DETECTION AND ANALYSIS OF MICROSCOPICALLY INVISIBLE CASCADE DEFECTS IN 14 MEV NEUTRON-IRRADIATED ALUMINUM AND IRON

Experiments to detect created by cascades in aluminum and iron, in which no defect structures have been observed by electron microscopy are designed by effectively combining 14 Mev neutron irradiation with electron irradiation damage by a high voltage electron microscope. The shrinkage and annihilation of interstitial loops formed by electron irradiation by subsequent neutron irradiation was most marked in aluminum and but occurred to some degree in iron. The result is explained by a simple model of diffusion of vacancies and interstitials based on the difference of the initial distribution profile between the two kinds of point defects in a cascade. The extent of the annihilation of neutron radiation induced defect clusters in iron formed at room temperature is detected by the variation of the interstitial cluster deformation at 323 K by high energy electron irradiation. Two annealing stages of 523-573 K and 573-623 K are observed.