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Beampipe Support Structure VI section within the pixel detector

Beampipe Support Structure VI section within the pixel detector. N. Hartman, E. Anderssen, D. Uken Lawrence Berkeley National Lab. Overview. Pixel Layout “Package” Installation Pixel Support Tube (PST) structure Beampipe integrated and adjusted internally to PST Beampipe Structure

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Beampipe Support Structure VI section within the pixel detector

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  1. Beampipe Support StructureVI section within the pixel detector N. Hartman, E. Anderssen, D. Uken Lawrence Berkeley National Lab N. Hartman LBNL

  2. Overview • Pixel Layout • “Package” Installation • Pixel Support Tube (PST) structure • Beampipe integrated and adjusted internally to PST • Beampipe Structure • Supported from Wires (Adjustable +- 10 mm) • Cruciform supports with longitudinal tubes • Pixel Services supported by beampipe structure • Assembly slides in with Pixel “package” on PST rails • Two additional supports added outside PST (after adjustment) • Adjustment Mechanism • 4 wires internal to PST govern all adjustment • Support wires run to end of beampipe frame • Adjustments made with “guitar tuner” from end of PST • Every wire has one adjustor • Bottom and 1 side wire have limit springs at each support location N. Hartman LBNL

  3. Pixel and Beampipe Layout • “Package” Design • Pixel Support Tube installed in Inner Detector • Attached to SCT barrel permanently • Attached to cryostat ends through “PST Supports” (previously named beampipe supports) • Pixel Detector, Services, and Beampipe integrated into one “package” on surface • Long history to design choice (see other reviews and publications) • Basic reason is that B-layer does not fit around beampipe flanges, and so they must be assembled together • Pixel System installed into PST in ATLAS pit • Pixel, services, and beampipe transported into ID on Installation and Testing Tool (ITT) • This “train” slides into PST on rails • Beampipe and service connections made in place N. Hartman LBNL

  4. Service and Beampipe Support Pixel Package Assembly Service and Beampipe Support Pixel Detector N. Hartman LBNL

  5. Pixel Assembly – step 1(beampipe and Pixels integrated) Beampipe temporarily held with auxiliary supports (on installation and testing tool - ITT) N. Hartman LBNL

  6. Pixel Assembly – step 2(beampipe structure assembled) Beampipe support transferred To wire system in support frames N. Hartman LBNL

  7. Pixel Assembly – step 3(Pixel services attached to beampipe support frames) Only ¼ of services are shown for clarity N. Hartman LBNL

  8. Beampipe Structure • Internal Supports (to PST) • Four support locations – 2 per side • All support locations consist of 4 adjustable wires • Wires are guided and supported by beampipe support frames • Two independent support frames • One on A side, one on C side • 2 sets of support wires per frame • Frames consist of cruciform supports with longitudinal tubes • Beampipe frames coupled through pixel frame itself • All beampipe adjustments made with the four internal wire supports • Beampipe is solely supported by these 4 internal supports until adjustments are finalized • Range of adjustment +- 10 mm in X and Y • External Supports (to PST) • Two additional supports are added after beampipe adjustment • Beam support constrains beampipe in Z and R on one side • Additional wire support provides R support on opposite end N. Hartman LBNL

  9. ID Layout Drawing External Beampipe Support Position Z = 3445 Agreed Internal Beampipe Support Positions Z = 800, 3000 N. Hartman LBNL

  10. Beampipe Support Frame(for 1 side of ID – 2 “internal” supports) Service panel Attachment points Longerons Wires at Z=-800,+800 Wires at Z=-3000,+3000 Cruciform supports adjustors N. Hartman LBNL

  11. Pixel Detector Services and Beampipe Support Frame Services and Beampipe Support Frame ID LayoutPixel System and Beampipe(Package being installed) PST Shown in Orange TRT TRT SCT Adjust Support Wires Adjust Support Wires Side C Side A Coupling “clips” between pixel and Service/beampipe frame N. Hartman LBNL

  12. ID LayoutPixel System and Beampipe Installed(beampipe position locked in place) PST Shown in Orange TRT TRT SCT Pixel Detector Services and Beampipe Support Frame Services and Beampipe Support Frame Side A Side C 2 Additional Supports Added After Adjustment: Wire supports (R) TBD Beam support (R,Z) TBD N. Hartman LBNL

  13. Tension/Compression Transmission through structures not services Clips register to Buttons on Frame and Service/Beampipe support structure Gaps allow ‘Phi’ offsets of up to +/- 1mm while only 0.25mm longitudinally N. Hartman LBNL

