Extending the calculation of electron velocity distribution functions for electrical discharges to large values of E/N

The popular two-moment expansion of the Boltzmann equation is developed for cases involving significant generation of electrons by ionization. In particular, this formulation enhances the determination of electron velocity distribution functions at high values of E/N where ionization becomes significant. The simple two-moment approach allows such calculations to be made with modest computing resources. Examples are given of two such calculations in an inert gas (argon), and the numerical approach for these is outlined. Comparison with published experiments is shown to be very good, in both the low-E/N and high-E/N regimes. In one example, comparison with published results from a very general numerical procedure is found to be excellent.