Comparison between bulk and thin foil ion irradiation of ultra high purity Fe

Accumulation of radiation damage in ultra high purity iron under self ion irradiation without and with simultaneous He implantation was investigated in bulk and thin foil form to assess, on the one hand, the effect of free surfaces and, on the other hand, the influence of He. Specimens were irradiated at room temperature to a dose of 0.8 dpa and similar to 900 appm He content. We found in thin foils after irradiation with single beam a majority of a(0) < 100 > type loops, while in the presence of He it is the 1/2 a(0) < 111 > type loops that prevail. In single beam irradiated bulk samples most of the loops are of 1/2 a(0) < 111 > type. In both bulk and thin foils density of defects visible in transmission electron microscope is considerably higher when He is implanted with prevailing 1/2 a(0) < 111 > dislocation loops, indicating that He stabilizes them. (C) 2013 Elsevier B.V. All rights reserved.