Characterization of surrounding gas-fed atmospheric pressure plasma jet using a double coaxial glass tube

We report the characteristics of developed surrounding gas-fed plasma jet using a double coaxial glass tube. Two gas flows can introduce independently into the tube and the gas and plasma flows interact outside of the glass tube. With an outer nitrogen (N₂) and an inner argon (Ar) gas flows, the plasma jet can be extended up to 44 mm while with both pure N₂ and mixing gas of N₂ and Ar, a conventional single glass tube cannot extend the jet to such length. In the case of helium (He) as an inner gas flow with an outer N₂ gas flow, emission lines of nitric oxide, the first negative and second positive system bands of N₂ were observed, while only the second positive system band was observed in the case of Ar as the inner one. Considering the Penning effects of each excited state, the metastable state of He has a higher energy than that of Ar, resulting in energetic nitrogenous productions in the former case. The excited state in the core plasma is one of the important conditions to determine the characteristics of the APPJ produced with a double coaxial glass tube. (author)