Spatiotemporal theory of a gyrotron based on a three-mirror cavity.

We present the quasi-analytical spatiotemporal theory of the resonant traveling-wave tube scheme of a gyrotron based on the transverse amplifications of the operating wave and on the use of a remote delayed feedback. The main idea is to implement a system with a dense spectrum of eigenmodes, which makes it possible to smoothly adjust the generation frequency by switching from mode to mode when the operating magnetic field changes. On the basis of a simple 2D three-mirror model, we show the possibility of achieving the stable single-frequency generation regime in this system if the excess of the operating current above the starting threshold is not too high. The mechanism of loss of stability of the single-frequency generation with an increase in operating current is also described. [ABSTRACT FROM AUTHOR]