Diffuse X-Ray Scattering in Fast-Neutron-Irradiated Copper Crystals

Nearly perfect copper crystals with dislocation densities less than {~} 10³/cm² have been irradiated with fast neutrons at doses up to 4×{}10¹⁹/cm², and the diffuse x-ray scattering resulting from the defects produced has been studied in a variety of situations. Measurements were made with a double-crystal spectrometer to allow observations of the scattering very close ({~} seconds of arc) to the Bragg peaks, for which a theoretical analysis of the data can be made. The diffuse scattering can be explained as resulting from defect clusters or dislocation loops {~} 100 {} in diam; there is an asymmetry of the diffuse scattering which appears to result from a predominance of large interstitial loops. This interpretation is consistent with electron-microscopy observations on these crystals. Diffuse scattering observations as well as anomalous x-ray transmission studies on irradiated crystals are suggested as very valuable tools to study the possibility of clustering phenomena in the annealing stages of various irradiated crystals.