BeTev%20Pixel%20Detector%20Mechanical%20Design.

1
BeTev Pixel Detector Mechanical Design.

• Alexandre Toukhtarov.
• Fermilab,
• PPD / Mechanical- Department.

2
Introduction.

• The goal of this presentation is
• a) to give an overlook view on BeTev pixel
  detector conceptual design and major steps of
  pixel detector assembly procedure,
• b) to explain prototype work, that is done,
• c) to explain results of FEA for some detector
  components.

3
Mechanical Support System Requirements.

• The Pixel Detector mechanical support structure
  should have low mass within the geometrical
  acceptance (300x300 mrad2) of the spectrometer.
• The detector needs to be retractable to a
  distance of 2 cm from the beam and after each
  refill, the detector has to be moved in position.
  The reproducibility should be better than 50 mm
  and the relative motion must be read out with a
  precision of 1-2 mm. .
• The whole detector will be placed inside the
  aperture of a dipole magnet with a field strength
  of 1.6 T it should not have any effect on the
  magnetic field strength.

4
Mechanical Support System Requirements.
(Continuation)

• The design must take into account that the
  operating temperature of the detector will be on
  the range between 10 degrees C and 5 degrees C.
  
• The detector must be shielded electronically from
  the circulating beam which is a significant rf
  source. Multiple scattering in the rf shielding
  (which also serves as the secondary vacuum
  envelope) and exit plates should be kept to a
  minimum and yet strong enough to withstand the
  differential pressure of 10-4 torr.

5
Mechanical Support System Requirements.(Continuati
on)

• The pressure inside the clean vacuum where the
  colliding beam will go through has to be better
  than 10-7 torr. The differential pressure between
  the clean and dirty (where the pixel
  detector resides) vacuum has to be no more than
  10-4 torr.
• The two halves of the detector must be aligned to
  each other with an accuracy better than 50 mm in
  x and y, and 200 mm in z (longitudinal
  direction).
• The individual half planes must be mounted with a
  precision of 20 microns or better, and the
  positions known to 10 microns before the
  half-planes are inserted in the vacuum container.

6
Mechanical Support System Requirements.
(Continuation)

• The System must include some means of alignment
  monitoring online.
• The system should be stable to within 2 um during
  data-taking.

7
Pixel Detector Conceptual Design and Detector
Assembly Procedure. General Notes.

• 1. Some small fitches like screw holes, screws,
  bolts, washers and nuts omitted.
• 2. Some components have a simplified shape.
• 3. Present design based on using of Be substrate.
  Using of another substrate options will require
  some modifications on detector design.

8
Assembled Half -Plane Support Brackets.
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Half- Support Cylinder.
10
Assembled Half Support Cylinder.
11
Assembled Half Support Cylinder(View From
Another Side).
12
Half- Plane Installation.
13
Half- Plane Installation (View From Another Side).
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30 Half- Planes Are Installed (Only 4 Are Shown).
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30 Half- Planes Are Installed (Only 4 Are Shown).
View From Another Side.
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All Flex Cables Are Attached to PC- Board.
17
Flex Cables Are Attached to PC- Board (Close
Look).
18
Assembled PC- Board. View From Beam Side.
19
Assembled PC- Board. View From Another Side.
20
RF- Shield and Displacement Sensors Are Installed.
21
RF- Shield.

• It made of 150 micron aluminum foil

22
Two Pixel Half- Planes Are In Front of RF- Shield.
23
Pixel Detector Vacuum Vessel.
24
The First Half- Detector Is Inserted Into Vacuum
Vessel.
25
First Half- Detector Is Installed.
26
Second Half- Detector Is Inserted Into the Vacuum
Vessel.
27
Second Half- Detector Is Installed Into the
Vacuum Vessel.
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All Pixel Detector Components Are Installed.
29
Pixel Detector Is Ready for Tests.
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Pixel Detector Is Installed on the SM-3 Magnet.
31
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.

32
Dave Butler Demonstrates His Work.
One shell is ready to go.
The ribs are cut out from this blanket.
33
Another Half- Cylinder Photos.
Half- Cylinder Skeleton
Assembled Prototype of the Half- Cylinder
34
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.

35
Support Bracket Prototype Parts and Manufacturing
Tools.
Manufacturing Tools
Some Parts of Support Brackets
36
Assembled Half- Plane Prototype.
Two Installed Half- Plane Prototypes.
37
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

38
Jorge Montes Teaches CMM to Take Measurements.
39
Close Look on One of the Half- Plane.
Sphere 23
Sphere 37
Load
Sphere 21
40
Excel Charts With Some Results for Spheres 21
and 23.
Sphere 21
Sphere 23
41
RF- Shield FEA. General Notes.

• RF- shield material is aluminum.
• Thickness of central portion is 0.15 mm, outer
  elements made of 0.50 mm thick aluminum.
• Two cases were considered
• Pressure from detector side
• Pressure from detector side.

42
Displacement Plot for 10-04 Pa Pressure.
0.071 mm
0.109 mm
43
Displacement Plot for 10-03 Pa Pressure.
0.71 mm
1.10 mm
44
Von Mises Stress Plot for 10-04 Pa Pressure.
45
Von Mises Stress Plot for 10-03 Pa Pressure.
46
RF- Shield FEA. Main Results.

• Main factor for definition about RF-shield design
  acceptance is displacement.
• Present RF-shield design has acceptable
  displacements for 10-04 Pa pressure.
• FEA made for ideal RF-shield model, so bigger
  displacement is expecting for real part. To make
  decision about final design, the real
  displacement has to be measured on RF-shield
  prototype.

47
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.

48
Shell Vacuum Vessel PC- Board Back Plate Model.
Vacuum Vessel. Made of 25-30 mm Stainless Steel
Plates.
PC- Board Back Plate. Made of 13 mm thick
Stainless Steel Plate.
49
Displacements Plot. Overall View.
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Displacements Plot. Vacuum Vessel Top Plate.
Actuator Positions
51
Displacements Plot. Vacuum Vessel Bottom Plate.
Actuator Positions
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Conclusion

• We are fare away from the detector final design.
• The vacuum and cooling subsystems are not yet
  well defined, it can have a big impact on the
  present design.
• Extensive engineering and prototyping work is
  needed on following detector components
• RF-shield
• Flex cable
• PC- Board
• Substrate-to-Main Manifold flex tube joint
• Most difficult assembly procedure steps
• Assembly fixtures.