May 17, 2012 FDC meeting
- Production Construction Tracking (Dave)
- Production status
- Third package tests (Lubomir)
- Engineering update
- Electronics update (Chris)
- Tests with first package in 126 FDC E-log (Beni)
Participants: Bill, Dave, Chris, Nick, Mark, Simon, Beni, and Lubomir.
- Dave for package #4 production: on wire frame #27 tension measurements were done, #28 will go on the stringing table next. The last wire frame for the package will go on the table by the end of the next week. #26 and #27 will be deadened on Monday. #26 has components, Chris will put components on #27 Monday/Tuesday. Working now on all the remaining cathodes for the package. Expect to have all the cathode for the package ready in two weeks. Bill asked Dave to put the wire frame numbers on the samples for the wire deadening.
- Third package was fully assembled a week ago and as of today the oxygen is 140ppm and it still may go a little down. For comparison we had 75ppm for one cell and 111ppm for four cells. Roughly we have ~10ppm contribution from each cell plus ~65ppm from the gas and gas system. In any case the oxygen is very low. All the cells were tested and all the channels are fine, except we had HV problem on the top cell: there was short (~1MOhm) to ground from two positive HV sectors. It turned out one shorts ONLY to the ground on the top cathode, and the other HV sector shorts ONLY to a particular strip on the top cathode. No connectivity was found to anything else, like wire frame ground, field wires etc. After the meeting we opened the package and as Dave predicted, we found two sense wires not completely cut, sticking up and making contact with the top cathode. The problem was fixed and we closed the package. Now we will have to wait one more week to get the oxygen down and do final tests.
- Bill: final tests on the design of the installation cart before bidding. Had further discussions with Tim and survey group on the fiducial scheme (Bill reminded us the scheme again).
- When installing the last two cells we had problems with the metal pins and had to put vacuum grease on them to make the insertion easy. To avoid bending of the pins, as Casey suggested, we want to put two handles and Bill will order them.
- Chris: Jim and Chuck made the drawings of the grounding clip. It will be Cu-Be 13mill thick and will have a force of 7.5lb; Bill: in this case we have to use Rohacell between the wire frame and the cathode. One company only responded to the bid: $2k for 500 clips (need ~120 per package). Chris submitted a PR.
- After some discussions we figured out that we can easily extend the grounding to the cathode from the top cell. We just extend the Cu foil to that cathode and put the clips that we have now on the top of the copper foil, thus we will also prevent damaging the cathode foil. In this case we may not need to do the inter-cell ground connections.
- Before making the clips we have to test them but the company will not give us samples, for that they need to set up the production. Bill suggested to use the 7mill brass shimming plates (that we have) and try to make a clip according to the drawings that Chris will send. At least we can test it before the production starts.
Tests with first package at 126
- Beni: working on the wire resolution. So far it is much worse than it was in the prototype, about ~400 microns. Beni traced down the problem to the very bad timing resolution of ~14ns. It was estimated using a simplified scheme: separating only vertical (from the Indiana chambers) tracks and comparing the timings from the parallel wires in the first and fourth packages. Most likely to problem is due to the oxygen in the gas, but Beni wants to check the F1TDC using different mode. Also it could be a result of a poor angular resolution of the Indiana chambers, but to see its effect it must be worse than 5mrad. Beni will report on this in the Collaboration meeting.
- Vladimir is arriving on May 30 for six months, will be helping with the package tests.
- Due to the Collaboration meeting Monday-Wednesday next week, unless there's something urgent, we will not have FDC meeting next week.