The EU strategy for solving the DEMO exhaust problem

Highlights: • EUROfusion has developed a broad approach to address the exhaust challenge for DEMO. • The baseline exhaust strategy builds on the solution foreseen for ITER. • Alternative divertor geometries solutions are studied as risk mitigation strategy. • Liquid metal targets using Sn-filled meshes are studied as risk mitigation strategy. • Intrinsically ELM-free solutions are needed for EU DEMO operation. Exhaust of power and particles is crucial for the DEMO device and the EU has developed a strategy to address the challenges. This strategy consists of a conventional approach based on extrapolation of the ITER solution (detached lower single null divertor) as well as the development of alternatives as risk mitigation. These comprise alternative magnetic divertor geometry, liquid metal targets and intrinsically ELM-free operational scenarios. On the experimental side, the EUROfusion programme has initiated both upgrades to existing linear and toroidal devices as well as plans to engage in new devices presently under construction in the EU. In parallel, the theory and modelling efforts are ramped up in a targeted effort to obtain the necessary understanding for safe extrapolation to DEMO. This is especially important for the alternatives, which cannot be tested in ITER.