xenon detector hardware liquid xenon group. 1 outline detector in 2008 operation in 2008 hardware...
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Xenon Detector HardwareXenon Detector Hardware
Liquid Xenon Group
2
OutlineOutline
• Detector in 2008
• Operation in 2008
• Hardware Upgrade and Schedule
• Summary
DetectorDetector
4
PMTs installationPMTs 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 LEDsNew LEDs
• Higher voltage with attenuation by coating LEDS
• Stable against instability of the input voltage
6
Problem in 2007 OperationProblem in 2007 Operation
Production procedure
•Fix pins in the holes and fill with silica
•Bake in argon atmosphere
•Cool down
Metal body
Glass insulator
Air
Xe
Wataru’s Design – Solution for 2007 run
No need to change connector
Replacement can be done quickly
Body made of insulator (not metal)
7
HV Feedthru ModificationHV Feedthru Modification
• Test of new feedthru– 1000 V applied on all
pins (48x6x4 pins)– One feedthru (48
pins) was tested at 1500V
• Successfully installed
welding
ceramic
Kyocera Ultra High Vacuum Feedthrough
New HV feedthru
8
New LN2 feedthru InstallationNew 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….!!!!!!!!!!
PMTCableChimneyRadiationSupportCu pipe?
?
Pipes
PMTs
Cables
•Refrigerator cooling power: 200W
9
Liquid circulation (Original Design)Liquid circulation (Original Design)• Circulate xenon in liquid phase
– Circulation pump• 100liter/h@3175rpm, p = 0.2MPa
– Molecular sieves• >24 g water absorption
• Used in 2007 run
Temperature Sensor
Purifier Cartridge
Molecular sieves, 13X 25g water
Freq. InverterOMRON
PT
10
Electronegative Impurity RemovalElectronegative Impurity Removal(Update in 2008 Run)(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 ModificationLiquid-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/CablesModification 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
175ns
97ns
NaI Electronics UpdateNaI Electronics Update
charge amp.charge amp. gn0261 gn0261 (hiroshima-(hiroshima-univ.)univ.)
inverting inverting amp.amp.and timing and timing filterfilter
APD
Light guide
9 amplifiers prepared, installed all on 17/Jun and checked all signal before connecting to splitter
rising time97ns for fast trigger
225ns (in 2007) ->175ns
replaced only amplifiers
energy outputby new setup
500ns
DRS
output for trigger
• output for energy measurement is also faster than that in 2007
14
New Scintillation CountersNew 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
CO
BR
ANaI
OperationOperation
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Gas/liquid systemGas/liquid system
Gas-phase purifier
Liquid-phase purifier
Detector1000L dewar
High pressureStorage
Gas line
Liquid line
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Scintillation Light YieldScintillation Light Yield
• In 2007 operation, there was an energy scale discrepancy btw alpha and gamma– Too small light yield from 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> / <Q/A> was found to be smaller than expectation and LP data
2007 Data
18
triplet= 22 ns
recomb= 45 ns
Waveforms (Shown in 2008 Review)Waveforms (Shown in 2008 Review)
= 21 ns
= 34 ns
! Careful treatment of electronics time constant is necessary
Xe
Xe X
e
Xe
Xe
Xe X
e
Xe
ee
ee
ee
A
Q
Q/A
Before purification 02.025.1/
/
AQ
AQ
was 1.93+/-0.02 in LP test
Electronegative impurity?
Oxygen??
2007 Data
19
Scintillation Light in 2008 RunScintillation 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
205 h
2/Dec
180 h
23/Nov
70 h
14/Nov
2007
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Why did it change in such way?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 MonitorLED 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 ShiftPMT 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 InvestigationHamamatsu Investigation
R9869 Gain Shift vs SKB
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
1.2
19 120
223
359
475
545
636
714
793
867
943
1032
1112
1258
1341
1436
1501
1634
1719
1783
1851
1902
1948
Serial No.
Gai
n Sh
ift
2
3
4
5
6
7
8
SKB
GainShift
SKB
Too much alkali ?????
24
Yet Another Way to Monitor the LightYet Another Way to Monitor the Light
• (Cosmic ray)
• Am-Be alpha source
Hardware UpgradeHardware Upgradeand Scheduleand Schedule
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Work during the shutdownWork 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
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Liquid filling scheduleLiquid filling schedule
• 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
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