Minutes of the Tracker Technical Meeting April 12, 2000 Present: SLAC: Gary, Elliott, Martin, Hartmut, John, BJ, Eduardo=20 Trieste: Michela, Erik, Julio, Guido Hytec: Erik, Eric, Scott=20 UCSC: Robert, Alec, Masa, Jose, Wilko, Gwelen Detectors have not arrived yet from STM. Michela called them and = expects an answer today. The answer came during the meeting. Monday = they will ship to Trieste. Half will ship directly to SLAC, but a week = to 10 days later, so that measurements of strip currents can be = completed. Environmental Chambers: John found that new ones go from $6000 to = $15,000. This is without vacuum capability. The low temperature is = typically -35 to -40 with a mechanical 1-stage fridge. With 2 stages = they get down to -70. A lot of them already exist at SLAC, with most = heavily used. John found one in the power conversion building with a = 2-stage fridge, which is seldom used and could be available to use. It = is about 2 feet on all sides inside. Outside it is the size of a large = kitchen refridgerator. The cooling rate is about =BD to =BC degree C = per second (presumably empty), although John thought that spec might = refer to liquid N2 cooling. =20 Hartmut discussed the issue of how we will arrive at a decision on = pitch. He has written a detailed document on the issue. In summary, he = is worried about S/N for inclined tracks as well as power. Therefore, = it is crucial to look at the efficiency for inclined tracks in our BTEM = data. Robert and Wilko are working on this. Robert would still like to = get some field calculations comparing various configurations with regard = to field intensity near the strips. Guido offered the services of a = Trieste person who has a program for this purpose. Hartmut will send = the desired configurations to him and to Takashi. Elliott stressed the = importance of this being reviewed from the science point-of-view. = Robert will talk to Steve about this. The schedule appears to demand a = decision by around the end of April. Given that short time scale, = drastic changes are ruled out. There is still interest in changes at = the +15% level (we are also evaluating +40%). This may be the first = decision item for instrument design team when Tune arrives in 2 weeks.=20 Martin summarize the current understanding on temperature specs. He has = been in close communication with Brenda at Lockheed. The proposed = operational range is -10C to +25C, with testing of an operating = instrument to 10C beyond this in both directions. The proposed survival = range (instrument powered off) is -20C to +40C, again with testing to = 10C beyond this in both directions. The range available for = fluctuations is a major driver for the cooling design (radiators etc). = Of the 35C operational range, the Tracker will use up to 15C just for = tower walls, plus another 5 or so across the grid, leaving only 15C = available to play with. Expensive K1100 fibers could reduce the = side-wall contribution to about 7C (at an extra cost for raw materials = of around $20k per tower). The cheaper P30 CC option that Hytec is = investigating is expected to get to about 10.5C down the tower side = walls. Hytec doing numerical analysis of C-Pb structures for the GLAST = converters and will summarize the results by next week. SLAC will make = a test piece (which should be aat least an inch square) with 300um C on = bottom (which they have in hand), 75um C on top (stuff used in the = BTEM), and 3.5% Pb in between. They need to measure the CTE and, maybe, = modulus. The piece needs to be constrained to a plane for the = measurements. For the UCSC/Hytec structures recently tested, that was = done by gluing them to the top of a piece of aluminum hexcell, which in = turn was bonded to a ridged plate. The hexcell holds things in a plane = but offers little resistance to lateral motion. Eduardo will talk to Ed = Garwin about making the measurements at SLAC. Martin will get = information about the 75um face sheets for Hytec's analysis and send to = Eric. Guido talked about efforts to prototype a C-Pb laminate for the = SuperGLAST layers. He was at CERN last week for an ESA workshop and = talked to Alfredo Placci. He proposed a 10 by 10cm square with 125um = C/90um Pb/125um C/90um Pb/125um C laminate. The objective will be to = measure the CTE. Robert encouraged them to establish contact with Hytec = to work out what would be the best test piece to start with. Eric's = preliminary calculations indicate the need for about 40% C and 60% Pb, = assuming the use of high-end fibers. Eduardo was recruited to organize = and track these efforts, together with the thin-Pb version being worked = on at SLAC. Near the end of the meeting Guido received a positive = response from CERN, which will be forwarded to Eduardo. CERN is also = willing to do some numerical analysis Jose summarized progress on analysis of beamtest data. Wilko installed = the reconstruction program in CVS. Monday there was a new release of = the raw data root tray. It was incorporated in the reconstruction = program and tested yesterday. The tracking appears to be working fine. = They are now studying the calorimeter and tagger reconstruction. Then = they will work on (1) filling in the root structures for the tracker = output and (2) study the PSF and tails in PSF. Arrache at College de = France will also start to look at the calorimeter code and work on it. = Taka would like to help with efficiency analysis. Wilko will call Taka = about getting together to organize this. Alec reported on progress with the hybrid corner piece. He made = full-length (for BTEM) corner piece and attached it to a hybrid. Now he = is getting ready to put Kapton on and is working on making tooling for = that. Robert noted that all of this work is assuming the original = spacing between hybrid and closeout. At one point 10 mils was taken out = of that, but it is needed back. Are the drawings up to date? Hytec has = 38cm tray designs. Erik will put them on their FTP site and send the = info to UCSC and SLAC. Robert asked if anything has been done yet on UV curing? Eduardo = reported that one trial was made, which broke very easily. He got some = new glue from Fermilab but doesn't know if it is NASA qualified. Gwelen = recommended starting all glue investigations with the Goddard database. There was a long heated discussion on ladder gluing jigs. Eduardo had a = design that Gary wasn't happy with. To make a long story short, my = conclusions as follows. We would like to improve upon the methods used = in the BTEM to meet the following requirements 1. 50um rms precision at the tray level 2. 100um absolute tolerance at the tray level (this would essentially = guarantee point 1, of course) 3. Ladders should not deviate by more than about 1/3 of 100um absolute = from one detector to another, so that when we place them on the tray = (not using shims like in the BTEM) they can be guaranteed not to = conflict with each other. 4. Detectors are vacuumed into a plane while curing. 5. A good quality CCD camera with video monitor is in place above the = jig for immediate verification before curing. 6. Rapid cure. 7. Improved control of the amount of adhesive that gets into the joint. 8. The time for assembly should not be greatly increased with respect to = what was achieved with BTEM ladders. SLAC should come up with a proposal to meet these requirements, which = should be reviewed by Alec at UCSC, somebody to-be-named at Trieste = and/or Perugia, as well as by Ossie at SLAC. =20 Issues: 1. Be sure that everybody and all drawings are in agreement that we are = NOT removing 10 mils of clearance between hybrid and closeout with = respect to the BTEM design. Action Items: 1. Wilko and Robert: measure at the detection efficiency for inclined = hadrons in the beam-test data. 2. Hartmut: send configurations to Guido and Takashi for comparative = electric field calculations near the detector implants. 3. Robert: communicate with Steve Ritz about the science implications = of a change in pitch. 4. Eric Ponslet: analyze representative C-Pb sandwiches and summarize = the results in a report. Included will be 300um C/3.5% Pb/75um C, since = that is what we have materials to construct at present. 5. Eduardo: talk to Ed Garwin about making the CTE (and modulus) = measurements on C-Pb structures at SLAC. 6. Martin: send information on the BTEM 75um carbon face sheets to Eric. 7. Wilko: call Taka to arrange a meeting to organize work on the = efficiency measurements. 8. Erik Swensen: put the 38-cm tray drawings on the Hytec web site and = make them available to SLAC and UCSC.