Radial macroscopic model of a plasma flowing along annular dielectric walls

Abstract

The classical model of the transverse interaction of a collisionless, partially ionized plasma with two insulator walls confining it, is here generalized to plasmas flowing parallel to the walls. A macroscopic formulation is proposed, where the contributions of the axial flow are included into the radial equations through source terms for particle production, ion friction, and ion heating. These contributions compete with those due to ionization, and add three new parameters to the classical model. Zero-ionization cases are presented to show that the net production (and loss) of plasma can be independent of ionization. Friction effects on the radial ion acceleration is found to reduce plasma fluxes into the walls. The ion temperature is determined from the competition between heating due to ionization and cooling due to radial rarefaction; isothermal and isentropic behaviors are recovered only for particular situations. Planar and annular geometries are studied. For the latter one, the differences in the inner and outer plasma fluxes are evaluated. The application of the model to the plasma discharge in an annular Hall thruster is commented.