Depth dependent damage profile in stainless steel irradiated with He-ions

Type 316 stainless steel was irradiated with 24 MeV He-ions up to 3.2 × 10²⁰ ions/m² at ambient temperature. A peak in microhardness occurred at a distance of 105 μm from the irradiated surface. Small dislocation loops were seen at depths ranging from 105 to 114 μm with the peak in number density at 110 μm. A pair of parallel lines with a space of 8 μm centered at a distance of 107 μm from the irradiated surface were revealed on the top surface of the specimen by chemical etching after post-irradiation annealing for l h at 1023 K. The parallel lines correspond to arrays of fairly large Frank loops aligned in narrow bands on each side of a region containing helium bubbles. The observed damage profiles agree with those predicted by Littmark and Ziegler.