Some remarks on in-situ studies using TEM-heavy-ion accelerator link from the stand point of extracting radiation damage caused by fast neutrons

Radiation damage of materials for fission and fusion reactors has been scaled in terms of the number of displacements per atoms (dpa). The method of evaluating the dpa has been established and standardized. However, it has become obvious that more detailed analyses are required, particularly for the nature and spatial distribution of the introduced point defects and their clusters. Such detailed nature of the defects introduced is thought to be governed by the primary knock-on atom (PKA) spectrum, A number of trials to elucidate the PKA dependent radiation effects by choosing the mass and energy of the incident ions have been explored. In some cases, defect formation by a single impinging ion has been observed. However, it has also been recognized that there are a number of artefacts arising from energy deposition distributions, existence of surface sinks together with radiation induced surface modifications and so on. In this paper, discussion will be made on how to establish irradiation correlation between neutron and heavy ion irradiations in a cascade damage formation regime. For the past fifty years, the correlation between neutron and ion irradiations from the view point of simulating the neutron radiation damage by ion irradiations has been discussed many times. However, the correlation itself has not been fully discussed separately. This is the major objective of this paper.