Experimental photon energy response of different dosimetric materials for a dual detector system combining thermoluminescence and optically stimulated luminescence

Abstract

Precise knowledge of the energy response of radiation detector materials is necessary for accurate dose measurements, because the usual TL and OSL material response relative to the medium of interest (air, water or tissue) varies with beam energy. in this work, we experimentally evaluated the photon energy dependence of different materials used as detectors (Al2O3:C Luxel, BeO Thermalox 995, LiF:Mg,Ti-TLD100 and Brazilian pellets based on CaSO4:Dy and CaF2:natural) in personal dosimetry through OSL and techniques, using optimized readout parameters for each material and radiation qualities similar to real situations of exposure. It is well known that depending on the material's effective atomic number and type of stimulation, the photon energy response can present either an under-response relative to air in the low energy range, as is the case of BeO, or a large over-response, as Al2O3, CaSO4 and CaF2, or even a very fiatresponse, as LiF. By utilizing intrinsic characteristics of these materials combined with OSL and TL techniques, we evaluated ratios of relative photon energy responses between pairs of OSL (OSLD) and TL(TLD) detectors. We have noted that for all combinations of materials (Al2O3/LiF, CaSO4/BeO, and CaF2/BeO), the ratio of energy responses of each pair did not change significantly with energy in the intervals below 50 or above 300 keV. On the other hand, in the range of energies between 50 and 300 keV, there was a strong change in the ratio values, indicating that the ratio of detector responses well-discriminates the incident photon energy. By using these outcomes, it was possible to apply dose corrections with respect to energy using ratios of OSL and TL signals of dosimeters exposed to unknown radiation beam qualities and to determine doses in a blind test. Our results point out that this methodology could be employed to correct photon energy responses of a personal dosimeter based on both OSL and TL techniques. OSL advantages (fast readout, possibility of various partial readings and of determining accumulated doses) would be associated with the TL ones (large variety of dosimeters commercially available and use of glow curve as a readout quality control) in a dual detector system capable of determining photon energy and dose, without using attenuation filters. This new methodology might improve dose evaluation in personal dosimetry. (C) 2014 Elsevier B.V. All rights reserved.