Minutes of the Tracker Technical Meeting

February 6, 2003

Action Items
1. Luca: check whether the MCMs work better if VDD is raised or the clock frequency lowered.

2. Tom/Dave: see if the Kapton bias circuit can be procured with a peel-off protective cover.

3. Dave: reverse VDD and Bias at the extreme ends of the bias circuit and MCM.

4. Sandro: send encapsulated ladder test results to Robert and Darren.

5. Nick: send the French composites procedures to use as an example.

6. Darren: look into how we should track inserts and other fasteners during flight fabrication.

7. Sandro: send a drawing of the desired alignment hole pattern for the bias circuits.

8. Dave: move copper and gold away from the trim line on the bias circuits.

9. Tom: get the thick tungsten order going.

10. Nick: resolve Dave’s question about the use of a 4V tantalum capacitor.

Sandro reported that G&A is still working on the system to do wire bonding of MCMs to ladders. Next Tuesday they will wire bond from the MCM to the bias circuit. Then they will glue ladders on and wire bond to the ladders. This is about a week behind schedule, but Sandro believes that there is still enough time to catch up, as the actual work should go fast once underway.

Luca reported that the Pisa MCM test procedure & results are on the Pisa web page under the EM tower link. They found all defects mentioned by UCSC plus a few more. In particular, for MCM 75 the register read-back always gives errors. Robert noted that UCSC raised VDD or lowered the clock frequency to account for the poor timing margin in the existing system (should be fixed in the chips now in fab). Pisa will check whether the new errors are due to the timing problem.

Sandro reported that Plyform is gluing tungsten & Kapton on the remaining panels. The Kapton alignment is good. They tested by vibration 4 trays. Three of them had some known defects during assembly (they were some of the first panels built). The defects can be readily observed in the shake test, from a lowering of the resonant frequency. Nevertheless, there were no changes in frequency from random vibe test, comparing before and after the test. There also was no damage. The work confirmed that they can do 4 tray tests per day, as required. The fundamental frequency of the good tray was above 850Hz. Silicon will lower this to about 700Hz. The Q was about 47. For one of the trays with gluing problems the frequency was about 560Hz. The tray destined to be used for qualification testing with live ladders and electronics was above 900Hz.

Next week they will try out the holographic system on these trays. Sandro said that they will buy this Frascati holographic system for use either at Pisa or Plyform.

Sandro said that the trimming process for the face sheets and Kapton contaminates the Kapton surface. He would like to buy Kapton foil with a protective cover that can be peeled off at the last moment. SLAC will look into this.

Sandro said that the edge bias bond pad (AVDDA) is not in a good position for the bias bond to the SSD. (This will be solved by interchanging AVDDA and BIAS at the two extreme ends of the bias circuit and the MCM.)

G&A ladder status. 80 encapsulated ladders are under test. However, the Perugia operator became ill and stopped the tests. Another group of ladders will be ready next week, and the Roma-2 group will be doing the testing. Sandro does not have the details from the first tests but will send more information tomorrow to Robert and to Darren.

MIPOT status: the Nusil encapsulant finally is in Pisa. Sandro will go to Mipot the week after next with all materials and the inox storage boxes. He will then discuss ladder production startup with Mipot. He will propose that they build 10 ladders, wait for review, and then do 90 more ladders.

Sandro is translating the Plyform procedures from Italian into English. Tom will leave 19th February to travel to Italy, arriving in Milan February 20 shortly after lunch. He will be at Plyform that afternoon and Friday and Monday. He would like to visit Pisa Tuesday, and he will leave February 27.

There was a discussion of the schedule for a PRR of the tray panel production. We will shoot for the week of 10 or the 17 of March. Tom will close this plan when over there. Nick will send the French composite procedures as a guideline. Tom will forward them to Sandro.

Aluminum handling and storage boxes are ready for the 4 live trays. They will be shipped with trays to SLAC in wood boxes with plenty of foam.

Tom reported that the order has been placed for cores, which will arrive by the end of the month and then will ship to Italy. The carbon-carbon is still at SLAC. Tom is trying to figure out how to mark the bars with serial numbers. A SLAC technician is being found to do the work.

