Power and particle exhaust in tokamaks: Integration of plasma scenarios with plasma facing materials and components

Fusion ignition, on the one hand, and particle and power exhaust, on the other, impose often conflicting criteria on the plasma scenario – the former requiring the plasma to be sufficiently heated, fuelled and confined, the latter the helium ash, impurity ions and the total input + fusion power to be removed without undue damage to the reactor itself, specifically its plasma facing components (PFCs) – necessitating an optimization of the latter to attain the optimum fusion gain for a given reactor design. Foremost among these problems is the issue of power exhaust, including both steady-state and transient heat loads on PFCs. This review examines the various strategies of reducing plasma loads on PFCs at the minimum penalty to the performance of a fusion reactor, specifically ITER, and attempts to quantify the impact of a given PFC limit in terms of the relative change to the fusion gain factor compared to the no-limit value.