Nanostructure evolution and surface modification of tungsten exposed to low energy, high flux deuterium plasma

One of the most important changes of plasma-facing material is plasma-induced damage which limits the material lifetime in fusion reactors. In this study, the influence of exposure conditions on tungsten nanostructure formation and surface modification was investigated. TEM specimens and bulk samples were prepared and exposed to deuterium plasmas with different fluxes (4.0-10.0 × 1021 D m−2 s−1), fluences (2.5-10.0 × 1025 D m−2) and temperatures (343-513 K), while ion energy was constant (60 eV). Distortion, nano-polycrystalline and amorphous structure were observed as irradiation damage. Increasing exposure intensity results in severer damage: (1) amorphous structure arises with increasing temperature; (2) deformation region greatly extends at a higher fluence; (3) degree of lattice distortion increases in high flux. Furthermore, surface morphology featured by blisters changes dramatically as well. Nanostructures and surface morphology observation indicates that nanostructure evolution is strongly related to surface modification, and it would influence the properties of tungsten.