Modeling the chemical kinetics of high-pressure glow discharges in mixtures of helium with real air

Atmospheric and near-atmospheric pressure glow discharges generated in both pure helium and helium-air mixtures have been studied using a plasma chemistry code originally developed for simulations of electron-beam-produced air plasmas. Comparisons are made with experimental data obtained from high-p...

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Veröffentlicht in:Journal of applied physics 2006-05, Vol.99 (9)
Hauptverfasser: Stalder, K. R., Vidmar, R. J., Nersisyan, G., Graham, W. G.
Format: Artikel
Sprache:eng
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Zusammenfassung:Atmospheric and near-atmospheric pressure glow discharges generated in both pure helium and helium-air mixtures have been studied using a plasma chemistry code originally developed for simulations of electron-beam-produced air plasmas. Comparisons are made with experimental data obtained from high-pressure glow discharges in helium-air mixtures developed by applying sinusoidal voltage wave forms between two parallel planar metallic electrodes covered by glass plates, with frequencies ranging from 10to50kHz and electric field strengths up to 5kV∕cm. The code simulates the plasma chemistry following periodic pulsations of ionization in prescribed E∕N environments. Many of the rate constants depend on gas temperature, electron temperature, and E∕N. In helium plasmas with small amounts (∼850ppm) of air added, rapid conversion of atomic helium ions to molecular helium ions dominate the positive ion kinetics and these species are strongly modulated while the radical species are not. The charged and neutral species concentrations at atmospheric pressure with air impurity levels up to 10000ppm are predicted. The negative ion densities are very small but increase as the air impurity level is raised, which indicates that in helium-based systems operated in open air the concentration of negative ions would be significant. If water vapor at typical humidity levels is present as one of the impurities, hydrated cluster ions eventually comprise a significant fraction of the charged species.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.2193170