Theory of gyrotwystrons with mixed transverse geometries of the various stages

Gyrotwystrons are gyrotron amplifiers with resonant cavities, field free drift regions, and a nonresonant output waveguide. They are expected to be more wideband than gyroklystrons, and more efficient than gyro-travelling wave tubes. A theory of gyrotwystrons has been developed which describes gyrotwystrons with cavities of different transverse geometry than the output waveguide. An analytical approach permits one to estimate in a simple manner the effect of mixed transverse geometry on the interaction between the electron beam and the microwave field. Numerical studies of an NRL gyrotwystron design show it possible to realize a rather high efficiency over a large bandwidth (e,g., 35% efficiency with a bandwidth of 6%)