Selection of plasma-facing materials in next-step fusion devices

Designing a robust interface between a thermonuclear plasma and the solid material environment remains a major challenge for next-step fusion devices and future power fusion reactors. Challenging trade-offs in material choice for plasma-facing components were identified in the internationally co-ordinated R&D program supporting the Engineering Design Activities of the ITER project. This paper surveys factors relevant to material choices in next-step devices, describes advantages and disadvantages of the various options, and discusses how their application depends on the specific operational requirements. Advances in materials technology with high-Z materials, together with improved plasma control leading to reduction and mitigation of off-normal events such as disruptions and ELMs, are an essential part of the long-term solution.