atlas pixel detector pixel support tube interfaces lbnl internal pst review e. anderssen, lbnl

ATLAS Pixel Detector

Pixel Support Tube Interfaces

LBNL Internal PST ReviewE. Anderssen, LBNL

September 2002Internal Review

E. Anderssen LBNL

ATLAS Pixel DetectorOverview

• Structures and Position in ATLAS• Internal Interfaces

– Rail Geometry/Sliders/Roller– Pixel to PST Mounts– PP1/PP0

• Mount/External Interfaces– PIXEL to SCT Mount Block– Forward End Support Flexures


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ATLAS Pixel DetectorPST Key Structures

Hoop Hat Stiffeners(section view)

30

45 10

SCT Flexuresand mount pads

Forward End Flexures Forward A

Forward C

Barrel

PST FlangesPP1 End Plug


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ATLAS Pixel DetectorPixel Package—Internal Interfaces

Service and Beampipe Support

Service and Beampipe Support

Pixel Detecto

r

PP0

PP1

PP1

Beam pipe SupportRail Sliders

Beam pipe SupportRail Sliders

Pixel FrameRollers

Pixel Mounts


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ATLAS Pixel DetectorPackage interfaces to PST

• Package has Several Physical Interfaces to PST– Rail Sliders/Rollers on Frame and Service/Beampipe Support– Pixel Mount Blocks– PP1 End Plate

• Installation Configuration– Frame Rollers engaged, Pixel Mounts not Yet Engaged– Rails Supports Entire Detector– PP1 Fixed Portion Clears Internal Dimensions of PST

• Installed Configuration– Frame Rollers Disengaged, Pixel Mounts engaged– Rails Continue to support Services and Beampipe– PP1(s) are Supported By PST end Flanges


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ATLAS Pixel DetectorInner Detector Layout


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ATLAS Pixel DetectorPatch Panel Zero

PPO region preliminary layout—cable routing and assembly sequence not completed

Nominal routing for tubes shown here—allows access to rails and pixel supports (discussed later)

Pixel Mount Block Access

Frame RollersService Sliders


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ATLAS Pixel DetectorPatch Panel One

PP1 layout determines final length of the Forward section of the PST—Layout of region is preliminary, and will require physical modeling to complete


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ATLAS Pixel DetectorMount Interfaces and Geometry

• Pixel detector is supported on mounts integrated into Flange of the Barrel PST

• Barrel PST is mounted to the Barrel SCT via Flexures and fixed Support– Mount Pad integrated with Flange of Barrel PST directly couples

SCT and Pixels decoupling as much as possible the shell of the PST• Forward PST sections are mounted to the Barrel PST

via a flange, and supported at their ends from the PST Support structure (formerly Beampipe support)

• Rails discussed later, however for completeness:– Pixel Detector rides in with package on rails and transitions to

mounts in the Barrel section of the PST– Remainder of Package (Service/Beampipe support Structure)

remains on rails


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ATLAS Pixel DetectorMount Schematic

• Pixel Support Tube Mounts to SCT Interface Block Via a Flexure• Pixel Detector Mounts to PST Barrel Via the Pixel Mount

SCT Not shown here

Pixel Detector

SCT Interface Block

Pixel Mount

Flexure

Missing Integrated Model with both PST and Pixel Detector Frame


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Interface to SCT Interlink(Barrel PST support)

• Pixel Support Tube is supported by Three Flexures and One “Fixed Support”– All Flexures and the Fixed Support have identical bolted and pinned

interfaces with PST Barrel and SCT Interface Block

• Interface Blocks which penetrate the SCT Thermal Enclosure are mounted to the SCT Interlink

• All Interface Blocks are identical – Brief modification of the end of the interlink to accommodate– Penetration through SCT Barrel Thermal enclosure standardized


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Proposal for SCT - Pixel Interface- 4 Blocks fastened to the SCT horizontal interlinks- Adjustement, if needed, by shimming or machining PST blocks

DimensionIs OK

Slide of E. Perrin

Need to Make integrated Model/Interface Drawing with relevant parts of SCT


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SCT Inner thermal enclosure- I propose to fix the TE inner cylinder directly to Barrel 3

- To save space.- To try to simplify penetrations and sealing.

Flexure

PST BARREL MOUNT PAD

3mm Shim (0-6mm As REQ)

R240

R253.5

Z 780


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ATLAS Pixel DetectorManufacturing and Assembly implications

• Flexures Mount Directly to SCT Interface Block (prior to PST Insertion)

• Mounting Pixel Support Tube requires access to inside of Barrel PST– Pins and bolts into Flexure are accessed through cutout– “Adjustment” is by shimming (horizontal) and flexure replacement

(vertical) – Adjustment only required in emergency in pit—nominally PST is

centered in SCT

• Above implies that set of pre-machined flexures will be required

• Pinned interfaces require accurate mating and alignment of interfaces

• Proposed solution is to Bond PST mount Pads in place– Depending on Schedule either Transfer Tooling or Bond in place


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ATLAS Pixel DetectorManufacturing Accuracy by Bonding

• Whether SCT or Mistress tool is used depends on Schedule

• Bond Gap can currently account for +/- 200, but can easily accommodate up to 1mm if required (need to change some nominal dimensions)

