Void Formation in Heavily Irradiated NaCl

Experimental and the oretical results are presented on the formation of voids discovered recently in havily irradiated NaCl. Experimental data show that for NaCl samples with particular dopants, the development of radiation damage, such as Na-colloids, chlorine inclusions and voids does not show a saturation as a function of the dose. A quantitative comparison of the new model for radiation damage in alkali halides with experiemental data is presented. Mean sizes and volume fractions of all types of observed defects are calculated. It is shown that voids formed due to agglomeration of F centers and cation vacancies can grow to the dimensions exceeding the mean distance between colloids and bubbles, eventually absorbing them, and, hence, bringing the halogen gas and metal to a back reaction. Impurities are shown to play a major role in the void development with increasing irradiation dose, which strongly affects the radiation stability of NaCl.