GLAST:Gamma Ray Large Area Telescope

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GLASTGamma Ray Large Area Telescope
Ladders, Trays and Towers Construction A.Brez INF
N - sez. Pisa
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Construction program
Pre-engineering model tower (2001) Engineering
model tower (february-july 2002) Qualification
tower 17 flight towers (161spare) The
pre-engineering tower is now ready and it will be
tested next week at SLAC
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• 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 (W18Xo) payload study
• Production of 4 superGLAST trays
• Tray vibrational test
• Production of 1 GLAST (W3Xo) tray

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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.
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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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TRAY ASSEMBLY JIG
BASE
COVER
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FEM of the tray assembly jig
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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
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Planarity of the GLAST tray 0 produced by
Plyform Vacuum bag differential pressure 0.2Atm
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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
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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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Assembly of the ladders over the tray
bridge
handle
guide
Z micrometers
shoulder
bridge pins
tray pins
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Assembly of the ladders on the trays
Transfer bridge
Ladder assembly tool
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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
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Need to have a better control of the parallelism
and of the distance of the two silicon layers
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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
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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
y
x
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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
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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
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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
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Conclusions A prototype of the engineering tower
is ready to be mounted The engineering of two
ladder production lines (GA,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)