Thermal response of substrate structural materials during a plasma disruption

Intense energy fluxes to in-vessel components like the first wall and the divertor plate of a fusion reactor are expected during plasma disruptions. This high energy deposition in short times may cause severe surface erosion of these components resulting from melting and vaporization. Coatings and tile materials are proposed to protect and maintain the integrity of the underneath structural materials from both erosion losses as well as from high thermal stresses encountered during a disruption. The coating thickness should be large enough to withstand both erosion losses and to reduce the temperature rise in the substrate structural material. Yet the coating thickness should be minimized to reduce potential problems from radioactivity, toxicity, and plasma contamination. Tile materials such as graphite and coating materials such as tungsten and beryllium on structural materials like copper and steel are analyzed as potential divertor and first wall design options. The disruption is assumed to be composed of two phases: a thermal quench phase followed by a current quench phase. The minimum coating thickness required to protect the structural material is discussed for range of disruption parameters. 7 refs., 8 figs.