Radiation defects in heavy ion-irradiated nickel at low temperature by X-ray diffuse scattering

We developed a reliable method of transferring specimens at low temperature after ion irradiation with a cryostat for X-ray diffraction measurements. Single crystal Ni specimens have been irradiated with heavy ions at 13 K. Transferring the irradiated specimens at low temperature without any warming up, defect structures were studied using X-ray diffuse scattering on annealing between 18 K and room temperature. We observed a q−4-dependence of the diffuse scattering intensity after the irradiation and the results indicated that there were both vacancies and interstitial clusters, which were associated with a displacement cascade. With increasing the annealing temperature of the irradiated Ni, the interstitial dislocation loops grew at 200 K and the radius and number of those loops began to decrease below 300 K.