The activation energy for the long-range intrinsic migration of self-interstitial atoms in metals, EmI, was an important physical quantity closely associated with microstructural evolution upon energetic particle irradiation. The EmI values for various metals were widely investigated through recovery experiments on specimens irradiated at low temperatures upon thermal annealing, and the values were estimated from the dependence of measured quantities of the specimens on the annealing temperature. On the other hand, the dependence of measured quantities on irradiation temperature was also expected to reflect the EmI values. It was of importance to compare the EmI values obtained by these two different kinds of experiments. However, no systematic studies were carried out along the latter line. In this study, the number densities of self-interstitial atom clusters formed in tungsten upon high-energy electron irradiation were directly measured as a function of the irradiation temperature using high-voltage electron microscopy. The analysis of the experimental data showed that the EmI value was in the range from 0.088 to 0.102eV or it was less than 0.046eV. These values were consistent with those obtained in a recovery experiment and a theoretical study, respectively.

Activation Energy for Long-Range Migration of Self-Interstitial Atoms in Tungsten Obtained by Direct Measurement of Radiation-Induced Point-Defect Clusters. T.Amino, K.Arakawa, H.Mori: Philosophical Magazine Letters, 2011, 91[2], 86-96