Minutes of the Tracker Team Meeting
New Action Items:
We set up a technical meeting on
encapsulation issues, including vibe/thermal tests, to take place Friday, after
the management meeting.
Plan for an MRB on existing trays:
Monday
Bias-circuit bonding items: Tiles
need to be in
Summary of Wednesday's visit to
Plyform:
INFN discussed with Luisella all points in the TART recommendation. Giovanni is writing minutes to send out today
(they are now posted on the Tracker web page at SLAC, in the meeting minutes
section). Etch of the first lot of tiles
is to be done in
Regarding cure schedules, they will
do T-peel test on 3 articles with curing at room temp and 3 at room temp for 24
hours and 2 hours at 66C. The old tests
were done after 24 hours room temperature only (i.e. incomplete cure, only to
working strength). Ben will send Sandro the
ASTM hardness test document. Monday
etched tiles will be in Plyform to be primed.
They should be ready to prepare peel tests by Thursday.
Compression pad: Plyform has a
candidate material that looks good, except that it is a little bit on the thick
side (2mm). They will try it out. Meanwhile, Jeff found 16inch square material
and is ordering two types (varying in modulus) and in both 1mm and 1.5mm thicknesses. Jeff
has some samples that he will send immediately to Sandro.
When can the EM ship to SLAC I&T? INFN wants
to do an ESPI test on the top tray and will paint the silicon to enable
that. This is to satisfy one of the TART
recommendations. They can do it next
week. The EM should be in SLAC October
1. The old container and data logger can
be used for the shipment.
Recalibration of torque wrenches for
tower assembly: we need to reset them to
the values on the assembly drawing. A
matching set is at SLAC and is being reset and will ship to INFN asap. Then INFN
should send back their set to SLAC to be reset.
For Tower-0 (trial assembly) we
resolved to torque all sidewall fasteners to the spec amounts (essentially the
same as used in the EM), but we will not use Solithane. Sandro said that well before Tower A assembly we will have plenty of sidewall test pieces that
we can use to test the Solithane procedures.
Emilio has put a torque pattern into the draft procedure. Dave and Martin will download it and review
it.
INFN explained that they plan to
assemble the sidewalls to the tower dry, initially. Only after the functional tests have all been
completed (including “burn-in”) and the tower is aligned and upright, then they
will remove the fasteners 1 screw at a time to put Solithane on and re-torque.
We need information from someone
with experience with using Solithane on small fasteners. Dave will look for somebody.
Pending change on cable hold-down
clamps for connector-saver ESD cap: this is with regard to the clamp that fixes
each cable to the cable hold-down plate.
The connector saver is restrained to the plate with a clamp, but there
is no ESD protection, with the connector pins being exposed. SLAC did a redesign of just the clamp, to
include an ESD cap, and the drawings went out for review yesterday. No hold-down clamps of the original design
were shipped yet. Robert Ruland will
hand carry them to
Tower Assembly Items:
A schedule for the Tower-0 assembly
was provided by Emilio. Dave was not
sure about how much time is needed for alignment, but Emilio’s start time agrees
with the present travel plans for Ruland and Tackes
(Sept 20-24).
Arthur sent around a note yesterday
concerning cable installation issues.
Robert noted that the problem reported with the trigger acknowledge
signal from the top cactus arm was probably just a confusion resulting from an
anomalous design of those cables, which were chopped down from the full-size
cable design. In short, the 3rd
arm of the mini-cable came from the 9th arm of the full-size cable
layout, because we wanted to simulate the top of the cable for these
installation studies. To make the
readout work, the address of that arm was changed from 8 to 2, but we neglected
to reroute the trigger acknowledge.
Consequently, the trigger acknowledge goes to
the 9th input in the TEM, not the 3rd.
Arthur suggested adding a stiffener
to the cable to back up the Omnetics connector on the
top-most cable arm. Robert said that
while it is too late to introduce such a design change at Parlex, this may be
possible as a post-bonding operation carried out at SLAC. Dave will look into what can be done.
Robert expressed a preference to use
nonflight cables for the Tower-0 assembly.
These are former flight cables from panels in which GSFC claimed a bad
coupon. Still, most of the cables used
will have to be flight cables (although another option is to provide these
cables to Gunther Haller after the Tower-0 assembly, since we do owe him a
set). In any case, we should not do
anything irreversible to the flight cables in terms of glue or tape.
Arthur will do a new tool design for
bending the cactus arm, as the existing tool is too slow and unwieldy.
There was some discussion of how to
restrain the cable in the Tracker.
Arthur proposed a silicone pad between the structural closeout and cable. He will make a sketch, since there was a lot
of confusion about this picture in the meeting.
Status of Grid I/F hardware assembly
procedure: Arthur sent out final draft for review and approval.
The existing cable corner brackets
are no good, due to poor machining and wrong plating. They are being reworked for use in Tower-0
but are definitely nonflight. They will
be glued to the existing top tray, which also is non-flight.
Thermal vacuum test preparation
status and plans for purchase or lease of a TQCM: Nicola reported that the GSE
for the thermal-vacuum test is ready for use in the same large chamber as was
used for the EM test. However, said large
chamber will not be available starting in October, due to maintenance and/or
upgrade. Instead, a smaller chamber
without a cold shroud will be used, together with a thermal plate for
temperature control. Therefore, some GSE
needs to be redone. Nicola is discussing with Alenia
on TQCM costs. The rental for just a few
days is something like 10k euro. He is
now looking into purchasing one. He will
contact Jack about vendors and lead times.
Jeff Tice reported on shipments:
He is ordering the compression pads
as noted above, with a 2 week turn-around.
