MuSR Manual
Contents
1. 3 Close the valve to the pump on the capillary line 13 4 Fill the sample space with He by turning black 3 way valve 8 downwards Wait until the flow meter on the He return line registers flow again 5 Remove the sample stick quickly but smoothly by undoing the Klein flange Cover the sample space with the blanking flange Return the 3 way valve 8 to its horizontal position 6 If the cryostat is to be left for a time without a sample present pump the sample volume via the 3 way valve 8 turned to upwards position using the rotary pump connected to the port above the valve Loading a sample 1 Ensure the sample stick is completely dry before inserting it into the cryostat 2 Ensure the cryostat is at about 25 K 3 Ensure the cryostat is connected to the He return panel or that a non return valve is fitted to the He outlet 7 4 Fill the sample space with He by turning the black 3 way valve 8 downwards Wait until the flow meter on the He return line registers flow again 5 Remove the blanking flange and introduce the sample stick quickly but smoothly 3 6 Pump the sample space via the 3 way valve 8 turned to its upwards position to 1 mbar the gauge on the top of the cryostat 10 reads the sample space pressure using the rotary pump 7 Turn the 3 way valve 8 to its downwards position to add He to the sample space and pump again to about 1 mbar 8 Add He to the sample space again and pump until th2. Relaxing asymmetry 96 I PARRA RE RE 0 T 2 3 4 Be 6 7 8 9 Number of 25 um Ti foils 0 10 20 30 40 50 60 70 80 90 100 Range mg cm Figure 7 Range curve for the Blue Variox Cryostat The range curves are different for each cryostat and those which are significantly different from the Variox curve shown here are included in the sections for each cryostat 2 5 Magnets The MuSR spectrometer has three sorts of magnets acting on the sample position zero field compensation coils calibration T20 coils and the Helmholtz coils that act as the main magnet They are set to act individually through the SECI program 2 5 1 Main magnet The main magnet can be used to provide up to 2500G in longitudinal mode and around 600G in transverse mode limited by the frequency response To switch on the main magnet use the SECI command 1 0 SECI should write Danfysik power supply has been selected After this commands of the form setmag nn where nn is the desired field can be used to set the field 2 5 2 Calibration coils The calibration coils are used when the spectrometer is in longitudinal mode to provide a small transverse to calibrate the difference in count rates in the forward and backward detectors They hang from flexible hooks next to the cryostat space and have a power cable leading from the downstream wall of the spectrometer area When inserting them before putting the cryostat into the spectrometer check tha
3. UDA See the old MuSR instrument manual 6 Further information 6 1 ISIS User Office Transport accommodation The ISIS User Office on the ground floor of building R3 room G11 should be contacted with queries about transport and accommodation related to your ISIS experiments Website http www isis stfc ac uk user office useroffice html Email isisuo stfc ac uk Telephone Fax 44 1235 445592 44 1235 445103 6 2 Food Breakfast for users staying in Ridgeway House is available there Breakfasts lunches and dinners are served in the R22 cafeteria Light lunches are also available in the R1 coffee lounge Vending machines are situated in the User Lounge in the Experimental Hall R5 5 next to the entry to the hall from the Main Control Room Opening times are listed on a sheet in the instrument cabin and on the ISIS User Office website http www isis stfc ac uk user office refreshments4424 html 6 3 Contact numbers Here is a list of useful numbers that you might find useful Except where stated these can be dialled from outside the lab by preceding them by 44 0 1235 44 Main control room MCR 6789 MuSR cabin R55 6135 EMU cabin R55 6831 HiFi cabin R55 6851 Experimental Areas 6338 ARGUS RIKEN 6766 Health Physics Sample checking 6696 Computer support 1763 07770858090 from outside the lab User Office 5592 Cosener s House 3007 01235 523198 Local taxis 5592 Ring
4. sssesssssseseseeeeeeeeeennnn nnne enne nnns snnt nnns 21 Figure t3 Site map of RA eseu ed dE ee eege tede ene 29 1 Introduction This manual is designed to provide all the basic information needed to perform an experiment using MUuSR If there is anything you remain unsure about you should check the details with your local contact or one of the instrument scientists Before starting to collect data it is worthwhile to check the following things are set up as desired e The instrument geometry longitudinal or transverse described in section 2 2 e The spectrometer area has been cleared of personnel the interlocks have been set correctly and the beam blocker has been raised to allow muons through to the sample The procedures for doing this are explained in section 2 3 e The magnetic field is correct for a Compensation of the Earth s magnetic field b Calibrations c Measurements The procedures for setting the magnets are described in section 2 5 e Sample environment is working as expected section 0 e The beam slits and steering are chosen to match the size of the sample and the desired event rate This is described in section O e The data acquisition and analysis software have been set up correctly These are described in sections O and O respectively This manual also includes the details of how to access and analyse the data recorded section 0 and information for ISIS users section O At the end of the manual
5. 10 Dantysk zl Step 14 t KEEP 0 10 20 10 10 Danfysk gt Magnet Dantysik 5 xo 340 0 o 5 5 10 Dantysik gt 16 KEEP KEEP D 10 20 10 10 Danfysik zl om v 3 380 o 0 5 5 10 Dantysik sl Command 1 rae E exa 1 cum T o 2 T P GS ee hb T a il 18 KEEP KEEP D 10 20 10 10 Danfysik xl Add AR Delete Enty 19 400 400 0 0 5 5 10 Danfysik v 20 KEEP KEEP 0 mi 20 10 10 Danfysk gt ch m a 38 360 0 0 5 5 10 Danfysk v Script Run Time Info 22 8 l KEEP KEEP D 10 20 10 10 Danfysik zl Current Count Rate 30 MeV hr 23 320 d 320 0 0 5 5 10 Danfysik EI Total Mevents in script mo 24 KEEP KEEP 0 10 20 10 10 Danfysik xl 25 20 280 5 5 10 Danfssk zl 7 Est length of script 24 hrs 0 mins Een i 3 E Script Table Read only U PJBLip8 gcl Figure 11 MuonScript window with representative entries In the menu on the top left of the window Read allows previously written scripts to be opened for editing Write saves the currently written script and Clear Script empties the current contents of the MuonScript window To add an entry type in the required temperature field selecting main longitudinal field or calibration and number of million events MEv then click Add If no change is required leave the temperature and or field values blank instead of re entering the same value this avoids having to wait to confirm
