The growth of defect clusters was observed  in situ during irradiation. Various 30 or 300keV ions (He+, O+, Mg+, Ar+, Xe+) and 200keV or 1MeV electrons were used to produce a range of displacement cascade effects. Dislocation loops were created both inside and outside of the bombarded region, at 870K, under concurrent irradiation with 30keV ions and 1MeV electrons. Various phenomena occurred during concurrent irradiation with 300keV ions and 200keV electrons. These included the formation of cavities, the suppression of dislocation loop formation and the preferential formation of loops at the periphery of the focussed electron beam. The irradiation spectrum effects were explained in terms of ionizing, displacive and sub-threshold nuclear stopping powers, localized energy densities within displacement cascades, and flux distributions within the focussed electron beams. It was noted that cation diffusion from the inside to the outside of the electron beam, which was probably caused by the sub-threshold nuclear and ionizing stopping powers, played an important role in microstructure evolution during concurrent irradiation.

K.Yasuda, C.Kinoshita, R.Morisaki, H.Abe: Philosophical Magazine A, 1998, 78[3], 583-98