An RF cavity for the B-factory

The authors describe the proposed design for the 476 MHz accelerating cavity for the Stanford linear Accelerator Center/Lawrence Berkeley Laboratory/Lawrence Livermore National Laboratory B-factory. Use of conventional construction in copper means that careful consideration has to be paid to the problem of cooling. The need for a high shunt impedance for the accelerating mode dictated the use of a reentrant shape. This maximized the impedance of the fundamental mode with respect to the troublesome longitudinal and deflecting higher order modes, when compared to open or bell-shaped designs. A specialized damping scheme was employed to reduce the higher-order mode impedances while sacrificing as little of the fundamental mode power as possible. This was required to suppress the growth of coupled bunch beam instabilities and minimize the workload of the feedback system needed to control them. A window design capable of handling the high power was also required. >