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Gamma-ray Large Area Space Telescope. GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 Revisions to Tray Design Robert Johnson Santa Cruz Institute for Particle Physics University of California at Santa Cruz Tracker Subsystem Manager Bottom Tray.
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Gamma-beam Large Area Space Telescope GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 Revisions to Tray Design Robert Johnson Santa Cruz Institute for Particle Physics University of California at Santa Cruz Tracker Subsystem Manager

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Bottom Tray Substantial upgrade: Taller Closeouts produced using M55J/CC overlay Larger M4 embeds in basic areas for sidewall mounting Bonded titanium corner sections 1-piece 3-sharp edge titanium flexures Bonded joint for side flexures Heavy 3-lb center and 6-utilize confront sheets Copper warm straps Assembly: Minor alterations on apparatuses utilized for top-plate get together Closeout dividers and corner sections amassed all the while Drill installation is being made to find the flexures to the Grid Static load test to confirm workmanship of the flexure connection

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Bottom Tray and Interfaces Status: Design finished: every positive edge from FEA. Machined base plate closeouts deliver tomorrow from COI Titanium corner sections and flexures June 2; Static test installation June 9 Drill format for flexure mounting is additionally on the basic way

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Sidewalls YS90 traded by K13D for better warm conduction Prepreg is in Italy for Plyform to start board gathering Short boards are required rapidly for static test apparatus Coupons will be tried to acquire allowables Smallest tower edges are in the sidewall-plate interface Existing edges depend on testing of YS90 coupons M4 Bottom Sidewall Section (M2.5 clasp unless checked generally)

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Mid Trays All EM mid-plate boards have been manufactured and tried A PRR was held at Plyform in mid April See Issues waiting be determined before starting flight generation: Loose carbon particles Grounding of the center Update and endorsement of drawings and techniques Several nitty gritty activity things recorded in the above referenced site page Implementation of the INFN database for board creation Plyform contract is set up and closeout embed acquisition is starting this week

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Carbon Particles EM mid plate carbon-carbon surfaces and trimmed face-sheet edges were passivated by spotting with a thin pitch. We want to use rather the Z-306 non-conductive dark paint, as it can be connected by showering, giving better scope onto surfaces and into corners. This will be tried on the top and base EM plate. The first plan had MCM mounting screws threading into the carbon-carbon. This is being supplanted by a cement joint, and the strung gaps are being substituted by smooth bores for arrangement pins. This change is required with a specific end goal to acquire great arrangement of the wire-holding edge of the MCM (see later slide), yet it additionally evacuates the issue of threading into carbon-carbon. Every other clasp string into additions.

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Carbon Particles One smaller than expected tower plate had a little projection close to the plate edge (conceivably a carbon fiber from the face-sheet edge or from the screw opening) that shorted the high voltage when the establishing screw was fixed. 5-mil 3M exchange cement was not put between the MCM and plate in this district, so this was a deviation from the expected outline However, the new MCM mounting plan replaces the exchange glue by an epoxy joint with under 100% scope The electrical protection issue is being determined by Replacing the rear MCM weld veil with a full-scope layer of Kapton Reducing the unfiltered HV plane to a limited follow and moving the separated HV arranges once again from all edges These have as of now been executed on the new scaled down tower MCMs. The projection that brought on the short could be felt while slipping a bit of plastic behind the MCM and must be further researched when the small scale tower is dismantled.

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MCM Mounting To maintain a strategic distance from Carbon chipping, the MCM will be not mounted by method for M1.6 screws. There will be smooth openings in the closeout, and stuck pins will supplant the screws. The MCM will be attached to the closeout with Scotchweld 2216 A/B dark (nonconductive). A clasping instrument will be utilized to hold set up the MCM while the cement cures. New clipping apparatus jolts to the supplements in the closeout warm supervisor, adjusts to the MCM to 2 sticks, and presses the top edge of the MCM into place to guarantee a straight edge for wire-holding.

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MCM ground opening Pin Nusil 2646 Closeout Grounding The MCM ground will be electrically associated with the closeout utilizing pins with conductive paste as a part of the 3 plated-through ground gaps. Dots of non-conductive paste will keep the conductive paste restricted around the ground gap to expand the electrical seclusion of the Kapton-secured MCM posterior. GND opening

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Core Grounding EM tests exhibited the need great establishing of the conductive plate parts Tray electrical conductivity: Carbon-carbon, carbon-fiber and Aluminum center have great electrical conductivity, yet are associated together with non conductive paste. The outcome is a poor electrical association, 10-100 ohms, from component to component. RFA from the associate audit requires a superior plan than utilized as a part of the present small tower. Additionally, the MCM mounting plan is being altered for different reasons.

