Thermoluminescent composites of sintered synthetic-topaz/in situ corundum for dosimetry by a novel reversible process.

Topaz (Al2F1·44(OH)0·56SiO4)/corundum (Al2O3) composites were prepared by a facile and novel reversible process from the sintering of synthetic topaz and AlF3 powders, with corundum formed in situ into the topaz matrix. The corundum formation reaction occurs in the temperature range 875-975 °C, from 40 min sintering time, obtaining the topaz- Al2F1·44(OH)0·56SiO4/corundum- Al2O3 composites. Although sintering temperature and time increment lead to higher corundum formation in the topaz matrix (78.4 wt % Al2O3 at 975 °C for 60 min), longer residence times give place to corundum percentage decrease due to topaz reconversion. The composites' microstructure is characterized by a rectangular bar with stacked pyramidal ends and polycrystals of hexagonal plates for topaz and corundum, respectively. For the topaz/corundum composites, the maximum density was 3.05 g/cm3 (17 % porosity) for specimens sintered at 925 °C for 20 min. The glow curves of the topaz/in situ corundum composite sintered at 975 °C and 0 min dwell time show thermoluminescent peaks between 180 and 250 °C, useful for dosimetric applications. The most helpful peak (at 221 °C) in the topaz/corundum composite's glow curves determined by computational deconvolution is sharp and exhibits the highest thermoluminescent response. Dose-response analysis of the composite (sintered at 975 °C for 0 min) with the best thermoluminescent response revealed two ranges of linear behavior, the first from 2 to 200 mGy, with an adjustment of 99.9 % and the second in the range 5-300 Gy (99.8 % fitting). The thermoluminescent response improvement of the topaz/corundum composites is attributed to the corundum formed in situ during sintering. Fading rate studies of the composite with the best sintering treatment revealed a signal decrease of 4 % after 15 days, which remained constant for up to 30 days, and 8 % after 60 days. The kinetic parameters, kinetics order (b), activation energy (E), and frequency factor (s) determined using the glow peak shape method showed second-order kinetics. The topaz/corundum composite with the best TL response (975 °C, 0 min) presents an effective atomic number (Zeff) of 11.74. The detection of lower doses (mGy) and the linear response at higher doses (Gy) of beta 90Sr, together with the other thermoluminescent properties, suggest that the topaz/corundum composites sintered at 975° for 0 min dwell time may find application in radiotherapy, geological dating, and environmental dosimetry.

Synthesis, RL and OSL characterization of thulium doped NaMgF3 neighborite.

The aim of this work is to study the dosimetric properties of tissue-equivalent thulium doped NaMgF3 neighborites and to determine their possible application as dosimeters in personal dosimetry. In this aspect, radioluminescence (RL) and optically stimulated luminescence (OSL) dosimetric properties of undoped and Tm3+ -doped NaMgF3 have been investigated for the first time. Samples were synthesized by solid state reaction and by considering a stoichiometric mixture of pure NaF and MgF2 reagents. Two emission peaks centered at 460 and 360 nm have been found in the RL emission spectrum of the doped samples, which can be ascribed to the 1D2 - 3F4 and 1D2 - 3H6 transitions of Tm3+ cations, respectively. Maximum OSL emission under blue light stimulation has been found for samples doped with 0.2 mol % of thulium. Furthermore, the OSL signal of this compound depends linearly on dose within the range 0.05-100 Gy. Besides, its OSL signal features satisfactory repeatability and a minimum detectable dose of 0.04 Gy. Finally, it has been found a low fading of the OSL signal of approximately 13% after the first 60 h, after which the OSL response remains constant. The obtained results suggest the feasibility of using this compound as an OSL detector in personal dosimetry.

Optically stimulated luminescence dosimetry performance of novel MgO-La(OH)3 phosphors.

The aim of this work was to study the optically stimulated luminescence (OSL) properties of novel MgO co-doped with different lanthanides and lithium ions as well as to evaluate the feasibility of using the mentioned phosphors as OSL dosimeters. In this context, the OSL efficiency corresponding to different stimulation wavelengths and different filters was analyzed for all the samples. The properties of the most efficient material, namely, MgO-La(OH)3, were further studied. Moreover, the repeatability and linearity of the OSL response, the fading of the OSL signal and the minimum detectable dose were investigated. Finally, feasibility of using these compounds in OSL dosimetry was assessed.

Thermo- radio- and optically stimulated luminescence of Ce-doped KYF4 single crystals.

