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摘要
This study explores the potential for using photon-stimulated luminescence of quartz grains to retrospectively evaluate multi-kGy gamma radiation doses. Subsamples from two ceramic tiles were given (60)Co gamma doses of 1, 3, 5, 15 and 30 kGy (nominal), accompanied by PMMA dosimeters and quartz grains from a geological sample known to exhibit thermally-transferred optically-stimulated luminescence (TTOSL). Following gamma irradiation, quartz grains were prepared from each subsample. OSL and TTOSL signals were measured for different preheat temperatures, and following re-irradiation with beta doses designed to equal the nominal gamma doses. OSL responses to 10 Gy beta test doses were measured following each cycle of high dose irradiation. Gamma doses were predicted from the beta responses, to evaluate the effectiveness of retrospective dose evaluation for different signal integrals, preheat combinations, and dose intervals. The use of linear modulation limited maximum OSL signal levels to 1.5 x 10(6) cps without reducing detector sensitivity, for the measurement of smaller TTOSL signals. The dosimetric behaviour of the three samples differed significantly: the best results were obtained from the pre-prepared geological quartz. OSL signals evident at short stimulation times, which are conventionally used for dosimetry and dating, did not in general appear appropriate for dosimetiy in the range of doses examined. They exhibited dose response characteristics that were highly preheat dependant and variable in form between samples, which contained rapidly saturating and/or non-monotonic components. Higher preheats, up to 300 degrees C, preferentially removed OSL and TTOSL signals evident at longer stimulation times: those that remained yielded growth in signal with dose to approximately 10 kGy, but the accuracy of retrospective dose determinations was variable. TTOSL signals evident at short stimulation times increased proportionally with dose when 300 degrees C preheats were used, up to 30 kGy of beta irradiation for two of the samples, but the given gamma doses were underestimated by 15-23%. Refinement of the present measurement protocol may improve assessment of the gamma doses, and the short term stability of the signal needs to be characterised, but the observed level of accuracy is already sufficient to provide approximate estimates for severity of radiation exposure. The present study has identified certain elements of OSL and TTOSL signals that can be used, in combination with a relatively severe preheating regime, to retrospectively evaluate doses of tens of kGy: beyond the range traditionally possible using quartz.
- 出版日期2011-9
