Overview of comprehensive characterisation of erosion zones on plasma facing components

Morphology of carbon plasma facing components retrieved from the TEXTOR tokamak after long operation periods and exposure to total particle doses exceeding 7 × 1026 m−2 was determined. Emphasis was on the composition and structure of the erosion zones. Tiles from two limiters—the main toroidal belt pump ALT-II and auxiliary inner bumper—were examined using high-resolution microscopy, surface profilometry, ion beam analysis techniques and energy dispersive X-ray spectroscopy. The essence of results regarding the net-erosion zones is following: (i) microstructure of surfaces is significantly smoother than on a non-exposed graphite, whereas carbon fibre composites show similar appearance prior to the exposure and after; (ii) deuterium retention is 2–5 × 1021 m−2; (iii) the presence of plasma impurity atoms (e.g. metals) is detected predominantly in small cavities acting as local shadowed areas on the surface. The results are discussed in terms of processes of material erosion/re-deposition and tokamak operation conditions influencing the morphology of wall components.