Depth profiles of energy deposition near incident surface irradiated with swift heavy ions

Ogawa, Tatsuhiko   ; Ishikawa, Norito   ; Kai, Takeshi   

Heavy ion irradiation, which deposits energy locally in materials, is widely used to study new material modification and radiation-induced damage. So far, radial distribution of energy deposition by heavy ions were well studied. By contrast, depth profile of energy deposition was usually assumed to be uniform but the energy deposition near the incident surface is likely suppressed because the delta-rays are pushed by the incident heavy ions. In this study, spatial distribution of energy deposition in the materials exposed to heavy ions is calculated by using a track structure simulation code RITRACKS. The result showed that energy deposition is suppressed in the first 2 nm of water and that beyond 2 nm is uniform. This result can be applied to the materials other than water by scaling with electron density. It is indicated that reactor fuel pins damaged by fission products and the materials modified by heavy ions receive less energy deposition and less radiation effect in the first 2 nm.