Studying tungsten under the cyclic action of a plasma gun jet

We have studied the cyclic action of a plasma gun jet, which modeled nonstationary thermal load related to the edge localized modes (ELMs), on the surface of tungsten elements intended for the ITER divertor. The results revealed significant changes in both the structure and morphology of a surface layer. After 100 irradiation cycles, a columnar or “ridged” structure of elements perpendicular to the initial irradiated surface is formed. Exposure to 1000 cycles changes the mechanism of material degradation and radically modifies the character of the surface topography, since the ridges are melted with the formation of droplet structures. The surface becomes rough, a loose material layer appears under the irradiated surface, and a 100-$\mu$m-thick recrystallized layer is formed.