Electro-acoustic stability of a superconducting spoke cavity
This thesis describes measurement procedures and results for the measurement of the Q value and microphonics of a superconducting spoke cavity. The thesis starts by introducing the background of RF electronics and how they pertain to superconducting cavities. We then present the cavity model and figures of merit characterising its performance, the theory of how electric fields cause mechanical vibrations in the cavity walls and present an experimental setup for measurements. Four measurement procedures are presented, of which two are implemented. Measurements are carried out by running the cavity in a self-excited loop in an accurate manner with precise calibrations. Finally, we present the measured Q value of a single spoke cavity and the results of microphonics measurements. We find that the cavity has a Q value of 1.06'10^9 at a resonance frequency of 360.215MHz. It is sensitive to microphonics of a few frequencies, most notably some close to 14 Hz which coincides with the repetition rate of the ESS.
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