6. MCR outside office hours Airport transportation 24hrs notice required 5592 Further useful numbers can usually be found written on the cabin doors Contact details for instrument scientists can be found via the muon group website http www isis stfc ac uk groups muons muons3385 html 6 4 Connecting a laptop computer When you arrive at ISIS you should be given a coupon providing the connection details to the wireless internet at RAL If this has not happened you should speak to your local contact This is the preferred method of connecting while on site and should be the simplest to use The wireless internet reception in the MuSR cabin is not always adequate so cable connections to the internet are also available Speak to your local contact if you have any difficulties in setting this up It is likely that you will need to change the proxy configuration of your internet connection The automatic proxy configuration URL is http wwwcache rl ac uk proxy pac 6 5 Sitemap Ridgeway House Main Gate ISIS Main TUR EA N HEL Entrance Figure 13 Site map of RAL Appendices A Pulsed techniques that can be used with MuSR Some pulsed techniques such as Radio Frequency p SR can be used with MuSR See documentation on the Muon Group website 7 Troubleshooting If something appears to be wrong then users should contact their local contact for assistance However there are a
7. few things that could be checked first 7 1 No muons or very few muons Is the proton beam on Check the beam current display in the hall and in SECI check MCR News and Beam Status The beam displays take a few seconds to update and the MCR might not send a message until they have some idea what went wrong Base rate used to set up the accelerator causes a corresponding reduction in muon count rate by a factor of 32 Did you open the shutter The Beam On light over the area door the red shutter open light by the shutter control buttons and the blue lights inside the area should be lit The Kicker may have tripped This vetoes data taking in all instruments to avoid accumulating double pulse data or just background turns on a flashing yellow light in the MuSR cabin and sends an alarm to the MCR who should reset it Resetting takes 5 minutes if the beam has not returned after this time phone the MCR Has a muon Beam Off button been pressed This turns off the muon beams and the white lights come on in all the muon areas Check if someone is locked in an instrument area or has used the emergency release break glass bolt on the door Anyone who is in any instrument area or blockhouse when blue lights come on should contact the MCR after pressing the beam off button 7 2 Counting but strange data Is your data analysis correct the right grouping and alpha Try with another program if in doubt Be sure you are looking a
8. field of 20G 1f 0 Switches on the Danfysik power supply to control the main magnet setmag nn Sets a magnetic field of nn Gauss Works with either Danfysik or calibration supply This command doesn t do anything if the zero field compensation system is on settemp nn Sets a temperature of nn sleep nn Waits for nn seconds
9. the Sorp temperature to 40K Please ensure that heater 1 is selected 2 Onthe Lower ITC5 Cool the 1K pot to 1 6K as a rule the 1K pot pump pressure should be 6mbar and the needle value 10 1296 3 Leave for 30minutes with the 1K Pot temperature less than 1 7K and the Sorp at 40K Cool the sorp to 4K open the needle value to 2596 but remember to close the needle value as soon as it is cold Failure to do so will result in the needle valve freezing 5 Ensure either the high temp low temp switch is on low temp or the heater 1or2 on the lower ITC5 is selected Failure to do so will reduce the Hei hold time from 30 hrs to 2hrs Heating and cooling above 1 6K 1 Sendaset point and ensure that the high temp low temp switch is on high temp CHECK 2 Oncooling back down from high temp Send a set point and heat the sorp to 19K The cooling power is low and this can take a long time 4 6 Furnace A description of the furnace will go here 4 7 CCR A new CCR for MuSR will be available soon 4 8 Small flow cryostats SECI Configuration Names Flow itc502 Flow_itc503 OpenGENIE Commands N A The temperature range is 4 to 400K for the normal flow cryostat and 6K 600K for the cryofurnace flow cryostat They are mounted in a frame that is lowered into the spectrometer from above with the transfer tube on the downstream side of the cryostat The locating pin on the top flange of the cryostat will then be on the beam window si
10. Configuration from the menu at the top of the SECI window This should be carried out with your local contact when there is a change to new sample environment Those cryostats that have more than one centre stick will have a configuration for each stick and it is important to change these appropriately temperature control and monitoring relies on this 3 2 SECI OpenGENIE commands Experiments are normally controlled by typing commands into the Open Genie command line window on the Dashboard page in SECI Commands are not case sensitive BEGIN Starts a run Asks for a sample name and other details The temperature and field entered here are used only for the file header and do not set anything END Finishes and saves a run There is a last chance to change the header details PAUSE Pauses data acquisition RESUME Resumes data acquisition LFO Selects the main magnetic field initially set to zero SETMAG value Sets the magnetic field to the specified value in Gauss FO Sets zero field using the Hall probes and X Y and Z coils This is a one off adjustment each time FO is typed not continuously monitored as on MuSR TFCAL Selects the transverse Y coil and sets it to 100G for calibration Other values can then be set if required SETTEMP value Sets the temperature on the cryostat CCR furnace usually in K The SETTEMP command also sets the appropriate control paramete
11. Configure VIs 250 Edit Tabs E Configure Blocks a 200 Display Blocks Status i 150 Open Genie Scripting 4004 AE 50 0 System Messages 11 36 00 11 37 00 11 38 00 11 39 00 Beam Status Time ISIS News Report a Problem d 35 lines scanned compiled Open GENIE successfully started at 15 Feb 2011 11 35 25 01800 48 lines scanned compiled oading Smalltalk image from C Program Files x86 gt CCLRC ISIS Facility Open GE TE genie im oading TCL commands Cif needed from C Program Files x86 gt CCLRC ISIS Facilit NOpen GENIE sre tclNinterface tcl pen GENIE U2 3 BUILD 5776 2810 82 24 15 57 01 Linked Feb 24 2018 19 43 44 library version 1 2 KRunning on x86 Windows_NT 6 1 built with MS Visual C U5 0 or greater Copyright lt C gt 1996 2882 CCLRC Rutherford Appleton Lab Open GENIE comes with ABSOLUTELY NO WARRANTY for details type warranty This is free software and you are welcome to redistribute it under certain conditions type licence for details K KKK Figure 10 SECI dashboard with the Open Genie tab displayed 3 1 Loading configurations To use any piece of sample environment with SECI it needs to load the control and monitoring information for that piece of sample environment This information is stored in configuration files that are saved after the equipment has been calibrated The configuration files are loaded either when SECI is restarted or by selecting Open
12. ISIS MuSR Manual P J Baker A D Hillier J S Lord and S R Giblin 29 June 2011 Contents pMEB le ere Ile e E A 2 TheMusbspertroineter ee EES 5 2 4 Instrument features and Layout 5 2 2 Rotating the spectrometer eene ener nn snn nnne nnne nnns 5 2 3 ET EE 5 2 3 1 Closing the area sonne nuege intei mid SIDE 6 2 3 2 Opening the area X 6 2 4 Muonbeam eni eee dae eue uten hk ea 7 2 4 1 Rate spot size and slit positions eese entente tenete tatnen nnn 8 2 4 2 Freq erncy response eegenen 10 2 4 3 eliam EE 10 2 9 E EE 11 2 5 1 Main ASM uL 11 2 5 2 Calibration Coils 11 2 5 3 Zero field compensation esee eese enetatntntntn tnnt ta tata tata ta sane nnna 12 2 6 Detectors and Data Acquisition Equipment essere 12 2 6 2 Data Acquisition Equipment s sssssssssssssususnenununnunununnunanunnununnnnunununnununnnnanunnnnnnunnananannnnana 13 2 6 3 Computers available eegene 13 3 Using SECI Sample Environment Control Interface eer 14 3 1 Loading configurations gecisi nene feet noue eheu en ene ERR a dle et eee en 14 3 2 SECI OpenGENIE commande 15 3 3 Mu uonScrpt os eer e teer ETE eee EY ER Ee ERR RR ER Ie e eR 16 4 Sample Environment eeseeeeeseseseseenn tnnt ta tenete tata tata nEsEsEsE Passa sa sa SE sn sEs Ms mss ss ss so so so sa me
13. Show all control blocks or use Display Blocks Status in SECI see left of Fig 9 3 3 MuonScript In order to produce consistent data with MuSR it can be helpful to run through a regular series of measurements with the same counting statistics and following a planned pattern of temperature and magnetic fields This can be done by writing a script in the MuonScript window of SECI and executing it in the OpenGENIE window We use a program MuonScript to generate a script from a table of fields temperatures and run lengths A new script can be edited while a previous run or script is still in progress MuonS cript Script Details Read Write Clear Script 60 60 0 0 5 5 10 Danfysik zl _ Pint Lose 2 KEEP KEEP 0 10 10 10 Danfysik v Details LS J wow p E pe p o9 E C 10 Dansk General 4 KEEP KEEP o 10 20 10 10 Danfysik zl Entries D Events MeV 10 5 140 140 0 0 5 5 10 Dantysik gt Temperature 6 KEEP KEEP D 10 20 10 10 Danfysik EN Start 7 180 180 H 5 5 10 Dantysik zl E amp 8 KEEP KEEP 0 10 20 10 10 Danfysk zl se n 5 220 m ae ups 00 Datis I 10 KEEP KEEP D 10 20 10 10 Danfysik zl Field n 260 0 5 5 10 Dantysik Stat IT 1 Sep Dantys z 12 KEEP KEEP 0 10 20 10 10 Danfysik xl End 13 sm 300 0 0 5 5
14. actually closed when the controller thinks it is fully open the ITC5 temperature controllers can sometimes get confused like this particularly after large temperature changes in Auto flow mode Switch the controller s main power off and on again to make it reset the valve then check it is set back to auto operation and re send the set point with settemp nn e The flow valve or capillary is blocked Ask for assistance to get it unblocked If the cryostat CCR will not warm up on demand warms rather slowly or cools below its set point The heater protection circuits have tripped For the ITC controller it may say Hot 1 or Hot 0 on the display Check that all the thermometer leads are plugged in then switch off and on again to reset For the Eurotherm controller CCR there is a small reset button to be pressed The CCR also has a thermal switch on the cold head check that the compressor is still running especially with set points above room temperature The heater itself or a lamp in the furnace has burnt out Ask for assistance The CCR has to be warmed up and withdrawn in order to replace its heater The helium flow valve is stuck open when the controller thinks it is shut There will be a large flow of gas and the pumping lines will be covered with ice Reset the controller to close the valve and then re send the set point If the temperature does not stabilise The P I D parameters or maximum power are incorrect f
15. any period Rapid consumption of cryogens is often a symptom of a malfunctioning cryostat Information on cryogen levels is usually presented on the instrument dashboard section 5 2 or in SECI Otherwise the level gauges connected to the cryostats can be read directly 4 1 Oxford Instruments Variox cryostat SECI Configuration Names Blue itc502 Blue itc502 Boost Blue itc503 Blue itc503 Boost OpenGENIE Commands blue 1t Operation below 4 5K blue ht Operation above 4 5K boost Allows use of boost heater The range curve for this cryostat is shown in Figure 7 4 1 1 Setting up and changing sample The cryostat will be craned into place by your local contact and the necessary electrical connections made The ISIS sample environment group will endeavour to maintain suitable cryogen levels during your experiments but it is important to check that it contains sufficient cryogens before leaving it unattended for any period Both helium and nitrogen levels should be monitored Removing a sample 1 Ensure the cryostat temperature is greater than 25 K too low a temperature and any liquid helium that has been pulled through the capillary could boil rapidly too high a temperature could cause He gas to diffuse through the Mylar window into the outer vacuum space 2 Ensure the cryostat is connected to the He return panel or that a non return valve is fitted to the He outlet 7 3 Close the valve to the pump on the capilla
16. are the troubleshooting section and a brief guide to commonly used SECI commands 2 The MuSR spectrometer 2 1 Instrument features and layout The MuSR spectrometer has 64 detectors each comprising a scintillator light guide and photomultiplier tube PMT These are arranged in two rings facing each other on opposite sides of the sample position High voltage cables take the PMT signals to the data acquisition equipment in the rear of the instrument cabin There are three sets of magnets that can be used with MuSR fixed zero field compensation coils the main magnet producing up to 2500G and removable calibration coils to produce fields perpendicular to the main magnet Next to the spectrometer is a small platform which is needed to guide cryostats in and out of the spectrometer when in longitudinal mode A set of stepladders is provided for this purpose when the spectrometer is in transverse mode or if further access is required The instrument cabin has computers for controlling the spectrometer through the SECI program monitoring the progress of the experiment and carrying out data analysis Samples should be mounted in the prep lab across the loading bay from the instruments and cabins towards the synchrotron Any sample preparation should be done on a tray labelled with one of the forms kept in the lab door 2 2 Rotating the spectrometer The spectrometer can be rotated from longitudinal to transverse mode in around 30 minutes This pr
