Thermal responses of first wall limiters in the Tokamak Fusion Test Reactor

Abstract

A model was used for the heat flux to estimate the thermal responses and the sublimation rates of several first wall limiters proposed for the Tokamak Fusion Test Reactor. The critical parameter is the thickness of the scrape-off layer, or outer skin of the plasma. The thinner this is, the hotter the limiter will become after repeated discharges. The minimum tolerable thickness is about 0.5 cm for copper or graphite tiles over Nitronic 33 steel backing plates. For thicknesses less than this the steel will be too hot; the sublimation rates of most of the proposed first wall coatings for the tiles are sufficiently low to not contaminate the plasma.