Home

GPS User Guide - Paul Scherrer Institute

1. gt e o e710 o e jm jI e ja s x rm R RI R Pl Figure 25 Diagram of the back connector of the Gossen power supply Up rep resents the voltage provided by the temperature controller max 10 Volts Kar is fixed at XXXX Ohms and Rp at XX Ohms The current furnished will be given by Ur X Rp X Irs 0 6 x Rar where Irs represents the current full scale of the Gossen power supply see Gossen manual Note that when used on the second port of GPS the settings of the Gossen power supply can be toggled between the 4 K CCR configuration and the Ziirich oven configura tion see Figure 18 with the help of a switch located near the Gossen power supply on the dedicated SCP rack 62 8 TOP LOADING JANIS 4 K CLOSED CYCLE CRYOSTAT Part HI 8 3 Setup made by the Instrument Scientist For the LTR regime two PID tables have to be prepared in the back end computer psw408 with name ccr_janis_stick_low pid and ccr_janis_cryo_low pid They have to be stored in the directory usrdisk0 musr exp td_musr dat 1s340 ccr_janis_stick_low pid 1 analog loop zone file for the janis CCR4K stick at low temperature BA35 CDISP lt loop gt lt resistance gt gt O lt resistance gt Loop 1 only CLIMIT lt loop gt lt S
2. Transfer 80 K Shield Temp _ y line Sensor I PS Temp Sensor AM _ PS Heat 20 K Shield Temp lt ar Sensor f Tube Temp Sensor Tube Heater Holder Temp Holder Heater lt Sensor Diffuser Temp S Sensors N Low Temperatures Diffuser Heater Figure 9 Temperature sensors and heaters In this regime the manual valve V2 should be kept fully open No current should be sent to the Tube Heater If a base temperature of 2 1 K is enough for the foreseen measurements the PUMP2 B should not be used Control that it is switched OFF If a base temperature of 1 8 K is required the PUMP2_B should be switched ON The lowest stable temperature is then obtained by gradually closing the needle valve V4 As the valve is closed the pressure P2 will gradually decrease and the sample temperature will decrease correspondingly Do not forget to change the setpoint temperature of the temperature controller When the minimum flow is reached further decrease in the needle valve V4 will result in a rapid warmup of the sample In this case the needle valve should be slightly opened and the same operation as above should be repeated During test runs stable base temperatures could be obtained with the fol lowing parameters 22 6 QUANTUM CRYOSTATS Part III Configuration Taif fuser P2 F2 PUMP2_A 2 15K 32 mbar 5 l min
3. Z if y 2m p Figure 1 Location of the 4 RGS buttons of the TM3 2 area 2 2 Entering the area from Red to Yellow To enter in the area for a short time the user will have to perform some simple opera tions Close the beam blocker by pushing the button ZU on the grey box located on the left hand side of the door Kanalverscluss KSE301 Wait until the red led ZU in ON Call the Control Room via the black CALL button CCTV camera and light should come ON Be prepared to unlock a black key The operator will switch the entrance gate on the yellow state Immediately after that the black keys will be released hear the characteristic click Each person going in the area should unlock a black key Put one black key in the door lock and turn it clockwise When the buzzer is heard push the door handle very gently down and open the door Enter and close the door When finished go back to the door Push the CALL button on the door CCTV camera and light should come ON When you hear the buzzer put your black key in the door lock and turn it coun terclockwise or press the little black button near the lock and gently push down the door handle Come out close the door and put back the black keys in their slots The operator shoul
4. Figure 13 Temperature dependence of the He flow through the Sample Chamber flow F2 in the High Temperature regime i e for 5 K lt Tyif fuser lt 300 K This flow should be controlled by the valve V3b If the recommended low values of flow are not applied at high temperatures a temperature gradient is usually observed in the sample chamber Part III 6 QUANTUM CRYOSTATS 27 Cryostat 9512 He flow through the Sample Chamber High Temperature regime 22 20 18 _ 16 E 14 10 10 8 O N A O 0 5 10 15 20 25 30 35 40 T K Figure 14 Temperature dependence of the He flow through the Sample Chamber flow F2 in the High Temperature regime i e for 5 K lt Taiffuser lt 300 K This flow should be controlled by the valve V3b If the recommended low values of flow are not applied at high temperatures a temperature gradient is usually observed in the sample chamber 28 6 QUANTUM CRYOSTATS Part II 0 10 20 30 40 50 Time min Figure 15 Example of heating and cooling curves solid line Taiffuser dashedline Tholder Note the large time difference between a heating and cooling process At higher temperatures the time difference and the undershoot of Taif fuser When cooling due to the rapid change of the He capillary impedence are much more pronounced Part HI 6 QUANTUM CRYOSTATS 29
5. These temperatures are obtained by adjusting with the valve V the mass flow through the pump PUMP During test runs stable Tps could be achieved with the following flows Cryostat Fl Quantum 9505 13 0 l min Quantum 9506 11 5 l min Quantum 9512 12 5 l min It is not advisable to operate with a too high flow value for which temperature instabilities are again observed The He gas entering the Sample Chamber is heated at the desired temperature by means of the Diffuser Heater DH and its temperature 77 fuser 18 monitored by a Cernox temperature sensor loop 1 of the temperature controller Depending on the desired temperature range a heater Tube Heater located on the He capillary after the needle valve V4 see Figure 9 is used to prevent the sudden flow of liquid helium in the Sample Chamber In order to obtain a faster response of the system a second heater loop is placed on the Sample Stick temperature sensor Cernox connected to the loop 2 of the temperature controller The operation may be divided into two overlapping temperature ranges e 2 1K or 1 8K using also the PUMP2_B lt Tyampie lt 10K Low Temperatures e 4K cryostat 9512 or 5K cryostat 9505 amp 9506 lt Tyampie lt 300K High Temperatures Part HI 6 QUANTUM CRYOSTATS 21
6. 62 9 Closed Cycle Cryostat Mark I 66 91 T krodueh n ss see aa RE AG mek dk Eeg dr ale Be 66 92 Temperature controls ece 6s baw ee alke eg kam pee ees 66 93 Samplechange lt o oak ee paper akk GAGE b e se 67 Part CONTENTS 3 IV Instrument magnetic fields 70 10 Zero field 70 11 GPS magnets 71 111 Introduction sara e ee we ee ee 2 71 VU MN AMONG vB cg god Boe era A Se 71 113 Phase Shits ee ew OA ke ee ee eS 71 V The muon beamline 74 12 Beam line power supplies and settings 74 151 The beamline sac doe Bee be ee ee ek 74 12 2 Setting the beamline lt s e 2 404 44484 2456 24 76 13 The spin rotator 78 13 1 Longitudinal geometry 78 13 2 Transverse geomety sasoca Re EE Re Ye 78 13 3 Conditioning and maintenance 78 14 Muons on request MORE 80 14 1 Introduction es e scie pete eee e Be EE A 80 14 2 Experimental Setup in the TM3 Area 80 14 3 Advantages but eee ee ee 81 14 4 Setting up the MORE mode o 82 15 Vacuum 83 VI Beam properties 85 16 Beam spot size 85 17 Range 86 18 Effect of the field on the 0 parameter 86 19 What to mind when determining the parameter 90 VI Annex A 92 20 Magnet power supplies 92 201 List ot power supplies pioc gk kee Oe be RA 92 VIII Annex B 93 21 MOGLI Quick references 93 21 1 Staring MOGLI sa g abre e ee hee eR RS 93 21 2 MOGLI Running EG EOG Se ss akg es ere amp Cae ee he
7. Up stream Material Thickness Heat Shield Superinsulation Aluminized Mylar 10 um 2 layers Sample Chamber Window Titanium 10 um Same for down stream e Window sizes In Out Heat Shield 29 0 mm diam Sample Chamber Window 15 mm diam 20 mm diam 44 6 QUANTUM CRYOSTATS Part HI 6 4 Additional Information 6 4 1 Temperature Controller The Conductus temperature controller connected to the Quantum cryostat is usually utilized in a REMOTE mode and can be directly controlled from deltat The fol lowing steps describe how to initialize configure and use the Conductus temperature controller from deltat Configuration Each time that you change the configuration of the cryostat new sample stick you have to configure the driver controlling the temperature controller In the tab Modify Devices choose the temperature controller entry and hit the buttons Modi fy and on the pop up window Modify Setup Choose the corresponding sample stick from the drop down list Hit the Next button and choose the corresponding Ent ry for your setup Remember that the QUANTUM is usually controlled by the Conductus in a two loop mode Hit the Apply Exit button and at this point the software should au tomatically detect the PID tables needed and load them into the Conductus temperature controller Remember to put the controller in the CONTROL mode Setting a temperature In the tab Modify Device
8. 0 832 0 25 50 75 100 125 Field Oe Figure 43 Field dependence on the determination of the parameter a by using the WEP magnet in the longitudinal polarization Note the much larger shift for the 0 parameter of the Up Down counters compare to the one of the Forward Backward counters The Forward Veto counter was aded in the definition of the Forward counter When performing zero field experiments in the longitudinal polarization i e using not only the Forward Backward detectors but also the Up Down ones the users should determine the Up down G parameter using the WEDLow Magnet and not the WEP one This again arises from to the vertical shift of the beam spot on the target produced by the WEP magnet see Figure 44 Part VI 19 WHAT TO MIND WHEN DETERMINING THE o PARAMETER 91 1 02 1 00 WEDL scan 0 98 oO E 2 lt 0 96 o WEP scan 0 94 0 20 40 60 80 100 Field Oe Figure 44 Field dependence on the determination of the parameter 0 for the Up Down counters by using either the WEDLow or the WEP magnets with a beam having transversal polarization Note the much larger shift for the 0 parameter when using the WEP magnet due to the vertical shift of the beam spot on the target VIL Annex A 20 Magnet power supplies 20 1 List of power supplies Table 15 List and specification of the magnet power supplies for the TM3 beam line A layout of the power supplies location is given on the Figure 30 on page 7
9. A I s F Part II 5 COMPUTERS AND ELECTRONICS 15 5 1 1 New TDC Electronics Introduction Layout VME Crate The new electronics consists of a VME crate with programmable constant frac tion discriminators CFD PSI CFD950 a multihit TDC CAEN V1190 for digitizing of time information and a scaler module SIS3820 for rate measure ments The VME frontend process to readout the VME TDC data is running on a front end Linux PC and connected to the VME crate by a SIS 1100 3100 VME PCI interface The complete event evaluation is done by software the TDC is operated in Continuous Storage Mode and the frontend process reads all the TDC data It searches for events that fulfill logics conditions The data are sent to the Analyzer process running on the Backend which builds the histograms taking into account post and pre pilup conditions as well as logics conditions see also Section 4 The system is also characterized by its flexibility as the whole logic diagram is simply stored in special setup files which can be easily modified and loaded for a desired configuration into the online database ODB of the MIDAS DAQ system The Figure 7 represents schematically the different modules used in the VME crate The analog signals are split by an active signal divider SP950 into a timing branch sent to the CFD CFD950 with 8 input channels and a monitoring branch for CFD threshold adju
10. 250 200 50 i 300 200 50 3 0 4 V e o G d DO SFP WY KA os s IV Instrument magnetic fields 10 Zero field Zero field compensation is regularly performed by the Instrument Scientist Since this operation is quite delicate and requires that the cryostat is at room temperature the users are not allowed to perform it themselves Extensive tests have shown that a weak remanent field is present at the sample region after that the main field WED has been set to high values This field has a value of few hundreds of milliGauss and is directed approximately along the beam direction angle of about 20 degrees High statistic runs have demonstrated that this field can be completely suppressed by applying for a very short time a small field of 100 Gauss with the auxiliary coils WEP After such a WEP cycling zero field is dynamically obtained compensation better than 30 mG by a newly installed automatic compensation device Such compensation relies on a continuous field measurement realized slightly off center The correction due to the off center position is taken into account and regularly calibrated by the Instrument Scientist When performing measurements in applied such as Knight shift measurements any stray fields created by the major magnets located in or near the experimental hall are tabulated and automatically compensated by the automatic compensation device See here for more information reachable from PS
11. 6 2 3 Configuration in the 7M3 area Pump PUMP1 Gast membrane pump Pump PUMP2_A Alcatel ADP 30 oil free pump Pump PUMP2_B Alcatel RSV 151B roots pump Electromagnetic Valve V3b PFEIFFER EVR116 valve controlled by a PFEIF FER RVC300 valve controller located in the beam area The He flows are measured by two Hastings transducers connected to two Hast ings flowmeter display The units are directly liters gas minute The maximum flow which can be mea sured is 50 l min The temperature of the Sample Chamber is controlled by a Conductus LTC 20 temperature controller The temperature of the Diffuser T r fuser 18 measured on the channel 1 loop 1 The temperature of the Sample Holder Tholder is measured on the channel 2 loop 2 The voltage loop 2 of the Conductus controls an external Gossen power supply The Tables 1 and 3 first loop and 4 5 and 6 second loop indicate the value of the PID parameters used by the temperature controller for the two loops A CryoCon 14 or LakeShore 208 thermometer display indicates the tempera ture of different heat shields and of the Phase Separator The temperature of the Phase Separator Tps is usually measured on the channel 1 The temperature of the He capillary Tube after the needle valve is usually measured on the channel 2 6 QUANTUM CRYOSTATS Part HI Table 1 Cryostat 9505 PID parameters for the Loop 1 diffuser of the temperature controller
12. PUMP2_A PUMP2_B 1 8K Smbar 5 l min Higher temperatures up to 10 K are achieved by keeping the He flow constant and solely changing the setpoints of the temperature controller Note that a temperature scan in this regime is only possible once the pressure and flow conditions necessary to reach the lowest temperature are obtained Typically for the lowest temperatures one will observe a situation with Taiffuser Slightly above Thoider Upon warming up Tjolder Will increase faster than 77 fuser in Such a way that both sensors will measure a similar temperature around 3 K At higher temperatures Tholder lt Tdiffuser and the difference reaches about 1 K at 15 K with PUMP2_A PUMP2_B Extensive tests performed by H Luetkens have show that the temperature of the sample closely follows the holder temperature aider at all temperatures see Figs 10 and 11 This is true independently of the sample mounting on a silver holder or on a fork Therefore in view of the observed temperature gradients in this tempera ture regime users are advised to control the temperature by solely setting a setpoint for Ty fuser This can be achieved by putting an arbitrary setpoint of say 1 K for Tholaer Alternatively the temperature controller can be set on a one loop mode For more details see section 6 4 1 The temperature of the sample is the one given by Thotder Part HI 6 QUANTUM CRYOSTATS 23 Sample Holder Fork Di
