Study of Combinations of TL/OSL Single Dosimeters for Mixed High/Low Ionization Density Radiation Fields

摘要

We have previously demonstrated that the increased response of optically stimulated luminescence (OSL) compared to thermoluminescence (TL) following high ionization density (HID) alpha irradiation is naturally explained via the identification of OSL with the "two-hit" F2 or F3~+ center, whereas the major component of composite TL glow peak 5 is believed to arise from a "one-hit" complex defect. This discovery suggested that near-total discrimination between HID radiation and low ionization density (LID) radiation using combined OSL and TL measurements may have significant potential in mixed-field radiation dosimetry In this paper we discuss and compare the potential application of combinedOSL/TL measurements using ~6LiF:Mg,Ti (TLD-600) or~7LiF:Mg,Ti ( TLD-700) and TLD-100 natural isotopic composition) detectors.The signal from the dosimeter is given by S_(TL) = a·D_n + b·D_γ S_(OSL)= c·D_n + d·D_γ where S_(TL) and S_(OSL) are the signal intensities for the TL/OSL and D_n and D_γ are the values of the dose deposited in the detector by the neutron (alpha particles) and gamma ray components of the radiation field respectively and a,b,c,d are appropriate calibration constants.Because b/a is a measure of the accuracy of the measurement of γ dose via TL and c/d is a measure of the neutron dose via OSL we can establish the figure of merit (FOM) as:FOM = (c/d)x(b/a).Beta and alpha particle irradiations were carried out with ~(90)Sr/~(90)Y (~500 keV average energy) and ~(241)Am sources (4.7 MeV) respectively and neutron irradiations were carried out at the PTB (Germany) (E_n = 5 MeV) and RARAF (Columbia University, USA) (E_n = 6 MeV) accelerator facilities. The highest values of the FOM obtained was ~30 for neutron/gamma discrimination and ~110 for alpha/gamma discrimination using OSL/TL - peak 5 measurements in TLD-700.