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

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.

Automated summary

The study investigates the dynamic evolution of plasma optical emission from an array of surface micro-discharges, revealing the interaction between co- and counter-propagating streamers resulting in new streamer fronts with altered velocities and intensities. Additionally, the emergence of secondary streamers is attributed to surface charges accumulated during a prior half cycle and turbulence fluctuations dominated by electrohydrodynamic force.