LCLS Undulator Vacuum Chamber Design

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Slide 1

LCLS Undulator Vacuum Chamber Design Soon-Hong Lee Advanced Photon Source

Slide 2

CDR Vacuum Chamber Requirements – Small Vertical Aperture (5 mm) and Thin divider (<0.5 mm) External Dimension: 6 mm OD x 3.42 m long (to fit inside a 6.35 mm crevice) – Stable Geometry (No Vacuum distortion) – High Conductivity Inner Surface To minimize the electric resistive wake-field impacts – Low Surface harshness, Ra < 100 nm (h: ~100 nm, g: ~100  m) To minimize the surface unpleasantness wake-field impacts – High Melting Temperature To make due amid direct essential bar introduction – Low Pressure and L ow out-gassing rate (pumping just in undulator hole)

Slide 3

Vacuum Chamber Design Options 1)

Slide 4

Vacuum Chamber Design I – Tube choice Concept I Ni-Coating to reflect completed SS 316L Tube and E.P. Cu-covering and E.P. E-Beam welding to SS flat bolster plate TIG welding to solid back vertical plate (or Clamping utilizing clasp) Concept II Electro-cleaning of OFHC Cu Tube (As-drawn tube) E-Beam attach welding to Cu plate Brazing to SS level bolster plate TIG welding to solid back vertical plate (or Clamping utilizing latches)

Slide 5

Vacuum Chamber Design II – Box Option Concept I Machining 4-mm thick plates for pillar gap opening Eletropolishing & Cu-Coating E-Beam welding at both sides E-Beam to SS even plate TIG welding to solid back vertical plate (or Clamping utilizing latches) Concept II Machining 8-mm thick plates for welding seats Bend SS reflect completed strip Cu-covering to twisted strip and E.P. E-Beam welding to machined plate TIG welding to solid back vertical plate (or Clamping utilizing clasp)

Slide 6

Comparison of Vacuum Chamber Designs

Slide 7

Vacuum Chamber Development – Tube choice

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Vacuum Chamber Development – Box alternative Stress Analysis Aperture Maximum Displacement Maximum Stress Remarks 10 mm (H) x 5 mm (V) – Strip 0.52  m 8.15MPa Small opening 6 mm 15 mm (H) x 5 mm (V) – Strip 5.86  m 41.7MPa Acceptable 25 mm 20 mm (H) x 5 mm (V) – Strip 19.2  m 106.4 MPa Out of criteria 20 mm (H) x 5 mm (V) gap – Strip sort Maximum Displacement: 19.2  m Maximum Stress: 106.4MPa 10 mm (H) x 5 mm (V) gap Strip sort Maximum Displacement: 0.52  m Maximum Stress: 8.15MPa 10 mm (H) x 5 mm (V) – U-profile 2.22  m 35.8MPa Small gap 12 mm (H) x 5 mm (V) – U-profile 3.72  m 42.1MPa Acceptable 15 mm (H) x 5 mm (V) – U-profile 9.40  m 84.2MPa Out of criteria 20 mm (H) x 5 mm (V) – U-profile 27.3  m 115.7MPa Out of criteria 6 mm 20 mm  Criteria -Maximum Displacement < 10  m (?) -Maximum Stress < 69MPa (Safety figure w.r.t. yield stretch: 3.0)

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6 mm ~102.5 mm 15 mm (H) x 5 mm (V) opening – Strip sort Maximum Displacement: 7.60  m Maximum Stress: 59.9MPa Global Sensitivity Study Max. von Mises stretch versus flat opening/Max. uprooting versus flat gap 69 MPa 10  m 16.7 mm 16.5 mm Global Sensitivity to even gap estimate

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15 mm (H) x 5 mm (V) gap – Strip with Strong-back Support Maximum Displacement: 18.88  m Maximum Stress: 48.3MPa Applied Loads & Constaints 3D –ProMechanica Model Vacuum Chamber Analysis – Support structure

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4 x E-Beam UHV Welding Leak Check I Prototype II Prototype I 8 mm  0.2 6 mm  0.1 Machining Both Surfaces Cu-Coated on reflect completed SS 316L strips (1.5 mm thick) Cu-Cu E-pillar Tack Welding Cu-SS Brazing SS316L OFHC Cu II Vacuum Chamber Prototypes

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