13. A stopping muon is defined as Mstop M V where V represents a veto event which is defined as V B BR BU BP or V Be Be Bog Beg Freto in the case of small samples where part of the Forward detector is used as veto Similarly a positron event is defined as P Pye Part II 4 THE DETECTORS 13 In addition the electronics checks for double events making sure that the detected positron can unambiguously be connected to a given decaying muon 14 5 COMPUTERS AND ELECTRONICS Part II 5 Computers and Electronics 5 1 Data acquisition and Electronics Figure 6 shows the overall interconnection of the various hardware items for the GPS instrument For the normal users the main item is the Linux console pc11318 This machine is used as an interface for the actual back end Linux system psw415 located in the WHGA building and which runs the data acquisition Network backbone Fast Electronic Frontend 1 4 VME Crate I rA a CFD amp TDC E a gt E y RS232 y LAN GPIB RS MSCB N I N 1 i WHGA U121 i i i 1 Li BE Console pc6012 Beamline Client pc8290 mrk i 1 i q 1 N N an Bo 7D E gt 1 i 1 N 1 i 1 Loo eee ee SS CUPS Printer WEHA_EG_1 Y Figure 6 The overall interconnection of the various hardware items for the GPS in strument
14. Solution check wiring let VP run separately external power HP ERROR No feedback HP ok after 30 seconds Solution check wiring and TCU START TIME ERROR GP gt 0 1 mbar after 10 minutes Solution Check Pirani Gauge and vacuum connections up to HV RECOVERY TIME ERROR GP gt 0 1mbar after I hour when HV open Recipient Volume could be to big Solution Make sure FV and FVHP are closed Check GP and GH INGRESS OF AIR GH gt 1 mbar when HV has been open Most probably a leak in the vacuum system Solution Fix it COMPRESSED AIR ERROR Valves do not react Solution check compressed air connections If you fixed an error press ERROR RESET F5 If the problem is solved the error message does not appear anymore Part VIII REFERENCES 95 References 1 J H Brewer et al Hyperfine Interact 66 1990 1137 2 J L Beveridge et al Z Phys C 56 1992 S258 3 R Abela A Amato C Baines X Donath R Erne D C George D Herlach G Irminger I D Reid D Renker G Solt D Suhi M Werner and U Zimmermann Hyperfine Interact 120 121 1999 575
15. gt At this point the power supplies should ramp up to the desired values For the high voltage power supplies block the setting is not automatic and one should additionally press the drop down list on the right hand side and choose the option HVSET Note that the setting of the high voltage power supplies can take several seconds e When saving the current setting the value in the column Set value will be written in the file and the colum File value will be updated accordingly Due to hysteresis effects cycle the steering magnets SSK31 SSK32 and SSK33 set their minimum values either 10 or 15 Amps wait few seconds and put back the proper initial values of the file By going from transverse to longitudinal mode it is sometimes necessary to retune the spin rotator value Note that this retuning could be necessary over a long time scale hours If better settings are found it is strongly requested to save them with the standard notation and by doing a proper entry in the logbook to the benefit of the following Users NEVER OVERWRITE EXISTING SETTINGS TT 12 BEAM LINE POWER SUPPLIES AND SETTINGS Part V es Jayanbi7 H OL Auogjeg seYNIMS winnooe yawn 1 1 l 1 I i 1 I i i 1 I 1 1 I i 1 l p 1 I 4 l 1 L i if I 1 l 1 l 1 1 l seaso veaso 9e1s0 ee1so oeaso ce uss aam 103M aam 18350
16. gt C lt heater max current gt Loop 1 only 1 0 25A 2 0 5A 3 1 0A 4 2 0A gt R lt heater max range gt Loop 1 only 0 5 1 heater loop is used 25 Ohm heater 310K max setpoint 2A max current 4 max range 0 25 S 310 C 4 R 5 lt zone gt lt top T gt lt P gt lt I gt lt D gt lt Mout gt lt range loopl only gt ESTO eens 0 0 1000 0 0 0 1000 0 0 1000 0 0 lt heater max range gt 1 IZ TPIDMR 1 84 3042 307 04107033 30 30 30 0 0 4 607 12 50 15 0 0 5 130 5 16 8 0 5 v fF WN RA e 66 9 CLOSED CYCLE CRYOSTAT MARK I Part HI 9 Closed Cycle Cryostat Mark I 9 1 Introduction 9 2 Temperature control The CCR can be operated between room temperature and about 10 K The sample holder is connected to a cold finger and the CCR is operated in vacuum Therefore the users should take care to obtain a good thermal contact between the sample and the holder An appropriate method should be used to attach the sample to the holder The CCR sample holder is similar to the one used for the Quantum cryostat see Fig ure 17 The CCR is usually installed on the 2nd cryogeny port of the GPS instrument As opposed to the situation in the Quantum cryostat the vacuum chamber around the CCR is separated from the main vacuum of the spectrometer Figure 26 shows the pump connections to the CCR Therefore independent pumps are necessary to evacuate this chamber usually a
17. v fF WN RA e 64 8 TOP LOADING JANIS 4 K CLOSED CYCLE CRYOSTAT Part HI For the HTR regime two PID tables have to be prepared in the back end computer psw408 with name ccr_janis_stick_high pidand ccr_janis_cryo_high pid They have to be stored in the directory usrdisk0 musr exp td_musr dat 1s340 ccr_janis_stick_high pid 1 analog loop zone file for the janis CCR4K stick at high temperature AA35 CDISP lt loop gt lt resistance gt gt O lt resistance gt Loop 1 only CLIMIT lt loop gt lt SPlimit gt lt heater max current gt lt heater max range gt gt S lt SetPointlimit gt gt C lt heater max current gt Loop 1 only 1 0 25A 2 0 5A 3 1 0A 4 2 0A gt R lt heater max range gt Loop 1 only 0 5 1 analog loop is used 475K max setpoint S 475 lt zone gt lt top T gt lt P gt lt I gt lt D gt lt Mout gt lt range loopl only gt de is 0 0 1000 0 0 0 1000 0 0 1000 0 0 lt heater max range gt 1 IZ TPIDMR l 1 450 90 7 3 0 0 Part HI 8 TOP LOADING JANIS 4 K CLOSED CYCLE CRYOSTAT 65 ccr_janis_cryo_high pid 1 heater loop zone file for the janis CCR4K cryo at high temperature AA35 CDISP lt loop gt lt resistance gt gt O lt resistance gt Loop 1 only 1 l CLIMIT lt loop gt lt SPlimit gt lt heater max current gt lt heater max range gt gt S lt SetPointlimit gt
18. 500 1000 1500 2000 2500 3000 3500 Field Oe Figure 28 Measured phase shifts as a function of the applied field WED for different detectors by courtesy of Joao Gil This negative time spin rotation introduces a field dependent phase shift for the de tectors Up Down and Right see Figure 28 The observed phase shift corre sponds almost exactly to the calculated one based on the field profile shown in Figure 27 Hence the phase increase due to the field profile represents about 0 0231 de grees Gauss V The muon beamline 12 Beam line power supplies and settings 12 1 The beamline The 7M3 beam line is currently the only beam line dedicated exclusively to uSR exper iments with surface muons although the original channel was optimized for pions of up to 350 MeV c It is attached to the thin target M at 22 5 in the forward direction see Figure 29 A 3 m long crossed field separator built at CERN can be used either as an electron muon separator or as a muon spin rotator Due to the optical character istic of this device its transmission depends strongly on the high voltage settings A compromise between high rates and a high degree of transverse polarization has been found experimentally and a muon spin rotation angle as large as 50 is used routinely More information on the nM3 beam line can be found here http aea web psi ch beam2lines beam_pim3 html Part V 12 BEAM LINE POWER S
19. 7 ZURICH OVEN 51 roove for Thermocouple Based on standard Sample Holder MSR 10 02 001 Only modifications shown Benennung Merkmale 27 09 2004 Reto Balz 2 1 Ersetzt durch El Baugruppe Stueckl Nr Blatt Nr Zusammenst Nr 1 Sample Holder Oven MSR 12 03 010 Zurich Oven Figure 21 Dimensions of the sample holder to be used in the oven Only the modifications to the standart sample holder are shown see Fig 17 52 7 ZURICH OVEN Part HI 7 4 Setup made by the Instrument Scientist if a LTC Controller is used Since the Conductus Neocera can only handle temperatures up to 799 K and voltages up to 5 8 V one has to define the output analog voltage limits of the PUS accordingly Table 8 Correspondence between displayed temperature and analog output of the PUS Display to allow a full scale measurement 800 K on the Conductus Neocera temper ature controller PUS Display Analog Output Celsius Kelvins Volts 0 273 1 0 0 526 9 800 0 5 8 908 4 1185 5 10 0 The 10 V value corresponds therefore to 908 4 and has to be set accordingly into the PUS Display To change the analog output value you must keep P pushed and change with DOWN or UP to the Parameter P20 Then release P and change with DOWN or UP the value You can skip a digit by pushing P Once your desired value is entered you have to push P for 3 seconds Horizontal lines on the display indicate that the
20. Hazardous samples removal from the area have to be recorded by the Spokespersons in the corresponding Logbook Hazardous Samples Logbook located in the Counting Room uSR measurements on radioactive material must be performed on hermetically sealed samples preventing any possible contamination All radioactive material has to be properly labeled allowing complete identification at all times and by any person Any unexpected event or any suspicion of an unexpected event involving radioactive material loss suspected contamination etc must immediately be reported to the Radiation Protection Group the phone number of the Safety officer responsible for the GPS area can be found on a yellow panel at the entrance door to the experimental area Outside working hours the report has to be given to the Accelerator Control Room internal telephone number 3301 or 3302 Removal of radioactive material from the PSI site will be allowed only after fulfilling the required formalities and is subject to authorization from the Radiation Protection Group and the Safety Officer for Transport of Radioactive Material USR measurements on hazardous material must be performed on hermetically sealed samples preventing any possible contamination All hazardous material has to be properly labeled allowing complete identification at all times and by any person All information type of material packing and any operation performed on hazardous material
21. eegs0 seiso zelso mav zeyss 1893S HESSV i 1 l 1 I 1 I 1 I d l 1 1 T 1 1 i 1 1 l 1 L l 1 I I 1 i 1 1 l tt I i it E I 1 i i 1 SE3SO LEISD peso LEISO ZEJSO LESS 90 380 0 aso ZENSV 908 350 zoe 350 jonuog EIS pog ASO Loe 150 OUD suis LEISV zoe 180 LOS 350 Sold uiged Sd9 Pue Kejeg oL Figure 30 Location of the nM3 beamline power supplies located on the platform above the GPS cabin The list of the power supplies is given in the Table 20 1 at the page 92 78 13 THE SPIN ROTATOR Part V 13 The spin rotator The spin rotator consists of mutually perpendicular electrical and magnetic fields It can be used either as a separator in longitudinal geometry or as a spin rotator in transverse geometry 13 1 Longitudinal geometry 13 2 Transverse geometry It this configuration the spin rotator is used as a separator The settings of the two fields are correlated so that muons of a particular velocity are transmitted The r le of the separator spin rotator is to remove contaminant particles primarily positrons from the muon beam When the muon beam is deflected by a magnetic field the spin and momentum vectors remain collinear However the same is not true if the beam is passed through an electric field when the muon spin is rot
22. entrances of the TM3 2 GPS and TM3 3 LTF area Note that the valves VSD31 and VSD321 are coupled with the beam blockers of the TM3 1 and TM3 2 areas respectively Thus these valves can be operated between positions CLOSE and OPEN only when the respective beam blocker is OPEN If the latter is CLOSED the valve can only be operated between positions CLOSED and SCHARF i e READY TO OPEN In the SCHARF position the valve will automatically open when the beam blocker will pass in the OPEN position The beam blockers can either be opened locally at the respective doors or through the EPICS control system see Section 12 2 Pressure sensors are located along the beamline at the pumps level The pressures can be read from the same touch panel 84 15 VACUUM Part V v 4 m y 5 eparator in a Figure 35 Display of one of the screens of the vacuum touch panel located near the entrances of the 7M3 2 GPS and 7M3 3 LTF area During normal operation all the valves along the beamline should be open i e green on the display Also all the turbo molecular pumps should be running i e green on the display The rough pumps will only be automatically switched ON when needed pressure in the buffer tank exceeding a given limit VI Beam properties 16 Beam spot size The beam spot size at the sample position is mainly determined by the shape of the hole in the Backward Veto detector Hence this beam s
23. ha ee ee es 94 Laboratory for Muon Spectroscopy A Amato amp H Luetkens June 2015 I Introduction 1 Regulations 1 1 Generalities 1 2 Dosimeters 1 3 Reachable users 1 4 Sample mounting 1 5 Radioactive samples 1 5 1 Transport and handling The Experimental Hall is classified as a Zone 1 area It is therefore not allowed to drink or eat in the Hall including in the Counting Room When leaving the Hall each user will have to check for possible contamination Please use the available hands and feet detectors All material leaving the Zone 1 area has to be checked by a Safety Officer SU Kontrolleur The phone number of the Officer on duty is indicated near the main exit When working in the Experimental Hall each user will have to carry his dosimeter The dosimeters are provided during the working hours by the dosimetry office located near the reception building WLGA During non working hours the dosimeters will be provided by the entrance guard To obtain a dosimeter a short and easy exam will be required Inform yourself at the dosimetry office Building WLGA for further details Users are requested to remain reachable at all time during the experiment by the Con trol Room and or the instrument scientist A mobile PSI phone 5880 is available for the person on shift and should be carried also in the PSI Guest House Please deposit this mobile phone in the GPS counting room at the end of y
