Dual-beam irradiation of I+/--iron: Heterogeneous bubble formation on dislocation loops

In order to understand the evolution of materials under irradiation conditions similar to those in future fusion reactors, we have irradiated high purity iron in situ in a transmission electron microscope with 1 MeV Fe super(+ ions while simultaneously implanting 15 keV He) super(+) ions, at 500 degree C. Once ~1 dpa/500 appm He were reached, helium bubbles and large dislocation loops were observed. The study reveals that helium bubbles nucleated heterogeneously: a majority of them were observed inside the large dislocation loops.