The Role of Metastable Species for High Pressure Glow Discharge Formation

对介质阻挡放电（DBD）中的亚稳组分在高压辉光放电中的作用进行了实验和理论研究，实验中对不同条件下DBD中Ar基高压气体中Ar（1 s5）进行了电学特性测量、放电结构观察、光学发射光谱和激光吸收光谱测量。研究了在Ar中加入少量电离势低于Ar（1 S5）激发势的C_2H_4时，Penning效应对高压辉光放电形成的影响。另外，将辉光放电用于废水处理，在与实验相同的条件下，采用流体模型对Ar/C_2H_4混合气体进行了数值模拟，研究了Penning电离对辉光放电的影响。本文还研究了微等离子体（直流微等离子体、共面电极介质阻挡放电微等离子体）中分步电离的贡献以及微等离子体的形成过程。此外，我们还验证了种子电子的电子雪崩是如何发展成辉光放电的，主要结论如下：1）为了形成稳定的大气压辉光放电，在低E/N区，通过Penning电离来提高有效电离系数是非常重要的。Ar与C_2H_4、C_2F_4和SiH_4的混合气体有望形成大气压辉光放电，用于真实的等离子体加工。2）大气压微等离子体中，正柱中的潘宁电离非常有效。气体加热和离子拖曳力导致强烈的气体流动。3）种子电子产生的电子雪崩导致的气体放电的径向膨胀需要电子或亚稳态物质的充分扩散。

The role of the metastable species for high pressure glow discharge formation in dielectric barrier discharge (DBD) geometry has been investigated experimentally and theoretically.In the experiment, we carried out the electrical characteristics measurement, discharge configuration observation, optical emission spectroscopy and laser absorption spectroscopy for Ar(1s_5) measurement in high pressure Ar-based gas in DBD at various condition. Influence of Penning effect on high pressure glow discharge formation is studied in Ar with adding a small amount of C_2H_4, which has lower ionization potential than excitation potential of Ar(1S_5). In addition, the glow discharge was used for wastewater treatment.In the numerical simulation using fluid model, the influence of Penning ionization was investigated in Ar/C_2H_4 mixtures under the same condition as the experiment. The contribution of stepwise ionization in microplasma (dc microplasma, DBD microplasma with coplanar electrode) was also investigated as well as the microplasma formation processes. In addition, we have verified how the electron avalanche from a seed electron develops into glow discharge.The main conclusion is as follows.1) For stable atmospheric pressure glow discharge formation without streamers, it is important to enhance the effective ionization coefficient at low E/N region by means of Penning ionization. Ar mixtures with C_2H_4, C_2F_4 and SiH_4 are expected to form atmospheric pressure glow discharge for real plasma processing.2) Penning ionization works very effectively in positive column in atmospheric pressure microplasmas. Gas heating and ion drag force causes the strong gas flow.3) The radial expansion of the gas discharge from a seed electron originated electron avalanche requires the sufficient diffusion of electron or metastable species.