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August 5, 2010 FDC meeting

Tentative Agenda

  1. Production
    • 727 B.C. status
    • equipment/materials needed for the production Casey's list
  2. Electronics: update (Fernando) doc1567
  3. Engineering
    • Cathode foil: flex soldering/gluing, procurement status (Roger) [3M conductive film]
    • Mylar window thickness
    • Wire stringing update (Bill)
  4. Full-scale prototype tests [FDC Log Book, pages 509-512]
    • oxygen contamination measurements (Beni)
    • cosmic test update (Beni)
    • wire resolution results
  5. Other: FDC paper


Participants: Eugene, Fernando, David, Glenn, Bill, Roger, Casey, Mark, Chuck, Beni, Simon, and Lubomir.

We welcomed the new FDC construction coordinator, David Butler.


- Bill: there will be a delay with the clean room construction, because some of the specifications (like +/-2% humidity control) were not realistic, which delays the bidding process. Eugene: the leading time is about 3 months, so expect it ready by December, although they will try to speed up the construction.

- Casey created a list of equipment and materials needed for the production. Everybody is encouraged to look at the link above. We discussed what type of microscope we need for the wire and flex soldering. Casey who is expected to be the main user, wanted to have bigger working distance than the new Fernando's microscope. It will be nice also to have a fast camera to work in real time just looking at the screen.


- Fernando reported on the acceptance test of the first article PCBs (see attached document). Overall the quality was good, the PDBs are accepted and the production should continue as scheduled. There were few exceptions, some of them minor, some easily fixable: on some of the boards the vias were not filled as required. One important issue was discussed: the material used in the boards is FR-4, but we required g10. We have to find out what's wrong with FR4 (water absorption, bromine content?) and see if we really need g10. Fernando will continue with electrical tests. After the meeting we went to F117 where Fernando showed the boards, their quality is certainly higher than of the boards used in the full-scale prototype.

- One of the two cable companies was awarded, the price is 20% lower.


- Cathode foils: the PR submitted, waiting for signatures. Roger discussed with Allflex people the grounding of the flexes that is done by vias which can be very costly. Different ideas were exchange: to make the flex longer on the sides and fold it, to use double-sided flexes and connect the two sides with conductive glue at the periphery of the flexes. Roger got also important information from Allflex: conductive film that conducts in one direction only (3M company) can be used instead of the cathode soldering. Has to be heated to 400 deg F, but Bill says this should be OK. Bill will ask for samples and we will start playing as soon as we have the first article cathode foils.

- The mylar windows of the FDC packages (2 per package) have to be thicker, as Bill requested. We agreed that their thickness can be increased from 1/2 mil to 1 or 2mil which is a small change compared to the target thickness.

- Wire stringing: the strongbacks from UVA have arrived. Bill also will order the pieces needed to attach the pin-rails to the granite table.

Full-scale prototype test

- Beni connected the new oxygen sensor. The instructions how to read it in case of different gases are posted at the FDC logbook page 511. Indeed, the measurements confirmed that we have oxygen contamination of the order of 0.1% that explains the mean charge vs drift time dependence.

- Now we have an estimation for the wire resolution, using two chamber layers with parallel wires and external tracking with the IU chambers. Beni showed several plots from the FDC logbook explaining the procedure. The mean resolution is about 200 microns and varies with the distance to the wire. There's a systematic deviation from the expected by the external tracking angle, that can be corrected for, but has to be understood.


Lubomir will have a talk at a conference (CAARI2010) next week, the contributed paper is linked above; comments and remarks are welcome. Whether there will be a FDC meeting next week will be decided later next week.