August 11, 2011 FDC meeting
- Production Construction Tracking (Dave)
- Wire deadening
- Other: Humi-seal, silver epoxy overheating
- Engineering (Bill)
- Package flatness
- Electronics (Chris)
- Pre-amp card connectors
- Chamber testing at EEL126
- Cell#2 status
Participants: Bill, Dave, Chris, Beni, Simon, Glenn, and Lubomir.
- Dave (see link above): all wire frames for the first package were laminated. Wire plane #5 ( the first to go in the package) will be populated tomorrow by Chris, followed by putting Humi-seal on the caps, and then wire deadening. Techs are working also on cathodes for cell#6: cathode type 1 is ready and the foils for type 2 are being cut.
- Wire deadening of the first production chamber (wire plane #2) was successful. The thickness of one sample was measured by a microscope from Olympus company and they found it ~66 microns along one wire. The surface looked very good. We have permission to use the W&M microscope to check samples. Bill is going to look at different wires to make sure the tickness is the same.
- The chamber from 126 with cell#1 was moved to Blue Crab and the wire plane #1 was replaced with wire plane #2. All the cathode channels were tested with the testing card. We found that several daughter card connectors didn't make good contact at some channels. After re-connection (sometimes several) finally we got them working. One bad connection was found between the flex at the cathode (the first one of this kind!) and it was fixed after re-heating/pressing without changing the conductive tape. We found also on the top cathode at an area that was exposed directly to the AC blower in 126, that the silver epoxy got some brownish color. It turned out that 9 days ago after a thunderstorm overnight the AC in the EEL switched from cooling to heating and the temperature in the morning reached 95deg F. The AC was fixed by 10am. It is not clear if it was the heat or humidity that caused this discoloration. We will prototype it, but the resistivity at this place was still low.
- Bill wants to try on one end window to use scotch-weld for gluing the thick mylar, he is afraid of the bubbles that appeared somewhere on the end windows.
- Bill: We measured the flatness of the new (wire plane #2) package that had now the new strong-back mounted on one side. There is a significant improvement but we still see +/- 11/1000" variations and some of them coming from the hubs. Bill/Dave will do more measurements.
- We discussed whether we need to cut the new gusset rings. The first two were cut but it resulted in some flatness problems. The point is that the gusset ring is right against the end window mylar that has ~0.5 Ohms/square resistivity and the cut in case of magnet quenching, will not help. There were discussions with Fernando after the meeting and he will look again into this. Important point he made is that in case of high current the aluminum will evaporate preventing higher currents. But then the question is what will happen with the aluminized mylar.
- Chris: the daughter/pre-amp card connectors can be used 10,000 times according to the specifications. Working FDC4 cables.
- The new package (old cathodes, end widows and new wire plane #2) was moved to Blue Crab on Wednesday. The gas tightness is OK (as usual) and on the next day we were able to apply HV (1650/-200 with 90/10 Ar/CO2 ~300nA) on all the sectors except one (#4). It is not clear yet what is the problem there and the current is high between the field and sense wires: could be the Epolite again and then it would require more drying, or sense/field wires stuck together during transportation.