Effects of He, D interaction on thermal desorption of He and D2 and microstructural evolution in pure Fe

He and H atoms are produced in (n, α) and (n, p) nuclear reactions. In fusion reactors, energetic T and D, being isotopes of H, and He particles damage the surface materials. To investigate the He-D interaction, Fe, which is a model metal of choice in ferritic stainless steel that is used in fusion reactors, was irradiated separately by He or D2 ions and by combinations of He + D2 or D2 + He ions with the energy of 5 keV. The dose for single-species irradiation and each step of double-species irradiation was 1.0 × 1020 ions/m2. Thermal desorption analysis indicates that, in the case of single ion species irradiation, thermal desorption of D occurs at temperatures below 700 K, while the main thermal desorption of He occurs at 750 K and above 1200 K. The binding energy of He and defects is higher than that of D and defects. In the case of irradiation with combinations of ions species, however, the obtained thermal desorption spectra are the same, although the peak intensities are different, suggesting that the He-D interaction is weak. The sorption of D is more predominant for irradiations with He + D2. On the microstructure level, the irradiated samples exhibited larger voids following combined irradiations compared with those for irradiation with a single ion species after annealing to 1323 K. During the He + D2 irradiation, D atoms are effectively trapped owing to the defects induced by pre-irradiation with He.