Influence of helium ion irradiation on the morphology and microstructure of CN-G01 beryllium

Abstract

Beryllium is considered as a candidate of ITER first-wall (FW) armor and neutron multiplier in fusion reactors. To assess the irradiation resistance of CN-G01 beryllium, which has been accepted as an alternative ITER-grade beryllium in China, 180 keV helium ions with fluences of 1.0 × 1017 ions cm−2, 5.0 × 1017 ions cm−2 and 1.0 × 1018 ions cm−2 were implanted at room temperature. The theoretical simulation of energy loss, damage distribution and helium concentration were proceeded by SRIM. In this paper, we report the experimental exploration of ion fluence effect on surface morphology and microstructure of irradiated samples. Field Emission Scanning Electron Microscope (FESEM) analysis depicted the formation and growth of helium bubbles at different irradiation ion fluences. No obvious exfoliation or cavities was observed on the surface at all ion fluences, suggesting a reliable radiation resistance of CN-G01 beryllium. Atomic force microscopy (AFM) morphology showed that the maximum height of bubbles was 47.8 nm. Surface roughness values increased slightly due to the formation of defects and bubbles on the irradiated beryllium surface. Nevertheless, the structural analysis demonstrated by grazing incidence x-ray diffraction (GIXRD), indicated an obvious preferred orientation on (101) peak at various ion fluences. Annihilation of defects caused by a small rise of the localized temperature could explain the increasing intensity of diffraction peak (101).