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ATLAS Pixel Detector September 2002 N. Hartman LBNL 1 Pixel Support Tube: Design, Prototyping, and Production PST Progress Update September 2002.

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Presentation on theme: "ATLAS Pixel Detector September 2002 N. Hartman LBNL 1 Pixel Support Tube: Design, Prototyping, and Production PST Progress Update September 2002."— Presentation transcript:

1 ATLAS Pixel Detector September 2002 N. Hartman LBNL 1 Pixel Support Tube: Design, Prototyping, and Production PST Progress Update September 2002

2 ATLAS Pixel Detector September 2002 N. Hartman LBNL 2 September 17 th Review Schedule 9:00PST Design Update 9:30 Shell Prototyping 9:45 Rail Prototyping 10:00 Mounts and Interfaces 10:30 Break 10:50Heater Testing 11:05 Heater Design and Fabrication 11:25Production Planning, Costs, Schedules 12:15Questions/Comments

3 ATLAS Pixel Detector September 2002 N. Hartman LBNL 3 Pixel Support Tube (PST) Overview Design Updates –Flange design Reduced from 26 pieces to 2 Length Shortened –Rail design Impact on stiffness of forward shell calculated Reduced from 2 pieces per rail to 1 Shell design augmented Local stiffness analyzed Prototyping –Material test results received –Shell and rail prototypes fabricated (covered in subsequent presentations) Shell produced with heaters, and in hybrid form Short rails produced and measured Production covered later

4 ATLAS Pixel Detector September 2002 N. Hartman LBNL 4 PST Overview

5 ATLAS Pixel Detector September 2002 N. Hartman LBNL 5 Support Condition of Pixel Support Tube in Inner Detector SCT TRT Fixed XYZ Fixed YZ (N/A) Fixed XY Fixed Y ID Vee Rail (float Z/dogged Z) (constrained XY) ID Flat Rail (float XZ) (constrained Y) +Z +X Side CSide A +Y Vertical SCT Vee Rail (float Z/dogged Z) (constrained XY) SCT Flat Rail (float XZ) (constrained Y) View from top—all Tube Supports are Horizontal and Co-planar Properties TBD Constraint TBD Flexure Mounts

6 ATLAS Pixel Detector September 2002 N. Hartman LBNL 6 PST Key Structures Forward A Forward C Barrel PST Flanges SCT Flexures and mount pads Mount Pad Flexure Forward End flange and Flexure, installation rail

7 ATLAS Pixel Detector September 2002 N. Hartman LBNL 7 Rail Overview DETAIL Flat Rail DETAIL V Rail Vee and Flat rails were chosen to provide pseudo-kinematic support for the detector during delivery to the support points. Rails are used only for delivery, not support.

8 ATLAS Pixel Detector September 2002 N. Hartman LBNL 8 Flange Design

9 ATLAS Pixel Detector September 2002 N. Hartman LBNL 9 Flange Face (machined layup) Flange base (Layup) Stiffeners (layups) Flange bolts Initial Flange Concept Base Piece –½ mm thick –Laid up as hoop, sized to fit shell Face Piece –Laid up as plate –Machined to size Reinforcements –Laid up individually –½ mm thick –24 parts Assembly –26 pieces bonded simultaneously as one assembly –Flange assembly bonded to PST Shell

10 ATLAS Pixel Detector September 2002 N. Hartman LBNL 10 Revised Flange Concept Stiffeners eliminated –Not required for stiffness –Reduces part count by 90% Flange shortened –From 40 mm long to 25 mm –Allows thicker “skirt” in order to machine ID, while approximately conserving material amount from old design –Still extremely conservative bond stresses Two piece design –Single piece skirt and flange face, provides good shear coupling to shell –ID of skirt machined, but face is not –Backing piece provides extra thickness for required stiffness Flange Cross Section Single piece skirt and face (“L” shape) Backing Ring

11 ATLAS Pixel Detector September 2002 N. Hartman LBNL 11 Revised Flange Analysis ANSYS analysis –Stiffening ribs removed –Flange constrained over bolt stress areas only (~2.5*Bolt Dia.) –Bolts omitted on diameter (planned pin locations) –2 mm forward end offset used (worst case) Results –Sub-micron displacement in flange –Max bolt load ~100 N (at topmost bolt) Glue Stress Calculations –Simple shear stress calculated (Shear = Axial Force/Area) –Max bolt load used and area assumed to be ½ of 1 stiffening unit (1/48 th of flange circumference) –Max stress assumed of 21 Mpa (Hysol Adhesive) –Factor of Safety = 140 for 25 mm long flange Glue Shear Stress Calculation Area Max Bolt Force

12 ATLAS Pixel Detector September 2002 N. Hartman LBNL 12 Rail Design

13 ATLAS Pixel Detector September 2002 N. Hartman LBNL 13 Rail Design Summary So far, the PST has been modeled without considering the effect of rails in the bending stiffness of the shell –Provided for faster/easier modeling –Will result in higher displacements in the SCT when rails are added Rails have conflicting design demands –Rail deflection must be minimal, to assure installation of detector –Rail stiffness must also be minimal, to reduce impact on SCT Initial analysis showed problems –Rail deflections were perhaps acceptable (~ microns) –However, impact on stiffness unacceptable (increase of 85%) Design shifted to one piece rail –Goal to increase local section modulus of rail, but with lowest cross sectional area possible “Hollow” shape more efficient However takes up more space in PST –Fiber changed to high strength carbon (rather than high modulus) in order to lower contribution to overall shell stiffness

