空气中微波击穿电场的计算

Simulation of Microwave Breakdown Electric Field in Air

本文采用扩散控制的微波击穿模型,计算了低气压空气的微波击穿电场。为获得简单而直观的计算方法,利用了直流场中的气体放电基本参量,给出了微波击穿电场的计算过程。通过合理的数学处理,推导出计算微波击穿电场的简单公式。计算结果显示,微波击穿电场与气压的关系呈现出典型的帕邢曲线,即在某个气压时击穿电场最小。最低击穿电场及其对应的气压,也以简单公式的形式在文中给出。用简单公式计算出的击穿电场与文献的实验结果基本符合,表明简单公式是正确的。在此基础上,探讨了影响击穿电场的因素。结果表明,等效直流电场和电子平均温度均与微波频率无关,它们均是气压与特征扩散长度乘积的函数。微波击穿电场并不是气压与特征扩散长度乘积的函数,而是分别受气压、微波频率、特征扩散长度的影响。频率越高,击穿电场越大。特征扩散长度越大,击穿场强越小。

The breakdown of microwave electric field in low-pressure air was approximated, modeled and simulated. The simple expression of the breakdown field was derived with the diffusion-eontmUed model in terms of DC discharge of gases. The impacts of the discharge conditions, including the pressure, average electron temperature, and microwave fre- quency, on the breakdown field were calculated. The simulated results show that the dependence of the breakdown field on the pressure closely resembles typical Paschen curve. The results calculated with the newly-derived formula were found to agree very well with the measured data reported in the literature. Moreover, we found that the microwave frequency little affects the effective DC field and average electron temperature, and that the breakdown field significantly depends on the pressure, microwave frequency, and characteristic diffusion length. A stronger breakdown field results from a higher fre- quency, and a weaker field originates from a shorter characteristic diffusion length.