Design of limiter/divertor first-wall components for Alcator C-MOD

A molybdenum first-wall heat shield will be used during the first phase of Alcator C-MOD operation. The heat shield is composed of approximately 7000 tiles (2-cm thick by approximately 2.5 cm×3.5 cm) and extends over three plasma-wall interaction zones: inner limiter, shaped-divertor, and flat-plate divertor. The heat shield and its support hardware are designed to withstand plasma disruption forces and, for the case of the shaped-divertor, to spread plasma exhaust of heat and particle fluxes over a large first-wall surface area. Peak surface heat fluxes are conservatively estimated (assuming no edge radiation) to be in the ranged of 6 MW/m² for the limiter and shaped-divertor tile surfaces with total input powers in the range of 6 MW. Flat-plate divertor surfaces are projected to experience the highest heat loads, exceeding 40 MW/m². The first-wall armor features a regular pattern of poloidal and toroidal `tunnels´ which are used to run cabling for magnetic pick-up loops and thermocouple wires. The present design allows the outer shaped-divertor tiles to be electrically isolated from the vacuum vessel