14 ATLAS Pixel Detector September 2002 N. Hartman LBNL 14 Evolution of Rail Design Initial rail shape designed to use as little space as possible inside PST, and to allow placement of sliders anywhere along frame One piece design chosen to fill maximum volume (and increase bending stiffness of rail itself). This was made possible by decision to place sliders/rollers at end of frame, freeing up space for rail inside. V-rail changed to “inverted” v shape. Increases inertia of section, and can be used either as v or inverted v.

15 ATLAS Pixel Detector Rail FEA Model Model simulates prototype of rails and 300 mm long shell (initial two-piece rail shape). Pixel Mass (1/4 of 35 kg) applied to PEEK slider. Slider impacts rail through contact elements. Shell is constrained along edges (where flanges or stiffeners would be). Shell modeled as both quasi-isotropic glass laminate and composite hybrid laminate of carbon and glass. 300 mm rail slider shell constrained on edges Cross section of v-rail and slider Prototype PEEK slider center bearing Section (R = 10 mm, L = 20) tapers on ends for rail misalignment slider shell

16 ATLAS Pixel Detector Rail Analyses Quasi-isotropic Glass Shell E = 19 GPa Slider made from PEEK E = 3.5 GPa Rail Quasi-isotropic CN60 E = 126 GPa Load Applied = 8.75 kg Dmax = 185 microns Composite Carbon/Glass Shell (Carbon in Hoop Direction) E axial = 21 GPa; E hoop = 147 GPa Slider made from PEEK E = 3.5 GPa Rail Quasi-isotropic CN60 E = 126 GPa Load Applied = 8.75 kg Dmax = 154 microns Hybrid Shell reduces rail displacement by 20%

17 ATLAS Pixel Detector September 2002 N. Hartman LBNL 17 Expected Rail Performance Rails displace more in beam mode than shell mode (displacements are primarily not in the cross sectional plane) –Deflection scales by stiffness (EI) of rail itself (to first order) –However, adding additional hoop plies of YSH80 (in the forward) does help by about 20% Different rail designs were compared for optimization –FEA results used as a starting point and comparison –Different designs compared by calculating EI, and then scaling to find expected stiffness and deflection implications Deflection in final rail shape is anticipated to be on the order of 125 microns (5 mil).

18 ATLAS Pixel Detector Anticipated Loads/Displacements Induced in SCT With Stiffer Forward PST Shells, Due to Installation Rails Z constrained flexure is located on side C, negative X (in this coordinate system). Highest Displacements and Forces Still Arise from Gravity and CTE Loading, Which are not affected by an increase in the Forward Shell Stiffness.

19 ATLAS Pixel Detector September 2002 N. Hartman LBNL 19 Prototyping

20 ATLAS Pixel Detector September 2002 N. Hartman LBNL 20 Prototyping Plan Material Testing –First test completed –Results are fairly consistent, but disagree with calculations Shells – presented seperately –Completed –Successfully demonstrate ability to reliably make tubes of given size Rails – presented seperately –Partially Complete – foot long rails have been made –Successful so far, but issues remain –Rail Sliders and/or rollers need to be fabricated and tested Flanges –To be outsourced, not yet complete Hoop Stiffeners –May not be prototyped (fabricate during production phase only) Mount Pads/Flexures – presented seperately –To be fabricated in-house, not yet complete PST Assembly (bonding) –Not yet complete –To be fabricated in-house and/or outsourced –Design yet to be completed

21 ATLAS Pixel Detector September 2002 N. Hartman LBNL 21 Material Test Results Calculations Differ substantially from results attained –Modulus of YSH80 samples is almost 40% low in cases (this modulus would be expected with CN60 type fiber) –Modulus of CN60 sample is approximately 20% low –Fiber volume from one sample is low (other samples not tested) However, measurements are fairly consistent –YSH80 samples are both very low –E1 and E2 directions are similar (quasi-iso layups) –Spread in test data (from multiple coupons) is not extreme –Void content in one sample is fairly low (other samples not tested)

22 ATLAS Pixel Detector September 2002 N. Hartman LBNL 22 Major Outstanding Items Design –Rail Riders Conservative choice is a rolling mechanism for detector –Space available at end of frame –Detector is more than half of sliding mass (on four support points) Sliders will be retained for service structure –Space for rollers is probably not available –Each support sustains lower load –Rails Is 35% increase in bending stiffness of forward tube acceptable? Rigorous FEA model of new rail design must be completed, along with tests to validate stiffness –Flange/Mount Pads Design must be modified for new flange (without ribs) Prototyping –Material Properties Discrepancies must be reconciled (Test accuracy or fabrication?) –Hoop Stiffeners Layup separately or incorporate in shell layup (this would require prototyping) –Bond Tooling All design must be completed in order to finish prototype phase


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