Micro-distribution of fuel and metal in carbon-based plasma-facing materials

Surfaces of carbon fibre composite tiles from the toriodal pump limiter of Tore Supra were examined with ion beams to determine simultaneously the distribution of co-deposited deuterium and metallic plasma impurities (i.e. steel components). With a 3He+ ion beam the reaction 2D(3He,p)4He was used for deuterium, 12C(3He,p)14N for carbon, whereas beam-induced x-ray emission and back-scattered ions served for the detection of heavier elements. Measurements were made both with a 1 mm beam and by a micro-beam focused down to 20 μm spot size and scanned over the sample to obtain maps of the different elements. Distribution maps of different elements—fuel and metal species—are presented for four distinct regions on the limiter: erosion zone, shadowed area, thin deposits and thick flaking deposits.