Bond Between Mount Block and PST Mount Pad can be made last

Mistress tool or SCT AS Built


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ATLAS Pixel DetectorInterface Geometry

780

803

PST MountFlexure

253.5

SCT Barrel 3And Interlink


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ATLAS Pixel DetectorMount Block Analysis

• Flexures chosen for tight packaging Accurate manufacture and predictability of analysis

• Large Factors of Safety against yield at maximum foreseen loads

• Have assumed that loads from Integrated SCT/PST model represent worst case loads (2mm end deflections of PST)


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ATLAS Pixel DetectorHow Much Float is needed

• Fixed Point to End of SCT yields an internal stress

– Due to CTE mismatch on the order of 1-2ppm/C

• Fixed point to end of Cryostat yields an External load on the ID Barrel via the SCT

– There is potentially a large CTE mismatch between Cryostat and the Pixel Support Tube

– Case where Cryostat raised 10C above no-power condition, and where Support tube CTE is unusually high (>1ppm/C)

• Flexures need to assure minimal loads at these extensions yet remain stiff in the orthogonal directions

fixed

1.6m120

4.25m @ +1ppm/C2.65m @ +1ppm/C

4.25m @ +23ppm/C1.2mm

2.65m @ +23ppm/C 700

-20C

-20C

+30C


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ATLAS Pixel DetectorBarrel Flexure Analysis

0.5/N0.17/N

2.3/N

50N

147N

150N

75 25

115


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ATLAS Pixel DetectorNeeded Load Set on Flexure

Fx

Fz

Fy

My

Mz

Mx

Direction LoadRequired

LimitLoad

Fx 121N 450N(~250)

Fy 211N 2.3kN

Fz 68N 400(150N)*

Mx 322N.m 750Nm

My 189N.M 24.6Nm

Mz 53N.m 19.6Nm

flex

*Load at 400 deflection—stop prevents further travel preventing plastic deformation of flexure. Load then transfers to bolted joint which has a limit loadEqual to Fy.

No limit in Fy foreseen due to high factor of SafetyLimits in X,Z make FoS similar to Fy (bolted interface)


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ATLAS Pixel DetectorDesign of flexure against Failure

• Flexure Yields in Z- Travel at ~400 deflection– Stops included to limit travel to 400 or less

• Fy Ultimate for Flexure depends on Tensile stress area of Webs on Flexures

– Area of webs ~20mm2 – area of Bolt M6 ~20mm2

• Fx will have limits built into interface pads as shown in figure above on right

• Built Prototype Flexure without Stops to verify plastic limits

• Will test Stiffness of Flexure with TVH system

Fy=5.2kLbf

M6 Fast

ener

FX

Fx

Fz

Fy

My

Mz

Mx

Flexu

re

PST M

ou

nt P

AD

Limit to <150

Shim


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ATLAS Pixel DetectorForward Flexure

Plastic Limit stop will be incorporated in design, and integrated withFlex lock mechanism necessary for lock-out during Installation ofPixel Detector

80


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ATLAS Pixel DetectorPixel Support Condition on PST

• This is an attempt at a pseudo-kinematic mount condition• Three points are fixed, with one adjustable in height—

nominally this is one of the ‘flat’ mounts• Mounts will be adjusted in co-planarity to match mount

surfaces—reducing twist of frame


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ATLAS Pixel DetectorPixel Frame Mounts

• Prototype of Pixel mounts developed

• Axle and Bearing design refined

– Angular contact bearings– Ceramic race – Ceramic Balls– Titanium Shaft

• Contact analysis shows one ball can take full detector load (no brinnelling)

• Statistical tolerance analysis shows 5 or more balls in contact

• Shaft is Full Hard 6Al4V Ti alloy with Nitrided Surface


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ATLAS Pixel DetectorInterface to Pixel Frame Endplate

• Three mounts fixed, One adjustable vertically• Two dowel pins, Three mounting screws• Holes machined in Ears of Endplate• Endplate registered to End frame by tight

shoulder screws in same ear


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ATLAS Pixel DetectorPixel Mount Block and preload spring


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ATLAS Pixel DetectorPreload Flexure

• Flexure Designed for 105N Preload– Nominally equals detector mass

plus some margin

• Deflection at preload nominally 1mm– Large compliance allows for

moderate machining and misalignment tolerances

• Factor of Safety against yield at Max flex design travel 1.7


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Flexure

PST BARREL MOUNT PAD R240

SCT Interface surface

pixel

40 Budget

Mount Deflection Budget• Gravity Deflection Budget of 40 is assumed80Hz assumed for

vibrational stability• Flexure/Mount Pad-Flange/Pixel mount all contribute• Assumed 20 for Pixel mount, 20 for rest


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ATLAS Pixel DetectorDeflection of Mounts

• Tip deflection of Long Shaft is 20.

• Angle change of shaft from pillow block adds 8.

• Nominal budget for Pixel mount was 20.

– Long shaft is coupled with short PST interface block

– Short shaft has less shaft deflection but more PST Pad windup

• Total Budget of 40 between SCT and Pixels is shared between these mounts and the PST mount pad

• Total budget is close to met—see Neal’s talk