Thermoluminescence Response Research Articles

Rare Earth Dy3+ Activated MgSrAl10O17 Phosphors for Luminescence

MgSrAl10O17:xDy3+ nanophosphors were fabricated by combustion method for different concentrations (x = 0, 0.0005, 0.001, 0.005, 0.01 and 0.02 mol) of Dysprosium (Dy). The synthesized nanophosphors were characterized by XRD, SEM, TEM, FTIR, PL and TL. The XRD (X-ray diffraction) showed crystalline hexagonal structure with preferred orientation of (107) plane. SEM (Scanning electron microscope) result shows the formation of nanosheets in irregular shape. TEM (transmission electron microscope) study revealed the nanoparticles within average diameter size of 30 nm. The FTIR ( fourier transform infrared spectrum) shows absorption peaks in numerous regions. TL (thermo-luminescence) properties included TL glow curves and TL response for different concentrations of Dy after exposure of 700 Gy gamma rays. TL intensity was found to increase with increase in concentration of dopant Dy and was found to show best result for x=0.02. Further PL (photoluminescence) characterization ofMgSrAl10O17:0.02 Dy3+ phosphor exhibits two main emission peaks at 484 and 575 nm due to Dy3+ ion, when excited with 350 nm wavelength.

Investigation by Thermoluminescence of the Ionization and Annealing Processes in Irradiated Ge-Doped Silica Fiber Preform

Germano-silicate fibers, mostly employed for telecom applications, are also implemented in radiation environments for data links or sensing. In this field, the understanding of radiation-induced mechanisms leading to the degradation of the performances of silica optical fibers has an essential role. Particularly, the estimation of the activation energies of the density of trapped states (DOTSs) governing the radiation-induced attenuation (RIA) is of primary importance. To investigate these mechanisms, the thermoluminescence (TL) is a powerful technique, by which the extrapolation of DOTSs has been previously largely achieved for pure and Al-, P-, Er-, and Yb-doped silica. Despite the key applications related to Ge-doped silica, one cannot do the same for this kind of fiber, due to an “anomalous” increase of their TL response along with the heating rate. The objective of this work is primarily to elucidate the specific radiation-induced mechanisms associated with the presence of Ge in silica that notably induce the anomalous TL response. We show from the experimental study of the RIA thermal annealing during the TL readout, and its correlation with the TL glow curve, that oxygen-deficient centers (ODCs) centers, trapping electrons during irradiation, form deep states which act as recombination center (RC) in the TL process. Finally, and most important, we propose a model that explains the TL anomalous features and how they are arisen from two specific properties of the annealing processes of Ge-related radiation-induced centers.

Synthesis and Thermoluminescence of Novel Ag3PO4:Ba2+ Nanophosphor as Gamma Radiations Detector

Ba2+ activated Ag3PO4 (APB6) orthophosphate as novel synthetic nanophosphor material were prepared using different impurity concentrations (1, 3, 5, 6 and 7 wt%) of BaCl2 salt. Coprecipitation method was used in preparation. The prepared nanophosphors were characterized via X-Ray Diffraction (XRD) and High-Resolution Transmission Electron Microscopy (HR-TEM) and the results confirmed the existence of nanoparticles. The thermoluminescence (TL) properties of the samples were extensively studied, where the APB6 sample with 6 wt% Ba2+ showed considerable TL characteristics. All the studied samples were subjected to optimum thermal annealing of 500oC for 1h and a heating rate of 5oC/s was applied. The TL response of APB6 nanophosphor exhibited the highest value in comparison with that of other compositions. In addition, APB6 sample revealed a good linearity of TL response within the gamma rat doses between 15 and 100 Gy, where a linear response is obtained with .0.9925 correlation coefficient. It also showed relationally low rate of fading of about 26% within a 50 days of storage. These good characteristics make the new prepared APB6 phosphor to be highly considered as a new potential TL dosimeter and can efficiently be used as γ-irradiation detector in many applications of ionizing radiation.

