 Filters In addition to the slits the slit wheel can be used to position thin Aluminum or SizN4 filters in front of either the channeltron or photodiode detectors The aluminum filters are from Lebow company and are 0 15 micron thick foil and either 10 mm diameter on a LS1 0 ring or 5 mm diameter on a LSO 5 ring The transmission vs photon energy for 0 15 micron thick aluminum taken from the CXRO website is shown in Figure 11 al Density 2 6989 Thickness 0 15 microns Transmission 0 500 1000 1500 2000 Photon Energy eV Figure 11 Transmission vs photon energy for a 0 15 micron thick aluminum filt
9. 00 steps per revolution is 0 000125 Chi x This angular rotation is provided by the linear translation of a lead screw rather than a rotation The gear reduction is 1 2 and the pitch of the lead screw is 1mm such that one full rotation of the motor provides a translation of 0 5 mm 0 0025 mm per full motor step This linear motion q is translated into a rotation by having the chi stage travel on arc shaped rollers with a radius of R 320 mm In the limit d R sin xy 90 Rx 90 this linear motion gives 0 179049 per mm or 0 089525 per motor revolution At the extent of the chi motion 5 degrees this creates an error in Chi of sin x 90 y 90 y 90 0 006 Phi Like Chi this motion is provided by the linear translation of a lead screw rather than a rotation however on a radius of Rp 300 mm instead of 320 mm In the limit dg R sin Rap this linear motion gives 0 190986 per mm or 0 095493 per motor revolution X y z These motions are provided by linear translations of a lead screw with the gear reduction of 1 2 and the pitch of the lead screw of 1mm such that one full rotation of the motor provides a translation of 0 5 mm 0 0025 mm per full motor step In this co ordinate system zis the vertical axis Detector z detz This motion raises and lowers the detector positions allowing one to position the channeltron MCP photodiode or YAG crystal into the horizontal scatte
10. 58 to 4 8A range 3 7 4 Oriental Motor RBD245A V Motor Drivers The Two Theta tth and Theta th motors are driven by two Oriental Motor RBD245A V motor drivers 1 8 micro stepping is used to eliminate the motor stalling at low speed and also allow smooth start and stop of the motions The connection between the MaxV controller and the RBD245A V is the same as the E DC motor driver T TI Tm T 4 3rd harmonic waveform H 4 3rd harmonic waveform O O O a RBD245A V Motor driver settings e SW1 Third Harmonic Waveform Correction E 4 e SW2 1 Smooth Drive Used OFF e SW2 2 Vibration Suppression Used OFF e SW2 4 Motor Stanstill Current 25 of rated current ON e RUN Operating Current Dial Setting 2 0 84A phase e DATA Step Angle Dial Setting 4 Number of divisions 8 Micro Stepping 1 8 full step Resolution 1600 steps revolution Step Angle 0 225 e Each motor is supplied with 48 V DC power June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 14 3 7 5 OMS MaxV Motor Controller The motor controller used is the Oregon Micro Systems Inc MaxV motion controller The MaxV accepts commands from the control computer and outputs appropriate pulse sequences to the Parker E DC or RBD245A V motor driver Step Direction The MaxV is a VME bus based motion controller with each card controlling up to 8 motions The RSXS diffractometer with 10 motions requires 2 MaxV cards Being VME bus base
11. 5K B Starting with the cryopump cold 1 Open the gate valve between the scattering chamber and the Pfeiffer HiPace700 turbo pump The gate valve between the scattering chamber and the cryopump Should be closed Ensure all venting valves are closed and the TriScroll pump is connected to the pumping port of the turbo pump 2 Start the Varian TriScroll pump This should initiate the pumpdown of the chamber and the pressure reading of the Convectron gauges in the main chamber and at the exhaust of the turbopump should decrease 3 When the chamber pressure is below 10 Torr start the Pfeiffer turbo pump 4 Turn on the CCG or the hot cathode ion gauge in the main chamber when the pressure indicated on the Convectron gauge in the main chamber reaches 10 Torr 5 When the pressure reading on the scattering chamber is 10 Torr or lower the gate valve connecting the cryopump and the main chamber may be opened The pressure in the main chamber should rapidly drop by 1 order of magnitude owing to the increased pumping speed of the cryopump 5 7 Sample Transfer and Load Lock Samples can be transferred in and out the scattering chamber via a load lock and amagnetically coupled sample transporter The load lock has a garage that can accommodate 3 sample positions that can be moved out of the path of the sample transfer arm using a rack and pinion linear translator gt The sample transporter has a PG RMD HJS OM 1 pincer grip sample grabb
12. REIXS Beamline Resonant Soft X ray Scattering Endstation User s Manual Version 2 0 David Hawthorn and Feizhou He Updated June 15 2012 TABLE OF CONTENTS 1 0 Introduction and Specifications annann A 1 20 QUICK SIA AA AAA 2 2 1 WEIWERT Ti 2 2 2 Choosing Detectors Filters and Gite 2 2231 DEE Oen 2 222 Fitters ANG SIG rv 3 0 Ree ir eran een eens ere 4 3 1 Me 5 3 2 Bleid erziele Ee IR GEN S ei a A 7 3 3 Same FEN Gata c ke e e hil sa 7 3 4 EEE E 9 SA Temperature JONO 10 3 4 2 Baking the Cryostat aannnannnannnannoennnennnnnnnnnennnennnrnnnrnnnrrnerrnenee 10 3 5 FADNES 10 3 6 Diffractometer AMO MN E 10 3 7 Motor GONO ira 11 3 7 1 AML Stepper Motors rnrnnnnnnnnrnnnnrnnnrnnnnrnnnnnnnnvnnnnrnnnsnnennnnsnnn 11 3 7 2 Thermionics Differentially Pumped Rotary Feedthrough 12 3 7 3 Parker E DC Motor Drivers a a 13 3 7 4 Oriental Motor RBD245A V Motor Drivers oocccococcciconiconinooo 14 3 7 5 OMS MaxV Motor Controller oocococccocnccocnconcncocnccococoncnnns 15 e ME 15 3 7 7 ut e teen te UE 15 3 8 MOtOr CONT OL SOMWA arr 16 3 8 1 EPICS Motor Drivers Software Setup occcooccccocccconcnccnonnnoncnonnoos 17 3 8 2 Spec Control Software eian a a 18 A 20 4 1 ga le 8 0 ele 20 4 1 1 Photodiode Wiring n nnoannannnnnnennnnnoannnnnnnnnnnennrnnnrnnrnnnrsnrrnrennes 20 4 2 NAMCO DEE aa Ol 21 4 2 1 Channeltron Biasing ressaca 22 4 2 2 Channeltron Puls
13. To avoid leakage currents from the heater impacting the TEY the heater is electrically isolated from the sample holder by a sapphire plate The diodes and heater are wired using clear teflon insulated copper wire that is wrapped around the body of the cryostat and tied down with insulated copper wire to heat sink the wires In addition a wire for total electron yield measurements is connected to the sample holder which is electrically isolated from the cryostat using a thin sapphire plate and ceramic hat washers McAllister technical services The cryostat is equipped with two 10 pin UHV feedthroughs for the heater and the 3 diodes and one SMA feedthrough for the total electron yield measurement Thermionics ACS CR copper rope 1 8 in OD gt From Alessandro Mortara at the Swiss Federal Office of Metrology METAS www metas ch Copper lugs are clamped using the WDT tools 190942 Parallel Handcrimping Tool www wdttools ch english ps htm and the METAS custom die and guide set Gold plating was done by Ali Farvid at the SLAC Metal Finishing Shop Parts were electropolished and then electroplated with 2 um Ni and 5 um Au http www group slac stanford edu mfd mtlfnsh html 7 http www lakeshore com 8 7Sapphire C plane 1 diameter x 0 5mm thick wafer one side polished Part ALC25D05C1 MTI corp http www mtixtl com June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 9 Cooling of the cryostat is achieved using a cl
