介质窗横向电磁场分布下的次级电子倍增效应

本文利用自编P3D3V PIC程序, 数值研究了BJ32矩波导传输TE₁₀模式高功率微波在介质窗内、 外表面引发的次级电子倍增过程, 给出了次级电子3维空间位置分布特征、介质窗表面法向静电场分布规律以及电子数密度分布特性. 模拟结果表明: 对于介质窗内侧, 微波强场区域率先进入次级电子倍增过程; 而对于介质窗外侧, 则是微波弱场区域优先进入次级电子倍增过程. 形成机理可以解释为: 微波坡印廷矢量方向与介质窗外表面法向相同而与内表面法向相反, 内侧漂移运动导致强场区域电子易于被推回表面, 有利于次级电子倍增优先形成; 外侧漂移运动导致强场区域电子易于被推离表面, 不利于次级电子倍增形成. 准3维模型相对1维模型: 介质窗内侧次级电子倍增过程中, 次级电子倍增进入饱和时间长、饱和次级电子数目少、平均电子能量高、 入射微波功率低、沉积功率低; 介质窗外侧次级电子倍增过程中, 次级电子倍增进入饱和时间短、饱和次级电子数目少、平均电子能量低、 入射微波功率低、沉积功率低. 沉积功率与入射微波功率比值与微波模式、强度及介质窗内外侧表面关系不大, 准3维和1维模型计算结果均在1%–2%左右水平. 关键词： 高功率微波 介质表面次级电子倍增 粒子模拟 横向电磁场分布

Effects of transverse electromagnetic field distribution in the multipactor discharge on dielectric window surface

By using a P3D3V PIC code programmed by the authors, the multipactor discharge effects on dielectric inner and outer surface under high-power microwave with TE₁₀ mode in the BJ32 rectangular waveguide are numerically studied. The electron spatial distribution, distribution of electric field in the normal direction of the dielectric surface, and electron density spatial distribution are presented. Numerical results could be concluded as follows. For inner surface, the multipacting first occurs in the area with large electric-field of microwave; for the outer surface, multipacting first occurs in the area with small electric-field of microwave. The above phenomena could be explained as follows. Poynting direction of microwave is the same as the outer surface normal direction and opposite to the inner surface normal direction. So the drift in the area with large electric-field of microwave causes electrons easy to move back to inner surface, and so electrons are easy to leave from outer surface. Compared with 1D3V model, in P3D3V model, we have for inner surface multipactor discharge with long oscillator forming time, small secondary electron number, high average electron energy, low incident power of microwave, and low level deposited power; for outer surface, we have multipactor discharge with short oscillator forming time, small secondary electron number, low average electron energy, low incident power of microwave, and low level deposited power. The deposited power is about 1%–2% of incident microwave power both in 1D3V and P3D3V models; while the ratio between deposited power and incident power of microwave has nothing to do with microwave parameters and inner or outer surface.
Keywords： high power microwave multipactor discharge on dielectric surface PIC simulation transverse distribution of electromagnetic field