GLAST:Gamma Ray Large Area Telescope

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GLASTGLAST GLASTGLAST Pisa GLAST Italia meeting, 18/02/02 A.Brez – INFN Pisa

GLAST:Gamma Ray Large Area Telescope

Ladders, Trays and Towers Construction

A.BrezINFN - sez. Pisa

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Pre-engineering model tower (2001)Engineering model tower (february-july 2002)Qualification tower17 flight towers (16+1spare)

The pre-engineering tower is now ready and it will be tested next week at SLAC

Construction program

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Purpose of the pre-engineering tower:1. Experimental validation of the mechanical project (drawings and materials)2. Experimental validation of the tray assembly procedure3. Qualification of the tray producers (PCI California, Plyform Italy)4. Experimental validation of the tower assembly procedure5. Dynamical test of the trays (vibrational)6. Thermal test of the trays7. Dynamical test of the tower (vibrational)

Italian efford:1. superGLAST (W=18%Xo) payload study 2. Production of 4 superGLAST trays3. Tray vibrational test4. Production of 1 GLAST (W=3%Xo) tray

Different procedures of tray and tower assembly have been developed:1. US procedures more close to the BTEM experience2. Italian procedures with more attention to the large series production

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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-CarbonComplicate tool, hard to control it.

Hytec (Los Alamos- New Mexico) tray assembly scheme developed in collaboration with PCI (Ontario, California)

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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

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Walls housing

Face-sheet reference pinholes

Plates reference pinholes

Bars fixing holes

BASE COVER

TRAY ASSEMBLY JIG

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FEM of the tray assembly jig

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SuperGLAST tray without payload

The Engineering Model trays will be done with fully Carbon-Carbon closeouts, without the Al particulars

M2.6 thread holes F3 reference holes

M2.6 thread holes

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0 50 100 150 200 250 300

X=-75mm

"X=+75mm"-0.02

-0.015

-0.01

-0.005

0

0.005

0.01

0.015

0.02

Z(mm)

Y(mm)

X(mm)

tray GALST Plyform 0 bottom side

0 50 100 150 200 250 300

X=-75mm

"X=+75mm"-0.02

-0.015

-0.01

-0.005

0

0.005

0.01

0.015

0.02

Z(mm)

Y(mm)

X(mm)

tray GALST Plyform 0 top side

X=-75mm

X=0mm

"X=+75mm"

Planarity of the GLAST tray #0 produced by PlyformVacuum bag differential pressure = 0.2Atm

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Tray #2 thermal boss profiles

-100

0

100

200

300

400

500

600

700

0 50 100 150 200 250 300 350 400

mm

m m

Trey #3 thermal boss profiles

-100

0

100

200

300

400

500

600

0 50 100 150 200 250 300 350 400

mm

m m

Tray #4 thermal boss profiles

-100

0

100

200

300

400

500

600

700

0 50 100 150 200 250 300 350 400

mm

m mTray #1 thermal boss profiles

-100

0

100

200

300

400

500

600

0 50 100 150 200 250 300 350 400

mm

m m

CMM measurements of the sides of the tray mean dimensions= 368.589 mmX368.586 mm

+0.038-0.034

+0.066-0.037

*** 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

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Tungsten plate

Vacuum square pockets

Tray reference pinholes

Tray reference pin

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.

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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)

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bridge

handle

Z micrometers

guide

shoulder bridge pins

tray pins

Assembly of the ladders over the tray

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Transfer bridge

Assembly of the ladders on the trays

Ladder assembly tool

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wafers alignment errors

0

10

20

30

40

50

60

70

mm

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 controlA new alignment tool is under project

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0

89.5

179

268.

5

358

ladder 0

ladder 1

ladder 2

ladder 30

0.10.2

0.30.4

0.5

0.6

0.7

mm

mm

tray #1 superGLAST tray thickness0=nominal thickness (31.034mm)

min=+0.44mmmax=+0.70mm

ladder 0

ladder 1

ladder 2

ladder 3

0

89.5

179

268.

5

358

ladder 0

ladder 1

ladder 2

ladder 3-0.05

0

0.05

0.1

0.15

0.2

mm

mm

tray #4 superGLAST tray thickness0=nominal thickness (31.034mm)

min=-0.02mmmax=+0.20mm

ladder 0

ladder 1

ladder 2

ladder 3

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

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An assembly tests has been performed at SLAC during PDR using BTEM assembly concept:Each tray has 2mm precision holes on the 4 corners4 corner posts refer one tray respect to the subsequent oneThe posts define the height and the horizontal position of the trays in the spaceThe side wall are added at the end

Corner posts

2mm

h

Tower assembly procedure: US proposal

Alignment errors pileup even with very demanding requirements on the tolerances, the final alignment is poor

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z

yx

Pre-assembly of the tower in open condition:The trays are hold and positioned by the 2 reference walls.Two sides are completely freeOn the other two sides the slots of the reference walls allow full cabling

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

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Stop pin

Reference pin

Screwing holes

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

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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 wallsThe reference walls with the slots are removedThe last 2 side walls are put in place with other 2 reference walls

Reference walls of the X side walls

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# Tray type close-out producer19 top Carbon-Carbon PCI18 glast Carbon-Carbon PCI17 glast Carbon-Carbon PCI16 glast Carbon-Carbon PCI15 glast Carbon-Carbon PCI14 Al mass model Al SLAC13 Al mass model Al SLAC12 Al mass model Al SLAC11 Al mass model Al SLAC10 Al mass model Al SLAC

9 Al mass model Al SLAC8 Al mass model Al SLAC7 Al mass model Al SLAC6 superGLAST Carbon-Carbon Plyform5 superGLAST Carbon-Carbon Plyform4 superGLAST Carbon-Fibre Plyform3 superGLAST Carbon-Fibre Plyform2 Al mass model Al SLAC1 bottom Carbon-Carbon PCI

side walls: Carbon-Fibre

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 procedure9 Aluminium mass models (trays with Al closeouts, honeycomb and face-sheets, with similar mechanical properties) produced by SLAC4 superGLAST trays produced by Plyform following the INFN assembly procedure

This week a full assembly exercise of the tower will be carried out at SLACThe week after the tower will be shaked

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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)

GLAST:Gamma Ray Large Area Telescope

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