1. SC cavity development for C-ADS @ IHEP Jianping Dai RF group, Accelerator Center, IHEP International Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China

2. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 1 Outline 1.Physical requirements for SC cavities 2.R&D of elliptical cavities 3.Design study on low beta spoke cavities 4.Scenario of SC cavity development for C-ADS 5.Summary

3. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 2 Layout of the C-ADS Linac 1. Physical requirements of C-ADS Linac Main linac

4. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 3 1. Physical requirements of C-ADS Linac (Injector-I) Cavity typeFreq. (MHz) gg Energy (MeV) # of Cavity /CM Max. V acc. (MV) Injector I (3-half β ) Spoke011T +Spoke021 325 0.3 +0.21 3.2-108+4/11.45/0.7 Injector I (1-half β ) Spoke0123250.123.2-10 18/2 or 13/1 0.63 or 0.84 Main Linac Spoke 0213250.2110-3428/71.32 Spoke 0403250.4034-17872/92.79 Ellip 0636500.63178-36728/77.68 Ellip 0826500.82367-150085/1715.47 Spoke Cavities: 3 type, Spoke011T(or Spoke012) 、 Spoke021 、 Spoke040 Elliptical Cavities: 2 type （ 5-cell ）, Ellip063 、 Ellip082

5. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 4 f (MHz) R/Q (Ω) Vacc (MV) Ep (MV/m) Bp (mT) T (K) Q0Pc (W) 18*Pc (W) 325130 0.6327.4402.0 1  10 10 0.315.5 0.5  10 10 0.6211.2 0.8436.553.42.0 5  10 9 1.119.5 1  10 9 5.497 Heat load of Spoke012 f (MHz) R/Q ( Ω ) Vc (MV) Pb (kW) Qe  f (Hz) 3251300.635.6 5.5  10 5 591 Bandwidth of spoke012

6. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 5 Why we choose spoke cavities?  Two candidates for low energy protons Half Wave Resonators ( by IMP ) Spoke Cavities (by IHEP)  Only two different frequencies in the Linac  Inherent advantages of spoke cavities

7. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 6 Challenges of low beta spoke cavities(I) I. Naturally larger values of df/dp II. Limited by beam dynamics, smaller space for ribs and tuner Low beta spoke cavities have smaller areas of high magnetic fields, thus present larger df/dp compared with medium beta SSR Up to now, no low beta Spoke cavity developed III. Very high Eacc (Vacc=0.84MV=>Ep=43MV/m, Bp=55mT for SSR0 of Project-X)

8. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 7 Challenges of low beta spoke cavities (II) Q0= 5  10 9 at 2.0K:  Eacc=5MV/m=>Ep=12.8MV/m&Bp=19.4mT for SSR1-01  Eacc=18MV/m=>Ep=46.1MV/m&Bp=69.7mT for SSR1-02

9. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 8 Challenges of medium beta Elliptical cavities  High magnetic shape => High Bp/Eacc, Weak mechanical stability  650MHz, 5-cell => Large dimensions

10. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 9  Start from June 2000, mainly from 2005 to 2007 2. R&D of elliptical cavities @IHEP  The fundamental infrastructure for SC cavities constructed  Work focused on 1.3GHz, beta=0.45, single cell elliptical cavity  Recent work on 650MHz, beta=0.45, single cell elliptical cavity

11. Clean room HPR BCP CBP VT crymodule （ 1.3GHz/700MHz VT stand 2K pumping system LLRF system RF source Facilities in 2007 230m 2 finished in 2004 The fundamental infrastructure

12. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 11 Present facilities 11

13. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 12 Three 1.3GHz, beta=0.45, single cell elliptical cavities were designed, fabricated, processed and Vertical test Mechanical and RF parameters The fabricated 3 cavities

14. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 13 Vertical test results 1.3GHz/β=0.45 1st: BP(20  m)+CP(80  m)+Anealing+CP(80  m)+HPR(1.5hr.)+Baking(120 ℃, 48hr.) @IHEP 2nd: CP(100  m)+HPR(2hr.)+Baking(120 ℃ 48hr.) @IHEP 3rd: Only evacuation after transfered from IHEP to KEK @KEK 4th: EP(80  m+3  m)+HF+HPR+Baking(120 ℃ 48hrs.) @KEK 表面电阻与温度曲线 表面峰值梯度测量曲线 42.4MV/m

15. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 14 Para.Mid-Cell (mm) r iris 40 R200 L51.884 A32 B48 LeLe 1.42 a9.4 b11.22  55 E p /E acc (void)3.17 H p /E acc mT/(MV/m)5.52 r/Q [  ] 35 G [  ] 140 k (cell to cell coupling)1.0% Fabricated at IHEP workshop Design and half-cell forming of the 650 MHz Single-cell Beta0.45 Cavity

16. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 15 3. Design study on low beta spoke cavities II. MWS and ANSYS/Solidworks are used for the optimizations: (Ep/Eacc, Q, R/Q) III. Two types of Spoke cavities were designed and compared Traditional Spoke012 Spoke009T I. According to the basic requirements and referring the designs of other spoke cavities, we got the preliminary EM design of our spoke cavity

17. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 16 Details on RF design of Spoke012 (I)  RF simulation settings: 100 lines/wavelength, ~4 million mesh cells.  E acc is calculated as V acc / L iris  R/Q 0 =V 2 acc /ωU @ Optimum β Magnetic field Electric field

18. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 17 Details on RF design of spoke012(II)  The dimensions of Lcav, T, W, D1, D2 and D were optimized Ep/Eacc vs. T  The cross section of the spoke was optimized. LeftMiddleright G (Ω)697472 R/Q 0 (Ω)@βg117124118 E peak /E acc 3.903.483.39 B peak /E acc (mT/(MV/m)) 4.413.944.23

19. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 18 Typical results of Spoke012 LcavLirisTWDcavDbeamD1D2A1A2 mm1707429894383581219110280 LcavfGR/Q@β opt Ep/EaccBp/EaccTtran 170mm325.0MHz53Ω150Ω3.194.66mT/MV/m0.77

20. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 19 Details on Mechanical design of spoke012  The material properties of niobium we used: Density=8560 kg/m 3, Young’s modulus=107 GPa, Poisson ratio=0.359, shell thickness=3.5 mm.  Two steps: without/with stiff ribs  Simulation settings: 1/8 cavity, tetrahedral mesh cells (5mm),

21. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 20 External load (I) The external load: 1 atm (760 torr) Frequency shift: -13.7MHz The peak displacement:4.47mm The peak stress: 212 MPa, (> 50 MPa (yield strength) Without ribs and beam pipe free

22. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 21 External load (II) Without ribs and beam pipe fixed The peak displacement:0.36mm The peak stress: 440 MPa, (> 50 MPa (yield strength)

23. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 22 Tuning sensitivity 1.319MHz/mm, 0.577mm/100kgf Displacement of Pushing Displacement of Pulling

24. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 23 Lorentz force detuning (static) 23 The Lorentz detuning coefficient: -25.8 Hz/(MV/m) 2 Displacement stress is outwards here stress is inwards here

25. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 24 6 different ribs were simulated (a) (b) (c) (d) (e) (f)

26. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 25 Mechanical properties with/without ribs for spoke012 Without ribsWith ribs (scheme e) Beam pipe free 4.47mm/bar -13.7MHz/bar Von stress=212MPa  f/  p= -18kHz/torr 0.423mm/bar -1.04MHz/bar Von stress=56MPa  f/  p = -1.4kHz/torr Beam pipe fixed 0.359mm/bar -402.29kHz/bar Von stress=440MPa  f/  p= -530Hz/torr 0.08mm/bar +6.5kHz/bar Von stress=65MPa  f/  p= -8.5Hz/torr Tuning sensitivity 0.577mm/100kgf 761.3kHz/100kgf 1.32MHz/mm 0.052mm/100kgf 68.6kHz/100kgf 1.32MHz/mm Lorentz force detuning-25.83Hz/(MV/m) 2 -3.2Hz/(MV/m) 2

27. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 26 Idea of spoke009T (By J. Tang & Z. Li)  The gap-center to gap-center length is 3*  /2, not traditional 1*  /2  The spoke center thickness is larger, so smaller gap Cross section of Spoke009T Cross section of Spoke012

28. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 27 Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China 27 Dimensions of Spoke009T & Spoke012 Lcav (mm) Liris (mm) T (mm) W (mm) Dcav (mm) D1 (mm) D2 (mm) Spoke009T26016080120476120288 Spoke01217074298943881219

29. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 28 Comparison of RF parameters RF parametersSpoke009TSpoke012 f (MHz)325 R/Q （ Ω ） @β opt 190150 Ep/Eacc*9.33.2 Bp/Eacc* (mT/MV/m ） 14.64.6 G （ Ω ） 7053 Ttran0.40.77 *Eacc=Vacc/Liris

30. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 29 Transit time for different β Spoke009T Spoke012

31. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 30 Different E-fields for the Spoke009T and Spoke012 Traditional Spoke012 Spoke009T

32. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 31 Comparison of mechanical parameters Conclusions:  With same Vacc, Spoke009T needs more cryogenic power because of lower transit time (factor of 3-4)  Spoke009T has better  f/  p (factor of ~3) Mechanical propertiesSpoke009TSpoke012  f/  p (pipe free, no ribs) 6.8kHz/torr18kHz/torr Tuning sensitivity620kHz/mm1319 kHz/mm

33. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 32 4. Scenario of SC cavity development for C-ADS  Tight schedule, especially for low beta cavities (~2 years)  Ambitious technical target  Not experienced Collaboration with experienced Labs in abroad and domestic. Do the work in parallel. More man power and more money

34. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 33 Contract for the development of prototype cavities was signed on August 31, 2011 at Harbin

35. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 34 Investigation of the cavity fabrication  All parts of the cavity are formed by machining or deep-drawing  Need to be chemically cleaned before assembling  Assembled by EBW to be a whole cavity Pickup port Coupler port Spoke bar End wall Stiffener Clean hole 450MHz ，  =0.2 spoke cavity (PKU&HIT)

36. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 35 Visiting FNAL/ANL/MSU for collaborations

37. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 36 Other potential collaborators for cavity fabrication  PAVAC INDUSTRY INC, Canada  Niowave, America Collaborations with FNAL/ANL/MSU are expected

38. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 37 Investigation of the cavity surface processing Before each EBW, pieces are cleaned Cavity is immersed in a bath of UPW with a degreasing agent and ultrasonically cleaned BCP (~100um) HPR Annealing (~800 o C) BCP (~20um) HPR

39. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 38 Vertical test of the prototypes  Test @IHEP, ~June 2012  Prototype cavity test @FNAL (2K system)

40. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 39 Summary  3 types of spoke cavities and 2 elliptical cavities are needed for China ADS Linac, and the spoke cavity for 3~10MeV injector is most challenging.  Supported by the R&D project for ADS, the fundamental infrastructure was constructed @IHEP and experiences on elliptical cavity got  RF and Mechanical properties of spoke012 and Spoke009T were preliminary studied and compared.  The fabrication, surface processing and vertical tests were investigated.  The collaborations with PKU&HIT were fixed, and collaborations with FNAL/ANL/MSU etc. are expected.

41. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 40 Thanks for your attention!

42. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 41 Microphonics for spoke014  The beam tube ports are fixed.  ½ cavity, the first 5 mechanical oscillation modes calculated. modef(Hz) 197 2175.43 3265.85 4369.51 5445.4

43. Inter. Review Meeting on C-ADS Acc. Phys. Design, Sept. 19~20, 2011, IHEP, Beijing, China jpdai@ihep.ac.cn 42 Multipacting simulation for spoke012