Browsing by Subject "Fluorspar"

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    Thermoluminescence response of CaF2:Dy as a function of irradiation temperature between room temperature and 270 °C
    (Elsevier Ltd, 2018) Karsu Asal E.C.; Polymeris G.S.; Kitis G.
    The Themoluminescence (TL) response of CaF2:Dy (TLD-200) as a function of irradiation temperature was studied in the present work. The irradiation of a TL material at elevated temperatures has a twofold scope: (a) To provide knowledge and insight regarding the possibilities of radiation dosimetry at high temperature environments; (b) The fact that during irradiation at elevated temperatures trap filling and trap emptying take place simultaneously, makes this pre-conditioning the most promising for the reflection in the net glow-curve of competition effects between traps and centres. The irradiation temperature (Tirr) region was between room temperature (RT) and 270 °C in steps of 10 °C. Using the same conditions as far as dose and temperature are concerned, post irradiation annealing (PIA) measurements were also performed, which give only the results of trap emptying. Both experiments were performed using (a) one sample for all measurements (single-aliquot procedure) and (b) two samples for each temperature (multi-aliquot procedure). Deconvolution was also applied in all cases towards investigating the impact of the two protocols on the kinetic parameters of all peaks for this specific material. The results showed that there is not any dependence of the TL response in the case of multi-aliquot procedure. However, in the case of single-aliquot procedure, a very interesting dependence of the TL response on Tirr is observed only for the last TL peak of TLD-200. These results, although weaker, were also observed in the case of PIA procedure. Activation energies of the high-temperature, more stable peaks yield a dependence on both irradiation and PIA temperatures. The results are discussed in the framework of the trap competition models. © 2018
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    Thermoluminescence glow-curve deconvolution using analytical expressions: A unified presentation
    (Elsevier Ltd, 2021) Peng J.; Kitis G.; Sadek A.M.; Karsu Asal E.C.; Li Z.
    This study provides a unified presentation of thermoluminescence (TL) glow-curve deconvolution within the framework of the open source R package “tgcd”, according to various analytical expressions that describe first-, second-, general-, and mixed-order kinetics as well as the recently developed semi-analytical expressions that derive from the one trap-one recombination center (OTOR) model that utilizes the Lambert W function or the Wright Omega function. We provide a comprehensive, flexible, convenient, and openly accessible program to analyze TL glow curves according to different models and expressions. The consistency of kinetic parameters determined using different model expressions was assessed using measured TL glow curve of CaF2:Dy. The performance of the computerized glow curve deconvolution (CGCD) method was also tested using simulated glow curves. Results revealed the benefits of comparing kinetic parameters determined from different model expressions and those obtained using experimental TL evaluation methods to assess the reliability of deconvolution results. The accuracy of the CGCD method is dependent upon both the model expressions used and the intrinsic trapping parameters of the TL material. © 2020 Elsevier Ltd
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    Thermoluminescence of Ce and Nd co-doped CaF2 phosphors after beta irradiation
    (Elsevier B.V., 2021) Yazan H.; Portakal-Uçar Z.G.; Akça S.; Topaksu M.; Townsend P.D.; Can N.
    In this study, we have synthesized CaF2:Nd3+,Ce3+ phosphors by solid state reaction method. The thermoluminescence (TL) properties of the family of synthesized phosphors (CaF2:Ce3+ and CaF2:Ce3+,Nd3+) were investigated using a combination of a SCHOTT BG39 and HC414/46 filters. This gave the highest TL intensity of each phosphor after 10 Gy β-irradiation. Two TL glow peaks of CaF2:Nd3+,Ce3+ phosphor are centered at around 90 and 265 °C (with a heating rate of 2 °Cs−1). The glow peaks displayed a linear dose response in the range of 0.1–50 Gy. Various heating rates (VHR) were performed between 0.5 and 10 °Cs−1. It was seen that the TL intensity at 90 °C decreases and peak maximum temperature shifts to higher temperatures with an increasing heating rate. The TL intensity of the glow peak located at 265 °C increases with heating rate. The initial rise (IR) applied after TM–Tstop experiment and computerized glow curve deconvolution (CGCD) methods in addition to the VHR method on the glow curves of CaF2:Nd3+,Ce3+ phosphor were used to determine the number of peaks, the order of kinetics (b), activation energy (E) and frequency factor (s). The response of TL glow curves remained constant within ±2% deviation from the initial value after 10 cycles of reuse. © 2021 Elsevier B.V.