Compact Crab Cavity Status E. Jensen for WP4 R. Appleby, T. Baer, J. Barranco, I. Ben-Zvi, G. Burt, R. Calaga, E. Ciapala, S. Da Silva, J. Delayen, L. Ficcadenti, R. De Maria, B. Hall, Z. Li, A. Grudiev, R. Rimmer, J. Tckmantel, J. Wenninger and many more (excuses) Crab Cavities context Many bunches require non-zero crossing angle to avoid parasitic collisions and to reduce beam-beam effects; Many bunches require non-zero crossing angle to avoid parasitic collisions and to reduce beam-beam effects; With non-zero crossing angle, luminosity gain by squeezing beams further is small (red curve below). With non-zero crossing angle, luminosity gain by squeezing beams further is small (red curve below). Crab cavities can compensate for this geometric effect and thus allow for a luminosity increase of about 50 % at * of 25 cm. Crab cavities can compensate for this geometric effect and thus allow for a luminosity increase of about 50 % at * of 25 cm. In addition, crab cavities provide an ideal knob for luminosity levelling; In addition, crab cavities provide an ideal knob for luminosity levelling; This allows optimizing for integrated rather than peak luminosity! This allows optimizing for integrated rather than peak luminosity! Local vs. Global Scheme Local Scheme: Local Scheme: Global Scheme: Global Scheme: Advantages: Only one cavity per beam; Larger beam separation near IP4; Elliptical cavity of known technology. Disadvantages: Constraining betatron phase advance; Requires larger collimator settings; Works only for H or V crossing; Only 800 MHz or higher fits. Advantages: Individual luminosity control at each IP; Adapted to H or V crossing; Orbit perturbed only locally; Could work lower f better performance. Disadvantages/concerns: Requires novel Compact Cavities (194 mm separation), well advancing, but not yet validated; Requires 4 cavities per IP; What if 1 cavity trips? Compact Crab Cavities are in need! The nominal LHC beam separation in the LHC is 194 mm; Conventional (elliptical) cavities scale with they are too large even at 800 MHz! The nominal LHC beam separation in the LHC is 194 mm; Conventional (elliptical) cavities scale with they are too large even at 800 MHz! but at higher f, the RF curvature is non-linear! but at higher f, the RF curvature is non-linear! This is a real challenge! This is a real challenge! Progress with Compact Crab Cavities They appeared in LHC-CC08 (in the box Exotic Designs); seriously considered from They appeared in LHC-CC08 (in the box Exotic Designs); seriously considered from They made remarkable progress since then. They made remarkable progress since then. Truly global effort: Truly global effort: FNAL, SLAC, BNL, KEK, LBNL, ODU/JLAB, ULANC & CERN Truly global design effort R. Calaga, SRF2011 SLAC (&ODU/JLAB) : Double-ridged cavity Double ridge cavity now teamed up with ODU/JLAB. Excellent! Double ridge cavity now teamed up with ODU/JLAB. Excellent! Field flatness < 10 mm Field flatness < 10 mm first OOM far away, HOM damping relatively simple (below cut-off) first OOM far away, HOM damping relatively simple (below cut-off) HOM below (stringent) impedance budget. HOM below (stringent) impedance budget. LHC-CC11, CERN, 15 Nov 2011 Zenghai Li ODU/JLAB (&SLAC) : Parallel bar to double ridged waveguide evolution J. Delayen, S. da Silva Progress with ODU/JLAB/SLAC design Flattening field profile OK: Flattening field profile OK: MP: cavity quite clean; issue maybe in the couplers under study! MP: cavity quite clean; issue maybe in the couplers under study! Engineering design has started: sensitivity to pressure variation done. Engineering design has started: sensitivity to pressure variation done. Prototype square outer conductor; size 295 mm Prototype square outer conductor; size 295 mm 3 MV, marginal for 5 MV 3 MV, marginal for 5 MV First CU, then Nb prototypes: First CU, then Nb prototypes: LHC-CC11, CERN, 15 Nov 2011 Prototype status BNL: wave cavity Compact and simple, mechanically stable. Compact and simple, mechanically stable. Synergy with eRHIC (181 MHz) Synergy with eRHIC (181 MHz) Large separation to next HOM (theor. factor 3, realistically 1.4, high-pass filter enough!) Large separation to next HOM (theor. factor 3, realistically 1.4, high-pass filter enough!) Non-zero longitudinal field issue? Non-zero longitudinal field issue? Easy tuning. Easy tuning. Field flattening OK (