Thickness Variations Affecting Optical Properties of Un-irradiated and Gamma Irradiated PADC Polymer Films

Abstract: Nuclear track detectors (NTDs) are affected by particulate radiation (such as alpha particles (α-particles)) and non-particulate radiation (such as gamma rays (γ-rays)), which are electromagnetic radiation. The NTDS used were poly allyl diglycol carbonate (PADC), namely the CR-39 polymer. The films were reduced in thickness by long-term chemical etching in a NaOH/ethanol solution, down to 50 µm from as-received CR-39 sheets 750 µm thick. Gamma irradiation experiments were conducted on CR-39 polymeric detector samples at a single dose of 300 kGy for different thicknesses to investigate the thickness-dependent behavior of the detector material. The effects of gamma-irradiation of PADC on the optical properties were investigated. CR-39 polymer samples were irradiated with gamma radiation at a dose of 300 kGy. The different thicknesses of unirradiated and gamma-irradiated polymer samples were investigated using UV-visible spectroscopy. In this work, the direct and indirect energy band gaps for unirradiated and gamma-irradiated CR-39 polymer samples with different thicknesses were estimated. The values of the indirect energy band gap were compared with those of the direct energy band gap. The change in the optical energy band gap with decreasing CR-39 thickness at the same dose was discussed in terms of gamma-irradiation-induced modifications. The correlation between the optical energy band gap and the number of carbon atoms in a cluster was also discussed, and optical constants were estimated using Tauc's equation. The variation in CR-39 thickness samples is considerable, indicating that the detector is not optically stable.