The transition between different modes of barrier discharges at atmospheric pressure

Barrier discharges (BDs) can be operated in so-called diffuse modes. In contrast to the usual filamentary regime, which is characterized by a large number of individual microdischarges, the plasma of a diffuse BD covers the entire electrode area uniformly. Depending on the operation conditions (gas composition, amplitude and frequency of applied voltage), different diffuse modes can be investigated, namely, the atmospheric pressure Townsend discharge (APTD) and the atmospheric pressure glow discharge (APGD). The subject of the paper is the study of the transition between APTD and APGD as well as between diffuse and filamentary BD modes. Therefore, BDs were studied in the gas mixtures N2/H2, N2/He, N2/Ne and N2/Ar. It is shown that APGD in the noble gases helium and neon is formed due to high ionization rate at a comparatively low electric field, assisted by indirect ionization mechanisms involving metastable states of inert gases and nitrogen impurities, while the existence of APTD is coupled to the existence of metastable states of molecular nitrogen. Furthermore, a similar memory effect of residual surface charges on the dielectric barriers as described for filamentary BDs was observed in diffuse BDs.