Tracking Meeting Jan 31 2025 2:30PM ET
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Zoom link: Please contact David Armstrong for meeting coordinates, or check with the MOLLER meeting calendar.
Agenda
- (Rakitha) - TS first production module results
- (David) - upcoming review
- (James) - [1] Measurement of pedestals from new readouts
- (brynna) - [2] SBU GEMs
- (Huong, Nilanga) - UVA GEMs
- (Chandika) - Rotator
Attendance
Vlad, David, Rakitha, Lasitha, James, Nilanga, Shashini, brynna, Chandan, Jaydeep, Huong
Minutes
- Trigger Scintillator/Rotator interference (David) - Lasitha has a new CAD design of TS/PMT connection that avoids mechanical interference, Chandika confirms. This has the PMTs emerging in radial direction, and will stick out a bit from the GEM holder, but that causes no new problems. Need to detail how PMT is held by GEM holder (not by TS frame).
- Trigger Scintillator tests (Rakitha) - after suggestions from last meeting, have increased thresholds on the cosmic paddles (to reduce spurious triggers) and retested the first production TS, with no other changes to the scintillator or its electronics. Now get 99.6% efficiency, uniform over TS. ADC spectrum looks reasonable, well-separated from pedestal. Conclusion - earlier low efficiency results were not correct due to fake triggers. Still probably want to minimize WLS bending, which is an advantage of the new mechanical design. The 1PE level is defined as about 20 counts above pedestal, rough estimate > 5 PEs for almost every event. Still don't fully understand timing spectrum (data taken using CAEN V1720 digitizer, 250 MHz clock (4 ns time bins) - sigma appears to be of order 5 ns, but spectrum has odd structure. Will study in more detail. Need to measure TS-paddle deltaT, rather than raw TS timing.
- UVa GEMs (Nilanga, Huons). Waiting for readout foils. Huong will deliver production module 2 to Asar to add to cosmic stand. Should UVa embark on assembling the 4 Polarimeter GEMs (have all the parts already) while waiting for readout foils? Yes, we agree that makes sense. So, assembly of the next Tracking GEMs at UVa will start after the polarimeter GEMs
are complete.
- SBU GEMs (brynna) - of the GEM foils with the 5 MOhm HV protection resistors with soldering issues, 18 were sent back to CERN to have them repair the connections. These were the foils with the most problems. 10 were kept, these were ones with fewer problems (1 or 2 connections per foil). Used Cu tape to short together the HV lines for HV leakage tests (with single 5 MOhm in series with power supply). First production module well underway - all 3 GEM foils HV tested, stretched and framed, RO board glued to honeycomb. Small question on nomenclature: SBU labels the three foils per chamber as A,B,C, with A being cathode side, B the middle, and C the readout side foil. More standard nomenclature is 1,2,3. Huong argues to switch to 1,2,3 for consistency with JLab and other group's practice (despite possible confusion between number of completed modules). Also - Readout foil precision pin holes are misaligned by about 0.3mm (Readout honeycomb precision
pin holes are fine) - Need to cut away excess to allow pin to go in. Decide this is not a real problem.
- SBU pedestals (James) - looking at channels with noisy pedestals, don't understand the pattern - doesn't seem to be the ones that are supposed to be floating. Is the readout board correct? Visually it appears to have the right pattern of traces. Is it software? Will investigate.
