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Detectors for PREx

Detectors for PREx. Piotr Decowski, Smith College Krishna Kumar. UMass. Collaboration Meeting, April 17-18, 2009. Dustin’s analysis. Statistics:. January 2008 test. 0.5cm thick quartz. 1cm thick quartz. Pedestal width = 1.85. MPV = 25.48 GSigma = 5.65 Net width = 5.34 (21%)

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Detectors for PREx

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  1. Detectors for PREx Piotr Decowski, Smith College Krishna Kumar. UMass Collaboration Meeting, April 17-18, 2009

  2. Dustin’s analysis Statistics: January 2008 test 0.5cm thick quartz 1cm thick quartz Pedestal width = 1.85 MPV = 25.48 GSigma = 5.65 Net width = 5.34 (21%) Net RMS = 8.57 (34%) (5.34)2 = 28.5 MPV = 14.37 GSigma = 4.59 Net width = 4.20 (29%) Net RMS = 5.49 (38%) (4.20)2 = 17.64 NPE = 1/(.21)2 = 22.7 NPE = 1/(.29)2 = 11.9

  3. January 2008 test Absolute determination of NPE: NPE * (1.602*10-19 C)*PMTGain = MPV(ch)*(50*10-15C/ch) LeCroy 1881M ADC NEEDED!

  4. Measurement of PMT gainAnna Boehle, Diana Jaunzeikare, Smith College 21 fC/ch

  5. Measurement of PMT gain, cont PMT: Hamamatsu R7723Q (fused silica window) PMT # ZK40033: Gain @ -2000V = 4.384*105

  6. Results 1cm thick quartz 0.5cm thick quartz NPE = 11.9 Statistics: NPE = 22.7 NPE (1cm)/NPE(0.5cm) = 1.90 Absolute gain: NPE = 18.1 NPE = 10.2 NPE (1cm)/NPE(0.5cm) = 1.77 (exp) Note: without pedestal width subtraction statistics gives NPE(1cm) = 20.3, and NPE(1cm) = 9.8

  7. GEANT4 Simulations Jon Wexler, UMass Cone mirror Tube mirror PMT cathode Quartz block

  8. Simulations: photon energy range PMT QE: 380nm Alzak cut Standard PMT QE cut 185 nm Quartz cut 500 nm QE cut Alzak: reflectivity 93 - 98% Anodized Al reflectivity: 85 - 87%

  9. Simulations: results 1cm thick quartz 0.5cm thick quartz Sim: NPE = 26.6 NPE = 13.9 Stat: NPE = 22.7 NPE = 11.9 Gain: NPE = 18.1 NPE = 10.2 Simulations overestimate experimental results by ~ 30% (there is room for improvements!)

  10. Simulations: Al vs Alzak 1cm thick quartz 0.5cm thick quartz NPE = 26.6 NPE = 13.9 Alzak NPE = 64.5 NPE = 34.0 Al Improvement: factor 2.4 !

  11. HRS focal plane Bob Michaels

  12. Detector concept Top view LED 2” PMT Optimize 10 cm Optimize 2” PMT Expected ~20 PE per PMT/electron (~4nA @1GHz) Quartz 0.5cm (0.25cm) thick Al mirror tube Two stacked 0.25cm thick detectors?

  13. Detector configuration A_T Det Det 2 Det 1 e- beam e- beam

  14. Conclusions and plan Simulations are reproducing experimental data well. We have tool to optimize geometry of new detectors with larger quartz accommodating larger footprint of the Pb elastic peak. Use of anodized aluminum instead of Alzak and PMTs with fused silica window significantly increases number of PE’s. Plan for nearest future: Construction of two prototypes of detectors with existing quartz blocks to test PE enhancement due to Al mirrors. These detectors will be used at the beginning of the HAPEX run. Optimization of geometry of detectors with larger quartz blocks. Construction of A_T detectors (similar to used in the January 2008 tests). Construction of small plastic scintillator pads which will be mounted above the main detectors, and in counting mode will substitute S0 detector.

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