October 13, 2011 FDC meeting
- Production Construction Tracking (Dave)
- First package tests (Lubomir)
- Engineering update (Bill)
- Electronics update (Chris)
- Testing set-up at EEL126 (Beni)
Participants: Eugene, Bill, Dave, Chris, Simon, Beni, Vladimir, Mark, and Lubomir.
- Dave: First package is fully assembled as of yesterday. Now working on the second package. The first cathode (type-3) is ready. Working also at another two cathodes and two end windows together in order to save conductive epoxy. On the first wire frame 54 resistors were damaged due to wrong orientation of the PCB ring during lamination. It was followed by corrective actions so that this will never repeat again; the resistors were replaced. There was another problem with the first wire frame when replacing the HV caps. The first replacement resulted in somewhat elevated leakage currents and it was decided to replace them once more. After the caps were removed it turned out many of their pads were delaminated. We will continue the production with the next wire frame that was already laminated while trying to fix the first one. Bill says somebody from the electronics group already fixed delaminated traces on a board before.
- Lubomir: Full first package running with gas since Wednesday evening. Leakage very low: bubbling at 35 ccpm. Will start testing today evening or on Friday. Valdimir tested the five cells before and found one problem: on one of the newly installed cathodes (type-1) on the top of cell#4, one flex delaminated completely from the cathode. All the conductive tape was on the cathode and nothing on the flex which is not normally what we see. Suspect the gluing temperature was not correct. Also the kapton tape that we put on the top of the flex/cathode was covering mostly the flex area and it may have lost adhesion to the cathode during cathode installation due to g10 deformation. In several cases when we had to remove the rigid-flex from the cathode pieces of conductive tape remain on both sides. The flex was glued again and the cathode installed at the same place. Now with all the six cells in the package Vladimir will test all the planes above and including this cathode since all these were either re-installed or never tested.
- Bill has drawings of many parts and tools ready, but we can't use the FDC account now. The new hubs will make the installation easier and will prevent from damaging the frames, therefore everybody agrees we need them urgently. During the meeting Eugene got permission to spend $1.7K for their production. We can start stacking the second package using the metal pins/hubs from the prototype since they are shorter and then replace them when we have the new hubs.
- Curtis Mayer gave us samples gluing Rohacell with aluminized mylar using three different Scotch Weld Epoxies: 1838 B/A (the one that we use), DP190 and DP460NS, demonstrating increasing adhesive power in this order. We are not using Scotch Weld with mylar, but Bill wants to try using DP460NS for gluing the mylar on the end window and probably on the cathodes. Now we use Hysol at these places.
- Chris: All the pre-amp cards both FDC and CDC have arrived. We also have all the guiding and the cooling brackets. Cody will start testing the cards with the third fADC125 we recently got from Gerard. The plan is first to have all the pre-amps for one FDC cell tested, so that we can try the installation of one colling loop, then to have the cards needed for one package.
- We discussed whether we can use the cooling tubes as pre-amp grounding. The problem is that with the new designed magnet in case it quenches one expects ~20mV e.m.f. on the loop (Eugene). The cooling tubes have breaks but if there's contact to the pre-amp brackets, the latter in turn connected to the ground on the cathodes or PCBs, one will bypass the break. The good news is that the resistance on the cathode ground is typically several ohms, resulting in less than 20mA current. As for the PCBs one should avoid having the cooling break between two anode cards that are on the same board. This was discussed with Bill after the meeting and it looks the problem can be solved. All this will be prototyped on the first package whenever we have the pre-amp cards. One thing is sure, we don't want to use water as a coolant.
Chamber testing at 126
- Beni: will have all the F1TDC needed by next week. The DAQ is running now, as before with one create. Since we don't have the fADC125's one create will be enough for now.
- Eugene suggested to start testing the first package in 126 before we have installed all the cards and cooling system at Blue Crab. The other option is to have everything installed and tested and Blue Crab and then moved to 126. It's not obvious what is the best approach and we will discuss this again on the next meetings after completing the tests with a source at Blue Crab.
Coffee and cake after the meeting at Blue Crab to mark the completion of the first package.