Efficient production and transport of OH radicals in spatial afterglow of atmospheric-pressure DC glow discharge using intersecting helium flows

Abstract

An efficient method for generating OH radicals in the spatial afterglow of atmospheric-pressure plasma was investigated. The method employed a DC glow discharge along two intersecting helium flows in air. Tiny helium flows were ejected from two metal nozzles with inner diameters of 0.5 mm, and they intersected at a distance of 3–5 mm from the nozzles. A stable glow discharge was formed along the intersecting helium flows by applying a DC high voltage between the two nozzles. It was shown by laser-induced fluorescence spectroscopy that an origin of OH radicals was water vapor admixed into the intersection point of the two helium flows from ambient air. OH radicals were transported from the intersection toward the spatial afterglow along the coalesced helium flow. This is a distinctive feature of the present plasma source, by which we can obtain the stream of OH radicals in the outside of the active plasma zone even though we employ the DC discharge. In addition, we observed the production of OH radicals in the spatial afterglow. We presume that the production process of OH radicals in the spatial afterglow is dissociative electron attachment to H2O2.