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

Outline Physical requirements of injector-I Design of prototype cavity Fabrication of prototype cavity Cavity post-processing and test Summary jpdai@ihep.ac.cn

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

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 0.63 178-367 7.68 Ellip 082 0.82 367-1500 85/17 15.47 Spoke Cavities: 3 type, Spoke012、Spoke021、Spoke040 Elliptical Cavities: 2 type（5-cell）, Ellip063、Ellip082 3 jpdai@ihep.ac.cn

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 jpdai@ihep.ac.cn

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) jpdai@ihep.ac.cn

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 jpdai@ihep.ac.cn

Outline Physical requirements of injector-I Design of prototype cavity Fabrication of prototype cavity Cavity post-processing and test Summary jpdai@ihep.ac.cn 7

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 jpdai@ihep.ac.cn

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

EM design with CST-MWS Mechanical design with ANSYS

Geometry Parameters RF Parameter of Spoke012 Parameter Value T 22 W 82 D 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

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

Outline Physical requirements of injector-I Design of prototype cavity Fabrication of prototype cavity Cavity post-processing and test Summary jpdai@ihep.ac.cn 14

Deep-drawing Spoke bar Coupler slice Spoke slice End wall

EBW and leak check for the spoke bars

EBW of the shell and the end wall

Cavity trimming and pre-tuning

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

Outline Physical requirements of injector-I Design of prototype cavity Fabrication of prototype cavity Cavity post-processing and test Summary jpdai@ihep.ac.cn 20

Experiences from BEPCII 500MHz cavity, 9-cell large-grain cavity of IHEP and other cavities 21 jpdai@ihep.ac.cn

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 jpdai@ihep.ac.cn

New chemistry site for cavity production Hall: 36m12m7m Daxing district, 42km from IHEP 23 23 jpdai@ihep.ac.cn

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

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

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. jpdai@ihep.ac.cn

Thanks for your attention! jpdai@ihep.ac.cn