A collisional-radiative model applicable to argon discharges over a wide range of conditions. III. Application to atmospheric and subatmospheric pressure arcs

Abstract

For pt.II see ibid., vol.22, p.632 (1989). The extensive collisional-radiative model for an argon atom plasma is applied to atmospheric and subatmospheric pressure wall-stabilised arcs in order to clarify the mechanisms by which the excited levels are populated in the axial region of these discharges. Computations are carried out for various sets of input parameters, such as the electron kinetic temperature Te, the atom temperature Ta, the ion temperature Ti, the electron number density ne, the ground-state atom population n1, the plasma column radius R and the escape factors Lambda mn and Lambda m, characterising the non-equilibrium plasmas under consideration. The predicted values of the populations in the excited levels and the qualities derived from them, as well as the values of the critical electron densities for establishing the local thermodynamic equilibrium in the axial region of the arcs investigated, are in good agreement with the corresponding experimental results. The effect of the changes in the discharge parameters Te, Ta, ne, R and Lambda 1n on the population mechanism, together with the role played by the recombination flow of electrons from a continuum, the deviations of the actual electron distribution function from the corresponding Maxwellian form and by the atom-atom inelastic collisions, are also shown.