Measurements of single-filament pulsed positive streamer discharge and two-dimensional ozone density distribution in atmospheric-pressure nitrogen-oxygen mixture ― effects of oxygen concentration *

Streamer discharge is widely used in applications. Fundamental researches on streamer have been conducted using experiments and simulations, but the simulation is usually axisymmetric two-dimensional (2D), which cannot be compared with experimental results because of the branching and non-axisymmetric characteristics of streamer discharge. Recently, we have succeeded in generating a pin-to-plane single-filament pulsed positive streamer discharge that can be compared with 2D simulation. In the current work, the effect of oxygen concentration on the single-filament steamer in atmospheric-pressure N₂/O₂ mixture is investigated. The gap distance is 13 mm and the applied voltage pulse is 30 kV with 200 ns duration. The results show that, when the O₂ concentration increases from 10% to 90%, the diameter and propagation velocity of streamer are almost constant irrespective of O₂ concentrations, whereas the optical emission intensity decreases as O₂ concentration increases. Next, 2D ozone density distribution produced in the streamer is measured using 2D photofragmentation laser-induced fluorescence. The results show that the total amount of O₃ yield reaches the maximum when the O₂ concentration is 40%. The measured results will be used for verifying our 2D simulation in future work.