Development of crab cavity for CESR-B

In order to realize the crab crossing scheme desired for B-factories, we designed single cell superconducting crab cavities operating in TM110 mode. A coaxial beam pipe was attached to damp dangerous monopole and dipole parasitic modes. We designed two kinds of cell shape depending on the method to cure unwanted polarization of TM110 mode; one is a round cell which will be slightly polarized and the other is an extremely polarized (squashed) cell. We made one-third scale copper/aluminum model cavities to check damping property. Q values of all dangerous monopole and dipole modes are damped to less than the order of 100, as was expected by calculations. We also measured one-third scale niobium model cavity in liquid helium. Design goals of field and Q value to provide necessary kick voltage for CESR-B were achieved successfully. These results show that our design of the crab cavity is promising to realize the crab crossing