Thermal FEA for Alcator C-Mod Advanced Outer Divertor

An advanced outer divertor is being developed for Alcator C-Mod to study reactor fuel (tritium) retention and plasma wall material interaction physics at reactor temperatures with high power long-pulse discharges. The divertor will be operated at controlled temperature of 600 °C. To achieve this goal, the divertor will be structurally and electrically continuous along the toroidal direction, requiring it to expand radially as temperature increases. This paper describes the thermal finite element analysis (FEA) and results of the outer divertor. There are four aspects, with focus on the A-Frame assembly. First of all, a one twentieth module of the full divertor is composed of divertor tiles, tile mounting plate, heaters, divertor gusset, A-Frame support, spherical bearings, bracket, halo current shunt, vessel gusset, and so on. By adjusting the power of each of the seven toroidal divertor heaters, the tiles achieve a uniform temperature poloidally with toroidal temperature variation within allowables. The temperature of each component is evaluated, and results are used to support the design changes. Second, radiation simulation on multilayer radiation shields behind divertor plate is presented. Third, radiation simulation of the diverter heater itself is done to understand more details of heat transfer from the heater to the surrounding tiles and support plates. Finally, thermal analysis is completed with a model including a tile and its mounting plate, to predict the effect of plasma heat load on divertor tiles. All the thermal FEA was performed with COMSOL, a commercial FEA software.