Accelerating cavity development for the Cornell B-factory, CESR-B

To achieve luminosities of 30-100 times CESR, 1-2 A of current must be stored. A CESR B-factory parameter list calls for 50 MV for two rings, to be supplied by 16 cells operating at 10 MV/m gradient. With a new cell shape, the impedances of the dangerous higher order modes (HOM) are drastically reduced. All HOMs propagate out of the cavity via the beam pipe, which is specially shaped. This allows HOM power couplers to be placed completely outside the cryostat. A ferrite absorber on the beam pipe lowers all Qs to approximately 100, which is sufficient to avoid multibunch instabilities without feedback systems. A waveguide input coupler on the beam-pipe provides Qext as low as 5*10/sup 4/, with a C- slot shaped iris that has a negligible effect on the cavity loss parameter. >