Influence of the nitrogen-helium mixture ratio on parameters of a self-sustained normal dc atmospheric pressure glow discharge

The influence of nitrogen additions to helium flow on the non-equilibrium plasma parameters and the discharge onset voltage of the self-sustained normal dc glow discharge at atmospheric pressure is studied. The concentrations of the low-excited helium atoms in states 21S, 21P, 23S and 23P are determined in glow discharge in helium (99.98%He) and in helium with a nitrogen admixture using the absorption spectroscopy technique. It is shown that the addition of a small amount of nitrogen into helium (less than 5%) leads to the increase of both interelectrode gap voltage and gas temperature. The drastic reduction of concentration of the low-excited helium atoms (n 2) in the cathode region even at a nitrogen admixture of 0.5% occurs due to their quenching by the nitrogen excited species. At the same time, concentrations of higher excited helium atoms (n = 3) are essentially unchanged