14. XS Endstation User s Manual Page 23 4 2 2 Channeltron Pulse Counting When a photon or charged particle impinges on the channeltron it produces secondary electrons that are accelerated by the high voltage applied to the channeltron These electrons will also strike the walls of the channeltron producing additional electrons that are further accelerated down the channeltron creating an avalanche effect This avalanche process produces a short pulse 8ns of up to 10 electrons at the anode These pulses are then counted to determine the number of incident particles hitting the channeltron To perform the counting the charge pulse is first amplified by a fast voltage preamplifier an Ortec VT120C gain 20 For ve biasing the charge pulse is converted to a voltage pulse by the isolating capacitor and the 50 Ohm input impedance of VT120C preamp For ve biasing the capacitor is missing and the 50 Ohm input impedance is the important The output of the VT120C is input into an Ortec 584 constant fraction discriminator This outputs a NIM standard fast negative gt the TIMING output for input to the SIS3820 counter card or NIM standard slow positive the POSITIVE output for input to the Ortec 449 2 ratemeter logic pulse for each input pulse that exceed a threshold voltage that can be set from 5 mV to 1V by a 10 turn potentiometer on the constant fraction discriminator This threshold should be set such that each input pulse is regis
15. a differentially pumped rotary feedthrough the first stage of which is pumped by the TriScroll pump with the second stage pumped by a 2 L s ion pump Pressure is measured by a combination of hot cathode ion gauge Stabil Ion cold cathode gauge and thermocouple gauges Convectron A residual gas analyzer is also installed on the scattering chamber A schematic of the pumping system is shown in Figure 14 48 http www struck de http www ultrahivac com June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 29 Table number 16 5 OD CF adapter flange for cryostat 10 OD CF blank 10 OD CF blank 6 OD CF viewport 6 OD CF viewport 6 OD CF viewport 6 OD CF viewport 4 5 OD CF beamline 10 OD CF viewport 10 8 OD CF viewport 11 8 OD CF viewport 12 4 5 OD CF viewport 13 4 5 OD CF load lock 14 8 OD CF viewport 15 10 OD CF viewport 16 see detail screwdriver viewport 17 see detail blank 18 8 OD CF viewport 19 8 OD CF viewport SECTION A A 20 8 OD CF viewport S viewport SCALE 0 075 1 1000 00 ale 39 2 75 CF RGA 44 275 ODCF goniometer 45 2750DCF goniometer Figure 13 The scattering chamber indicating port assignments for the vacuum pumps gauges and electrical feedthroughs June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 30 When the scattering chamber is operated as a stand alone system without the sample prep and analysis chambers connected
16. arm A counter clockwise rotation of the 20 axis corresponds to increasing 26 with the 20 rotation axis defining the positive z direction in the laboratory The zero of 20 is defined as the setting at which the undeflected X ray beam hits the detector The positive y axis is along the line from the sample to the X ray source The position at which rotates the y circle to put the y rotation axis along the y axis defines the zero of 6 A clockwise rotation of y corresponds to increasing y The zero of y is the position which puts the rotation axis along the positive z axis The positive x axis direction is determined by the cross product of the yand zaxes 2 y x 2 which completes the definition of the right handed coordinate system SPEC Four Circle reference v2 8 of spec documentation Certified Scientific Software 2001 June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 5 June 15 2012 Two Theta 20 This is the rotation of the detector arm about the vertical axis zin the laboratory frame This motion is designed with a gear reduction of 1 1800 such that one motor step 1600 steps per revolution is 0 000125 Theta 0 This is the rotation of the sample position about the vertical axis zin the laboratory frame It has been aligned out of vacuum to have the center of rotation co incident with that of the Two Theta rotation This motion is designed with a gear reduction of 1 1800 such that one motor step 16
17. at the 2nd stage to be pumped by the first stage This is needed to pump the 2nd stage to a low enough pressure lt 10 gt Torr to start the ion pump This should be done with a turbocart rather than the TriScroll pump that is usually used to pump the 1st stage of the differentially pumped rotary feedthrough 5 6 Pumpdown Procedure To pump the system down to low pressure from atmospheric pressure A Starting with the cryopump warm 1 Open the gate valve between the scattering chamber and the Pfeiffer HiPace700 turbo pump and the gate valve between the scattering chamber and the cryopump Ensure all venting valves are closed and the TriScroll pump is connected to the pumping port of the turbo pump gt http www thermionics com June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 33 2 Start the Varian TriScroll pump This should initiate the pumpdown of the chamber and the pressure reading of the Convectron gauges in the main chamber and at the exhaust of the turbopump should decrease 3 When the chamber pressure is below 10 Torr start the Pfeiffer turbo pump 4 Turn on the CCG or the hot cathode ion gauge in the main chamber when the pressure indicated on the Convectron gauge in the main chamber reaches 10 Torr 5 When the pressure reading on the scattering chamber reaches 10 Torr begin cooling the cryopump by turning on the CTI 8200 compressor The cryopump should take 1 5 hrs to reach a temperature of 1
18. d it requires a VME crate and VME crate controller to operate 3 7 6 VME The OMS MaxV motor controller operates on a VME bus The VME bus uses a Wiener VME crate and a Struck Innovative Systeme SIS1100 SIS3100 VME to PCI interface card combination This allows for control of the VME bus using a rack mounted PC with a Redhat Linux operating system 3 7 7 Attocuber Controller An Attocube ANC350 Controller from Attocube System AG is used to drive the two Attocube actuators inside the polarization analyzer The actuators have built in resistive encoders for close loop control of these two motions The Controller is connected to the REIXS VLAN network with following network configurations e Hostname MC2E1610 401 e Domain clsi ca e Static IP 10 52 11 100 e Subnet Mask 255 255 252 0 e Default Gateway 10 52 11 254 SPEC Setup Attocube e ANA Analyzer ANR101 RES e ATH Analyzer Theta ANR51v RES The default configuration for Attocube actuators e ANR101res_95_171 aps e ANRv51_C4 029 aps 18 http www pro dex com 19 http www wiener d com 20 htto www attocube com June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 15 f 3 8 Vi H del Vi gt Mi v a 3 Z O 5 A ANC350 Motion Controller O ACTIVATION x0 1 Figure 5 Attocube ANC350 Controller Figure 5 shows the front panel of the Attocube ANC350 controller The first channel is a motion controller The next three channels