24. is used or by switching the corresponding button on the HECTOR unit in case that a LS340 is used This last point can be performed directly from the Console running the pro gramme deltat Part HI 9 CLOSED CYCLE CRYOSTAT MARK I 69 9 4 Setup made by the Instrument Scientist if a LakeShore 340 Controller is used A PID table has to be prepared in the back end computer psw408 with name ccrl pid It has to be stored in the directory usrdisk0 musr exp td musr dat 15340 ccrl pid heater loop zone file for CCR1 cryostat RA36 21 NOV 2006 zone table taken from Christoph Boo Bericht l CDISP lt loop gt lt resistance gt gt O lt resistance gt Loop 1 only 1 i CLIMIT lt loop gt lt SPlimit gt lt heater max current gt lt heater max range gt gt S lt SetPointlimit gt gt C lt heater max current gt Loop 1 only 1 0 25A 2 0 5A 3 1 0A 4 2 0A gt R lt heater max range gt Loop 1 only 0 5 1 heater loop is used 25 Ohm heater 300K max setpoint 2A max current 4 max range 0 25 5 300 C 4 R 4 lt zone gt lt top T gt lt P gt lt I gt lt D gt lt Mout gt lt range loopl only gt LISTO I dei 0 0 1000 0 0 0 1000 0 0 1000 0 0O lt heater max range gt 1 IZ TPIDMR 350 50 15 0 3 300 50 0 300 30 5 7 1707 15 3 200 12 3 gt N N ol 00 200 50 3 50 200 50 3 3 3 200 200 50 A A SP MD
25. of the electrovalve V3b the yellow valve VI on the transfer line pump use the closing ring Lift up slightly 50 cm the transfer line on the He dewar side the bottom part of the tranfer line in the He dewar should now be above the liquid He level Open the needle valve V4 completely Pressurize slightly the Phase Separator with He gas by opening the valve V5 until you reach a pressure PI of about 1000 mbar check if the He gas cylinder is open Check carefully and frequently the pressure P and P2 in the Phase Separator and in the Sample Chamber An overpressure in the Sample Chamber could damage the titanium windows Disengage the adaptor of the transfer line from the top of the dewar by releasing the O rings Slide the adaptor upward along the transfer line Remove completely the transfer line on the He dewar side Replace the plug of the He dewar to prevent freezing of the He dewar Connect the transfer line to the He recovery line If time is not pressing stop blowing He gas in the system by closing the valves V5 blowing He gas in the system will speed up the warming process but will introduce an additional hazard factor Switch OFF the two vacuum pumps Part HI 6 QUANTUM CRYOSTATS 39 6 2 8 Trouble shooting This section is hopefully intended to help the user coping with several known problems e In the High Temperature Regime Ty r fuser 18 oscillating Check that the needle valve V4 is 0 5 mm
26. open 50 units very sensitive Check that the Tube Heater is switched ON Check that the He flow Fl through the transfer line is high enough the Tps value are given on page 20 Increasing F1 slightly usually helps to keep a stable Taif fuser e Temperature oscillations around 20 K in the High Temperature Regime Check that the Tube Heater is switched ON Close slightly the needle valve V4 e In the High Temperature Regime large temperature gradient and very low values of P1 The needle valve V4 is probably closed too much e In the High Temperature Regime one cannot reach the values of He flow needed to obtain the lowest temperature in this regime i e 4 or 5 K depending on the used cryostat Open slightly the needle valve V4 e In the High Temperature Regime large temperature oscillations are seen below 10 K Make sure that the setpoints for the two loops diffuser channel I and holder channel 2 are set to the same values The PID parameters are optimized only for this configuration e After a sample change or a long period at high temperature the lowest temper ature in the Low Temperature Regime can hardly be obtained by closing the needle valve V4 a large temperature increase is observed It is just a matter of waiting long enough If time is crucial it is advisable to perform a first run at about 2 5 3 K even without the optimal values of P2 and F2 see Section 2 2 2 but with F2 low enough to avoid temper
27. oxygen in solution in the blood will diffuse out causing a rapid collapse and possible death Every year people die when inhaling helium gas to try the squeaky voice trick A single deep inhalation of helium gas can be fatal 18 6 QUANTUM CRYOSTATS Part HI 6 2 Principle of operation 6 2 1 Description The QUANTUMCOOLER Continuous Flow Cryostat utilizes liquid helium as a coolant to provide stable controllable sample temperature The system is de signed for either vertical cold end down or horizontal operation For this reason the transfer line connection is at 45 degrees so that it can be operated in either position The system consists of 3 components e The QUANTUM continuous flow cryostat e The QUANTUM return vapor shielded liquid helium transfer line e The QUANTUM removable Sample Stick QUANTUMSTICK As shown in Figure 8 liquid helium from the supply dewar travels trough the center of the transfer line enters the continuous flow cryostat and the flow is split Sample Chamber Flow The first flow circuit is for sample cooling Liquid helium from the transfer line enters the top of the Phase Separator PS and the liquid from the bottom is ex panded through the needle valve V4 then is injected in the Sample Chamber The cold gas exits at the top of the Sample Chamber and the flow is controlled by the manual valve V2 and the electromagnetic valve V3b and the pumps PUMP2_A and PUMP2_B Heat Shiel
28. pim3 psi ch and is running under Linux account acsop and password PSIbeaml To use your PC or Laptop on the PSI Network you should enable DHCP to get a PSI TCP IP address regardless of what host name you choose CUPS printers are available in the Experimental Hall The printer WEHA_EG_1 is located on the gallery between the LTF and GPS cabin The printer WEHA_E5_2 is located in the Experimental Hall near the area TES It is also equipped with a xerox machine and a FAX These printers can be accessed from UNIX and Windows sys tems for Windows just type the print server adress in a Windows Explorer window Nwinprintw III Sample environment 6 Quantum cryostats 6 1 Safety 6 1 1 Hazards 6 1 2 Asphyxiation hazard The Quantum Continuous Flow Cryostat contains liquid helium Consequently like all equipment using cryogens certain hazards are present The potential hazards are catastrophic rupture of unvented vessels freezing damage from splashing cryogens and asphyxiation hazard from high concentrations of helium gas Catastrophic rupture can occur if a cryogen is held in a sealed container while warming The user should therefore ensure that the necessary valves of the helium recovery lines are kept open High concentrations of helium gas in a room constitutes an asphyxiation hazard Although non poisonous the gas may reduce the concentration of oxygen below safe levels When helium concentration is extremely high then the
29. software and should NOT be considered by a normal uSR user Figure 27 shows the WED field profile along the incoming muon beam In the trans verse polarization geometry this long field extension introduces quite a noticeable ro tation of the muon spin before the implantation into the sample see also Common Logbook 3 page 079 72 11 GPS MAGNETS Part IV Table 14 Relation between the DAC values and the actual field for the dif ferent power supplies WEP DAC Field G 500 16 385 1000 33 133 1500 49 586 2000 65 798 120 110 Fraction of nominal field 100 90 80 70 60 50 40 30 20 10 WED DAC Field G 51 12 63 508 57 76 3048 307 03 WEDLow 10082 9935 49 DAC Field G 15123 1489 07 0 0 285 20165 1982 64 100 24 291 25206 2475 66 500 120 315 32263 3165 98 1000 240 345 35288 3461 92 2000 480 405 40329 3955 08 45370 4448 50 50412 4941 96 55453 5435 00 60494 5928 00 65535 6421 50 WED 50 100 Distance cm The present values can also be found in the directory userdisk0 musr exp td_musr expmag of the Backend Figure 27 Calculated field profile WED magnet along the beam direction Part IV 11 GPS MAGNETS 73 400 350 Initial Phase 300 250 200 150 Phase degrees 100 50 0 0
30. stan dard MOGLI pumping unit Second Port Chamber V He Fiom Helium K er LEV MOGLT Pump Uniti K x 4 7 GH EE eC JX FVHP Bv X 1 GP Figure 26 Vacuum diagram for the CCR Two temperature sensors Cernox are used to monitor and control the temperature of the CCR They are both mounted at the end of the cold finger The PID values of the temperature controller are of course dependent on the temperature controller used Part HI 9 CLOSED CYCLE CRYOSTAT MARK I 67 9 3 Sample change Table 12 CCR PID parameters of the temperature controller LTC Conductus Neocera The P parameters are rounded when displayed by the controller The parameters are stored in a PID Table of the Conductus temperature controller The maximum power should be fixed at 20 CCR with LTC Break P I D Heater point K Range W 320 15 62 16 50 200 15 62 16 50 199 999 60 62 16 5 TT 60 62 16 3 50 42 50 16 5 40 35 37 9 5 25 22 23 6 5 20 22 23 6 5 19 999 100 15 4 0 5 1 4 100 15 4 0 5 Table 13 CCR PID parameters of the temperature controller Lakeshore 340 The P parameters are rounded when displayed by the controller The parameters are stored in a PID Table of the Lakeshore temperature controller CCR with LS 340 Break P I D Heater point K Range W 320 200 50 3 10 250 200 50 3 10 200 200
31. study of muon spin precession and relaxation easily up to 20us 10000 Silver Bo 10 mT 1000 Conventional uSR S 0 100 Fitted function e B N e 1 Ae cos at 9 Oo gt LLI 0 2 4 6 8 10 12 14 16 18 20 Time us Figure 33 uSR in silver in a magnetic field of 10mT measured at the GPS facility instrument in conventional and in MORE mode Insert Reduced asymmetry plot for the first 2us in MORE mode function fitted for t gt 0 4us 82 14 MUONS ON REQUEST MORE Part V In MORE mode with M counter trigger we observe a small distortion in the spectra at times t lt 450ns insert in Figure 33 which is due to the delay between the passage of the muon and the arrival of the trigger signal at the kicker During this time ad ditional muons can enter the spectrometer and kill events through pile up rejection Fitting the distorted spectra is possible using different values of the fit parameters NO normalizing constant and BO background in the two regions However the MORE technique is preferentially used for slow signals where cutting off the first channels does not affect the data analysis 14 4 Setting up the MORE mode To measure in MORE mode the following operations should be performed 1 Appropriate setting for the beamline magnets see Section 12 2 The kicker will be switched ON automatically The readback of the kicker should be about 4 6 corresponding to 4 6 kV 2 Ch
32. the computer has taken the control of the device In this case wait few seconds and restart the procedure The computer connects to the device every 30 seconds so be quick To rotate the sample remotely e In deltat the tab Modify Devices contains the device Position Choose this device and hit the Modify button Enter the new position value in the pop up window and close it e A rotation of the sample can also be included in a auto run sequence by using the command SET Position ANGLE 100 0 With this example an angle of 100 is requested Part HI 6 QUANTUM CRYOSTATS 47 6 4 4 Miscellaneous e The second loop of the temperature control utilizes the analog output of the temperature controller CONDUCTUS The output is utilized to control the Gossen power supply Figure 18 indicates the necessary settings to interface both instruments The maximum current for the Gossen is therefore limited to about 0 5 Amp M N PRS TUVWX Y Z j gt W 11O JJ j m lt E LID ef P RRI R PI t i Figure 18 Diagram of the back connector of the Gossen power supply Up represents the voltage provided by the temperature controller max 10 Volts KR is fixed at 2033 Ohms and Rp at 34Ohms The current furni
33. the valves V V3a When you are ready to insert the Sample Stick with the new sample you should follow an analog procedure as above Namely Stop the He flow through the pumps by closing the two valves V2 and V3a on the pumping line of the Sample Chamber do not disconnect the electrical plug of the electrovalve V3b the yellow valve V on the transfer line pump use the closing ring without changing the actual setting of the valve Pressurize slightly the Sample Chamber with He gas by opening the valve V6 until you reach a pressure P2 slightly above 1000 mbar check if the He gas cylinder is open Check carefully and frequently the pressures P and P2 in the Phase Separator and in the Sample Chamber Dismount the blind flange very shortly before inserting the Sample Stick Insert the Sample Stick carefully to insert a warm Sample Stick requires more force than to remove a cold Stick Replace the clamp Immediately stop blowing He gas by closing the valve V6 Restart the He flow through the He pumps by opening the valves V V3a and V2 if the low temperature regime is needed 34 6 QUANTUM CRYOSTATS Part HI e Readjust the He flows e When a sufficient He flow is detectable in the Sample Chamber set the temper ature controller in the Control Mode by pressing the Local button if necessary and pressing the Control button Note that if the sample stick was changed you will have first to configure t
34. time of entry to the experimental area handling measurements time of re moval from the area have to be recorded by the Spokespersons in the corresponding Logbook Hazardous Samples Logbook located in the Counting Room Part I 2 THE BEAM AREA 1M3 2 7 2 The beam area 1M3 2 During measurements the area is locked and its access is controlled by the so called PSA system and is directly supervised by the Control Room The entrance gate can be in 3 different states Green Yellow Red The access is free and everybody is allowed to enter the zone The beam blocker is of course shut The access is restricted and controlled by the Control Room The access in the area is possible if the beam blocker is shut but each person entering the area must take a black key The area is locked and nobody can enter in the area In this state the beam blocker is usually open and uSR measurements are possible 2 1 Closing the area from Green to Red To close the area the user will have to perform some simple operations Do first a quick check to ensure that the area is empty Go out and close the door Call the Control Room via the black CALL button CCTV camera and light should come ON Tell the operator via the microphone that you want to do a Rundgang Be prepared to unlock a black key The operator will switch the entrance gate on the yellow state Immediately after that the black keys will be rel
35. 0 30 30 4 50 60 40 30 5 5 30 40 17 2 3 15 40 13 2 5 10 10 9 I 5 8 10 10 1 5 4 50 5 1 0 5 3 100 10 1 0 5 1 500 10 1 0 5 The Table 4 Cryostat 9505 PID parameters for the Loop 2 Sample Holder of the temper ature controller The parameters are stored in a PID Table of the Conductus temperature controller Cryostat 9505 Loop 2 Break P I D point K 300 70 10 2 250 70 10 2 200 70 10 2 150 70 10 2 100 70 10 2 70 10 10 2 40 2 102 10 1 8 2 5 1 8 2 1 1 8 2 6 QUANTUM CRYOSTATS Part HI Table 5 Cryostat 9506 PID parameters for the Loop 2 Sample Holder of the temper ature controller The parameters are stored in a PID Table of the Conductus temperature controller Cryostat 9506 Loop 2 Break P I D point K 300 70 10 2 250 70 10 2 200 70 10 2 150 70 10 2 100 70 10 2 70 10 10 2 40 2 10 2 10 1 8 2 5 1 8 2 1 1 8 2 Table 6 Cryostat 9512 PID parameters for the Loop 2 Sample Holder of the temper ature controller The parameters are stored in a PID Table of the Conductus temperature controller Cryostat 9512 Loop 2 Break P I D point K 300 70 10 2 250 70 10 2 200 70 10 2 150 70 10 2 100 70 10 2 70 10 10 2 40 2 10 2 10 1 8 2 5 1 8 2 1 1 8 2 Part HI 6 QUANTUM CRYOSTATS 33 6 2 4 S
