Uncertainties in low γ-dose determinations by means of ESR using the biomaterial modern coral reef

The ESR spectrum of unirradiated modern aragonite coral (CaCO3) material from the Red Sea (Hurgada area) is characterized by four signals with spectroscopic splitting factors of g=2.0056, 2.0030, 2.0006 and 1.997. The most intensive and stable line in this spectrum is attributed to CO2- radicals at g=2.0006±0.0005. The dose response from 50 mGy to 20 Gy, energy dependence and effective atomic number are calculated so as to investigate coral as a dosimeter material in the clinical dose range. The lower experimental γ-dose limit was found to be 50 mGy with signal-to-noise (S/N) ratio of 15. The combined and expanded uncertainties accompanying these measurements are 1.72% and 3.44%, respectively.