Evolution of the density profiles and flows of charged particles during the diffusive decay of an electronegative gas plasma

Different scenarios of the spatiotemporal evolution of the parameters of th e diffusive decay of a pulsed electronegative gas plasma in the absence of plasma chemical processes are studied. It is shown that nonlinear diffusion in a plasma with negative ions occurs in several stages. The rate of elect ron density decay increases with time and, in the beginning of the second s tage, almost all the electrons escape from the discharge volume. On the oth er hand, the ion density profile is smoothed out due to ion-ion ambipolar d iffusion and the flow of negative ions toward the wall is absent in the fir st stage of decay. In the second stage, the main diffusion mode is first es tablished and then the ion-ion (electronless) plasma decays exponentially w ith a characteristic time determined by ion-ion ambipolar diffusion. (C) 20 01 MAIK "Nauka/ Interperiodica".