36. 2 0 5A 3 1 0A 4 2 0A gt R lt heater max range gt Loop 1 only 0 5 analog loop is used 1200K max setpoint s 1200 l lt zone gt lt top T gt lt P gt lt I gt lt D gt lt Mout gt lt range loopl only gt LEIOA teoria 0 0 1000 0 0 0 1000 0 0 1000 0 0 lt heater max range gt 1 1 1200 20 4 8 0 0 Parameters from Christophe Boo outdated 1 1 450 15 1 2 3 0 0 2 500 19 1 8 4 0 0 3 700 24 2 4 4 0 0 4 800 30 3 6 4 0 0 5 1200 50 6 5 0 0 5 54 8 TOP LOADING JANIS 4 K CLOSED CYCLE CRYOSTAT Part HI 8 Top Loading Janis 4 K Closed Cycle Cryostat 8 1 Introduction Since 2008 a top loading Janis 4 K CCR cryostat is available on the second cryogeny port SCP of the GPS instrument This Janis 4 K CCR can be operated between 4 K and 475 K though in different modes The 4 K CCR is usually installed on the 2nd cryogeny port of the GPS instrument As opposed to the situation in the Quantum cryostat the vacuum chamber around the 4 K CCR is separated from the main vacuum of the spectrometer Therefore independent pumps are necessary to evacuate this chamber usually a standard MOGLI pumping unit see also Section 21 When operating with the second cryogeny port the external part of the right positron detector is removed reducing further the counting rate of this counter The sample is connected to a sample stick located in a so called sample chamber This sample chamber
37. 2 and V3a Turn ON vacuum pumps PUMP and PUMP2_A Open carefully valves V5 and V6 to purge the cryostat Check carefully and frequently the pressure P and P2 in the Phase Separator and in the Sample Chamber An overpressure in the Sample Chamber could damage the titanium windows Insert slowly the transfer line in the new He dewar As soon as the sintered part is enough inserted in the dewar lower the adaptor and connect it to the dewar Make sure that the adaptor of the transfer line is well inserted in the dewar and that all O rings are tightened Leave the transfer line above the liquid He level Open the valves on both He pumps do not forget if necessary to connect the electrical plug of the electromagnetic valve V3b Wait 3 minutes Pull down slowly the transfer line in the He dewar Once Tps has reached its nominal temperature see page 20 the valve VI should be partially closed If an increase of Tps is observed this indicate that VI has been closed too much and insufficient helium is entering the system Once the optimum V setting has been achieved the sample temperature can be controlled as described in Section 6 2 2 38 6 QUANTUM CRYOSTATS Part HI 6 2 7 Shutdown procedure This section is not intended to a normal uSR Facility user Stop the He flow through the pumps PUMP and PUMP2_A by closing the two valves V2 and V3a on the pumping line of the Sample Chamber remove the electrical plug
38. 50 3 10 150 200 50 3 10 100 200 50 3 10 50 200 12 3 10 40 170 15 5 10 30 300 30 5 1 20 300 50 O 1 10 350 50 15 1 Heat the sample to room temperature and wait 15 min after reaching the set point Switch OFF the CCR compressor Immediately switch OFF the heater by putting the temperature controller to MONITOR mode if necessary depress first the LOCAL button in case that a LTC Controller is used or by switching the corresponding button on the HECTOR unit in case that a LS340 is used Stop pumping by swiching OFF the MOGLI pumping unit This is performed by pressing the button LOCK HV on the MOGLI Controller Remove the screws connecting the CCR to the vacuum chamber Slowly open the valve V He to admit He gas into the chamber Check carefully and frequently the pressure in the chamber do not go beyond 1000mbar Close valve V He Open the CCR 68 9 CLOSED CYCLE CRYOSTAT MARK I Part HI Change your sample If necessary remove the moisture of the CCR with a heat gun Insert the CCR and connect it to the vacuum chamber with the available screws Start pumping by pressing the button UNLOCK HV on the MOGLI Controller Note that the HV valve will only be open when pre defined conditions will be fullfilled Switch ON the temperature controller by pressing the button CONTROL if necessary depress first the LOCAL but ton in case that a LTC Controller
39. 7 Magnet Current Voltage Limitation QTH31 120 50 QTH32 50 50 QTH33 50 50 ASL31 50 12 QSL31 50 50 QSL32 50 50 QSL33 50 50 QSL34 50 50 ASL32 50 12 QSL35 50 50 QSL36 50 50 SSK31 10 24 SPIN ROT 500 80 SEP31 SPIN ROT 200 kV HV SPIN ROT 200 kV HV QSE31 50 50 QSE32 120 50 ASK31 120 50 QSE33 50 50 QSE34 50 50 SSK32 10 24 QSE35 50 50 QSE36 120 50 ASS31 500 80 SSK33 20 24 QSE37 50 50 QSE38 50 50 ASK32 50 12 QSE303 50 24 QSL302 50 24 QSE304 50 24 QSE301 50 24 QSL302 50 24 QSE302 50 24 WED 650 300 100 WEDL 50 24 100 WEP 200 50 100 VII Annex B 21 MOGLI Quick references 21 1 Starting MOGLI 21 2 MOGLI Running Make sure the power Netz is connected to a 380V plug socket and all devices are switched on Make sure the compressed air pipe is connected on the local compressed air sys tem Make sure all the vacuum parts are well connected and the manual flood valves are closed If the main switch is on 5FO the FPS display should show PST OFF HV LOCKED Decide wheter to UNLOCK HV or not F4 F3 If UNLOCK is choosen the HV valve will open when pre defined pressure conditions are fullfilled The recipient will be evacuated relatively fast For evacuating slowly fragile windows install an additional fine adjust valve between the recipient and the MOGLI u
40. GPS User Guide Contents I Introduction 1 Regulations LI Generabtes caco AA kA Le B e a CA eee BR ee ae A 13 Reachable users coi iaa eal eS RR akk A LA Sample omme 2 4 ia eee a KG Goes 15 Radidctive samples vs asar E ee Sa BAG 1 5 1 Transport and handling A Fe AA 153 Unexpected Byens ses E A 154 RemovaliromPS c 2 1 000 GS 16 Hagardous satoples 22 omar A G 2 The beam area TM3 2 2 1 Closing the area from Green toRed 2 2 Entering the area from Red to Yellow 2 3 Freeing the area from Red to Greed II The instrument 3 General description 4 The detectors 5 Computers and Electronics 5 1 Data acquisition and Electronics o o S1 1 New TDC Electonics saksere skam ee T SL2 Slow Contool oo abs EE REE ee EA ks SE HIRE GOTHI super BA ge Gea dele eda 5 3 Laptop connections lt s o ere ek saa RA Ga Ga SA EDADES ss os s ee e le bek kor ah hed Age ee ie da lete III Sample environment I DD NN DN Ur Ur Ur nnn A oo nN N 10 10 10 14 14 15 16 16 16 16 17 9 4 Setup made by the Instrument Scientist if a LakeShore 340 Controller IS MEE ji se a BG AA o bad eek CONTENTS Part 6 Quantum cryostats 17 Gl S pba es SEL AE pa s ket ea Eo 17 GLI Hazas oo osa Gus Al G r Ge dk Be ren en RS 17 6 12 Asphyxiation hazard op e ee ee RE ass 17 62 Principle Of Ope
41. I intranet http lmu web psi ch intranet manuals Zero_Field_ Compensation_Comprehensive_Manual pdf Part IV 11 GPS MAGNETS 71 11 GPS magnets 11 1 Introduction 11 2 Setting a field 11 3 Phase shifts Two sets of Helmholtz coils are available to produce magnetic fields at the sample position WED These are the main coils producing a field along the muon beam direction This field is used either for Longitudinal Field studies when the muon polarization is along the beam direction or for Transverse Field measurements when the muon spin is rotate with the Spin Rotator The maximum field reachable is 5 6 kG reduced field due to a problem of the magnet when the coils are operated with the WED power supply If low field value are required typically below 100 G or if a high stability for very low fields is required typically during muonium studies the power supply WEDLow can be utilized With this latter power a maximum field of 390 G can be reached WEP This pair of coils produces a horizontal field perpendicular to the muon beam direction along the cryostat axis This field is typically used for calibration purposes total asymmetry determination of the parameter alpha The highest field available is 60 G Both magnets are controlled by the deltat software To set a field choose the tab Exp Magnets choose the desired magnet and provide the new field value At this point the software will send the neces
42. PICS clients applications The heart of the EPICS control for the nM3 beamline is a VME crate located on the platform above the GPS cabin in the first left hand side row of power supplies This crate contains a processor module and the interface cards for the power supply In addition the old power supplies have an additional interface multi I O located in the same rack e The deltat Console is usually utilized to set the WED WEDL and WEP power supplies This is performed directly in deltat as explained in Section 11 2 e The PC is utilized to set the other power supplies This is performed by the application SetPoint This application which can be started either with the icon SetPoint on the Desktop or with the command line afs psi intranet HIPA Secondary bin setpoint_new tcl From this application one can set the magnets switch them ON OFF open close the beam blockers and also control the Spin Rotator high voltages Some standard settings are normally provided transverse or longitudinal mode shared or not shared MEG or not MEG The names are normally self explanatory How to set the beamline e Start the SetPoint application on the PC8290 see above e When loading a new setpoint file sp files the values are read and displayed in the column File value In order to set the power supplies one should select them via the button Select All for example and press the button Set File value
43. Plimit gt lt heater max current gt lt heater max range gt gt S lt SetPointlimit gt gt C lt heater max current gt Loop 1 only 1 0 25A 2 0 5A 3 1 0A 4 2 0A gt R lt heater max range gt Loop 1 only 0 5 analog loop is used 310K max setpoint s 310 lt zone gt lt top T gt lt P gt lt I gt lt D gt lt Mout gt lt range loopl only gt WAST Aiaia 0 0 1000 0 0 0 1000 0 0 1000 0 0 lt heater max range gt 1 IZ TPIDMR 1 450 90 7 3 0 0 Part HI 8 TOP LOADING JANIS 4 K CLOSED CYCLE CRYOSTAT 63 ccr_janis_cryo_low pid l heater loop zone file for the janis CCR4K cryo at low temperature 1 AA35 CDISP lt loop gt lt resistance gt gt O lt resistance gt Loop 1 only 1 l CLIMIT lt loop gt lt SPlimit gt lt heater max current gt lt heater max range gt gt S lt SetPointlimit gt gt C lt heater max current gt Loop 1 only 1 0 25A 2 0 5A 3 1 0A 4 2 0A gt R lt heater max range gt Loop 1 only 0 5 1 heater loop is used 25 Ohm heater 300K max setpoint 2A max current 4 max range 0 25 S 310 C 4 R 5 lt zone gt lt top T gt lt P gt lt I gt lt D gt lt Mout gt lt range loopl only gt ESTO eens 0 0 1000 0 0 0 1000 0 0 1000 0 0 lt heater max range gt 1 IZ TPIDMR 1 84 3042 307 04107033 30 30 30 0 0 4 607 12 50 15 0 0 5 130 5 16 8 0 5
44. TUM CRYOSTATS Part HI dewar and that it does not bent if necessary move slowly and carefully the He dewar to align it with the transfer line Be also sure that the transfer line does not touch the bottom of the He dewar leave it few centimeters above the bottom The He flow in the transfer line will first show a rapid increase due to the sudden overpressure in the He dewar which will be followed by a decrease After 1 2 minutes the He flow through the transfer line will again increase to its maximum value After a few minutes the temperature of the Phase Separator should drop to the nominal value Readjust the He flows For this last point experience shows that the transfer line flow F2 should be maintained for few minutes to a high value and gradually decreased When a sufficient He flow is detectable in the Sample Chamber set the temper ature controller in the Control Mode by pressing the Local button if necessary and pressing the Control button If you want to operate in the High Temperature regime do not forget to switch ON the Tube Heater Do not forget to tightly close the empty He dewar and to connect it to the He recovery line Part HI 6 QUANTUM CRYOSTATS 37 6 2 6 Startup procedure Cryostat warm This section is not intended to a normal uSR Facility user Check vacuum space of cryostat and transfer line Connect transfer line to cryostat Open needle valve V4 completely Close valve V V
45. The P parameters are rounded when displayed by the controller The pa rameters are stored in a PID Table of the Conductus temperature controller The maximum power should be fixed at 40 Cryostat 9505 Loop 1 Break P I D Heater point K Range W 300 30 20 4 50 150 30 20 4 50 100 100 30 10 5 50 100 10 4 5 20 250 10 1 5 15 150 5 2 5 10 50 5 1 5 4 200 6 2 0 5 3 100 10 2 0 5 1 2 8 2 0 5 Table 2 Cryostat 9506 PID parameters for the Loop 1 diffuser of the temperature controller The P parameters are rounded when displayed by the controller The param eters are stored in a PID Table of the Conductus temperature controller The maximum power should be fixed at 27 Cryostat 9506 Loop 1 Break P I D Heater point K Range W 300 10 40 20 50 200 8 40 20 50 150 6 40 20 50 100 30 120 60 5 50 20 24 6 5 20 15 35 16 5 6 18 10 3 0 5 5 5 18 10 3 0 5 3 20 10 3 0 5 1 20 8 2 0 5 Part HI 6 QUANTUM CRYOSTATS 31 Table 3 Cryostat 9512 PID parameters for the Loop 1 diffuser of the temperature controller The P parameters are rounded when displayed by the controller The pa rameters are stored in a PID Table of the Conductus temperature controller maximum power should be fixed at XX Cryostat 9512 Loop 1 Break P I D Heater point K Range W 300 30 30 4 50 7
46. UPPLIES AND SETTINGS 75 E QSESO1 _ OD Figure 29 Schematic of the beam magnets of the 7M3 beamline Magnet names of the form QXXNN represent quadrupoles ASXNN are bending magnets SSKNN are steering magnets and FSNNN are slits The slits FSH31 and FS31 are always fully open The muon rate at the instrument is controlled with the slits FS302 located just in front of the septum magnet ASS31 76 12 BEAM LINE POWER SUPPLIES AND SETTINGS Part V 12 2 Setting the beamline Since 2011 all the power supplies for the beam magnets are now controlled by the system EPICS Experimental Physics and Industrial Control System In addition al most all the power supplies have been replaced and few more will be replaced during the next shutdown All but few power supplies QTH31 QTH32 AND QTH33 are located on the platform above the GPS cabin see Figure 30 All power supplies can be controlled via the Beamline PC PC8290 The Experiment Magnets WED WEDL and WEP can be controlled through the deltat application running on the console PC6012 Both computers run E
47. _B is switched OFF The control is performed by the Valve Controller PFEIFFER RVC300 The ac tual He flow is measured by a flowmeter HASTINGS HS 50KS and is also indicated on the center display located at the top of the rack Setting a flow from deltat In the tab Modify Devices choose the flow controller entry and hit the Modi fy button Enter the new flow value in the pop up window and close it Setting a flow in an autorun sequence A He flow setpoint can also be included in a auto run sequence by using the command SET Flow FLOW XXX command Example SET Flow FLOW 4 3 With this example an He flow setpoint has been set to 4 3 liter gas minute e Manual setpoint only in case of emergency Locate the RVC300 device in the area rack Press the button locate below PARAM Press the edit button to edit the SOLL value Change it with arrow buttons note that 100 mV correspond to 1 1 min Presse the button locate below SAVE e Software setup done by the uSR Facility team The on line database in the backend computer has to be edited In the database directory Equipment flowr300 Settings Devices RVC300 DD the vari ables Scale should be set to 100 Flim to 25 Vlim to 6000 and Offset accordingly The time needed for the actual He flow to reach the setpoint value will depend on the PID parameters of the RVC300 controller When increasing the temperature the He flow should be changed first if necessary The temperature controll
