Effect of Gamma Irradiation on Celluloid Film and Related Influence on the Registration of Alpha Tracks

Celluloid film, used as for α-track detection for its being one of the most sensitive solid state track detectors, was irradiated up to 3.5×107 rad by 60Co γ-rays. The radiation damage was examined by weighing a piece of the film before and after etching with sodium hydroxide solution under various conditions. Six molar sodium hydroxide solution at 50°C was found to be the most suitable etching solution for this irradiated celluloid film. On measuring the optical density, it was seen that the absorption curve for UV light shifted to the longer wavelength side accompanying an increase of absorption dose of γ-ray energy on the film. Both the gravimetric and the optical methods of determining radiation damage indicated its dependence on the γ-ray absorption dose. The sensitivity of α-track registration was also estimated by examining the appearance of α-track under the optical microscope according to etching time. The critical energy of the celluloid film for the registration of α-tracks decreased with the absorption dose of γ-rays.