Full-Wave Analysis of a Complex Gyrotron Cavity with Coupled Smooth-Walled and Corrugated Resonators

A full-wave analysis is used to investigate conversion of normal modes in a complex gyrotron cavity formed by coupled smooth-walled and corrugated cylindrical resonators. The analysis takes into consideration expansion of normal modes in terms of azimuthal harmonics. It is shown that the high-order azimuthal harmonics produce a minor effect on a pair of the second-harmonic operating modes of the complex cavity. The exception is a shift of the optimal corrugation depth, which provides the strongest coupling between the operating modes. It is found that the first-harmonic competing mode exhibits reduced purity and ohmic quality factor, which are caused by strong coupling between azimuthal harmonics due to the corrugations.