General Meeting Summary 10/5/17

NPS SUBSYSTEM UPDATES

• 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

NPS COLLABORATION MEETING - JANUARY 2017

• 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 hornt@cua.edu

• Note: Compact Photon Source Meeting will be together with NPS meeting

NEXT MEETING: THUR 2 NOVEMBER at 9:00 AM (EST)