The role of a dielectric barrier in single-filament discharge over a water surface

Abstract

A dielectric barrier discharge over distilled water was investigated by means of synchronized, fast electrical and optical diagnostics. For this purpose, a single, alumina-covered electrode was placed above a water surface and a grounded tungsten electrode underwater, while the gas gap was constantly flushed with synthetic air at atmospheric pressure. Discharge events occur at rising and falling slopes or at the plateaus of the applied high-voltage pulse. Due to the synchronized diagnostics, a direct comparison of electrical characteristics and optical features of individual discharge events was performed. In most cases, a single discharge channel develops between the tips of the dielectric and the Taylor cone. Surface discharge channels can also occur in the upper part of the electrodes, which can be explained by a water layer being formed on the dielectric and acting as a virtual electrode. The discharge morphology and dynamics were found to be independent of the voltage polarity, which contradicts to known experiments with bare metal pin electrodes instead of dielectric-covered ones.