The chaotic character of ion relaxation oscillation in microwave tubes
微波管中离子张弛振荡的混沌现象

The noise caused by ion relaxation oscillation becomes a research focus in the field of microwave tubes recently because of the improvement of radars and communications requirements. In this paper, electron beam is described by beam envelope equation, and ions generated from ionization of the background gas in microwave tubes are treated as discrete macro-particles. One dimensional Particle-in-Cell(PIC) simulation code was developed, and time series of ion relaxation oscillation are obtained by using the presented method. The ion relaxation oscillation is treated as the response of a complex nonlinear dynamical system, and the time series is analyzed by the power spectrum; the phase diagram and Lyapunov exponent are restructured. From the analysis results we find that the ion relaxation oscillation has a chaotic character. The reason of chaos was attributed to the dissipative Structure of the system. This would be useful for depressing relaxation oscillation and processing signals with relaxation oscillation noise.