Influence of the ionization process on characteristics of spatial relaxation of the average electron energy in inert gases in a uniform electric field.

Theoretical studies of the characteristics of the spatial relaxation of the average energy of electrons in inert gases (He, Ne, Ar, Kr, Xe) in a uniform electric field had been carried out. Conditions were considered when spatial relaxation has the character of damped oscillations. The calculations were performed using the Monte Carlo technique both without and taking into account the secondary electrons that appeared due to the ionization of atoms by electron impact. It was shown that the inclusion of secondary electrons leads to a noticeable decrease in the spatial relaxation length even in the case when the contribution of the ionization process to the electron energy balance is relatively small. For these gases, the upper boundary of the the electric field strength was determined, where the spatial relaxation of the average energy has the character of damped oscillations.

Modification of the Coulomb Logarithm due to Electron-Neutral Collisions.

We demonstrate that in partially ionized plasmas, Coulomb scattering can be significantly perturbed by electron collisions with neutral gas particles, and that this effect can be incorporated in the Coulomb collision terms of the Boltzmann equation by a modification of the classical Coulomb logarithm. We show that Boltzmann transport calculations using this modified Coulomb logarithm are in excellent agreement, for a sensitive model problem and a wide range of conditions, with particle simulations describing the many-body Coulomb interactions from first principles.