Influence of a Nitrogen Admixture on the Value and Radial Profile of the Metastable Argon Atom Density in a DC Glow Discharge in Argon

• Published in: Plasma physics reports 2018-12, Vol.44 (12), p.1154-1163
• Main Authors: Grigorian, G. M., Dyatko, N. A., Kochetov, I. V.
• Format: Article
• Language: English
• Subjects: Admixtures; Argon; Atomic; Density; Electric field strength; Electric fields; Gas discharge tubes; Gas pressure; Glow discharges; Low-Temperature Plasma; Mathematical models; Molecular; Nitrogen; Optical and Plasma Physics; Physics; Physics and Astronomy; Plasma
• ISSN: 1063-780X; 1562-6938
• DOI: 10.1134/S1063780X18120036

Results of measurements of the value and radial profile of the density of Ar( 3 P 2 ) metastables in a dc discharge in pure argon and Ar + 0.1%N 2 and Ar + 1%N 2 mixtures are presented. The electric field strength in the positive column of the discharge was also measured. The experiments were performed in a 2‑cm-radius discharge tube at gas pressures of 1, 7, and 60 Torr and discharge currents in the range of 10–50 mA. It is found that, at a pressure of 60 Torr, a nitrogen admixture to argon leads to a significant decrease in the electric field strength in the diffuse discharge, while at P = 1 Torr, in contrast, the electric field increases substantially. The degree to which the nitrogen admixture affects the density of Ar( 3 P 2 ) atoms on the discharge tube axis also depends on the gas pressure. At a pressure of 60 Torr, the Ar( 3 P 2 ) density decreases substantially (by three orders of magnitude for the 1%N 2 admixture and 1.5 orders of magnitude for the 0.1%N 2 admixture), while at a pressure of 1 Torr, the Ar( 3 P 2 ) densities in pure argon and in Ar + N 2 mixtures differ less than twice. It is also shown that, at all gas pressures under study, a nitrogen admixture to argon leads to the broadening of the radial profile of the Ar( 3 P 2 ) density. The experiments were accompanied by numerical and theoretical studies. For pure argon, the calculations were performed in a one-dimensional (along the tube radius) discharge model, while for the Ar + 1%N 2 mixture, in a zero-dimensional model, which allows one to calculate the plasma parameters on the tube axis. The calculated results were used to qualitatively explain the experimentally observed effects.