均匀场中负流注放电形成过程粒子模拟

Particle-in-cell Simulation of Propagation Process of Negative Streamer Discharge in Uniform Field

为研究均匀场中负流注放电的形成过程,采用粒子模拟方法对平行平板间隙中均匀场作用下高电压流注放电通道的形成和发展进行模拟,获取流注形成发展过程的瞬态物理图像和流注通道中心场强的变化图像。模拟结果表明:电子崩向阳极发展过程中,头部呈辐射状发展,尾部细长,电子集中在电子崩头部,当电子崩转变为流注后,流注通道中形成非平衡等离子体,通道头部和尾部局部场强增大,流注头部存在高能电子;在流注通道内的电子数密度分布图中观察到流注通道存在明显的分叉现象,不同气压和场强下通道分叉现象存在差异;场强一定时,流注发展速度受气压影响较小;气压一定时,随着场强增大,高能电子出现时间缩短,流注发展速度明显提高,通道中电子数密度显著增大,电离程度加深。

To study the propagation of negative streamer, we numerically simulated negative streamer channels in a uni-form field between parallel-plate electrodes using the particle-in-cell （PIC） method. Photos of transient steamerpropagation and electric field intensity at the center of streamer channel are obtained. The simulation results indicate thatavalanche spreads to anode with a radial head and a slender tail, while electrons gather in the head. After the avalanchetransforms into streamer, non-equilibrium plasma forms in the streamer channels, local electric fields in the head and tailincrease, and there are high-energy electrons in the head. Furcation of streamer channels is shown clearly in the picturesof electrons density distribution. There are differences in the bifurcation phenomenon between different pressures andelectric field intensities. Propagation speed of streamer hardly changes with pressure under the same electric field intensi-ty. However, it increases significantly with electric field intensity under the same pressure, in the meantime high-energyelectrons appear earlier, electron density in the channel increases obviously, and the degree of ionization increases.