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CsI Compton Veto Detector for A low Mass WIMP Experiment

CsI Compton Veto Detector for A low Mass WIMP Experiment. He Dao KPS@Jeju University 23 Oct 2004. Content. Introduction of our low mass wimp experiment Structure of CsI detector Some test and conclusion plan. Status of WIMP detection. The thresholds are a few keV

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CsI Compton Veto Detector for A low Mass WIMP Experiment

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  1. CsI Compton Veto Detector for A low Mass WIMP Experiment He Dao KPS@Jeju University 23 Oct 2004

  2. Content • Introduction of our low mass wimp experiment • Structure of CsI detector • Some test and conclusion • plan

  3. Status of WIMP detection • The thresholds are a few keV • Corresponding to the ~10GeV mass limit measurable

  4. CRESST: lowest threshold • Cryogenic bolometer • 262g Sapphire detector • The lowest threshold gotten until now: 500keV

  5. Our Idea Using low-threshold detector to “find” low-mass WIMP

  6. Our detector • 5g Ge detector Shielding

  7. Background Control • Cosmic Ray: Underground lab • Material background: purest material: Ge • Other particles: Multi-layer shielding: Pb, Cu, CsI veto detector PSD(Pulse Shape discrimination)

  8. Energy Threshold of Detector • Threshold? less than 100eV after PSD PSD Parameter: for every current shape 100eV

  9. The Aim of Our experiment Our estimated results: Target mass: 5g Counts rate: 1 count/keV·kg·day Threshold: 100 eV Upgrade to 1kg Ge

  10. CsI Compton veto Detector

  11. CsI Crystal Structure • Top: • 150mm50mm • 29 degree slope from height 30mm • 76mm at top • Bottom: • 150mm30mm

  12. CsI Crystal Structure • Wall (6 parts): • R=75 mm; • r=45 mm • 5 L=220 mm; • 1 L=171 mm; • Outlet hole (see pic before)

  13. Photon Collection • PMT performance: • CR119, one, at the top of CsI crystal • low background, good stability • Minus HV: -1.5KV • Anode resistance : 10K • Current: < 1mA • Reflecting film covers all surface of crystal .

  14. Compton Veto Function Shielding for high energy gamma.

  15. Primary Performance Test • Place : Tsinghua, China • Time : 16-18,Aug,2004 • Source : Cs-137, Co-60 • Bias: 12V • HV: -1000V • Void inside

  16. Co-60 test result • Resolution becomes better when the source moves form bottom to top. • Peak moves since amplifier threshold adjusted.

  17. Cs-137 test result The result seems bad while source near the bottom. That is because of the energy which is not high enough.

  18. Comparison of two sources

  19. Test Conclusion • Photon collection efficiency Efficiency becomes worse while source moving from top to bottom because only one PMT is used, at top. • Ray Energy Higher energy ray can be detected more easily than lower one, which is good for high energy gamma ray shielding in this experiment.

  20. Plan • Now: • CsI detector was sent to Korea • Nov: • Installation in Y2L and advanced test • MC simulation • Dec: • Built up with HPGe detector

  21. Thank you!

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