Minutes of the Tracker Technical Meeting October 25, 2000 Erik reported on an analysis by Steve of face sheet requirements for SuperGLAST trays. The analysis was conservative in that it included the mass of converters and detectors but did not include any contribution from them to the stiffness of the tray. They found that the 4-ply facesheet that they had recommended for standard trays, with 1-lb/ft**3 aluminum core (0.7 mil walls), will not work (fundamental=344 Hz). 6-ply with the same core is not much better (376 Hz). 6-ply with 3-lb/ft**3 core (2 mil walls) gives 427 Hz. 6-thicker plies with 3-lb core gives 501 Hz. This is with a 389 mm closeout frame. With the final size the frequencies will come up by about 6%. Finally, with a 6- ply thin face sheet and 3-lb/ft**3 core and the stiffness of W included as a continuous layer, he gets 536 Hz. This is with a silicone adhesive assumed for the W attachment. From that, it looks like the thin 6-ply face sheet could be used for SuperGLAST trays, but not the 4-ply. The 4-ply is about 20% less R.L. than assumed in our proposal (for the face-sheet contribution). Erik said that the face sheets will require 8 weeks for delivery, plus shipping to SLAC, Pisa, etc. Sandro said that this is too long a time for their testing schedule. He will detail at the next meeting a proposal for mockup trays using their face sheet material. It was decided that Hytec should order face sheets for 10 trays standard trays (including 2 for tests at SLAC) in the 4-ply configuration, plus 4 SuperGLAST trays in the 6-ply configuration, plus additional face sheets needed for Hytec material testing. Tom reported on a venting analysis. Trays and core material will vent in a few seconds. A preliminary look indicates that venting a whole tower looked problematic through the cable runs, but this needs a closer look. It was concluded that the cutout in the electronics side of the closeout for the connector and cable should be 12 mm from the corner (as in BJ's drawings), not 20 mm. Hytec will review their drawings. BJ will send the hybrid drawing to Erik. Robert remarked that we need to finalize the cable size. Eduardo reported on requirements for payload tolerances. At SLAC they divided the problem in two. Tom will look into embedding the converters into a Kevlar bias circuit. He is not sure, but he thinks that the 200 micron range is OK for placement tolerances. Ossie said that the tolerance on the W foil dimension is about 20 microns. Eduardo will run some MC and provide a document next week on requirements. Ossie reported that they will make thermal tests today on the baby detectors and expect to have results by end of the week. They already verified that strain-gauge measurements are repeatable. Ossie reported on acquisition of dummy silicon wafers. He proposed to order for Pisa 120 turnkey samples (all steps done at one vendor). Presently he has 100 wafers cut that he will aluminize in about 2 weeks. He will get a quote for more samples (probably about $40 each). There is no answer yet from Micron on patterned wafers. Hartmut talked to Yamamoto at HPK. Yamamoto said that they can do it. Takashi is talking to them. We also are talking to ST. Hartmut will work on how many we need and when and report next week. Ossie asked if we need to measure the radiation length on a W sample? It should be just a function of thickness. There was a discussion of uniformity requirements. One possibility is that we can grade them by weight. Tom will look at a trade study between smaller variations in thickness versus keeping track of weight of converters in each tray. We should have W in hand in 3 weeks, slightly oversize. Pisa said that they can machine to size for their needs. Gwelen reported that he is working on the electronic/tray ICD. He has an outline from Hytec to start with. General question: should we combine all into one Tracker ICD? Tom will be responsible for the overall ICD. It was decided that Gwelen will just put together paragraphs for the hybrid and give to Tom. It was decided that we would have separate documents for tower-to-grid versus internal tray ICD. Sandro reported that he will pick up the pitch adapter from CERN tomorrow and mail on Friday. Wilko said that the extra controller chips are in the mail, but a new test board needs loaded still. Wilko reported that the BTEM tower is disassembled. We still need to tack down detectors. The technicians are trying this out today and hope to finish in 1 to 2 weeks. Probably UCSC can have a tray prepared for shipping to Pisa in 1 week. We need to find a shipping method with environmental control. Gwelen will look into this. Sandro remarked that they are continuing work on mechanical analysis and will put on the web some results by the end of the week. Ronaldo said that he has a team also working on software. They are ready to do some constructive work and would like to work on a subject connected with the tracker. Sandro asked if will SLAC do tests on adhesive properties? Ossie said that they will not measure fundamental properties. Sandro will send a proposal for adhesives commonly used in Italian industry. SLAC is focusing on a worst-case test of the adhesive bond. Decisions: 1. Use Hytec's recommended 4-ply layup for the standard-tray face sheets. 2. Hytec will order materials for 10 standard trays and 4 thick-converter trays. 3. The distance from tray corner to connector cutout should be 12 mm. Action Items: 1. Sandro: make a proposal for Pisa tray mockups. 2. Eduardo: document tray payload tolerance requirements. 3. Ossie: get quote on more dummy detector samples. 4. Hartmut: figure out how many facsimile detectors we need. 5. Tom: do trade study on converter thickness tolerance versus grading foils. 6. Wilko: get test board loaded for Pisa. 7. Gwelen: figure out how to ship trays to Pisa. 8. Sandro: prepare a proposal on adhesives, as used in Italian industry.