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Xenon Detector Hardware

Xenon Detector Hardware. Liquid Xenon Group. Outline. Detector in 2008 Operation in 2008 Hardware Upgrade and Schedule Summary. Detector. PMTs installation. All PMTs were taken away for check and reinstalled in the cryostat New LED on the outer side for better calib. of inner PMTs

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Xenon Detector Hardware

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  1. Xenon Detector Hardware Liquid Xenon Group

  2. Outline • Detector in 2008 • Operation in 2008 • Hardware Upgrade and Schedule • Summary

  3. Detector

  4. PMTs installation • All PMTs were taken away for check and reinstalled in the cryostat • New LED on the outer side for better calib. of inner PMTs • Wire alpha sources are at staggered positions • Better PMT calibration • Alpha sources (all) on walls were removed 25mm 31mm

  5. New LEDs • Higher voltage with attenuation by coating LEDS • Stable against instability of the input voltage

  6. Problem in 2007 Operation Wataru’s Design – Solution for 2007 run Air Metal body Glass insulator Xe • Production procedure • Fix pins in the holes and fill with silica • Bake in argon atmosphere • Cool down No need to change connector Replacement can be done quickly Body made of insulator (not metal)

  7. ceramic welding HV Feedthru Modification • Test of new feedthru • 1000 V applied on all pins (48x6x4 pins) • One feedthru (48 pins) was tested at 1500V • Successfully installed Kyocera Ultra High Vacuum Feedthrough New HV feedthru

  8. PMTs ? Cables Pipes New LN2 feedthru Installation • Pressure was slowly increasing under normal operating condition in 2007 runs • 6 new LN2 feedthru have been installed • Stainless steel pipes instead of Cu pipes • Pipes are precisely and strongly centered in order not to touch the wall • Bellows connection for the cooling pipes on the covers • 30-40W reduction of heat load was achieved • But … still pressure is slowly increasing…. !!!!!!!!!! • Refrigerator cooling power: 200W

  9. Temperature Sensor Liquid circulation (Original Design) Purifier Cartridge Molecular sieves, 13X 25g water Freq. Inverter OMRON • Circulate xenon in liquid phase • Circulation pump • 100liter/h@3175rpm, Dp = 0.2MPa • Molecular sieves • >24 g water absorption • Used in 2007 run PT

  10. Electronegative Impurity Removal(Update in 2008 Run) • O2 getter cartridge • Developed for LAr use at CERN • Mounted at the exit MEG liquid-phase purifier with by-pass valves

  11. Liquid-phase Purifier Modification • New purifier cartridge to remove water • Oxidization-reduction of Cu • Outside of the purifier cryostat • MS is replaced to new pellet • Particle filter has been installed

  12. Modification of Splitter-DRS Connections/Cables • GND line from splitter floating  grounding on DRS board • Copper tape + black tape DRS pedestal distribution before/after modification

  13. NaI Electronics Update 9 amplifiers prepared, installed all on 17/Jun and checked all signal before connecting to splitter • output for energy measurement is also faster than that in 2007 inverting amp.and timing filter charge amp. gn0261 (hiroshima-univ.) replaced only amplifiers rising time 97ns for fast trigger 225ns (in 2007) ->175ns energy outputby new setup output for trigger 97ns APD Light guide 500ns 175ns DRS

  14. New Scintillation Counters • Used for time calibration of LXe • Scintillator x 2 • 70mm x 70mm x 7.4mm • Fine mesh PMT x 4 • Hamamatsu H6152-70 • Pb converter COBRA NaI

  15. Operation

  16. Gas/liquid system Gas-phase purifier Gas line Liquid line High pressure Storage Detector 1000L dewar Liquid-phase purifier

  17. a Scintillation Light Yield • In 2007 operation, there was an energy scale discrepancy btw alpha and gamma • Too small light yield from g events ( < 1/2) • Purity seemed to be good because we observed • Improvement and plateau of light yield of both gammas and alphas • but <Q/A>g / <Q/A>a was found to be smaller than expectation and LP data 2007 Data

  18. g a e Xe Xe e e Xe Xe Waveforms (Shown in 2008 Review) • triplet= 22 ns • recomb= 45 ns tg = 34 ns ta = 21 ns ! Careful treatment of electronics time constant is necessary 2007 Data Before purification Q/A was 1.93+/-0.02 in LP test A Q Electronegative impurity? Oxygen??

  19. Scintillation Light in 2008 Run • Rapid increase at the beginning thanks to the liquid-phase purification • Removal of water/oxygen • LN2 cooling was necessary to help limited cooling power during purification • Increase (~14%) in summer by gaseous purification, however this was not significant • Large increase (46%!) in Oct-Dec after replacing the diaphragm of the gas-circulating pump 2007 205 h 2/Dec 180 h 23/Nov 70 h 14/Nov

  20. Why did it change in such way? • LN2 cooling pipe • In the cryostat • On the inner vessel wall and covers • Diaphragm • found to be broken in September

  21. LED Light as a Monitor • It is found that our LED system has very good stability. • Much more stable than our calibration precision • We can monitor the stability by a number of PMTs.

  22. PMT Gain Shift • Gain decrease in pi0 runs • PMT gain shift was found with muon beam on ( 2~3% ) • Time constant : short and long • CR peak during MEG run • LED run with normal muon beam • LED constant intensity with open/close beam blocker Beam on Beam off

  23. Hamamatsu Investigation Too much alkali ?????

  24. Yet Another Way to Monitor the Light • (Cosmic ray) • Am-Be alpha source

  25. Hardware Upgradeand Schedule

  26. Work during the shutdown • PMT/Cryostat • Open the downstream cryostat cover • Visual inspection of the cryostat • Take a few PMT to be sent back to Hamamatsu for further investigation of gain change • Installation of a new chimney cover with steel cooling pipe (previous one was made of Cu) • Replacement of the 1000L dewar heater • Recovery of xenon to the storage in Feb • Replacement of the heater and warm up frozen xenon in Mar • Liquefaction in April • Installation of new getter in March on the top of the cryostat • Installation of new Liquid Pump/Purifier in April • 1000 L/hour circulation expected • No electric noise

  27. Detector 6-19/April Evacuation 20-22/April pre-cooling 23-24/April cold gas alpha DAQ 25-26/April Liquid transfer 27/April-10/May Electronics test Purifier test 11/May- Purification and test 1000L dewar 26/Jan-27/Feb Recovery of xenon to the storage 2/Mar-6/Mar Recovery of the gas in the dewar 9/Mar-13/Mar Repair work of the heater 14/Mar-1/April Evacuation 2/April-22/April Liquefaction Complete removal of impurities Liquid filling schedule

  28. Summary • Successful running in 2008 • Remaining problems • Scintillation light yield (30% less than LP data) • Cooling power • Hardware upgrade/repair • New Getter purifier • New liquid pump • Replacement of the top chimney cover • LN2 cooling pipe: Cu  Stainless Steel • Replacement of the heater in the 1000L dewar • PMT gain shift investigation is in progress by Hamamatsu • Detector will be ready in the middle of May

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