Stability analysis of a gyrotron backward-wave oscillator with an external injection signal

Controlling the phase and frequency of a gyrotron backward-wave oscillator (gyro-BWO) by means of injection-locking techniques is of practical importance. Using a nonlinear self-consistent time-independent code, this paper analyzes the stability of a gyro-BWO with an external injection signal. To examine the stability of steady-state solutions, the perturbation of the phase difference between the oscillator and injected signal must decay in time. A nonlinear time-independent code is employed to study the properties of the injection-locking gyro-BWO, including the locking power, the phase difference between the oscillator and injected signal, and the locking bandwidth curve. The simulation results show that the dependence of the phase difference of stable solutions on the frequency is consistent with the theoretical prediction at the injection-locking regime. Furthermore, the simulated phase differences of all stable solutions correspond with restrictions between -90 degrees and 90 degrees. Comparing with the curve of the locking bandwidth obtained by Adler's equation, the simulated result is slightly asymmetrical due to the field concentration near beam entrance. Finally, an efficiency enhancement on the injection-locked gyro-BWO is found and will be discussed.