Relevancy of displacement cascades features to the long term point defect cluster growth

Displacement cascades in iron have been generated by means of the MARLOWE binary collision approximation (BCA) code with primary knock-on atom (PKA) energies ranging from 5 to 100 keV. They serve as input for modelling long term evolution by means of the LAKIMOCA Object Kinetic Monte Carlo code. It is found that the size distributions of the fractions of vacancy and interstitial clustered in the long term are not significantly dependent on the PKA energy in this range. Since the subcascade formation, morphology and spatial extension, as well as the spatial correlations between primary point defect positions do depend on the PKA energy, it is concluded that the size distributions of clustered point defects fractions in the long term do not depend on these cascade features. In contrast, the size distributions of clustered point defect fractions in displacement cascades are found to be independent of the PKA energy while their spatial correlations strongly influence the cluster size distributions in the long term. The use of a mean field approximation in cluster growth kinetics predictions is thereby invalidated. Irradiation dose and dose-rate are also found to be determinant factors governing the long term evolution.