Minutes of the Technical Tracker Meeting
April 4, 2001
Hartmut reported on the recent visit to HPK. He sent out already his notes on decisions and action items (see attachment). One result of the meeting is that they are updating the SSD specs based on new data from Ohsugi. In particular, they tightened the leakage current specs, due to observed correlation between leakage current and number of bad strips. They also discussed procurement issues and space qualification of the process and pedigree of the boules. Hartmut said that HPK now is interested in making dummies, which would be blanks with just the aluminum pattern and overglass. HPK is presently producing 600 detectors, to arrive in the period June through August. In September they will start delivering 500/month, which means that this mass production will start in June. HPK has a plan to stock up on blank wafers in order to satisfy our needs. Hartmut said that we will ask for two quotes from HPK: 100V depletion versus 150V depletion. Ohsugi already started the bid process for the main production run at KEK. Tom is working on the PO from SLAC. Italy will not begin the process until May/June, and that will probably be only for next calendar year production. Hartmut stressed that there will be one set of bidding documents for the 3 places, to maintain consistency. He is now working on updating the documentation.
Hartmut said that HPK found 28 detectors in their inventory. Pisa will buy at least 26 of them. Also, Pisa will buy 10 mechanical samples.
Ronaldo requested that HPK measure the distance from the cut-line to the mask on each detector. Hartmut thinks that they agreed to do this. Most important is the edge parallel to the strips. Ronaldo would also like to measure the orthogonal edge, to ensure that square wafers are used to build ladders.
Hartmut discussed the testing of cutoffs. The plan is for one per lot to be tested in Hiroshima. Hiroshima also will track the test results from HPK and the HPK yield.
Hartmut talked to the GLAST parts man (Nick Vermani). He seems to be reasonable and agreed that the cutoff testing is an appropriate way of doing the QC. He also would like to have some mechanical testing done: vacuum, thermal shock, mechanical shock. Robert thought that much of that seems meaningless on bare wafers, since if there is a crack, it will show up first in the leakage current. Tom will talk to Nick about this.
Ossie said that he talked to Gross (a NASA materials expert on adhesives) about Nusil 1142. His opinion is that primer is a must. Also, single-component silicone requires humidity to cure, so we must be careful not to store bonded parts immediately in a nitrogen locker. He went over the SLAC thermal test data with Omar. They also checked that the glue had not released during the test. It had not, and in fact, the bond seemed quite strong (even without primer). He will release quantitative results tomorrow. Gross also agrees with the use of 2216 epoxy for SSD edge gluing.
Pisa sent back facesheet and CC materials to Hytec because they didn’t want to pay 20% duty on the declared value. Sandro said that he will send information to Hytec on how to send the objects such that taxes will not have to be paid.
Hartmut said that Pisa must find how as soon as possible to get stuff imported (especially SSD) without requiring us or HPK to declare them to have no value.
Sandro said that Plyform is looking for a hotel nearby them for the night of the 24 April. Sandro will reserve a hotel near Pisa. Althouse will arrive on Saturday in Milan, and he and Robert will stay until Wednesday.
Gwelen reported that the pitch adapter is being fabricated by Q-Flex. Sandro has not yet submitted it to CERN but will send it this week. Gwelen and Alec have been working on improving the tooling design for the pitch-adapter installation and modifying it to fit the final size. Alec is starting to machine new tooling. He and Gwelen made a small test with glass beads in the adhesive. They work well and should improve the bond uniformity, strength and alignment. Gwelen concluded that we want to look into options for etching the backside of the Kapton circuit to improve bond strength. He asked Q-Flex to do a plasma etch on the backside. The Lick Observatory people at UCSC have good experience with that technique, and Gwelen will do a test with their equipment.
Some problems are still being fixed in the MCM design at SLAC. Gwelen called Teledyne for information and answers to his questions. They haven’t gotten back to him. It doesn’t appear that they are going to help much without a contract. Tom is talking to the procurement people at SLAC. To avoid another bidding process, he will try to provide evidence that we have already explored other vendors.
Sandro reported that he was in Plyform yesterday. The 1st two mockup trays with tungsten and bias circuits mounted are complete. Another 2 panels are to be finished this week. He had discussions with them on closeout production. They have interest in making closeouts in classical carbon fiber material. Sandor will order some samples from them. In Terni there is activity continuing to set up the thermal chamber and strain gauges.
There was some discussion of vacuum deposition of aluminum on the sidewalls. The plan is just to coat the outside surfaces. Tom thought that the process might help to coat the countersink areas and protect them from the screw heads. He wants to have electrical contact from this coating through the screws and inserts to the aluminum honeycomb core. This might be difficult to achieve, he thought, if we just bonded aluminum foil to the outer surface.
Erik reported that he has had conversations with Tom and Robert about the closeout design and some of the ideas and requests from Pisa. He is working on reducing or eliminating the machining of the backsides of the closeout pieces. He talked to the machine shop about their recent experience with the Alcomp CC material. They found that the material has some memory, which might make it difficult to hold tolerances. Hytec is investigating and found that it doesn’t look so bad. Nevertheless, there is some concern about positional tolerances. Erik proposed to make the MCM side thicker by 2 mm, which would make it more stable to machine and also allow them to turn the mortise and tenon joint around. He said that he could also remove the facesheet location feature for production (depending on the needs of the vendor who does the production tray panel assembly). That would leave little machining to do on the backside. Robert objected to the additional 2 mm, as he does not want more material in the fiducial volume (under the active areas of the detectors) or more material in between towers. Robert also mentioned mass, but Erik said that the total Tracker mass is under the allocation, due to the removal of some stuff from the design (such as the ACD clips). He and Erik will discuss this offline.
Erik reported that Hytec bonded together a prototype closeout frame. They purposely racked it and broke it at about 10 lbs of force. Therefore, the assembled frame appears to be easy to handle safely, even without the core and facesheets bonded on. He needs to discuss with Sandro the position of the locating holes for ladder alignment. In particular, do they have to be on the centerline? Sandro doesn’t think so, since the tray is not exactly symmetric anyway (the converter being on only one side).
Masa reported that he sent out for review the conceptual design of the tracker construction database. There are 4 authors from UCSC (Masa), Pisa (Luca), SLAC (Eduardo), and Hiroshima (Yasushi Fukazawa). He would like feedback.
Nick asked about how to do soldering of Nanonics connectors. Wilko said that it has been done by hand under a stereo microscope at UCSC without difficulty.
Action Items: