1. Chamber & Vacuum System
Dean R. Walters
Soon-Hong Lee, James Bailey, James Morgan, Dana Capatina, Scott Doran, ANL
Lou Ann Tung, LLNL

3. Production Vacuum Chamber Ass’y
X-Adjustor
Z-Adjustor
Support Assembly
Vacuum Chamber Assembly

4. Measurement results of magnetic permeability (r)
6/29/2019
Measurement results of magnetic permeability (r)
Material
As-received condition
After vacuum annealing
After machining & forming
After TIG welding
After final machining
316LN
1.002a (1.004b)
1.003a (1.003b)
1.004a (1.003b)
1.008c (1.003d)
310S
1.057e (1.005f)
1.036e (1.003f)
1.033e (1.003f)
1.042e (1.018f)
1.051c (1.007d)
20Cb-3
1.007e (1.008f)
1.008e (1.015f)
1.008e (1.015 f)
1.010e (1.011f)
1.018c (1.009d)
Nitronic 33
(1.002g)
1.022e (1.006f)
1.030e (1.012 f)
1.030e (1.023f)
1.126c (1.033d)
Nitronic 40
1.004e (1.003h)
1.003e (1.004 h)
1.005e (1.004 h)
1.019e (1.052h)
1.081c (1.048h)
Initial Calibration, 1.27±0.01
1.272
1.276
1.275
1.277
Note on thickness a: 1.99 mm, b: 6.65 mm, c: 0.5 mm, d: 6.0 mm, e: 1.59 mm, f: 6.35 mm, g: 7.94 mm, h: 4.76 mm
Anneal conditions
Vacuum pressure at 1.0 x 10-4 Torr
1,750 º F for 30 minute soaking on 20Cb-3 and 1,950 º F for 30 minute soaking on the other types
Rapid Nitrogen gas quenching
316LN had stable permeability values of less than 1.010, even if cold-works and welding.
310S and Nitronic 40 had increased in permeability after welding significantly.
20Cb-3 had acceptable permeability values less than (most less than 1.010) and good welding characteristics (less heat-affected zone)
Nitronic 33 and 20Cb-3 had increased in permeability after annealing.
This Table summarizes the permeability measurement results under the fabrication processes of the vacuum chamber
and represents the permeability in terms of the sample thickness.
Data in parenthesis refer to the true permeability of the holding arm, which were converted from the measured in the different thickness.
Others refer to the true permeability of thin-walled area, which were converted from the measured.
Samples received from the vendor had low permeability values of less than
After annealing, the permeability was measured again. The results showed Nitronic 33 and 20Cb-3 had increased in permeability
After forming and machining. permeability changes were not significant. Nitronic 33 samples showed the most changes.
After TIG welding, the permeability of 310S and the Nitronic series had increased, but no changes in 316LN.
Although 20Cb-3 had a small increase in permeability, it had a very narrow heat-affected zone (HAZ) which indicated good weldability.
Furthermore, vacuum chamber weldments were machined to have holes with a 6 mm vertical dimension.
The permeability in the holding arm area had decreased, except in Nitronic 40.
But, in the thin-walled area on the top and bottom, all samples had increased in permeability except Nitronic 40.
Because the Ferromaster permeability meter is very sensitive to sample thickness,
especially when less than 2 mm, the last two columns in Table represent results very difficult to analyze.
The calculation from measured to true permeability is possibly biasing the results as a result of using the final dimensions
after the last machining step.
Anyhow, throughout the fabrication studies, we confirmed that 316LN is only the material without any practical changes in permeability
and that 20Cb-3 has low permeability and good weldability.
Test

5. Measurements of the changes of applied magnetic fields
6/29/2019
Measurements of the changes of applied magnetic fields
Sample chambers under APS undulator "A"
A 3-inch-long sample vacuum chamber was inserted Into a hybrid permanent magnet undulator with a 3.3 cm period and 8 mm min. gap
To Investigate high magnetic field influence to the relative magnetic permeability
Peak of applied magnetic field: ~ 1.2 T
B/B < 1.5 x10-4
Undulator A
8.0 mm
To investigate high magnetic field influence to relative magnetic permeability,
a 3-inch-long vacuum chamber sample was inserted into APS undulator A with an 8 mm gap.
Then, we measured and compared the relative changes in applied magnetic fields at peak point
with/without 3-inch-long vacuum chambers.
In this application, we applied a peak magnetic field of 1.2 Tesla and
the acceptable range of the relative change of applied magnetic field is B/B < 1.5 x10-4.
Based on the results of the changes to the applied magnetic field,
all vacuum chamber materials can be considered suitable for the LCLS vacuum chambers.
Especially, 316LN and 20Cb-3 showed less 1 Gauss change with / without a sample chamber
Hall probe holder
Sample chamber
Test

