Growth rates of interchange modes in the dense z-pinch and gas blanket effects

Abstract

A class of models of the dense z-pinch in which the bulk of the plasma is neutrally stable against interchange is studied. At a radius a the plasma is abruptly terminated and surrounded by a gas blanket. Instability results from the surface current necessary to maintain pressure balance at the plasma-gas interface. A single dispersion relation applies to all models in this class and shows two effects of the gas blanket in reducing growth rate. (1) Partial support of plasma pressure by external gas pressure reduces the driving force for the instability, and (2) mass loading of the relatively dense neutral gas reduces growth rate