Results 1 - 10 of 19958
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[en] The genetic algorithm (GA) for simulation of the thermoluminescence (TL) mechanisms in solids was adapted. The realization of main evolutionary operators (selection, crossover and mutation) was carried out with using parameters of the known band schemes. The efficiency of the GA simulation was estimated taking non-interactive multitrap model as an example
[en] The thermally activated characteristics (TAC) of the linearly modulated optically stimulated luminescence (LM-OSL) signals of seven quartz samples from different origin were studied relative to the TAC of their respective thermoluminescence (TL) glow-peaks at 110 deg. C. Within the framework of the study the TAC behavior of the LM-OSL was investigated by measuring the OSL signal at room temperature (RT) with the 110 deg. C glow-peak present during OSL measurements, as well as, at 125 deg. C without the glow-peak at 110 deg. C removed by a cut-heat at 180 deg. C prior to OSL measurement. The LM-OSL curves were analyzed into individual components using a computerized deconvolution procedure. It was found that all individual LM-OSL components of each kind of quartz follow the TAC behavior of the respective TL glow-peak at 110 deg. C. The fourth component of the LM-OSL curve, centered at about tm=400s, appeared when the OSL measurements were performed at RT, whereas it was absent when the OSL measurement were performed at 180 deg. C. It is suggested that this component is closely related with the TL glow-peak at 110 deg. C
[en] Results from a study on the thermoluminescent (Tl) emission from Al2 O3:Cr,Ni are presented. The measurements were obtained for evaluation of the Al2 O3:Cr,Ni dosimetric properties. Different crystal batches were exposed to two kind of ionizing radiation (X-ray and β-). The Tl spectrum has a main peak with high thermal and optical stability, deviating from linearity for doses lower than 3.6 Gy. Furthermore, this material shows advantages (thermal resistance, reusability, multiple heating cycles) compared to TLD-100. Measured Al2 O3:Cr,Ni properties indicate that it could be used as a dosemeter. (author)
[en] The theory involved in the phenomenon of thermoluminescence emission, the characteristics of the main thermoluminescent phosphorus and some of their applications are presented. Some of the main thermoluminescent dosemeters used in dosimetry are described. (M.C.K.)
[pt]Apresentam-se a teoria envolvida no fenomeno da emissao termoluminescente, as caracteristicas dos principais fosforos termoluminescentes e algumas de suas aplicacoes. Descrevem-se alguns dos principais dosimetros termoluminescentes utilizados em dosimetria. (M.C.K.)
[en] We investigated the loss of sensitivity on Thermoluminescent Dosimeter (TLD)-700H(LiF: Mg, Cu, P) by Thermo Fisher Scientific at multiple read-irradiation cycles on two different TLD readers. Our test results suggest that the current Time Temperature Profile (TTP) with a maximum temperature of 260 °C overheats DT-702/PD’s thinnest chip 3 causing 29% ± 7.4% loss in sensitivity over 1000 cycles. For the other three elements, it is significantly less. A possible cause of this effect is overheating of element 3. Our results indicate that one possible solution is to modify TTP for all chips and decouple the TTP for chip 3. There is also significant variability ranging from 22% to 40% between different TLD’s and 8%–22% for different readers. Calibration cards undergo the highest number of heats and irradiation cycles because they are used to calibrate TLD’s and readers. The stability of calibration card’s sensitivity is critical to provide accurate dose of record. Any change in the calibration card element correction coefficient (ecc) is reflected immediately in calibration of other TLD’s and readers. A variety of processes have been implemented to control sensitivity of calibration cards. Proficiency and intercomparison results support the current operating policy and procedures to protect the accuracy and efficiency of our personnel dose program. Suggested TTP modification may reduce the loss of sensitivity for and may extend the life of calibration TLD’s to over 1000 heat cycles.
[en] This paper summarises recent developments in the Risoe TL/OSL reader. These new developments include an elevated temperature irradiation facility that has been expanded to measure variable temperature radioluminescence (RL) during beta irradiation. This RL facility allows the measurement of TL, OSL and RL in the same software-controlled automatic sequence. To provide an alternative to the 90Sr beta source, the performance of a software-controlled mini X-ray generator has been investigated. This has the advantage of providing a range of dose rates spanning more than three orders of magnitude up to more than 2 Gy/s. A separate bleaching facility has also been added to the reader, new powerful infrared (IR) light-emitting diodes have replaced the IR laser diode in the general OSL unit, and an IR laser has been included in the single-grain OSL attachment. This paper describes these new facilities, and illustrates their applications with representative measurements
[en] The models employed so far for deconvolving thermoluminescent glow curves are either derived by neglecting the interaction among traps and resorting to the quasi-equilibrium approximation, or are simply phenomenological. Several published articles have shown that the approximations are difficult to justify. Further it has never been shown that they are rigorously applicable to any known system. As to the phenomenological model it is no physically meaningful. An algorithm is reported which allows analyses of glow curves without the aforementioned approximations.