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Thermoluminescence of single wall carbon nanotubes synthesized by hydrogen-arc-discharge method
摘要： Single Wall Carbon Nanotubes (SWNT) synthesized by the hydrogen-arc-discharge method were tested as thermoluminescent (TL) material and found to be highly resistant to gamma radiation. Gamma irradiation of the as-prepared material with doses between 1 and 20 kGy induced changes on the morphology of the SWNT, such as nanoloops, as observed by Scanning Electron Microscopy. From X-ray diffraction, the as-prepared material shows content of various forms of carbon, including nanotubes, hexagonal carbon (graphite), and rhombohedral carbon too. The full width at half maximum (FWHM) of diffraction peaks remain practically unchanged after irradiation. The glow curves show a single TL peak centered at about 449 K. Because the complex structure of the glow curves, it seems that the TL signal could be produced by a trap distribution instead of a single level of traps. To dilucidate the mechanism responsible of glow curves and the value of activation energy of traps, kinetic parameters like Eeff, ?E, and s of experimental the glow curves have been analyzed using computerized glow curve deconvolution (CGCD) considering a continuous distribution of trapping levels, peak shape and initial rise methods, as well as heuristic equations. The measured TL dosimetric properties may be summarized as follows: (a) moderate reproducibility of the TL signal (coefficient of variation 24.87%); (b) main peak activation energy of 1.206 eV; (c) threshold dose of ~1 kGy; (d) TL-sensitivity of ~7.0x10-4; (e) human bone equivalence, i.e., high-Z material, Zeff =15 and, (f) wide linear range of TL dose-response in the range 0.170–2.5 kGy.
关键词： Radiation effects,kinetic property,thermoluminescence,carbon nanotubes,dosimetric material
更新于2025-09-23 15:21:01
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Photoluminescent and thermoluminescent properties of low temperature synthesized Nd3+ doped Mg2SiO4 nanophosphors for display and dosimetry applications
摘要： A potential green emitting orthorhombic Mg2SiO4:Nd3+ (1- 9 mol %) nanophosphors were synthesized by low temperature (350 oC) solution combustion technique. The characteristic PL emission peaks at ~ 458 nm (2G9/2 →4I9/2) and ~ 518 nm (4G5/2+2G7/2→4I9/2) were recorded upon 420 nm excitation and maximum intensity was observed for 3 mol % Nd3+ doped samples. The optimised sample exhibit CIE coordinates (0.1667, 0.4336) in green region with quantum efficiency of 65 %. The latent fingerprint detection analysis was carried out using optimised sample on versatile surfaces. The thermoluminescence studies of the γ- irradiated (1- 5 kGy) Mg2SiO4:Nd3+ (3 mol %) samples was studied with heating rate of 5 oCs-1. The TL glow peak was observed at 160 oC. The estimated trap parameters (b, E, s) by standard methods were reported. The obtained results from photoluminescence, fingerprint detection analysis and thermoluminescence properties suggest that the optimised phosphor could be a candidate for WLEDs, forensic and dosimetry applications.
关键词： Mg2SiO4:Nd3+,Photoluminescence,Thermoluminescence
更新于2025-09-23 15:21:01
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Recent Advances in Silica Glass Optical Fiber for Dosimetry Applications
摘要： In this paper, we review the highly promising silica glass, fabricated as doped and undoped optical fiber for intended use in radiation dosimetry. The dosimetry techniques reviewed here, underpinned by intrinsic and extrinsic defects in silica glass, focus on Thermoluminescence (TL), Optically Stimulated Luminescence (OSL) and Radioluminescence (RL), with occasional references to the much more established Radiation Induced Attenuation (RIA). The other focus in this review is on the various materials that have been reported earlier as dopants and modifiers used in silica glass optical fiber radiation dosimeters. This article also elaborates on recently reported optical fiber structures, namely, cylindrical fibers, photonic crystal fibers and flat fibers, as well as dimensions and shapes used for optimization of dosimeter performance. The various types of optical fiber radiation dosimeters are subsequently reviewed for various applications ranging from medical dosimetry such as in external beam radiotherapy, brachytherapy and diagnostic imaging, as well as in industrial processing and space dosimetry covering a dynamic dose range from μGy to kGy. Investigated dosimetric characteristics include reproducibility, fading, dose response, reciprocity between luminescence yield to dose-rate and energy dependence. The review is completed by a brief discussion on limitations and future developments in optical fiber radiation dosimetry.
