Study of glow discharge positive column in air with dust structures

Complete text of publication follows. Experimental and numerical study of positive column of glow discharge with dust particles was motivated by the need to simulate plasma parameters and electric field configuration changes induced by cloud of particles. Dust structures of micron size particles were developed in the positive column of a glow discharge in air at pressure of 0.1 - 0.6 torr and discharge current of 0.1 - 3 mA. The numerical model of positive column with dust cloud with the specified geometric parameters, represented in, is developed. Plasma of positive column is described in terms of diffusion model and OML approximation is applied for description of dust particle charging. The numerical task was solved at discharge parameters where the most stable dust structures were observed. The radial distributions of plasma components reflect the change of electric field in presence of dust particles. When concentration of particles attains sufficient value, the efficiency of particle surface absorption becomes comparable with diffusive losses of electrons on walls of discharge tube leading to the situation when the electron concentration on outer face of dust cloud becomes even higher than in the center of discharge tube. At some critical concentration of dust particles, the radial electric field changes its direction towards the axis of the tube in certain region inside the dust cloud. Experimentally measured and simulated current-voltage characteristics of discharge with and without dust component show the increase of the positive column electric field strength in the presence of dust particles and the higher stability of discharge against disturbing action of dust particles at high currents.