Experimental and Theoretical Study of the Inhomogeneous Electron Kinetics in the dc Column Plasma

The radial change of the electron velocity distribution function and of related macroscopic quantities of the electrons are studied theoretically and experimentally in the positive column plasma of a neon dc low pressure glow discharge. The theoretical investigations are based on the solution of electron kinetic equations. The measurements of electron kinetic quantities are performed by using a single probe technique with automated recording. To avoid the strict treatment of the complicated radially varying electron kinetics in the microphysical description of the column plasma, various simplifications of the appropriate inhomogeneous kinetic equation have been adopted in the past. Recently a strict solution approach of this complex kinetic problem could be developed. Using this strict solution approach and experimentally determined electron kinetic quantities the approximation quality, obtained by applying various simplified approaches to treat the electron kinetics as the conventional homogeneous approach, the nonlocal approach and the local field approximation, is illustrated and critically evaluated in this paper.