ATLAS Pixel Detector Support Structure Status and Future Developments February 19, 1999

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

4. Frame Concept • Flat Panel Frame Assembly • Disk Regions-2 • Central Region-1 • End cones-2 Frame cutouts Frame corner connections

5. Frame Size Current Studies Based on 250mm Outer Radius

6. Frame Issues Solution to Dynamic and Static Stiffness • 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. Flat Panel Frame Static Solution with High Modulus Fiber(Typical of XN80, P120, or K13C2U) • 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

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

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

11. Flat Panel Frame FEA Comparison Between Structures(For Light WeightingIn Center Panel Only) Frame modifications needed to meet design goals

12. Flat Panel Frame Solutions with High Modulus FiberWith All Cutouts Included(Typical of XN80, P120, or K13C2U) • 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

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

14. Flat Panel Frame Solutions with High Modulus Fiber Light-weighted Frame (Typical of XN80, P120, or K13C2U)

15. Flat Panel Frame Proposed End Reinforcement(Added after Disk Installation) • 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

16. Flat Panel Frame End Tubular Frame Connection • 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. Flat Panel Frame Solutions with High Modulus FiberWith End Reinforcement(Typical of XN80, P120, or K13C2U) • 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

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

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

20. Flat Panel Frame FEA Summary for Light Weighted Structure(End Flat Panel Structure 0.6mm facings)

21. Flat Panel Frame Summary Remarks on FEA • 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.

22. Pixel Support A Concept for the SCT/Pixel Mounting Interface • 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)

23. Pixel Support Restraint at Corners Vary 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

24. Disk Support A Concept For Disk Ring 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

25. Disk Support Disk Support Ring Retention • 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 sandwich ring V-groove spherical ball spring keeper

26. Disk Support Disk Ring Position Adjustment • 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

27. Frame Prototype Objective: Test Frame and Support Interactions • 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

28. Frame Costs Process of Establishing Fabrication Cost Estimate • 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

29. 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

30. Design Data What is Needed to Finalize Frame Design • 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??

31. Milestones Outer Frame Development • 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

32. Frame Costs High Modulus Laminates(Cost on Bulk Basis) 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/#

33. Frame Costs Preliminary Cost Summary

34. Mass Summary Sample Mass Breakdown for Frame Study