Gas-Insulation of a Hot Plasma

Abstract

THE attempts to heat a plasma to thermonuclear temperatures have all started from the idea that the plasma should be separated from the walls of the vessel by magnetic fields in vacuum. The purpose of this communication is to discuss another possibility, namely, to insulate the plasma from the walls by means of a magnetized gas at high pressure. As the thermal conductivity increases with temperature, a hot gas seems to be a poor insulator ; but at high temperatures, where the gas becomes ionized, the thermal conductivity can be decreased very much by a magnetic field. Its variation with the temperature is shown qualitatively in Fig. 1. The first maximum is due to the dissociation and the second to ionization, whereas the third is produced by the electron conductivity and the fourth by the ion conductivity. At high temperature the ion conductivity dominates and its asymptotic temperature variation is as T ^−5/2.