Double Quarter Wave Crab Cavity Qiong Wu On

Double Quarter Wave Crab Cavity Qiong Wu On behalf of the DQWCC team 11/14/2012 The Hi. Lumi LHC Design Study is included in the High Luminosity LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.

Outline • Current Design • Cavity parameters • Higher Order Mode (HOM) damping • Stiffening • Helium Vessel • Fabrication Status • Future plan 11/14/12 • Summary 2

Crabbing (fundamental) mode freq. 1 st HOM Cavity length Cavity width Beam pipe diameter Deflecting voltage Unit MHz cm cm cm MV DQW crab cavity 400 579 38. 4 14. 2 8. 4 3. 3 11/14/12 The Double Quarter Wave Crab Cavity 3

Cavity Dimensions 11/14/12 unit: mm 4

Cavity Field 11/14/12 Electric field (left) and magnetic field (right) of fundamental mode. 5

B Cavity Parameters Unit DQWCC Fundamental Mode Frequency MHz 400 Nearest Mode Frequency MHz 579 Vertical Deflection Voltage MV 3. 3 Rt/Q (Fund. Mode) Ohm 400 Epeak MV/m 48** Bpeak m. T 67** Vacc k. V 1. 7 J 13 Energy Content **Might have some decrease in electric field on the cavity and increase of magnetic field at the port opening (ACE 3 P) 11/14/12 E 6

Electric field HOMs deflection mode horizontal mode 11/14/12 longitudinal mode HOM Damping 7

11/14/12 HOM couplers 8

HOM frequency [GHz] Mode Config. R/Q [Ω] Qext 0. 579 Longitudinal 108 1130 0. 671 Horizontal 70. 5 2340 0. 700 Hybrid (y, z) 0. 24/0. 25 1140 0. 752 Deflection 34. 9 1750 0. 800 Horizontal 6. 02 e-4 3160 0. 917 Horizontal 30. 9 2050 0. 949 Longitudinal 28. 1 3180 1. 080 Deflection 1. 54 1240 1. 102 Horizontal 1. 84 e-3 1380 1. 114 Deflection 1. 06 1380 1. 202 Horizontal 5. 07 e-2 7880 1. 247 Hybrid (y, z) 8. 0 e-2/6. 0 e-2 1730 1. 291 Deflection 10. 0 926 11/14/12 HOM Damping 9

Stiffening Crab cavity max stress intensity vs Nb thickness (bare cavity only) 90 80 Pressure: • 2 e 5 Pa (2 bar) outside • vacuum inside. 70 60 50 Fixed Support: One side of beam port. 40 30 20 10 0 1 2 3 4 Thickness of Nb [mm] 5 Nb property for reference: • Density: 8. 58 e-3 g/mm^3; • Yield-RT: 4. 83 e 7 Pa (7 e 7 Pa 6 for 300 RRR Nb) • Yield-Cryo: 5. 77 e 8 Pa. 11/14/12 Max Stress Intensity [10 MPa] 100 Nb property: • Modulus @ RT: 1. 03 e 11 Pa • Modulus @ Cryo: 1. 23 E 11 Pa • Poisson’s Ratio: 0. 38 10

Stiffening Cont’d 11/14/12 • Stiffening plates and frames are added to the cavity for vertical cold tests. • The material for stiffening components can be either Nb or Ti. • The thickness of the stiffening plates is 4 mm, and the frame is 25 × 25 mm^2 in cross section. • The only welding needed is the straight section on top and bottom of the stiffening plates. 11

Courtesy of Luís Alberty 11/14/12 Cavity stress simulation for 2 e 5 Pa (2 bar) outside + vacuum inside. 12

• Stiffening material: Ti • Nb to Ti transition by serrated surface plus SS bolts • SS bolts and pins at frame connections 11/14/12 Mechanical design of stiffening 13

• Preliminary design of the helium vessel • The vessel will play a role in stiffening the cavity • Clearance for other beam lines in the vicinity. • Simple machining and welding • Compact design which saves LHe 11/14/12 Helium Vessel 14

11/14/12 Cavity stress simulation for 2 e 5 Pa (2 bar) outside + vacuum inside. 15

Fabrication Status 11/14/12 Courtesy of Niowave Inc. 16

Plan for 2012 -2013 • The design of the cavity is complete. • Fabrication of the cavity with stiffening frame is in progress. • We expect the fabrication to be complete at the end of calendar year 2012. • Chemistry and HPR will be done right after the fabrication of the cavity. • Vertical testing, first without HOM couplers then with HOM couplers will be carried out through early 2013. 11/14/12 • The testing will be focused on o Deflection voltage o HOMs o Peak fields o Possible multipacting 17

Prototype fabrication and testing • Fabrication and testing of the cavity and its various RF couplers (FPC, pick-up, HOM) will include: Ø Cavity fabrication Ø HOM coupler (two units) Ø Fundamental Power Coupler and pickup Ø Chemistry and HPR Ø Vertical testing (2 rounds) Ø LLRF • DQWCC project team @ BNL: Qiong Wu, Binping Xiao (Postdoc), John Skaritka, Vito De Monte, Sergey Belomestnykh, Ilan Ben-Zvi, Silvia Verdu Andres (Postdoc starting in Jan. 2013) 11/14/12 • Collaboration & Support: Rama Calaga (CERN), Luís Alberty (CERN), Zenghai Li (SLAC) 18

Summary • The DQWCC can provide high deflection voltage in a very compact dimension. • The peak surface field of the cavity is in a safe level at the target deflecting voltage. • It is optimized for LHC installation so that no conflict to the adjacent beamlines. • The fabrication of the cavity will finish before the end of 2012, and pre-testing treatments will start right after. • Large separation between fundamental deflection mode and 1 st HOM simplifies the design in HOM damping scheme and high-pass filter design. • Close collaboration with other LARP participants profits greatly to the cavity design and fabrication. 11/14/12 • We are looking forward to testing the prototype Nb cavity in the year of 2013. 19

Acknowledgement 11/14/12 Work supported by the US LHC Accelerator Research Program (LARP) through US Department of Energy contracts DE-AC 02 -07 CH 11359, DE-AC 02 -98 CH 10886, DE-AC 0205 CH 11231, and DE-AC 02 -76 SF 00515. 20

Reference • Q. Wu, et. al. , HOM Damping and Multipacting Analysis of the Quarter-wave Crab Cavity, Proceedings of IPAC 12, New Orleans, LA, May 20 -25, 2012 • R. Calaga, et. al. , A Quarter Wave Design for Crab Crossing in the LHC, Proceedings of IPAC 12, New Orleans, LA, May 20 -25, 2012 • Q. Wu, presentation, LARP CM 18/Hi. Lumi LHC Meeting, Fermi Lab, May 7 -9, 2012 • Q. Wu, S. Belomestnykh, I. Ben-Zvi, Novel deflecting cavity design for e. RHIC, Proceedings of SRF 11, Chicago, IL, July 25 -29, 2011 • R. Calaga, presentation, LHC-CC 11, CERN, Nov 14 -15, 2011 11/14/12 • I. Ben-Zvi, presentation, LHC-CC 10, CERN, Dec 15 -17, 2010 21