19. diode clamped into place using BeCu clips and enclosed in an aluminum enclosure See IRD documentation for additional information quantum efficiency handling instructions for the AXUV100EUT photodiode Photodiode Wiring The photodiode is wired using triaxial cable and connectors to allow for a guarded and shielded measurement from the electrometer all the way to the photodiode The photo current is measured from the anode of the photodiode which is connected to the pin of an SMA receptacle attached using Epotek H21D silver epoxy and mechanical clamping The ground of the SMA connector is electrically isolated from the ground of the 22 http www ird inc com index html 3 Amphenol part 901 9215 purchased from Newark June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 20 4 2 aluminum enclosure by 2 ceramic hat washers from McAllister Technical Services and is electrically connected to the guard of a custom in vacuum Kapton insulated triaxial cable from Accuglass The cathode of the photodiode is electrically connected to the guard The shield of the Accuglass triaxial cable is connected to the aluminum enclosure of the photodiode Channeltron Detector The channeltron detector is used for single photon measurement It has an upper dynamic range of 10 counts second at which point the count rate will become non linear with the incident photon intensity The channeltron used is a Sjuts KBL10107
20. e Counting 00nno0nnnennnannnnnnnnnnnnnnnnnnnnennnenne 24 June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page i 4 3 Micro Channelplate MCP Detechor 24 4 3 1 MCP Mounting and Baseng 25 4 4 Polarization Analyzer aaa 26 25 SME VP 26 45 Bua 26 TD nn e OO aeeanns ate eae eee 27 4 6 Total Electron Yield TE W eee 28 AT VIG GIy Stal ME 28 4 8 Measurement Elechrontce 28 4 8 1 Nova Voltage to Frequency Converter 28 4 8 2 SIS3820 Counter Card c ooccccocccccccnccncnnononnonnnnonnnnnnnnnnnonnnnnncncnnnns 29 4 8 3 Fanin Fan Out NIM G rd eiea Gens anon 29 B20 ERT dE 29 5 1 Pressure Mesas UM A Ad 31 5 2 Pfeiffer HiPace700 Turbo Pumpen 32 5 3 Vanam ASCO PIN yu 32 5 4 Helix Cryo Torr 8F CGnwopump 32 5 5 Differentially Pumped Rotary Feecdtbrough 33 5 6 Pumpdown Hrocedure occcocccoccccccnccncncnonccncncnncononnnoncnnnnnnnnnncnnrnonnncnncnnnnos 33 5 7 Sample Transfer and Load Lock cooocccccccnccccnnocccnccnonncncncnannncnacnnnos 34 5 0 Items 0O Update Ve eegene 37 June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page ii 1 0 Introduction and Specifications The Resonant Soft X ray Scattering RSXS endstation is a UHV 4 circle diffractometer for resonant elastic x ray scattering It is intended for use in resonant soft x ray scattering absorption and reflectivity measurements in the soft x ray region 100 2000 eV to probe the C N O F Na Mg Al K edges the 3d transition meta
21. e current settings used for the AML stepper motors are shown in Table 2 These settings do not generally need to be adjusted The motor driver is controlled by the OMS MaxV motor controller which communicates with the E DC motor driver via the 25 pin D connector this is achieved through an intermediary breakout box which converts the signal carried by the CAT5 cable from the OMS MaxV card to the cable connecting to the E DC motor driver Additional E DC motor driver notes e The motor current is set individually for each motor with a suitable choice of a resistor between REF and CURRENT inputs on the motor e Each motor is supplied with 48 V DC power e A wire is connected between CURRENT and REMOTE This enables the motor controller to bring the motor current to zero when not moving This is used in conjunction with the AUTO HARDWARE option of the MaxV motor controller software 17 http www parkermotion com June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 13 Table 2 Parker E DC motor driver DIP switch settings 2 3 4 5 6 7 8 1 4 5 7 AML Motors Rotary Feedthrough Anti resonance enabled ON Anti resonance enabled ON ON l 200 steps per revolution ON 25000 steps per revolution ON O O E Ca En O al full standby current full standby current Automatic test disabled Automatic test disabled OFF OFF current loop gain 16 F current loop gain 16 N F OFF 0 44 to 1 27A range OFF 1
22. ed is supplied by the Helix Cryo Torr 8F cryopump gt This pump uses a closed cycle helium cryo cooler to cool a cold head a large surface area gas absorbing manifold to 15K At these low temperatures the sticking co efficient of most gases is high As such gases hitting the cold head are stuck on the cold head and effectively removed from the vacuum system For water the Helix 8F has a reported pumping speed of 4000 L s The cryopump is connected to a helium compressor the water cooled 3 phase 8200 compressor using flexible self sealing high pressure helium conduits The temperature of the cryopump is measured with a CTI curve C diode installed on the cryostats coldhead This can be monitored using the Lakeshore model 211 temperature monitor If the pump temperature and chamber gt from Stanford Research Systems Inc http www thinksrs com products RGA htm 7 http www helixtechnology com http www lakeshore com June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 32 pressure begin to increase and the pump is still operational it may be an indication that the pump is saturated and needs to be regenerated heated up and pumped out The pump is isolated from the main chamber using a 10 OD CF pneumatically controlled gate valve from VAT part 10846 UE24 0005 0094 Care must be taken to ensure that the cryopump is not exposed to high pressure air when cold as all of the water in the air will condense onto t
23. er calculated from the CXRO website http henke Ibl gov optical constants filter2 html Note the effect of Aluminum oxidation has been neglected in this calculation This will provide some energy dependence to the filter at the oxygen K edge 520 600 eV The silicon nitride SizN4 windows are from Norcada part NX10500A They have a 5mm x 5mm window that is 50nm thick mounded on a 10mm x 10mm 200 micron thick silicon frame This frame is then mounted on a Lebow LS0 5 or LS1 0 ring The transmission vs photon energy for 50 nm thick SizNa taken from the CXRO website is shown in Figure 12 http henke Ibl gov optical constants filter2 html 4 http www norcada com http henke Ibl gov optical constants filter2 html June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 27 4 6 4 7 4 8 4 8 1 Total Electron Yield TEY The total electron yield TEY which is proportional to the x ray absorption is determined by measuring the drain current coming off the sample when subjected to the x ray beam This is simply done by measuring the current from a lead connected to the sample holder which has been electrically isolated from the chamber ground The drain current is measured using a Keithley picoammeter or other suitable current measuring device SiIGN4 Density 3 44 Thickness 5 00000E 02 microns Transmission Photon Energy eV Figure 12 Transmission vs photon energy for a 50 nm thic
