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1 Xenon Detector Xenon Detector Group
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2/22 Contents Construction Status Cryostat PMT mounts PMT Pisa PMT test PSI PMT test Trouble report Neutron background at PiE5 Schedule
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3 Construction Status Cryostat PMT mounts
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4/22 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. Covers are machined Flange for central chimney Main flanges (not machined yet)
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5/22 Examples of modification Newly added for mounting feedthrus Feedthru flange ? Inner Cover Counter Weight Inner Vessel Flange Counter weight to install inner vessel covers
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6/22 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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7/22 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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8/22 PMT mounts
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9/22 PMT Mounts Assembly Test
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10 PMT Pisa PMT test PSI PMT test PMT trouble report
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11/22 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 source measured PMT reference PMT
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12/22 Gain @ 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 σ =(5.1±0.3) % Pisa PMT test results No zener with zener Anode Sensitivity by Hamamatsu Measured Gain different Xe purity ZA1985 ~Xe Purity Bad ~3
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13/22 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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14/22 1 st test 2 nd test 3 rd test All data PSI PMT test result Gain, linearity LED QE sources on wires TC0106 (R9288) Gain Curve QE PMT linearity 1st2nd3rdtotal New PMTs188184144516 PISA & PSI 30 19 30 79 Re-test 20 35 64119 source changed same position different position
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15/22 Comparison between Pisa and PSI tests PSI 1st PSI 2nd PSI 3rd 100μm 200μm 50μm thick gold plate tungsten wire clipping Am over gold 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), 1 st test Am (produced by SORAD), 2 nd & 3 rd tests Gas data OK SORAD Am source PSI 1 st PSI 2 nd Liquid Gas datasimulation
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16/22 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 Vacuum break Chlorine Al Silica Metal Tube HCl Good Vacuum break Electron Probe Micro Analyzer
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17/22 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 (>0.3 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 (40 o C, 93%, 96h) 8 PMTs with cleaning no leak 2 PMTs without cleaning leak in one PMT This treatment seems to be effective. d Silica Window Metal tube Al heat sealing Metal tube
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18/22 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 > 150PMTs soon for replacement and spares. Those will be tested in PSI (4 th LP test) and Pisa. We should not use PMTs with very large tilt (d > 0.35~0.4mm). This new PMT selection criteria is expected to suppress the problem during detector operation.
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19 Neutron background at PiE5
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20/22 Neutron Background Measurement Measurements of neutron flux and energy spectrum in the E5 area Evaluation of the effects on the detector Setup NaI detector (4 inch x 4inch) Bonner sphere system with a 3 He detector Two measurements Aug/2004 (w/o BTS) Dec/2005 (w/ BTS) ++ B A NaI surrounded by Lead walls
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21/22 Neutron Background (preliminary) 1.8mA proton current, 1.2x10 8 + /s Location A (by Bonner Sphere in Dec/2005) Thermal neutron flux: 1-1.2 n/s/cm 2 Total neutron flux: 4-4.5n/s/cm 2 Consistent with Aug/2004 measurement Location B (by Bonner Sphere in Dec/2005) Thermal neutron flux: 3.7-5.4 n/s/cm 2 Total neutron flux: 10-10.5 n/s/cm 2 NaI activation ( 128 I activation) method (Location B) Thermal neutron flux: 1.8+/-0.3 n/s/cm 2 A bit lower but compatible with a factor of 1.5 Nonthermal neutron flux: ~10 n/s/cm 2 Large uncertainty. Good agreement with He3 measurements PMT background current due to neutron IPMT < 1A PMT response is linear far above this level No need of neutron shielding PRELIMINARY Time
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22/22 Schedule
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