Comparison and Correction of Thermo-Luminescent Responses in Different Neutron Fields

Introduction: Neutron dosimetry is a challenging subject in radiation protection. Responses of neutron dosimeters mostly depend on the neutron energy spectrum. Dosimeter response corresponding to a dose-equivalent in the calibration field is different from responses in other neutron fields. Consequently, the dose estimated by neutron dosimeters may be associated with great uncertainty. Therefore, the present study aimed to modify the response in different neutron fields in order to reduce this uncertainty. Material and Methods: Thermo-luminescent dosimeters (TLDs) are widely used to determine neutron dose-equivalent. In the present study, a set of TLD-600 and TLD-700 dosimeters included in a TLD card was utilized to determine the response to “fast” neutrons of 241Am-Be,252Cf, and 239Pu-Be standard fields in four dose-equivalents of 5, 10, 15, and 20 mSv. Meanwhile, 241Am-Be was regarded as the calibration field. Results: As evidenced by the obtained results, for equal dose-equivalents, the original responses in 252Cf and 239Pu-Be fields are smaller, compared to those in the 241Am-Be filed. The maximum discrepancies were obtained at 26.8% and 42.5% occurring at 20 and 5 mSv, respectively. After the application of a correction factor equal to the average of relative responses (i.e., in 241Am-Be to two other fields) corresponding to all dose-equivalents considered, these differences reduced to 12.4% and 21.7%. Conclusion: It can be concluded that the correction method used in the present study could enhance the accuracy of dose estimated by TLDs in fast neutron fields.

Thermoluminescence study of pellets prepared using NaCl from Khewra Salt Mines in Pakistan.

In this study, the thermoluminescence characteristics of naturally occurring salt (NaCl) were assessed for the development of a radiation dosimeter. For this purpose, mined crystalline samples of salt were procured directly from Khewra salt mines in Pakistan. The samples were hand crushed, sieved, and compressed to pellets comparable in size to standard TLD chips, and irradiated to gamma radiation doses in the range of 5mGy and 5000mGy. Thermoluminescence (TL) response showed three main peaks in the glow curve around 115-130°C, 150-170°C, and 220-240°C. A linear TL response was observed for the dose range of 5-100mGy. The TL response became supra-linear for the dose ranges of 100-1000mGy and 1000-5000mGy. The Tm-Tstop method was applied to identify the overlapping peaks of the glow curve. Computerized glow curve deconvolution (CGCD) was then employed for the characterization of electron trap parameters such as frequency factor (s), activation energy (E), and the kinetic order (b), using General Order (GO) kinetics. The figure-of-merit (FOM) was found to be 1.08%, 0.94%, 0.77%, and 0.75%, at 500mGy, 1Gy, 2Gy, and 5Gy, respectively. The TL intensity faded by 20% within the first 24h after irradiation and finally stabilized after two weeks. In addition, structural, morphological, and elemental analyses, were also performed using various analytical techniques. X-ray diffraction (XRD) showed that the salt crystallizes in a face-centered cubic structure. Scanning electron microscope (SEM) micrographs indicated that the crystallites are closely packed and cubic-shaped with non-uniform size, and mostly found in the agglomerated form. Similarly, the elemental analysis confirmed the presence of impurities such as Mg, Sr, S, K, O, and Ca, in the samples. The present study concludes that the pellets made from salt samples from Khewra mines have a potential for use as radiation dosimeters.

Thermoluminescent properties of LaAlO3:C crystals synthesized by solid state reaction applied to UV Dosimetry

In this work we have investigated the thermoluminescent (TL) response of carbon doped lanthanum aluminate crystals grown by solid state reaction method. We conducted three syntheses by different combinations of Al2O3, La2O3 and 0.1 wt % of carbon atoms. The 1:1 mixture of aluminum and lanthanum oxide was mixed with 0.1wt.% carbon and annealed at 1700°C for two hours in a hydrogen atmosphere. The X-ray diffraction analysis revealed the formation of the rhombohedral LaAlO3 crystallographic phase. F and F+ centers were identified by ultraviolet-visible spectroscopy. Fourier transform infrared spectroscopic data show higher and lower frequencies assigned to AlO6 octahedra in LaAlO3. The UV irradiations were carried out using a commercial 8W UV lamp. Thermoluminescence measurements were performed at a Harshaw 4500 TL reader. The three syntheses were very efficient to obtain carbon doped LaAlO3 crystals with high thermoluminescent output, for low exposure rates of UVR fields.