24. er see Figure 15 This pincer grip is opened and closed by rotating one of the magnets on the dual shaft sample transporter The pincer grip is used to clamp around the stainless steel eyehole protrusion on the sample holder see Figure 2 When the pincer grip is closed around the eyehole protrusion the sample can be removed from the garage by lowering the garage and pulling the sample back from the garage with the sample transporter Ferrovac RMDG40 900 150 Dual Shaft Rotateable Sample Transporter http www ferrovac ch gt Huntington Mechanical Laboratories model L 2231 4 June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 34 The sample can then be positioned in the diffractometer sample receptacle with using the sample transporter Once the sample is in the sample receptacle the pincer grip can be opened the sample transporter removed and the sample locked in place using the 4 40 screw and the in vacuum screwdriver Please refers to the RSXS Loading Samples procedure for details of sample loading June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 35 Isometrische Ansicht Material vennmass Uber 1 6 30 100 300 10001 bis 6 30 100 300 1000 2000 Pincer Grip RMD for Omicron Toleranz 0 05 0 1 0 3 0 5 0 8 1 2 Sample Plates PG RMD OM 44 PG RMD OM Ferrovac GmbH Winterthurerstr 457 8051 Z rich Figure 15 Ferrovac PG RMD HJS OM 1 pincer grip manipu
25. erentially pumped rotary feedthrough to allow for rotation of the cryostat and heat shield in concert with the theta rotation of the sample The scattered x rays can be detected with one of four detectors a photodiode detector that is suitable for high intensity signals including the direct beam a single photon sensitive channeltron detector a 2D single photon sensitive micro channelplate MCP detector and a polarization analyzer for horizontal or vertical polarization at O K Mn Ni and Cu L edge A slit filter wheel is positioned in front of the channeltron and photodiode detectors to allow one to position different size detector slits and either Al foil or silicon nitride filters in front of the detectors In addition the sample has been electrically isolated from ground to allow for total electron yield TEY to also be measured simultaneously The in vacuum diffractometer is housed in a 1m diameter vacuum chamber that is pumped by a 700 L s turbo pump and a cryopump This pumping combination provides a base pressure of 5x10 Torr June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 1 2 0 Quick Start 2 1 Manuals and Procedures Please refers to REIXS Manuals webpage for the most updated manuals http exshare lightsource ca REIXS Pages manuals aspx Useful procedures 1 2 3 4 5 RSXS Loading Samples RSXS Center of Rotation Alignment RSXS Sample Alignment RSXS Alignment for Reflectivity Scans
26. have three identical stepper drivers e Stepper Driver 1 ANR101 RES e Stepper Driver 2 ANRv51 RES e Stepper Driver 3 Spare Motor Control Software The motor control software is running on REIXS IOC with a Scientific Linux operating system The motor control software is comprised of several components 1 Motor control software written by the CLS as a generic motor control for stepper and servo motors This motor control software communicates with the motor control hardware a separate module is designed for each specific motor driver ex the OMS MaxV motor control card This software also assigns an EPICS process variable PV for each control feature and broadcasts the PV to the CLS distributed EPICS control system 2 A secondary module is needed to convert the PV names used by the CLS EPICS motor control convention to the APS EPICS motor control convention This is needed since SPEC is only set up to use the APS EPICS motor control convention 3 SPEC This is standard diffractometer control software from Certified Scientific Software SPEC controls the diffractometer by calling the EPICS motor process variables needed to control the motors To access the SPEC Motors APS Motor Record Control Screens click the APS Motors button on the REIXS Motor Energy Main Menu 21 http www certif com index htmi June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 16 3 8 1 EPICS Motor Drivers Software Se
27. he pump potentially damaging the cold head and requiring considerable pumping time to remove It is designed to be operated below a cross over of 150 Torr liters For the scattering chamber volume of 1000 L this corresponds to a cross over pressure 0 15 Torr If time permits it is best to operate the cryopump at lower pressure after pumping the chamber using the turbo pump to a pressure of 10 Torr or lower In addition care must be taken to ensure that the pump is not isolated when warming as all of the gas condensed on the pump will outgas upon warming As a safety measure the pump is equipped with a one shot UHV burst disk MDC part 420032 that will release in the event pump overpressure P 10 psi If the pump is to be warmed with the gate valve to the main chamber closed the pump can be vented and pumped through an auxiliary roughing port during warming Warm dry gas nitrogen can be flowed through the pump during warming to speed up the regeneration process 5 5 Differentially Pumped Rotary Feedthrough The cryostat on the scattering chamber is supported by a 6 OD CF differentially pumped rotary feedthrough Thermionics RNN 400 MS MFD MC gt The first stage of the differentially pumped rotary feedthrough is pumped by a Varian TriScroll TS 300 pump The 2nd high vacuum stage is pumped by a Thermionics 2 L s appendage ion pump part AIP 2 133 MP 2 A manifold supplied with the pump allows for a valve to be opened so th
28. hined at the AMPEL machine shop by Dieter Schnieder 3 6 Diffractometer Alignment The diffractometer is mounted on a ring that is attached to a separate frame from the scattering chamber by three stainless steel rods At the base these rods are attached to three CF flanges that connect to the scattering chamber through edge welded flexible bellows This sub frame designed by Luc Venema has out of vacuum adjustments for the pitch roll vertical height and horizontal position of the goniometer relative to the http www ata nl 10 http www rpmechatronics co uk 11 http www championballbearings com 12 http www jicastings com home htm 13 38 50 FF edge welded stainless steel bellows from Palatine Precision Ltd http www palatineprecision co uk June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 10 beam direction to be adjusted independent of the scattering chamber This allows for orientation of the goniometer to have a horizontal scattering plane with the beam intersecting the axis of rotation of the goniometer The flexible bellows also provide some degree of vibration isolation from the scattering chamber cryostat pumps 3 7 Motor Control 3 1 AML Stepper Motors The stepper motors used in the diffractometer are Arun Microelectronics Ltd AML C14 1 vacuum compatible stepper motors These motors are speciallty stepper motors chosen for their low outgassing and suitability for ultrahigh vacuum Con