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Core Grounding Solution 1) Add to the honeycomb conductive chambers ( gold plated kapton tubes ) stuck with conductive cement Will be tried with 2 EM base plate and 1 EM beat plate. 2) Put conductive paste on the closeout dividers when the plate is amassed, in correspondence to the conductive barrels. Push set up the closeout dividers to pack the barrels

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Backup Core Grounding Solution MCM closeout Structural closeout Tested as of now with existing EM boards. Association wire Groove loaded with conductive paste After the plate is finished, 4 furrows are machined over the MCM-auxiliary closeout dividers. The scores are loaded with a short conductive wire and with conductive paste (Nusil CV2646). The honeycomb is associated with the basic divider trough the venting gap by method for a stuck wire. Venting opening Glue joint Experimental result: all the plate parts (closeouts, confront sheet, honeycomb) are associated with low resistance <1 W.

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Bias Circuits Incremental upgrades to improve plate fabricating: Solid (not incubated) and ¼ oz. Cu (not ½ oz.) shield plane, to encourage sticking to the plate board. Removable top Mylar film to secure the circuit amid get together. Switch Bias and GND associations at the two edges (and on the MCM) to right arrangement with the SSD inclination cushions. Move the GND cushion through far from the holding locale and increment the cushion leeway from the SSDs and from the cut edge. Evacuate limit Cu outskirt at the cut edge (meddled with trimming). These are in no time being checked with a model keep running of the circuit. These models can be utilized on the top/base EM plate.

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Tray Electronics GTFE ASIC (G3 adaptation; 123 wafers close by) Corrected the comparator shakiness issue (no indication of this issue in >20 wafers of chips tested and >100 chips on MCMs and smaller than normal MCMs, including some associated with live steps). Adjusted the planning edge in the enlist readback: with VDD=2.5V we can read enrolls up to 28 MHz. GTRC ASIC (Version 6; 20 wafers close by) Corrected the planning edge in the information readback: with VDD=2.5V we can read information up to around 30 MHz. TOT buffering rectified Parity checking adjusted with the exception of that an information field equality blunder in summons sent to the GTRC is not hailed. 100% wafer test testing of usefulness and I/O ports is in advance on both ICs at 22 MHz and VDD=2.4V. Programmed inking of awful dice. Determinations and seller set up for wafer lapping, dicing, acknowledgment testing, and careful optical investigation.

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MCM PWB No adjustment in schematic or SMT parts situation. Remedy of directing of two flags that required crossed wire bonds in the past adaptation. No other directing changes. Ought to be no change in electrical conduct. IC cushion sizes acclimated to coordinate the flight-creation dice. Kapton cover on the rear for enhanced electrical separation, in addition to diminishment of HV predisposition planes on the posterior. Omnetics connectors: an immense change and GSFC affirmed! Pitch-connector range expanded from 0.64 mm to 1.0 mm, to decrease push. 15 sheets from a late preproduction run are being utilized to make MCMs for the scaled down tower. Incorporate the majority of the above upgrades. Created to the most recent LAT PWB particulars, with all confirmations and coupons close by. One board has as of now been amassed by us and tried.

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MCM Pitch Adapter Removed cover layer Stress riser broke follows Required high exactness arrangement Increased follow length at both closures Trim in the wake of attaching to the PWB Eliminates tight arrangement resistance and guarantees space for wire bonds (greatest wellspring of dead stations in the small scale tower) Move crisscross far from ASICs Facilitates wire holding at Teledyne Increase twist sweep on PWB Reduce shot of split follows Eliminate glass dabs from paste These were clustering and making knocks that broke individual follows 4 new models clung to PWBs at Teledyne with astounding results

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MCM Assembly We are adding another procedure to stake the two substantial tantalum capacitors. Work is in advance to enhance the electrical test program: Faster test execution Better UI Addition of a couple of new tests Better and speedier examination of blunders Assembly of 10 new sheets for the smaller than usual tower is in advance this week. Work is in advance on the agreement with Teledyne; the SOW was just drafted. The primary part of 50 MCMs will be a preproduction run and will incorporate the 36 loads up for the hardware and flight programming bunches.

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Flex-Circuit Cables The principal smaller than normal tower links had a few imperfections that have been settled in the outline: TEM connector on the wrong side of the link Inverted TREQ differential

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