Studies of electron transport and propagation of negative ionization fronts in C₂F₆ and its mixtures with N₂ and CO₂

A multi-term solution of the Boltzmann equation is used to calculate the transport coefficients of electron swarms under the influence of an electric field. The hierarchy resulting from a spherical harmonic decomposition of the Boltzmann equation in the hydrodynamic regime is solved numerically by representing the speed dependence of the phase-space distribution function in terms of an expansion in Sonine polynomials about a Maxwellian weighted function. Electron transport coefficients are calculated over a range of reduced electric fields with significant differences in behavior between the pure C₂F₆ and its mixtures with N₂ and CO₂ being found. Values of mean energy, ionization rate, drift velocity, and diffusion tensor are reported here. In order to simulate the propagation of negative ionization fronts, we employ the classical fluid model which combines the equation of continuity for electrons and ions as well as the drift-diffusion approximation for electrons, and Poisson’s equation for the calculation of the space charge electric field.