Continuous trap distribution and variation of optical properties with concentration in oxi-fluoroborate glass doped with Nd3+

Alkaline earth borate glasses are being studied due to their interesting structure and properties. Here, the optical properties of some barium oxyfluoride glasses are reported. The absorption spectra by means of Judd Ofelt theory, the room temperature luminescence, and the thermoluminescence (TL) response as a function of dopant concentration were studied. The effect of the concentration on the thermal stability and the glass structure was also analyzed. The incorporation of Nd 3+ affects not only the optical properties but also the thermal ones. From Raman spectroscopy, no great differences were observed among undoped and doped glass samples. Judd-Ofelt parameters are lower or comparable to other borate and silicate systems. The temperature of the maximum intensity on the TL curve does not change with the irradiation dose, indicating samples follow a first-order kinetic model. However, the detailed TL analyses evidenced a continuous distribution of the activation energy and the signal stability after irradiation was also studied and interpreted in the same way. The results presented here indicate that the oxy-fluoride borate glasses are promising materials for TL applications.

Characterization of passive dosimeters in proton pencil beam scanning - A EURADOS intercomparison for mailed dosimetry audits in proton therapy centres.

The lack of mailed dosimetry audits of proton therapy centres in Europe has encouraged researchers of EURADOS Working Group 9 (WG9) to compare response of several existing passive detector systems in therapeutic pencil beam scanning. Alanine Electron Paramagnetic Resonance dosimetry systems from 3 different institutes (ISS, Italy; UH, Belgium and IFJ PAN, Poland), natLiF:Mg, Ti (MTS-N) and natLiF:Mg, Cu, P (MCP-N) thermoluminescent dosimeters (TLDs), GD-352M radiophotoluminescent glass dosimeters (RPLGDs) and Al2O3:C optically stimulated dosimeters (OSLDs) were evaluate. Dosimeter repeatability, batch reproducibility and response in therapeutic Pencil Beam Scanning were verified for implementation as mail auditing system. Alanine detectors demonstrated the lowest linear energy transfer (LET) dependence with an agreement between measured and treatment planning system (TPS) dose below 1%. The OSLDs measured on average a 6.3% lower dose compared to TPS calculation, with no significant difference between varying modulations and ranges. Both GD-352M and MCP-N measured a lower dose than the TPS and luminescent response was dependent on the LET of the therapeutic proton beam. Thermoluminescent response of MTS-N was also found to be dependent on the LET and a higher dose than TPS was measured with the most pronounced increase of 11%. As alanine detectors are characterized by the lowest energy dependence for different parameters of therapeutic pencil beam scanning they are suitable candidates for mail auditing in proton therapy. The response of luminescence detector systems have shown promises even though more careful calibration and corrections are needed for its implementation as part of a mailed dosimetry audit system.

TL Characteristics and Dosimetric Aspects of Mg-Doped ZnO

Dosimetry characterization and the evaluation of kinetics parameters of trapping states of Mg-doped ZnO phosphors synthesized by Sol-Gel technique. The thermoluminescence response of Mg-doped ZnO samples showed a linear response when exposed to X-ray radiation and the optimum annealing condition was 400oC/4h for the three concentrations. A broad-shaped TL glow curve with an upper bound of 270 °C, which shifts to lower temperatures with increasing dose, indicating that general order (GO) kinetics thermoluminescence processes are involved. We conclude that the ZnO doped Mg phosphors under study are promises to develop dosimeters for high radiation dose measurements. Kinetic parameters, such as activation energy (E), frequency factor (s), and order of kinematic order (b), were estimated by the Glow Curve Deconvolution (GCD) method. ZnO:Mg phosphor has a great potential as a dosimeter for monitoring in the fields of ionizing radiation.

