General Meeting Summary 3/22/18

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  • Simulation details: calorimeter at 3m from a pointlike target source of electrons, which are spread out over the calorimeter surface
  • Based on previous studies:
  • A 1mm air gap increases the energy resolution by 1-1.5% - seems acceptable for physics
  • New: instead of air use carbon and look at energy resolution as function of function of distance between crystals
  • Energy resolution decreases more with the material than with air gap, impact is mainly on the constant term
  • Distance between crystals not as important as presence of material
  • A 1mm gap of carbon between crystals is mechanically feasible
  • Discussion about fitting PMT and its mu metal shielding in a slot determined by crystal transverse dimensions (20.5 mm) and carbon structure (1mm)
  • Current mu metal thickness is 0.3 mm - could be reduced to 0.1 mm, perhaps with additional box outside
  • PMT diameter tolerance is 0.5mm based on information from company (18.6mm) vs. a few measurements (19.1mm). ACTION ITEM: Measure ~20 PMTs to get an idea of the diameter variation/distribution


  • Goal is to determine the impact of bremsstrahlung background to TCS detector operation
  • Action Item: model photon spectrum and relate to electron intensity, obtain real photon flux


  • NPS 3x3 prototype is installed in Hall D and cosmic data have been taken - straight tracks going through one column in the center
  • Machinery for analysis has been setup and has been tested (single PE analysis etc.)
  • When beam available measure one point
  • Energy range might be extended by removing material, e.g. TRD, to access larger range of pair spectrometer (3-6 GeV)
  • Updates on mechanical engineering for 10x10 "prototype" (COMCAL)
  • Mechanically feasible to install in this location in Hall D
  • Time line for 10x10 frame construction is end of July/beginning of August
  • For 10x10 "prototype" and given the short time frame go ahead with HyCal design, but keep in mind modifications, e.g. carbon structure, to make ComCal similar to NPS prototype
  • ACTION ITEM: ask engineer if can accommodate later a carbon grid with 1mm crystal-to-crystal separation; figure out how to deal with shallow electron angles in Hall D
  • Discussion about gluing PMT to crystal
  • For Primex 1500 crystals, PMTs rarely failed, but question is how HV divider performs


  • Magnet: all components (coils, yoke) now at JLab
  • Crystals
  • Specifications table including COMCAL and FCAL now available
  • Based on discussions with PANDA, Crytur should be able to accommodate both theirs and NPS crystal productions
  • Communications with SICCAS about last procurement ongoing