Revision as of 17:59, 12 July 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. We can't find what was different in the production of the last two wire frames. On Wednesday we installed back the third cell but with the working wire frame #18, that was before 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 to clean it and if it's stable we will use it in the second cell. As for #27, the plan for now is to leave it as a spare and use one of the spare frames (#6) in the fourth package.

- Spare wire frame #6: Anatoly was able to remove the HV caps and clean the Humiseal (without using aceton); there's die in the Humiseal which makes it very easy to see it with UV light. Next, we will test the wire frame between the Lexan sheets, first, without HV caps. Since we are not sure if we can fix #27, Bill will ask "Vision Machine" for quotation of four g10 wire frames. If we need them, we have to submit PR before the end of July.

- Third package: 10 ground clips (first article) finally arrived and we tested them on the package. They have a bite of ~12.5mm and we asked for 11mm, that's why we have to bend them a little, but other than that they worked fine. Casey put already them on one cell and is looking for a way to bend them in a standard way, using a press. This is not a big deal and we decided to go ahead with the production of the rest of the clips, instead of waiting another month. Tina and Dave put the labels on all the pre-amps for the third package.

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