Nonlinear analysis of absolute instability in gyrotron traveling wave amplifiers

Abstract

This study analysis the absolute instability by using a nonlinear self-consistent simulation code. The code is based on the technique of steady-state particle tracing in a weakly nonuniform interaction structure and appropriated for output power of amplifier, start-oscillation currents of gyro-BWO and reflective oscillation. If the unstable band extends to the forward and backward wave regions, there will provide an internal feedback to result in the absolute instability.