He ordered 10 of each. A sample
will go to Sandro via Fed-Ex by mid next week.
Going out from SLAC to
Outer container: the
Jeff has 10 data loggers. SLAC needs to send at least 1 to
Jeff needs to procure rolls of ESD
sheets for bagging. Also, desiccants
need to be ordered.
Emilio said that he needs correct
screws for the corner brackets. Jeff
said that they are on backorder.
Persis asked when can
we schedule reviews of the new procedures. Sept 17.
Review of the Tower-Assembly PRR
action items. Status is in italics
below:
Action
Items from the
1)
Peter
A. to provide Emilio LATDOC numbers (Qty. 4) for CMM Inspection Procedure, CMM
Tower Measurement Software Program, CMM Tower Baseplate
Measurement Software Program, CMM Tower & Baseplate
Assy. Measurement Software Program.
Done
2)
David
Tackes (CMM consultant for SLAC) to provide CMM
Inspection Procedure and (qty. 3) CMM software programs for release to LATDOCs. These items
will then be provided to INFN for use on Tower A
Alignments.
Dave will hand carry these with him
3)
Martin
Nordby to distribute remaining engineering design drawings for review/release.
Martin: many are in the release cycle. Need sign-off from Sandro on several. Only 2 drawing not yet submitted: new bracket
for cables and ground configuration assembly.
They will go out middle of next week.
4)
INFN
to analyze Burn-in test fixture (MGSE dark box) and determine if TEM/PS heat
can be dissipated by current design or if baffled-vents (or other means) needs
to be added to reject heat.
Nicola Saggini: he did a small thermal
model. 12 + 16 watts poses no problem if
the air is changed each ˝ hour or so.
This will assure that the temperature remains less than 30C. Martin Cautioned to make sure that there is no
risk from a fan or air supply turning off.
Robert cautioned about feeding dry air into the box (ESD concerns). Nicola said that they will also couple the baseplate to the dark-box walls. He will send out a drawing, and the details
will be captured in the procedure.
5)
Martin
is to check with J. Ku about the status of stress analysis of turn-over
fixture. J. Ku is to review and approve INFNs proof load requirements and procedure so INFN can
proceed with proof-load test.
Emilio sent all documentation to John and waiting for
answer. He needs a go-ahead by next week
from John. Dave will follow up.
6)
INFN
is to ensure that tooling and fixture drawings are under configuration control
and that the critical lifting hardware drawings are approved by SLAC (John Ku).
A configuration control system
is not really in place in
7)
Emilio
to forward Long Post Fixture and X Lifting Fixture (two configurations)
designs, stress analysis and proofload requirements
and/or results to J. Ku for review and approval.
Same as above: Dave will follow up.
8)
J.
Tice to ship flight materials, MGSE, and EGSE to INFN immediately. Partial shipment of H/W is acceptable. Do not wait for all items to arrive. Ship what we have on-hand and sent subsequent
items when they are delivered to SLAC.
See status above.
9)
A.
Scholz to hand-carry Grid I/F hardware.
(Studs and Hex Bushings are having Nytemp and Dicronite
surface treatment installed.)
Done
10)
A.
Scholz to bring Flex Cable mock-up H/W, Cable samples, transfer adhesive, and
Cable bending tool to INFN and conduct training with INFN before flight cables
are bent for installation.
Done
11)
M.
Nordby to re-send the Sidewall specification (which has been updated by Martin
with his comments) to Riccardo, Sandro, Nanda, and
Robert. Riccardo
is to review this and update/finalize the specification.
Riccardo will work on
this tomorrow.
12)
INFN
to provide copy (hardcopy or softcopy) of Tower Assembly Flow (from INFN
database) and detailed travelers to Darren Marsh for review.
Giovanni is collecting this information.
13)
INFN
to provide detailed kitting list of parts and materials for Tower A Assembly. Indicate
which items they have on-hand, and indicate which items they expect from
SLAC. This is to help ensure that no
items have been inadvertently missed that could cause hit to assembly/test
schedule. Provide list to David Rich,
Jeff Tice, and Robert Johnson.
A spread sheet is on the
14)
TBD. Luca is looking into getting somebody in
15)
INFN
is also to ensure that equipment (electrical and mechanical) calibration and
proof-test records are current and maintained, to be prepared in case of an
audit.
done
16)
INFN
to measure heat straps and bottom tray and determine whether the heat straps
will be properly "sandwiched" between bottom tray and sidewalls to
ensure proper heat transfer without addition of epoxy. A final
decision on this assembly must be reached and documented both in the procedures
and drawings.
TBD
17)
INFN
is to conduct engineering evaluation (and talk with Jeff Tice on his
experience) of application, cure time, and removal/reinstallation of Solithane
for use on sidewall fasteners. Execute
some tests, possibly using the EM. The
torque pattern is to be written in the procedure.
See discussion of Solithane above.
18)
Martin:
inform Emilio of the rationale for choice of adhesive for mounting the top
corner brackets? INFN: review whether
the schedule is compatible with the room-temperature cure time needed for the
adhesive.
done
19)
J.
Tice: Provide specifications and results of drop test for the old style outer
shipping container (conducted by T. Borden).
The old style outer shipping container will probably be used for ground
transportation within
Jeff will talk to Borden.
20)
Luca
to distribute LAT-TD-00191 to team for review.
done. One more turn before sending to Natalie for
release.
21)
D.
Rich to schedule MRB to address open NCRs, provide
written dispositions before proceeding with Tower A
assembly/test. The date for this MRB is
dependant on direction from GLAST Project management concerning Tower A.
Scheduled for next Monday.