Interstitial clustering in cascades in fast-neutron irradiated aluminium by diffuse X-ray scattering

Abstract We measure diffuse X-ray scattering close to Bragg reflections in aluminium single crystals after irradiation with fast-neutrons at 4.6 K. Comparing the intensity of the Huang scattering with that measured after e-irradiation for the same radiation-induced resistivity leads to the result that in Al during n-irradiation interstitial clusters containing an average of three defects are formed. The cluster size is independent of dose up to 2.4 × 10 18 n / cm 2 which indicates the clusters to be formed in a single cascade. Very close to the Bragg peak is a modulation of the Huang intensity which shows that the interstitial clusters are not randomly distributed but are correlated in cascades. Fitting a theoretical curve to the modulation, a cascade radius R k = 50 A is obtained. During annealing the clusters grow and finally form interstitial loops. Long-range migration of the interstitials away from their nascent cascade is observed.