ENGINEERING AND MATERIALS ISSUES IN DESIGNING A COLD-GAS DIVERTOR

One of the key challenges facing the International Thermonuclear Exper imental Reactor (ITER) Project is the development of plasma-facing com ponents (PFCs) that can withstand the severe environmental conditions at the plasma edge. The most intensely loaded element of the PFCs is t he divertor. The divertor must handle high fluxes of energetic plasma particles and electromagnetic radiation without excessive impurity bui ldup in the plasma core. The ''cold-plasma-target'' mode of divertor o peration proposed for ITER expands the divertor design window to inclu de several alternate heat sink and armor materials that were not avail able for the previous ''high recycling divertor'' approach. In particu lar, beryllium armor can now be considered with copper, niobium and va nadium heat sink materials; and helium or liquid metal coolants are fe asible in addition to water. This paper presents material properties a nd compatability assessments for these materials and coolants along wi th parametric studies of thermal and mechanical performance. A viable design window is found for copper and niobium heat sinks with berylliu m armor, but not for vanadium unless thin (similar to 1 mm) coolant st ructures can be accommodated mechanically.