A multiscale approach to defect evolution in tungsten under helium irradiation

We have studied He irradiation in tungsten from a multiscale point of view: Density Functional Theory (DFT) to obtain the binding energies of He to vacancy clusters, Binary Collision Approximation (BCA) and Molecular Dynamics (MD) to produce defect cascades and Object Kinetic Monte Carlo (OKMC) to study their evolution in larger temporal and spatial scales. A comparison between BCA and MD cascades produced by PKA at different energies has been done at different temperatures: at high temperature and at high PKA energies the OKMC results clearly depend on the defect cascades. 625 keV pulsed He ion irradiation has been simulated with cascades obtained by means of BCA and MD. The results show that in the case of ion irradiation, BCA results can provide good OKMC results. However, in the case of neutron irradiation producing high energy PKAs, BCA cascades clearly overestimate the number of FPs, which may have a strong influence on the OKMC results.