Co-deposited layer characterisation and removal control by optical emission spectroscopy coupled to nano-second laser ablation

Optical emission spectroscopy, coupled with laser ablation, has been used to characterise plasma facing components. First results of feasibility studies have shown that specific lines of metallic impurities can be used to discriminate co-deposited layer from substrate (graphite). By recording these lines shot by shot, it is possible to follow in real-time co-deposited layer removal and to evaluate co-deposited layer thickness. It is also possible to evaluate, with this technique, impurity profiles versus depth. Furthermore, an hydrogen line has been recorded during the last experiments, indicating that such a technique could be implemented in situ, in a tokamak, to localise and quantify tritium retention.