LCLS Undulator Bellows Module

Jan. 6, 2006Chamber & Bellows IDR

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LCLS Undulator Bellows Module

Soon-Hong Lee

Internal Design Review


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LayoutGeneral RequirementsSpecificationsConceptual DesignsMaterials for Bellows ModuleFE Stress AnalysisMechanical Failure TestConclusions

Contents


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LayoutShort Break Diagnostic Section


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From www.flexhose.com

• Baking temperature at ~200 C• Fabrication tolerance of chamber, BPM, Quad. • Longitudinal cradle motion constraint = 3.0 mm• Total axial travel 5.0 mm

• Adjacent two undulators are tilted symmetrically• Angular stroke for bellows module = 2 tan–1 (height change/length between bellows module) • Height change = 2 mm (~2.5) + 2 mm (~2.5) = 10 mm 2 x tan–1 (10/3800) = 0.3• Undulator segment pitch tolerance (rms) = 14 rad • Total angular rotation 0.5

• Adjacent two undulators are tilted and/or in parallel• Quad center manual adjustment range = 2.0 mm • Total lateral offset 2.0 mm

General RequirementsBellows motion requirements


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General RequirementsMechanical Concept of Bellows Module

Consider axial travels/constraints for easy installation and maintenance Consider lateral offset with flexible contact fingers and static stubConsider maintenance cycle and material fatigue lifeConsider mechanical restraints to prevent damages for bellows and fingers

RF ConnectionsProvide a sliding surface with good lubricity and good electric conductivity

RF fingers, spring fingers, and stub mechanismRF seal ring or spring gasket across flange joints

0.4 ~ 0.5 mils silver plating on the shield fingers0.2 ~ 0.3 mils rhodium plating on the stub


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SpecificationsFlexibility Allow 0.5 of Angular Stroke (Pitch and Yaw)

Allow 2.0 mm of Lateral Stroke (X & Y axes) Allow 5.0 mm of Axial Stroke (Z axis)

Life At least 2,000 cycles

Vacuum 1 x 10 –7 Torr

Low Beam Impedance Electric continuity by RF fingers and RF seal ring or spring gasket across flange joint

Space Constraints Minimize beam directional overall length of module (Z-axis)Axial constraint mechanism for easy installation and maintenance

Thermal Loads Bake at 200 C and Operation HeatingContact Resistance Heating

Structural Loads Fatigue stress due to flexible strokes across the moduleGravity, vacuum force, and contact force

Plating Requirements 0.4 ~ 0.5 mils Silver plating on the RF-shielding fingers0.2 ~ 0.3 mils Rhodium plating on the Stub tube/Spring fingers


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Bellows ModuleRemovable tie rods

for restraints to prevent damages

Welded Bellows (200-125-3-EE)

Axial travel: 16~60 mm lateral offset: 4.3 mm

angular offset: 50

EVAC flanges with chain clamps for

space limitation and easy maintenance

RF-connections


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Bellows Module - Exploded

RF Fingers (BeCu 174) with Ag-plating

Stub (OFE Cu) & Spring Fingers (BeCu)

with Rd-plating

RF seal ring or spring gasket


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Materials for RF Fingers and Stub

FingersStub Tube

FingersFlange Need Heat Treatment after

forming


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RF Finger Stress Analysis

3 mm at tip


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RF Finger Stress Analysis

324.8 MPa at root > Fatigue strength of BeCu (276MPa)


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Design Parameters

RF-finger root

RF-finger tip

• To investigate maximum stress at root • contact types (point contact or surface contact) • # of RF-fingers • # of Spring-fingers• shape of fingers to reduce the overlap damage• thickness and length of fingers

Spring fingerStub


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FEA Case Study

Case Contact

RF Fingers Spring Finger

Thickness Maximum Displacement

Maximum Stress

Z-travel (± 5 mm )

No. of Fingers

Root angle

Tip angle

No. of Fingers

Fingerangle

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Point Contact

18 18º 8º 8

45º

0.15mm

3.85 mm 225 MPa Contracted

2 9 36º 16º 8 3.82 mm 397 MPa Contracted

3-1 16 20º 8º 8 3.79 mm 226 MPa Contracted

3-2 16 20º 8º 8 2.87 mm 144 MPa Extended

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Surface Contact

18 18º 8º 8 3.13 mm 281 MPa Contracted

5 18 18º 10º 9 40º 3.04 mm 304 MPa Contracted

6 15 22º 10º 9 40º 0.30 mm 3.38 mm 553 MPa Contracted

7 9 36º 18º 9 40º 0.15 mm 3.84 mm 423 MPa Contracted

8, 9 18 - - 0.15 mm 6.10 mm 221 MPa No Spring fingers

• Use Pro/Mechanica - Contact Analysis - Surfaces of fingers & stub are contacted - Applied ±2 mm (Y) for lateral offset, ± 5 mm (Z) for axial travel• Criteria - Maximum Displacement < 8.0 mm - Maximum Stress < 276 MPa (based on fatigue strength of BeCu Alloy 174)

- 2mm

+ 2mm

+ 5 mm


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Case 1


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Case 3-1


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Case 3-2


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Case 8


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Case 9


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RF Fingers

0.15 mm thick 53.5 mm long

16 fingers


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Spring Fingers

0.15 mm thick29.5 mm long

8 fingers


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Bellows Module Assembly


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Mechanical Failure TestObject of failure test is to prove the part in the following conditions• 2,000 cycle actuation

• ± 5.0 mm axial travel distance

• ± 2.0 mm lateral offset movement

0.5 of angular stroke

• Ag- & Rd- plating thickness

Materials Size Price Vendors

Stub OFE Cu Tube ½˝ O.D. x 0.0625˝ THK x 1.5˝ LG Copper and Brass Sales

OFE Cu Rod 5/8˝ O.D. x 1.5˝ LG

Fixtures OFE Cu Plate 5/16˝ (or 1/4˝) x 12˝ x 72˝

RF-fingers / Spring-fingers

BeCu 174-HT Thickness: 0.15 mmWidth: 35 mmLength: 55 mm

1lb/ free sample

Brush Wellman, Inc. (1 lb free, $500 min. lot charge)

BeCu 25-1/2HT

GlidCop A-15 Spot Welding Consultant, Inc.