17. ause To resume the run type resume This will avoid accumulating empty frames which will upset the dead time calculations 4 Sample Environment The following sample environment is available to be used on the MuSR spectrometer The choice of sample environment is normally confirmed with the local contact at least several weeks before the experiment is run It will then be prepared by the ISIS Sample Environment group and will be ready for the start of the experiment Cryostats working below 1K require some preparation by the user before the beam time starts as is explained in their sections below Equipment Schedule code Temperature range Manual Section Oxford Instruments Variox OXF MuSR 1 5 300 K 4 1 Oxford Instruments Variox OXF Beast 1 5 300 K 4 2 TBT Dilution Fridge DR TBT 0 04 4K 4 3 Oxford Instruments Fridge DRI MuSR 0 04 4K 4 4 Sorption refrigerator SR Mu 350mK 50K 4 5 Furnace Fur Mu 300 1000 K 4 6 CCR coming soon CCR MuSR TBC 4 7 Small flow cryostat 5 600K 4 8 Long flow cryostat FLO HiFi 4 300 K 4 9 As well as preparing the cryostats before an experiment the ISIS Cryogenics group does their best to keep them topped up with cryogens while experiments are running Nonetheless it remains the users responsibility to check that the levels are sufficient particularly when large temperature changes or sample changes have occurred and if leaving the experiment unattended for
18. ck that no one is inside the MuSR area Press the search button situated on the far side of the spectrometer and close the area door and remove the key from the lock turning anticlockwise Insert this key into the key box to the right of the door turning it clockwise 3 The key box should now be full 4 The blocker can now be raised press the raise button next to the small red light bulb and keep it pressed until the blue area lights come on and the blocker has stopped moving 2 3 2 Opening the area To enter the MuSR spectrometer area 1 Check that the magnetic fields applied on the instrument are compatible with safe entry to the area It is necessary to switch off the main magnet and calibration coils when changing cryostats 2 Lower the blocker by pressing and holding the green button The white area lights come on once the blocker is down 3 Remove the topmost available key from the key box by turning it anticlockwise and insert it into the door lock turning clockwise There is no longer a separate bolt The door can now by opened by removing the locking bolt 5 If it is necessary to open the gate on the MuSR platform remove the topmost key from the key box and use it in the gate lock 2 3 3 Muon beam off buttons In an emergency the muon beam can be immediately switched off by pressing a muon beam off button such as that pictured below If this happens you should inform your local contact who will be able to reactivate t
19. de Use the appropriate ITC5 temperature controller for the cryostat and connect through the patch panel Start pumping the OVC using a turbo pump Connections Cryostat sample space port to a T connector which is connected to He gas gauge and rotary pump Cryostat heater thermometer to ITC channel 1 the stick thermometer to ITC channel 2 stick A or 3 stick B and the transfer tube needle valve to ITC Aux Out through the patch panel Transfer tube gas outlet at the top of the dewar leg to the pumping box via a long plastic tube Inserting the stick The sample can be changed when the cryostat is cold but heat it up to gt 25K first 1 Letthe sample space up to 1 atm with helium and remove the blanking plate 2 Insert the stick the pin on the stick flange locates into the hole in the flange on the cryostat 3 Pumpthe sample space purge with helium repeat and admit 15 mbar of exchange gas Cooling 1 Checkthat the PTFE sealing washer is present on the cryostat end of the transfer tube Connect the needle valve cable Turn the ITC5 on This initialises the valve Fully open needle valve press amp hold Gas Auto then press Raise keep in Manual light off Check with your local contact that the dewar has the helium level probe installed H esa sso Insert the leg of the transfer tube in the dewar Be very careful not to bend the transfer tube In practice the tube will need to be almost fully inserted into the dewar before th
20. e 29 App peA d CS e ER 29 A Pulsed techniques that can be used with MuSR s sssssssssusnunsusnneunnunnunuunnnnunnunnnnnunnnnunnnnnnnnnnnnnnnnn n 29 Ze Xro bleshooting dude Eeer 30 7 1 No muons or very few muonsl sees rennen nnne nennen tnter en 30 7 2 Counting but strange data 30 7 3 Temperature seed ette edet ed ied ene er de e eue en rase eve esee Eee SER dehet 30 8 Quick Guide to SECI cssssssssssssssererseseceeeeeeseeseseeeesnsnaneneneeeseeeneeeeseseasseeesearauanenenenseeeeeeeeeeensaeneeesnsnananes 32 List of Figures Figure 1 MuSR in its longitudinal and transverse orientations esses 5 Figure 2 Interlock key box master switch and main door lock seen 6 Figure 3 A muon beam off button sesen oeeaaeaii ena eaea e ane aeria aas aaa a ea ineat aasa 7 Figure 4 Layout of the muonbeamlines 8 Figure 5 Graph of asymmetry and rate vs Slit position 9 Figure 6 Frequency response in MUSR eese nnnnnnnnnn nnn inihi iari n nanus 10 Figure 7 Range curve for the Blue Variox Cryostat ccccccccccccsssesssecececessesseseceesceeseesesnsaeeeesesseessaaees 11 Figure 8 Zero Field vi in active compensation mode 12 Figure 9 MuSR detector numbering 13 Figure 10 SECI dashboard with the Open Genie tab displayed eene 14 Figure 11 MuonScript window with representative entree 16 Figure 12 Range curve for Beast Variox Cryostat
21. e sample space gauge 10 reads 20 mbar This is the correct exchange gas pressure 4 2 2 High and low temperature mode operation For temperatures above 4 2 K the cryostat can be operated with the gas flow valve under automatic control having set blue ht in the OpenGENIE window To achieve stable temperatures below 4 2 K it is necessary to control the gas flow valve manually Issue the command blue 1t in the OpenGENIE window and check that the gas flow control in the temperature window of SECI is showing Manual Connect the flow gauge attached to the Rootes pump frame to the exhaust and adjust the gas flow using SECI until the exhaust flow rate is around 450cm min The temperature should drop rapidly to below 2K Small adjustments to the flow rate may be needed to ensure a stable temperature Ensure that the temperature can be stabilized at the desired base temperature and disconnect the flow gauge to prevent it being clogged by oil Set points can be set in the conventional manner up to around 5K To return to higher temperature operation the blue ht command should be issued in OpenGENIE 4 3 TBT dilution fridge SECI Configuration Names TBT OpenGENIE Commands N A This is a stand alone dilution fridge working from around 40 mK to 4 2 K Users need to arrive at least 24 hours before their beamtime to allow the sample to be mounted and cooled off beam before measurement The ISIS Sample Environment group and the local contact
