Defect production and formation of helium-vacancy clusters due to cascades in α-iron

Displacement cascades are simulated by molecular dynamics methods in α-Fe containing different concentrations of substitutional He atoms. Primary knock-on atom (PKA) energies, E p, from 0.5 to 5 keV are considered at the irradiation temperature of 100 K. The concentration of He in Fe varies from 1 to 5 at%, and the results are compared with the simulations performed in pure α-Fe. We find that the total number of point defects increases with increasing He concentration. The present studies reveal the formation and the configurations of He-vacancy clusters in the cascades of α-Fe. Furthermore, the production efficiency of He-vacancy clusters increases with increasing He concentration and PKA energy. The nucleation mechanisms of He-vacancy clusters in displacement cascades are discussed in detail