Minutes-9-22-2011
September 22, 2011 FDC meeting
Contents
Agenda
- Production Construction Tracking (Dave)
- Status
- First package tests (Lubomir)
- Engineering update (Bill)
- Electronics update (Chris)
- Chamber testing at EEL126 (Beni)
- Other: latest pictures of the package
Minutes
Participants: Eugene, Bill, Dave, Chris, Simon, Beni, Vladimir, Mark, and Lubomir. Vladimir is a new graduate student from MePhi Moscow.
Production
- Dave: started checking the continuity before taking the frame out of the stringing table: on the wire frame for cell#5 (that was just finished) one broken wire was found and was fixed today. Epoxy will cure overnight and tomorrow we will put on the stringing table the wire frame for cell#3 to fix one wire there too. Wire frame for cell#4 is ready, just needs last cleaning. On the last cathode (for the first package) the rigid-flexes were glued to the cathodes. Next, they will be tested with a generator and then the daughter cards glued.
- We discussed the reason for these broken wires, so far we had always one broken wire per plane. On the last one found on the frame for cell#5, we looked with a microscope. The wire was broken at the end of the epoxy right where it touches the soldering pad. The wire tip was bent at ~90 deg at this place somehow. It was not clear if the tip was inside or outside of the epoxy. The wire was checked by doing tension measurements on it. The only operation that happened later was cutting the wires and then doing the continuity measurements. One explanation could be a cold solder and then the wire brakes when twisting it. Dave suggested also that if the wire is above the PCB it may not be fully covered with epoxy and is easily breakable a that point.
- End of last week we put three cells in the package after replacing two wires in the second cell and changing all the O-rings. The first three cells were tested channel by channel by Vladimir. All were OK except no signal on one wire channel in the new third cell, most likely broken wire. We found again gas leakage in about the same area as with the two cells. The amount of leakage was about the same (bubbling above 80-100 ccpm) as with the two cells, indicating that the problem is in the second cell. Bill suspects it is the seam on the wire frame between the PCBs that may have been somehow damaged during the installation. To fix the broken wire and look at the leakage place we decided to unstacked the package down to the second wire frame. After finding the broken wire on the frame that is on the stringing table we decided to continue with this tomorrow.
Engineering
Electronics
- Chris is in vacation; will work on the board that will bring the signals from the daughter cards outside for testing. While testing the resistors on the PCB's, Anatoly found that some percentage (~5-10%) of the resistors have lower values by 10-30%. These are current limiting resistor, but still Lubomir will discuss with Fernando if these need to be replaced.
Chamber testing at 126
- Beni started rearranging the space at 126. He swapped the electronics and the gas racks and added another rack with a second VXS crate. Now there's enough space around the racks.
Other
- For the Lehman review next month Eugene needs new results from the production chambers. Beni explained his results about the chamber efficiency for the second cell. Lubomir will also prepare some plots from the test of the second cell using fAD125. As for the first production package, the plan is to have it ready before the review but most likely by that time still there will be no results from the tests with the DAQ.
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