Minutes of the Tracker Technical Meeting

January 16, 2002

Action Items:

1. Robert: write a response to the PDR action items for Friday.
2. Ossie & John: take the stack apart and measure the tray dimensions.
3. Tom: get the trays ready to ship out next Tuesday to Pisa and Hytec.
4. Erik, Sandro, and Ossie: send Tom information on the status and estimated delivery dates for the piece parts of the Engineering Model (see below).
5. Tom and Robert: complete the table of EM piece parts and update the EM schedule.

Robert went over the PDR closeout report. The two action items relevant to the tracker group are to

1. Evaluate pre-production ICs thoroughly to ensure success of the full production run.
2. Refine assembly and test procedures.

Robert must write a response by Friday.

Tom noted that we need to clarify who is buying the last 1400 SSDs. The MOAs for Italy and Japan specify 5000 each, but the estimate for the number needed, including wastage, spares, and prototypes, is about 11400. The Tracker reviewer was concerned about this accounting, even though he did not mention it in the report.

Tom went over the results of the preliminary stacking test at SLAC. The trays were stacked Thursday, but the CMM data were lost. So Friday they took the stack apart and started over. One tray near the top didn’t line up as well as it did on Thursday. They put one sidewall on and 80% of the screws in. Monday they finished putting in screws. With no sidewalls there is no play from one tray to next, due to tight corner post pins (Erik noted that that was the original intention of the design). Tom said that they could get all sidewalls screws in but used up nearly all of the available play. Looked at other sidewall and noticed that top layer was off. There was worry that maybe a wrong-height cornerpost had been put in. This produced an idea to anodize them different colors. Tom would like to make changes to the post design so that they go together and come apart more easily. In particular, the trays are easily damaged around the corner-post holes when trying to pull them apart.

Erik said that Hytec had planned to locate everything by the corner posts and let the sidewalls float. Tom would like a little bit of slop so that countersunk screws can all center. SLAC can still analyze the printouts from the first stackup, for which the data was lost in the computer. Tom noted that one tray has an MCM closeout wall twisted by up to 30 mils top to bottom. This tray cannot be used in the stack.

Sandro analyzed the CMM numbers in an excel file (from the second stackup, I assume). The carbon carbon tray show problems in dimensions in x,y. One tray is 700 microns too long, for example. Tom thought that maybe that could be the one with the twisted closeout piece. Erik said that the corner holes were drilled at GMSI by measuring to find the true center of the tray and then referencing from that.

Ossie said that he will take the stack apart and measure carefully the individual trays and spacers. In production this needs to be controlled carefully (both sides) before putting silicon on.

Erik cautioned Tom not to rely on the screws to locate the trays. If the corner pins are left loose, then one could consider using Sandro’s scheme of pins in holes & slots. The existing trays do not have the slots, but only holes. Sandro thought that the scheme could still be used by putting undersized pins in the holes where he wanted a slot. (Of course, Sandro’s pinning scheme will be used in any case in the assembly test with the external fixture.) Robert asked Sandro for a writeup and drawing on his alignment scheme. Sandro said that it is on the web at http://www.pi.infn.it/glast/mech_mtg/pimech.html.

Tom said that next week SLAC will ship the aluminum trays and 2 bottom trays to Sandro. Steve wants back the tray with silicon on it, for thermal testing, and also the bottom tray that was not used. Tom wants to get silicon on it first. Steve noted that one bottom tray does not have precision insert alignment, so Sandro would not want that one. Tom will look at the schedule and figure it out. In response to Sandro’s question, Tom said that we don’t need to simulate the MCM mass in the prototype tower shake testing, since the mass is small and near the tray edge.

Robert asked that everybody send the status of piece parts to Tom for the engineering model. See Tom’s list of piece parts below.

Sandro reported on the Italian vibration test performed on January 3. During random vibration of the Plyform tray the screws on the two lateral sides came out, leaving it supported by only the MCM bosses. No damage was evident. They also tested a PCI-built light-core, 4-ply facesheet tray with heavy tungsten. There was some degradation of the resonance frequency from the test. However, there was no chipping or other damage of the closeout walls, which was the objective of this test (the light tray was not designed to support the heavy tungsten). Robert asked about the seemingly random variations in Q values measured in the various tests. Sandro said that they need to improve their algorithm for extracting Q values from the data.

Tom reported on a screw-up with the EM MCM PWB fabrication at Young electronics. The MCM boards do not have the thickened edge for cutting the radius. Young was sent a message to ignore that detail in the drawing, when the intention was simply to ask them not to cut the radius. Tom and Ossie are working on getting strips of material glued to the finished boards so that the radius can be cut.

Erik reported that he is expecting flexure prototypes a week from Friday. Alcomp has 40 bars of closeout material ready to ship but has been holding on to them pending seeing mechanical test data. The thermal test data on the parts look good. Steve is preparing for a thermal cycle test of the trays.

Robert asked about the status of the closeout drawings. Erik says that there are some changes on Edward’s desk. He would like to hold off a few days before releasing them to look more at the stack testing. Sandro said that there still is an issue of the tongue-and-groove, which he would like to remove to save machining costs. Robert doesn’t want to delay the machining until after the February assembly testing. He decided to give a week to look more at the alignment issues and the EM schedule and try next week to make a decision on when to start machining.

Tom reported that a new Tracker web page is online at SLAC: http://www-glast.slac.stanford.edu/Tracker-Hardware/default.asp. There still is more work to do on it, but people can start looking at it to access documents and drawings.

Tracker EM Piece Parts

Part	Purchaser	Vendor	Del Date	Need Quantity	Ordered Quantity
SSD’s	SLAC – INFN -Japan	Hamamatsu	Ongoing	10,496	11,400
Dummy SSD’s	SLAC - Ossie		12/1/01
Bias Circuits	SLAC – Ossie/Dave		1/18/02?
Thin Converters	SLAC - Ossie		12/1/01
Thick Converters	SLAC - Ossie		12/1/01
4 Ply Face Sheets	INFN - Sandro
6 Ply Face Sheets	INFN - Sandro
Light Core	Hytec –Erik		9/1/01
Heavy Core	Hytec – Erik		9/1/01
Std Closeouts	SLAC – Ossie		1/15/02?
Top/Bottom Closeouts	SLAC – Ossie		1/15/02?
Tray Inserts	INFN - Sandro
TMCM Screws	INFN - Sandro
Tall TMCM’s	SLAC – Tom/Teledyne		1/15/02
Short TMCM’s	SLAC – Tom/Teledyne		1/15/02
Converter Adhesive	INFN - Sandro
SSD Adhesive	INFN - Sandro
SSD Encapsulation	INFN - Sandro
TMCM Adhesive	INFN - Sandro	3M Conductive Tape
TMCM Handling Box	SLAC – Tom
Side Walls	Hytec – Eric	PCI-GMSI		4	5
Side Walls Screws	SLAC – Tom
Flexures & Mount Plates	Hytec – Erik			8
Flexure Mount Screws	SLAC – Tom			32
Thermal Gasket	SLAC – Tom			1	2
Conductive Tape-corners	SLAC – Tom
8 Flex Cables	SLAC – Dave
Lifting Fixture	SLAC – Tom/BJ			1	1
Vibration Fixture	Hytec – Erik			1	1
Tower Shipping Box	SLAC-Tom/BJ			1	1