29. hrough 4 port 33 detector z and slit wheel 14 http www arunmicro com gt http www omeaa com June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 11 OMEGA de ee temperature monitor Parker E DC motor drivers 1 per motor limit switches and encoders Motor controller breakout boxes i not used OMS MaxV motor controllers 2 VME crate VME crate rack mounted control computer Linux CLS EPICS distributed control system Experiment control computer EPICS motor control and SPEC Figure 3 Block diagram of the motor control sequence 3 7 2 Thermionics Differentially Pumped Rotary Feedthrough The Thermionics RNN 400 Rotary Feedthrough is driven by a Lin Engineering motor 8618M 02DE It is a NEMA 34 frame mount with 8 wire bipolar wiring series connection nominal rating 3 0V 4 0A This motor is also driven by a E DC motor driver 16 http www linengineering com LinE June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 12 J gt Le s l s v Ler Ge we AA Figure 4 Feedthroughs for AML motors and polarization analyzer 3 7 3 Parker E DC Motor Drivers The motors except for tth and th are powered by Parker E DC motor drivers The E DC motor drivers have a number of hardware selected options to determine the steps revolution motor current standby current step waveform etc Many of these parameters are set by DIP switches on E DC board Th
30. jack receptacles These receptacles are connected to SHV vacuum feedthroughs using Accuglass Kapton insulated co axial cables that have MHV connectors on one end and Accufast 500s connectors on the other end suitable for connection to the SHV vacuum feedthroughs Each cable is labeled at either end with 1 2 3 or 4 loops of Kapton insulator copper wire to aid in identifying the wires The outer connector of these co axial cables is connected to the chamber ground at both the MHV receptacle and the SHV feedthrough In addition low voltage signal leads connected to the four corners of the resistive anode are needed to carry the detector signal to the detector electronics The signal leads use SMA panel jack receptacles like the photodiode detector These receptacles are connected to BNC vacuum feedthroughs MG 23 electroformed gold mesh from Precision Eforming http www precisioneforming com 37 Delta Part UG 931 U www deltarf com purchased from M amp S Electronics Inc 38 part KAP 1CX 60AF500sMHV 32 Amphenol part 901 9215 purchased from Newark June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 25 using Accuglass kapton insulated co axial cables that have SMA connectors on one end and Accufast 500s connectors on the other end suitable for connection to the BNC vacuum feedthroughs These detector signals are then fed into the model 2500 preamp which then outputs to the model 2502A position analyzer 4
31. k silicon nitride filter calculated from the CXRO website http henke I Ibl gov optical constants filter2 html YAG Crystal For a visible indication of the beam position scintillating Yttrium Aluminum Garnet activated by Cerium YAG Ce crystals are installed on the detector arm in the center of the slit wheel and as an optional sample when placed on the sample holder The YAG Ce crystals are 10 mm x 10 mm x 1 mm with a square grid marked on the surface of the crystal The 8 mm x 8 mm grid has 1 mm x 1mm squares 30 micron thick lines and a cross hair through the center of the grid formed by thicker 60 micron lines Measurement Electronics Nova Voltage to Frequency Converter The Nova N101VTF voltage to frequency converter provides the option of converting from Crytur Ltd http www crytur cz 47 http novarad com n101vtf htmi June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 28 the analogue output of a picoammeter electrometer or current preamplifier into counts per second The resulting signal can be read into the SIS3820 counter card along with the output from pulse counting measurements such as the channeltron This allows one to measure several instruments with co incident start and stop times The Nova N101VTF uses LEMO style co ax connectors for all inputs and outputs 4 8 2 SIS3820 Counter Card Pulsed detector signals such as from the channeltron discriminator or the Nova voltage to freque
32. l L edges and the rare earth M edges amongst other absorption edges in this energy range The diffractometer has 11 in vacuum motorized motions including 4 rotations 20 0 X the ability to position the sample in the center of rotation x y z the ability to position one of four detectors into the scattering plane detz the rotation of a slit wheel s t that allows one to position one of 10 slit and filter combinations in front of the detectors and two piezo actuators ana ath to position the multilayers in the polarization analyzer The sample can be transferred into and out of the vacuum chamber using a load lock and a combination of an in vacuum wobble stick screwdriver and a magnetically coupled dual axis sample transporter The load lock garage can house up to 3 samples for rapid switching between samples and minimal downtime The sample holders have been developed to allow for a full azimuthal rotation of the sample that can be manually actuated by the in vacuum wobble stick manipulator The sample can be cooled to 20K using a closed cycle Helium 4 cryostat that is connected to the top of the scattering chamber The sample holder which is rigidly connected but thermally isolated from the diffractometer is thermally attached to the cold stage of the cryostat using flexible copper ropes A heat shield extends from the cryostat in order to reduce radiative heat losses at the sample position The cryostat is also mounted on a diff
33. lator for sample transfer June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 36 6 0 Items to Update v2 0 e motor feedthrough wiring diagrams e revise scattering chamber layout to correct and specify motor feedthrough locations e description of sample transfer procedure direction of clamping action cautions about applying too much torque to the sample holder theta angles for transfer and clamping tilting of phi by 1 degree to push sample holder up against the screw e procedure to align diffractometer phosphor cross hairs and telescope e Modify pumping diagram e diagram of channeltron wiring e include images of typical channeltron pulses e clarify which panel the BACKLASH setting must be set in e telescope Topcon AT G6 e note about venting of turbopumps with part numbers e add note about lubricating the gear wheels with WS MK Impex MK WS 06 0 6 micron WS powder e modify section on slit wheel motor e add SPEC commands June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 37
