Influence of ion drag force on radial distribution of dust particles and void formation in a DC glow discharge

A model of the positive column of a DC glow discharge in argon with dust particles is presented. The model is based on the solution of the non-local Boltzmann equation for the electron energy distribution function (EEDF), the drift-diffusion equations for ions, and the Poisson equation for a self-consistent electric field. The radial distribution of dust particles density in a dust cloud is calculated according to an equilibrium Boltzmann distribution in the electrostatic field and under the action of the ion drag force. It is shown that if in the center of the discharge tube the ion drag force is larger than the electrostatic force, a dust-free region (void) in the central part of the dust cloud is formed. Otherwise (for a smaller ion drag force) the dust cloud is formed around the axis of the discharge tube without a void. In both cases, in the region of the dust cloud the ionization and recombination rates become almost equal to each other, and the radial component of the electric field is expelled from the dust cloud.