Irradiation damage of reduced activation ferritic/martensitic steel CLAM exposed to low-energy high-flux D + He mixture plasma

Abstract

Irradiation damage behavior of reduced activation ferritic/martensitic steel CLAM exposed to D + He mixture plasma was extensively investigated using the linear plasma facility PSIEC at a sample temperature of ∼800 K with an ion flux of ∼4.0 × 1021 m−2 s−1, an ion fluence of ∼7.0 × 1024 m−2 and an incident ion energy of ∼89 eV. Fiber-like nanostructure fuzz was formed on the irradiated CLAM steel surface. D and He bubbles were observed both inside and under the fuzz structure from cross-sectional TEM characterization. Damage level of the steel surface has been found to gradually increase as increasing He concentration in the mixed plasma. The growth process of fuzz can be described as pinholes (which originated from nano-bubbles) to nano-sphere structures, wavy erosion layers, rods, and eventually develops to nano-fuzz. Tungsten enrichment in the near-surface has been determined after plasma exposure due to preferential sputtering of middle-Z elements of iron and chromium. The measured surface tungsten concentration varied from 1.9 to 4.0 wt.%, depending on He concentration in the plasma. Obtained sputtering yield increased as well with increasing He concentration in the mixed plasma.