34. ncy converter are to be counted using a Struck Innovation Systeme SIS SIS3820 64M scaler card This card is housed in a VME crate which is controlled by a rack mounted computer running Linux operating system This computer is connected to the network and allows for controlling the SIS scalar card from the EPICS distributed control system using EPICS drivers and control software written by the CLS controls group for the SIS3820 The SIS3820 scalar card has 32 channels that have been factory configured to have channels 1 16 operate with a NIM standard logic pulses and channels 17 32 to operate with TTL standard logic pulses The SIS3820 uses LEMO style co ax connectors for all inputs and outputs 4 8 3 Fan in Fan Out NIM Card A CAEN N454 4 8 Logic Fan In Fan Out NIM card is used to split one detector signal to two identical signals This is mainly for the data collection during the 2 in 1 mode operation 5 0 Vacuum System The scattering chamber is a custom stainless steel vacuum chamber designed by Luc Venema and manufactured by Johnson Ultravac Inc see Figure 13 The chamber is pumped by a Pfeiffer 700 L s turbo pump and a CTI Cryo Torr 8F cryopump The turbo pump is backed by a TriScroll pump that is used both to back the turbo pump and to pump the chamber down from atmospheric pressure Both the turbo pump and cryopump are separated from the scattering chamber by electro pnuematic gate valves In addition the scattering chamber has
35. ned by David Hawthorn and constructed out of thin wall stainless steel hypodermic tubing 0 095 diameter 0 005 thick This structure has two levels with 6 tubes per level held together by aluminum brackets The sample receptacle is electrically isolated from the support structure by 4 ceramic hat washers McAllister Technical Services The sample holder is also attached to the cryostat above using flexible copper braids see Section 3 4 for details of the braids and cryostat This design is intended to provide high strength and stability with minimal conductive heat loss through the support structure The heat load on the sample supplied by the support structure assuming the base is at room temperature and the sample is at 4K is estimated to be 0 1W gt http lowerfriction com June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 7 a b Figure 2 a Sample holder and sample receptacle assembly b and c Blowup of sample holder and sample receptacle assembly June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 8 From above the sample holder is connected to the cryostat using 4 lengths of OFHC copper rope with gold plated copper lugs clamped to each end of the rope These copper braids are then clamped with stainless steel screws to the sample receptacle on one end and to a gold plated OFHC copper adapter that connects to the cryostat on the other end This latter adapter is separated fr
36. num x Filter removed 4 For weak broad peaks larger slits will give better signal to noise ratio 5 The aluminum filters provide additional light blocking for the photodiode detector 6 Both the channeltron and photodiode are sensitive to charged particles electrons ions The aluminum and Si3N filters provide some filtering of charge particles The measurement contribution from charge particles has not yet been tested for the various detectors June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 3 3 0 Diffractometer The diffractometer is a 4 circle UHV diffractometer with a total of 10 degrees of motion It was designed principally by Luc Venema at the University of Groningen based in part on the Spinoza diffractometer at the NSLS beamline X1B The diffractometer has a full range of theta and two theta motions spanning O 180 degrees and limited chi and phi motions each spanning 5 degrees In addition the sample position can be moved 7 5mm in x y and z to position a sample into the center of rotation of the diffractometer In addition to these 7 motions the detector arm allows for a z height adjustment of 90 mm to position any of the four detectors photodiode channeltron MCP or Polarization Analyzer into the horizontal scattering plane A slit wheel with unlimited 360 degree rotation allows for one of ten filters slits to be positioned in front of either the channeltron or photodiode detecto
37. om the cryostat by a thin sapphire plate described above to provide electrical isolation but maintain good thermal contact The sample receptacle copper braid clamps and some of the sample holders were electropolished and gold plated in order to reduce their thermal emissivity 3 4 Cryostat The sample is cooled with an Advanced Research Systems ARS DE 210SB closed cycle cryostat The cryostat is a UHV compatible 2 stage cryostat The 2nd stage of the cryostat is designed to reach a base temperature lt 3K without any attachments and have 0 8W of cooling power at 4 2K A custom gold plated OFHC copper heat shield is attached to the first stage of the cryostat and extends to partially cover the sample holder This provides partial shielding against radiative heat losses The cryostat is mounted in the chamber on a Thermionics RNN 400 differentially pumped rotary feedthrough This has a motorized rotary motion to allow for it to rotate along with theta This is necessary to allow for a wide range of motion without twisting up the copper braids that connect the cryostat and the sample holder It also allows for rotation of the heat shield relative to the sample holder The temperature of the cryostat is monitored and controlled using three Lakeshore DT 670B SD silicon diode temperature sensors The heater is a Lakeshore 252 100W cartridge heater HTR 25 100 It is clamped in place using an OFHC Cu clamp just above the sample holder
38. on User s Manual Page 24 4 3 1 MCP Mounting and Biasing The detector head has an 85 transmission electroformed gold mesh attached to front end gt It is mounted in an aluminum enclosure and attached to the enclosure by the grid ring at the front of the detector This grounds the grid in front of the channelplate to the aluminum enclosure and subsequently the scattering chamber Similar to the channeltron the channelplate requires high voltage biasing in order to operate This can be done using a single high voltage power supply and the voltage divider shown in Figure 10 r SHV connector EM Input grounded to chassis 800 950 V 1 MOhm SHV connector 300 500 uA min EM Center SHV connector EM Output 0 005 uF 150 300 V T 0 01 uF 200 KOhm SHV ve 1800 to 2200 V from HV power supply grounded to coax outer SHV connector connector ee i at power supply EES series resistors to limit current o in event of discharges High Voltage divider in sensor for Quantar MCP detector 100K to 1Mohm For Dave Hawthorn dhawthor uwaterloo ca Figure 10 Voltage divider for ve biasing of the MCP For the MCP these high voltage connections are needed for the 1st channelplate between the two channelplates at the 2nd channelplate and at the resistive anode Like the channeltron high voltage electrical connections to the channelplate are made using MHV panel