$460.00 / min. 5 lb

J. L. Anthony & Company

Bellows Stainless Steel 347

P/N: 200-125-3-EELateral offset: ±0.17˝ (4.3 mm)Angular offset: ± 50° @ installed length of 1.59˝

$ 271.00 /Ea

Standard Bellows Company


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ConclusionsEstablished design specifications based on physics requirements, maintenance, and installation etc.Conceptual design and drawings are completed.Based on FE analysis (contact analysis) by use of Pro/Mechanica, max. stress on fingers is expected to have 226MPa which shows below fatigue strength (276 MPa) of BeCu Alloy 174.Lubricity and mechanical failure tests are planned to investigate the Rd- & Ag-plating thickness and the performance of RF- & Spring-fingers.


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RF Fingers and Stub PlatingBellows Testing

Jim Morgan


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RF Fingers and Stub Plating and Test Requirements

Plating RequirementsMaintain electric continuity and provide lubricity across the sliding joint ( RF fingers and Stub) during operationsOptimize plating performance

•Avoid galling•Minimize loss of plating•Avoid loss of plating adhesion (flaking)

Testing Parameters for Bellows Assembly and Sliding Joint•Test at 10-7 torr•Allow visual inspection of sliding joint during the test•2000 cycle test•±5mm axial travel (static and dynamic)•±2mm lateral offset (static and dynamic)•±0.5° angular offset


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Approach

1. Plate RF Fingers and Stub with Rd and Ag according to specifications developed for the bellows for the PEP- II High Energy Ring*

2. Test fingers as assembled inside the bellows to insure acceptable performance at operating conditions for 2000 cycles

3. Change coating thicknesses if required

4. Optimize performance as budget and schedule allow*Curt Besler, Jeffery Berg “High Current RF Shield for PEP-II Vacuum System Expansion

Joint” LLNL

M.E. Nordby, N. Kurita “Bellows Design for PEP-II High Energy Ring Arc Chambers” SLAC


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Plating Materials and Initial Thickness

RF Fingers – 0.4 to 0.5 mils Ag

Stub – 0.2 to 0.3 mils Rd

Plating thickness can be changed to optimize performance.

Other possible materials for increased lubricity at the joint

include:

Dicronite – impregnated Tungsten Disulfide

Nanolube – nested nanoshpere structure Tungsten Disulfide


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Section Thru Test Fixture

Set-up for dynamic axial Testing


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Enlarged View – Test Fixture

Enlarged view


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Bellows Prototype ScheduleActivity ID Activity description Early start Early finishUN43_00242 Study of Lubrication Coating 05/02/05A 11/30/2005UN43_00243 Proto Mech. Anal. 06/15/05A 11/30/2005UN43_00241 Proto Prelimin Design 07/22/05A 11/30/2005UN43_00245 Test Tooling Design 11/01/05* 11/30/2005UN43_00244 Evaluation of Lubrication Coating 11/22/05* 1/12/2006UN43_00246 Proto Review 1/13/2006 1/30/2006UN43_00247 Proto Final Design 1/31/2006 2/20/2006UN43_00248 Write Bellow Fab Spec 2/14/2006 3/1/2006UN43_00201 Test Equipment Fab & Assy 2/21/2006 4/3/2006UN43_00070 Bid Package-Ag Plated RF Finger Prtp Bel Mod 3/2/2006 3/6/2006UN43_00080 Bid Package-Rh Plated Stub Prtp Bel Mod 3/2/2006 3/6/2006UN43_00090 Bid Package-Tubes Prtp Bel Mod 3/2/2006 3/6/2006UN43_00100 Bid Package- Prtp Bellows Module 3/2/2006 3/6/2006UN43_00120 Bid Process Prtp Bel Mod 3/7/2006 4/10/2006UN43_00130 Procure Ag Plated RF Finger Prtp Bel Mod 4/11/2006 4/12/2006UN43_00140 Procure Rh Plated Stub Prtp Bel Mod 4/11/2006 4/12/2006UN43_00150 Procure Tubes Prtp Bel Mod 4/11/2006 4/12/2006UN43_00160 Procure Bellows Prtp Bel Mod 4/11/2006 4/12/2006UN43_00180 Prototype Bel Mod Award Complete 4/12/2006UN43_00190 RCV: Bellows Prtp Bel Mod 4/13/2006 5/24/2006UN43_00200 Quality Assurance Prtp Bel Mod 5/25/2006 6/1/2006UN43_00220 Measurement and Test Prtp Bel Mod 6/2/2006 6/15/2006UN43_00230 Review and Report Prtp Bel Mod 6/16/2006 6/22/2006UN43_00240 Prototype Bel Mod Testing Complete 6/22/2006


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Bellows Prototype Costs

•Material costs from current loaded schedule

•Bellows $ 1,500

•Test Equipment $ 4,000

•Evaluation of plating $ 3,000

•Rh plate stub $ 900

•Ag plate fingers $ 3,000

•Fabrication of small parts $ 600

Documents

LCLS Undulator Bellows Module