Frequency Range for Stable Generation of Atmospheric Glow Discharges in Helium and Nitrogen

Low-temperature atmospheric pressure glow discharges are now used in an increasing range of applications, from thin film deposition, through removal of gaseous pollutants, to surface sterilization. While their potentials are now widely recognized with a large body of application-oriented experimental studies in literature, the understanding of their behaviors remain largely sparse. For example, it is not clear how the dynamics of atmospheric glow discharges may be affected by the temporal characteristics of the excitation voltage. Equally importantly how this dependence may be used to derive better and more stable atmospheric gas discharges. We have previously shown that the production of excited species in atmospheric plasmas can be made more efficient by pulsing the sinusoidal excitation voltage than the usual case of sinusoidal excitation. In this contribution, we aim to study further effects of temporal characteristics of the excitation on atmospheric plasma dynamics. In particular we will establish the frequency range within which stable atmospheric glow discharges can be generated with sinusoidal excitation. We consider both helium discharge and nitrogen discharge, such that the difference of discharge dynamics in these two different gases is used to probe the physics that underscores their different frequency ranges. Using a theoretical model that has been validated with experiments, atmospheric helium discharges and atmospheric nitrogen discharges are studied in details. Through numerical examples, their respective frequency ranges for stable generation of atmospheric glow discharges are deduced. The difference in these frequency ranges is discussed from the standpoint of the difference in key ionization processes in these two difference carrier gases. These are also compared with experimental results.