Minutes-6-9-2011

June 2, 2011 FDC meeting

Agenda

1. Production (Dave)
   • First chamber assembly: HV problem
   • Spacer ring: gas leakage
   • Second set wire frame and cathodes
   • Other
2. Engineering (Bill)
   • Vacuum chamber
   • Ultrasonic cleaning
   • Rigid-flex gluing tool
   • Other
3. Electronics (Fernando, Chris)
   • PCB schematics update
   • Other
4. Chamber testing
   • Wire Position Measurements
5. Other

Minutes

Participants: Eugene, Bill, Dave, Chris, Caleb, Beni, Simon, and Lubomir.

Production

- End of last week we assembled the first production chamber, run gas over the weekend, on Monday applied HV and was tripping (1uA threshold) at very low voltages: ~20-30V for sense wires and somewhat higher (~30V, one sector was at -500V for short time) for field wires. Then we found ~1-10MOhm between HV and ground and practically all the pads on the PCBs, even between opposite PCBs on the wire frame that have no electrical connection. The conclusion was: the wire frame got wet (most likely the Rohacell) when it was cleaned in the ultrasonic bath. We tried to dry it with a lamp and then with a heat gun; didn't work. Then today we put it a big vacuum chamber at the Test Lab to take the moisture out. The person servicing the vacuum chamber mentioned that it went down to 10^-4 torrs for ~2hours, much slower than usual (~20min) which indicates there was a lot of moisture there.