Formation mechanisms of the APTD mode in a N₂-N₂O DBD at atmospheric pressure

Dielectric barrier discharges (DBDs) at atmospheric pressure have raised significant interest for their potential in various applications, including surface treatment, decontamination and plasma medicine. It is well known that the used gas mixture largely influences the respective operation mode of DBDs, which is crucial for their practical use. This study explores the effects of N₂O admixture to N₂ on the discharge behavior of a sine-driven single-filament DBD. Electrical and optical diagnostics in combination with simulations reveal that the discharge operates in the atmospheric-pressure Townsend discharge (APTD) mode when small amounts of N₂O are added to the N₂ background gas. A time-dependent and spatially one-dimensional fluid model is applied to study in detail the reaction kinetic processes and transport effects leading to the formation of the APTD mode under the given conditions. It is shown that the presence of N₂O significantly influences the spatio-temporal discharge dynamics by enhancing the associative ionization process O + N(²P) → NO⁺ + e, which is pivotal in sustaining the APTD. Additionally, the dissociation of N₂O provides atomic oxygen and nitrogen, supporting this ionization mechanism up to a certain threshold of N₂O concentration.