Fading and residual responses for thermoluminescent dosimetry of silica beads irradiated using a high-dose electron-beam

Thermoluminescent (TL) glow-curves of 10 different coloured Toho Japan bead types have been obtained using a Risø TL/OSL reader studied for a fading period of 6 months as well as for residual dosimetry for fading up to 16 months after irradiation. For the entirety of the delay period studied the Frosted beads showed the largest TL response followed by Pink and Rose beads. Pink beads showed the best fit to the second order polynomial fit applied to the observed fading. In a more detailed dose curve fitted for a 6 month delay between irradiation and readout in order to determine the nature of the TL response as a function of increasing dose, it was found to follow the same trend for all bead colours. The residual TL response was also studied for beads that showed a large TL response. In these studies all colours showed similar dose response curves to those for the 1st readout, with Pink beads showing the best agreement to the fit applied to model fading.

Impact of alkali metal cation (Li+) on luminescence behavior of CaSO4:Ce3+ nanophosphors

Herein we report the structural, morphological, photoluminescence (PL) and thermoluminescence (TL) properties of Li co-doped CaSO4:Ce3+ nanophosphors prepared successfully via co-precipitation method. The PXRD pattern confirmed the single-phase hexagonal structure with space group P3121(152) with JCPDS Card no. 76–02312. The average crystallite size was estimated by Scherrer’s and W-H methods are found to be in the range 40–90 nm. These results are well agreed with the TEM results. The SEM micrographs reveal a wire-like structure with an average size ranging from 80 to 110 nm. Under 293 nm excitation, the effective blue emission positioned at 305 and 328 nm which are characteristic of 5d → 4f (2F5/2 and 2F7/2) of Ce3+ ions. PL emission intensity is increased with an increase in Li+ ion concentration and reached a maximum of 5 mol% and then started decreasing. The results show that the addition of Li+ ions in CaSO4:Ce3+ lattice could induce a significant improvement of their PL intensity. The chromaticity coordinates and correlated color temperature of all the phosphors were studied and found to be located in the blue region. The TL response of the prepared nanophosphors to 10 Gy-5 KGy doses is studied and their kinetic parameters were discussed in detail. These outcomes specify that these phosphors are favorable material for luminescence centered optoelectronic devices.

Thermoluminescence properties of high-dose gamma-irradiated diamond films

Thermoluminescence (TL) properties of gamma-irradiated chemical vapor deposition (CVD) diamond films at high doses are presented. Samples of undoped and nitrogen-doped CVD diamonds were exposed to 60Co gamma sources and TL intensity as a function of the dose was analyzed. To evaluate the feasibility of using these materials as TL high-dose dosimeters, reproducibility of the TL signal, and the TL response as a function of absorbed dose from 100 Gy up to 10 kGy were studied. Furthermore, the fading of the TL glow curve was analyzed. Finally, to estimate the kinetics parameter values associated with the trap distribution in the CVD diamond, a computerized deconvolution was carried out by using the general order kinetics (GOK) model.

Evaluation of TL and OSL responses of CaF2:Tm for electron beam processing dosimetry

The thermoluminescence (TL) and infrared stimulated luminescence (IRSL) responses of in-house produced CaF2:Tm dosimeters are investigated in this work, envisaging their application in electron beam (EB) radiation processing. The irradiations were performed at an industrial EB accelerator (1.5 MeV) covering a dose rate range of 2–8 kGy/s and dose up to 10 kGy. In general, the TL glow curves display four peaks, termed as peaks 2, 3, 4, and 5, corresponding to temperatures at ~150, 200, 240, and 300 °C, respectively. The intensity of the low-temperature peaks (2 and 3) grows with the dose, while the others remain constant (saturated). Nevertheless, an evident dose effect on the glow curves manifests in decreased peak3/peak2 ratio with increasing doses.The CW-IRSL curves exhibit similar patterns with an initial signal increase, followed by an exponential decay. Instead of the normal monotonic decays, these peak-shaped curves might be due to the charge capture competition between empty shallow traps and recombination centers. Both TL and IRSL intensities increase linearly with doses up to 6 kGy, and for higher doses, they become sub-linear with a saturation trend around 10 kGy. Another common feature of TL/IRSL response is its dose rate dependence, being more sensitive at higher dose rates. Despite being dose-rate dependent, the CaF2:Tm dosimeters might be suitable for EB processing dosimetry. However, for their use as routine dosimeters, relevant dosimetric characteristics, such as fading and response reproducibility, have to be investigated. Work in this direction is underway.

