Electro-mechanical interactions in superconducting spoke -loaded cavities

This dissertation reports an investigation of the mechanical and electromagnetic properties of a beta = 0.4 double-spoke-loaded and a beta = 0.5 triple-spoke-loaded superconducting cavity at Argonne National Laboratory. These cavities are of interest in new heavy-ion and proton linear accelerators. We present a powerful method for characterizing arbitrary time-dependent Lorentz force induced detuning of superconducting cavities; the convolution of the Lorentz transfer function and the cavity accelerating gradient. Using the beta = 0.5 triple-spoke-loaded superconducting cavity the Lorentz transfer function is shown to accurately predict the cavity response to RF field pulses. We present experimental data characterizing the microphonic-noise of the beta = 0.4 double-spoke-loaded superconducting cavity and the subsequent design and testing of the beta = 0.5 triple-spoke-loaded superconducting cavity. The beta = 0.5 triple-spoke-loaded superconducting cavity rms microphonic-noise is less than 0.5 Hz, an improvement by an order of magnitude over the beta = 0.4 double-spoke-loaded superconducting cavity. Finally, electromechanical frequency and phase control methods to compensate the microphonic-noise of superconducting spoke-loaded cavities are presented. The techniques and methods developed here advance characterization and tuning techniques which are beneficial for all superconducting cavities and enable the use of spoke-loaded cavities in future accelerators.