大气压脉冲微波Ar/N_(2)等离子体射流的时空特性研究

Study of spatiotemporal characteristics of atmospheric-pressure pulsed microwave Ar/N_(2)plasma jets

在空气环境中,很难形成特定形貌的微波等离子体射流.本文构建了双气体通道同轴谐振放电装置,在空气环境中产生了脉冲微波Ar/N_(2)双层等离子体射流.实验测量了Ar/N_(2)等离子体射流电离发展的时空演变过程:(1)使用高速相机测量等离子体射流形貌的瞬态变化,发现电离的初始阶段和结束阶段存在光辐射增强的放电影像;(2)使用瑞利散射装置测量等离子体射流的电子密度,发现电子密度值达到10^(21)m^(-3)数量级,且在脉冲微波的上升沿和下降沿各有一次电离波峰;(3)使用单色仪测量特定波长段光谱的瞬态变化,追踪N_(2)^(+)谱线从首次出现到稳定发展、直至最后衰减消失的过程.结合实验测量结果和电磁仿真分析,发现脉冲微波的上升沿和下降沿各有一次增强电离过程,揭示了脉冲微波Ar/N_(2)双层等离子体射流的特殊放电形貌是时空局域增强电离致使.

Generating a microwave plasma jet with a specific morphology is difficult in ambient air.In this study,a coaxial resonant discharge device with dual gas channels is constructed to generate an atmospheric-pressure pulsed microwave Ar/N_(2) double-layer plasma jet.In addition,the time-space evolution of the ionization process in the Ar/N_(2) plasma jet was studied.The following results were obtained:(1)A high-speed camera captured transient changes in the plasma jet morphology;enhanced optical radiations were observed during the initial and final stages of ionization.(2)A microwave Rayleigh scattering device characterized the spatiotemporal electron evolution process in the plasma jet;electron density values were observed to reach 10^(21)m^(-3) orders of magnitude,with an ionization wave peak on the rising and falling edges of the microwave pulse.(3)A monochromator measured dynamic changes in the transient spectra,tracking the evolution of N_(2)^(+)spectral lines from their initial appearance toward a steady development and final decay.Combining the results of experiments and electromagnetic simulations,it was observed that the rising and falling edges of the microwave pulse exhibited an enhanced ionization process,revealing that the spatiotemporal local enhanced ionization was responsible for the unique discharge morphology of the pulsed microwave Ar/N_(2) double-layer plasma jet.