Influence of reflections on mode competition in gyrotrons

A general theory is presented for studying the influence of reflections on mode competition in gyrotrons. Strong effect is found in the illustrative example: the coaxial cavity TE/sub 28,16/ gyrotron operating close to the optimal point in the general parameter spare. In some cases, the fixed-field approximation and the self-consistent approach lead to qualitatively different predictions, which emphasizes the need for self-consistent calculations in the final stage of design of a gyrotron.