General Meeting Summary 2/22/18

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  • Magnet (Bogdan)
  • main coil arrived, yoke pieces ready to ship, next steps: assembly and testing
  • HV Bases (Julie)
  • received bases, tested some and found they perform well under HV
  • revised base design (by Fernando) will have connectors installed on the base, communicated with vendor about this modification - possible and adds ~$1500, action item: get information on revised base design from Fernando
  • testing of boards in progress, need to redo some tests with the modified bases
  • procurement of sockets in progress
  • Crystals (Vladimir, Tanja)
  • Characterization of SICCAS crystals continues, also including chemical composition analysis
  • Communication with CRYTUR on next crystal procurement ongoing
  • Prototype (3x3 matrix) being assembled for test of method in Hall D in March - installation at pair spectrometer, which would be used as trigger, expected electron rate 3-6 GeV, actual rate low: 300 Hz, energy resolution of pair spectrometer ~1%; Limitations of this prototype to determine crystal energy resolution: 1) small matrix, so have eight blocks on edge, 2) pair spectrometer resolution similar to expected crystal energy resolution
  • Frame - simulation of energy resolution to determine if inner frame feasible (Ho San, Carlos)
  • full GEANT4 simulation including all materials (crystals, reflectors, etc.) was developed
  • Results: 1) 1 GeV electron deposits energy over more than nine crystals, 2) control of relative calibration of crystals is important for energy resolution, 3) (Air) gap between crystals and miscalibration mostly affect the constant term and constant term increases linearly with gap size
  • Based on Jan 2018 collaboration meeting, inner frame structure adds 1-2mm carbon between crystals - is impact on resolution acceptable?
  • Overall, having material between crystals seems ok, but preferably at most 1mm (effect ~10%) - also have to check for other effects like miscalibration, effective acceptance
  • Miscalibration: 3% seems doable, 1% is challenging
  • Next steps:
  • Simulation with 0.5-1mm carbon between crystals - check impact on constant term
  • Check acceptance
  • Check on possible optimizations of grid, i.e., can one group crystals into 4x4, 3x3 cells or similar - need to check with engineer what is allowed
  • Number of crystals to work with is: 30 x 36 - final details will depend on possible grouping


  • Backward angle physics with NPS (Bill)
  • Physics idea is interesting, need to figure out the required size of the calorimeter, location etc.
  • TCS (Marie, Vardan)
  • Working on balancing physics impact and statistics, e.g. optimal angles
  • To establish a baseline for angular acceptance, can assume the old UVa target configuration, but keep in mind that it is optimized for longitudinal polarization
  • further updates on background simulations next meeting