Transcript Xenon Detector Status

Xenon Detector Hardware
Liquid Xenon Group
Outline
• Detector in 2008
• Operation in 2008
• Hardware Upgrade and Schedule
• Summary
1
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
– Wire alpha sources are at
staggered positions
• Better PMT calibration
25mm
– Alpha sources (all) on walls were
removed
31mm
3
New LEDs
• Higher voltage with
attenuation by coating LEDS
• Stable against instability of
the input voltage
4
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)
5
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
ceramic
welding
Kyocera Ultra High Vacuum Feedthrough
New HV feedthru
6
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….
PMT
Cable
Chimney
Radiation
Support
Cu pipe
?
?
!!!!!!!!!!
PMTs
Cables
Pipes
•Refrigerator cooling power: 200W
7
Liquid circulation (Original Design)
•
Circulate xenon in liquid phase
– Circulation pump
• 100liter/h@3175rpm, Dp = 0.2MPa
– Molecular sieves
Purifier
Cartridge
Molecular
sieves, 13X
25g water
Freq. Inverter
OMRON
PT
• >24 g water absorption
•
Used in 2007 run
Temperature Sensor
8
Electronegative Impurity Removal
(Update in 2008 Run)
• O2 getter cartridge
– Developed for LAr use at CERN
– Mounted at the exit MEG liquidphase purifier with by-pass valves
9
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
10
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
11
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
energy output
by new setup
rising time
97ns for fast trigger
•
APD
Light guide
500ns
DRS
output for trigger
output for energy
measurement is also
faster than that in 2007
225ns (in 2007) ->175ns
175ns
12
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
13
Operation
Gas/liquid system
Gas-phase
purifier
Gas line
Liquid line
Detector
1000
L
dewa
r
Liquidphase
purifier
High
pressur
e
Storage
15
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
a
2007 Data
– 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
16
Waveforms (Shown in 2008 Review)
• triplet= 22 ns
• recomb= 45 ns
a = 21 ns
g = 34 ns
g
Xe
Xe
a
e
! Careful treatment of electronics time constant is necessary
Xe
e
Xe
e
Before purification
Q/A
2007 Data
 Q / A g
 Q / A a
 1.25  0.02
was 1.93+/-0.02 in LP test
A
Q
Electronegative impurity?
Oxygen??
17
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
180 h
205 h
23/Nov
2/Dec
70 h
14/Nov
18
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
19
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.
20
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
21
Hamamatsu Investigation
R9869 Gain Shift vs SKB
1.2
8
GainShift
1.15
SKB
7
1.1
6
5
SKB
1
0.95
4
0.9
3
0.85
1948
1902
1851
1783
1719
1634
1501
1436
1341
1258
1112
1032
943
867
793
714
636
545
475
359
223
2
120
0.8
19
Gain Shift
1.05
Serial No.
Too much alkali ?????
22
Yet Another Way to Monitor the Light
• (Cosmic ray)
• Am-Be alpha source
23
Hardware Upgrade
and Schedule
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
25
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
26
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