Controlling the frequency of periodic self-modulation in gyrotrons with external reflections

Abstract

We develop the theory of electron–wave interaction in gyrotrons with reflections of part of the radiation, focusing on the implementation of self-modulation generation regimes with controlled frequencies. The optimal conditions for the simultaneous excitation of neighboring axial modes of the electrodynamic system of a gyrotron with a reflecting diaphragm in the output waveguide path are found. When the gyrotron is powered by an electron beam under these conditions, periodic self-modulation regimes are realized with the distance between the main spectral components controlled by varying the distance to the reflector. The conclusions of the theory are confirmed by the results of direct particle-in-cells simulation.