48. ample change The following points describe the process of changing a sample in the cryostat For safety reasons a sample change should only be performed in the High Temperature regime with a sample temperature T gt 30 K Switch OFF the heaters by setting the Conductus or Neocera temperature con troller in the Monitor Mode by pressing the Local button if necessary and pressing the Monitor button Switch OFF the Tube Heater Disconnect the electrical plug from the sample stick Dismount if necessary the rotation motor Stop the He flow through the pumps PUMP1 and PUMP2_A by closing the two valves V2 and V3a on the pumping line of the Sample Chamber do not disconnect the electrical plug of the electrovalve V3b the yellow valve V on the transfer line pump use the closing ring without changing the actual setting of the valve Pressurize slightly the Sample Chamber with He gas by opening the valve V6 until you reach a pressure P2 slightly above 1000 mbar check if the He gas cylinder is open Check carefully and frequently the pressures P and P2 in the Phase Separator and in the Sample Chamber An overpressure in the Sample Chamber could damage the titanium windows Remove the clamp of the Sample Stick Remove the Sample Stick from the cryostat Immediately mount a blind flange on the cryostat opening Stop blowing He gas by closing the valve V6 Restart the He flow through the He pumps by opening
49. ated with respect to its momentum vector The effect of the electric field in the separator spin rotator is to rotate the muon polarization upwards slightly by about 7 so that there is a polarization component transverse to the momentum direction This component will for example create an oscillatory signal in the Up Down and Right detectors when a longitudinal field is applied In this geometry the spin rotator will rotate the muon spin upward by about 50 By increasing the angle the transmission of the spin rotator is dramatically reduced When a transverse field WED is applied the detectors Up Down and Right have a reduced asymmetry corresponding to the projection of the polarization vector on the field frame 13 3 Conditioning and maintenance If the required voltage for the spin rotator separator E field cannot be reached a conditioning of the electrodes is most probably necessary That is slowly increasing the voltage with vacuum conditions until the field breaks down and leaving it at this setting for a period before increasing it further This process is done each year at the start of the beam period or when necessary by the instrument scientist The spin rotator is operated with a constant and controlled gas flow Helium Neon gas at 1 2 x 10 mbar PSI Nr 13 700 0000 The gas bottle has to be changed periodically usually done by a dedicated technician Figure 31 shows the pressure of the gas bottle as a function of the
50. ature gradient say about 6 7 l min After this first run one should be able to obtain the opti mal values of P2 and F2 which are necessary to reach the lowest temperature and also to start a temperature scan e After a He dewar change the flow Fl does not reach the usual values and the pressure PI is lower as usual Be sure that the bottom of the transfer line does not touched the bottom of the He dewar If not the transfer line is probably partially blocked Remove it from the He dewar following the instructions as for changing the He dewar and warm it up again Let a flow of He gas flowing through the transfer line by opening the valve V5 e Upon reaching the lowest temperature in the Low Temperatures regime the temperature controller does not display the sensor 2 holder sensor any more and the controller has jumped to the Monitor Mode This happens sometimes at very low temperatures with Diode sensors Wait few minutes to see if the display comes back to normal If yes switch the temperature controller to the Control Mode by pressing the Local button if necessary and pressing the Control button If not and you are desperate put the controller on a one loop mode with the help of the deltat program Tab Modify Devices buttons Modify and Modify setup 40 6 QUANTUM CRYOSTATS Part HI 6 3 Dimensions e Dimensions e Sample holder dimension 41 6 QUANTUM CRYOSTATS Part III PSI uSR User Facilities Quantum C
51. cera temperature controller both other thermo couples are also connected to PUS Thermocouple Display which provide a linear output signal to feed the Conductus Neocera temperature controller The PID values of the temperature controller are kept to fix values 10 250 and 0 for the parameters P I and D Using the Lakeshore 340 Temperature Controller When the Lakeshore 340 Temperature Controller is used both other thermocouples are directly connected to the controller and not to the PUS Thermocouple Display The thermocouple for the heater is connected as sensor C and the thermocouple of the sample is connected as sensor D For the Lakeshore the PID parameters shown on Table 7 are used Table 7 Zurich Oven PID parameters for the Loop 2 of the temperature controller The parameters are stored in a PID Table of the Lakeshore temperature controller Zurich Oven Loop 2 Break P I D point K 450 15 1 2 3 500 19 1 8 4 700 24124 4 800 30 3 6 4 1200 50 6 5 To heat up the sample the analog output of the temperature controllers is sent to a GOSSEN power supply use exclusively the type 24K32R4 32V 4A Figure 20 indicates the necessary settings to interface both instruments The maximum current for the GOSSEN is therefore limited to about 4 Amp 50 7 ZURICH OVEN Part HI 7 3 Sample change Stop heating by switching either the temperature controller to MONITOR mode if neces
52. d Cooling Flow The second flow circuit is the heat shield cooling Liquid helium from the trans fer line enters the top of the Phase Separator and the gas exiting from the top of the PS is used to cool the sample chamber and the main heat shields EX The cold return gas is then used to cool the transfer line shield The flow is controlled by the valve V1 and the pump PUMPI Part III 6 QUANTUM CRYOSTATS 19 P1 l P2 Pump2_B Pump2_A Pumpi Transfer line 7 Tv N EN y VIN RNS a ka C i S zar SS E vX B Xe He EX V3a V3b F2 S dewar PS oo V4 S U fi He a U He He He gas recovery Sample He gas recovery recovery supply chamber supply Diffuser Figure 8 Schematic diagram of the Quantum cryostat P pressure F flow V valve EX heat exchanger PS phase separator 20 6 QUANTUM CRYOSTATS Part HI 6 2 2 Principle of control action Phase Separator Sample Chamber For all desired sample temperatures the temperature of the Phase Separator Tps should be kept constant Utilizing the available DT 470 Lake Shore Diode and taking into account the pressure drop through the heat exchangers and the uncertainties of the sensors one should maintain the following temperatures Cryostat Tps Quantum 9505 4 6K Quantum 9506 4 3K Quantum 9512 4 1K
53. d now put by himself the entrance gate in the red state If not tell him to close the area sperren Locate the grey box controlling the beam blocker on the left hand side of the door Wait until the PSA led is ON 1 minute and press the button AUF to open the beam blocker After some seconds 30 s the green led AUF will indicate that the beam blocker is open 2 3 Freeing the area from Red to Green To allow a free access to the area the user will have to perform some simple operations Close the beam blocker by pushing the button ZU on the grey box located on the left hand side of the door Kanalverscluss KSE301 Wait until the red led ZU in ON Part I 2 THE BEAM AREA 1M3 2 9 e Call the Control Room via the black CALL button CCTV camera and light should come ON e Tell the operator to free the access Zugang frei e The state of the entrance gate should change to the Green state The access is now free IL The instrument General description The detectors The GPS Instrument is permanently installed in area TM3 2 using a so called surface muon beam i e positive muons originating from the decay of positive pions stopped near the surface of the production target M The typical range of these muons is about 1 5mm in polyethylene or 0 65 mm in aluminum see also Section 17 page 86 The TM3 beamline is equipped with an electromagnetic separator spin rotator al
54. dea is to extract only one muon at a time out of a continuous beam by means of a fast switching electrostatic deflector kicker on request from a USR instrument This makes sure that no other muon reaches the spectrometer until the extracted one has been processed Moreover the concept of Muons On REquest MORE does not significantly reduce the intensity of the original beam which is there fore available for the simultaneous use by a second spectrometer i e MORE produces twice as many results of even higher quality lower background in one spectrometer than the conventional technique 14 2 Experimental Setup in the 7M3 Area The main components Kicker Septum magnet installed for MORE in the surface muon beam line piM3 are shown in the Figure 29 see also Ref 3 The kicker contains two 1m long 20cm wide electrodes 20cm apart Two power sup plies for de voltages up to 5kV and 5kV are connected to the electrodes via fast switches giving a difference of 20kV between the two field directions and a separation of the muon trajectories of about 5cm at the intermediate beam focus in front of the septum magnet located about 5m from the kicker exit Each switch consists of a series of 15 high voltage MOSFET transistors type IXYS 6N100 The muon detector M counter in the spectrometer GPS or LTF is used to trigger the kicker The kicker is switched to the spectrometer running in MORE mode say GPS for a maximum of 5ys at a fixed re
55. defined for a particular setup Note that for all the modules developped at PSI a RS485 connection is avail able It allows to setup the module with the MSCB MIDAS Slow Control Bus protocol through a MSCB submaster connecting the RS485 bus to the ethernet Those settings are saved on flash memory on the boards Changing the logic As said the logic conditions as for example switching ON and OFF the Veto 5 1 2 Slow Control 5 2 Other computers 5 3 Laptop connections 5 4 Printing counter can be changed by software This is done through the GUI application deltat for more information see the Manuals MuSR Graphical User Interface deltat and TDC Elctronics Manual The slow control devices are mainly controlled via GPIB IEEE 488 bus RS 232 serial line directly through Ethernet TCPIP or through the Midas Slow Control Bus MSCB e GPIB Controlled through an Agilent LAN GPIB Gateways E5810A e RS 232 Controlled either through a Lantronix ETS8PS 8 channel RS232 termi nal server Some Linux workstations are available They can be used with the user s AFS account or with the local account account _musr_tst and password DeltatDeltat As described in Section 12 2 the secondary beamline control system controlling all beamline elements magnets slit systems separator etc between the target station and the experiment is now based on the EPICS architecture A client PC is dedicated to control the beamline hipa
56. eased hear the characteristic click Each person going in the area should unlock a black key Put one black key in the door lock and turn it clockwise When the buzzer is heard push the door handle very gently down and open the door Enter and close the door Check in the right order the 4 locations buttons indicated on the Figure 1 The locations are also reported on a figure displayed at the door of the area The location to clear is indicated by a lighted green button which has to be pressed At this point you are responsible that nobody is staying in the area When finished go back to the door Push the CALL button on the door CCTV camera and light should come ON When you hear the buzzer put your black key in the door lock and turn it coun terclockwise or press the little black button near the lock and gently push down the door handle Come out close the door and put back the black keys in their slots The operator should now put by himself the entrance gate in the red state If not tell him to close the area sperren Locate the grey box controlling the beam blocker on the left hand side of the door Kanalverschluss KSE301 Wait until the PSA led is ON 1 minute and press the button AUF to open the beam blocker After some seconds 30 s the green led AUF will indicate that the beam blocker is open 2 THE BEAM AREA 1M3 2 Part I RGS Buttons
57. er setpoint should be changed in a second step The opposite should be done when decreasing the temperature If a large change of flow is required big temperature overshoots can be observed To minimize the overshoots the He flow setpoint should be changed in different steps prior to change the temperature controller setpoint Depending on the setting of the needle valve V4 between the Phase Separator and the Sample Space it is possible that a desired He flow cannot be reached eventhough the RVC300 controller will fully open the Electromagnetic Valve V3b To fix this problem one should more open the needle valve 46 6 QUANTUM CRYOSTATS Part HI 6 4 3 Sample rotation A step motor and its controller EL734 can be utilized to rotate the sample The motor unit can be mounted on the cryostat on the available holders 3 The motor shaft has to be connected to the sample stick using the available screws 2 The motor control unit EL734 switches automatically to local mode as soon as a local operation is performed To rotate manually the sample e Be sure that the and buttons are lit otherwise wait few seconds Press the green round button corresponding to the motor 1 The green LED of the button should now be ON Press and hold the or yellow button to rotate the sample in one or the other direction If during this operation the green square button suddenly lit it means that
58. ffuser Temperature K Time Figure 10 Comparison of the temperatures measured at the diffuser with the ones measured at the sample holder and at the sample position Fork Note the gradi ent and the perfect agreement between the sample holder temperature and the Fork temperature Sample Holder Fork Diffuser Temperature K Time Figure 11 Same configuration as in Fig 10 for higher temperatures Note that the gradient is now opposite 24 6 QUANTUM CRYOSTATS Part HI High Temperatures In this regime the manual valve V2 is kept closed and the electromagnetic valve V3b controls the mass flow through the pump PUMP2_A make sure that the PUMP2_B is switched OFF and that the valve V3a is fully open A heater current should be sent and kept at all times into the Tube Heater Cryostat Tube Heater Current Quantum 9505 230 mA Quantum 9506 230 mA Quantum 9512 200 mA The needle valve V4 should be about 0 5 mm open 50 units If large temperature oscillations are observed at low temperatures especially around 15 20 K the needle valve V4 should be further slightly closed The desired temperature is obtained by choosing the He flow F2 according to the Figures 12 Cryostat 9505 13 Cryostat 9506 or 14 Cryostat 9512 and by sending the required setpoints to the temperature controller If the flows nec essary to reach the lowest temperatures in this
