LBNL Pixel Support Study 1

1
ATLAS Pixel DetectorSupport Structure
StatusandFuture DevelopmentsFebruary 19, 1999

• W. Miller
• HYTEC

2
Meeting Topics

• Review frame design status
• Recent FEA results and plans
• Discuss trade-off of sandwich core materials,
  carbon foam versus honeycomb
• in terms of performance
• definite cost impact
• Discuss prototypes for testing and test
  objectives
• Frame components
• Frame sub-assembly

3
FEA Studies
Work Completed
Nearing completion
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Frame Concept

• Flat Panel Frame Assembly
• Disk Regions-2
• Central Region-1
• End cones-2

Frame cutouts
Frame corner connections
5
Current Studies Based on 250mm Outer Radius
Frame Size
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Solution to Dynamic and Static Stiffness
Frame Issues

• Problems confronting developing a reasonable
  solution
• Minimum mass and radiation length requirement
  must be preserved
• Envelope more or less fixed
• limits options for solving dynamic stiffness
  issue
• To avoid over constraining detector that causes
  undesirable strains the lateral restraint of
  detector must be limited to two points
• occurs at the extreme ends of the frame
• lateral reactions to acceleration type loads
  produce purely radial reaction, direction of
  lowest stiffness due to load concentration
• Frame studies focusing on
• Frame construction details to achieve 70 to 100
  Hz natural frequency in lateral direction
• Gravitational sag less than 10µm

7
FEA Results
Example Frame Without Cutouts, No Corner
Effects (Both XN50 and Higher Modulus Fiber
Option)

• Notice that substantial stiffness comes from
  using end rings
• increased core stiffness produces 7 effect,
  with XN50

8
Static Solution with High Modulus Fiber(Typical
of XN80, P120, or K13C2U)
Flat Panel Frame

• Model parameters
• Facings high modulus fibers, e.g., XN80, P120,
  and K13C2U
• Core 68.1kg/mm2 (97000psi, Hexcel 3/16 core
  size)
• 2 radial end plates, separated by 25 mm, bounded
  by sandwich facings. Double facing thickness
  between 25mm spacing (0.6mm)
• Total mass of structure and pixel detector
  38.38kg
• Loading 1G vertical
• Peak deflection 6.07?m, more or less uniform
  along length

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Static Solution with High Modulus FiberIncluding
Corner Effects(Typical of XN80, P120, or K13C2U)
Flat Panel Frame

• Model parameters
• Transverse connection at individual frame
  sections limited to 8 corner points
• Core 68.1kg/mm2 (97000psi, Hexcel 3/16 core
  size)
• 2 radial end plates, separated by 25 mm, bounded
  by sandwich facings. Double facing thickness
  between 25mm spacing (0.6mm)
• Total mass of structure and pixel detector
  38.39kg
• Loading 1G vertical
• Peak deflection 7.28?m at mid-section

Frame sections
Load transfer at corners only
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Solutions with High Modulus Fiber(Typical of
XN80, P120, or K13C2U)
Flat Panel Frame

• Model parameters
• Transverse connection at individual frame
  sections limited to 8 corner points
• Core 68.1kg/mm2 (97000psi, Hexcel 3/16 core
  size)
• 2 radial end plates, separated by 25 mm, bounded
  by sandwich facings. Double facing thickness
  between 25mm spacing (0.6mm)
• Centerframe light weighted
• Solution static and dynamic
• Peak deflection 10.2?m at mid-section
• 1st mode 46.66Hz

Dynamic 46.66 Hz
Static 10.2mm
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FEA Comparison Between Structures(For Light
Weighting In Center Panel Only)
Flat Panel Frame
Frame modifications needed to meet design goals
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Solutions with High Modulus FiberWith All
Cutouts Included(Typical of XN80, P120, or
K13C2U)
Flat Panel Frame

• Model parameters
• Transverse connection at individual frame
  sections limited to 8 corner points
• Core 68.1kg/mm2 (97000psi, Hexcel 3/16 core
  size)
• 2 radial end plates, separated by 25 mm, bounded
  by sandwich facings. Double facing thickness
  between 25mm spacing (0.6mm)
• Entire frame light weighted, total mass 36.9 kg,
  including detector elements
• Solution static
• Peak sag of outer barrel, 13µm
• Peak sag overall, 16.3µm

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Solutions with High Modulus Fiber(Typical of
XN80, P120, or K13C2U)
Flat Panel Frame

• Model parameters
• Transverse connection at individual frame
  sections limited to 8 corner points
• Core 68.1kg/mm2 (97000psi, Hexcel 3/16 core
  size)
• 2 radial end plates, separated by 25 mm, bounded
  by sandwich facings. Double facing thickness
  between 25mm spacing (0.6mm)
• Entire frame light weighted, total mass 36.9 kg,
  including detector elements
• Dynamic solution
• fundamental mode, 38.03 Hz

