SSRF STORAGE RING VACUUM SYSTEM

Report
ALUMINUM ALLOY VACUUM
CHAMBERS FOR SSRF
L.X. Yin, D.K. Jiang, H.W. Du, X.L. Jiang
SSRF Vacuum Group
Shanghai National Synchrotron Radiation Center
SSRF
1
CONTENTS
• Outline of SSRF vacuum system
• Aluminum Vacuum Chambers
– Design
– Fabrication of prototype
– Test
SSRF
2
Vacuum System Structure
AbV-7
X、Y
AbV-4
AbH-6 AbV-5
X、Y、Z
X、Y
X、Y、Z
SSRF
AbH-3 AbH-2 AbV-1
X、Y
X、Y、Z
X、Y
3
Principle of Vacuum System Design
• Antechamber type structure
• Machined and welded aluminum alloy vacuum
chambers
• SR photons are intercepted by OFHC photon
stops except to beamline
• SR irradiate the photon stop surface in
10°angle
• Titanium sublimation pumps are located
beneath the photon stops
SSRF
4
Vacuum System Model
SSRF
5
History of Aluminum Chambers
• Early 1970s
Extrusion
SPEAR, PF
• End of 1980s Antechamber
extrusion SPring8, APS
• End of 1980s
Machining + welding
– Machining upper and lower
halves out of aluminum plate
and welding at the periphery
ALS, PLS, SSRC
SSRF
6
Requirements for SSRF Chambers
• A clean inner surface
q < 6.7×10-10 Pa.m3/s/m2
• Sufficient mechanical strength
Deformation for BPM < 0.03mm
• Flatness < 0.5 mm
• Roughness < 0.8 μm
• Fit relative systems
SSRF
7
Materials
• Aluminum alloy A5083-H321.
–
–
–
–
Nonheat treatable aluminum-magnesium alloy
A small amount of cold work
Stretched and stabilized
Good weldability and dimensional stability
• SS316L--A6061-T6 explosion bonded plates
– Checked by ultrasonic detector
SSRF
8
Structural Design
•
•
•
•
•
•
•
•
Different features on the external surface
Support stages inside the chamber
Enough space between the chamber and the magnets
Conflat® Flange with AL-SS transition material
Helicoflex® gaskets on BPM flanges
Helicoil® screws inside the screw holes
High precision holes for survey
Water-cooling channels in the chamber body
SSRF
9
Chamber Structure (1)
SSRF
10
Chamber Structure (2)
SSRF
11
BM and Chamber
SSRF
12
QM and Chamber
SSRF
13
SM and Chamber
SSRF
14
RF Shielded Flange
SSRF
15
1m-long Chamber model
SSRF
16
Machining
•
•
•
•
•
•
Numerically controlled mill
Dedicated milling cutters
Water soluble metalworking fluid
Spray cooling method
No polish by sandpaper
Constant temperature workshop
SSRF
17
Machining Procedure
• Chamber piece
–
–
–
–
–
Blank the plate
Machine and weld the water - cooling channel
Rough machine the features
Release and keep free
Finish machine in two steps
• BPM hole
– Rough machine
– Assemble the two halves
– Finish machine both of the BPM holes
SSRF
18
Numerically controlled milling
SSRF
19
Cleaning
• Purpose
– Clean surface contamination
– Eliminate the old surface layer
– Form a new surface layer
• Procedure
–
–
–
–
–
Scrub, ALMECO 18, room temperature
Scrub, CITRANOX, room temperature
Scrub, ALMECO 18, 50 - 60℃
Rinse, distilled water
Dry, room temperature
SSRF
20
XPS Test for Sample
Element
Before clean
After clean
C
68.4%
23.6%
O
23.6%
71.2%
Al
8.0%
5.2%
Oxide layer thickness
61.7 Å
A2 Region: Sur
Technique:XPS
Source:Mg K-Alpha
Analyser:CAE=100
Step=0.50
180.0k
160.0k
Relative intensity (c/s)
140.0k
120.0k
100.0k
80.0k
60.0k
40.0k
20.0k
0.0
0
100
200
300
400
500
600
700
800
900
1000
1100
BINDING ENERGY (eV)
SSRF
21
Welding
•
•
•
•
•
•
AC TIG welding with filler
Hand hold
Surface protection from any contamination
Humidity control in workshop
Remove oxide layer
Argon gas flowing inside chamber
SSRF
22
Welding Structure Design
Upper piece
Alumimum tube
Welding edge
Welding edge
Slot
Groove
Lower piece
Chamber body
SSRF
23
Welding Platform
Clamp
Upper piece of chamber
Welding edge
Wedge
Support
Clamp
Lower piece of chamber
Support
Bolt
Bolt
Flatform
SSRF
24
TIG Welding for Chamber
SSRF
25
Welding Crack
Stainless steel(316L)
Alumunum alloy(6061)
Crack
Prolonging pipe(6061)
Chamber(5083)
SSRF
26
Dimensional Inspection
• Flatness (upper surface)
(bottom surface)
• Max. error in transverse direction
• Surface roughness (beam chamber)
(antechamber)
• Max. deformation in vacuum load
SSRF
0.23 mm
0.48 mm
1.4 mm
0.25-0.61μm
0.28-0.80μm
0.28 mm
27
Max. Error in Transverse Direction
SSRF
28
Vacuum Test Results
• Total leak rate(Pa.m3/s)
• Ultimate pressure(Pa)
<4.0×10-10
4.9×10-9
1.7×10-8
• Outgassing rate(Pa.m3/s/m2)
4.1×10-10
• RGA spectrum
No contamination peak in 10-10 Pa
SSRF
29
Pumping Down Curve
1E-5
P1
P2
P3
150¡æBake out
1E-6
Start SIP
Stop bake out
Pressure (Torr)
1E-7
TSP Degas+sublimation
Degas
1E-8
Room temperature
1E-9
1E-10
TSP sublimation
1E-11
0
12
24
36
48
60
72
84
96
108 120 132 144 156 168
time (hours)
SSRF
30
Conclusion
• A complete process for the chamber prototype
manufacture has been performed with acceptable
dimensional accuracy and good vacuum properties.
• Many effects have been taken to solve
corresponding problems.
• A lot of experiences have been accumulated.
• The large aluminum alloy UHV chamber for SSRF
can be manufactured on domestic technology.
SSRF
31
6m-long Chamber Prototype
SSRF
32

similar documents