1. SC spoke cavity for China-ADS 3~10MeV injector
Jianping DAI, Hong HUNAG, Peng SHA, Qunyao WANG, Han LI
RF group, Accelerator Center, IHEP
November 6, 2012

2. Outline Physical requirements of injector-I Design of prototype cavity
Fabrication of prototype cavity
Cavity post-processing and test
Summary

3. Spoke012 cavities are used
Main linac
Spoke012 cavities are used
in this section
Layout of the China ADS Linac

4. Spoke Cavities: 3 type, Spoke012、Spoke021、Spoke040
Cavity type
Freq. (MHz) g
Energy (MeV)
# of Cavity /CM
Max. Vacc. (MV)
Injector I
Spoke012
325
0.12
3.2-10
12/2
0.78
Main Linac
Spoke 021
0.21
10-34
28/7
1.32
Spoke 040
0.40
34-178
72/9
2.79
Ellip 063
650
0.63
7.68
Ellip 082
0.82
85/17
15.47
Spoke Cavities: 3 type, Spoke012、Spoke021、Spoke040
Elliptical Cavities: 2 type（5-cell）, Ellip063、Ellip082 3

5. Layout of the 5MeV injector
Cavity type
Freq. (MHz) g
Energy (MeV)
# of Cavity /CM
Max. Vacc. (MV)
Injector I
Spoke012
325
0.12
3.2~10
12/2
0.78
Q0=0.3~11010
Qe=7105 4

6. Why we choose spoke cavities?
Inherent advantages of spoke cavities
Only two different frequencies in the Linac
Two candidates for low energy protons
Half Wave Resonators ( by IMP )
Spoke Cavities (by IHEP)

7. Challenges of low beta spoke cavity
I. Naturally larger value of df/dp
Low beta spoke cavities have smaller areas of high magnetic fields, thus present larger df/dp compared with medium beta SSR
II. Limited by beam dynamics, smaller space for ribs and tuner
III. Multipacting barrier
Up to now, no very-low beta(~0.1) spoke cavity developed

8. Outline Physical requirements of injector-I Design of prototype cavity
Fabrication of prototype cavity
Cavity post-processing and test
Summary 7

9. IHEP-PKU-HIT joint group=>
EM and mechanical design-PKU&IHEP
Fabrication-HIT&PKU&IHEP
Post processing and Test-IHEP
IHEP-PKU-HIT joint group=>
Contract signed on August 31, 2011 at Harbin 8

10. By the end of November, 2011，the EM optimization and mechanical design of Spoke012 were finished.
The design work was reviewed on December 8, 2011

11. EM design
with CST-MWS
Mechanical design
with ANSYS

12. Geometry Parameters RF Parameter of Spoke012 Parameter Value T 22 W 82D 90
Factor
1.25
R1in 47
R2in
199
R1out 35
R2out
164
Lcav
180
Liris 73 R
234
Parameter
Value
Frequency
325 MHz G
61 Ω
R/Q0
142 Ω
Epeak/Eacc
4.5
Bpeak/Eacc
6.4 mT/(MV/m)
Effective length for Eacc is defined as βλ

13. Mechanical properties of the prototype cavity
Ports free or locked
Stiff ribs
At 1 atm
df/dP (kHz/torr)
Peak deformation (mm)
Peak stress (MPa)
Frequency shift (MHz)
Free No
3.256
157
-8.28
-10.9
Locked
0.218
389
-0.21
-0.278
1st
0.11
<44.3
0.049
0.065
<45.6
-0.044
-0.058
2nd
0.848 89
-1.7
-2.24
118
0.014
0.018

15. Outline Physical requirements of injector-I Design of prototype cavity
Fabrication of prototype cavity
Cavity post-processing and test
Summary 14

16. Deep-drawing
Spoke bar
Coupler slice
Spoke slice
End wall

17. EBW and leak check for the spoke bars

18. EBW of the shell and the end wall

19. Cavity trimming and pre-tuning

20. Two cavities (Ribs and flanges not welded)
Shell and end wall
Two cavities (Ribs and flanges not welded)

21. Outline Physical requirements of injector-I Design of prototype cavity
Fabrication of prototype cavity
Cavity post-processing and test
Summary 20

22. Experiences from BEPCII 500MHz cavity, 9-cell large-grain cavity of IHEP and other cavities21

23. Prototype cavity post-processing and test
Incoming
Inspection
Dimension RF
Thickness
Measure
Bulk
Chemistry
Degrease
Heat treat
(600oC)
RF tuning
Light
High Pre.
Rinse
1st
Assembly
2nd
Leak
Check
120oC bake
24 hours
Vertical
Test
Disassembly
He vessel
Welding
Flange
Lapping
Horizontal 22

24. New chemistry site for cavity production
Hall: 36m12m7m
Daxing district, 42km from IHEP 23 23

25. SC Cavity Post Process Facilities @ Daxing district
LINAC 12
Institute of High Energy Physics, Chinese Academy of Sciences 24

26. The vertical test shall be done at the end of 2012.
Qe of pickup in the V-test
Assembly of vertical test
The vertical test shall be done at the end of 2012.
LINAC 12
Institute of High Energy Physics, Chinese Academy of Sciences 25

27. Summary
3 types of spoke cavities and 2 elliptical cavities are needed for China ADS Linac
The spoke012 for 3~10MeV injector is the most challenging because of its tight schedule, lack of experience and ambitious technical target.
Design and fabrication of Spoke012 prototype have been finished by IHEP-PKU-HIT joint group
Another two Spoke012 cavities will be fabricated by PAVAC and tested at TRIUMF next year
The post-processing and vertical test of the prototype cavity should be finished at the end of this year.

28. Thanks for your attention!