Plasma facing and high heat flux materials – needs for ITER and beyond

Abstract

Plasma-facing materials (PFMs) have to withstand particle and heat loads from the plasma and neutron loads during reactor operation. For ITER knowledge has been accumulated by operation experience and dedicated tests in present tokamaks as well as by laboratory experiments and modelling. The rationale for the selection of PFMs in ITER (Be, W, carbon fibre reinforced carbon) is described with regard to the critical issues concerning PFMs, esp. erosion during transient heat loads and the T-inventory in connection with the redeposition of carbon. In the fusion reactor generation after ITER the very stringent conditions of increased surface power to be removed from the plasma, a lifetime requirement of several operational years, high neutron fluences and increased operation temperature are exerting even more severe constraints on the selection of possible materials. Comparing these boundary conditions with materials under development and their further potential, only a narrow path is left regarding heat sink and PFMs. In this context the investigations on W as first wall material carried out e.g. in ASDEX Upgrade are being discussed as well as laboratory results on W-based material systems. The implications of these results are the starting point of what should form a consistent programme towards plasma-facing and heat sink materials for a fusion reactor.