Single and mixed gas breakdown characteristics induced by high power microwave
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摘要: 综合考虑高功率微波对电子的加速过程以及电子与气体分子的碰撞过程，建立了单一气体与混合气体击穿过程的蒙特卡罗仿真模型，编写了三维蒙特卡罗仿真程序(3D-MCC)。针对单一气体Ar和N2以及混合气体N2/O2展开研究，仿真了气体雪崩击穿电子云形成过程，对比分析了不同气体电子能量分布函数随压强的变化规律。发现了Ar击穿特性受电子能量分布函数影响较大，而N2击穿特性受电子能量分布函数影响较小。通过分析平均电子能量以及电子密度随时间的变化过程，得到了Ar和N2击穿时间，并通过与流体模型计算得到的击穿时间比对分析验证了3D-MCC模型的正确性。在真空腔体内开展了S波段高功率微波大气击穿实验，测量得到了场强为6.38 kV/cm时不同压强下的大气击穿时间。通过在辐射源与真空腔体之间增加聚焦透镜，大大减小了壁效应的影响，并且采用模型仿真得到的大气击穿时间与实验结果吻合较好。Abstract: A Monte Carlo model is proposed to simulate the process of HPM single and mixed gas breakdowns, and a three-dimensional Monte Carlo code (3D-MCC) is compiled by analyzing the collision process between electrons and background gases. Aiming at Ar, N2 and N2/O2 mixture (air), the electron cloud formation process and the electron energy distribution function (EEDF) can be obtained by simulating the process of gas breakdown using 3D-MCC. The gas breakdown time, derived by analyzing the variation trend of the EEDF and the electron density along with time, has an intense dependence on the EEDF for Ar, but not for N2. The correctness of this model is verified by comparing with the fluid model. An experimental system allowing the air breakdown to be triggered in vacuum by a focused HPM is established. The air breakdown time is measured under different pressures at S-band when the electric field is 6.38 kV/cm. The simulation results are consistent with the experimental data.
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Key words:
- high power microwave /
- gas breakdown /
- Monte Carlo simulations /
- breakdown time
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