Wall fluxes of reactive oxygen species of an rf atmospheric-pressure plasma and their dependence on sheath dynamics
journal contributionposted on 01.12.2014, 14:56 by Ding-Xin Liu, Aijun Yang, Xiao-Hua Wang, Ming-Zhe Rong, Felipe IzaFelipe Iza, Michael G. Kong
A radio-frequency (rf) atmospheric-pressure discharge in He–O2 mixture is studied using a fluid model for its wall fluxes and their dependence on electron and chemical kinetics in the sheath region. It is shown that ground-state O, O+2 and O− are the dominant wall fluxes of neutral species, cations and anions, respectively. Detailed analysis of particle transport shows that wall fluxes are supplied from a boundary layer of 3–300μm immediately next to an electrode, a fraction of the thickness of the sheath region. The width of the boundary layer mirrors the effective excursion distance during lifetime of plasma species, and is a result of much reduced length scale of particle transport at elevated gas pressures. As a result, plasma species supplying their wall fluxes are produced locally within the boundary layer and the chemical composition of the overall wall flux depends critically on spatio-temporal characteristics of electron temperature and density within the sheath. Wall fluxes of cations and ions are found to consist of a train of nanosecond pulses, whereas wall fluxes of neutral species are largely time-invariant.
This work was supported by the State Key Laboratory of Electrical Insulation and Power Equipment (No EIPE11108), the Fundamental Research Funds for the Central Universities of China, and the English Department of Health.
- Mechanical, Electrical and Manufacturing Engineering