59. hamber Evacuate the sample chamber by putting the MOGLI on unlock Pump con tinuously the sample chamber during the full operation in High Temperature Regime The temperature control is performed by 2 GaAlAs diodes LakeShore TG 120 SD controlling two independent heater loops The first diode is located on the sample chamber tube the second one is located on the sample stick The temperature controller is normally a LakeShore 340 During operation in the High Temperature Regime the setpoint of the loop of the sample chamber should be kept at 280K and the sample stick setpoint can be changed as desired e The temperature of the Sample Chamber tube 7 5 or Theater 18 measured on the channel loop 1 e The temperature of the Sample Holder Thotder Or Tanalog 18 measured on the channel 2 loop 2 The voltage loop 2 of the LakeShore controls an ex ternal Gossen power supply use exclusively the type 24K32R4 32V 4A Figure 25 indicates the necessary settings to interface both instruments The maximum current for the Gossen is therefore limited to about XXX Amp e Do not forget to switch ON the heaters by pressing the corresponding but ton on the HECTOR unit in case that a LS340 temperature controller is Part HI 8 TOP LOADING JANIS 4 K CLOSED CYCLE CRYOSTAT 59 used This last point can be performed directly from the Console running the application deltat On the application deltat the LakeShore 340 is c
60. he temperature controller via the Console see Section 6 4 1 You can also switch the temperature controller on Control Mode from the Console e If you want to operate in the High Temperature regime do not forget to switch ON the Tube Heater Part HI 6 QUANTUM CRYOSTATS 35 6 2 5 He Dewar change Should the He Dewar levelmeter read below 15 in the case of a 100 liters de war or below 100 mm in the case of a 250 liters dewar the He Dewar needs to be changed For safety reasons a He dewar change should only be performed in the High Temperature regime with a sample temperature 7 gt 30 K Stop the He flow through the pumps PUMP and PUMP2_A by closing the two valves V2 and V3a on the pumping line of the Sample Chamber do not disconnect the electrical plug of the electrovalve V3b the yellow valve VI on the transfer line pump use the closing ring Switch OFF the heaters by setting the Conductus or Neocera temperature con troller in the Monitor Mode by pressing the Local button if necessary and pressing the Monitor button Switch OFF the Tube Heater Lift up slightly 50 cm the transfer line on the He dewar side the bottom part of the transfer line in the He dewar should now be above the liquid He level Pressurize slightly the Phase Separator with He gas by opening the valve V5 until you reach a pressure PI of about 1000 mbar check that the He gas cylinder is open Check carefull
61. he pumping unit MOGLI press the unlock button Be sure that the 3 ways valve 3 2 valve is open Reconnect the cable B to the electrical feedthrough of the sample cham ber Enable the heater by pressing the corresponding button on the HECTOR unit located near the LakeShore 340 temperature controller Set new setpoints from the computer 60 8 TOP LOADING JANIS 4 K CLOSED CYCLE CRYOSTAT Part HI The Tables 10 and 11 indicate the value of the PID parameters used by the temperature controller for the two loops Table 10 Cryostat Janis 4 K CCR PID parameters for the Loop sample chamber tube of the LakeShore 340 temperature controller The parameters are stored in a PID Table in the BackEnd computer and dowloaded on the LakeShore temperature controller when necessary Cryostat Janis 4 K CCR Loop 1 Break P I D Heater point K Range W 130 5 16 8 100 60 12 50 15 100 30 30 30 0 10 8 30 30 0 1 Table 11 Cryostat Janis 4 K CCR PID parameters for the Loop 2 sample stick of the LakeShore 340 temperature controller The parameters are stored in a PID Table in the BackEnd computer and dowloaded on the LakeShore temperature controller when necessary Cryostat Janis 4 K CCR Loop 1 Break P I D point K 450 90 7 3 Part HI 8 TOP LOADING JANIS 4 K CLOSED CYCLE CRYOSTAT 61 MN P BH ST UV W XY Z PTT eet Td ed
62. hit the front surface of the sample at about 0 3c 4 MeV and are then slowed by interactions within the material before stopping The implantation energy of the muons results in them passing through several hundred microns of ma terial before they come to rest Prior to hit the sample the muons will go through different material e 2 mylar windows 2x4 um e the M detector scintillator material 0 2 mm e 2 layers of superinsulation aluminized mylar 2 x 10 um e the cryostat titanium window 10 um When entering the sample the actual amount of material traversed by the muon and the width of the muon distribution depend upon the materials density as a rough guide the muon range is roughly 130 mg cm compare to the 180 mg cm just after the production target of material i e about 1 3 mm of water 0 6 mm of silicon etc Figure 38 shows the fraction of stopped muons in aluminum foils of different thick ness The experiment was performed by piling up foils on a thick quartz plate and comparing the diamagnetic and muonium fraction of the uSR signal The experiment was performed directly inside of the Quantum cryostat All muons are stopped for an aluminum thickness of about 0 6 mm 18 Effect of the field on the parameter In longitudinal configuration the asymmetry is sometimes extracted from the direct difference between the Forward and Backward detectors To take into account the different design and quality of the detectors a pa
63. ic port used Each of the sub detector is read on both side by an array 4 or 5 SiPMs photo sensors e A Backward veto detector Bio This detector consists of a hollow scintil lator pyramid B4 B BY and B2 with a 7x7 mm hole facing the M counter The purpose of the Byer is to collimate the muon beam to a 7x7 mm spot and to reject muons and their decay positrons missing the aperture active collimation e A forward veto detector Para rejecting muons which have not stopped in the sample and their decay positrons It is used with small samples When the sample holder assembly stops all muons Fyero itis usually added to the F detector to increase the forward solid angle Right Right pias Saas Down Mobile WA Sample Forward Veto Muon Backward Veto Counter HE Left Left Figure 3 Schematic top view of the detectors Not shown are the BY B2 and the Up detectors 4 THE DETECTORS Part II Figure 4 View of the detectors set located up stream from the sample The Beto pyramid is clearly visible as well as the Backward Muon detectors Portions of the Left and Right detectors are also visible Figure 5 View of the detectors set located down stream from the sample The U D R portion L portion and F detectors are visible The Mobile detector is here in the Left position The pyramid is the F detector which can be added or not to the F definition
64. is located on the side of the cold head Sumitomo Heavy Industries with a direct access from the top of the cryostat allowing therefore rapid top loading changes of sample see Figure 22 Cooling is provided by a good thermal link be tween the second stage of the cold head and the bottom part of the tube of the sample chamber An aluminum radiation shield surrounds the sample tube and is cooled by the refrig erator first stage heat station Cold Thermal Head Link Connection to 3 L 2nd port vacuum Wy Samples Sik n phs pr Sl EA ne access Er SS TAGS ST Se si HIS TSG DS Sample Chamber Sample Chamber tube tube copper part stainless steel part Connection to external vacuum pump Figure 22 Schematics of the Janis 4 K CCR In the Low Temperature Regime i e up to 300 K the sample chamber must contain helium gas to ensure a good thermal contact with the sample Within this temperature mode the temperature of the sample is controlled through two heating loops one for the sample chamber tube and one for the sample stick Both loops should have the same setpoint On the other side during high temperature measurements i e from 300 to 475 K the sample chamber is permanently pumped and thermal contact kept at a minimum between the stick and the sample chamber tube The cold head is also active in this mode and the sample chamber tube must be
65. lowing to rotate the muon spin direction with respect to the muon momentum o T N Figure 2 3D view of the instrument without sample insert The muon beam enters the instrument from the right hand side The instrument is designed for zero ZF longitudinal LF and transverse field TF USR experiments in wide ranges of temperature see Part III page 17 and external magnetic field see Part IV page 70 A special detector arrangement allows to inves tigate very small samples Sample rotation is provided for the study of orientation dependent effects in single crystals The GPS Instrument can be used simultaneously with the Low Temperature Facility LTF Instrument either by splitting the beam continuously by widening the spot in front of the collimators located at the entrance to the septum magnet see Figure 29 page 75 or by triggering an electrostatic deflector kicker on request of one of the Instruments Muons On REquest MORE see also Section 14 page 80 The detector arrangement consists of e A muon detector M having a thickness of 0 18 mm Part II 4 THE DETECTORS 11 Six positron detectors with respect to the beam direction Forward F Back ward B Up U Down D Right R and Left L Some of these detectors i e U D R and L are actually composed by two different subdetectors A so called Mobile detector which is either added to the R or to the L detector depending on the cryogen
66. maintained at 280 K with the first heater loop The sample stick acts as a hot finger and its temperature is varied with the second heater loop The 4 K CCR sample holder is similar to the one used for the Quantum cryostat see Figure 17 Part HI 8 TOP LOADING JANIS 4 K CLOSED CYCLE CRYOSTAT 55 8 2 Principle of operation 8 2 1 Low temperature regime LTR s said this regime extend between 4 K and 300 K In this regime the sample chamber must contain helium gas to ensure a good thermal contact with the sample Preparation The 2nd port should be put in position by translating the Quantum cryostat on the Ist port to the position 119 5 mm Interconnecting helium supply and return gas lines should be installed between the cold head and compressor Tighten each fitting securely with the appropriate sized wrench Be sure that supply and return lines do not become crossed during installation Plug the cold head s control power cord into the jack located on the SHI compressor back panel on one side and on the cold head on the other side Connect the thermometry cables from the electronic rack to the cryostat electrical feedthroughs A for the cryostat and B for sample stick if already inserted The vacuum chamber around the 4 K CCR is connected to the 2nd port cham ber of the GPS instrument and therefore separated from the main vacuum of the spectrometer Prior to cooldown connect the MOGLI pumping uni
67. nd flange and insert the sample stick Stop blowing He gas by closing the valve V He A Decrease the pressure in the sample chamber down to 200 mbar by pump ing with the MOGLI pumping unit Isolate the sample chamber by closing the 3 ways valve 3 2 valve on the sample chamber Reconnect the cable B to the electrical feedthrough of the sample cham ber Enable the heater by pressing the corresponding button on the HECTOR unit located near the LakeShore 340 temperature controller Set new setpoints from the computer 58 8 TOP LOADING JANIS 4 K CLOSED CYCLE CRYOSTAT Part HI 8 2 2 High temperature regime HTR This regime extend between 300 K and 475 K In this regime the sample chamber must be continuously evacuate and the sample stick acts as a hot finger Preparation Sample mounting Temperature control in HTR The 2nd port should be put in position by translating the Quantum cryostat on the Ist port to the position 119 5 mm Interconnecting helium supply and return gas lines should be installed between the cold head and compressor Tighten each fitting securely with the appropriate sized wrench Be sure that supply and return lines do not become crossed during installation Plug the cold head s control power cord into the jack located on the SHI compressor back panel on one side and on the cold head on the other side Connect the thermometry cables from the electronic rack to the cry
68. nit Press PST ON F1 to start MOGLI Rezipient Yl Oa gt HV HP FVHP BV X O GP Xw s VP Figure 45 Vacuum diagram of a MOGLI unit While MOGLI is running observe the dual gauge for the actual pressure the Turbo Control Unit TCU for turbo indicators and the FPS display for messages from the controller see Table 16 94 21 MOGLI QUICK REFERENCES Part VIII 21 3 Errors To change the turbo pump to standby mode use the TCU front panel Prior to change recipients or open extern valves while MOGLI is running you must first press the button LOCK HV on the FPS Unit Never use the manual flood valves FV FVHP or the manual switches of pneu matic valves VV BV HV without well instructed staff and reading carefully the documentations of MOGLI Table 16 Meaning of the FPS indicator LEDs IN green LED OUT red LED 101 HP ok 002 HP on 102 HP 80 003 VP on 103 VP run 006 open VV 104 VV open 007 open BV 105 VV closed 009 open HV 106 BV open O11 GP lt 0 Imbar 107 BV closed O12 GH lt Imbar 110 HV open 111 HV closed 114 VP at speed You can find the full version of how to fix an error in the complete documentation The FPS shows errors on the display as scrolling text messages FPS shows wrong display text Solution load FPS program Mogli_v2 fps from a computer to FPS VP ERROR VP is not at speed after 30 seconds
69. number of operation days Part V 13 THE SPIN ROTATOR 79 Pressure bar 120 100 80 60 40 20 Separator nM3 Gas Pressure 50 100 150 200 Days Figure 31 Change of bottle gas pressure as a function of time 80 14 MUONS ON REQUEST MORE Part V 14 Muons on request MORE 14 1 Introduction In conventional time differential uSR experiments an ideal lifetime spectrum would contain only start stop events belonging to the same muon In real experiments using continuous muon beams however there is always a certain number of muons escaping detection e g those stopping near but not hitting the muon counter This results in a random rate of events in the start and stop channels and a random background in the muon decay histograms thus limiting the useful time interval to about 10 us and excluding investigations of low muon spin precession frequencies or slow relaxation processes Pulsed muon beams on the other hand deliver many muons per pulse at low repetition rates e g 50Hz at ISIS In this technique the time resolution is limited by the finite length of the muon pulses 80ns at ISIS compared to Ins on the GPS instrument at PSI However the background is typically three orders of magnitude lower A method to solve the background problem at continuous muon beams has been pro posed earlier see 1 2 for surface muon beams at TRIUMF or KAON but has never been realized The basic i