Thermoluminescence response and its kinetic analysis of a natural milky quartz associated with tin-tungsten-fluorite mineralization

The current work was going to study the TL properties of natural milky quartz mineral associated with tin-tungsten-fluorite mineralization in the Eastern Desert of Egypt. The chemical compositions of the investigated samples were examined by Atomic Absorption Spectrometer. The samples were irradiated to different gamma doses from 250 mGy up to 2 kGy. The kinetic analysis of the glow curve was carried out and it revealed that there were composed of six trapping sites at energies 0.92, 0.99, 1.08, 1.22, 1.32 and 1.48 eV responsible for deconvoluted glow peaks at 417.1, 433.9, 474.1, 532.1, 571.8 and 641.7 K respectively. The TL response exhibited a linear behavior in the range from 5 Gy up to 500 Gy and supralinear attitude in the range 500 Gy up to 2 kGy. The minimum detectable dose of the investigated samples was evaluated as 627 μGy and the sensitivity was measured to be 293.27 Gy−1 mg−1. For the fading results, the TL-intensity of the samples was decreased to be 55% from its original value in five days and after then no change in the intensity was observed up to two months.

Thermoluminescence of fluorapatite mineral

Fluorapatite [Ca10(PO4)6F2] is a mineral of the apatite group of the highest occurrence in the world among phosphates. The material is known for its diverse luminescent properties, as fluorescent lamps and lasers. The thermoluminescence (TL) signal of apatite from various origins has been investigated in the past years, mainly of the Mexican origin. In this work, the objective was to investigate the TL of samples of the Brazilian natural fluorapatites submitted to beta-ionizing radiation. The chemical composition of the samples was obtained by the technique of X-ray fluorescence and the electronic transitions were verified by optical absorption in the visible region. The mineral presented a wide optical absorption band between 500 nm and 750 nm, typical of fluorapatite, and SEM/EDS showed a high percentage of purity. The registered Raman spectrum exhibits the characteristics modes from the PO43− tetrahedra, observed in fluorapatite, and a band at 1103 cm−1 characteristic of the (CaO3)2- carbonate group. The TL measurements were carried out using a commercial Risø TL/OSL reader, model DA-20, equipped with a built in 90Sr/90Y beta source, with different radiation doses (1–5 Gy). The TL glow curve showed three peaks located at about 350 K, 470 K and 570 K (heating rate of 1 K/s). The activation energy and the frequency factor associated with each peak were determined by different methods. In addition, the TL response (area under the peaks) has shown linear behavior in relation to the doses.

Application of microdosimetric concepts in CaCO3:Ce3+/Dy3+ for megalevel radiation dosimetry

The 150 °C and 290 °C thermoluminescence (TL) peaks in CaCO3:Ce were attributed to generically related traps. TL process in calcites arises from O2− interstitial ions and anion vacancies created during pre-sintering which serve as hole traps and electron traps, respectively. The TL response of CaCO3:Ce is supralinear in the dose range 0.5–5 kGy due to secondary electron track interaction and sublinear beyond 5 kGy due to saturation of traps. The charge state surrounding a cation vacancy and Oi2− in CaCO3:Ce3+ can be considered as 3- (2- from oxygen and 1- from Ce3+) since Ce3+ is prone to oxidation to Ce4+ state which increases 2-track interaction during γ-irradiation at high doses and 2-hole trapping by densely ionizing radiations. TL of CaCO3:Dy is dominated by Dy3+ emission (480 and 570 nm) and a linear TL response with dose in the range 0.5–15 kGy since track interaction probability is less.

