Inter-comparison study between human and cow teeth enamel for low dose measurement using ESR

Human and cow teeth enamel samples were separated and irradiated with gamma-ray to study radiation-induced radicals as dosimetric material with electron spin resonance (ESR). The enamel spectrum is characterized by two main g-factors g parallel to = 1.9976 and g perpendicular to = 2.0019. The dosimetric signal for enamel at g = 2.0019 is ascribed to CO(2)(-) radicals. The dose response was studied in the range from 200 mGy to 2 Gy. Power dependence, energy dependence and thermal stability had been studied also to determine the optimum conditions for ESR measurements and stability of the signal at room temperature as well. Radical formation efficiency (G-value) of 0.44 +/- 0.09 and 0.65 +/- 0.13 was obtained for human enamel and cow enamel, respectively. The life time for human enamel and cow enamel were estimated from Arrhenius plot to be 1.1 x 10(7) years and 7 x 10(6) years, respectively. The activation energy for human enamel and cow enamel were also calculated from Arrhenius plot to be 1.23 eV and 1.15 eV, respectively. The dose conversion factors for enamel in water and air were calculated to be 0.901 D(water) and 0.998 D(air). The combined and expanded uncertainties accompanying these measurements are +/- 5.79% and +/- 11.58%, respectively. (C) 2010 Elsevier B.V. All rights reserved.