The dominant role of oxygen concentration in He+O2 atmosp heric-pressure cold plasmas

Summary form only given. He+O₂ atmospheric-pressure cold plasmas have received much attention; mainly rely on the potential use of reactive oxygen species generated in such plasmas. In this paper we present the impact of oxygen concentration from 0ppm to 5% on the discharge modes, power dissipation, chemical composition and electrode fluxes of plasma species in He+O₂ atmospheric-pressure cold plasmas with a constant power density of 40W/cm³. It is found the discharge evolves from α mode to γ mode with the increase of oxygen concentration. The power coupled into electrons dominates in plasma bulk for all oxygen concentration, while the power coupled into ions dominates in the sheath below 10000ppm and in plasma bulk above 10000ppm. The power coupled into electrons dominates over the power coupled into ions below 20000ppm, as is opposite above 20000ppm. O^- is the dominant anion below 3000ppm and replaced by O₃^- at higher oxygen concentration, while O^- is always dominant in the electrode fluxes of anions for all oxygen concentration. O₂⁺ is dominant in the densities and electrode fluxes of cations below 10000ppm and replaced by O₄⁺ at higher oxygen concentration.