Heat transfer simulation of Alcator C-Mod Advanced Outer Divertor

Abstract

An Advanced Outer Divertor is being developed for the Alcator C-Mod to study D retention at reactor temperature with high power long-pulse discharges. The divertor will be operated at elevated temperature up to 600°C. To achieve this goal, the divertor will be structurally and electrically continuous along toroidal direction, requiring it to expand radially as temperature increases. This paper describes the finite element analysis and results of heat transfer simulations of the outer divertor. There are four aspects, with focus on the AFrame assembly. First of all, a 1/20th 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, etc. 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. Secondly, 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. Thirdly, heat transfer analysis is performed with a model including a tile and its mounting plate, to predict the effect of plasma heat load on divertor tiles. Finally, radiation simulation on multilayer thermal shields is presented. All the heat transfer simulations are completed by COMSOL, commercial finite element analysis software.