Erosion of marker coatings exposed to Pilot-PSI plasma

In this article, laser induced breakdown spectroscopy (LIBS) has been used to study plasma-induced erosion processes. Samples with ITER-relevant coatings were exposed to controlled plasma fluxes whose parameters were characteristic to those occurring in the reactor walls. After the experiments, erosion of the coatings and changes in their surface structure were determined using LIBS and a set of other surface-diagnostics methods. This way, the applicability of LIBS for in situ erosion/deposition measurements, particularly the influence of plasma exposure on the obtained LIBS spectra could be investigated in detail. Elemental depth profiles, extracted from the LIBS results matched well with those obtained by the other surface analysis methods. However, we observed that plasma-induced changes of the crystalline structure of target materials can significantly alter the laser-ablation rate. This is the main factor which influences the reliability of results obtained by LIBS.