The goals of this work are to determine the luminescence properties of KYF4 single crystals doped with different concentrations of Ce3+ ions and to evaluate their possible application as a detector of beta radiation. In particular, thermoluminiscence, radioluminiscence and optically stimulated luminescence properties of KYF4: Ce3+ exposed to beta radiation have been studied and very good dosimetric properties have been obtained within the dose range 0.02-20 Gy.

Optically stimulated luminescence of natural NaCl mineral from Dead Sea exposed to gamma radiation.

In this work, the continuous wave - optically stimulated luminescence (CW-OSL) emissions of natural salt minerals, collected from Dead Sea in summer of 2015, were studied. The CW-OSL dose response of natural salt showed a linear range between 0.5Gy and 10Gy of gamma radiation of 60Co. Samples exposed at 3Gy exhibited good repeatability with a variation coefficient of 4.6%. The CW-OSL response as function of the preheating temperature (50-250°C) was analyzed. An increase of 15% of the CW-OSL response was observed in NaCl samples during storage period of 336h. The results showed that the natural Dead Sea salt minerals could be applied as natural dosimeter of gamma radiation.

Synthesis and stimulated luminescence property of Zn(BO2)2:Tb3.

Zinc borate, Zn(BO2)2, doped with different concentrations of terbium (0.5-8mol%) was synthesized and polycrystalline samples were characterized by Scanning Electron Microscopy and X-Ray Diffraction. The Zn(BO2)2 was formed in the pure samples sintered at 750 and 800°C which has the body centered cubic structure, and a ZnB4O7 primitive orthorhombic phase was present. The thermoluminescent intensity was dependents on the thermal treatment (250-500°C) and also on the impurity concentration. The linear dose-response was obtained between 0.022-27.7Gy and 0.5-50Gy when the samples were exposed to beta and gamma radiation, respectively. The complex structure of the glow curves was analyzed by the Computerized Glow Curve Deconvolution method. The kinetics parameters were calculated assuming the general order kinetics model describing accurately the TL process. The glow curves of Tb3+-doped zinc borate phosphor were well deconvolved by six glow peaks. Zinc borate with 8mol% of impurity concentration exhibited an intense radioluminescent emission. The radioluminescent spectra show their maximum bands at 370, 490, 545 and 700nm related to the terbium ion in the zinc borate. These obtained results suggest that the terbium doped zinc borate is a promising phosphor for use in radiation dosimetry because of its high TL sensitivity to the ionizing radiation.

New algorithm for analyzing phosphorescence curves: Its application to the K2YF5:Pr compound.

Analysis of phosphorescence curves is an alternative procedure to glow curve analysis in order to find the parameters characterizing trap and recombination centers of thermoluminescence materials. In this article a new algorithm to analyze phosphorescence curves is reported, which is derived from the set of coupled differential equation describing the carrier traffic without resorting to approximations. The new algorithm has been employed to analyze the phosphorescence curves of the K2YF5:Pr compound.

Performance of ZnSe(Te) as fiberoptic dosimetry detector.

Fiberoptic dosimetry (FOD) is an experimental technique suitable for in-vivo, real time dosimetry in radiotherapy treatments. FOD relies on using a small scintillator coupled to one end of a long optical fiber. The scintillator is placed at the point where the dose rate is to be determined whereas a light detector at the other end of the fiber measures the intensity of the radioluminescence emitted by the scintillator. One of the problems hampering the straightforward application of this technique in clinics is the presence of Cherenkov radiation generated in the fiber by the ionizing radiation, which adds to the scintillating light and introduces a bias in the dose measurement. Since Cherenkov radiation is more important in short wavelength range of the visible spectrum, using red-emitting scintillators as FOD detectors permits to reduce the Cherenkov contribution by using optical filters. In this work, the performance of red-emitting tellurium-doped zinc selenide crystal as FOD detector is evaluated and compared to the response of an ion-chamber.

Photostimulated luminescence detection and radiation effects on cinnamon (Cinnamomum zeylanicum) spice.

The increase of disease borne pathogens in foods has promoted the use of new technologies in order to eliminate these pathogen microorganisms and extend the shelf-life of the foodstuffs. In particular, Cinnamon (Cinnamomum zeylanicum) contains an important number of pathogen microorganisms and it is frequently sterilized by gamma radiation. However, it is important to develop the detection methods for irradiated food in order to keep the dose control and also to analyze the radiation effects in their chemical property. This work reports (i) the photostimulated luminescence (PSL) detection of irradiated cinnamon and thermoluminescence (TL) detection of the inorganic polymineral fraction separated from this spice, and (ii) the proximate chemical analysis carried out on fat, protein and dietetic fiber contents. The detection limits using the PSL and TL methods were 500 Gy and 10 Gy, respectively, and the fat content was increased significantly with the gamma dose that could be related to the lipid oxidation in the cinnamon.

