1. 1 Xenon Detector Xenon Detector Group

2. 2/22 Contents  Construction Status Cryostat PMT mounts  PMT Pisa PMT test PSI PMT test Trouble report  Neutron background at PiE5  Schedule

3. 3 Construction Status Cryostat PMT mounts

4. 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)

5. 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

6. 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

7. 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.

8. 8/22 PMT mounts

9. 9/22 PMT Mounts Assembly Test

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

11. 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

12. 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

13. 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.

14. 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

15. 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

16. 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

17. 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

18. 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.

19. 19 Neutron background at PiE5

20. 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

21. 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 < 1A PMT response is linear far above this level No need of neutron shielding PRELIMINARY Time

22. 22/22 Schedule