Materials perspective - A survey of plasma facing materials for fusion power plants

A future fusion power plant will confine very hot ionised gas or 'plasma' containing the hydrogen isotopes deuterium and tritium in a toroidal magnetic chamber (or 'tokamak'). The energy from the resulting fusion reactions will be released as energetic a particles and neutrons. The solid material lining of the inner wall of the chamber (the plasma facing material or 'armour') will be exposed to fluxes of particles and radiation and this armour must shield the outer mechanical structures from plasma damage. At the surface of the armour, the physical processes are complex and there will be an interchange of particles between solid and plasma. Where ions strike surfaces, they are implanted and sputtered atoms and neutrals are released into the plasma. Therefore armour and plasma form a coupled system. Projecting from current experimental knowledge, this survey gives a perspective of the conditions and behaviour of three leading candidate plasma facing materials (carbon, beryllium and tungsten) in a power plant.