Experimental determination of the first Townsend ionization coefficient in mixtures of Ar and N2

Abstract

Mixtures of Ar with N2 are relevant for many areas of plasma applications. In particular, modeling of atmospheric pressure plasma jets for biomedical applications requires precise knowledge of fundamental gas parameters such as the Townsend ionization coefficient α. This study determines α in mixtures of Ar with N2 in a dark non-self-sustaining Townsend discharge. The discharge current versus electrode spacing was measured in the absolute pressure range of 10–800 Torr and reduced electric field strength E/N range of 40–1000 Td. The density normalized ionization coefficient α/N increases with E/N and decreased with N2 content in the gas mixture. A good coincidence between measurements and calculations with Bolsig+ was observed. In case when N2 concentration was between 10% and 50% in the mixture, experimental results were 20%–30% lower than predicted by Bolsig+ calculations. The results of this work were compared with α/N determined in mixtures of He with up to 10% of N2