39. osed cycle circuit that includes a 3 phase water cooled helium compressor ARS model 10 HW and 3 4 stainless steel self sealing high pressure helium lines that connect the cryostat expander to the compressor Power to the expander is also supplied from the compressor 3 4 1 Temperature Control Temperature control is achieved using the Lakeshore 325 temperature controller The diode connected to the top of the sample bracket is used as the control sensor The diode connected to the cold point of the cryostat is for monitoring purpose only The Lakeshore 325 controller is set to use 10 region PID control 3 4 2 Baking the Cryostat The displacer of the cryostat needs to be removed in order to bake the cryostat 3 5 Fabrication The components of the diffractometer were machined mostly out of Aluminum 6061 by machinists at the University of Cologne in Germany the University of British Columbia and the University of Groningen Gearwheels were supplied by Gear Technology and Applications GTA and Reliance Precision Mechatronics LLP Hybrid bearings with MoS coating were supplied by Champion bearing TiN coating of gearwheels and V groove rollers was done by J J Castings Investments Heat Treatments Ltd For more detail on individual components and their assembly refer to the complete set of drawings of the diffractometer and supporting documentation supplied by Luc Venema The sample holder and support structure were mac
40. r All of these motions are achieved using AML C14 1 in vacuum stepper motors and suitable gear reduction In the polarization analyzer two Attocube piezo actuators are used to position the 4 multilayers for either horizontal or vertical polarization The final motion is a rotation of the cryostat which is mounted on the vacuum chamber via a differentially pumped rotary feedthrough This is motorized externally but allows for the cryostat to be rotate in concert with or separately from the theta rotation as needed As a note of caution this notation may conflict with other co ordinate system conventions In particular the convention used by Luc Venema in designing the instrument interchanges the definition of y and z relative to the above convention t L Venema rug nl June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 4 Te re A MCP EP Mm ha Sample holder EN l Slit wheel f D MIS I A ja al Sample support structure Photodiode z stage Figure 1 Image of the diffractometer prior to installation in ite scattering chamber 3 1 Motions All of the motions of the system are detailed below For this description the coordinate system detailed in SPEC for a four circle diffractometer is used From the SPEC manual The x y plane of the laboratory coordinate system is called the scattering plane and contains the sample and the points reached by the detector as it rotates on the 20
41. r ion affects the signal background In addition a SRS RGA200 residual gas analyzer with electron multiplier is installed for detailed analysis of the residual gas composition The RGA200 is interfaced using an RS232C serial cable to a PC that runs the Windows based RGA control software Warning The ion gauges and RGA should only be turned on at low pressure P lt 10 4 Torr 5 2 Pfeiffer HiPace700 Turbo Pump The HiPace 700 is a 700 L s turbo pump mounted on an 8 OD CF flange It provides the pumping to achieve the high vacuum 10 Torr needed to open the cryopump to the vacuum chamber It also provides an alternative pumping mechanism for instances when the vibration from the cryopump in unacceptable The turbo pump is backed by a Varian TriScroll pump This pump is isolated from the main chamber using an 8 OD CF pneumatic gate valve with solenoid and position indicator part 303006 101 The pump may be vented to atmosphere from the venting port of the pump This should be done using dry nitrogen gas This venting port also serves as the main port for venting the scattering chamber 5 3 Varian TriScroll Pump The Varian TriScroll TS300 pump is used to rough out the chamber to 1 Torr during initial pumpdown It also serves as the backing pump for the Pfeiffer HiPace700 turbo pump providing a pressure of 107 Torr at the turbo pump exhaust 5 4 Helix Cryo Torr 8F Cryopump At high vacuum the highest pumping spe
42. ring plane This motion is provided by linear translations of a lead screw with the gear reduction of 1 2 and the pitch of the lead screw of 1mm such that one full rotation of the motor provides a translation of 0 5 mm 0 0025 mm per full motor step The center of the channeltron detector is positioned 40 mm above the center of the MCP and YAG crystal which are positioned 40 mm above the center of the photodiode detector The polarization analyzer is 10mm above the center of YAG crystal Slit wheel s t The slit wheel is coupled to a drive with 1 120 gear reduction One motor step 200 steps per revolution is 0 015 degree The 10 slit filter positions on the slit wheel are equally spaced 36 apart Analyzer ana This Attocube piezo rotary actuator is inside the polarization analyzer to change the orientation of the multilayers for measuring either horizontal or vertical polarization REIXS Beamline RSXS Endstation User s Manual Page 6 3 2 3 3 e Analyzer Theta ath This Attocuber actuator is used to switch between the four multilayers for different photon energies and to position the multilayers at correct theta angle for polarization analysis Lubrication of Gears For all the gear wheels in UHV regular grease lubricant cannot be used For proper lubrication of the gear wheels especially the worm gear dry Tungsten Disulfide powder WS from MK Impex Canada MK WS2 06 0 6 micron WS2 powder is applied every two to fo
43. s more accurate measurements for weak signals Channeltron detector typical settings discriminator threshold 60mV 6 on the dial less than one full turn of the 0 1V 10 turn potentiometer voltage 2100V dark REIXS Beamline RSXS Endstation User s Manual Page 2 count with beam off 0 1 cts s When starting up counts should start to appear at 1800V On the oscilloscope the pulses should have a width 5 10ns 8 The micro channelplate MCP detector has a maximum count rate of 1x10 counts sec for the total area It has very low dark count and is very good for measuring weak signals The voltage for MCP detector is 1900V 9 Total electron yield TEY Using SR570 preamplifier 30 Hz 12dB low pass filter OV bias O current offset low noise 5nV A sensitivity The TEY should be slightly noisier with the cryostat on due to inductive pickup from the cryostat 2 2 2 Filters and Slits 1 Use slitselect command in SPEC to select the slit 2 The distance between the sample and the slits is 290 mm 3 To search for Bragg peaks or specular reflections it is best to start with the largest slit and move to smaller slits once peaks are found Table 1 Slits 1 o 10mmx10mm 196 x1 96 nofiter 5 mm x 5 mm 0 988 x 0 9889 0 1 mm x 3 mm 0 020 x 0 5939 6 180 0 1 mm x 1 mm 0 020 x 0 198 no filter 8 108 0 5 mm x 3 mm 0 099 x 0 593 Aluminum Co 72 10mmdiameter 196 Alumi
