The role and importance of IBA in studies of wall components in controlled fusion devices

EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB, UK

1. Fusion Plasma Physics, Royal Institute of Technology (KTH), 100 44 Stockholm, Sweden
2. Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
3. Institut fürKlima- und Energieforschung, Forschungszentrum Jülich, D-52425 Jülich, Germany
4. CCFE, Culham Science Centre, Abingdon, OX14 3DB, UK
5. Max-Planck-Institut fürPlasmaphysik, 85478 Garching, Germany

First wall materials in controlled fusion devices undergo serious modification by several physical and chemical processes arising from plasma–wall interactions. This includes material erosion, transport of eroded species in the plasma and re-deposition leading to the formation of mixed-material layers. Detailed information is required for the assessment of: (i) material lifetime; (ii) accumulation of hydrogen isotopes in wall materials, i.e. fuel inventory; (iii) dust formation. These issues are crucial for the economy and safety of reactor operation. As a consequence, these are the driving forces for detailed study of plasma-facing materials (PFM) and components (PFC).

A large variety of materials research methods are used to determine the morphology and properties of wall components and probes retrieved from fusion devices after entire experimental campaigns (plasma operation of up to 105 s) or short-term tests in order to perform relevant experiments and to obtain broad characterization of materials. Ion beam analysis techniques play a particularly prominent role here because of their isotope selectivity in the low-Z range (1-10), high sensitivity and possible combination of several methods in a single run.

The aim of the talk is to provide an overview of experimental procedures and results obtained in the examination of materials from JET (the largest tokamak), TEXTOR and ASDEX Upgrade. The presentation is structured along the points: “what” is to be analysed and “why”, and then “how” the analyses are carried out. The role of 3He-based NRA, RBS, PIXE (standard and micro-size beam) and HIERDA in fuel retention and material migration studies is presented. The use of tracer techniques with rare isotopes (e.g. 13C, 15N, 18O) or marker layers on wall diagnostic components is described. Development of equipment to enhance research capabilities and issues in handling of contaminated materials are addressed.