22. e transfer tube can be inserted into the cryostat Reduce pressure in the dewar as required with the red valve 6 Putthe transfer tube into the cryostat and tighten the locking nut Turn on the diaphragm pump Open the valve on the pumping box There should be a very small flow 7 After about 5 minutes the flow should increase as liquid reaches the cryostat beginning cooling 8 The Green valve on the dewar should be open and the Red valve closed during operation 9 Ifthe cryostat is still not cooling after 20 minutes the tube may be blocked with ice or solid air 10 Remove the transfer tube from the cryostat and dewar Warm both ends with the hot air gun Blow clean helium gas through it use a piece of rubber tube over the cryostat end Removing 1 Warm the cryostat to 25K or above 2 Ensure the needle valve on the transfer tube is open set the ITC5 to Local press Gas Flow and Raise then shut the valve on the pumping box The pressure should rise rapidly to 1 atm If it doesn t check with your local contact 3 Thetransfer line can then be removed Be careful not to bend either of the legs If the cryostat will be used again during the experiment the transfer line may be left in the dewar with the needle valve closed Be sure to fit the protective tube over the free end of the transfer line 4 Unplug all electrical leads from the cryostat Close the sample space tap and disconnect the sample space pumping line 5 Close the OVC
23. he beam once the emergency has been rectified Figure 3 A muon beam off button 2 4 Muon beam MuSR receives the second of the two pulses of surface muons that come from the muon target every time the ISIS synchrotron sends protons towards the neutron target Before it reaches the spectrometer it is focused and steered to control where the muons hit the sample in the cryostat This is done using a combination of dipole and quadrupole magnets that are shown in the figure below The focussing and steering of the muon beam will have been checked during the calibration period at the start of each ISIS cycle If a change to the focussing or steering is required for your experiment you should speak to your local contact The two pulses of muons that travel from the muon target are separated using an electrostatic kicker before the EMU and HiFi beamlines branch off from the MuSR beamline This uses a large DC voltage to split the first of the two bunches of muons so they can be steered into EMU and HiFi dipole HiFi ha od n kicker separator steering magnet SN 4 tre 4 quadrupole Jt MuSR Chr e mep emm b of focusing magnet ET muon Do LL production These components are unshielded to neutron and are visible from the platform production target above the beamlines 5 proton beam Figure 4 Layout of the muon beamlines 2 4 1 Rate spot size and slit positions The count rate is controlled by varying the n
24. in each detector that recovers exponentially at short times With the present instrument set up the optimal counting rate is 40 45 MEv h The choice of slit position to achieve this varies with the cryostat used 2 4 2 Frequency response Because the bunch of muons arriving in the sample do not arrive at the same instant any transverse fields within the sample cause the muons to precess relative to each other during the period they enter the sample The result of this is that the asymmetry of precession signals decreases as a function of the transverse magnetic field as can be seen in the figure below The same effect applies to oscillations due to fields inside samples and also to relaxation rates and places a limit on what can be measured using ISIS muon instruments Frequency response of the USR signal Asymmetry N 0 2 4 6 8 10 12 Frequency MHz Figure 6 Frequency response in MuSR 2 4 3 Range curve It is very important that the muons stop in the sample rather than in the mount or cryostat Getting this right can be achieved by examining the range curve For the Variox cryostat the range curve is shown in figure number The aim is to have the sample centre at the midpoint of this curve To adjust the stopping range silver titanium or mylar sheets can be placed in front of the sample The best approach can be discussed with your local contact Range curve for Blue Variox Cryostat 11 11 09 D a SS 1 20 4 0
25. in the experiment Clicking on an individual run shows the metadata associated with the file Runs can be downloaded by selecting them and clicking the download button Below the download button is a box to select all the files in the set There are also options to search through your data and list your data If you wish to send a particular location in iCat to another member of your experimental team so they don t have to navigate to a particular view then the hyperlink can be copied as it points to the current view This works if the person opening the link has the appropriate access permissions New ISIS datasets are allocated a digital object identifier DOI which can be referenced when the data are published If you require a DOI for data taken before 2011 speak to your local contact or a member of ISIS staff 5 2 Dashboards A dashboard showing the status of MuSR can be monitored remotely from a web browser or WAP enabled mobile phone Go to http dataweb isis rl ac uk and select dashboards then MuSR This shows the temperature magnetic field and the data acquisition system status Run titles are redacted 5 3 Data analysis software There are a number of software packages that can be used to analyse MuSR data Their manuals can be consulted for more information Here are some links to them WiMDA http www isis stfc ac uk groups muons downloads wimda installation notes7856 html MANTID http www mantidproject org Main Page
26. lds it actually sets If you are about to start measurements on a new sample using a script use the SETLABEL command to ensure the sample name etc are correct If you have just set a temperature or field the script will not put this in the header either again use SETLABEL Finally type runscript to start the script When a script changes temperature the TPAR parameters Accuracy Wait and Timeout for the new set point are used The control temperature readback must be within Tset Accuracy continuously for the Wait time in minutes before the next run starts No check is made on the sample log temperature the Wait must be long enough to allow it to come to equilibrium For very large samples Wait may have to be increased If the temperature is not stable after Timeout minutes even if it had just reached the set point and the Wait interval is now counting down the run starts anyway To stop a script Ensure the OpenGENIE window is active and press Ctrl C There may be a message about wait cancelled then the prompt returns If a run was in progress it will still be running and will not stop at the number of events specified in the script use end to stop it when appropriate Alternatively you might write a new script or edit the old one to complete this run and continue To pause a script during a run for example while closing the blocker and entering the area go to the OpenGENIE window and type p
27. lium exchange gas and then close the sample space valve on the cryostat More gas pressure may help with low temperature operation or to prevent electrical breakdown with RF measurements Turn off the scroll pump when finished It may be necessary to disconnect the pumping line in order to close the sample pit door or because other instruments users will need the pump Reconnect the thermometer cable Check it is using the appropriate channel on the temperature controller and is reading approximately the same as the cryostat channel 1 or cooling towards that value for a warm stick inserted in a cold cryostat If using a different stick to before don t forget to change the configuration in SECI To change between helium storage dewars you should ask your local contact or a member of the ISIS sample environment team for assistance 5 Data analysis 5 1 Accessing the data While at ISIS the data can be accessed directly from the data analysis computer in the MuSR cabin To access the data remotely use the iCat portal at http data isis stfc ac uk You will need to log in with your STFC Federal ID and password To retrieve your data click on the My Data tab You will be presented with a list of the experiments you have carried out at ISIS which can be sorted according to RB Number Title Facility and Date The data can be downloaded by clicking on the experiment in the listing which opens the Datafile Window This lists the data sets
