Introduction to divertor physics

A brief review will be given on the physics of divertor, which plays a very important role in magnetic confinement devices. The divertor "diverts" the power and particles coming out from the core plasma to a volume separated from the core. In the divertor, intense interaction between the plasma and the wall surface takes place, where significant portion of the power from the core is deposited and particles are pumped out after many cycles of neutralization and reionization. Thus the components directly facing the hot core are protected from the intense heat and bombardment of plasma particles.The hot core is protected from the direct ingress of impurities from the divertor. Concentration of heat onto narrow zones in the divertor makes the heat removal from the divertor the most challenging issue of the fusion reactor design. In the first part of this talk, various physical processes that characterize the divertor are reviewed, including collision, diffusion, sheath, presheath, ionization, charge exchange, recombination, radiation, retention, etc.In the second part of the talk, heat load during transient processes, i.e. disruption and ELMs, are reviewed.In the third part of the talk, we discuss how a liquid metal divertor can contribute to solution of these problems.プラズマ・核融合学会 九州・沖縄・山口支部 特別講