Tungsten as material for plasma-facing components in fusion devices

The use of tungsten (W) as material for plasma-facing components (PFM) in fusion devices is reviewed with respect to its plasma and material compatibility under burning plasmas conditions. Fusion-relevant plasma operation with W walls is characterised by the need to operate at high edge densities, no or moderate density peaking, and external tools to control the W transport in the plasma core. Several surface and material issues related with the high particle fluencies in fusion devices needs further R&D but are not considered from present view to seriously limit the use of W as PFM. Reliable control of Edge Localised Modes (ELMs) and disruptions is indispensable for the application of W, both to control the W transport in the edge and to avoid target melting in uncontrolled events which can seriously detoriate the operational performance of the device. For DEMO and reactors, the behaviour of W under large neutron fluencies has to be further clarified and measures must be developed to mitigate degradation of material properties by neutron damage.