Minutes of the Tracker Technical Meeting
November 22, 2000

The meeting started with a general discussion on the coordination of having
the panels built in Italy. The cost of the carbon/carbon closeouts was
estimated, by Hytec, to be $8K for the first order, or about $700 a panel,
and for the production run the cost would drop to about $400 a panel.

The web site for Hytec was sent to Pisa so that they could access the
preliminary drawings of the panels.

During next week's meeting there will be a discussion on the best time for
Tom and Steve Nye to visit Pisa and discuss the panel design with the
Italian vendors, after Pisa has some time to look at the drawings.

Pisa is planning on 8 mock-ups. Four mock-ups will be fabricated now
consisting of just core and face sheets and four more will be fabricated
using carbon/carbon closeouts and 6 ply face sheets early next year. Eric
will look into the cost and schedule of additional carbon/carbon closeouts
to support these mock-ups. The delivery date of the 6 ply face sheets is
currently 12/26/00.

Pisa asked for more information on the Nusil adhesive - Ossie to forward as
soon as possible.

Ossie announced that the tungsten converter material for the mock ups was in
house. They are 5 mil and 25 mil thick, whereas the design is now 4 and 25.
A general discussion on the sizing of the converters to the flight
dimensions was held.  Tom is getting a 1-piece tungsten converter priced, including
costs for integrating it into an aramid-fiber bias circuit.  He noted that the
aramid material is about 3 times more expensive than polyimide, with a finished
board being about double the cost of polyimide.   

Tom is to forward the spread sheet with the tracker dimensions to Italy and
UCSC.

Review of the Pisa drawings (later in the day):

GLAST Ladder assembly fixture:
- Ossie was concerned about the large amount of machining on one side relative to
the other.  He said that this could cause the resulting piece not to be flat.
- Ossie stated our requirement that there be no contact of metal with the Si detectors.
The edge that the ladder is pushed up against for alignment should be teflon also.
- Ossie suggested that the contact points for the detector edges, for alignment, 
should also be radiused, and that the contact area should be relatively small,
to minimize the probability of grit getting in and disturbing the alignment.  John
noted that in his design the round pins give a natural lead-in to the contact point.
He machined them to a slight flat just to ensure straightness of the ladder edge.
- John noted that the chips need to be supported near the edges where the 
detector-to-detector bonding takes place.  The problem is that the Si wafers
tend to be bowed, so if they are supported in the center one gets vertical steps
at the glue joints.
- Gwelen suggested that we would like to keep small the exposted horizontal contact
surface also to minimize the chance of grit getting on the surface and scratching the
detectors.  Ossie said that one source of such grit is chips from the sawn edges
of the Si wafers.  The clean-room filtration won't help with that.
- Ossie brought up his idea to use "Gelpac" for the vacuum contacts.  This stuff holds
onto the detectors and requires vacuum only to release it.  That way one does not need
vacuum lines in the way when carrying the fixture from one workstation to the next,
for example.
- It was noted that John's design has the 4 vacuum valves built into the fixture, so that
only one vacuum hose needs to be attached.
- Gwelen expressed concern about the edge clamping force.  John's design uses spring 
clamps that are force limited.

Box for wire bonding, testing, and encapsulation of ladders:
- SLAC and UCSC pointed out the utility of the dovetail edge on the existing fixtures,
which allows quick mounting into wire bonders, test stations, encapsulation station, etc.
- Ossie thought that in general the design looks more complex than necessary (compared
with the existing fixtures).
- We could not understand from the drawing the cover arrangement.
- In the existing fixtures the electrical test circuit is a separate piece, which might
be considered to save money in the new design.

Bridge:
- There was concern that it might not be stiff enough for its weight.