JEF meeting, February 12, 2021
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Meeting time and location= 8:30 am EST (JLab time) Bluejeans only
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Agenda
- SICCAS crystals
- Test of the active base
- COMCAL tests, TAC running, etc.
- Data analysis
- Simulations
Minutes
Attendees: Igal,Zisis,Phil,Sasha,Jared,Arsak,Tim B.,Tim W.,Liping,Jane,S.T.
- Attempts to communicate with our contact at SICCAS have failed
- Still expecting a batch from SICCAS: wait for 1-2 weeks while keep trying to contact the company
- Have money to spend on more crystals -- switch to CRYTUR?
- Sasha reported on linearity studies of amplifier used in redesigned PMT base
- During PrimeX run observed nonlinear behavior that was reduced when reduced gain and increased HV
- Bypassed the amplifier -> good performance
- Beam tests: used 24x amplifier: very nonlinear!
- Vlad P. worked on redesign: resistor changes to increase voltage on first dynode, addition of amplifier circuitry
- Sasha used HP pulse generator to mimic current source, studied amplifier with ~2.3x gain
- Gain drops off by ~10% below 0.5 V signal size, but stable at ~1-2% level above 0.5 V
- Important because central block gets most of energy in the shower (~80%)
- Linearity depends on HV, better linearity at higher divider currents
- Nominal HV=900 V
- Gain drops off by ~10% below 0.5 V signal size, but stable at ~1-2% level above 0.5 V
- Ideas to improve base design include using separate power supply for amplifier, or use external amplifier?
- Expect only need amplifier for inner ring of insert
- Expect 3x-6x gain at most
- Plan is for URegina and UNCW to help out with effort
- URegina can make boards or modify existing amplifiers, asked us to send 1-2 PMTs
- During PrimeX run observed nonlinear behavior that was reduced when reduced gain and increased HV
- Working on CCAL refurbishment
- Do not need 24x amplifier
- Use no amplifier?
- Middle ground: 3x amplifier with dip switch to disable
- Working on light monitoring system: Josh polishing new fibers
- Will get help from Tim W.'s group for module fabrication
- Igal working on 2γ mass distributions -> dark scalar search
- π0 is huge background: limits search to m(2γ)<90 MeV?
- Major sources of background: η→3π0 and π0π0 production
- Thinking of backing off using reaction filter to get finer control in analysis
- Current MC model for π0π0 background does not agree with data
- MC distributions also not smooth, have strange peaking behavior where no peaks are expected
- S.T. working on more realistic generator
- Also could extract shape from real data
- Thinking of switching to π+π- and π0π0 above 2 pion threshold
