The effect of three different methods of adding O2 additive on O concentration of atmospheric pressure plasma jets (APPJs)

In order to maximize the O concentration generated by the atmospheric pressure plasma jets (APPJs), several different methods of adding O-2 additive to working gas have been proposed. However, it is not clear, which method is capable of generating the highest concentration of O atom. In this paper, the concentration of O atoms in an APPJs by adding O-2 to (1) the working gas, to (2) the downstream inside the tube, and (3) to the shielding gas is investigated by two-photon absorption laser-induced fluorescence spectrometry. The results clearly demonstrate that the highest O density is achieved when 1.5% of O-2 is added to the working gas rather than the other two methods. In other words, the most effective way to generate O atoms is by premixing O-2 with the working gas. Further investigation suggests that O atoms are mainly generated around the electrode region, where the electric field is highest. In addition, when O-2 is added to the working gas, if in the meantime extra O-2 is added to the downstream inside the tube, a significant decrease of O density is observed. Published by AIP Publishing.