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PREx detector status report

PREx detector status report. Piotr Decowski Smith College. HRS focal plane. Keith Otis, UMass. Quartz stack. Thin quartz. Keith Otis, UMass. Requirements: Integrating Radiation hard (~1 GHz) Good resolution (<25%) Small size. Test bench for cosmic ray measurements. Cosmic muon

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PREx detector status report

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  1. PREx detector status report Piotr Decowski Smith College

  2. HRS focal plane Keith Otis, UMass

  3. Quartz stack Thin quartz Keith Otis, UMass

  4. Requirements: Integrating Radiation hard (~1 GHz) Good resolution (<25%) Small size

  5. Test bench for cosmic ray measurements Cosmic muon E>300 MeV quartz block stack Quartz blocks 5 cm Trigger scintillators Cherenkov light 5 blocks Number of Cherenkov photons 3 blocks 20 cm 300 MeV PMT 1 block Pb 20cm trigger scintillators Muon energy (GeV)

  6. Response of Hamamatsu R329-02 PMT to single photons at HV = +2000 V shutter LED 200 ns 1 kHz LED power pulse PMT output PMT 1:100 optical filter +2000 V ADC gate 29 channels 29 channels

  7. Cosmic muons - measurements 1 block 5cm*4cm*0.5cm 5 blocks Number of channels per PE = 29 Measurement Measurement Channel # Channel # Simulations Simulations # of photons # of photons “Factor of 4” puzzle: Nph in simulations = NPE in measurements Measurement Simulations reproduce well width of the experimental distributions Simulations Black dots: Distr. of events vs (channel / number of channels per PE) (meas.) Red dots: Distr. of events vs number of photons reaching PMT (simulations)

  8. Simulations Distributions of Cherenkov photons generated in quartz blocks of different thicknesses: Number of photons and RMS vs block thickness RMS N of photons RMS 39% RMS 11% 1cm block 15cm block Quartz block thickness (mm) Distribution of generated photons THINNER BETTER!

  9. Do we need scanners? Examples of scans from HAPPEX II: Scanners are very useful for precise monitoring of electron flux distribution at the detector face. Good knowledge of this distribution is important for determination of the average Q2 value (note that it is critical because of the small size of PREx detector) James Barber, UMass Momentum axis

  10. Scans parametrized Logarithmic distribution fitted with polynomial a0 a1 a2 a3 a4 Run number James Barber, UMass

  11. Plans for the nearest future: Optimization of quartz block size, and of light collection using cosmic muon setup Mechanical design and machining of detector prototype 3. Test of prototype using CEBAF electron beam (summer 2007?)

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