Spatially dependent kinetics of electrons and excited atoms in the column plasma of a He-Xe dc discharge

The radially varying kinetics of electrons and excited atoms in the cylindrical axially homogeneous positive column of a dr glow discharge in a gas mixture of helium and 2% xenon was studied. The experimental investigations comprise the radially resolved measurements of the isotropic parr of the electron velocity distribution function (EVDF) using a single-probe technique and of the densities of atoms in the lower excited states by using a laser diode absorption method. The theoretical investigations are based on the solution of the space-dependent kinetic equation for the EVDF and the balance equations of excited gas atoms. Besides a strict solution, various simplified treatments of the electron kinetics as the conventional homogeneous approach and the nonlocal approach have been applied. The electron kinetic behavior in the helium-xenon column plasma changes remarkably with increasing helium gas pressure from a distinctly nonlocal behavior at a low pressure of 100 Pa to a nearly local behavior at a medium pressure of 600 Pa.