Minutes of the Tracker Technical Meeting

December 11, 2003

Agenda:

- Discussion and decision on going forward with proposed flexure/Grid interface

- Discussion on pros and cons of reworking the EM tower into the flight interface configuration

- Update on T/V test planning.

- Discussion of need to investigate possibilities for TEM temperature control during flight T/V testing

- Startup of tray panel assembly, non-flight and flight

- NCR on honeycomb

- Open action items

- A.O.B.

Action Items

1. Jim, Darren: disposition the honeycomb cores

2. Jeff: find a delivery schedule for new cores

3. Sandro: send samples of defective cores to SLAC

4. Tom Borden: find the thermal conductivity number used by Jeff Wang and send it to Tom McCarthy.

5. Sandro: ship the drill fixture (on its protective plate) to SLAC asap

6. Tom/Robert/Jim: make a more detailed schedule for getting to the next vibration test

7. Jeff: track down the missing Hysol glue and send the invoice to Sandro

8. Sandro: check with Alenia on availability for vibration testing starting January 26

9. Tom: put together a test plan for the new concept and send it to Sandro

10.Sandro: send to Tom information on the number of inserts needed for completing the sidewall test coupons

We considered Sandro’s idea about machining the corner bracket and flexure in one piece. Erik doesn't think it is possible unless the height of the tower is raised several millimeters. Otherwise the EDM wire used to cut the flexure blades will cut into the corner bracket. Tom said that BJ is preparing an assembly drawing for flexure and bracket. The plan is that the machine shop will be responsible for delivering a matched pair already assembled.

Nanda reported on the thermal-vacuum test meetings. They discovered that there had been no parasitic analysis done in the test configuration. Doing some analysis showed a high loss of heat through the thermal blanked compared to dissipation down the tower. We will have to modify the test setup to include an aluminum cage around the tower with its aluminum sides heated. Also, they plan to keep the TEM box decoupled from the baseplate and controlled to approximately room temperature. They are making progress on defining actions. Jack has a list, including responsible parties and due dates. They are working toward a TRR in the first week of February, with the test following in 10 days. Tomorrow they will go to Rome and will meet with Alenia Monday.

Sandro has sent honeycomb NCR data (now posted on the Tracker web site in http://www-glast.slac.stanford.edu/Tracker-Hardware/QA/NCRs.html). The problems are of several types: Extra walls, cuts not parallel to cell rows, dual colors, and crushing damage to cells near the periphery. Heavy cores show only the problem with non-parallel cuts. For light cores, however, only about 5% are perfect. SLAC will consider the data and arrive at a disposition. Robert said that schedule demands that we try to find enough good cores for the first flight tower. Sandro reminded us that he must return all cores one way or another to the USA, for customs reasons.

Jeff will find a schedule for delivery of new honeycomb.

Sandro will send samples of the damaged honeycomb tomorrow.

Sandro said that even though the heavy bottom tray honeycombs are mostly good, we still are short of them. Not enough spare top tray honeycombs were ordered the first time, either.

Tom McCarthy said that he would like to know the number Jeff Wang is using for thermal conductivity of the sidewall material in his model. Robert commented that we also need to measure that number from Plyform coupons.

Regarding the flexure-Grid interface, Tom said that Mike Foss will complete detailed drawings today of the concept being worked at SLAC (see http://www-glast.slac.stanford.edu/Tracker-Hardware/ART/vibe/vibe.html). Then Tom will look at modifications necessary to the vibe fixture and existing flexures.

Sandro said that there are serious issues with removing the bottom tray. He asked if the conical section could not be put into the outer part of the flexure, as an insert into the existing counterbore. Tom said no, that since the load of the tower bears on the conical section, it has to extend all the way to the Grid. Otherwise there will be a large bending moment on the bolt.

Robert asked if we couldn’t test the new concept with the 2nd bottom tray. To make that possible, Pisa will send the drilling tool to SLAC immediately. Tom cautioned that it’s high precision is fragile, so it must be fixed to its aluminum base plate for shipping.

Robert asked if the epoxy in the side-flexure liquid bushing can be removed after removing the bolt. Tom said yes, that this will have to be done after dismounting a tower from the vibration fixture and before putting it into the Grid (the same bushing cannot be used, because the fixture and Grid alignment won’t be the same). Tom said that the conical bushing has a self-extraction feature to make sure we can get the thing apart.

Sandro cautioned that a realistic schedule needs to be made for the vibration test. He estimated at best 1 week to dismount, drill, and remount the tower. More if there is any problem. His biggest concern is the cables. Two spares are in Pisa, but 6 cables have no spares. Tom will take parts there to remake at least 1 cable if necessary. There are not enough Nanonics connectors available to make another complete set of those cables.

Jeff said that he sent the Hysol adhesive for potting connector pins. Pisa has not seen it. Jeff will track it down and will also send the invoice to Sandro.

Tom estimates this for a schedule: test the tooling the first week of January and then go to Italy the following week. Go into the vibration test at Alenia the week of January 26? Sandro will check this with Alenia.

Erik said that they could modify the static test fixture to accommodate the new flexure-grid interface design. Tom said that it would be useful to use it to study hysteresis in the new design (should be much smaller than in the old design). In any case, the static test fixture will be needed for the flight towers.

Sandro asked Tom to send a test plan to Pisa for checking out the new interface design.

Sandro will send information tomorrow on the inserts needed for the sidewall test coupons, so Luca can carry them back with him on Saturday. In early January they will send coupons with inserts for testing at COI. Plyform will make a complete new set of coupons for testing tensile, compression, and shear. None of the coupons will be taken from the panel edge this time. They will test them in early January, to be completed before the vibration test.