Low loss parameter for new CESR electrostatic separators

The electrostatic separators in the e+e- storage ring CESR have been large contributors to the overall impedance. In addition, the RF fields generated by the beam passing through the separators have seriously degraded the high voltage performance. These problems are becoming more acute as the beam current and bunch current are increased to meet the luminosity goals. A new separator has been designed for which bench measurements on a full scale mockup indicate one can expect a loss parameter of only 0.123 V/pC - about one quarter the value for the existing separators. A factor of two reduction came from tapering the ends. The other factor of two came from the unique ground electrode structure, which serves to keep electromagnetic energy close to the beam. At the ends of the separator, the taper and ground electrode are blended together in an unusual surface