Minutes of the Tracker Meeting
1. MRB: please see the list of NCRs and presentations on http://glast.pi.infn.it/GLASTtalks.html#MRB
2. Discussion of what to do about the non-working ladders(s) on Tower-1
Bad channel NCRs:
NCR 435: Kapton tape was not
applied to the back-side of cables on Tower-2, except over the resistors. This will be used as is. Starting with Tower-4 SLAC will apply the
Kapton tape. SLAC plans to make a form
board to locate the tape. Tower 3 cables
are already in
NCR 434: 1 Tower-2 sidewall has no mechanical tests available on laminate coupons. All process tests, including void content and fiber volume, were good, and the detailed results will come from Plyform. They cannot have the mechanical tests on the laminate done in time for Tower-2 vibration testing. Sandro mentioned that they may not have enough material to do these tests in the future, which will be another issue. He made the case that the laminate mechanical tests are redundant with tests already done by COI, while the Plyform process controls are covered by other tests. Sandro will write a short summary to send to Ben Rodini for his review.
NCR 431: On one tray the top Kapton of the bias circuit delaminated from the Kapton back cover around the edge of the tray. The delamination generally progressed up to the internal copper plane. The delamination tore off the HV pads in one location, so the tray is not useable without extensive rework. Richard Gobin will look for serial numbers of bias circuits in the same lot. So far this is the only incidence of this problem, so it appears to be a defect in the bias circuit fabrication.
Persis will request in writing the plans for Towers 15 and 16. (Note: the rebaseline change request approved concurrently to this meeting states that the last 2 Tracker towers will be non-flight.)
NCR 427: Tower-1 vacuum out of spec. This was deferred to next week to allow Nicola to prepare detailed reports.
Tower-1 ladders: detailed symptoms were presented for two ladders. One was a transient problem that has never recurred. The X16 Ladder-0 looks serious and could be the result of a mechanical failure. The Tracker team wants to pull the sidewall off to see what happened. Even if it cannot be fixed it will be important to understand the cause, to avoid such problems in the future. An MRB will be held Monday morning to get approval to remove the sidewall.