Pin-to-plane self-pulsing discharge in transversal airflow: interaction with a substrate of plasma filaments blown out from the discharge zone

Abstract

The pin-to-plane electrode system for the multi-sectioned discharge in the transversal airflow at atmospheric pressure has been developed. The airflow is directed perpendicularly to the electric current. As it was revealed, all sections of the multi-sectioned discharge operate identically and independently to each other. For this reason, the spatial-temporal behavior of the discharge excited only in a single section was investigated. The pin-to-plane discharge (PPD) was powered by a positive polarity DC voltage that induces the spontaneously repeating streamer-spark breakdowns in a discharge gap. Each breakdown forms the plasma filament (PF) which is being further blown out of the discharge zone and stretched by the airflow. The PF impacts a dielectric plate located in the path of the airflow at different distances away from the discharge zone. Two modes in the behavior of the blown-out PF have been revealed. When the plate is close to the discharge zone, the blown-out PF is tightly pressed by the flow to the plate. In this case, both the brightness and electric current of the PF are periodically pulsing with a high frequency up to the plasma filament breaking up due to its strong elongation by the flow. If the plate is far away, the quasistationary regime happens. During the PF elongation in this regime, plasma filament keeps both the brightness and current approximately changeless till the filament breaking up. At In this regime, the blown-out PF is being stretched in parallel to the surface without contacting it. The release of energy into the PF continues also in the course of its blowing out until its impinging the object located in the path of airflow. Due to that, the PPD pulsing mode generates a lot of reactive species inside the PF up to its impinging the object to be treated. This is a reason why the self-pulsing PPD can be highly effective for surface processing by non-thermal plasma.