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April 21, 2011 FDC meeting


  1. Production (Dave)
    • Cathode production, copper discoloration
    • Wire plane production
    • Other issues
  2. Electronics status (Fernando,Chris)
  3. Engineering status (Bill)
  4. Chamber testing (Lubomir)
  5. Other


Participants: Eugene, Dave, Chris, Simon, Beni, Glenn, and Lubomir. Relatively short meeting.


- We found discoloration spots on the first cathodes that were produced at Blue Crab. The spots are brown but have blue color at the periphery. There's one spot covering several thin traces close to a connector. Eugene explained the finding done with electron microscope by Olga: chlorine was found, so most likely this is copper chloride (brown) and copper chloride dihydrate (blue). We suspect chlorine is left from the etching procedure (have to verify that Allflex uses ferric chloride for etching). Then the effects we see is due to the wetting of the foils, this is needed for the alignment and gluing the panels together. So far we exclude the possibility that the copper reacts with the new packing paper. This is due to the fact that we see more spots on the first article foils than on the production foils. Still, we are waiting to hear from Andy Wu who will do independent analyses. Eugene, Lubomir and others agreed that Allflex should continue with the foil production.

- Dave: many problems this week. Still waiting for some signatures on some of the procedures. Yesterday there was a problem with the AC (due to transformer problem, second of this type) in the clean room; the humidity went up to 70%. It was fixed but Ron Bartek suspects a problem in the design. The power went out this morning, maybe related to Surry power plant shut down. It turned out according to Rusty Sprouse, we can't use the temporary light that we have outside of the clean room. The heater in the ultrasonic cleaner doesn't turn off; the ultrasonic cleaner was shipped back to the manufacturer for repair.

- The granite plate used for cathode flatness measurements was successfully moved to Blue Crab. Eugene suggested to check the flatness of at least one cathode, but it doesn't have to be the first one. We will do it later; don't want to spread our efforts to many projects when we are late with the first production chamber.

- After several improvements in the cutter (stronger blade, modifications in the blade holder, and very importantly cutting on wet plastic tape as proposed by Anatoly) it's not wobbling now. Second cathode foil was glued. Second PCB ring was glued. As of now, the highest priority is the wire frame lamination, so that we can continue with the stringing. Then, in parallel we will work also on the cathodes.


- Chris: discussing the price and details for the additional tinning of 50 rigid flexes, out of 100.


- Without Bill, Dave reported: parts for the strongback came from the machine shop. Other parts/tools are being machined in the shop: the jig table for the package assembly, the modified shoe for the rigid-flex gluing and other parts.

- Talking later with Bill: will work on the procedures then on designing a storage for the foils.

Chamber testing

- First measurements with the prototype in vertical position with 55Fe source were done; thanks to Beni for fixing the DAQ and Simon for getting back the source. The idea was to check the ratio of the charges on the two cathodes, that's why we used one wire as a trigger and two cathode cards connected to fADC125. The result: the measured charge ratio is in between the ratio for the standard position and the upside-down position, so the effect is most likely due to some frame deformation. Expect more measurements at different positions on the chamber and plots for the next meeting.

- Beni: expecting to get the differential pressure transducer, to be used to measure the pressure difference between different chamber layers.