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Solutions with High Modulus Fiber Light-weighted
Frame (Typical of XN80, P120, or K13C2U)
Flat Panel Frame
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Proposed End Reinforcement(Added after Disk
Installation)
Flat Panel Frame

• Tubular end truss
• Demountable
• Does not block passage of services to any great
  extent
• Tubes are 10mm OD with a 0.6mm wall, composite
  construction similar to longitudinal members

Tubular members tie into longitudinal tubes
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End Tubular Frame Connection
Flat Panel Frame

• Geometry of end piece
• Concept depicted is an illustration
• Details of end piece need to be worked out
• Construction feature will incorporate some
  light-weighting
• Pin connection will have zero clearance feature
  to remove play

17
Solutions with High Modulus FiberWith End
Reinforcement(Typical of XN80, P120, or K13C2U)
Flat Panel Frame

• Model parameters
• Transverse connection at individual frame
  sections limited to 8 corner points
• Core 68.1kg/mm2 (97000psi, Hexcel 3/16 core
  size)
• 2 radial end plates, separated by 25 mm, bounded
  by sandwich facings. Double facing thickness in
  disk region
• 4-10 mm dia. corner end beams reinforcements,
  0.6mm wall
• Entire frame light weighted, total mass 37.53 kg,
  including detector elements
• Static solution
• Gravity sag, 10.43mm

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Solutions with High Modulus FiberWith End
Reinforcement(Typical of XN80, P120, or K13C2U)
Flat Panel Frame

• Model parameters
• Transverse connection at individual frame
  sections limited to 8 corner points
• Core 68.1kg/mm2 (97000psi, Hexcel 3/16 core
  size)
• 2 radial end plates, separated by 25 mm, bounded
  by sandwich facings. Double facing thickness in
  disk region
• 4-10 mm dia. corner end beams reinforcements,
  0.6mm wall
• Entire frame light weighted, total mass 37.5 kg,
  including detector elements
• Dynamic solution
• fundamental mode, 77.5 Hz

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Solutions with XN50 LaminatesWith End
Reinforcement(illustrate effect of lower modulus
laminate)
Flat Panel Frame

• Model parameters
• Transverse connection at individual frame
  sections limited to 8 corner points
• Core 68.1kg/mm2 (97000psi, Hexcel 3/16 core
  size)
• 2 radial end plates, separated by 25 mm, bounded
  by sandwich facings. Double facing thickness in
  disk region
• 4-10 mm dia. corner end beams reinforcements,
  0.6mm wall
• Entire frame light weighted, total mass 37.53 kg,
  including detector elements

Gravity sag increased to 16.4mm
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FEA Summary for Light Weighted Structure(End
Flat Panel Structure 0.6mm facings)
Flat Panel Frame
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Summary Remarks on FEA
Flat Panel Frame

• Reinforcements to the very ends of the frame
  produced positive results in raising the first
  vibration mode--with kinematic mounts
• 77.5 Hz for frame with ultra-high modulus
  composites
• Drops to 66.46 Hz for XN50, and 0.6mm laminate
  facings at end sections
• gravity sag increases from 10 to 16.4 mm
• Eliminating the end reinforcements-with XN50
  composite
• Gravity sag increases from 16.4 to 17.7 mm, small
  effect
• Resonance drops to 36.7 Hz if we eliminate the
  reinforcements
• Resonance would decrease further if we use 0.3mm
  facings on the end sections---30.99Hz
• Clear benefit to reinforcements at frame ends
• Increased facing thickness on ends is beneficial,
  as is the use of higher modulus laminates.

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A Concept for the SCT/Pixel Mounting Interface
Pixel Support

• Desirable attributes for mount
• kinematic to extent practical
• Four point support
• 1 point XYZ
• 1 point XY
• 2 points Y
• All support points are adjustable vertically
• Pixel frame reinforced locally to resist lateral
  loads
• Issues
• Need to be assured that SCT channel design is
  fixed in geometry and stable
• Look into pixel frame reinforcements and mount
  materials

40mmX10mmX3mm SCT mounting channel
(must be replaced with end plates)
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Restraint at Corners Vary
Pixel Support
lock

• Mount concept
• Vertical adjustment for leveling detector
• Conical seat and V-groove track at opposite end
  position detector laterally
• Restrains X and Z, and rotation about vertical
  axis
• Simple flat contact permits movement in X and Z
• Considerations
• SCT support dimensional accuracy
• to what extent can we rely on location of
  channel?
• Must we shim?

