CsI Compton Veto Detector for A low Mass WIMP Experiment

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CsI Compton Veto Detector for A low Mass WIMP
Experiment

• He Dao
• KPS_at_Jeju University
• 23 Oct 2004

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Content

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

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Status of WIMP detection

• The thresholds are
• a few keV
• Corresponding to
• the 10GeV mass
• limit measurable

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CRESST lowest threshold

• Cryogenic bolometer
• 262g Sapphire detector
• The lowest threshold
• gotten until now
• 500keV

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Our Idea

• Using low-threshold detector to find low-mass
  WIMP

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Our detector

• 5g Ge detector Shielding

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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)

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Energy Threshold of Detector

• Threshold?
• less than 100eV after PSD

PSD Parameter for every current shape
100eV
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The Aim of Our experiment

• Our estimated results
• Target mass 5g
• Counts rate 1
  count/keVkgday
• Threshold 100 eV
• Upgrade to 1kg Ge

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CsI Compton veto Detector
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CsI Crystal Structure

• Top
• ?150mm?50mm
• 29 degree slope from height 30mm
• ?76mm at top
• Bottom
• ?150mm?30mm

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CsI Crystal Structure

• Wall (6 parts)
• R75 mm
• r45 mm
• 5 L220 mm
• 1 L171 mm
• Outlet hole
• (see pic before)

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Photon Collection

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

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Compton Veto Function

• Shielding for high energy gamma.

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Primary Performance Test

• Place Tsinghua, China
• Time 16-18,Aug,2004
• Source Cs-137, Co-60
• Bias 12V
• HV -1000V
• Void inside

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Co-60 test result

• Resolution becomes better when the source moves
  form bottom to top.
• Peak moves since amplifier threshold adjusted.

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Cs-137 test result

• The result seems bad while source near the
  bottom. That is because of the energy which is
  not high enough.

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Comparison of two sources
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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.

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Plan

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

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• Thank you!