The high power microwave window breakdown characteristics of N2–SF6 mixtures are investigated with 3D particle-in-cell and Monte Carlo collision simulation. The space and density distributions of electrons and ions are obtained. The results show that the threshold of breakdown increases with the ratio of SF6 when E/P is large. However, when E/P is small, the threshold of breakdown in 70% of SF6 and 30% of N2 is greater than that of pure SF6. This phenomenon is also observed in experiments. The theory analyses show that the energy loss of electrons is mainly caused by excitation collisions with N2 when the average energy of electrons Te is less than 6 eV and is dominated by excitation and ionization collisions with SF6 when Te is greater than 6 eV. When E/P is small, the proportion of low energy electrons is large and Te increases with the ratio of SF6. Therefore, the effective ionization rate first decreases and then increases as the ratio of SF6 increases. Thus, the optimal ratio for improving the insulation properties is 60%–80% SF6 when E/P is small. When E/P is large, the proportion of high energy electrons increases. Therefore, the effective ionization rate and density of electrons decrease as the ratio of SF6 increases. The maximum threshold of breakdown occurs when the ratio of SF6 is 100%.

中文翻译：

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微波窗口气/介质界面N2-SF6混合物击穿特性研究

N2-SF6 混合物的高功率微波窗口击穿特性通过 3D 细胞内粒子和蒙特卡罗碰撞模拟进行研究。获得电子和离子的空间和密度分布。结果表明，当E/P较大时，击穿阈值随着SF6比例的增加而增加。但是，当 E/P 较小时，70% SF6 和 30% N2 的击穿阈值大于纯 SF6 的击穿阈值。在实验中也观察到这种现象。理论分析表明，当电子平均能量Te小于6 eV时，电子的能量损失主要由与N2的激发碰撞引起，而当Te大于6eV时，则以与SF6的激发和电离碰撞为主。当 E/P 较小时，低能电子比例大，Te随着SF6比例的增加而增加。因此，有效电离率随着SF6比例的增加先降低后增加。因此，当 E/P 较小时，提高绝缘性能的最佳比例是 60%–80% SF6。当 E/P 大时，高能电子的比例增加。因此，有效电离率和电子密度随着 SF6 比例的增加而降低。SF6 的比例为 100% 时出现最大击穿阈值。随着SF6比例的增加，有效电离率和电子密度降低。SF6 的比例为 100% 时出现最大击穿阈值。随着SF6比例的增加，有效电离率和电子密度降低。SF6 的比例为 100% 时出现最大击穿阈值。