Transcript Mechanical/Vacuum Design

LCLS Undulator
Vacuum Chamber Design
Soon-Hong Lee
Advanced Photon Source
Argonne National Laboratory
Office of Science
U.S. Department of Energy
A U.S. Department of Energy
Office of Science Laboratory
Operated by The University of Chicago
CDR Vacuum Chamber Requirements
– Small Vertical Aperture (5 mm) and Thin wall (<0.5 mm)
External Dimension: 6 mm OD x 3.42 m long (to fit within a 6.35 mm gap)
– Stable Geometry (No Vacuum deformation)
– High Conductivity Inner Surface
To minimize the electric resistive wake-field effects
– Low Surface roughness, Ra < 100 nm (h: ~100 nm, g: ~100 m)
To minimize the surface roughness wake-field effects
– High Melting Temperature
To survive during direct primary beam exposure
– Low Pressure and Low out-gassing rate (pumping only in undulator gap)
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Vacuum Chamber Design Options
SS 316L tubing + Ni Coating
+ E.P. + Copper Coating + E.P.
OFHC seamless Cu tubing
+ E.P.
SS 316L plate/strip + Machining + E.P.
+ Coating + Welding + Annealing
Al Extrusion + E.P.
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1)
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Vacuum Chamber Design I – Tube option
Concept I
1.
2.
3.
4.
Ni-Coating to mirror-finished SS
316L Tube and E.P.
Cu-coating and E.P.
E-Beam welding to SS horizontal
support plate
TIG welding to strong-back vertical
plate (or Clamping using fasteners)
Concept II
1.
2.
3.
4.
Electro-polishing of OFHC Cu Tube
(As-drawn tube)
E-Beam tack welding to Cu plate
Brazing to SS horizontal support
plate
TIG welding to strong-back vertical
plate (or Clamping using fasteners)
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Vacuum Chamber Design II – Box Option
Concept I
1.
2.
3.
4.
5.
Machining 4-mm thick plates for
beam aperture opening
Eletropolishing & Cu-Coating
E-Beam welding at both sides
E-Beam to SS horizontal plate
TIG welding to strong-back vertical
plate (or Clamping using fasteners)
Concept II
1.
2.
3.
4.
5.
Machining 8-mm thick plates for
welding seats
Bend SS mirror-finished strip
Cu-coating to bended strip and E.P.
E-Beam welding to machined plate
TIG welding to strong-back vertical
plate (or Clamping using fasteners)
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Comparison of Vacuum Chamber Designs
Chamber Designs
SS 316L tube
+Ni Coating
+ E.P.
+Cu Coating
+ E.P.
OFHC
Cu tube
+ E.P.
Advantages
- Low surface finished tubing
( ~ 5 Ra Sumiclean & Valex)
- High melting temperature
( ~ 1670K)
- Low out-gassing rate
- Not easy to handle, install and align without
- High conductivity (100%)
 Coating not required
- Not easy to handle, install and align without
- Low out-gassing rate
comparable to stainless steel
- High melting temperature
SS 316L
plate/strip
+ Machining
+ Welding
+ Annealing
Disadvantages
( ~ 1670K)
- Low out-gassing rate
- Self-support mechanism
- Can measure surface
roughness before welding
loosing aperture from bends and dents
- Low conductivity  Coating required
- Not easy to coat the copper
- Not easy to achieve 4 Ra surface finish
- Not easy to measure surface roughness
loosing aperture from bends and dents
- Low melting temperature ( ~ 1358K)
- Not easy to achieve 4 Ra surface finish
- Not easy to measure surface roughness
- Low conductivity  Plating required
- Technical challenges in machining and
welding
- Requires a post-weld annealing
- Out-gassing surface increased
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Vacuum Chamber Development – Tube option
As-received SS 316L Tube
As-received OFHC Cu Tube
20 x 20m
50 x 50m 100 x 100m 3D-100 x 100m
(24.64nm Ra) (10.07nm Ra) (16.15nm Ra)
20 x 20m
50 x 50m 75 x 75m
3D-75 x 75m
(297.98nm Ra) (317.49nm Ra) (207.98nm Ra)
Performed Cu-Coating tests
with 1-m long SS 316L tube
-
Difficult to coat the copper
Difficult to achieve 4 Ra surface finish
Performed electro-polishing tests
with 12 ft long OFHC Cu tube
-
Not easy to achieve 4 Ra surface finish
Measurement
Instrument
Tube
Materials
As-Received
Roughness (nm)
Cu-Coating
Thickness (m)
After Cu-Coating
Roughness (nm)
After Electropolishing (nm)
AFM (area)
SS 316L
10.1 ~ 24.6
-
-
-
OFE Cu
188.1 ~ 424.5
N/A
N/A
-
SS 316L
48.30 ~ 313.4
7.02 ~ 16.82
378.0 ~ 2,018.0
-
OFE Cu
71.45 ~ 412.5
N/A
N/A
75.3 ~ 386.7
Profilometer
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Vacuum Chamber Development – Box option
Stress Analysis
 Criteria
- Maximum Displacement < 10 m (?)
- Maximum Stress < 69MPa
(Safety factor w.r.t. yield stress:
3.0)
6 mm
Aperture
Remarks6 mm
Maximum
Displacement
0.52 m
Maximum
Stress
8.15MPa
Small aperture
15 mm (H) x 5 mm (V) – Strip
5.86 m
20 mm
41.7MPa
Acceptable
20 mm (H) x 5 mm (V) – Strip
19.2 m
106.4 MPa
Out of criteria
10 mm (H) x 5 mm (V) – Strip
25 mm
10 mm (H) x 5 mm (V) – U-profile
2.22 m
35.8MPa
Small aperture
10 mm (H) x 5 mm
Strip
20 (V)
mmaperture(H) x 5 mm
(V)type
aperture – Strip type
Displacement:
0.52Displacement:
m
Maximum
Stress:
8.15MPaStress: 106.4MPa
12 mmMaximum
(H) x 5 mm
(V) –Maximum
U-profile
3.7219.2
m
m
42.1MPa
Maximum
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
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Global Sensitivity to horizontal aperture size
69 MPa
6 mm
10 m
~102.5 mm
16.7 mm
16.5 mm
15 mm (H) x 5 mm (V) aperture – Strip type
Maximum Displacement: 7.60 m Maximum Stress: 59.9MPa
Global Sensitivity Study
Max. von Mises stress vs. horizontal aperture / Max. displacement vs. horizontal aperture
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Vacuum Chamber Analysis – Support structure
15 mm (H) x 5 mm (V) aperture – Strip with Strong-back Support
Maximum Displacement: 18.88 m
Maximum Stress: 48.3MPa
Applied Loads & Constaints
3D –ProMechanica Model
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Vacuum Chamber Prototypes
Prototype II
I
4 x E-Beam
UHV Welding
Leak Check
I
6 mm  0.1
8 mm  0.2
Machining Both Surfaces
Cu-Coated on mirror-finished
SS 316L strips (1.5 mm thick)
Cu-SS Brazing
II
SS316L
Cu-Cu E-beam Tack
Welding
OFHC Cu
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Undulator Systems Review, March 3-4, 2004
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