The role of inert gases in first wall phenomena in fusion devices

Abstract

The first wall surfaces of fusion devices will be exposed to bombardment by inert gaseous projectiles such as helium. The flux, energy, and angular distribution of the helium radiation will depend not only on the type of device but also on its design parameters. For near term tokamak devices, the first wall surface phenomena caused by helium bombardment that appear to be quite important are physical sputtering and radiation blistering. Examples of these processes for a number of first wall candidate materials are discussed. While the physical sputtering phenomenon is understood, the mechanism of blister formation is not yet fully comprehensible. The various models proposed for radiation blistering of metal during helium bombardment is critically reviewed in the light of most recent experimental results.