Design of a 325 MHz SC Spoke040 cavity at IHEP

A spoke cavity is a TEM-class superconducting resonator with particular advantages: compact structure and high shunt impedance. The 325 MHz beta=0.40 (beta=v/c, v is the velocity of particle and c is the velocity of light) single spoke cavity (Spoke040) is adopted for the Chinese ADS (Accelerator Driven Sub-critical System) project. The physics and mechanical design has been accomplished, and the fabrication of a prototype is currently in progress. In this paper, the optimization processes for the main radio frequency (RF) and mechanical parameters are analyzed in detail. Two kinds of cavity end-walls (flat and convex) are compared. The convex end-wall is preferred in order to improve mechanical performance of the cavity. Two prototypes of the Spoke040 cavity are in the machining stage, and should be finished in early 2014. Vertical testing is also under preparation.