  14. PST End View Showing Beampipe Structure Possible Additional Rails for Beampipe (both flat) Service panels Detector Installation Rails (flat and V) N. Hartman LBNL

  15. Geometry at Pixel Detector End Longerons Wire Guide Cruciform Support No BP Collar Shown Beampipe Beampipe shown in extreme off-center position N. Hartman LBNL

  16. Geometry at Forward End of Beampipe Support Wire Adjustors Longerons Wire Guide Cruciform Support No BP Collar Shown Beampipe Beampipe shown in extreme off-center position N. Hartman LBNL

  17. Beampipe Adjustment Mechanism • 4 adjustable support locations • Each location consists of 4 orthogonal wires • Located at Z positions of cruciform supports • Support wires run to end of beampipe frame • 90 degree bend made by monolithic grooved guide • Wires located co-axial to longitudinal frame tubes • Adjustments made with “guitar tuner” from end of PST • Every wire has one adjustor unit • Bottom and 1 side wire have limit springs at each support location, in addition to limit switches or indicators • Un-sprung wire provides position • Sprung wire provides tensioning (9 kg nominal) • Adjustment process: • Sprung wire is loosened • Un-sprung wire is adjusted to move beampipe into proper position • Sprung wire is re-tightened (to nominal tension) N. Hartman LBNL

  18. Beampipe Support Frame Wires at Z=-3000,+3000 adjustors Fixed Adjustors (no spring) Top and side Wires at Z=-800,+800 Sprung adjustors Side and bottom N. Hartman LBNL

  19. Use “Tuning Engine” Design(guitar mechanism) Wire Spool Worm gear worm N. Hartman LBNL

  20. Tuning engine alignment Wires leave spools and are routed down longerons Adjustors shown in Initial assembly position (no preload) N. Hartman LBNL

  21. Spring Provides Force Limitation Wire path Pins provide hard Stop in event of wire breakage Assembly Tuning unit Slides in longeron Adjustor shown in Nominal position With 9 kg preload Adjustor shown in Initial assembly position (no preload) Limit switches provide Indication of min and max preload N. Hartman LBNL

  22. Analysis – wire system (1) Furthest wire support End Fixed in Z beampipe beampipe This is an approximate solution: - wire stretch is not considered - geometry is simplified - small angles are neglected R L Z = cte expansion of beampipe V + A = R L = R + spring extension (x) Z,R Given; solve for X,V V Z A R N. Hartman LBNL

  23. Analysis – wire system (2) • Thermal expansion of beampipe • Expands from side that is constrained in Z (beam support) • Causes most motion in furthest wire • Assumptions • 7 m from Z support to furthest wire • Wire radial length is 14 cm • Elongation in furthest wire during bakeout • Chosen spring – k=3300 N/m • Wire stiffness • Assume wire diameter of 1 mm, stainless wire, maximum wire length of 2 m (very conservative, as high Z wire is not long) • k=EA/L=82500 N/m • Since wire stiffness >> spring stiffness, assume all motion is in the spring mechanism (not 100% correct, but good estimate) RESULTS N. Hartman LBNL

  24. Analysis – wire system (3) • Positioning tolerance with sprung adjustors • Nominal operating tension is 9 kg • Wire tension throughout system • Total compression in spring at 9 kg = 27 mm • Assume nominal tension should never be exceeded • Adjustment range is 10 mm • Sprung adjustor should be backed off by 10 mm before adjustments are made • Reduces nominal load in adjustor to 5.7 kg • This difference results partly in relaxation of the opposite wire • After adjustments are made, sprung adjustor is re-tightened • During re-tightening, alignment is disturbed due to stretch in wire • Total stretch = 9-5.7 kg * 9.8 / 82500 N/m = 400 microns So Intrinsic adjustment tolerance is no better than ½ mm This seems acceptable, but is it? N. Hartman LBNL

  25. Closing Comments • Design is preliminary but well thought out • Sizes are workable but approximate • No show stoppers are forseen • Work still needs to be completed • Buckling needs to be analyzed • Cruciform supports must be designed • Materials should be chosen for low activation and low Z (there is considerable flexibility in material choices for the final design) • Beampipe interface (collars) must be designed • Vibration analyses may be required • Detail designs must be completed • Prototype plans • Full working prototype will NOT be built • Adjustor units will be prototyped • Single support frame (1 side) will be built and tested • Will use initial design • If this needs re-design and rebuilding, it will come from contingency • Second frame will be built to final design (may be same as initial) • Prototyping to begin in October 2002 assuming funds are available N. Hartman LBNL

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