The effect of electron detachment on the diffusive decay of a low-pressure electronegative plasma

Abstract

There are two possible scenarios in the diffusion decay of a low-pressure electronegative plasma in a system featuring the electron detachment effect. In the case of a weak detachment, the system exhibits an initial sharp drop in the electron concentration followed by the ion-ion plasma formation. A small admixture of electrons appearing as a result of the detachment keeps all negative ions within the volume. In this stage, the densities of all charged plasma components decay according to the same exponential law with a characteristic detachment time. In the limit of a strong detachment, a principally different plasma decay regime takes place. In this limiting case, a usual (free of negative ions) rather than ion-ion plasma is formed in the second stage. This can be accompanied by paradoxical phenomena such as the growth of electron density with time, build-up of the near-wall potential jump, and a considerable decrease (up to complete vanishing) of the diffusion electron cooling usually dominating in the electron gas energy balance.