Simulation of atmospheric pressure non-thermal plasma discharges for surface decontamination applications

Abstract

Numerical simulations are conducted to characterize atmospheric pressure plasma discharges for surface decontamination applications. A self consistent two-dimensional hybrid model is developed to simulate the atmospheric pressure radio frequency (RF) plasma discharges in helium-oxygen mixtures. Numerical simulations are carried out for the plasma generated between an annulus electrode configuration with gas flow in between the electrodes and a surface to be decontaminated in front of the plasma afterglow. Basic plasma properties such as electron number density, radical, ion and excited species number densities, gas temperature, electric field and electron temperature are studied. The simulations indicated the discharge to operate in the α mode at low power. In the α mode the discharge was found to be uniform and volume dominated. At high power the discharge was found to transition to γ mode, with peak ionic species near the electrode surfaces. The discharge was also found to constrict in the axial direction. In both the modes He2*, O, O2 (1Δg) and O3 were the dominant species in the after glow of the discharge. O, O2 (1Δg) and O3 are key species for surface decontamination. Peak gas temperature predictions indicate the discharge to be a non-thermal non-equilibrium discharge. However the peak temperature of the discharge while in the γ mode was ∼150 K higher than that at the α mode. © 2008 Springer Science + Business Media B.V.