Minutes of the Tracker Design Team Teleconference
April 18, 2001
Sandro reported that 18 ladders have been assembled in Italian industry: 9 at Mipot and 9 at GMA. One ladder has one detector out of alignment by 40 micrometers. However, the rest of the ladders are all with 10 micrometers over their length.
Research on tungsten converter plates indicates that the thickness tolerance for the 18% converters will be difficult to achieve at best. Good-Fellow can make the converters within our thickness tolerance, but they are concerned about the large quantity we need. A tungsten/copper/nickel alloy (95% W, 1.5% Cu, 3.5% Ni) has been located that can be machined. The question was asked how this alloy would affect the radiation length and the science. Hartmut will research this issue and respond. The first impression is that the standard thickness, 0.7 mm, that is available of this alloy will be acceptable.
Sandro discussed his insert proposal for tray alignment in the tower. See the attachment. There will be 8 of these pin/inserts per tray—two per closeout. They could be removed after the screws are installed or else left in place. This concept will be discussed further next week in Italy.
Hytec reported that two sets of carbon-carbon closeout walls are being machined. Samples will be carried to Italy next week.
The thermal analysis was reviewed at Hytec with the Chomerics gasket material between the tower and the grid as well as for both Allcomp and SGL closeout materials. The results give an 11.6C rise from the grid to the top tray with Allcomp closeouts and a 14.7C rise with the SGL closeout material. (The closeout material affects both the heat conduction from the grid to the tower wall and from the tower wall to the MCM. The former is the biggest contributor, as that is where the power density is highest.) Erik will call Bernard at NRL to discuss the temperature range that the calorimeter requires. (Note added by Robert while editing: The issue is not really the calorimeter temperature, but rather whether the thermal radiators can hold the grid temperature low enough that the top of the tracker stays under our maximum allowed temperature of 25C. Hence we should talk to Martin.)
The insert testing, for galling and pull out, of aluminum inserts with A286 screws has been completed at Hytec with good results. No galling was observed after 10 insert removal cycles with the screws loaded to 80% yield in each cycle. Further tests may be done after a discussion is completed, next week, about the total range of testing and rework possibilities.
General discussion: Sandro requested that Erik bring his vibration test data and processes next week, and Erik stated he intended to. Sandro asked how thick was the Parylene coating. Erik responded that it is 2 to 10 micrometers. Gwelen pointed out that the old thermal specification from Martin does not have any requirements for thermal cycling and no lower temperature limit for the grid. Steve reported that he has located a vendor for EMI shielding on the tower walls. The three materials available are Cu, Al, and Ni. Al is preferred, as it has the shortest radiation length.
UCSC: Gwelen is trying to finish his report on the plating requirements for wire bonding. The pull testing of the pitch adaptor to the MCM continues. Results show that plasma etching of the Kapton results in the strongest bond with epoxy. In fact, the pitch adaptor could not be pulled off of the MCM when bonded after plasma cleaning. A report will be written (no date given).
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