Difference between revisions of "Minutes-6-9-2011"
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== Production == | == 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. We will keep it there by tomorrow morning when we expect 10^-7 torrs. Bill | + | - 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. We will keep it there by tomorrow morning when we expect 10^-7 torrs. Bill: such under pressure will not damage the Rohacell. |
| + | - The good news is that the gas leakage of the first package was very low (undetectable) except at one place: one of the tube on the spacer ring. Mark Stevens was yesterday at Blue Crab explaining the procedure for gluing the gas tubing on a new spacer ring; the first one will be fixed too. | ||
| + | |||
| + | - We are working now on the second chamber set. The second wire frame was strung, glued, positions measured, then the wires were soldered. (After the meeting also the tensions were measured). Tomorrow the wires will be cut and the PCBs populated. Cathodes #3 and #4 are type 3 (as #1 and #2) and ready mechanically. After testing the modified tool we will glue the rigid-flexes. | ||
| + | |||
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Revision as of 23:24, 9 June 2011
June 2, 2011 FDC meeting
Agenda
- Production (Dave)
- First chamber assembly: HV problem
- Spacer ring: gas leakage
- Second set wire frame and cathodes
- Other
- Engineering (Bill)
- Vacuum chamber
- Ultrasonic cleaning
- Rigid-flex gluing tool
- Other
- Electronics (Fernando, Chris)
- PCB schematics update
- Other
- Chamber testing
- Wire Position Measurements
- 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. We will keep it there by tomorrow morning when we expect 10^-7 torrs. Bill: such under pressure will not damage the Rohacell.
- The good news is that the gas leakage of the first package was very low (undetectable) except at one place: one of the tube on the spacer ring. Mark Stevens was yesterday at Blue Crab explaining the procedure for gluing the gas tubing on a new spacer ring; the first one will be fixed too.
- We are working now on the second chamber set. The second wire frame was strung, glued, positions measured, then the wires were soldered. (After the meeting also the tensions were measured). Tomorrow the wires will be cut and the PCBs populated. Cathodes #3 and #4 are type 3 (as #1 and #2) and ready mechanically. After testing the modified tool we will glue the rigid-flexes.
