The influence of anisotropy and non-locality of the electron distribution function as well as non-equilibrium ion diffusion on the electrodynamics of CF4 DC discharge at low pressure

The influence of non-locality and anisotropy of the electron distribution function (EDF), as well as of the non-equilibrium ion diffusion, on the behaviour of the discharge in a strongly electronegative gas has been studied using as an example a CF4 DC glow discharge at low pressure. In order to take into account the spatial non-uniformity of the EDF, we used the spatially dependent mean electron energy (MEE) method and the particle-in-cell Monte Carte (PICMC) technique. The results of calculations were compared with the experimental values of the reduced electric field for the CF4 DC glow discharge. It has been shown that, for the case of low pressures (high reduced electric fields), the PICMC technique describes the discharge the most adequately. It has also been shown that the EDF is strongly anisotropic at low pressure, in which case the ionization process is supported by electrons moving in only one direction. The non-equilibrium ion diffusion (due to the ion-heating in the axial electric field) has been shown to bring about a significant modification of charged particle radial profiles. As a result, the region of quasi-neutral electron-ion plasma near the tube wall does not exist throughout the range of pressures studied (0.13-2.6 Torr).