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April 7, 2011 FDC meeting


  1. Production
  2. Electronics
    • Status (Fernando,Chris)
    • Cathode foil inspection
  3. Engineering
    • Tests with conductive tape (Lubomir, Bill)
    • Status (Bill)
  4. Chamber testing
  5. Other


Participants: Bill, Eugene, Dave, Chris, Roger, Fernando, Simon, and Lubomir.


- Just before the meeting the review committee sent us their final report, linked above to the agenda. Eugene commented on it: there are no show-stoppers and the FDC production can continue. There are no recommendations, just findings and suggestions on which we may answer later. The main suggestion is to test the z-axis conductive tape technique for gluing the rigid-flex assemblies. They suggest to study the radiation damages and also to continue with the conventional testing in longer term. Even if it turns out later during the production that there are problems with this technique, it will be possible to re-solder the rigid-flexes using standard soldering technique. The committee also suggested to work on the packaging and storing of the materials and assemblies. There were some healthy concerns related to the air quality (due to the use of chemicals), HV as used for testing the chambers and also ergonomic conditions. Overall the conclusions of the committee are very positive and Eugene thanked to the people involved in the FDC review.

- Dave: the production actually started already on April 1st with making one cathode foil that will be used for the first chamber. The test cathode was glued to the frame but some additional tooling is needed to cut the foil. In the mean time we will tension the first production cathode foil. Also, the first production PCB ring was glued. Now we have the tools to trim the Rohacell on wire frames. For the start of the production we will use the solder wire from UVA, even it's thicker (~0.7mm) than what we have ordered.


- Fernando: ASIC contract was awarded. Still waiting from the CDC people to confirm the parameters of the pre-amps and the FADC125 shaping. If needed one can modify the attenuation on their HV boards without changing the parameters of the pre-amps and fADC125. We already confirmed that the parameters are OK for the FDC.

- Rigid-flex assemblies: we received 480 recently and expect the last 135 in May. Fernando and Chris wanted to know how to proceed with the stuffing: to tin or not to tin the contacts. Tinning is needed if the conductive tape doesn't work and we have to solder. So far testing electrically the conductive tape we haven't seen any differences between the tinned and not tinned samples. Still mechanical tests with tinned samples have not been done yet. For now, we decided to order 50 rigid-flexes tinned and 50 not tinned so that we can continue with the production. The price will be higher by a few hundred $ due to the set-up fees (Eugene agreed). Depending on the results we will decide what to do with the rest of the rigid-flexes.

- Last week we received the first two sets of foils from the mass production that were already inspected. The foils look better that those from the first article; still visible are imprints of the rollers on the foils but these will disappear after tensioning. Another two sets just arrived. Roger asked to put the invoice number together with the results of the inspection in a spreadsheet so that he can handle the payments. Regarding the storage of the foils, so far we leave them flat on a table after the inspection and Dave ordered shelvings for that, but Fernando and Roger are concerned with possible corrosion. We decided to try with one set to roll it back in the original packing which is a more compact way of storing.


- Conductive tape tests. Bill did mechanical tests: to peel off the conductive tape one needs from 80g on the edge of the tape to about 130g in the middle. One of our techs tried it already pulling by hand one side of a sample and peeled it off easily. Bill will improve the tooling: wider and longer shoe, higher temperature (up to 350degF, according to Fernando solder melts above 400degF) and wider conductive tape. In addition if we have to, we can tape the contact with Kapton tape on the top after gluing. We also put two samples in liquid nitrogen and they are OK electrically. Bill will test those mechanically. Dave will do test also with heating up to ~80degC. Lubomir placed four samples in Hall C to study the radiation hardness as suggested by the review committee. We expect to have results from this test in a month; the first samples will have enough radiation in a week but taking them out of the Hall and reading the dosimeters will take time. Since so far there are no problems (that are not solvable) with the conductive tape we decided to start the production using this technique.

- Bill is working on different tools: the heater for the conductive tape, the new jig table to be used for the package assembly, improving the foil cutter and other.

Chamber testing

- Simon showed results from his analyses of the cosmics data with fADC. First (page 554) it appears that the wires as "seen" by the strips are at an angle systematically: ~2mm over the length of the wire. So far the explanation is that the strip pitch might be different due to the cathode tensioning. To calibrate the strips (page 555) using the fact that the charges on the top and bottom strips are the same, first he makes "sagging" correction and then finds the calibration constants for each channel. After the first iteration, the resolution improves by ~10%. The fraction of the charge in the strip with the max signal is about 50% of the total charge (page 556).