Minutes of the October 9, 2002 Tracker technical meeting
1. EM schedule
- bare trays
- trays with W and Kapton
- EM mechanical MCMs
- EM working MCMs
- Mounting MCMs
- Mounting ladders
- Final wire bonds
- Electronic and environmental testing of trays
2. EM test station for Pisa
3. Luca's trip to SLAC
4. 50 vs 300 ladders at G&A
- Ossie: make sure the the CMM is available for the new tools.
- Tom: find out from GSFC why the GE615 RTV cannot be used.
- Tom: check on why Nusil cannot ship the conductive glue for ladder attachment.
- Sandro: check whether enough tungsten is in hand for the EM tower.
- Tom: give connector savers to Dave for the Pisa test system.
- Luca: send Tom a list of organizations in Italy that may use LAT test software.
- Sandro: find costs for obtaining thin tungsten in Europe for flight production.
The top tray insert installation fixture and assembly fixture should arrive at SLAC next week. Ossie should schedule use of the CMM at SLAC to QC them before shipping to Italy.
Production of tray panels will restart tomorrow in Plyform, following repairs of the equipment. They expect to be able to assemble at a rate of 3 trays/week starting next week. Sandro predicted a finish data of Nov 8 for all but the bottom tray.
Pisa measured the tungsten assembly tool. It needs slight modifications for glue clearance. Sandro expects it to be done in about 1 week, so they can start gluing tungsten in week 43.
The Kapton assembly tool was due yesterday. Sandro needs to check on the status.
Sando says that Plyform should finish all of their work on the EM trays by the end of November.
In parallel, during November they can start placing ladders on trays.
Tom will talk to GSFC about why we cannot devolatize the GE615 RTV adhesive prior to use.
G&A can start making ladders without encapsulation, with testing done after wire bonding. It was agreed to allow G&A to start on this.
Pisa has a problem obtaining the Nusil glue for ladder attachment. Tom will check on this. Sandro will forward the message that he received from Nusil.
Tom will meet with Teledyne tomorrow to discuss the MCM assembly progress.
Dave is making a test connector for verifying the mechanical/thermal MCMs when they come off the line at Teledyne.
Sandro said that development of integration procedures for attaching the MCM to the SSD ladders is on hold because of conflicting ladder activity at G&A needed to develop procedures for the new encapsulant.
There was a meeting with Parlex meeting yesterday. The EM readout cables will be finished in a week or two. Tom gave Parlex enough connectors to populate one complete set. Robert has 110 connectors on order. The mini tower needs 4 cables, but only one or two Nanonics connectors on each.
Sandro will check if they enough tungsten in Pisa for the EM. The mini working tower has only thin tungsten on the top tray. Some more thin tungsten is on order (it was ordered in case it would be needed for the 3 bottom trays).
Tom will give Dave 2 connector savers so that he can finish the enclosure for the interface board to be sent to Pisa. UCSC assembled and tested a mini-MCM that will be shipped to Pisa in a day or two.
Tom said that ITAR needs a list of organizations in Italy, including vendors, that will use LAT software. This could be an issue if we make use of the spacecraft vendor software. Luca will send a list of organization names.
Robert suggested that we use an existing bottom tray and sidewalls to test tower assembly, since the new bottom tray will be late. Tom said we will have to work around a schedule conflict with bottom tray test work.
Erik said that Hytec is concerned about the tower displacement with the general GEVS input random vibe spectrum. The PDR analysis was done with the Delta-II spectrum and also assumed some support from a polymeric gasket between tower and grid. With the new spectrum, which doubles the power around the first lateral resonance, Erik estimates displacements of 400 microns rms, which is too much. He reckons that we need to go up from 100 Hz to about 130 Hz. To do so, they may redesign flexures as single-pieces with blades further apart (8 mm?). But then we must also consider what this does to the loads from increased lateral stiffness.
Tom said that there is a troubling issue with the magnetic properties of the invar. The problem is not the ACD PMTs but with the ACS and associated magnetometer on the spacecraft. It can tolerate only a few percent of the Earth's magnetic field. Current estimates are 20% to 25% from invar bottom trays. This could be minimized by heating the invar above the curie point before assembly, to eliminate permanent magnetization, but that would still leave a risk of it getting magnetized again after assembly. SLAC is purchasing some invar to make several mockup closeout frames to test.
There was a discussion of the thin tungsten size and tolerance. Present EM material is 5 mils thick. For flight it will be 4 mils. Sandro will look into cost and tolerance available for thin tungsten in Europe. In the U.S. we can obtain the foils for $14 each to 10 mils (1/4 mm) tolerance. More precise cutting by EDM would cost $7 more. Tom will send a spread sheet to Sandro on this. We believe that the 10 mil tolerance is fine and consistent with Tracker requirements. The squares would be cut 9 mils smaller in size to keep within the maximum allowed by the tooling.
Luca said that the SSD database is available from the Pisa web site. There are two reports: Pisa tests and HPK tests. There is also a facility to make one's own analysis. Download the MS Access datafile and an executable file and select the analysis. He will do a similar thing for ladders. Robert said that he has a student starting to work on a database for the ASICs and MCMs. He would like to follow the Pisa example. Luca said that he can offer some advice when he is at SLAC.