Ambipolar diffusion in strongly electronegative plasma

Abstract

This paper studies the ambipolar diffusion in an electronegative plasma containing electrons, a single species of negative ions and a single species of positive ions. We demonstrate that in a plasma with the concentration of negative ions more than 10 times exceeding that of electrons one has to take into account the mobility of negative and positive ions. We established that in a strongly electronegative plasma (when the ratio of the concentration of negative ions and that of electrons α = n−/ne ≫ 1 and μe ≪ α·μ−, where μe and μ− are the mobilities of electrons and negative ions) the diffusion ceases to be ambipolar, and the coefficients of ambipolar diffusion of the charged particles become approximately equal to their coefficients of free diffusion.