RADIATION FRONTS IN TOKAMAK DIVERTOR PLASMAS

The impurity radiation from a tokamak divertor can be significantly en hanced due to the formation of a V-shaped impurity radiation front and the effects of perpendicular plasma heat conduction. For some conditi ons, the transition to a V-shaped radiation front can have a bifurcati on character, such that the impurity radiation region jumps from the d ivertor targets to the entrance into the divertor. The divertor geomet ry can play a significant role in the formation of a V-shaped impurity radiation front. The analysis of the energy transport and impurity ra diation suggest that divertor geometries with ''vertical'' target, neu tral gas recirculation where sidewalls, or their combination are the m ost attractive from the point of view of the formation of a V-shaped r adiation front and the plasma energy loss. (C) 1998 American Institute of Physics. [S1070-664X(98)00806-4]