Ostrich egg shell as an accurate retrospective dosimeter using electron paramagnetic resonance technique

This study investigates the dosimetric features of Ostrich egg shell (Oesh) using Electron Paramagnetic Resonance (EPR) spectroscopy to evaluate its potential as an accurate retrospective dosimeter. Key dosimetric characteristics, including sensitivity, dose-response, UV light effect, and temporal and thermal stability, were systematically evaluated. The EPR spectra of γ-irradiated samples revealed six radiation-induced signals (S₁–S₆) corresponding to biocarbonate radicals (CO₃⁻, CO₃³⁻, and CO₂⁻), with the dosimetric peak centered at g = 2.0040 ± 0.0016. The material exhibits a highly linear dose-response relationship in the range of 0.3 Gy to 1 kGy (R > 0.999). With a detection limit of 0.21 Gy, Oesh demonstrates significantly higher sensitivity than other egg shell dosimeters. The EPR signal remained stable after seven days of storage at ambient temperature with less than 18% fading depending on modulation amplitude value. Crucially, exposure to UVA and UVC light did not affect the γ-induced radicals, confirming the robustness of the dosimetric centers. The ratio of the dosimetric peaks S4 to (S4 + S5) exhibits a time-dependent decay that can be modeled to determine the elapsed time since irradiation. Furthermore, the measured energy dependence factor for Cs-137 (662 keV) is 1.01 relative to Co-60 (1250 keV), confirming the material’s reliability across relevant photon energies greater than 100 keV. These results establish Ostrich egg shell as a promising, highly sensitive, and stable material for both retrospective dosimetry and general radiation monitoring applications.