Anomalous-x-ray-transmission investigation of neutron-irradiated copper: comparison of theory and experiment

In this study we have made anomalous-x-ray-transmission measurements on nearly perfect copper crystals that had been irradiated with fast neutron doses varying from 3.6 to 10.9 × 10¹⁸/cm² (E>0.6 MeV). The observed decrease in intensities for 111, 220, and 222 reflections with CuKα, MoKα, and AgKα x rays was expressed in terms of effective absorption coefficients. These absorption coefficients increased linearly with neutron dose. They have been analyzed in terms of the theory of Dederichs, and it has been shown that these data are consistent with the presence of defect aggregates in the form of dislocation loops. It has also been shown that the theory can explain the wavelength and reflection dependence of the observed absorption coefficients for these neutron doses when the calculations are scaled to the measured data for the 111 reflections of MoKα and CuKα radiations. Therefore, these data have provided a successful test of the functional dependence of the theory, independent of the defect concentration and size distribution.