Minutes of the Tracker Technical Meeting May 10, 2000 Present: Jose, Wilko, Masa, Alec, Gwelen, Robert, Eduardo, Guido, Ossie, BJ, Taka, John, Elliott, Hartmut, Gary, Eric, Erik Guido said that in Trieste they have made some new calculations of fields in detectors. He believes that 235 microns is feasible. The results will be sent to Hartmut and Ohsugi. Also, he has asked a colleague in Bologna to allow Trieste to use their climatic chamber for ladder tests in June. Ossie said that he measured 5 mechanical samples of size 6.4 by 10.7. The bow in them is identical from one detector to the next. There is no twist. It looks like a section of cylinder with the bend in the long direction (strips wrapping around the cylinder. The measurement tool exerted a force of less than 1g and had a resolution of 1/10 micron (did I get this right? Seems kind of small). A bow of 50 microns was measured with this force. The force required to press a detector down flat is 13 grams, which is consistent for all samples. Also, their thickness is identical to 2 microns. The measurement was done in a temperature controlled area. John reported on a series of tests he made gluing old silicon pieces together with UV curing adhesive. He varied the cure time and bond thickness. He found that with a 50um bond line the UV adhesive wouldn’t cure down in the gap. Even a post cure in an oven at 60C for an hour didn’t help. A 120um glue line did cure from UV and was the strongest of all the tests, according to Eduardo’s sensitive fingers. That bond thickness, however, requires some means of spacing to hold the bond line. Ossie has obtained some samples of room temperature cure space qualified epoxy. Also, he found that one can cut cure time in half for each 18C increase in temperature, so a moderate baking would greatly reduce the cure time. Gwelen reported again on Pb creep. Eric suspected an error in Gwelen’s numbers, but Gwelen reviewed his calculations and didn’t see an error. Robert initiated a discussion of the use of compliant adhesives to isolate the lead expansion and contraction from the detectors. Elliott suggested the use of tantalum in the SuperGLAST layers and said there would be about a 15kg mass penalty. Tantalum might work best in the case that a compliant adhesive is used, since it moves less than lead. Gwelen reported that 3M has 2, 5, and 10 mil transfer tapes available without a foam core. Somebody said that temperature might be an issue with tapes, but Gwelen said that these space-qualified tapes have in their specifications a much larger operating range than what we require. Alec reported on progress with making the right-angle interconnect. He has successfully made a 32-cm long right-angle interconnect with 40 mil radius, completely mounted on a board with a Kapton circuit glued on. The Kapton was trimmed on a milling machine to simulate the use of a router. The result looks very good. There is no significant glue squeeze-out, and the glue thickness is very uniform. The tooling that he devised gives excellent alignment without any futzing around. The bonding surfaces are flat and should work well. Gwelen did a wire bonding tests on the previous short prototype version and sent around pictures of the result, which looks very nice. It is already clear that this technique is going to work well. Soon we will be ready to design a prototype Kapton part specifically for this procedure. We may have to test that first with the old length of boards, since new ones won’t be available for a while. Jose reported on progress with understanding the PSF. He scanned some events out in the tails and discovered that the tagger energy that he was using was often way too high. For example, in one event there was 1 GeV in CAL, 4 GeV in tagger, and a wide opening angle in the tracker suggesting an energy much lower even that 1 GeV. He is at the moment concentrating on getting the Root output finalized in preparation for next week’s meetings. Eduardo has some more results on TOT analysis. He is able to see clear differences between 1 and 2 electrons going through a single strip. He says for this analysis he needs a dynamic range up to 6 MIPs only (about 20us). He is not quite ready to write it up. There was some ensuing discussion of the motivation for the TOT. The original motivation was to remove background from tracks coming out of the calorimeter and ranging out in the tracker. No work has ever been done to evaluate how well that would work. A somewhat later motivation was to eliminate single-electron tracks that sneak past the ACD from the high-energy photon sample. Eduardo’s analysis is the first work that has been done on this. Hartmut asked if we want more baby detectors. The answer was yes. He also got a price quote on special mechanical samples that could be made by Hamamatsu: $200 each. STM detectors: Guido reported that a new batch has been started. One wafer will be sent to Takashi for study with the IR camera.