Xenon Detector

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Xenon Detector

• Xenon Detector Group

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Contents

• Construction Status
• Cryostat
• PMT mounts
• PMT
• Pisa PMT test
• PSI PMT test
• Trouble report
• Neutron background at PiE5
• Schedule

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Construction Status

• Cryostat
• PMT mounts

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Cryostat Construction

• Construction at SIMIC http//www.simic.it
• Stainless steel raw material, sheets, tubes,
  flanges etc. are ready at SIMIC
• Several design modifications
• Feedthru mounting, cover handling, platform
  extension, SIMIC request etc.

Main flanges (not machined yet)
Flange for central chimney
Covers are machined
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Examples of modification
Newly added for mounting feedthrus

• Counter weight to install inner vessel covers

Feedthru flange
?
Counter Weight
Inner Vessel Flange
Inner Cover
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Cryostat Construction cont.

• Special materials are also at SIMIC
• G10 parts made in Pisa
• Cold and warm o-rings
• Windows material
• Thin foil
• The honeycomb is on going. The mold is in
  construction and should be ready in two weeks (as
  of 31/Jan). Only a week is necessary to make one.
• Bellows for chimneys are not ready yet.
• Various kinds of test are planned at SIMIC
• During construction Pressure test, Leak test
• After construction Leak test, Cold test

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Construction Schedule

• According to SIMIC schedule, the cryostat will be
  delivered to PSI at the beginning of May 2006.
• However the schedule is already behind
• We need to put additional pressure on them to
  respect their construction schedule.

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PMT mounts
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PMT Mounts Assembly Test
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PMT

• Pisa PMT test
• PSI PMT test
• PMT trouble report

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Pisa PMT test

• 298 PMTs tested, total of 650 tests
• 3PMTs/day, 2.5 hours for one test
• All data has been put into MySQL database

TEFLON stop
measured PMT
source
reference PMT
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Pisa PMT test results

• Gain _at_ 800 V (three times per test)
• Linearity all tested PMTs linear up to at least
  7 uA
• Quantum efficiency timing resolution
• The luminosity of Xe varied by a factor of 3
  along the tests
• ZA 1985 was tested once in two weeks to check
  stability / reproducibility
• QE of ZA1985 had an RMS of 5.6
• Independent of purity
• At least two tests for each PMT (different
  orientation)
• Error of QE measurement ? s(5.10.3)

Measured Gain
Bad
Anode Sensitivity by Hamamatsu
Xe Purity
ZA1985
3
different Xe purity
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PSI PMT test

• PMT test in liquid xenon by using LP cryostat.
• Up to 238 PMTs can be tested at once in two
  months
• We performed three tests
• Thanks to Students from Tokyo
• June August, August October, November
  December
• We tested not only newly delivered PMTs but also
  PMTs tested in Pisa, PMTs used in the previous
  test etc.
• Gain, QE, Linearity of PMT output measured.

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PSI PMT test result
Gain Curve

• Gain, linearity ? LED
• QE ? a sources on wires

1st 2nd 3rd total
New PMTs 188 184 144 516
PISA PSI 30 19 30 79
Re-test 20 35 64 119
1st test 2nd test 3rd test All data
QE
PMT linearity
a source changed
TC0106 (R9288)
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Comparison between Pisa and PSI tests
PSI 1st

• 20-30 PMTs tested in Pisa were tested in each
  test at PSI
• Discrepancy between Pisa and PSI tests
• LP wire sources
• Po (produced in Genova), 1st test
• Am (produced by SORAD), 2nd 3rd tests
• Gas data OK

PSI 2nd
PSI 1st
SORAD Am source
PSI 2nd
Gas
Liquid
PSI 3rd
Am over gold
data
simulation
clipping
100µm
50µm thick gold plate
tungsten wire
200µm
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PMT Trouble

• About 8 PMTs delivered in April-July 2005 have
  undergone vacuum break at the window edge.
• HPK investigated this problem and found
• Misalignment of the window during construction
• Insufficient treatment to remove HCl after
  heat-sealing

HCl
Electron Probe Micro Analyzer
Silica
Metal Tube
Al
Good
Vacuum break
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PMT trouble cont.

• Silica window is mounted by Al heat-sealing on
  the metal tube.
• No guiding tool to keep the window horizontal.
• Bad PMTs have larger window tilt (gt0.3 mm).
• Cleaning using warm HCl liquid.
• Washing with only water after this cleaning
  process
• Cylinder guide for heat sealing
• Keep the window horizontal
• Ultra-sonic cleaning with pure water after heat
  sealing and washing with HCl
• Complete removal of HCl
• High temp high humidity test (40oC, 93, 96h)
• 8 PMTs with cleaning ? no leak
• 2 PMTs without cleaning ? leak in one PMT
• This treatment seems to be effective.

Al heat sealing
Silica Window
Metal tube
Metal tube
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PMT trouble summary

• About 8 of delivered PMTs suffered from vacuum
  break.
• Hamamatsu investigated the problem and found that
  this was caused by remaining HCl that could not
  be removed due to window tilt.
• They introduced in their production
• Guiding tool
• Ultra-sonic cleaning after HCl wash
• They will deliver gt 150PMTs soon for replacement
  and spares. Those will be tested in PSI (4th LP
  test) and Pisa.
• We should not use PMTs with very large tilt (d gt
  0.350.4mm).
• This new PMT selection criteria is expected to
  suppress the problem during detector operation.

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Neutron background at PiE5
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Neutron Background Measurement

• Measurements of neutron flux and energy spectrum
  in the pE5 area
• Evaluation of the effects on the detector
• Setup
• NaI detector (4 inch x 4inch)
• Bonner sphere system with a 3He detector
• Two measurements
• Aug/2004 (w/o BTS)
• Dec/2005 (w/ BTS)

B
m
A

NaI surrounded by Lead walls
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Neutron Background (preliminary)

• 1.8mA proton current, 1.2x108 m/s
• Location A (by Bonner Sphere in Dec/2005)
• Thermal neutron flux 1-1.2 n/s/cm2
• Total neutron flux 4-4.5n/s/cm2
• Consistent with Aug/2004 measurement
• Location B (by Bonner Sphere in Dec/2005)
• Thermal neutron flux 3.7-5.4 n/s/cm2
• Total neutron flux 10-10.5 n/s/cm2
• NaI activation (128I activation) method (Location
  B)
• Thermal neutron flux 1.8/-0.3 n/s/cm2
• A bit lower but compatible with a factor of 1.5
• Nonthermal neutron flux 10 n/s/cm2
• Large uncertainty. Good agreement with He3
  measurements
• PMT background current due to neutron
• IPMT lt 1mA
• PMT response is linear far above this level
• No need of neutron shielding

PRELIMINARY
Time
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Schedule