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 ; Aldo noted that the up-to-date NCRs
are on the
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:
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.
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.)
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.
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
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.
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.
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.
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
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.