28. mmand fO in the OpenGENIE window 2 6 Detectors and Data Acquisition Equipment 2 6 1 Detector positions and grouping MuSR has 64 detectors arranged in two rings around the sample position In order to form a longitudinal forward backward grouping detectors 33 64 are summed to form the forward set and detectors 1 32 summed for the backward set In the transverse case the two detector arrays are perpendicular to the initial polarisation direction A suitable way of grouping the detectors in this case is in four groups of eight top 17 24 49 56 bottom 1 8 33 40 forward 9 16 57 64 and backward 25 32 41 48 These sets can be analysed separately or further arranged into forward backward sets top bottom forward backward Beam In Detector 40 Figure 9 MuSR detector numbering Detector 33 is on the far bottom corner from detector 1 2 6 2 Data Acquisition Equipment The Data Acquisition Equipment is kept in the instrument cabin 2 6 3 Computers available Three computer screens are permanently installed in the MuSR cabin The screen on the right hand side of the cabin nearest the DAE is used for running SECI to control the instrument MUSR This is mirrored on a screen on the muon area platform The screen in the middle of the cabin shows the status of the experiment and control parameters on the instrument dashboard The screen on the left is used for data analysis and has a number of suitable programs installed
29. nnaan nnna 18 4 14 Oxford Instruments Variox cryostat sse eterne nnne 19 4 1 1 Setting up and changing sample esent tnnt tette tate ta tenen 19 4 1 2 High and low temperature mode operation eene 19 4 1 3 BOOSt MOE 9 5 20 4 2 Oxford Instruments Variox Beast sse 21 4 2 1 Setting up and changing sample eese eese tenente tenen tnn te teta tas 21 4 2 2 High and low temperature mode operation eese 22 43 TBTdimiuton fridge uH RHET e ER teta een tette 23 4 4 Oxford Instruments dilution fridge sse 23 45 Sorption refrigerator oo Ren eee ie RETRO RR e te eee eens 24 4 6 UPN ACC ener EE 24 ADE KN E 24 4 8 Smallflow crvostats cece ceeeeeeeceeeaeeeacecaaeeeaeeeaeecaaecsaecsaecsaeseeeseeeseaeeeaeeeaeeeaeeeaes 25 4 9 E RA e E E 26 5 EECH LEA 27 5 1 Accessing the date ege rS e ete e P n Gath Ye Tee Re deeem 27 5 27 Dashboards i285 crete nia tate tee eed on it tot eerte 27 5 3 Dataanalysis software E 27 6 Further infOrmation PEE 28 6 1 ISIS User Office Transport accommodation esee 28 62 FOO0d oso d o ee d ees 28 6 3 Contact numbers EE 28 6 4 Connecting a laptop computer sessi nnnt tenentes inneren 28 6 5 SHUG map eerie tempera er ree ee a deer ea ana e ea de aee RE dav
30. ocedure must be done with a local contact present to move the cryostat in and out of the spectrometer and to ensure no damage is done to the spectrometer or any of the apparatus within the area A list of people authorized to supervise the spectrometer rotation is displayed on the fence of the spectrometer area magnets and detectors c NA P d M magnet and detectors u e sample TM e sample magnet and detectors Transverse Field Longitudinal Field Figure 1 MuSR in its longitudinal and transverse orientations 2 3 Interlocks In order to ensure the safety of personnel around the MuSR spectrometer the muon beam has a series of interlocks that prevent muons entering the spectrometer area whilst people have access This section describes the procedures for exiting and entering the MuSR area under normal operating conditions Some pulsed techniques such as Radio Frequency uSR have a further series of interlocks that are explained in their appendix to this manual Figure 2 Interlock key box master switch and main door lock 2 3 1 Closing the area To leave the MuSR spectrometer area 1 Close the gate which allows access above the spectrometer on the top of the MuSR platform remove its key and insert into the key box to the right of the lower area door Turn the key clockwise The locking pins need to be in the vertical plane for the lock to be shut and can be easily adjusted if they have misaligned 2 Che
31. on the attached computer MUSRO1 Power sockets UK and EU are available for laptops and Ethernet cables and sockets are available if the wireless signal proves inadequate Further information on this is provided in Section 6 4 3 Using SECI Sample Environment Control Interface The data acquisition magnets and all the sample environment equipment that are involved in doing an experiment using the MuSR spectrometer are controlled using the SECI program A brief guide to the most commonly used SECI commands is printed on the back cover of this manual Here the more detailed aspects of using SECI are explained ILE Sample Environment Control Interface Version 1 0 9 18933 m x File Manager Temperature Temp N2 Level 90 300 96 Field Steering Next Run 31531 Temp Cryostat 163 660 K a selected magnet Danfysik Steer HSM 0 0 11 39 15 February 2011 e Temp_Sample 309 100 K Field_ZF_Magnitude 2 00e 004 G Steer VSM 0 2 User s test Title DAE Test Current Run Time 00 22 09 Total Mev 0 Temp_GasAuto Manual Field_T20 0 000 G Temp_HeaterAuto Automatic Field_Danfysik 0 000 G Temp_Gas 79 000 Field_Emu 0 000 G Good Raw Frames 0 0 Count Rate 0 Temp_Power 0 000 Field_Hifi 0 000 G Current Period 1of1 Kicker Status OFF Temp He Level 96 800 96 P Temperature Experiment Details Temp Cryostat Temp Sample Temp Cryostat Setpoint LabVIEW VIs 350 Add VI Remove VI 300
32. or this sample Some adjustment may be necessary with large samples or special centre sticks or in the furnace The wrong calibrations are being used or the sample and control thermometers are swapped Is the stick connected to the correct channel on the temperature controller The helium flow rate is much larger or smaller than intended for this temperature Check the flow valve Sometimes the auto flow algorithm does not stabilise and it helps to set the valve to Manual operation this is OK for operation at a single temperature or small changes One of the thermometers is faulty or not in thermal contact with the sample stage Ask for assistance Similarly the heater may be in poor thermal contact with the sample The thermal cut out switch on the CCR is operating Is the set point too high Is the compressor on 8 Quick Guide to SECI It is important to check that SECI has the correct configuration for the cryostat sample stick and any period cards are set correctly before starting to collect data Once these are all right the following SECI commands are often useful begin Starts a run You will be asked to enter some details for the header file These need to be checked and confirmed at the end of the run end Finishes a run and saves the data abort Finishes a run and clears the data 0 Switches on the zero field compensation system and the other magnets off t 20 Switches on the calibration coils to provide a transverse
