Ion bombardment of alkali halides, III: Track-effect analysis of measured damage profiles in KCl

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Abstract
Single crystals of KCl were bombarded with monoenergetic beams of protons (1.5 MeV and 2.3 MeV) and alphas (2.3 MeV). Fluences varied from 1012 to 1014 cm−2. Combining the results of a photomicrographic procedure with values of crystal optical density, profiles yielding F centers/cm3 versus depth were obtained. It is observed that F-center concentration does not follow dE/dx. Profile shapes and magnitudes are accounted for in terms of the established concept of an ion infratrack, characterized by high energy density and dose rate, surrounded by a region of low energy density. The latter is assumed to have an F-center production efficiency characteristic of electron beam irradiation. The infratrack is found to have a significantly higher efficiency and to dominate F-center production. Analysis of data indicates that infratrack efficiency versus velocity may be independent of the identity of the incident particle, and leads to predictions regarding anticipated F-center production by heavy ions.