关键词： radioluminescence,thermoluminescence,Silica optical fiber,review,dosimetry
更新于2025-09-23 15:19:57
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Lanthanide-doped MgO: A case study on how to design new phosphors for dosimetry with tailored luminescent properties
摘要： In this work we systematically investigated undoped and lanthanide(Ln)-doped MgO with diverse dopant combinations, MgO:Ce,Ln and MgO:Tb,Ln, where Ln=Eu, Yb, Tm, Sm, Dy, Nd, as well as the same combinations with an additional 3 mol% Li dopant. We characterized the thermoluminescence (TL), optically stimulated luminescence (OSL), radioluminescence (RL), TL emission spectra and OSL emission spectra. Our investigation indicates that Ce3+ and Tb3+ act as recombination centers and their characteristic spectra are observed under thermal or optical stimulation. Conversely, TL measurements suggests that Sm3+, Tm3+ and Yb3+ probably act as electrons traps. The role of Li was investigated, since it was found to increase the RL, TL and OSL intensities in MgO. As part of the present investigation, we identified promising OSL materials sensitive to ionizing irradiation with distinct luminescent properties.
关键词： Optically stimulated luminescence,Dosimetry,Thermoluminescence,Lanthanides
更新于2025-09-19 17:15:36
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Studies on pelletized lithium magnesium borate TL material for eye lens dosimetry
摘要： Recent epidemiological studies in various cohorts confirm that radiation induced cataract may occur at a threshold dose as low as 0.5 Gy. ICRP has recognized the higher radiosensitivity of eye lens and recommended to reduce annual eye lens dose limit from 150 mSv to 20 mSv. Present dosimetry for eye lens is largely based on LiF based dosimeters. The present work is an attempt towards using near tissue equivalent lithium borate material namely lithium magnesium borate doped with terbium (LMB:Tb) in eye lens dosimetry. The material in powder form was synthesized using solid state sintering method and pelletized using poly tetra fluoro ethylene (PTFE) as binding agent. It was observed that 130 mg of 1mm thick LMB:Tb pellet bound with PTFE showed stable glow curve structure and attractive dosimetric features in terms of sensitivity, fading, linearity, reusability etc. A proposal of 1.5 mm Teflon encapsulation corresponding to tissue equivalent thickness of 3 mm was put forward for an ideal dosimeter for the measurement in terms of Hp(3). Energy and angular dependence studies based on FLUKA simulations suggest a flat response for the prototype design. In addition to PTFE, various tissue equivalent encapsulations such as polyimide, polyamide 6 and PMMA were also evaluated using FLUKA code.
关键词： thermoluminescence,Eye lens dosimetry,lithium borate phosphor
更新于2025-09-19 17:15:36
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Structural, morphological and 6 MeV energy electron dosimetric properties of Cu doped SnO<sub>2</sub> phosphor.
摘要： Cu doped SnO2 (SnO2:Cu) nano phosphor (NP) was successfully synthesized by one-step simple hydrothermal method and it was characterized by XRD (X-Ray Diffraction) for structural, FESEM (Field Emission Scanning Electron Microscopy) for morphological and EDS (Electron Dispersive Spectroscopy) for elemental analysis. NP was annealed at 700 °C for 2 hr and its crystallinity for tetragonal phase was confirmed through XRD. The crystallite size was ~10.39 nm for un-annealed and ~18.16 nm for annealed samples which has been calculated using Scherer equation. The particle size was estimated to be ~43 nm and the elemental composition of Sn, O, Cu was obtained by EDS. In addition, to study the dosimetric properties, the SnO2:Cu phosphors were irradiated with 6 MeV electron beam at fluences ranging from 10 x 10^11 e/cm^2 to 20 x 10^12 e/cm^2 which is equivalent to the 1.55 kGy to 31 kGy. The irradiated sample showed Thermoluminescence (TL) dosimetric glow peaks at 170 °C, 263 °C and 303 °C. SnO2:Cu NP was found to be sensitive enough for energetic electrons. Further, it has been noticed that the TL dose response found sensitive upto 10 x 10^12 e/cm^2 (15.50 kGy) with fading of 5.1 % for 2 months. Hence, SnO2:Cu can be used for the measurement of electron doses.
