Electron and ion fluxes to a dust grain in atmospheric pressure plasma

Approximate expressions for the electron and ion fluxes to a dust grain under conditions a ≪ l ≪ λ ( a is the grain radius, l is the mean free path of electrons or ions and λ is the screening length) are presented. Such conditions can be realized, for example, in a plasma at atmospheric pressure and temperature T ∼ 0.1 eV for grains of (sub)micron size. In two limit cases l ≪ a , λ and l ≫ a , λ, the expressions for the fluxes are well known. In the intermediate case, the motion of an electron or ion in the spherical layer a < r < a + l is considered as collisionless in the Coulomb potential, while for r > a + l the drift-diffusion approximation is used. The obtained expression for the electron flux is applied for setting the boundary condition near the dust grain in the case of a thermionic plasma.