Detectors for PREx Piotr Decowski Smith College Krishna

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

January 2008 test Statistics: 1 cm thick quartz�� Dustin’s analysis 0. 5 cm 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

January 2008 test Absolute determination of NPE: NPE * (1. 602*10 -19 C)*PMTGain = MPV(ch)*(50*10 -15 C/ch) Le. Croy 1881 M ADC NEEDED!

Measurement of PMT gain Anna Boehle, Diana Jaunzeikare, Smith College 21 f. C/ch

Measurement of PMT gain, cont PMT: Hamamatsu R 7723 Q (fused silica window) PMT # ZK 40033: Gain @ -2000 V = 4. 384*105

Results 1 cm thick quartz�� 0. 5 cm thick quartz�� Statistics: NPE = 22. 7 NPE = 11. 9 NPE (1 cm)/NPE(0. 5 cm) = 1. 90 Absolute gain: NPE = 18. 1 NPE = 10. 2 NPE (1 cm)/NPE(0. 5 cm) = 1. 77 (exp) Note: without pedestal width subtraction statistics gives NPE(1 cm) = 20. 3, and NPE(1 cm) = 9. 8

GEANT 4 Simulations Jon Wexler, UMass Cone mirror Tube mirror PMT cathode Quartz block

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

Simulations: results 1 cm thick quartz�� 0. 5 cm 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!)

Simulations: Al vs Alzak 1 cm thick quartz�� 0. 5 cm thick quartz�� NPE = 26. 6 NPE = 13. 9 NPE = 64. 5 NPE = 34. 0 Alzak Al Improvement: factor 2. 4 !

HRS focal plane Bob Michaels

Detector concept Top view LED 10 cm Optimize Quartz 0. 5 cm (0. 25 cm) thick Al mirror tube 2” PMT Expected ~20 PE per PMT/electron (~4 n. A @1 GHz) Two stacked 0. 25 cm thick detectors?

A_T Detector configuration Det 2 Det 1 e- beam

Conclusions and plan 1. Simulations are reproducing experimental data well. 2. We have tool to optimize geometry of new detectors 3. with larger quartz accommodating larger footprint of the Pb elastic peak. 3. Use of anodized aluminum instead of Alzak and PMTs with fused silica window significantly increases number of PE’s. Plan for nearest future: 1. 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. 2. Optimization of geometry of detectors with larger quartz blocks. 3. Construction of A_T detectors (similar to used in the January 2008 4. tests). 5. Construction of small plastic scintillator pads which will be mounted above the main detectors, and in counting mode will substitute S 0 detector.