PPPS-2013: Collisional-radiative modeling of free-burning arc plasma in argon

Summary form only given. Recent ambitions were aimed at improving a free-burning arc modeling by means of a self-consistent description of the arc plasma and the electrodes¹. As next step, a non-equilibrium model of the arc in argon describing the heat transfer, electric and magnetic field, and excitation kinetics of a large number of levels of argon atoms is presented. The extended scheme of levels allows obtaining the populations of individual levels giving rise to important radiative transitions and enables better comparison with spectroscopic measurements. The model is based on the magnetohydrodynamic approach and starts from macroscopic parameters only. The Navier-Stokes equations provide a solution for the total mass density and the mass-averaged velocity. Separate energy equations are solved for heavy particles and electrons. The current continuity, Ohm´s law and Maxwell´s equations are considered to obtain the electric potential and the self-induced magnetic field. The heat transport in the electrodes accounts for thermal conduction, Joule heating and energy fluxes on their boundaries with the plasma due to ion and electron heating, electron emission and black body radiation. The unified description of the plasma and the electrodes is realized by implementing a sheath model², in which the space charge sheath is treated as a zero-dimensional interface and the plasma characteristics of the presheath are obtained from the near-surface control volumes. The species transport is described by diffusion equations for excited atoms and ions. A set of reactions accounts for elastic scattering, excitation and de-excitation in collisions with electrons and atoms, step-wise ionization, recombination and spontaneous emission.