General Meeting Summary 9/14/17

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  • 160 SICCAS crystals arrived - 16 boxes with 10 crystals/box
  • All crystals are labeled
  • Visual inspection shows small scratches (< 1 mm) on surfaces, some crystals have features inside
  • discussion how to quantify effect of surface effects on crystal response
  • Started mechanical measurements, e.g. dimensions
  • Required dimensions are 2.05cm x 2.05 cm x 20.0 cm (+-50um tolerance on sides, +- 150 um for length)
  • Measured dimensions are 2.10cm x 2.10 cm wity 0.09 mm uncertainty using caliper - looking for better measurement instrumentation
  • Status of Crytur crystal production
  • Still working on meeting radiation resistance variation requirements
  • Most measurements performed at Giessen though for different geometry crystals
  • Some open questions on rectangular crystal quality - being investigated at CUA


  • Anticipated delivery dates for yoke is end of month (main coil is delayed until end of year)
  • Test plan discussion
  • Hall probe for tests identified and available
  • Information needed for initial test plan: space requirements and what measurements will be performed
  • need details of power needed and for what - initial discussions with Hall have started (Bogdan)


  • Need correct values for: crystals and dimensions, PMT dimensions, HV divider dimensions
  • Curing system
  • plan is to use 2 blue and 2 red LEDs at the four corners of the crystal
  • assume LED diameter 2mm, which is smaller by about a factor of two than what was previously used for NPS 3x3 prototype
  • assume LEDs will be placed at the back to avoid radiation damage even though placement may be less efficient for curing
  • Mechanical connection PMT to crystal
  • currently assume spring-based system similar to 3x3 NPS prototype, alternatively could try some structure from front
  • Note: Hycal design glued PMT to crystal, not very flexible
  • Nominal NPS design assumes optical connection PMT to crystal is with an organic scintillator (optical grease like Bicron 630)
  • Crystal dimensions and reflector
  • Nominal NPS design reflector is teflon, expected crystal-to-crystal variation in thickness is expected to be on order 20-50um, similar to the uncertainty in crystal dimensions
  • for frame, standard principle would be to compress entire crystal stack and temperature regulation, so thickness variation on that level may not be an issue
  • Electronic ports at back of PMT
  • Design assumes that all cables come outside the box on the top towards the back using rotatable channels - designer is working on the details and also eliminating remaining mechanical interference


  • Crystals - start characterization of 160 SICCAS crystals and record results,
  • Magnet - write test plan including space requirements and what measurements will be performed
  • Frame - continue design work and curing system studies, check dimensions of HV divider with OU, need input on mechanical interference and electronics connection at back from JLab designer, need a few R4125 PMTs with bases for testing
  • HV dividers - continue procurement of PMTs and divider components
  • NPS collaboration meeting - start thinking about dates and coordination with JLab meetings in 2018