Minutes of the Tracker Technical Meeting
July 3, 2002
There was a discussion of the status of detector procurement. Hartmut passed on information from Ohsugi:
HPK is presently processing the 600 sensors ordered by Italy. 1000 from Hiroshima will start soon. It takes 3 months for a full processing run. If HPK does not receive more orders, they will simply postpone the production schedule accordingly. Ohsugi will meet with Yamamoto when he returns from Europe to discuss the production schedule for next year, starting with October. Ohsugi needs input on how many we will order in the next half year.
Sandro said that Pisa will order another 600 detectors after testing the first 600. 100 are tested so far, and they will probably order the other 600 by the end of this month. Sandro expects another 800 to be ordered in the Autumn. He will try to send a more firm date.
Sandro said that he is modifying the wafer-testing document, LAT-TD-527. They have found that the geometric tests always show that the cuts are within the limits of the measurement error. Furthermore, 3 wafers may have been damaged due to the extra handling needed for this measurement. He proposed to eliminate this step and make only a sample test, of the 1st, last, and 1 in middle of each batch. Also, Pisa has obtained a set of reference resistors and capacitors to use for calibration checks of the meters used in the electrical testing. These will be used to check the calibration regularly, instead of sending the instruments in for periodic calibration.
Hartmut cautioned that after any long production stop we should check again the wafer cuts on a larger sample.
Sandro reported that Monday they plan to go to G&A to start ladder assembly. This will begin with 2 weeks of incoming inspection. He will refine the procedure documentation during this period. Robert emphasized that we absolutely cannot start flight ladder production until the documentation is signed off and is under configuration control. We agreed that about the first 30 ladders will not be used for flight and can be assembled prior to completion of the documentation.
Sandro reported that Plyform has completed 3 trays (as in last week’s minutes): 2 light and 1 heavy. Shake tests were done last Thursday on one of each, at a level of 7g rms random vibration. Sandro considered this mainly to be a check of the new fixture. They have been working on a fast mounting method and obtained good results: 2 hours for 1 tray with one fixture. A second fixture has been ordered. They will be able to test 4 trays per hour without Si, 2 with Si. The resonant frequencies were found to be 1180 Hz and 1134 Hz for light and heavy bare trays only. They also measured the planarity of the face sheets: 40 microns min to max. The planarity from one face sheet to the other was 100 microns maximum error. Since then there has been a delay in receiving the trays in Pisa to check the dimensional accuracies of the assembled trays. Then will continue next week with production after that check.
Drawings of the tungsten assembly tool are finished. Somewhere between July 22 to 26 they will start attaching tungsten to panels. Luisella is working on the kapton tooling design now.
Pisa would like 4 trays sent for thermal tests: 2 heavy and 2 light. One of their goals is to measure stress on the Si. Robert noted that Hytec has done this for light trays (see LAT-TD-759). However, Sandro said that one of their goals is to test putting several trays at once in the chamber. Sandro will send Ossie a copy of the proforma invoice, and Ossie will ship the trays.
Robert reported that the LAT management has convened an Anomaly Review Team (ART) to review the problem of the test failure of the flexure-to-bottom-tray joint and recommend remedial action. The goal is to wrap it up within a couple of weeks, after which we will be able to plan in detail how to change the joint design. Our goal is to hold the EM schedule, minimize changes to the tray design and associated assembly fixturing, while at the same time introducing a very robust reinforcement. The gasket concept will also change, probably moving away from the polymeric gasket toward a springy metal contact.