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GLAST:Gamma Ray Large Area Telescope

GLAST:Gamma Ray Large Area Telescope. Ladders, Trays and Towers Construction A.Brez INFN - sez. Pisa. Construction program. Pre-engineering model tower (2001) Engineering model tower (february-july 2002) Qualification tower 17 flight towers (16+1spare)

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GLAST:Gamma Ray Large Area Telescope

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  1. GLAST:Gamma Ray Large Area Telescope Ladders, Trays and Towers Construction A.Brez INFN - sez. Pisa

  2. Construction program Pre-engineering model tower (2001) Engineering model tower (february-july 2002) Qualification tower 17 flight towers (16+1spare) The pre-engineering tower is now ready and it will be tested next week at SLAC

  3. Purpose of the pre-engineering tower: • Experimental validation of the mechanical project (drawings and materials) • Experimental validation of the tray assembly procedure • Qualification of the tray producers (PCI California, Plyform Italy) • Experimental validation of the tower assembly procedure • Dynamical test of the trays (vibrational) • Thermal test of the trays • Dynamical test of the tower (vibrational) • Different procedures of tray and tower assembly have been developed: • US procedures more close to the BTEM experience • Italian procedures with more attention to the large series production • Italian efford: • superGLAST (W=18%Xo) payload study • Production of 4 superGLAST trays • Tray vibrational test • Production of 1 GLAST (W=3%Xo) tray

  4. Hytec (Los Alamos- New Mexico) tray assembly scheme developed in collaboration with PCI (Ontario, California) Hytec tray assembly strategy: Gluing at 120oC face-sheets, honeycomb and closeouts with a monolithic graphite tool. There are problems due to the CTE mismatch between graphite and Carbon-Carbon Complicate tool, hard to control it.

  5. Assembly procedure guideline used in Plyform: Structural gluing of the face sheets with the honeycomb under moderate pressure (0.2atm) at high temperature (Redux 312 UL, 100g/m2 foils, cured at 120oC) Room temperature gluing of the closeouts (Redux 420 AB) References holes used for tray assembly and for subsequent alignments situated on the closeout

  6. TRAY ASSEMBLY JIG BASE COVER

  7. FEM of the tray assembly jig

  8. SuperGLAST tray without payload M2.6 thread holes M2.6 thread holes F3 reference holes The Engineering Model trays will be done with fully Carbon-Carbon closeouts, without the Al particulars

  9. Planarity of the GLAST tray #0 produced by Plyform Vacuum bag differential pressure = 0.2Atm

  10. *** WBS 4.1.4 TRACKER (R. Johnson) TKR Mechanical * The stacking test and measurements on the PCI carbon- composite trays showed that the jigging as used at PCI did not hold the dimensional tolerances sufficiently well. Those trays will be machined slightly to fix them up for further tests. * The room-temperature cure method and jigging used at Plyform (the intended fabrication vendor for engineering model and flight panels) does appear to hold tolerances sufficiently well, based on 3 trays measured. ---------------------------------------------------------------- MCM side CMM measurements of the sides of the tray mean dimensions= 368.589 mmX368.586 mm +0.038 -0.034 +0.066 -0.037

  11. The tungsten gluing tool has 16 vacuum pockets to align the tungsten plates The glue is deposited both on tray and on tunsten plates. The tray is aligned by means of dowels. A 0.2Atm pressure is applied over the tray.

  12. Kapton bias circuits gluing tool 1: alignment of the 2 kapton bias circuits on 2 vacuum chucks and glue deposition 2: alignment of tray over the bottom chuck 3: gluing at room temperature of the two circuits together in a reduced vacuum bag (0.2Atm)

  13. Assembly of the ladders over the tray bridge handle guide Z micrometers shoulder bridge pins tray pins

  14. Assembly of the ladders on the trays Transfer bridge Ladder assembly tool

  15. Problems: the ladder assembly jig is not safe for this purpose : the ladder rubs the reference walls when it is lift on. The friction can cause the lost of the vacuum fixation of the ladder which can move without control A new alignment tool is under project

  16. Need to have a better control of the parallelism and of the distance of the two silicon layers

  17. Tower assembly procedure: US proposal An assembly tests has been performed at SLAC during PDR using BTEM assembly concept: Each tray has f2mm precision holes on the 4 corners 4 corner posts refer one tray respect to the subsequent one The posts define the height and the horizontal position of the trays in the space The side wall are added at the end Corner posts h f2mm Alignment errors pileup even with very demanding requirements on the tolerances, the final alignment is poor

  18. Italy assembly concept: Refer the trays to the side walls of the tower. The side walls are Carbon fibre plates, 1.5mm thick. On the side walls there are holes for the screws and precision holes in correspondence with the reference holes on the tray closeouts. Each tray is referred to the side walls reference system independently of the other trays z Pre-assembly of the tower in open condition: The trays are hold and positioned by the 2 reference walls. Two sides are completely free On the other two sides the slots of the reference walls allow full cabling x y

  19. Stop pins: 4 pins on the corners avoid accidental contacts between the trays Reference pins: 3 pins define the height and the position of the tray in space The tray is screwed against one of the reference walls Reference pin Screwing holes Stop pin

  20. Reference walls of the X side walls When the tower is fully assembled, cabled and tested, two reference walls put in place the first two side walls. The trays are referred and fixed to the carbon fibre side walls The reference walls with the slots are removed The last 2 side walls are put in place with other 2 reference walls

  21. Tower assembly and vibrational test: SLAC 20-28 february The components of the pre-engineering tower have been produced: Top, bottom and 4 GLAST trays made by PCI following the Hytec assembly procedure 9 Aluminium mass models (trays with Al closeouts, honeycomb and face-sheets, with similar mechanical properties) produced by SLAC 4 superGLAST trays produced by Plyform following the INFN assembly procedure This week a full assembly exercise of the tower will be carried out at SLAC The week after the tower will be shaked

  22. Conclusions A prototype of the engineering tower is ready to be mounted The engineering of two ladder production lines (G&A,Mipot) and of one tray assembly line (Plyform) has been completed successfully Open questions: QA of the tray assembly line not yet developed. Engineering Model : CMM measurements in INFN Dynamical tests: in Centrotecnica (samples) + qualification (all trays) Need to develop a light system to check dinamically the workmanship at different levels (search of main resonance modes)

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