6. Fabrication Processes
SST Plate, End Cap (144” x 7.5” x 1”) (144” x .5” x.25”) 20Cb-3
SST Sheets (144” x .75” x .120”) LN SST
Milling/Polishing
Polishing/Milling
Seam Welding
Final Machining
Cleaning/Baking
Coating

7. Prototype Vacuum Chambers
Compound screws (Brass Screws & SST )
Vacuum Chamber
NW 50 Flange -Clamp Type (316L SST)
Top & Bottom Strips (316LN)
Chamber Strong-back (20Cb-3)
End Cap (20Cb-3)
Prototype A
Top & Bottom Strips (20Cb-3)
Chamber Strong-back (316 SST)
End Cap (20Cb-3)
Prototype B

8. SUT Machining Results Material: Austenite stainless steel 316
Supplier: Walco Tool & Engineering
Parallelism of chamber surfaces (0.100 mm): mm
Thickness of chamber (6.00 ~ 6.08 mm) : max mm
Straightness of chamber edge (± mm) : max mm bowed
Vibratory or thermal stress relief is required, which may restore the original properties of the base metal E H

9. Prototype B Machining Results
Material: Austenite stainless steel 316
Supplier: Dial Machine Inc. (measured Aug. 8, 06)
No attempt was made to tweak in, or adjust, the constrained condition to improve the results.
Flatness of nose bottom surface in the clamped condition (0.100mm): 0.314mm
Parallelism of nose bottom surface to strongback bottom in the clamped condition (0.100mm): mm
Parallelism of nose top surface to nose bottom surface in the clamped condition (0.100mm): mm
Straightness of chamber edge (180.0± 0.20mm) : ~179.70mm (0.160mm bowed)
Thickness of chamber every 12” in the clamped condition (5.0±.08mm) : 4.945~5.112mm
Flatness of the surface of machining fixture in the strongback clamped condition: 0.04mm
Flatness of the bottom surface of strongback in the free state: 1.143mm

10. Polishing of Stainless Steel
Samples of True #8 stainless steel sheets from Pacific Plus Inc. of Dallas, TX / Hwa Yang Stainless Steel Group in China.
True #8 and super #8 are trademarks of Pacific Plus International, Inc.
1.5 mm thick 316 SST sheets (1 ft x ft) and 0.5 mm thick 304 SST sheet (4 ft x 8 ft) were bought to evaluate the impact of manufacturing operation on the surface finish.
Samples were polished at Fine Art Inc. and Polished Metals Limited.
Measurements
Used Tencor Alpha-Step to obtain a 2D surface profile.
Used MicroXAM RTS surface profiler (White light interferometry)
MicroXAM RTS from

11. Evaluation of Roughness Scans - Polished
Sample: #PLM 2
Mode: PM
Objective: 50x
Size: x mm2
# 8
r(z): mm; hrms: nm
x’rms: mrad; z’rms: mrad
Sampled Data (1024x1024)
Lineout (x: #200; z: #300-#400)
Full Spectrum (1024x1024)
Sampled Data (500x500)
Full Spectrum (500x500)
Size: x mm2
WLI
AFM
r(z): mm; hrms: nm
x’rms: mrad; z’rms: mrad
For wakefield considerations, the beam- (or z-) direction is the most important and all measurement results are within tolerance, i.e., have rms derivatives in z of less than 10 mrad.

12. CO2 Laser Weld Prototyping Inspection Results for Sample 3
Intermittent weld
Seal weld
Groove

13. CO2 Laser Weld Prototyping 42” Vacuum Chamber Prototype
Fixturing for end cap welding
Fixturing for strong back welding
Welding strong back
Welding end cap

14. Final Machining Prototyping
Machined to red line both sides
Vacuum Chamber Gap
Actual Weldment

15. Final Machining Prototyping
Preliminary Inspection Results for the 42” Prototype
<0.002” Flatness & <0.002” Tolerance on Thickness

16. Coating Basics

17. Test set up operating Coating inside a 7.9 mm Glass tube

18. Prototype Development
May
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Jan.
Feb.
2006
2007
42” Prototype
Parts
Proc. 304 SS & Mach.
Fixtures (Weld)
Design & Fab.
Assembly
Weld
Mach
Coat
Laser Weld Development
6” Samples
ANL
18” Samples
Vendors
Final Mach. Development
6” Samples
ANL
Fixtures (Mach)
Design & Fab.

