BTev Pixel Detector. Mechanical Prototypes and FEA

1
BTev Pixel Detector. Mechanical Prototypes and FEA

• Alexandre Toukhtarov
• Fermilab,
• PPD / Mechanical Department

2
Introduction

• The goals of this presentation are
• to explain prototype work, that is done
• to explain results of FEA for some detector
  components

3
Prototype of Support Half- Cylinder

• The goal of this prototype work was the
  verification of manufacturing and assembly
  technology and procedure
• Prototype has about 1/3 of the real cylinder
  length and correct cross section sizes
• Each prototype component has specified by design
  carbon fiber ply layout

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Half- Support Cylinder
5
Dave Butler Demonstrates His Work
One shell is ready to go.
The ribs are cut out from this blanket.
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Another Half- Cylinder Photos
Half- Cylinder Skeleton
Assembled Half- Cylinder Prototype
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Prototype work results and future planes

• During manufacturing and assembly work no
  problems were discovered
• Future plan includes
• designing and manufacturing of the special
  fixture to make more half-cylinder assembly more
  precise
• making a full-length prototype to verify assembly
  fixture work and taking a measurements of the
  half-cylinder mechanical strength

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Prototype of Pixel Half- Plane Support Brackets

• The goals of this work were
• The verification of manufacturing and assembly
  technology and procedure
• Definition of bracket mechanical strength by load
  test and comparison load test results with FEA
  prediction.
• Prototype has real size, each prototype component
  has specified by design carbon fiber ply layout

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Support Bracket Prototype Parts and Manufacturing
Tools
Manufacturing Tools
Some Parts of Support Brackets
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Assembled Half- Plane Prototype
Two Installed Half- Plane Prototypes
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Half- Plane Installation
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General Notes On Half- Plane Support Brackets
Load Test

• Known loads were applied at known points on half-
  plane dummies
• Tooling balls on half- plane dummies and support
  half- cylinder prototype were used to measure
  deformations in support brackets
• Tooling ball displacements were compared with FEA
  predictions

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Jorge Montes Teaches CMM to Take Measurements
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Close Look on One of the Half- Plane
Sphere 23
Sphere 37
Load
Sphere 21
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Excel Charts With Some Results for Spheres 21
and 23
Sphere 21
Sphere 23
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Prototype of Pixel Half- Plane Support
BracketsMain Results and Future Plans

• During manufacturing and assembly work no big
  problems were discovered, however some
  manufacturing and assembly improvements are
  required
• Measurement result for only one load direction is
  presented. The results for another load
  directions are far away from FEA prediction.
  There is an understanding of a reason for such
  big error. An improvement of half- cylinder
  fixation is required. An another set of load
  tests will be conducted.

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RF- Shield FEA. General Notes.

• RF- shield material is aluminum.
• Thickness of central portion is 0.10 mm, outer
  elements made of 0.50 mm thick aluminum.
• 0.133 pa (10e-03 torr) pressure from detector
  side was applied, gravity was taken into account.

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RF- Shield
100 micron aluminum foil
100 microns aluminum foil
500 microns aluminum foil
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Displacement Plot for 0.133 Pa (10e-03 torr)
Pressure
0.019 mm
0.008 mm
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Von Mises Stress Plot for 0.133 Pa (10e-03 torr)
Pressure
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RF- Shield Main FEA Results

• Main factor for definition about RF-shield design
  acceptance is displacement and not stress
• Present RF-shield design has negligible
  displacements for 0.133 Pa (10e-03 torr)
  pressure. So for required 0.0133 Pa (10e-04 torr)
  pressure foil thickness in theory can be reduced.
• But, because of FEA uses an ideal RF-shield
  model, bigger displacement is expected for real
  part. Another argument against thickness
  reduction is possible manufacturing difficulties.
  

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RF- Shield Future Plans

• Because of complex geometry, RF- shield requires
  extensive manufacturing prototype work,
  especially for its central portion.
• So far, two methods of central portion
  manufacturing have been considered
• super plastic aluminum forming (one aluminum
  sheet is gradually formed with some intermediate
  heat treatments). Just to mention it, LHCb
  silicon detector team successfully uses such
  technology
• welded design (a few pieces formed separately and
  welded together afterwards)
• We are going
• to make some welded prototypes at Fermilab
• to find out an US company or companies
  interested to make RF- Shield by means of plastic
  forming

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RF- Shield Future Plans(Continuation)

• Just to mention it, we understand, that the
  RF-shield has some negative influence on the
  beam. Calculations and prototype cross-check
  measurements are needed. We got some preliminary
  calculation results. These results basically say,
  that RF- Shield has no significant impact on the
  beam. However an additional, more detailed
  calculations are required.
• We will also study the EMI effects on the readout
  electronics and whether the shielding is
  sufficient

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Vacuum Vessel PC- Board Back Plates FEA.
General Notes

• The main goal of FEA is define displacement
  of Vacuum Vessel in places were Half- Detector
  Actuators attached
• Vacuum Vessel and Back Plate made of stainless
  steel
• Simple shell models used
• Back Plate connected to vacuum vessel by means of
  shoulder screws
• Atmospheric pressure and load from known detector
  components applied to Vacuum Vessel PC- Board
  Back Plates

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Second Half- Detector Is Installed Into the
Vacuum Vessel
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Pixel Detector Vacuum Vessel
Material Stainless Steel Total weight 550 kg
(1210 Lbs)
25 mm
25 mm
30 mm
30 mm
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Vacuum Vessel PC- Board Back Plates
Vacuum Vessel. Made of 25-30 mm Stainless Steel
Plates
PC- Board Back Plate. Made of 13 mm thick
Stainless Steel Plate
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Vacuum Vessel PC- Board Back Plate Shell Model
Vacuum Vessel. Made of 25-30 mm Stainless Steel
Plates
PC- Board Back Plate. Made of 13 mm thick
Stainless Steel Plate
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Displacements Plot. Overall View
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Displacements Plot. Vacuum Vessel Top Plate
Actuator Positions
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Displacements Plot. Vacuum Vessel Bottom Plate
Actuator Positions
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Vacuum Vessel PC- Board Back Plates
FEA.Results and Future Plans

• Displacements and stresses are small, however,
  because the shell model is used, bigger
  displacements and stresses are expected
• Future plans
• More accurate 3d FE model will be created
• FEA will be mainly directed on an optimization of
  the design and a reduction of the Vacuum Vessel
  weight

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Conclusion

• The Pixel Detector is complex system, but only a
  few components are mentioned in this presentation
• We understand, that extensive engineering and
  prototyping work for each subsystem and component
  is required