微波管中离子张弛振荡的混沌现象

微波管中离子张弛振荡引起的噪声对其工作性能有很大影响，已成为微波管领域研究的焦点之一.用包络方程描述电子束特性，用离散的宏粒子模型描述离子特性，在此基础上编写了一维粒子模拟程序，对行波管与速调管模拟，得到张弛振荡的时间序列；将振荡看作是一个复杂非线性动力学系统的响应，分析了离子张弛振荡时间序列的功率谱、重构相图及Lyapunov指数，指出离子张弛振荡具有混沌性质，为研究离子张弛振荡的控制与带有离子振荡噪声信号的处理提供了参考. 关键词： 张弛振荡 粒子模拟 微波管 混沌

The chaotic character of ion relaxation oscillation in microwave tubes

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.