Minutes-7-12-2012

July 12, 2012 FDC meeting

Agenda

1. Production Construction Tracking (Dave)
   • Fourth package tests
   • Spare wire frames
   • Third package preparation
2. Engineering update (Bill)
   • Cooling system [1], [2]
3. Electronics update: PR for the spare PCBs, grounding, other (Chris, Nick)
4. Gas system update (Beni)
5. Test set-up in 126 (Beni)
6. Other

Minutes

Participants: Bill, Dave, Eugene, Nick, Simon, Vlad, and Lubomir

Production

- Results of the tests of the last three cells of the fourth package: top cell #1 (wire frame #18) working fine, cell #2 (wire frame #28) and cell #3 (wire frame #27) had a problem, high dark currents, about 400-500nA for frame #28 and 1100-1300nA for #27. Both cells held HV for a long time (3-4 days) and all channels are OK. Still, we were not comfortable with that and disassembled the three cells on Monday. It turned out that the HV caps on all wire frames were indeed replaced, just Anatoly didn't have record for #28. On Wednesday we installed the third cell with wire frame #18, that was on the top.

- From Monday till Wednesday we were testing #27 separately between the two Lexan sheets: the high current didn't change even after cleaning, or removing HV cap on the HV PCBs. There's no current through the field HV and looks like the current goes on the HV PCBs to ground. Most likely humidity plays a role here. We used a lamp for several hours to heat/dry the PCB; the current goes up by a factor of two almost immediately after turning it on. On Wednesday we gave up with #27 and started testing wire frame #28, the current there is much lower, ~400nA. The plan is to try clean it and if it's stable we will use it as