Non-adiabatic transition of beams in gyrotrons through various magnetic field profiles

Abstract

The achievement of efficiency enhancement in small-orbit gyrotrons by using depressed collector techniques requires precisely configured magnetic field profiles which present adiabatic as well as non-adiabatic transitions to the spent beam. The effect of adiabatic changes can be evaluated analytically. That of complex non-adiabatic transitions, however, must be studied by numerical simulation of the particle trajectories. A single-particle code has been used to study a variety of profiles such as steps, troughs, and peaks. Results are presented showing the influence of the parameters of the field profile on the ratio of perpendicular to parallel components of velocity. Beam heating effects are also considered and examples are given of how they can be minimized.