Luminescence detection and dose assessment of irradiated Yerba Mate (Ilex paraguariensis) tea leaves.

Imported commercial samples of Yerba Mate (Ilex paraguariensis) tea leaves were characterized by thermoluminescence (TL) and photoluminescence (PSL) physical methods. Samples of Yerba Mate were irradiated between 0.5-50Gy and 20Gy-5kGy gamma doses by using two different dose rates from (60)Co irradiators. The Electron Dispersive Analysis (EDS) shows that the inorganic fraction is mainly composed by quartz and Ca-feldspars minerals. These polyminerals show a good sensitivity to gamma radiation and to UV light (530nm). Linear dose-response curves were obtained between 0.5 and 12Gy at low dose-rate, and with 20 to 500Gy at high dose-rate of gamma radiation. At higher doses (600Gy) an apparent slow saturation effect was observed. Low fading of the TL signal was found. The detection limits of TL and PSL are 6Gy and 300Gy, respectively. Results show that luminescence emission (TL and PSL) is a reliable method for detection of irradiation Yerba Mate.

Determination of kinetics parameters of the main glow peaks for KMgF3:Lu and LiF:Mg phosphors after long-term high temperature storage.

The isothermal decay method is useful for determining the trap activation energy in thermoluminescent material for dosimetry purposes. Recently we proposed new modified expressions for isothermal decay method. As validation of the modified expressions, after long-term (4 h) high temperature storage, the activation energy of experimental TL glow peaks, KMgF3:Lu (0.17 and 0.34 mol%) and LiF:Mg (0.04 mol%), in the framework of the general-order kinetic was calculated. The results of the kinetics parameters were compared with those obtained by the other methods like Initial Rise (IR), Sequential Quadratic Programming Glow Curve Deconvolution (SQPGCD), deconvolution of the TL glow curves by assuming the General Order Kinetic (GOK), and Chen General-Order Kinetics method. It seems that both SQPGCD and GOK deconvolution methods give more accurate kinetics parameters values for the experimental glow curves.

Analysis of the main dosimetric peak of Al2O3:C compounds with a model of interacting traps.

The glow curve of Al2O3:C compounds has been analyzed by employing a model consisting of two active traps, thermally disconnected traps and one recombination centre. The analysis takes into account interaction among traps and the thermal quenching of the thermoluminescent emission.

Thermoluminescence study of polyminerals extracted from clove and marjoram for detection purposes.

Food irradiation is a widely employed technology for food treatment. Since in several countries no regulations prevail, it is difficult to detect whether food has been irradiated or not. Among different analytical methods the study of the thermoluminescent (TL) emission of polymineral extracted from food is one of the most useful physical identification method. The aim of this work is to analyze the TL properties of inorganic polyminerals extracted from commercial clove (Syzygium aromaticum L.) and marjoram (Origanum majorana L.) spices exposed to (60)Co gamma radiation for detection purposes. The feasibility of using the TL method for irradiated food detection and absorbed dose determination is assessed.

Thermoluminescence analysis of irradiated oyster shells.

This paper reports the thermoluminescence (TL) analysis performed on the oyster shells powder. TL response of (60)Co gamma-rays irradiated samples were studied in the range from 80 Gy to 8 kGy doses. TL signal of irradiated shell powder was higher as compared to the unirradiated control samples, which allowed to identify the irradiated oysters. Results show that the oyster shells have good TL properties and can be useful for the identification of irradiated seafood as well as for the evaluation of the treatment dose.

Radioluminescence of red-emitting Eu-doped phosphors for fiberoptic dosimetry.

Fiberoptic dosimetry (FOD) technique has become an attractive method for real-time dosimetry. Al(2)O(3):Cis one of the most used radioluminescence materials for FOD due to its high efficiency but it presents the drawback of emitting in the spectral region, where spurious luminescence is also important. Optical filtering is the simplest technique to remove spurious luminescence, but is useful when red-emitting scintillators are employed. In this work, the feasibility of using red-emitting Eu-doped phosphors as FOD scintillators has been investigated.