General Meeting Summary 9/14/17

CRYSTALS

• 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

MAGNET

• 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)

FRAME - DISCUSSION OF INITIAL FRAME DESIGN ASSEMBLY

• 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

ACTION ITEMS

• 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

NEXT MEETING: THURSDAY 5 OCTOBER at 9:00 AM (EDT)