BPX divertor conceptual design and analysis

For its primary mode of operation, the Burning Plasma Experiment (BPX) uses a double-null divertor for the removal of energy and charged particles from the plasma. Due to the high-power densities and the use of inertial cooling, high-thermal-conductivity annealed pyrolytic graphite (PG) and 1D carbon fiber composites are the two leading candidates for the plasma facing material. To maximize the power handling capability of the divertor, a tile thickness (normal to the plasma facing surface) greater than 30 mm, essentially infinitely thick for the burn durations being considered for BPX, is used and the separatrix is swept across the divertor surface to spread the heating over as large an area as possible. In the baseline divertor design concept, an arrangement of 546 modules forms a continuous surface, at the top and bottom, around the toroidal circumference of the vacuum vessel. Each divertor module consists of PG tiles housed in a metallic support frame which mounts to the vacuum vessel wall at four locations. The PG tiles have a c-direction thickness (normal to the PG tile laminations) of 6.35 mm and are oriented poloidally to minimize the eddy current forces induced during disruptions and to accommodate the thermally induced stresses during normal operation. >