Dynamic simulation of the ion sheath in the presence of fast monoenergetic electrons

Abstract

This paper contains interesting simulation results concerning the nonstationary potential distribution inside the sheath formed between a plasma and a biased electrode in the presence of a fast group of electrons. The influence of these fast monoenergetic electrons on the ion dynamics of a planar sheath is investigated assuming that the ion, electron, and fast electron components act as three coupled fluids. Under collision-free conditions and in the presence of a fast electron beam, the evolution of the potential and ion density distribution as a function of length is found. These profiles show that in the plasma with a group of fast monoenergetic electrons, a nonmonotonic distribution of the potential could be formed in front of the cathode in which its maximum is larger than the biased electrode potential with the passage of time. Results indicate that the formation of this maximum potential depends strongly on the ratio of the density of non-Maxwellian (fast) electrons to the density of the Maxwellian (plasma bulk) electrons.