Double Quarter Wave Crab Cavity Qiong Wu On behalf of the DQWCC team 12/13/2012 12/13/12

Outline Current Design Cavity parameters Higher Order Mode (HOM) damping Fabrication Status Stiffening and Helium Vessel Future plan Summary 12/13/12

The Double Quarter Wave Cavity Crabbing (fundamental) mode freq. 1st HOM Cavity length Cavity width Beam pipe diameter Deflecting voltage Unit MHz mm MV DQW crab cavity 400 579 390 148 84 3 12/13/12

Cavity Dimensions 390 337 296 291 362 unit: mm 12/13/12 Fabrication of prototype cavity is underway. Cavity is made out of only sheet material 291 unit: mm 12/13/12

Electric field (left) and magnetic field (right) of fundamental mode. Cavity Field Electric field (left) and magnetic field (right) of fundamental mode. 12/13/12

Cavity Parameters Unit DQWCC Fundamental Mode Frequency MHz 400 Nearest Mode Frequency 579 Vertical Deflection Voltage MV 3 Rt/Q (Fund. Mode) Ohm Epeak MV/m 44** Bpeak mT 60** Energy Content J 12 ** Might have some decrease in electric field on the cavity and increase of magnetic field at the port opening (ACE3P) 12/13/12

HOMs HOM Damping Electric field deflection mode horizontal mode longitudinal mode 12/13/12

HOM Couplers Scheme: I II III Loop size: 20 mm × 15 mm 12/13/12

HOM Damping HOM frequency [GHz] Mode Config. R/Q [Ω] Qext-I Qext-II Qext-III 0.579 Longitudinal 108 864 1360 1770 0.671 Horizontal 70.5 1526 3080 3260 0.700 Hybrid (y, z) 0.24/0.25 929 1310 2210 0.752 Deflection 34.9 1418 2020 3350 0.800 6.02e-4 2074 4120 4630 0.917 30.9 1345 2660 1.88e8 0.949 28.1 3183 3360 2220 1.080 1.54 1071 1350 1920 1.102 1.84e-3 902 1490 2350 1.114 1.06 2663 5040 2630 1.202 5.07e-2 5021 11000 8980 1.247 8.0e-2/6.0e-2 1373 1970 2920 1.291 10.0 778 1060 1450 12/13/12

Cavity with HOM high-pass filter 66 mm Z. Li @ 2nd Joint HiLumi LHC-LARP Annual Meeting Modified from BNL HOM filter for 56 MHz SRF Quarter Wave Cavity 12/13/12

Fabrication of the Prototype Courtesy of Niowave Inc. 12/13/12

Design of prototype stiffening Stiffening material: Ti Nb to Ti transition by serrated surface plus SS bolts SS bolts and pins at frame connections 12/13/12

Helium Vessel Design Preliminary design of the helium vessel The vessel will play a role in stiffening/tuning the cavity Clearance for other beam lines in the vicinity. Compact design which saves LHe Stress relief connections to the coupling ports(not shown here) 12/13/12

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 in January 2013. 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. The testing will be focused on Deflection voltage HOMs Peak fields Possible multipacting 12/13/12

Prototype fabrication and testing Fabrication and testing of the cavity and its various RF couplers (FPC, pick-up, HOM) will include: Cavity fabrication HOM coupler (two units) Fundamental Power Coupler and pickup Chemistry and HPR Vertical testing (2 rounds) 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) Collaborations: Rama Calaga (CERN), Luis Alberty (CERN), Zenghai Li (SLAC), Niowave Inc. 12/13/12

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 January 2013, and pre-testing treatments will start right after. Large separation between fundamental deflection mode and 1st 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. We are looking forward to testing the prototype Nb cavity in the year of 2013. 12/13/12

Reference Q. Wu, presentation, Double Quarter Wave Crab Cavity, 2nd Joint HiLumi LHC-LARP Annual Meeting, Frascati, Italy, Nov 14-16, 2012 Q. Wu, et. al., HOM Damping and Multipacting Analysis of the Quarter-wave Crab Cavity, Proceedings of IPAC12, New Orleans, LA, May 20-25, 2012 R. Calaga, et. al., A Quarter Wave Design for Crab Crossing in the LHC, Proceedings of IPAC12, New Orleans, LA, May 20-25, 2012 Q. Wu, presentation, LARP CM18/HiLumi LHC Meeting, Fermi Lab, May 7-9, 2012 Q. Wu, S. Belomestnykh, I. Ben-Zvi, Novel deflecting cavity design for eRHIC, Proceedings of SRF11, Chicago, IL, July 25-29, 2011 R. Calaga, presentation, LHC-CC11, CERN, Nov 14-15, 2011 I. Ben-Zvi, presentation, LHC-CC10, CERN, Dec 15-17, 2010 12/13/12