Evaluation of transport coefficients in plasmas containing argon and sodium

Abstract

Results of a theoretical evaluation of number densities and transport coefficients for low-temperature (2000 K to 20 000 K) argon plasma containing up to 10% of added sodium are presented. It is taken that the plasma is kept under a constant pressure, equal to, or 5 to 25times higher than the normal atmospheric pressure. The plasma is treated as weakly non-ideal and having attained the LTE state. Use is made of a previously derived modified Debye radius with the cut-off at the Landau length rather than at the smallest ionic radii, which allowed to treat the plasmas investigated as weakly non-ideal. This new Debye radius significantly alters the evaluated equilibrium plasma composition and transport coefficients. For the sake of comparison, the analogous system of equations for pure argon was also solved, with the use of the same evaluation methodology. The results of the theoretical evaluation of the electrical conductivity for pure argon plasma are compared with the experimental measurements. The theoretical results are found to be in satisfactory agreement with the available experimental data. On the other hand, the addition of a small amount of sodium is shown to lead to a significant increase in the electron number densities, as well as in both electrical and thermal conductivities below 10 000 K.