March 17, 2011 FDC meeting
- Production status (David)
- Readiness Review (Lubomir, Dave)
- Electronics (Fernando,Chris)
- Engineering (David)
- Conductive tape gluing
- Chamber testing
- "Upside-down" tests (Lubomir)
- Testing set-up improvements (Beni)
Participants: Dave, Chris, Eugene, Roger, Simon, Beni, Mark, and Lubomir. Bill was busy with the drawings for the review.
- Dave: The first exercise on making cathode foils was successful; for that we used two damaged panels, but made one extra cut on one of them. To exercise the cathode tensioning we need to glue the third panel but we can use just a Kapton piece. Temporary lights have been installed in the "dirty" area. The stringing table soon will be ready and will be moved inside the clean room. The granite plate ("monument") in 126 that was used for flatness measurements will be moved to the clean room, as well.
- The clean tend in 126 was dismounted and the parts will be moved away by the end of the week. To plan the space in 126 one can use the drawings linked at the end of the agenda.
- For the readiness review both, a wiki page (linked above) and a secure website (linked to wiki) were created. The account/password for the secure site can be given upon request. There's folder with preliminary documents where we will put all the procedures, drawings and additional information. The talks also must be uploaded well before the review. Bill is working on the drawings. Dave has the most important procedures approved and is working on the remaining. Lubomir will help him with some of the procedures.
- Chris: expects the parts for the rigid-flexes soon. As of now, in the Gerber files, the flex contacts are tinned but we have not decided yet about that (see discussions of the flex gluing below). We have received 34 signal cables that were re-worked and are one feet shorter. Soon we will receive the rest 16 of the first article.
- Roger: no news from Alflex, expecting the next set of panels by March 25.
- Fernando was not at the meeting and we didn't discuss the fADC125.
- The second attempt to glue the flex to the cathode using conductive tape was successful. A sample was shown at the meeting. In the previous attempts the flex was glued to the wrong side and as a result connecting all the signal traces to the cathode ground, while the ground traces were connected to the rigid-flex ground. Still, in the first trials one could check some of the connections and they were not OK. The important now was that Casey was able to align the connector pins by using back-light through the g10 plate. Aslo we used thermal conductive silicon to make the pressure over the contact more equal. Later, however, we saw we had an epoxy blob on the back of the g10 that made the plate not parallel to the surfaces of the tool. So, maybe the procedure will work even without conductive silicon.
- To investigate the longevity of the gluing there were several suggestions. Eugene: to put the sample in and out of the fridge for several days and check it. This will simulate temperature and also (Beni) humidity changes. The radiation effects can easily be studied in HallA/C; one day there will be equivalent to tens of years at Hall D. Our techs will make more samples for testing. Any other suggestions to investigate the life time of the conductive tape gluing are welcome. This procedure will save us a lot of time and troubles, but the main question now is how reliable it is. In that respect we will postpone the decision about the flex tinning and Chris will inform the vendor about that possible change.
- Beni made some improvements in the testing set-up adding more amplifiers to the external Indiana chambers. Now we can cover almost the whole FDC chamber but we need also another F1TDC module.
- Lubomir finished with the scanning of the prototype as it is upside-down. He showed a 3D plot for the top/bottom strip asymmetry at standard and upside-down positions. It clearly shows the effect goes with the gravitation and is maximal in the middle of the chamber. There's some "fine" structure visible for all the runs that can be flattened out by improving the electronics calibration. One can upturn the problem: the ratio of the top/bottom strips can be used to calibrate the electronics. Including in addition the wire amplitudes one will have redundancy and thus a good cross-check.