Self-Consistent Model of Kinetic Striations in Noble Gases

Plasma stratification remains a subject of considerable scientific and technological interest. We have developed self-consistent model of kinetic striations in noble gases using kinetic equation for electrons coupled to Poisson equation for the electric field and a drift-diffusion model for ions. The kinetic equation for the electron energy distribution function (EEDF) with kinetic energy u as independent variable has the form of a diffusion equation in (r,u) phase space with a tensor diffusion coefficient. Physically, it means that the elections diffuse along surfaces of constant total energy (kinetic plus potential) before they lose large quanta of the kinetic energy in inelastic collisions with atoms. Using kinetic energy as independent variable simplifies coupling of the nonlocal kinetic solver for electrons with other plasma equations. Such a hybrid model was implemented in both COMSOL software and in open-source basilisk framework for 1d1u phase space. We will demonstrate the formation of standing striations in Townsend discharges under DC and RF conditions, moving striations in DC discharges, and standing striations in Capacitively Coupled Plasmas. Comparison of simulation results with experimental observations will be discussed.