Xenon Detector Hardware

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
Watarus 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
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
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
Liquid circulation (Original Design)
Purifier Cartridge Molecular sieves, 13X 25g water
Freq. Inverter OMRON

• Circulate xenon in liquid phase
• Circulation pump
• 100liter/h_at_3175rpm, Dp 0.2MPa
• Molecular sieves
• gt24 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
inverting amp.and timing filter
charge amp. gn0261 (hiroshima-univ.)
replaced only amplifiers
rising time 97ns for fast trigger 225ns
(in 2007) -gt175ns
energy outputby new setup
output for trigger
97ns

• output for energy measurement is also faster than
  that in 2007

APD
Light guide
175ns
500ns
DRS
14
New Scintillation Counters
COBRA
NaI

• 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

15
Operation
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Gas/liquid system
Gas-phase purifier
Gas line
Liquid line
High pressure Storage
Detector
1000L dewar
Liquid-phase purifier
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Scintillation Light Yield

• In 2007 operation, there was an energy scale
  discrepancy btw alpha and gamma
• Too small light yield from g events ( lt 1/2)
• Purity seemed to be good because we observed
• Improvement and plateau of light yield of both
  gammas and alphas
• but ltQ/Agtg / ltQ/Agta was found to be smaller
  than expectation and LP data

2007 Data
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Waveforms (Shown in 2008 Review)

• ?triplet 22 ns
• ?recomb 45 ns

ta 21 ns
tg 34 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
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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 ( 23
  )
• 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
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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

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Liquid 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

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