View source for Tracking Meeting Jan 17 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=

* (David) - upcoming reviews 
* (Asar) - more cosmic data-taking
* (James, Jaydeep) - SBU GEMs
* (Rakitha) - TS first production module results
* (Chandika) - TS interference issues

=Attendance=
Rakitha, Valdimir, Shashini, David, Klaus, Chandan, Asar, Chandika, James, Jaydeep

=Minutes=
#(David) Ask for slides for upcoming reviews (Director's review Feb. 25-27 and DOE/IPR review Mar. 25-27) Need draft slides for dry run on Tue. Jan. 28. Asar will provide efficiency scans, ADC plots, and 2D hit maps from cosmic data (not track-based) and Chandan will provide initial 2D-plots from tracking analysis. Will also ask for assembly photos from UVa and SBU.
# (Asar, Chandan) Holly has moved her GEMs out of the TestLab GEM room and into Hall C; so, we can now use the TestLab room entirely for MOLLER GEM work. David will email UVa to request that assembled production modules be brought to JLab so we can have three MOLLER production GEMs in the cosmic stand for good tracking data-taking.
# (James) Have received from CERN all 42 GEM foils needed for the 14 SBU GEMs, and frames and honeycombs enough to make 5 modules. Still waiting on the readout cards - estimated to receive 5 of these by end of the month. However, initial Q/A testing showed problems with many of the soldered resistors on the GEM foils. Every foil has at least one problem. Problem is only with the 5 MOhm protection resistors (not the foils with the 500 kOhm resistors). While the resistors have correct resistance, there is open circuit
between the traces they span for a large fraction of them - every one of the 28 foils which require the 5 MOhms have at least one bad connection. However, SBU cannot re-solder connection without contaminating the clean room they are using for GEM assembly. However, need to have these connected for the leakage current tests in individual foils. Discussion - send back to CERN for resolder? Alternative decided on after discussion:  use an external Cu strip to short all the traces together, and then use single external 5MOhm protection resistor (in series with HV supply) for leakage tests, since the SBU protocol gangs all the channels together anyway. Then, once foils are accepted based on leakage studies, assemble GEM and re-solder faulty resistors outside of clean room. UVa adds these resistors after assembly in their process - 
James to contact Huang for advice. Need need to send foils back to Rui at CERN.
# (Rakitha) Cosmic results from 1st production module disappointing/confusing. Efficiencies (for > 1 pe) are low, averaging around only 90%, or when dividing mapped area into 9 sectors, average only 85%, with
some regions at only 73%. Contrast with final prototype which had same scintillator geometry, which had 99.5% efficiency. Why? Final prototype used Kurary fibres borrowed from JLab, prod. module used newer fibres direct from company. But, compared cosmic hit efficiency between the two batches of fibers using identical setup and verified new fibers are good as old batch. Check PMT coupling to the fibers and verified it is properly coupled using optical grease. However, in production module have more and tighter bends on fibres than in final prototype. Tried tests in which varied bend angle using the initial 2-groove
prototype. See drop in relative efficiency (in that case) of 9-10% when go from no-bend to 10 cm radius bend in fibre. However, David comments that ADC spectra from production module don't appear consistent with low PEs - see big gap between lower edge of ADC spectrum and the pedestal. Also, don't see that the small change in ADC (mean-pedestal) value with location in TS is consistent with the apparent drop in efficiency. Maybe the low efficiency is not entirely real? Fake triggers? Will try raising thresholds on cosmic paddles to reduce possibility of fake triggers. Also, need to understand ADC spectra in terms of #PEs. Also, don't understand the apparent differential non-linearity in the time spectra seen (using a CAEN 1720 (250 MHz) digitizer).
# (Chandika) Found interferences between new TS design and the TS/GEM holder frame. David, Chandika, Rakitha, Lasitha will meet Monday to see if there is a work around in how/where the PT is mounted that would a) avoid the interference and b) reduce number of fibre bends to avoid loss of PEs.