LAUSR

The effect of Primary Knock-on Atom (PKA) spectrum on the damage creation and subsequent deuterium trapping at the defects has been investigated using computer simulations and surrogate ion-irradiation experiments. The PKA spectrum generated by light ions resembles close to 14 MeV neutrons. Ion-irradiation experiments have been carried out with ions of Au, W, B, He and D of energies ranging from 100 keV – 80 MeV for a fluence range of 1.3 x 10 ions-cm to 5x10 ionscm. While 80 MeV-gold ions produced dense clusters of defects and dislocation loops, boron produced predominantly dislocation lines and dislocation loops. Molecular dynamics simulations show that at large PKA energies (>150 keV) the fragmentation of the cascade takes place which tend to limit the size of individual defect cluster. Transmission electron microscopy studies have shown that 80 MeV Au-irradiation which has significant fraction of PKA energies above fragmentation threshold has produced dense cluster of smaller defects (<12 nm). Deuterium irradiation experiments indicate that the defect produced during the irradiation might act as channels for diffusion leading to a significant shift in the implantation profiles.