Meeting 1/27/22 - COMTRA

Schedule

Joe reviewed schedule again, beam test window is shorter at UITF, now from Jun 1 - Oct 31, see slide 4 media:220127_COMTRA.pptx

Joe proposed moving polarimeter test to non-dispersive "straight" section to avoid any energy dependent position jitter
Shaun showed UITF beam line, identified how we could remove single spool in 4' pass-through, leaving irradiation line intact
Joe is confirming this with Matt as first priority location
Riad showed model/pics of ceramic break & radiator we'd like to use, 6mm thick copper, 1" flat surface for beam, approved for 10 MeV/100uA with cooling
Riad will discuss with Eric if 6mm okay - then we move to fabricate second ceramic break & radiator

List of components needed to build two portable DAQ systems: media:ComptonTransPol_DAQ_PurchaseNeeds_2022Jan.xlsx
Discussed possibility of running local EPICS, to provide convenient controls to DAC, PS, Helicity Board....Riad will discuss/confirm path forward

Lakshmi will review the overall plan, when ready small group will meet to begin reviewing her questions about function and requirements

Greg has installed Geant4 and loaded files to run some of the examples
Greg would next like to learn to run and interpret output from the model Ben & Eric developed, then can add the radiator we'll use

I am in contact with the Alpha-Spectra company which was providing BGO crystals for a local project we had in Orsay. This is a US company which provides crystals with a guaranteed 8-9% resolution. At the time we were investigating for an order they were less expensive than Saint-Gobain and turned-out to be more performant (we performed dedicated measurements to test this).

They should be back to me shortly with information about availability of improved radiation hardness crystals as well as radiation limits of the crystals they are currently providing.

It should be noted that litterature about radiation aging of BGO crystals indicates that after a rapid loss of about 20% of transmission, the performance is kind of stable. Some experiments chose to first irradiate crystals to operate in that regime.

We may need tools to control the overall stability of the experimental signal... dedicated cosmic ray calibration run or light illumination... too early stage to provide a direction of answer, but this should be kept in mind.