44. sult the AML C14 1 manual for detailed specifications The vacuum performance of the AML stepper motors depends on their temperature during operation which determines how much the motors outgas The motors should be operated in a mode where full power is only applied during motion minimum or no holding current This can be accomplished with appropriate settings on the Parker E DC or Oriental Motor RBD245A V motor drivers set in hardware and the OMS MaxV motor controller set in software The temperature on each motor can be monitored using K type thermocouples embedded in the motor and Omega CN708 thermocouple temperature monitors and limit controllers The motors can be baked to 200 C This can be achieved by applying a suitable steady current to the motors from the E DC or RBD245A V motor drivers Each AML C14 1 stepper motor has 4 Kapton insulated motor wires and two thermocouple wires AML MLF18F feedthroughs are used to feed the wires between UHV and air Each MLF18F has 18 pins and bundles the wires from three motors onto each feedthrough On the air side MLF18L cables carry the motor wires to the motor driver enclosures From here the motor wires are connected to the E DC or RBD245A V motor drivers and the Omega CN708 temperature monitors The layout of the feedthroughs for motors is shown in Figure 4 e Feedthrough 1 port 36 Theta and two theta e Feedthrough 2 port 35 chi and phi e Feedthrough 3 port 34 x y and z e Feedt
45. tered as a pulse but no noise pulses or artifacts due to unusually shaped pulses which can lead to double counting of pulses register as pulses Examining the pulses using an oscilloscope can aid in setting the correct discriminator level The absolute value of the discriminator level will depend on the details such as the applied bias voltage the state of the channeltron and the configuration of the biasing network The count rate of the channeltron can also be monitored using the Ortec 449 2 ratemeter 4 3 Micro Channelplate MCP Detector The micro channelplate MCP detector is a single photon sensitive spatially resolved 2D detector from Quantar Technology Inc The channelplate detector head is a 25 mm diameter double channelplate detector part 3390 3090 SH SM R1 This detector head has a lower resistance faster time constant resistive anode SH is equipped with higher count rate HOT SM channelplates It s spatial resolution of 0 25mm and a maximum count rate of 10 cts s It is designed to be used in conjunction with the model 2502A position analyzer the model 2415C histogramming memory and model 2500 preamp 32 http www ortec online com 3 The 584 constant fraction discriminator should be used in Leading edge LE mode 34 see http www ortec online com download Electronics Standards Definitions pdf for definitions of NIM logic standards 35 http www quantar com June 15 2012 REIXS Beamline RSXS Endstati
46. throughs Each cable is labeled at either end with 1 2 3 or 4 loops of Kapton insulator copper wire to aid in identifying the wires The outer connector of these co axial cables is connected to the chamber ground at both the MHV receptacle and the SHV feedthrough 4 2 1 Channeltron Biasing The channeltron may be biased either positively or negatively With a negative bias the anode of the channeltron is at ground and the front end of the channeltron is held at a large negative voltage This biasing configuration serves to repel negatively charged ions or electrons from the front end of the channeltron Positive ions in the chamber produced from the ion gauges or from the x ray beam hitting the sample will be attracted to the channeltron Some of these ions will be intercepted by the grid in front of the channeltron which is also held at a large negative bias The back of the channeltron is held at 100V above the channeltron anode to ensure that electrons in 3 Delta Part UG 931 U www deltarf com purchased from M amp S Electronics Inc 3 part KAP 1CX 60AF500sMHV June 15 2012 REIXS Beamline RSXS Endstation User s Manual Page 22 the channeltron are accelerated to the anode rather than the back of the channeltron A high voltage divider shown in Figure 8 can be used for the biasing so that a single high voltage power supply such as the FAST Comtec NHQ 203M can be used to supply the appropriate voltages to channeltron HV 2500
47. tup To set up a motor 1 With the mouse click on the chosen motor Two theta Theta etc on the SPEC Motors APS Motor Record Control Screens 2 Click on the orange button indicating the process variable name assigned to that motor ex SMTR1610 4 122 01 for Two theta This will call up another window Common Motors maxvMotor edl In this window there are tabs at the bottom to select the parameters of the motor For our purposes the important tabs are POWER BRAKE and LIMIT SW BACKLASH e POWER There are 4 modes of operation ON and OFF apply either full power specified by the E DC motor driver hardware or no power respectively AUTO HARDWARE instructs the motor driver to only apply power when the motor is moving using the present configuration of the motor driver When the motor is not moving there is reduced or no holding current in this configuration The current default setting is ON Leave this setting ON for Two Theta and Theta motors and change this setting to AUTO HARDWARE for all other motors e BACKLASH The backlash is specified in Amount as the number of motor steps There are 4 settings NO YES FAVORED and DIR CHANGE NO will apply no backlash correction for any move YES will apply a backlash correction for every move regardless of direction FAVORED will only apply a backlash correction in one direction INCREASE or DECREASE
48. ur months to the gears in UHV The WS2 powder can be mixed in Methanol and spread over the gear teeth Pay special attention to the gears in the Two Theta and Theta motions Sample Holder The sample holder and sample receptacle was designed by David Hawthorn based on a design used by Christian SchuBler Langeheine in the Wesche RSXS chamber at BESSY As shown in Figure 2 the sample holders have a wedge shape that mates with a wedge Shaped receptacle A 4 40 socket head cap screw is fixed to the sample receptacle but free to rotate is used to lock into a 4 40 thread on the sample holder and draw the sample holder towards the receptacle to make good thermal contact at the wedges of the sample holder The screw action is provided by a Ferrovac WM40 520 50 S magnetically coupled single shaft wobblestick manipulator with 3 32 ball head hex tool attachment Samples may be transferred into and out of the sample holder using a magnetically coupled sample transporter by releasing the screw and using the sample transporter to clamp onto the stainless steel eyehole protrusion on the sample holder Two types of sample holder have been developed for the RSXS endstation a plain flat sample holder and a sample holder that accommodates a cylindrical plug sample holder This latter sample holder allows for continuous azimuthal rotation of the sample in vacuum The sample holder is attached to the diffractometer via a thermally isolating support structure desig

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