Radiation-induced defect buildup and radiation-enhanced diffusion in a foil under energetic bombardment

The distribution of interstitials, monovacancies and vacancy aggregates containing two to six vacancies in a silver foil under irradiation was calculated as a function of both distance from the surface of the foil and irradiation time by numerically solving the rate equations for various temperatures (0–250°C) and internal sink concentrations (0,10 ^?5 and 10^?3). The calculations would be useful in areas of high-voltage electron microscopy, radiation-enhanced diffusion and void formation. The mobile defects (interstitials, monovacancies, divacancies and trivacancies) were assumed to react with each other, to annihilate at fixed sinks and to diffuse to the surface. Vacancy clusters larger than trivacancies were considered to be immobile, able to grow, but not dissociate. Humps on the steady-state concentration profiles for monovacancies and immobile vacancy clusters were found near the surface of a foil, provided the irradiation temperature and sink density were low and/or the defect production rate was quite high. The radiation-enhanced diffusion coefficient, $\text{D}{}_{\mathrm{rad}}$, of the material was calculated from the diffusivities of mobile defects and their steady-state concentrations, as a function of temperature, sink concentration, and Frenkel-pair production rate.