RESUMO
In this study, the effect of high γ-doses on the track parameters, structure as well as optical properties of pristine and γ-irradiation CR-39 nuclear track detector (NTD) were investigated. CR-39 detectors were exposed to γ-doses from 50 up to 500 kGy and then irradiated by fission ions (F.F) of fluence from 252CF source. The track diameter (D), bulk etch rate (VB), etch induction time (EIT), cut-off or saturated time (tcut-off) for saturated diameters and projected track length (Lo) of normally and inclined incident fission tracks were estimated for different removal layers (h). A linear relationship between D and γ-doses (Dγ) up to 500 k Gy was obtained. The VB for pristine and for γ-irradiated CR-39 was determined. A linear behaviour of VB was obtained up to 300 kGy. Etch induction time (EIT) and saturated time (tcut-off) of pristine and γ-irradiated detectors for normal and inclined fission ions tracks were evaluated respectively up to 500 kGy. Each EIT and tcut-off decreased exponentially fast with increasing γ-doses but the inclined incidence appeared earlier than normal case. Pristine and γ-irradiated CR-39 detectors were examined using FTIR and UV-Vis spectrophotometer. From this study, a linear relation of band gap energies (Egap) as a function of γ-doses, Dγ, was obtained. The value of (Egap) decreased when increasing γ-doses for direct and indirect transitions, respectively. In addition, a systematic increase of Urbach energy (EU) was recorded together with the Dγ increase. Moreover, a linear behavior of the refractive index (n) along with γ-irradiated CR-39 plastic detector was observed via direct and indirect methods.