70. ontrolled by the front end Temperature_2nd_port This front end should run and configured to operate with the high temperature PID tables Sample change in HTR The sample change must be performed with the compressor cold head running Set the sample stick setpoint to 300 K and wait until the sample stick tem perature is below about 320 K Stop the heater by pressing the corresponding button on the HECTOR unit located near the LakeShore 340 temperature controller Disconnect the cable B from the electrical feedthrough of the sample chamber Stop pumping in the Sample Chamber by isolating the MOGLI pumping unit press the lock button Pressurize the sample chamber by opening the V He A valve be sure that the 3 ways valve 3 2 valve is open Gas should blow through the overpressure valve located on the sample chamber Remove the sample stick and immediately connect the blind flange at the end of the sample chamber Isolate the sample chamber by closing the 3 ways valve 3 2 valve on the sample chamber Change your sample When ready pressurize again the sample chamber with He gas by opening the 3 ways valve 3 2 valve on the sample chamber and the V He A valve Gas should blow through the overpressure valve located on the sam ple chamber Dismount the blind flange and insert the sample stick Stop blow He gas by closing the valve V He A Start pumping in the sample chamber with t
71. oose the appropriate MODE for the acquisition software In the deltat programme chosse the tab TDC Settings and the button Modify Settings 3 Be sure that the MORE electronics is set to send the muon on request to GPS see also Figure 32 4 Start your measurements Part V 15 VACUUM 83 15 Vacuum The beamline vacuum is controlled by different pumps named PS32 PS33 spin rotator PS34 and PS321 GPS Instrument Other pumps are located on the LTF branch Different valves are also located along the beamline VSD31 between pro ton beam and TM3 beamline VSD32 and VSD33 up and down stream of the spin rotator and VSD321 up stream of the GPS instrument In addition two mylar win dows 4 um are located at the beginning of the beamline and just in front of the GPS instrument The different pumps and valves are controlled from the vacuum panel located near the entrance to the 7M3 2 GPS area During normal operation all the valves should be open and all turbo molecular pumps should be ON Interlocks prevent the opening of or will close the valves in case of too large pressure difference Since 2011 the whole vacuum equipment of the beamline is operated from the new vacuum control panel located near the entrance of the GPS and LTF area Caution should be taken when operating this touch panel as pumps and valves will close without additional warning Figure 34 Location of the vacuum touch panel located near the
72. ostat electrical feedthroughs A for the cryostat and B for sample stick if already inserted The vacuum chamber around the 4 K CCR is connected to the 2nd port cham ber of the GPS instrument and therefore separated from the main vacuum of the spectrometer Prior to cooldown connect the MOGLI pumping unit and evacuate the second port vacuum chamber to a pressure of 107 mbar or less Better vacuum levels provide greater insulation resulting in shorter cooldown times and lower final temperatures After evacuation is complete you can start the compressor After that the cold head starts to cooldown seal the vacuum valve V 2nd firmly see Figure 23 Outgassing and O ring permeation will cause the pressure to rise slowly over time therefore periodic re evacuation will be necessary Remove the 4 K CCR blind flange at the end of the sample chamber insert the sample stick in position and fix it using the appropriate clamp Since within the HTR mode the sample is warmed by the sample stick heater special care in thermally anchoring the sample to the holder is needed Be sure to correctly position the sample stick horizontally and check the longitudinal position see Figure 24 The MOGLI pumping unit can now be connected to the sample chamber valve V 2nd closed MOGLI on lock position pumping pipes connected to the Sample Chamber see Figure 23 and open the 3 ways valve 3 2 valve of the sample c
73. our experi ment Sample mounting is NOT allowed in the Counting Room All sample mounting will have to be performed either in the beam area or in the Sample Preparation Laboratory located also in the Neutron Hall Moreover it is forbidden to handle radioactive material samples in the Sample Preparation Laboratory The transport of radioactive material is subject to authorization A number of national and international regulations must be fulfilled concerning e g labeling packing type of shipping and shipping documents Depending on the type and activity of the ra dioactive material special transport or shipping may have to be organized On the PSI site all transports of radioactive material outside a controlled zone e g outside the Experimental Hall have to be declared in advance to the Safety Officer of the Radiation Protection Group The name and telephone number of the member on duty can be found on a yellow panel at the entrance door to the GPS area Handling of radioactive material is not allowed outside a controlled zone or inside any Counting Room Moreover it is also forbidden to handle radioactive mate rial samples in the Sample Preparation Laboratory All information type of material packing and any operation performed on radioac tive material time of entry to the experimental area handling measurements time of 1 REGULATIONS Part I 1 5 2 Preparation 1 5 3 Unexpected Events 1 5 4 Removal from PSI 1 6
74. petition rate max 40kHz usually 37 kHz The signal of the first muon hitting the trigger detector M counter after a minimum delay of 200ns is used to switch the kicker back to the spectrometer running in par asitic mode LTF in this case The delay is necessary to avoid damage to the power switches Either instrument GPS or LTF can be used in MORE mode while the other one is running in parasitic mode Part V 14 MUONS ON REQUEST MORE 81 515 22 us Pulser O Je 8020 DT104 a 200 ns DT104 2 i _ End Mark 7 NIM DT10 TTL Kicker Electronic GPS or LTF signal ia oe ee AA Latch Mode Figure 32 Schematic of the switching logic for the beamline kicker The instrument to which the muon on request will be send is defined by i the setting of the logical AND coincidence i e GPS AND and LTF OFF for GPS and the opposite for LTF ii by changing the mode of the NIM TTL converter either NORMAL or COM PLEMENTARY 14 3 Advantages but Figure 33 shows an example of uSR in silver in an external magnetic field of 10mT taken with the GPS in MORE mode For comparison a conventional spectrum is shown taken at the same event rate The background in MORE mode is at least a factor of 100 lower than in conventional mode thus allowing the
75. pot size will only marginally depend on the opening of the slits FS302 which will therefore only act as a regulation of the event rate The beam spot size has been measured without cryostat but with all detectors in posi tion with the help of a detector width 2 mm Horizontal and vertical scans have been performed The results have been deconvolutated to take account of the finite width of the detector 10000 m r r r r Muon beam profile 8000 e o GPS sample position 2 mm detector O 6000 e FWHM 5 8 mm 2 F taking into account 2 the detector width O 4000 t S 2000 5 1 gt o o o 10 8 6 4 2 0 2 4 6 8 10 12 14 Vertical Position mm Figure 36 Raw data from a vertical scan of the beam spot at the sample position After deconvolution the FWHM is estimated to be 5 8 mm 86 18 EFFECT OF THE FIELD ON THE o PARAMETER Part VI 3000 1 r r rr r r sana Muon beam profile t o GPS sample position L 2 mm detector 2000 L L FWHM 5 3 mm 2 L taking into account 3 1500 the detector width O F 6 1000 L L k e 500 0 1 9 o 1 f fi L fi fi 1 i O 1 fi fi f 1 10 8 6 4 2 0 2 4 6 8 10 12 14 Horizontal Position mm Figure 37 Raw data from a horizontal scan of the beam spot at the sample position After deconvolution the FWHM is estimated to be 5 3 mm 17 Range The muons in the beam
76. rameter o is utilized ideally amp 1 This parameter is obtained by performing a measurements in a weak transverse field usually the WEP magnet see Section 19 When a longitudinal field is applied the interaction of the magnetic field with the incoming muons and the decay positrons creates a change of the parameter 0 Figures 39 and 40 show the deduced asymmetry in longitudinal field by assuming a amp parameter Part VI 18 EFFECT OF THE FIELD ON THE PARAMETER 87 Fraction of stopped muons 0 100 200 300 400 500 600 700 Aluminium thickness um Figure 38 Fraction of stopped muons as a function of aluminum thickness constant Both a small silver sample and a silver plate were measure in Veto and Non Veto mode respectively This asymmetry change is an artifact that reflects the change of the parameter 0 Hence measurements performed in transverse polarization prove that the asymmetry is constant up to 6 kG pointing therefore to a change of to explain the reduction observed for example on Fig 39 Experimental data can be corrected for this effect however the precise form of the curve depends on the initial value of a and on the tunning used during the experiment The users are therefore advised to perform their own calibration and not rely on the curves of Figures 41 and 42 which show the relative change of assuming constant asymmetry in field Note also that the use or not of the Forward Veto coun
77. ration so ee G REE RS ak s 18 Gall Peppers s re ed eRe ee eee amp dd 18 6 2 2 Principle ot controlaction lt x se e R beh bak eS 20 6 2 3 Configuration in the TMB area 29 A A ee Ree Sele amp BAG 33 625 He Dewarchanse oo 5 be 85 5 pe eee Ree ws 35 6 2 6 Startup procedure Cryostat warm 37 627 Shutdown procedure lt lt ens ane ee Bee Ee BAG 38 62 8 Trouble shooting lt o soceri sek ke se ee 0 39 63 DIMENSIONS vgs akse ced teehee eead a eh be 40 6 4 Additional Information 44 6 4 1 Temperature Controller o oao 44 642 He floWw contol s sosa me 52 2b be a ER R 45 643 Sample rotation io 6 6 ae dG Bae a e ote amp BE 46 6 44 Miscellaneous 47 7 Z rich Oven 48 EL ze se o esc sa hd See GG ee Le eee s 48 72 Temperature contiol s cosac eR ES eR 48 Vo Sampl chang e ee a ee ERAS we Eee ew 50 7 4 Setup made by the Instrument Scientist if a LTC Controller is used 52 7 5 Setup made by the Instrument Scientist if a LakeShore 340 Controller TD A RR EE a lee a eS eae ALS Ge eS 53 8 Top Loading Janis 4 K Closed Cycle Cryostat 54 81 Inttod ction s sk v s bak Ge a e ee R 54 Bo POG OF Operation sa sa e Als st see ak seede BAS 55 8 2 1 Low temperature regime LTR 55 8 2 2 High temperature regime HTR 58 8 3 Setup made by the Instrument Scientist
78. regime cannot be reached the needle valve V4 should be slightly more opened Since the sample holder is solely cooled down by the incoming He gas which is stabilized at the temperature of the Diffuser the time constant neces sary to reach a given setpoint by cooling can be extremely long for an example see Figure 15 It is therefore strongly recommended to perform the required temperature scans by increasing the temperature If long series of runs are required below 10 K it is strongly recommended to switch to the Low Temperatures regime see previous pages in order to save He liquid Part III 6 QUANTUM CRYOSTATS 25 Cryostat 9505 Helium through the Sample Chamber High Temperature Regime 20 18 16 14 o N He Flow l min 00 O 50 100 150 200 250 300 350 5 10 15 20 25 30 35 40 Temperature K Figure 12 Temperature dependence of the He flow through the Sample Chamber flow F2 in the High Temperature regime i e for 5 K lt Taiffuser lt 300 K This flow should be controlled by the valve V3b If the recommended low values of flow are not applied at high temperatures a temperature gradient is usually observed in the sample chamber 26 6 QUANTUM CRYOSTATS Part II Cryostat 9506 He flow through the Sample Chamber High Temperature regime
79. rol the temperature of the different parts of the oven e at the heater position e at the sample holder e on the thermal shield The temperature stability loop is based on the thermocouple at the level of the ther mocoax heater The sample temperature is provided by the additional thermocouple Part HI 7 ZURICH OVEN 49 MN PRS TUVWX YZ PTT ee TT de gt e o e710 o e jm jI e ja s x rm R RI R Pl Figure 20 Diagram of the back connector of the Gossen power supply Ur represents the voltage provided by the temperature controller max 10 Volts KR is fixed at 1000 Ohms and Rp at 60 Ohms The current furnished will be given by Ur x Rp X Irs 0 6 x Rrr where Irs represents the current full scale of the Gossen power supply see Gossen manual placed on the back of the sample holder The third thermocouple measures the temper ature of the water cooled shields Since spare parts are rather difficult to obtain users should carefully handle these thermocouples Please discuss with the Facility team about an appropriate mounting procedure The thermal shield thermocouple is always connected to the PUS Thermocouple Display Using the LTC Conductus Neocera temperature controller When using the LTC Conductus Neo
80. ryostat 9506 and 9512x in GPS Cryostat Chamber Sample Region Horizontal Cross Section Scale 11 1180 1182 to DN 40 Flange of Sample Chamber Port Sample Stick Sensor X Donath 30 Apr 1997 Sample Stick Heater 48 46 5x Sample Holder 30 EE RE Diffuser Heater Diffuser Sensor ES I Sample Chamber 7 A Radiation Shiel GPS Cryostat Chamber EE GE 2 Vi Z L Vt ES Li I IS 29 in amp out 10 um Titanium 2 Layers of 64 pm Aluminized di Polyester Superinsulation gt Beam Figure 16 Drawing of the internal part of the Quantum cryostat inside the GPS chamber 6 QUANTUM CRYOSTATS Part HI 42 _e ZO OL YSIN JepjoH ajdwes IN Hela younp 1219813 sis anony Mysu Jauayos Ned EF ulawabyye ajeso y eddn ibneg LC ogue Y 00 S0 S esse yyeuog x 007 60 60 praon omnes a ES Jeddo9 OHAO Figure 17 Drawing of the coomonly used sample holder Part HI 6 QUANTUM CRYOSTATS 43 e Material in beam path
81. s choose the temperature controller entry and hit the buttons Modify and on the pop up window Modify Temperature On the pop up window change for both loops the setpoints and hit the button Apply Changes Autorun sequences Before writing an autorun sequence be sure that the Conductus in the desired mode one or two loop mode In the autorun file do not forget to give all 6 arguments in the two loop mode only 3 for the one loop mode To change the temperature you will need an entry like SET Temperature 100 0 1 0 30 100 0 1 5 30 WAIT Temperature INRANGE In this example the setpoints are 100 0 K for both loops the tolerances 1 0 K for the first loop and 1 5 K for the second loop and the waiting times are 30 seconds See also page 22 for a discussion about the Low Temperature setpoints Software setup done by the SR Facility team The on line database in the backend computer has to be edited In the database directory Equipment templtc Settings Devices LTC21out DD the variable Serial Number should be set accordingly In the directory userdisk0 musr exp td_musr dat ltc of the Backend computer a file 1tc_NNNN tab should exist where NNNN is the serial number of the controller Part HI 6 QUANTUM CRYOSTATS 45 6 4 2 He flow control The He flow trough the Sample Space can only be controlled when solely the Electromagnetic Valve V3b PFEIFFER EVR116 is used the big bypass valve V2 is shut and the PUMP2