33. orrect exchange gas pressure 4 1 2 High and low temperature mode operation For temperatures above 4 2 K the cryostat can be operated with the gas flow valve under automatic control having set blue ht in the OpenGENIE window To achieve stable temperatures below 4 2 K it is necessary to control the gas flow valve manually Issue the command blue_1t in the OpenGENIE window and check that the gas flow control in the temperature window of SECI is showing Manual Connect the flow gauge attached to the Rootes pump frame to the exhaust and adjust the gas flow using SECI until the exhaust flow rate is around 450cm min The temperature should drop rapidly to below 2K Small adjustments to the flow rate may be needed to ensure a stable temperature Ensure that the temperature can be stabilized at the desired base temperature and disconnect the flow gauge to prevent it being clogged by oil Set points can be set in the conventional manner up to around 5K To return to higher temperature operation the blue ht command should be issued in OpenGENIE 4 1 3 Boost mode Boost mode is used to speed up temperature changes on warming above 30K It uses a second temperature controller and a heater on the sample stick to achieve this To use boost mode the SECI configuration must include boost and the OpenGENIE command boost must have been entered Boost mode does not increase cooling speed or change the operation of the cryostat below 30K 4 2 Oxford Inst
34. rs heater power P I D values and for scripts the required stability before a run begins These are selected from a table which can be viewed by choosing the TPAR blue menu entry You can edit the table and then do File Update and the new values will be used on the next SETTEMP command or temperature change in a script If you change configurations the default table for the sample environment equipment chosen is reloaded The header details can also be changed at any time before the run ends using the SETLABI CI p command which will ask for the new value SETLABEL S Sample name O Orientation T Temperature E Field RB RB number U Users C Comments In addition to the header various measured values such as the sample temperature and magnetic field are logged in the run file The following additional commands may be needed in special cases END IMMEDIATE Ends and saves the run without waiting for the period cycle to complete Use only if in period mode and the beam has gone off ABORT Ends the run and throws away the data Use with care BLUE HT Puts the Blue and Beast Variox cryostats into high temperature automatic gas valve control mode BLUE LT Puts the Blue and Beast Variox cryostats into low temperature manual gas valve control mode BOOST Uses the centre stick boost heater on cryostats with one CSHOW ALL
35. ruments Variox Beast SECI Configuration Names Beast_itc502 Beast_itc503 OpenGENIE Commands blue 1t Operation below 4 5K blue_ht Operation above 4 5K This is similar to the other Variox cryostat but with a larger helium bath and a different sample stick There is no boost function on this cryostat Range curve for Beast Variox Cryostat 18 09 09 T T T T T T T T o 10 F Relaxing asymmetry 4 4 AL rn 4 n 1 0 1 2 3 4 5 6 7 8 9 Number of 25 um Ti foils L A L 1 1 1 1 A 4 0 10 20 30 40 50 60 70 80 90 100 2 Range mg cm Figure 12 Range curve for Beast Variox Cryostat 4 2 1 Setting up and changing sample The cryostat will be craned into place by your local contact and the necessary electrical connections made The ISIS sample environment group will endeavour to maintain suitable cryogen levels during your experiments but it is important to check that it contains sufficient cryogens before leaving it unattended for any period Both helium and nitrogen levels should be monitored Removing a sample 1 Ensure the cryostat temperature is greater than 25 K at lower temperature any liquid helium that has been pulled through the capillary could boil rapidly too high a temperature could cause He gas to diffuse through the Mylar window into the outer vacuum space 2 Ensure the cryostat is connected to the He return panel or that a non return valve is fitted to the He outlet 7
36. ry line 13 4 Fill the sample space with He by turning black 3 way valve 8 downwards Wait until the flow meter on the He return line registers flow again 5 Remove the sample stick quickly but smoothly by undoing the Klein flange Cover the sample space with the blanking flange Return the 3 way valve 8 to its horizontal position 6 If the cryostat is to be left for a time without a sample present pump the sample volume via the 3 way valve 8 turned to upwards position using the rotary pump connected to the port above the valve Loading a sample 1 Ensure the sample stick is completely dry before inserting it into the cryostat 2 Ensure the cryostat is at about 25 K 3 Ensure the cryostat is connected to the He return panel or that a non return valve is fitted to the He outlet 7 4 Fill the sample space with He by turning the black 3 way valve 8 downwards Wait until the flow meter on the He return line registers flow again 5 Remove the blanking flange and introduce the sample stick quickly but smoothly 3 6 Pump the sample space via the 3 way valve 8 turned to its upwards position to 1 mbar the gauge on the top of the cryostat 10 reads the sample space pressure using the rotary pump 7 Turn the 3 way valve 8 to its downwards position to add He to the sample space and pump again to about 1 mbar 8 Add He to the sample space again and pump until the sample space gauge 10 reads 20 mbar This is the c
37. t the correct run Run 0 for the run in progress is only available after a new run has accumulated 5000 frames about 2 minutes if the beam is on at full current before then you get the previous one When a run ends the Run 0 file is not updated with the final data so for final analysis re load the data using its run number instead A sequence of very short runs might not update the Run O file at all Is the count rate too high in some detectors causing pile up distortion To monitor the run in progress select the DAE page in SECI and the Run Diagnostics 2 tab in the DAE VI that appears Enter 64 in the Number of Spectra box on the right and scroll up and down to see all the channels Is the magnetic field set correctly Check in SECI The beam may be badly focused and missing the sample Check the beamline and steering magnets The Kicker may have tripped or is still running but at reduced voltage and failed to veto the data 7 3 Temperatures If the cryostat will not cool when requested or starts to warm when it should be at a steady temperature e The cryostat has run out of helium In the case of the flow cryostat this means that the attached storage dewar is empty Was this due to repeated heating cooling cycles or because the flow valve was stuck open e The CCR compressor may have stopped There is a reset button If it happens again ask for assistance it may need refilling with more helium gas e The flow valve is