19. Prototype Development
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Jan.
Feb.
2006
2007
Apr.
Prototype A
Strongbk.
Strongbk.
Strongbk.
Strongbk.
Strongbk.
P.O.
20Cb-3 Mach.
End Cap
End Cap
End Cap
End Cap
End Cap
Proc. 20Cb-3 & Initial Mach.
Side Walls
Side Walls
Side Walls
Side Walls
Side Walls
Polish Sheet
Intl. Mach.
Weldment
Weldment
Weldment
Weldment
Weldment
Fab. Fix. & Weld
Mach/ Coat
Prototype B
Strongbk.
P.O.
Proc. 316 L & Initial Mach.
End Cap
Proc. 20Cb-3 & Initial Mach.
Side Walls
Polish Sheet
Intl. Mach.
Weldment
Fab. Fix. & Weld
Mach/ Coat

20. Prototype Development
May
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Jan.
Feb.
2006
2007
Coating Development
Consultant
Agreement
Place PO
1St
Part #2
Equipment
Design
Procure
Assy
Full Size Setup
Power Supply
Loan Agr
Ship
Install
Process Dev
Bench Test
42” Prt

21. Chamber Schedule

22. Chamber Design Review
The LCLS undulator vacuum chamber and system were reviewed by a committee composed of John Grimmer, APS, Nadine Kurita, SLAC, Allan Rowe, FNAL, and John Noonan, ANL, chair on September 27 and 28, 2006
Schedule
The schedule for fabrication and delivery of vacuum chambers for the undulator vacuum system is tight, especially for the undulator vacuum chamber. This is a complex part with stringent physics requirements, especially the surface finish. Aspects of the chamber are demonstrated, but a full-size prototype will not be complete until December, 2006.
The Undulator Vacuum Chamber
There are no technical barriers to fabrication of the chambers. However, there are tooling and detailed fabrication issues that need to be answered in order for production to proceed. Successful chamber fabrication will be a significant accomplishment. The physics are stringent
Fabrication of the full size prototype chamber is essential and the engineers should have all the APS and LCLS support that they need to complete the fabrication. The full size prototype will determine vacuum integrity, outgassing rates for the chamber, coating surface finish, and dimensional straightness. It is important to perform a test in which the full size chamber is installed in an undulator and its straightness measured. The survey groups need to be involved in the tests and certify that the installation procedure is reasonable.
Magnetic measurements need to be repeated on the 20Cb-3 steel. The 20Cb-3 material has no apparent pedigree in demanding vacuum and magnetic applications. The prototype has not yet been welded leak tight and will clearly be "worse" than 316LN in magnetic performance, although the effect of the difference is debatable.

23. 6 Month Look Ahead Prototypes Production
42” Prototype Complete Nov. 20
Full Length Prototype A Jan. 25
Full Length Prototype B Jan. 20
Production
First Lot Strongbacks Material Nov. 10
First Lot Strongbacks Machining Jan. 19
Side Wall Machining Jan. 10
End Cap Machining Jan. 19
First Lot Laser Welding Feb. 20
First Lot Final Machining Mar. 16
First Lot Vacuum Processing and Coating Mar. 30
Second Lot Strongback Material Jan. 25
Second Lot Strongback Machining Mar. 7

24. Vacuum System Calculations
Mathematica model based on location increments of 1 cm long in order to determine the system pressure profiles.

25. Vacuum System Calculations
In past hand vacuum calculations have been used to estimate the vacuum system performance
Recently a collaboration with LLNL has been established to provide calculations.
Below are the results obtained at this point.
The next analysis will include:
-Add in the turbo and roughing pumps (with S(p)) in the long break
and an ion pump in all three breaks
-Put in the time-dependent outgassing rate for stainless steel (already have fit)
-Put in the different rates for copper and aluminum

26. (Short break is the same but without the valve spool)
Long break layout
(Short break is the same but without the valve spool)

27. Pressure profile with one ion pump on the long break with one undulator section
Dz = 1 cm
All surfaces outgas at
1.6 x T-l/s/cm2 cm
One undulator section
Long break

28. Conclusions
Chambers
This has not progressed as expected. The Strongback delay has rippled through the prototype schedule and it impacts the production schedule.
The Design Review Committee has agreed that the Strongback can enter production, but testing is needed on the full sized prototypes to continue with the production of the whole weldment.
These Prototypes must be done before the end of January so that the production units are not impacted.

29. End

30. CO2 Laser Weld Prototyping 42” Vacuum Chamber Prototype
Results in Constraint Condition
0.000”
0.001”
0.001”
0.000”
0.000”
0.002”
0.001”
-0.001”
0.002”
0.000”
0.001”
0.001”
0.000”
0.000”
0.000”
0.001”
Flatness Variation Along Center of Wall Sheet
Across Sheet Flatness <0.001”

31. Vacuum Chamber alignment
6/29/2019
Vacuum Chamber alignment
Vertical Adjustment Screws (14)
Test

32. On Going Work Test Set up 42” chamber Full size setup Cathode Guides
Straightening of Cathodes
Tensioning of Cathodes
Vertical positioning
42” chamber
Full size setup
Vertical Coating Stand