Effects of oxygen concentration on streamer propagation and ozone production in a single-filament streamer discharge at atmospheric pressure

Limited research has been conducted on the formation mechanism of chemically active species in streamer discharges with respect to the oxygen concentration, which is critical to various applications such as ozone generation, air purification, and plasma-assisted combustion, among others. Herein, the oxygen concentration in an N-2/O-2 gas atmosphere is varied from 1% to 99% under atmospheric pressure and room temperature to investigate changes in the characteristics of streamer discharge propagation and generation of chemically active species. As the oxygen concentration increases from 10% to 90%, the decay rate of the discharge current, propagation velocity of the primary streamer, and ozone production efficiency increase. These phenomena are qualitatively explained by the electron attachment reaction to oxygen molecules and changes in the electron energy distribution function caused by the change in the oxygen concentration. However, the amount of discharge emission from N-2(C) cannot be explained by changes in the fraction of electron energy lost in excitation of N-2(C) and its quantum yield, implying that changes in the production of N-2(C) in the primary and secondary streamers must be considered in a spatiotemporal manner. This study demonstrates that the ozone and N-2(C) production characteristics in streamer discharges vary nonlinearly with respect to the oxygen concentration.