Plasma–wall interaction: Important ion induced surface processes and strategy of the EU Task Force

In future thermo-nuclear fusion devices, such as ITER (International Thermonuclear Experimental Reactor), the interaction of the plasma with surrounding materials in the vacuum vessel constitutes one of the main remaining engineering problems. The choice of materials is a crucial point, which will determine issues such as the plasma facing components lifetime before refurbishment or the tritium inventory build up in the vessel, which should be limited for safety reasons. In order to tackle these issues, the European Task Force on Plasma–Wall Interaction has been implemented in the frame of EFDA (European Fusion Agreement) in the fall 2002 with the aim “to provide ITER with information concerning lifetime-expectations of the divertor target plates and tritium inventory build-up rates in the foreseen starting configuration and to suggest improvements, including material changes, which could be implemented at an appropriate stage.”The EU-PWI-TF brings together the efforts of 24 European associations in the following fields of investigation:
• Material erosion and transport in tokamaks.
• Tritium inventory and removal.
• Transient heat loads on plasma facing components.
• Dust production and removal.
• Associated modelling and diagnostic development.This paper will present the organisation of the EU-PWI-TF. It will provide examples for the multitude of surface processes in Plasma–Wall Interaction and present the status of knowledge concerning material erosion and hydrogen retention for the choice of ITER materials (Beryllium, Carbon and Tungsten).