82. sary commands to the PC server controlling the beamline Note that when a specific device has been chosen the software will automatically switch ON the requested device and switch OFF the two others Similarly when a field 0 is chosen for one power supply the three power supplies will be switched OFF For Zero Field measurements the action to set one device to zero will automatically switch off all the devices This is particularly useful in the autorun mode when a combination of Zero and Longitudinal Field measurements is requested In an autorun sequence file the field can be changed as shown in the following exam ple Set Magnet WED 1000 30 In this example a field of 1000 G will be applied by the WED power supply and a stabilization time of 30 seconds is requested The device WED can be replaced by WEDL or WEP Note that the power supply settings and readback values are also displayed on the beamline PC located in the Counting Room After setting a field from the Workstation a star x will appear on the beamline PC in front of the setting of the concerned power supply This is normal and indicates that another client the deltat software in this case has changed the setting Do not try to set the power supplies WED WEDL and WEP from the beamline PC The Tables 14 give the relation between the field values and the DAC values of the different power supplies These tables are already integrated in the DELTAT
83. sary depress first the LOCAL button in case that a LTC Controller is used or by switching the corresponding button on the HECTOR unit in case that a LS340 is used Wait until the temperature is below 320 K Be patient This can take a very long time hours Stop pumping by swiching OFF the MOGLI pumping unit This is performed by pressing the button LOCK HV on the MOGLI Controller Remove the screws connecting the oven to the vacuum chamber Slowly open the valve V He to admit He gas into the chamber Check carefully and frequently the pressure in the chamber do not go beyond 1000mbar Close valve V He Open the oven Stop the water flow by closing both valves IN and OUT Change your sample Carefully remount the thermocouple Open the water flow by opening both valves IN and OUT Insert the oven and connect it to the vacuum chamber with the available screws Start pumping by pressing the button UNLOCK HV on the MOGLI Controller Note that the HV valve will only be open when pre defined conditions will be fullfilled Check again that the water is flowing and switch ON the temperature controller by pressing the button CONTROL if necessary depress first the LOCAL but ton in case that a LTC Controller is used or by switching the corresponding button on the HECTOR unit in case that a LS340 is used This last point can be performed directly from the Console running the pro gramme deltat Part HI
84. shed will be given by Up x Rp x Irs 0 6 x Rrr where Irs represents the current full scale of the Gossen power supply see Gossen manual 48 7 ZURICH OVEN Part HI 7 Z rich Oven 7 1 Introduction 7 2 Temperature control Although the Ziirich oven can now be used on some Facility spectrometers it is not a Facility instrument Therefore the users should be aware that only a limited support will be available from the Facility team The oven can be operated between room temperature and 1200 K The sample holder is connected to a warm finger and the oven is operated in vacuum Therefore the users should take care to obtain a good thermal contact between the sample and the holder An appropriate method should be used to attach the sample to the holder do not use glue The oven is usually installed on the 2nd cryogeny port of the GPS instrument As opposed to the situation in the Quantum cryostat the vacuum chamber around the oven is separated from the main vacuum of the spectrometer Figure 19 shows the pump connections to the oven Therefore independent pumps are necessary to evacuate this chamber usually a stan dard MOGLI pumping unit Second Port Chamber V He Erom Helium K Gr Gauge EV MOGLI Pump Unit K 4 7 GH gt lt HV wl JX FVHP BV X V GP Figure 19 Vacuum diagram for the Ziirich oven Three thermocouples type N are used to monitor and cont
85. stment see TDC Elctronics Manual Analog Signals le SP950 SP950 SIS1100 3100 Ga oka U ECL gt gt 00 000 00000 GE 0 00 0000 000000 00000 MSCB o1000 0000 00000000 000000400 90000 Y CD950 CFD950 CFD950 SIS3820 V1190B MIDAS Linux PC Frontend MIDAS Linux WS Back nd Figure 7 Schematics of a typical VME elctronic crate for a bulk muSR experiment In additon to the CFDs TDC Scaler and VME PCI interface the crate is usually also equipped with a PSI Clock CD950 Also NIM ECL PSI converters LC950 and Coincidence Units can be installed The signals from the CFD s are sent as ECL signals to the TDC V1190 and 16 5 COMPUTERS AND ELECTRONICS Part II also to the scaler If hardware coincidence is necessary the ECL or NIM signal outputs of the CFD can be used with a PSI Coincidence Unit FC950 available from Studio E The signal can be fed back to the TDC and Scaler by the ECL output of the Coincidence Unit The signals from the TDC and Scaler are sent to a MIDAS frontend Linux PC through the optical link VME PCI interface In the front end Linux PC the events are checked for coincidence conditions and are sent to the Analyzer pro cess running on the Backend computer where the histograms are built according to the trigger and logics conditions
86. surements performed in Veto mode on a 4x 4mm silver sample 1 65 r T r T No veto mode 1 60 L Ag sample plate m A assumed constant v 1 55 L 0 o a S 1 50 L a o 3 145 z 1 40 L z a 1 35 L 1 2000 4000 6000 Longitudinal field G Figure 42 Evolution of the G parameter deduced from the Forward and Backward detectors by assuming a constant asymmery parameter Measurements performed in Non Veto mode on a large silver plate 90 19 WHAT TO MIND WHEN DETERMINING THE oa PARAMETER Part VI 19 What to mind when determining the parameter In addition to the problem explained above the users should mind some basics points when determining the a parameter For example a very slight field dependence of the alpha parameter on the value of the WEP field can be observed see Figure 43 This dependence arises from the vertical shift of the beam spot on the target This is demonstrated by the large shift observed in the a parameter for the Up Down detectors measured with the same beam condictions On the other side the effect on the o parameter for the Forward Backward is rather low but if extremelly precise determination of amp are necessary it is adviced to extrapolate its value at zero field by measuring at different WEP values 1 15 A Longitudinal Pol CC 110 WEP scans O Q G 1 05 Z 1 6 00 lt 0 95 0 844 Longitudinal Pol ry WEP scans co 0 840 O E 0 836 2 E
87. t a LakeShore 340 temperature con troller is used This last point can be performed directly from the Console running the application deltat e On the application deltat the LakeShore 340 is controlled by the front end Temperature_2nd_port This front end should run and configured to operate with the low temperature PID tables Part HI 8 TOP LOADING JANIS 4 K CLOSED CYCLE CRYOSTAT 57 Sample change in LTR The sample change can must be performed with the compressor cold head run ning Stop the heater by pressing the corresponding button on the HECTOR unit located near the LakeShore 240 temperature controller Disconnect the cable B from the electrical feedthrough of the sample chamber Pressurize the sample chamber with He gas by opening the 3 ways valve 3 2 valve on the sample chamber and the V He A valve Gas should blow through the overpressure valve located on the sample chamber Remove the sample stick and immediately connect the blind flange at the end of the sample chamber Isolate the sample chamber by closing the 3 ways valve 3 2 valve on the sample chamber Change your sample and be sure to dry the sample stick thoroughly When ready pressurize again the sample chamber with He gas by opening the 3 ways valve 3 2 valve on the sample chamber and the V He A valve Gas should blow through the overpressure valve located on the sam ple chamber Dismount the bli
88. t and evac uate the second port vacuum chamber to a pressure of 107 mbar or less Better vacuum levels provide greater insulation resulting in shorter cooldown times and lower final temperatures After evacuation is complete the compressor can be started After that the cold head starts to cooldown seal the vacuum valve V 2nd firmly see Figure 23 Outgassing and O ring permeation will cause the pressure to rise slowly over time therefore periodic re evacuation will be necessary Re evacuation is required whenever the minimum temperature obtained begins to increase He gas from bottle 3 2 Valve KX Sample Chamber sample stick pumping system to V He B Figure 23 Vacuum diagram for the 4 K CCR on the GPS 2nd port 56 8 TOP LOADING JANIS 4 K CLOSED CYCLE CRYOSTAT Part HI Sample mounting Remove the 4 K CCR blind flange at the end of the sample chamber insert the sample stick in position and fix it using the appropriate clamp Since within the LTR mode the sample is cooled by exchange gas special care in thermally anchoring the sample to the holder is not really needed Be sure to correctly position the sample stick horizontally and check the longitudinal position see Figure 24 Figure 24 Picture of the outer part of the sample stick with the distance ensuring that the sample inside the cryostat is located in the beam position Temperature control in LTR The MOGLI pumping unit can now be connected to
89. ter in the definition of the For ward counter strongly affects the form of the apparent field dependence of the reduced asymmetry 88 18 EFFECT OF THE FIELD ON THE amp PARAMETER Part VI T z T y T E T T T 0 25 LB a Veto mode 4x4 mm Ag sample a a assumed constant gt 024 L a D a E 0 23 2 8 K a 0 22 L z 0 21 1 1 A 1 4 P 4 0 1000 2000 3000 4000 5000 6000 Longitudinal field G Figure 39 Evolution of the asymmetry deduced from the Forward and Backward de tectors by assuming a constant parameter G Measurements performed in Veto mode on a 4x 4mm silver sample T T T T T T T T T T 0275 No veto mode 0 24 L B Ag sample plate 0 23 L assumed constant 0 17 L lill 0 1000 2000 3000 4000 5000 6000 Longitudinal field G Figure 40 Evolution of the asymmetry deduced from the Forward and Backward de tectors by assuming a constant parameter amp Measurements performed in Non Veto mode on a large silver plate Part VI 18 EFFECT OF THE FIELD ON THE PARAMETER 89 T T T T T T 7 T T T 0 95 F Veto mode 0 94 L 4x4 mm Ag sample SE naa L assumed constant 5 oO le E 0 92 0 91 L z z 3 0 90 L 0 89 L ig 088 L 4 L 1 1 1 1 0 1000 2000 3000 4000 5000 6000 Longitudinal field G Figure 41 Evolution of the parameter deduced from the Forward and Backward detectors by assuming a constant asymmery parameter Mea
90. the sample chamber valve V 2nd closed MOGLI on lock position pumping pipes connected to the Sample Chamber see Figure 23 and open the 3 ways valve 3 2 valve of the sample chamber Evacuate the sample chamber by putting the MOGLI on unlock Once sufficiently evacuate isolate the MOGLI by putting on lock and allow about 200 mbar of gas in the sample chamber through the valve V He A When done close the 3 ways valve to isolate the sample chamber The temperature control is performed by 2 GaAlAs diodes LakeShore TG 120 SD controlling two independent heater loops The first diode is located on the sample chamber tube the second one is located on the sample stick The temperature controller is normally a LakeShore 340 In normal operation in the Low Temperature Regime identical setpoints should be provided for both loops e The temperature of the Sample Chamber tube T ube Or Theater is measured on the channel 1 loop 1 s The temperature of the Sample Holder Tholder Or Tanalog is Measured on the channel 2 loop 2 The voltage loop 2 of the LakeShore controls an ex ternal Gossen power supply use exclusively the type 24K32R4 32V 4A Figure 25 indicates the necessary settings to interface both instruments The maximum current for the Gossen is therefore limited to about XXX Amp e Do not forget to switch ON the heaters by pressing the corresponding but ton on the HECTOR unit in case tha
91. value is saved The PUS will automatically retum to measuring mode The Conductus Neocera temperature controller should have a table oven_0800K With a trick temperatures higher than 800 K can be achieved To do so the reading of the temperature controller is divided by a factor 10 For example a reading of 100 K will correspond in reality to 1000 K For this configuration the analog output of the PUS Display has to be changed accordingly see table below and the sensor table oven_1200K has to be used Table 9 Correspondence between displayed temperature and analog output of the PUS Display to allow measurements up to 1200 K i e 120 K displayed on the Conduc tus Neocera temperature controller PUS Display Analog Output Celsius Kelvins Volts 0 273 1 0 0 926 9 1200 0 5 8 1598 0 1871 1 10 0 Part HI 7 ZURICH OVEN 53 7 5 Setup made by the Instrument Scientist if a LakeShore 340 Controller is used A PID table has to be prepared in the back end computer psw408 with name Zurich Oven pid It has to be stored in the directory usrdisk0 musr exp td musr dat 15340 Zurich Oven pid 1 analog loop zone file for zurich oven CDISP lt loop gt lt resistance gt gt O lt resistance gt Loop 1 only CLIMIT lt loop gt lt SPlimit gt lt heater max current gt lt heater max range gt gt S lt SetPointlimit gt gt C lt heater max current gt Loop 1 only 1 0 25A
92. y and frequently the pressure P and P2 in the Phase Separator and in the Sample Chamber An overpressure in the Sample Chamber could damage the titanium windows Disengage the adaptor of the transfer line from the top of the dewar by releasing the O rings Slide the adaptor upward along the transfer line Remove completely the transfer line on the He dewar side Replace the plug of the He dewar to prevent freezing of the He dewar Carefully warm up the transfer line using the available heat gun Be sure that the sintered end part is free of any ice Change the He dewar Check that the He recovery line is connected to the dewar and that the cor responding valves are open Be sure that the recovery line is not bent and that the He gas can flow freely Insert slowly the transfer line in the new He dewar As soon as the sintered part is enough inserted in the dewar lower the adaptor and connect it to the dewar Make sure that the adaptor of the transfer line is well inserted in the dewar and that all O rings are tightened Leave the transfer line above the liquid He level Stop blowing He gas by closing the valve V5 Open the valves on both He pumps do not forget if necessary to connect the electrical plug of the electrovalve V3b Open the valve VI completely Wait 30 seconds Pull down slowly the transfer line in the He dewar Check carefully and frequently that the transfer line is well aligned with the 36 6 QUAN

GPS User Guide - Paul Scherrer Institute

Contents

Download Pdf Manuals

Related Search

Related Contents