Dynamics of plasma streamers in a helium surface micro-discharge array at atmospheric pressure

Abstract

Abstract The dynamic evolution of plasma optical emission from an array of surface micro-discharges has been investigated by optical emission imaging. The array was operated in helium at atmospheric pressure and driven at 2.0 W at a frequency of 30 kHz. The findings indicate that surface charges and external voltage have a significant contribution to the splitting of the plasma streamer, with luminous fronts moving at velocities of 8.3–22.4 km s−1. The split plasmas induce new discharge events within a single hexagonal cell. Furthemore, we present the case of two co- and counter-propagating streamers generated within one hexagon mesh element. Experimental evidence reveals that the co-propagating streamers merge and produce a new streamer front with enhanced intensity under the combined effects of electrostatic repulsion, gas dynamic interaction and a photolytic process. As the spacing between the counter-propagating streamers decreases, the streamers interact electrically, resulting in a modification of the shape of these streamers as well as a decrease in their velocities and emission intensities. The emergence of secondary streamers is also observed. This behavior is related to surface charges accumulated during a previous half cycle and their redistribution due to the turbulence fluctuations dominated by electrohydrodynamic force. From the propagation of an individual streamer, it is shown that surface charges accumulated in a previous negative half cycle can determine the plasma path to some extent. The ionization wave propagates over the rim electrode with a velocity of about 20 km s−1, resulting in a distinct discharge channel and a strong interaction between neighboring hexagonal units in an array. The ionization wave leads to the propagation of plasma across the dielectric surface of the array.