关键词： Hydrothermal Method,Electron Irradiation,Thermoluminescence,SnO2
更新于2025-09-19 17:15:36
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The RbSr <sup>2</sup> Σ <sup>+</sup> ground state investigated <i>via</i> spectroscopy of hot and ultracold molecules
摘要： We report on spectroscopic studies of hot and ultracold RbSr molecules, and combine the results in an analysis that allows us to fit a potential energy curve (PEC) for the X(1)2S+ ground state bridging the short-to-long-range domains. The ultracold RbSr molecules are created in a mK sample of Rb and Sr atoms and probed by two-colour photoassociation spectroscopy. The data yield the long-range dispersion coefficients C6 and C8, along with the total number of supported bound levels. The hot RbSr molecules are created in a 1000 K gas mixture of Rb and Sr in a heat-pipe oven and probed by thermoluminescence and laser-induced fluorescence spectroscopy. We compare the hot molecule data with spectra we simulated using previously published PECs determined by three different ab initio theoretical methods. We identify several band heads corresponding to radiative decay from the B(2)2S+ state to the deepest bound levels of X(1)2S+. We determine a mass-scaled high-precision model for X(1)2S+ by fitting all data using a single fit procedure. The corresponding PEC is consistent with all data, thus spanning short-to-long internuclear distances and bridging an energy gap of about 75% of the potential well depth, still uncharted by any experiment. We benchmark previous ab initio PECs against our results, and give the PEC fit parameters for both X(1)2S+ and B(2)2S+ states. As first outcomes of our analysis, we calculate the s-wave scattering properties for all stable isotopic combinations and corroborate the locations of Fano–Feshbach resonances between alkali Rb and closed-shell Sr atoms recently observed [V. Barbé et al., Nat. Phys., 2018, 14, 881]. These results and more generally our strategy should greatly contribute to the generation of ultracold alkali–alkaline-earth dimers, whose applications range from quantum simulation to state-controlled quantum chemistry.
关键词： spectroscopy,laser-induced fluorescence,thermoluminescence,ultracold molecules,photoassociation,potential energy curve,Fano-Feshbach resonances,RbSr molecules
更新于2025-09-19 17:15:36
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Predicting the afterglow duration in persistent phosphors: a validated approach to derive trap depth distributions
摘要： Persistent phosphors are increasingly investigated due to their potential applications in various fields, such as safety signage, dosimetry and in vivo imaging. These materials act as optical batteries that store and gradually release energy supplied during optical charging. As the energy is stored, or ‘trapped’, at specific defect sites in the host lattice, a clear understanding of the defects and trapping mechanisms in these materials is important for systematic improvement of their properties. Here, the thermoluminescence and afterglow properties of the near-infrared (NIR) emitting persistent phosphor LiGa5O8:Cr3+ (LGO:Cr) are studied. This phosphor is used as a model system for illustrating a more general approach to reliably derive trap depth distributions in persistent luminescent and storage materials. The combination of the Tstop–Tmax method with initial rise analysis is used to experimentally determine the presence of a broad distribution of trapping states. Computerized glow curve fitting is subsequently used to extract the relevant trapping parameters of the system in a rigorous, consistent manner, by fitting all the experimentally recorded data simultaneously. The resulting, single set of model parameters is able to describe all measured thermoluminescence and afterglow data and hence can be used to predict afterglow and storage properties of the phosphor under various conditions. The methods to analyze and describe the trap structure of the persistent phosphor LGO:Cr are straightforwardly applicable for other persistent and storage phosphors and result in a reliable determination of the relevant trapping parameters of a given material.
