Minutes-7-21-2011
July 21, 2011 FDC meeting
Agenda
- Production Construction Tracking (Dave)
- Status
- HV tests: results, testing procedures (Lubomir)
- Other: wire deadening, iron source
- Engineering update (Bill)
- Electronics update (Chris)
- Chamber testing at EEL126
- Tests with external tracking (Beni)
- Other
Minutes
Participants: Eugene, Bill, Dave, Chris, Beni, Simon, and Lubomir.
Production
- Dave (see the construction tracking): Continued with stringing wire frame#4. Wire frame#3 is waiting for soldering second phase component (Chris will do it together with Tina). Cell#5: one cathode ready, working on the second (type 2) cathode. Cell#6: working on the first cathode.
- Waiting for the chemicals for the wire deadening; probably will start testing the procedure beginning of next week. Bill: what is the wire diameter needed to deaden the wire? Lubomir: according to Garfield if we make sense wires 40um signal drops by factor of 40, for 60um - factor of 400, and for 80um -factor of 2,700. After some discussions, Bill will look what is the sagging effect of thickening the wires and Lubomir will estimate the suppression factor that we need.
- The PR for the iron source was submitted waiting for the RadCon signature, probably at the beginning of the next week.
- Investigating the sources of the high leakage currents; applied HV on the signal side of a wire frame without wires. In some of the measurements we found the current is too high because of the bad connection between the Cu tape (on which HV is applied) and the wire pads. The lowest current we got is ~10nA for one board when the capacitors are covered with Humiseal, and close to 0nA when capacitors were removed cleaned and then soldered without flux, latter done by Anatoly who put solder on the capacitors and pads, cleaned the flux and then solder the capacitors just by heating. According to Chris this is not a certified way for soldering because of possible oxyde layer.
- Conclusions for the HV problem: the capacitors itself are not the source of the leakage. Some small amount of flux found below some of the capacitors indicate that this might be a problem but this effect is reduced by covering it humiseal that actually penetrates also below the capacitors. The humiseal help also to cover possible sharp places on the capacitor plates that otherwise in gas would produce sparks. Lubomir proposed a procedure for testing the wire frames just before stringing. If all the leakage current of the caps is less than few tens nA the caps will be covered with humiseal, otherwise the caps showing big currents will be removed, the place cleaned and then put back.