38. t they are facing in the correct direction shown by the Out labels painted on the coils The calibration coils are switched on using the SECI command t 20 which also sets 20G This is normally ideal for calibration but smaller fields can be set using commands such as setmag nn where nn is the desired field 2 5 3 Zero field compensation The zero field compensation coils work in active combination with a flux gate probe to ensure the field at the sample position is reduced as far as possible After calibration before each cycle the compensation process is controlled within SECI and can be viewed from the Magnets screen zerofield vi_ jc x File Edit View Project Operate Tools Window Help ep Long 3 jun 2010 Er Set zero Activity Update Interval stop KH Ze 2 Gro oam Power Supply Outputs Measured mG rectedmG Set pointmG Currents A Field from Others Ref Currents Currents Voltages L s801 oo oo o474 9O o o 474 0 470 7 299 T 448 o2 o0 1221 Go 1 221 1 217 5 957 y 1500 0 1 0 0 0 506 DO O 506 0 510 1 312 Magnets 20 0 Readout ae Field Now 0 0 EE 10 0 5 0 Status 0 0 p Ed 7 10 0 Reset Field Log ec Kaes Print E v MT 1023 lz Pap Debug Deployment Figure 8 Zero Field vi in active compensation mode To switch on the zero field compensation use the SECI co
39. the value is still stable The first entry can take control of and finish off a run that was in progress when the script starts in this case you would usually leave both temperature and field blank only selecting the number of million events at which the present run should finish For a linear scan of either temperature or field but not both enter the start end and step values Use only the Start value for a single run Scans can go up or down You can highlight an entry in the table then Insert At instead of Add to place the new entry just before it Delete removes the highlighted entry To estimate the counting time taken by a script enter the count rate in the box at the bottom left and MkScript will calculate the total counts in the script and the estimated time This does not include time for temperature or field changes which may be significant To update the estimated time after changing the rate add another entry or click somewhere in the table Finally save the script with Write and choose a filename for it To load a script that has been edited go to the OpenGENIE window and type load yourscriptname gcl using the filename you chose As a reminder the name is shown in the bottom border of the MuonScript window and you can also use Tab to auto complete the name Note that the script will not set or prompt for the sample name or any header entries other than the temperatures and fie
40. umber of muons entering the spectrometer in each bunch This is done using a variable slit just downstream of the electrostatic kicker that changes the size of the muon beam spot We can estimate the size of the muon spot by placing different sized discs of hematite on a silver backing plate and changing the slit positions Muons stopping in the hematite contribute a negligible amount to the asymmetry signal because they are rapidly depolarized whereas those stopping in the silver remain fully polarized The resulting asymmetry and rate curves are plotted against slit position in the graph below Asymmetry and Rate vs Slit Position for Blue Cryostat 120 100 lt lt i i o eS p 5 e n 80 S 7 7 O 4 D amp 60 amp lt S 8 2 bei c C C 40 Full asymmetry 21 6 e e 19mm Fe O disc on Ag 2 30mm Fe O disc on Ag o Rate MEv h 0 0 5 10 15 20 25 30 35 40 4 Slit Position Figure 5 Graph of asymmetry and rate vs slit position It is best to choose a fixed slit position for a given experiment to provide the most consistent results If small samples are being measured it may be desirable to close the slits below the position giving the optimum rate Otherwise it is best to open the slits to a level just below the point at which the data become distorted by the effects of detector deadtime recovery after counting a positron and buffer overflow in the electronics Such problems are evident in a drop in the count rates
41. value and switch off and disconnect the turbo pump Remove the cryostat and frame from the spectrometer 4 9 Long flow cryostat SECI Configuration Names Flow itc502 Flow_itc503 OpenGENIE Commands N A The operating range is 5 to 300 K Helium consumption is highest when operating at low temperature but a small flow is used even above room temperature Changing sample Ensure the cryostat is at 50 K or higher to prevent frozen air on the windows Connect the scroll pump to the sample space valve Connect a helium gas line to the small valve on the pump but do not open it yet Turn on the scroll pump pump out the line and then close off the pump Open the sample space valve on the cryostat Remove the clamp holding the stick into the cryostat the stick will still be held in place by vacuum Disconnect the thermometer cable from the stick Admit helium gas to the sample space to bring it to 1 atmosphere use the pressure gauges and small valve on the pump set Withdraw the sample stick Leave the O ring on the cryostat flange If the new sample is not ready yet put the blank plate on the cryostat and pump the sample space Insert the new sample stick Check the orientation the bolts on the cryostat flange can be used as a guide but note that the sample pit cage is not quite aligned with the beam field axis Tighten the clamp Pump the sample space with the scroll pump Flush with helium and pump again Admit 20mbar he
42. will assist with the sample mounting and cooling process 4 4 Oxford Instruments dilution fridge SECI Configuration Names OXDF low OXDF high OpenGENIE Commands N A This uses the Variox cryostat described in section 4 1 with a dilution fridge insert This allows temperatures from around 40 mK to 300 K Users need to arrive at least 24 hours before their beamtime to allow the sample to be mounted and cooled off beam before measurement The ISIS Sample Environment group and the local contact will assist with sample mounting and cooling 4 5 Sorption refrigerator SECI Configuration Names he3 OpenGENIE Commands N A The sorption refrigerator operates between 350 mK and 50 K Users need to arrive at least 24 hours before their beamtime to allow the sample to be mounted and cooled off beam before measurement The ISIS Sample Environment group and the local contact will assist with the sample mounting and cooling process Sample mounting 1 Mount sample onto the sample blade using the usual precautions for low temperatures and cold finger cryostat 2 Clean and re grease both sides of the cone seal then pump and rotate the sample can by 180 3 Puton the sorption cryostat tails and pump OVC Computer control 1 Change the configuration to the He3 Sorption Cryostat 2 Ensure the vi s in both tabs Muon Temp Panel and He3 are running Condensing the He3 cooling to base 1 Onthe Upper ITC5 Set
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