Beta particle excited thermoluminescence of CaZrO3 phosphors synthesized by solid state reaction

In this work, the synthesis through solid state reaction and the thermoluminescence (TL) characterization of pellet shaped CaZrO3 samples is reported. X-ray diffraction confirms that orthorhombic CaZrO3 was obtained. The glow curve has two maxima located at 149 and 216 °C as well as a less intense maximum around 350 °C when a 5.0 °C/s heating rate is used after 64 Gy of beta particle exposure. A remarkably reproducibility of the TL response is observed in repeated irradiation – TL readouts cycles. The TL as a function of the dose displays linear dependence in the dose range from 0.5 to 256 Gy. The intensity of the maximum located around 216 °C remains 61% 14 days after irradiation, and then remains closely constant for longer times. The synthesized CaZrO3 exhibits TL properties potentially of interest for use in radiation detection and dosimetry.

Synthesis, structural, optical, and thermoluminescence properties of ZnO/Ag/Y nanopowders for electronic and dosimetry applications

In this study, ZnO99.5-x/Ag0.5/Yx (where 0≤ x ≤ 10) nanopowders were synthesized by using the hydrothermal method. The structural, optical and thermoluminescence properties of the prepared nanopowders were experimentally examined. Moreover, the effect of yttrium (Y) dopant ratio on the studied properties was discussed in details. The structural, morphological, optical properties of the prepared TL material were investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and ultraviolet–visible (UV–Vis) respectively. The pellets of the nanopowders were exposed to X-ray doses of up to 4 Gy to investigate their thermoluminescence response, sensitivity and reproducibility. The glow curve for the ZnO/Ag/Y sample was observed at yttrium dopant ratio of 7% mol and the main peak corresponding to 165 °C. The heating rate of 7 °C/s was found to be consistent with the highest TL intensity at a low standard deviation. The best TL response with minimum standard deviation was observed at 300 °C. The optimum annealing time corresponding to the highest TL response was 30 min. The study demonstrated a linear dose response with a strong correlation coefficient equal to 0.999. The sensitivity of the co-doped ZnO/Ag/Y nanopowders (pellets) was found to be 0.28, which is lower than that of TLD-100 chips by 3.5 times. The results demonstrated the suitability of the novel synthesized TL material for electronic and dosimetry applications.

Experimental verification of consistency of micro-silica glass bead thermoluminescent detectors for mixed gamma/neutron irradiation

The thermoluminescent response of micro-silica glass beads has prompted their use as dosimeters across a variety of incident ionising radiations. This work presents the latest of a campaign to investigate, and confirm, the suitability of glass beads for neutron dosimetry applications. The impressive spatial resolution coupled with the linearity of dose response over a large dynamic range makes their use especially appropriate for applications requiring high levels of sensitivity. Data has been taken within the mixed radiation field of an americium-beryllium (241AmBe) source for two contrasting geometric configurations, investigating the fall-off of counts with respect to distance and the bead-to-bead variability to a uniform radiation dose from a mixed neutron/gamma radiation field. The study also considers the effect of experimental variations due to ambient light levels and the bead mounting itself.The exceptional spatial resolution previously demonstrated allows for observation of fine detail in the plot of dose versus distance from the source. Additionally, fine resolution peaks similar to those observed in previous simulations and data are observed again here. In this work, we can exclude the possibility that these response peaks are related to the source-bead distance.

Luminescence sites and spectra of metal doped microwave synthesized Mg2SiO4:Tb

Terbium doped magnesium orthosilicate (Mg2SiO4: Tb) has been reported as the most efficient thermoluminescence dosimeter material. Further sensitivity improvements of Mg2SiO4: Tb may be achieved by co-doping with other metal ions. Performance is strongly influenced by the sintering conditions, as shown here for Mg2SiO4: Tb samples which were synthesized with microwave thermal processing. A series of Mg2SiO4: x mol% Tb (x = 0.5, 1, 3, 5, 7) and Mg2SiO4: Tb, M (M = Li, Na, Ca, Al, Ga) samples are compared. Photoluminescence (PL) and Thermoluminescence (TL) of all samples are dominated by the characteristic emission of Tb3+. Co-doping can improve the sensitivity, and this is linked to modification of the micro-structure, as revealed by SEM measurements. Among the co-doped samples investigated, Mg2SiO4: Tb, Na shows the highest TL response with the main TL peak at 196oC. Differences between processing with microwave heating and thermal sintering are apparent in terms of the association of the dopants. Benefits and future possibilities with wider applications are discussed.