Electron microscopy observations of radiation damage in irradiated and annealed tungsten

Abstract

In the present work tungsten samples were irradiated with W6+ ions with a kinetic energy of 20MeV in order to simulate radiation damage by fast neutrons. Two samples with cumulative damage of 2.3 and 6.36 displacements per atom were produced. The scanning transmission electron microscopy investigations were carried out in order to determine structure changes resulting from the irradiation. The evolution of the damage with post implantation annealing in the temperature range 673–1100K was also assessed. Damage profiles were studied at cross-sections.Scanning transmission electron microscopy studies of the lamellae after annealing revealed aggregation of defects and rearrangement as well as partial healing of dislocations at higher temperatures. The results confirm the higher density of radiation-induced dislocations in the near surface area of the sample (1.8*1014m−2) in comparison with a deeper damage area (1.5*1014m−2). Significant decrease of dislocation density was observed after annealing with a concurrent growth of dislocation loops. Transmission electron microscopy analyses show that the dislocation loops are perfect dislocations with the Burgers vectors of b=½[111].