Vertical adjustment
cone
flat
Section views
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A Concept For Disk Ring support
Disk Support

• Mount considerations
• To avoid excessively tight frame assembly
  tolerances, we machine and locate precision
  inserts
• Bushings are bored after bonding
• this fixes the azimuthal and Z location for
  V-groove receivers, within 10µm, possibly better
• Three V-groove blocks are positioned and bonded
  to bushings
• fixture used in bonding the V-groove receivers.
  ? positional tolerance can be improved by using
  bond clearances to an advantage if necessary
• three precisely located balls on the fixture
  locate the V-grooves radially, and rotationally

Disk support ring mounts
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Disk Support Ring Retention
Disk Support

• Assembly sequence
• Disk assembly inserted into frame
• Spherical balls on mounting ring are placed onto
  three V-grooves
• Spring keeper inserted from outside to restrain
  spherical ball in V-groove
• Spring keeper is guided by the machined bushing
  bonded in the frame structure and fixed in place
  on the outside of the frame
• Considerations
• Required spring force to resist movement of disk
  from extraneous forces caused by services
• Material selection

V-groove
sandwich ring
spherical ball
spring keeper
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Disk Ring Position Adjustment
Disk Support

• Adjustment features
• R-? disk position is obtained by precise location
  of three point ball support in three V-grooves
• Final positioning of disk provided by adjustment
  screw (fine thread)
• Adjustment screw provides pure axial motion, as
  well as tip/tilt
• Considerations
• Material selection of individual components
• use composite materials to extent practical
• to what extent metallic (Be) elements are desired
  is unclear at this time
• Demonstrate zero backlash at component level

adjustment screw
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Objective Test Frame and Support Interactions
Frame Prototype

• Prototype test considerations
• Frame performance is strongly influenced by the
  stiffness in the end sections
• Local stiffness of the frame dependent on frame
  internal reinforcements
• Testing with the end section will investigate
  adequacy of this reinforcement, as well as the
  general performance of the lightweight structure
• Test of interface connection of the central frame
  will also be covered

For test remove SCT mount
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Process of Establishing Fabrication Cost Estimate
Frame Costs

• History
• 1st cost estimate covered a comparison between
  tubular frame and flat panel
• Lower projected cost favored the flat panel
• Conclude that even with refinements to both
  designs that this conclusion would remain
  unchanged
• Flat panel costing
• Proceeded to obtain additional cost information
  with modified drawing set--solicited bids from 3
  vendors
• Vendors were advised we were still refining the
  structural aspects and design changes must be
  anticipated
• Our objectives were to
• Break down costs for NRE, tooling materials, and
  fabrication labor

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Where are We?

• Analysis
• Must complete frame FEA to evaluate overall
  effect of frame light weighting on performance,
  and support point reinforcement
• Need to focus on panel joint designs and SCT
  support interactions with FEA
• FEA of disk structure to include effects of mount
• Prototype frame
• Need to decide on end section material
  thickness, fiber choice, and core material
• Complete preliminary construction drawings, joint
  connections
• Costing
• Solicited pricing information from 3 vendors to
  common definition
• Met with 3 vendors and discussed their proposal
• Selected lowest bidder and requested formal
  prototype quote
• Fixed cost quote was based on performing effort
  in 3 phases
• Prepared to go ahead with this effort-some
  discussion still pending

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What is Needed to Finalize Frame Design
Design Data

• Solidify Pixel/SCT interface to complete frame
  design and analysis
• Insertion rail design envelop in sufficient
  detail
• frame attachments, method of transfer from rail
  to SCT, etc.
• Confirmation on SCT/Pixel mount interface-
  channel design?
• structural robustness
• dimensions, positional reference?
• material
• Refinement to our proposed Pixel to SCT mount
• Factor design into frame prototype testing
• Coolant line, manifold design, and cable routing
• Develop understanding of possible extraneous
  loads on disk assembly
• Recommend early prototype tests of
  tubing/manifolds to validate design of coolant
  system
• Heat shield effects??

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Outer Frame Development
Milestones

• Decision on prototype core material---------------
  ---- 1/30/99
• Decision on fiber material------------------------
  ---------- 2/19/99
• FEA of panel cut-outs complete--------------------
  ----- 2/28/99
• Release drawings for LBNL mock-up-----------------
  - 1/30/99
• Order pre-preg material---------------------------
  ---------- 2/22/99
• Order core material-------------------------------
  ------------ 2/22/99
• FEA of reinforced corner (1st mode
  problem)-------- 3/30/99
• TVH with new environmental enclosure--------------
  -- 3/01/99
• 1st sandwich panel--------------------------------
  ------------ 5/15/99
• Evaluation of 1st panel without/with
  cutouts--------- 5/30/99
• Full scale prototype complete---------------------
  -------- 9/15/99
• Preliminary stiffness tests complete--------------
  ------ 10/15/99

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High Modulus Laminates(Cost on Bulk Basis)
Frame Costs
ALLCOMP proposes P30 fiber carbonized/heat
treated to equivalent 22 Msi, resin impregnated,
as replacement to above resin based composites.
At 25, cost per lb is 500/
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Preliminary Cost Summary
Frame Costs
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Sample Mass Breakdown for Frame Study
Mass Summary