Modeling of nonlocal slow-electron kinetics in a low-pressure negative-glow plasma

The kinetics of slow electrons is studied in a low-pressure negative-glow p lasma (NGP). A method based on the nonlocal approach is proposed, which all ows the nonlocal (nonequilibrium) nature of slow electrons to be accounted for in a physically transparent and numerically efficient manner. The slow electrons are divided into trapped (cold, Maxwellian) and free (supertherma l, non-Maxwellian). It is shown that the superthermal (free) electrons are particularly important because they carry current and supply energy to the system of cold (trapped) electrons. A nonlocal energy-balance equation for the trapped electrons is derived, in which heating by superthermal electron s and diffusion cooling are found to be among the most important mechanisms . Simple expressions for the diffusion-cooling rate and the wall potential are determined. The proposed method is validated by the numerical solution of the full kinetic equation for a NGP in Ar. The energy and space distribu tions of electron fluxes are analyzed, and flux reversal (in energy space) is observed and explained. A comparison to experiment is carried out and cl ose agreement is obtained. The proposed method can be useful in building fu lly kinetic, self-consistent models of various NGP-based discharge devices. (C) 1999 American Institute of Physics. [S1070-664X(99)01503-7].