Effect of dose rate, temperature and impurity content on the radiation damage in the electron irradiated NaCl crystals

The dependencies of void formation and radiolytic sodium accumulation on th e irradiation dose, dose rate, temperature and impurity content are analyze d within a framework of a theoretical model, which is based on a new mechan ism of dislocation climb. The mechanism involves the production of V-F cent ers (self-trapped hole neighboring a cation vacancy) as a result of the abs orption of excess H centers at dislocation lines. Voids are shown to arise due to the reaction between F and V-F centers at the surface of halogen bub bles. All reactions involved in the evolution of extended defects are contr olled by the difference between the absorption of H centers and F centers. This difference is determined by the material specific parameters responsib le for the bias factors of extended defects and by the mean concentration o f point defects. The latter depends on the temperature and dose rate as des cribed in the present paper. Impurities can facilitate or suppress radiatio n damage formation depending on their effect on the nucleation of extended defects under irradiation. This is demonstrated by comparing theoretical re sults obtained for dose dependence of colloid volume fraction at different dislocation densities with experimental data obtained in crystals doped wit h different impurities. (C) 2000 Elsevier Science B.V. All rights reserved.