General Meeting Summary 8/22/19

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  • A request for 88 days for E12-13-010 (DVCS), E12-13-007 (SIDIS) and Hall A DVCS days from jeopardy, was submitted and approved
  • WACS experiment beam time request to be submitted later


  • J. Beaufait agreed to write the TOSP, needs help from collaboration to implement safety features - ODU will provide
  • Once TOSP complete can energize magnet in test lab and the ODU team can start testing


  • Demonstrated that background generations works
  • Showed that event generation works by comparing to Pavel's EM background calculations - here just count number of particles as function of angle and energy (particle flux)
  • Demonstrated that dose rate calculations works
  • Conversion to dose equivalent (in rem per beam electron at 1m) is done using the particle flux and conversion tables
  • Calculation of radiation dose (of interest for calorimeters and different from dose equivalent) is done using particle flux and assuming total absorption
  • A normalization error from the ERR presentation was fixed - related to the division by the mass of one crystal rather than the mass of one crystal column
  • New dose rates were calculated - challenging at small angles still
  • With current projections and assuming the 50krad limit for degradation/need for recovery, one would have to anneal about once a shift
  • 1 krad/hr at 6.3deg, 6m, 11 GeV, 11uA
  • 5 krad/hr at 7.9deg, 4m, 11 GeV, 50uA
  • Discussion of next steps
  • Estimate how radiation damage is distributed along the crystal - is there compensation between degradation due to low energy particles and shower collection
  • Have profile of shower - high energy
  • Profile of dose due to low energy particles expected to be different
  • Radiation damage mainly in first few centimeters of crystal - front area degrades faster than the rest
  • Shower collection may not be affected as much - in fact, overall looks like a small impact on resolution from existing plots, but good to verify
  • specific questions: How large non-uniformity of the radiation dose along the crystal? What is impact of the dose on the signal amplitude? What is energy deposition in the crystal? How large projected photon flux at PMT (due to background)? How large the shift of the base line of the signal (in GeV in 50 ns window)?
  • Isolate source of radiation - determine shielding as necessary
  • specific questions: Where is the source of radiation with the magnet present in the model? How the source distributed along beam line?


  • Discussion of Bogdan's presentation and suggestions
  • Interesting, but need to test and determine how difficult it would be to make this change (currently all components are optimized for the current scheme and already assembled)
  • next: meet with A. Somov and Fernando for further discussion and possible tests along with planned nonlinearity studies with LED and tuning of gains of current divider


  • Characterizations ongoing
  • Have 307 Crytur crystals (137/150 JLab, 55/55 CUA, 15/? OU, plus 100 JLab from 2018) - on schedule
  • SICCAS: 60/160 replacement crystals are being shipped back to vendor


  • Planning meetings with interested parties this fall