General Meeting Summary 10/5/17

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  • Date will be in the week of the Hall A/C meeting - exact choice will depend on NPS meeting agenda
  • Please send suggestions for talks by 19 October to
  • Note: Compact Photon Source Meeting will be together with NPS meeting


  • PMTs and HV Dividers
  • New PMTs were delivered with slightly different sockets - requires machining (or, if doesn't work get back to Hamamatsu)
  • 100 of the new PMTs were given to Hall D for assembly and tests
  • 1-2 new PMTs ready to be shipped to IPN-Orsay for assembly and tests
  • Assembly drawings of PMT+crystal module from HyCal are being collected - action item: get the original drawings from designers
  • similar to HMS calorimeter, but dimensions different and PbWO4 more fragile
  • found that in actual HyCal PMTs were NOT glued to crystal (that was only done for prototype modules)
  • OU got a quote for HV divider components (Advance Assembly) - checking the details, if all looks ok, will go ahead with the full procurement
  • PbWO4 Crystals
  • Discussion of visual inspection and dimension measurements with caliper of box#3 (10 crystals) of the first set of 160 SICCAS crystals
  • Visual inspection shows that about half of these crystals have bubbles and/or chipped edges - according to data the company sent, this does not affect optical properties
  • Action item: post the data the company sent
  • Discussion about alternative measurement methods to make nondestructive measurement of crystal dimensions that is safer (and potentially faster) than measuring with caliper
  • Note: current labor for measuring dimensions with calipers for 10 crystals (1 box) is 1 week
  • Best choice for purchasing a measurement system seems a dimension gage with tough probe
  • Probe has a sphere/ball tip at end, so can slide along crystal without visible scratching
  • Current plan is to measure transverse dimensions at three points along the crystal moving the probe
  • There is also an existing automated dimension measurement instrument in the machine shop owned by accelerator. For Hall A DVCS, this facility was available to the collaboration. This seems to have changed and now one cannot perform measurements oneself any longer.
  • What is the cost for using machine shop or a local company to make dimension measurement of 100s of crystals?
  • Initial crystal optical measurements performed at CUA for SICCAS 5031-5040 (box #3, first set of 160 pieces delivered in Sept 2017)
  • Initial results of subset of two suggest low light yield compared to requirement
  • Reference crystal results have been stable to 0.5 pe/MeV for more than a year
  • NPS magnet
  • All still seems on schedule for yoke and main coil delivery later this year
  • Frame
  • Design work ongoing including prototype module design (PMTs will not be glued to crystal)
  • Evaluation of specs for LED curing system
  • New graduate student implementing geometry in simulation to study effect of material