Effects of external reflections on gyrotron backward wave oscillators

The gyrotron backward-wave oscillator (gyro-BWO) is sensitive to external reflections because it employs a non-resonant interaction structure. These reflections may result in serious output power variations and ragged frequency tuning. A numerical model is developed for the investigation of the reflection effects. It treats beam-wave interactions in the presence of external reflections. As a hybrid feature of the formalism, external reflections are self-consistently determined by the structures, rather than artificially set as a constant value as in previous models. The model has been employed to examine the effects of external reflections on the tunable bandwidth of the gyro-BWO, and showed the resonance in the external circuit is the major cause of the ragged frequency tuning.