Development of Superconducting Spoke Cavities for High-Velocity Applications

Abstract

To date, superconducting spoke cavities have been designed, developed, and tested for particle velocities up to β0 ~ 0.6, but there is a growing interest in possible applications of spoke cavities for high-velocity applications. The first task is to explore the design parameter space for low-frequency, high-velocity, single- and double-spoke superconducting cavities in order to determine how each design parameter affects the electromagnetic properties, in particular the surface electromagnetic fields and the shunt impedance. Once an electromagnetically optimized, high-velocity spoke cavity is designed, there are several other characteristics that need to be investigated. These include multipacting scenarios, higher-order mode excitation and suppression, multipole analysis of the accelerating field, and mechanical properties. Finally, the cavity fabrication and testing is performed and evaluated. In this dissertation, we present a detailed account of the full development process for the first high-velocity single-spoke cavity operating at 325 MHz and double-spoke cavity operating at 500 MHz.