An Assessment of Alternative Divertors for the European DEMO

The uncertainties surrounding the physics of plasma exhaust and its centrality in reactor design require a thorough evaluation of promising alternatives as a precautionary measure to avoid delays in DEMO, if the ITER solution for the divertor could not extrapolate to reactor relevant machines. In this contribution, we review the physics and engineering work carried out within EUROfusion's work package DTT1/ADC on the subject (see Fig.1), showing with a quantitative assessment that alternative configurations provide a larger operating space than the single null according to multifluid simulations (in particular, lower Argon seeding levels and core concentration; lower separatrix density for comparable divertor protection; greater resilience to high power operations), but also highlighting the many engineering challenges that these configurations entail. The 3D engineering analysis of the alternative designs shows that the balance between port space for remote maintenance and the reinforcement of the supporting intercoil structures, stiffening the structure with respect to out of plane forces, is crucial to achieve acceptable solutions. In addition, active and passive magnetic control, pumping, neutronics and turbulence in alternative configurations will be discussed with quantitative analyses.