The Role of Metastable Species for High Pressure Glow Discharge Formation

点击翻译按钮获取中文摘要

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.