General Meeting Summary 3/22/18

ENERGY RESOLUTION SIMULATION UPDATE

• 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

TCS BACKGROUND STUDIES

• 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 PROTOTYPE

• 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

OTHER UPDATES

• 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

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