Long Plasma Jet Generated by DC Discharge in N2 at Atmospheric Pressure: Impact of Trace Admixtures on Composition of Reactive Species in Far Afterglow

The object under study is a long plasma jet (up to 15 cm) generated by a steady-state dc discharge in N₂ at atmospheric pressure. Successful usage of long afterglow plasma jet for distant treatment of 3-D object of a complicated shape with deep slots was demonstrated. This paper focuses on a role of trace impurities in plasma-forming gas on chemical composition of reactive species in far afterglow plasma. This role was studied numerically by example of the additives in high-purity nitrogen contained in high-pressure N₂ tank. It is shown that small oxygen admixtures (at 10 ppm level) to N₂ can be more effective in production of atomic oxygen than ambient air. Besides, trace admixtures of water vapor and hydrocarbons (at parts per million level) lead to full change in a composition of reactive species in far afterglow in comparison with the set of primary species generated by plasma source.