DIFFER Seminar: Power and particle exhaust in the W7-X divertor - an introduction and overview

The exhaust of particles and heat is one of the unresolved challenges on the way to a future fusion reactor. The main exhaust concept explored in the current fusion experiments is based on the modification of the magnetic edge topology by diverting the outermost field lines to dedicated target areas physically distant from the core plasma. This concept, called the "divertor", has been thoroughly explored in the case of tokamaks for over forty years, and it is now being investigated in the Wendelstein 7-X (W7-X) stellarator. The 3D nature of W7-X prevents the adoption of poloidal divertors developed for tokamaks. Instead, W7-X features an exhaust concept called the "island divertor", which exploits magnetic islands induced by the main coils at the plasma edge to connect discrete target plates. The combination of islands and target plates results in heat and particle handling capabilities that are significantly different from that in tokamaks. This presentation will give an overview of the main characteristics of the W7-X island divertor, and compare them with the well-established tokamak features.