Responding to Robert’s questions, Sandro explained that the inner face of the CC closeout is coated at the beginning, prior to panel assembly. The outer face is coated at the very end. Sandro is interested in using black paint instead of the resin (the same black paint that we intend to use to increase the tower-module emissivity).

Sandro said that inserts are included in the Plyform order, so it will be their responsibility to procure them. Robert asked how are the inserts tracked (material, by lot, etc). Darren will look into this.

Bias circuits: Sandro said that we need to change the position of reference holes to make them asymmetric, so that they cannot be put on backwards. Sandro will send a drawing. Also, the existing circuit has one hole out of place, apparently due to an error at Parlex. Tom said that SLAC will get an inspection procedure in place to make sure that our flight procurements match the drawings. Sandro also said that the copper/gold ring all around the bias circuit must stay 2 mm outside the cut so it doesn't interfere with trimming.

Thin tungsten: Sandro reported that an order has been placed for 10% extra material. He is starting to prepare the order for cutting, which will be done by water jet. The blank sheets should arrive at the end of March. The cutting can be done in 2 or 3 weeks.

Thick tungsten: Tome said that he has a discussion going with the project office to get help with ordering. Tom will talk to Debbie & Shannon about getting these orders out. The lead times are not bad for material but can be an issue for the double disk grinding.

Electronics parts: polyfuses, PWB, HV caps, SMT parts all need to be ordered. Robert is working on closing out issues with the polyfuse procurement specification, but the order should go out now, anyway, as the requirements on the manufacturer have been settled (some issues remain regarding testing by a third party after delivery). The HV capacitor specification is released, so those are being purchased. There is one unresolved voltage rating issue with a tantalum capacitor (can we use a 4V part with a 2.5V supply?).

Erik reported that Hytec is still working on the model. They modified the closeout design slightly to relieve problems with stress concentrations in the corners. The closeouts now are nearly all M55J, with just small layer of carbon-carbon for machining the outer surface. (Thermal conductivity through the bulk is no longer a big issue for these parts, because of the heat straps.) The corner bracket has a taper to relieve peel stress. The carbon-carbon now extends just to the end of the taper. Most of titanium bonds directly to M55J. Tom said that he is thinking that the EM closeouts should be fabricated at COI. He would like to do the same for the flight hardware to be consistent. There is a question about when to install the midspan inserts for flexures. It may be best to wait until after panel assembly, so that the flexure alignment and insert installation can be done together. In any case, the sidewall inserts can go in earlier, prior to panel assembly. Tom will review this when in Italy. Erik suggested that we don't necessarily need shoulder screws for the sidewall flexures, since they will be bonded to the closeout, so the inserts could be put in earlier without worrying about alignment tolerance. Tom will take drawings to Italy and go over the bottom tray assembly and tower assembly with Sandro. Erik noted that the design modifications should not change the tray panel assembly procedure in Italy.

The M55J will get no machining except for hole drilling and edge cuts. There will be no cutting into the fibers. Erik said that they may lay it up heavy with resin on the top so that they can take a skim cut through the resin on the top side. The smooth flat mold side is on the inside surface.

Hytec is in the middle of the analysis on the load fixture. Franz is doing this, while Steve is working on the bottom tray analysis. Erik wants to get the load fixture components out to the machine shop quickly.

Tom said that so far there are no results on the acoustic analysis except hearsay that the numbers are coming in lower. It should be completed by the end of the week.

Erik said that the thermal strap design has been modeled. There are some stress issues in the copper. They may simply be immediately relieved in practice by plastic flow of the material. Either a stronger allow is needed, or else the material flow must be studied.

Tom said that there is a tower ICD modification. We will go to a 30C operational limit. This gives 3 degrees more margin for us and 2 for the Grid.

The mechanical ICD needs a drawing from Martin for release.

Robert discussed the peer review preparations. We need some kind of design report, but keep it simple. It does need to cover well the bottom tray stuff. Erik will look at the old report and see what needs updated. We also need to document test results as they are available.