3 - Plasma exhaust

Abstract

Plasma-materials interactions (PMI) are well-managed in present-day devices, but become more challenging for ITER and reactors. Plasma exhaust basics are discussed, with a focus on the use of divertors to manage steady-state power, particle, and momentum exhaust. The factors that determine the peak heat flux, which must be maintained below known technological heat transfer limits, are emphasized. The need to mitigate transients, both repetitive edge localized modes and disruptions, as well as the presence of 3D perturbations that cause additional heat flux peaking, are described. Finally, protection of the wall from PMI, and the candidates for the materials that formulate the plasma facing surfaces, including solids and liquids are reviewed. Due to the higher power density, longer pulse length, and neutron environment, the plasma exhaust challenges for DEMO are more difficult than ITER, possibly requiring additional improvements from innovative divertor concepts presently being studied by the community.