Plasma sprayed tungsten-based coatings and their performance under fusion relevant conditions

Several tungsten-based coatings were produced using water stabilized plasma spraying. Their basic properties (structure, composition, etc.) were characterized. Their behavior under high temperature plasma conditions was investigated at a small-size tokamak CASTOR. The samples were inserted into plasma at various radii and exposed by standard plasma discharges. Main plasma parameters, impurity radiation and specimen temperature evolution were observed. Only a local influence of the tungsten presence was found; no significant erosion was observed. Selected coatings were tested under high heat fluxes at the electron beam facility JUDITH at FZJ, to simulate disruption conditions. The samples were subjected to varying loads, while the absorbed current, surface temperature and particle emission were recorded. The induced changes were observed by surface profilometry, SEM and optical microscopy. The coatings were able to absorb about 0.5 GW/m2 (2.5 MJ/m2) in thermal shock loading without significant damage.