关键词： thermoluminescence,afterglow,persistent phosphors,LiGa5O8:Cr3+,trap depth distributions
更新于2025-09-19 17:15:36
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The photoluminescence and thermoluminescence characteristics of the Eu3+ doped CaMoO4: Detailed kinetic analysis of TL glow curves
摘要： Ca1-xMoO4:xEu3t (x varies from 0.02 to 0.07) phosphors were prepared via complex polymerization method (CPM). It was determined that CaMoO4:Eu3t has powellite crystal structure with space group ??41/?? (No.88). The cell parameters are ?? ? ?? ? 5.217 ? and ?? ? 11.414 ?. The intense bands observed in the excitation spectrum of Ca0.95MoO4:0.05Eu3t at 240 nm and 281 nm belong to the charge transfer transition in O2(cid:0) → Mo6t and O2(cid:0) → Eu3t groups and these bands overlap with each other. Aside from these bands, five other bands were observed in the excitation spectrum between 350 and 500 nm that belong to 7F0→5D4, 7F0→5G4, 7F0→5L6, 7F0→5D2, 7F0→5D2 electronic transitions of Eu3t ions. The emission spectrum of Ca0.95MoO4:0.05Eu3t exhibits a series of emission bands between 550 nm and 750 nm that can be attributed to the 5D0→7Fj (j ? 0–4) transitions of Eu3t ions. The thermoluminescence properties of Ca0.95MoO4:0.05Eu3t were investigated in detail and the glow curves were analyzed via glow curve deconvolution (GCD) method. The results showed that Ca0.95MoO4:0.05Eu3t was composed of four general order TL glow peaks. The f(D) function was investigated at a heating rate of 1 ?C/s and the linear (f(D) ? 1) behavior of the curves at very low doses was found to be followed by a supralinear (f(D) > 1) behavior up to nearly 102 Gy.
关键词： Photoluminescence,CaMoO4 phosphor,Thermoluminescence,Molybdates
更新于2025-09-16 10:30:52
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Phototransferred thermoluminescence of annealed synthetic quartz: Analysis of illumination-time profiles, kinetics and competition effects
摘要： Phototransferred thermoluminescence (PTTL) induced from annealed synthetic quartz using 470 nm blue light is reported. The quartz was annealed at 900oC for 10, 30 and 60 minutes prior to use. A glow curve of conventional TL measured at 1oC s-1 following irradiation to 200 Gy for the sample annealed for 10 minutes shows six peaks at 90, 122, 176, 210, 240 and 340oC. The sample annealed for 30 minutes has peaks at 80, 110, 136, 196, 240 and 330oC. Similarly, the sample annealed for 60 minutes also has six peaks at 80, 120, 134, 188, 235 and 340oC. For ease of reference, these are labelled I-VI respectively. Peaks observed under PTTL are referred to as A1 onwards. Of the six peaks, only the first three are reproduced under phototransfer for the sample annealed for 60 minutes. When the duration of annealing was reduced to 10 minutes, PTTL is induced only at peaks A1 and A3. Interestingly, for the intermediate duration of annealing of 30 minutes, the only peak that appears under phototransfer is the first one, A1. For quartz annealed for 10 minutes, the PTTL appears as long as the preheating temperature does not exceed 560oC. On the other hand, in the quartz annealed for 30 and 60 minutes, PTTL only appears for preheating to and below 450oC. This shows that the occupancy of deep electron traps at temperatures beyond 450 or 560oC is low in the said samples. The activation energy for peaks A1 and A3 was found to be about 0.68 eV. The PTTL peaks were studied for thermal quenching and peaks A1 and A3 were determined to be subject to this effect. The activation energy for thermal quenching was determined as 0.62 ± 0.04 eV in analysis using peak A1. In all cases, the PTTL intensity goes through a peak as a function of illumination time. The experimental dependence of PTTL intensity on illumination time is modelled using sets of coupled linear differential equations based on systems of donors and acceptors whose number is determined by preheating temperature. Competition effects involved in the PTTL have been discussed.
关键词： competition effects,phototransferred thermoluminescence,synthetic quartz,Annealing,thermal quenching
更新于2025-09-12 10:27:22