CORRELATION OF VACANCIES IN ALPHA-IRON AND COPPER AFTER LOW-TEMPERATURE NEUTRON-IRRADIATION OBSERVED BY SMALL-ANGLE SCATTERING OF SYNCHROTRON-RADIATION

The correlation of vacancies in Fe and Cu, irradiated with fast neutro ns at low temperature, was examined by small-angle scattering (SAS) of synchrotron radiation. The scattering curves were analysed in terms o f a distribution of depleted zones (DZ) according to the appropriate r ecoil spectrum, After irradiation and annealing at 90 K single vacanci es and small agglomerates were found in Fe. 70% of them were correlate d in DZ with an average radius of 12.6 Angstrom,and a mean vacancy con centration of 1.1%. In Cu we observed larger agglomerates-<n> = 11-15 vacancies-in DZ with an average radius of 8.2 Angstrom and a mean vaca ncy concentration of 5.2%. A strong scattering signal at very low scat tering angles is attributed to correlations between the individual cas cade zones, During recovery we observed agglomeration of the vacancies in both metals. While in Cu the correlation between individual DZ sur vived annealing at 430 K, the correlation vanished in Fe samples durin g annealing in stage m. A computer code was developed to simulate the correlation between the individual cascades in Fe. It was found that t he observed negative curvature of the resistivity damage rate can be e xplained by this correlation effect.