时变等离子体高功率微波频率上转换的粒子模拟

Particle-in-cell simulation for frequency up-conversion of high-power microwave in time-varying plasma

基于电磁波与时变介质相互作用能够实现电磁波频率上转换的原理,通过粒子模拟(PIC)方法对电磁波与时变等离子体薄层相互作用进行模拟,实现了频率由2.45GHz提升至130GHz,功率转化效率约为0.39%。探究了等离子体参数(包括等离子体密度、有限的等离子体上升时间以及等离子体薄层厚度)对频率上转换的影响。模拟结果验证了等离子体密度决定上转换频率,与理论结果相符。模拟结果表明,等离子体薄层厚度越大,得到的上转换波的能量越大;等离子体的上升时间越小,上转换波的转换效率和频谱纯度越高。采用等离子体密度2×10^(20)cm^(-3),等离子体厚度1cm,等离子体上升时间0.04ns可以得到可观的130GHz上转换波输出。

The frequency up-conversion of an electromagnetic wave in a time-varying plasma has been simulated in this paper with particle-in-cell （PIC） method, and it transformed a 2.45 GHz source radiation into a 130 GHz radiation with the power conversion efficiency of around 0.39%. We also studied the effects of the plasma parameters including the plasma density, the finite rise time of ionization and the width of plasma slab. It is concluded that the frequency up-conversion of the output wave was mainly affected by the plasma density, which was consistent with the theoretical results. In addition, the simulation showed that the energy of the output wave would be lager with the increase of the width of plasma slab, and the conversion efficiency of the output wave and spectrum were much better when the plasma rise time was shorter. A considerable 130 GHz radiation could be obtained with the plasma density of 2×10^20 cm^-3, the plasma thickness of 1 cm, and the plasma rise time of 0.04 ns.