Xenon Detector

1. Xenon Detector Xenon Detector Group

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

3. Construction Status Cryostat PMT mounts

4. 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

5. Examples of modification Newly added for mounting feedthrus Counter weight to install inner vessel covers Feedthru flange ? Counter Weight Inner Vessel Flange Inner Cover

6. 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

7. 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.

8. PMT mounts

9. PMT Mounts Assembly Test

10. PMT Pisa PMT test PSI PMT test PMT trouble report

11. 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

12. No zener with zener Pisa PMT test results • 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) % Measured Gain Bad Anode Sensitivity by Hamamatsu ~Xe Purity ZA1985 ~3 different Xe purity

13. 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.

14. same position different position PSI PMT test result Gain Curve • Gain, linearity  LED • QE  a sources on wires QE 1st test 2nd test 3rd test All data PMT linearity a source changed TC0106 (R9288)

15. 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

16. Vacuum break Chlorine 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

17. d 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 (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

18. 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 (4th 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.

19. Neutron background at PiE5

20. 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

21. Neutron Background (preliminary) • 1.8mA proton current, 1.2x108m+/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 < 1mA • PMT response is linear far above this level • No need of neutron shielding PRELIMINARY Time

22. Schedule