An experimental and theoretical investigation of the dynamics of a flowing afterglow plasma

A study of plasma and neutral gas flow dynamics has been carried out in pure helium flowing afterglow. The measured plasma flow velocity nu p is observed in effect to be radially independent, in contrast to the instantaneous neutral gas flow velocity profile nu g (r) which is approximately parabolic with some slip at the walls. This observation has led to a new and simplified approach to the flow dynamics based on the concept of a radially independent plasma flow velocity from which, in conjunction with the instantaneous charged particle velocity radial profile (assumed to be equal to nu g (r) and a fundamental mode Bessel radial distribution of charged particle (plasma) density, an averaged plasma flow velocity nu p has been calculated which is shown to be accurately equal to nu p in the approximate pressure range 0.3-0.9 Torr. nu p (hence nu p ) is shown to be related to the mean neutral gas flow velocity nu 0 according to nu p approximately 4 / 3 nu 0 .