Studies of the Early Afterglow in Helium and Argon Plasmas

Abstract

Spatially resolved measurements of parameters during the early afterglow of helium and argon plasmas are presented. The investigated plasmas were contained in a vessel with a wall temperature much less than the electron temperature at the center of the plasma. All measured parameters developed nonuniformly. In spite of the high thermal conductivity of the free electrons, a temperature gradient was supported; the electron temperature being highest in the center of the vessel. The mechanism by which these gradients were supported is discussed. Both the electron and neutral gas temperatures remained elevated at several thousand degrees for at least 200 μsec into the afterglow. Attention is also focused on the effect of spatially nonuniform plasma parameters on transport processes as well as the dependence of the net decay on the cold walls.