About the possible source of seed electrons initiating the very first breakdown in a DBD operating with the air at atmospheric pressure

Abstract

The conditions of the very first breakdown happening in a periodical dielectric barrier discharge (DBD) are not the same as those in the discharge established regime. The main intriguing problem in the very first breakdown is the source of the initial seed electrons. In this work, the role of atmospheric small negative ions in the appearance of seed electrons is investigated. The very first breakdown was studied by using a pin-to-plane barrier corona and plane-to-plane DBD operated with ambient air. These discharges were driven by fast- and slow-growing applied voltage. The experimental data related to the very first breakdown are presented. A short summary sounds as follows. In the case of a barrier corona initiated by a fast-growing voltage, seed electrons can appear due to their detachment from background negative ions in the bulk. Under a slow-increasing voltage, background ions have the time to be fully adsorbed on the cathode and the anode long before breakdown occurs. In such a case, seed electrons can appear from negative ions desorbed from the cathode. This desorption is induced by a strong electric field in the gap. The latter mechanism can work in a plane-to-plane DBD driven by both fast- and slow-growing applied voltage. Based on numerical calculations, a qualitative explanation of the obtained results is given. The influence of UV irradiation on the very first breakdown was also studied.