TL Signal Research Articles

Comparative analysis of predose effects on TL and OSL signals in BeO dosimeters

This study investigates in detail the effects of predose on TL and OSL signals for BeO dosimeters. The TL and OSL signals were deconvoluted to each peak and component. As a result of deconvolution, the variations in the kinetic parameters (E, Tmax, b) for the TL signals and the lifetime values of the OSL signals were investigated. In addition, sensitivity changes according to predose were monitored for each peak and component. Finally, dose response curves were studied using the dose linearity index (f(D)) for each peak and component. Accordingly, the peak structures and kinetic parameters did not change according to the predose for the TL signal, whereas variations in the lifetime values for the OSL signal were observed, especially at the initial dose values (0.1 and 0.2 Gy). There was no change in sensitivity according to the predose for the total area condition although each peak and component exhibited independent behavior. Therefore, TL and OSL signals should be evaluated based on the total area in predose applications. The TL and OSL dose response curves exhibited different behaviors according to predose. TL dose response curves were not affected by the predose except for 1000 Gy, while the OSL dose response curves were affected by the predose considering the total area condition. The possible reason for the differences between the TL and OSL dose response curves is the significant transfer effect in the OSL signal at low doses, which results in greater changes at low doses compared to the TL signal. Also, thermal quenching effects may have resulted in lower intensity in the case of the TL signal. In future studies, preheating tests and thermal quenching corrections on TL peaks at high predoses may increase our understanding of deep trap interactions in BeO dosimeters.

Effect of heat treatment on chemical durability and TL dosimetric properties of Na2O-SrO-B2O3 glass system

Na2O-SrO-B2O3 glass system prepared by the known melting-quenching method was applied to a progressive heat treatment (HT) at 600 °C for 4, 6, 8 and 10 h. Glass (G) and its corresponding heat treated (HT) samples were characterized by density, molar volume and XRD technique that revealed the complete amorphous structure of the glassy matrix and the coexistence of two crystalline phases in the corresponding glass ceramics; monoclinic phase of NaSrBO3 and the triclinic phase of sodium strontium pentaborate Na3SrB5O10. Testing chemical durability of G and HT samples at 95 °C for 24 h, revealed higher chemical stability in aqueous (H2O) and acidic (H2SO4) solutions, while the highest leachability was detected in the alkaline medium (NaOH). pH of leaching solution was found to control the leaching process and displayed rising behavior with time of immersion. The progressive rising of leaching solution temperature; 25, 40, 60 and 95 °C, revealed a quiet leachable enhancement as well. SEM photographs represented rough and heterogeneous surface morphology with continual leaching and the formation of colloidal layers at the later stages of corrosion.The TL-dosimetric properties indicated extremely higher thermoluminescence properties of HT samples than the untreated glass. The analysis of the exhibited TL signals revealed the composition of the glow curves of the treated and untreated samples of eight TL components. The obtained results recommend the acceptable chemical durability of the heat treated samples especially in the neutral medium that displayed no more than 8.5% leachability rate yearly, besides their promising TL-dosimetric features, accordingly their possible application in the field of radiation dosimetry.

SrAl2O4: Ce: Synthesis and dosimetric characteristics of a new highly sensitive TL phosphor for dosimetry

Strontium aluminate (SrAl2O4) doped with different Ce concentrations was synthesized by the solid-state reaction method to find the best thermoluminescent response. The crystal structure of the material has been analyzed by Rietveld refinement of X-ray diffraction (XRD) results. The effects of different dopant concentrations and thermal annealing regimes on TL sensitivity and the optimum conditions for producing dosimeters with superior sensitivity to commercial dosimeters were investigated. It has been shown that the maximum TL sensitivity is obtained at a concentration of 0.3 mol% Ce and a heat treatment at 1000 °C for 2 h. The TL glow curve of Ce-doped strontium aluminate (SrAl2O4) pellets shows three TL peaks at 90, 150, and 250 °C. The dosimetric characteristics of the new material examined in this work are linear response in the dose range with applications in personal and environmental dosimetry; TL sensitivity; minimum detection dose; reproducibility; energy dependence; and TL signal fading. Based on the results obtained, the synthesized material is a dosimeter with a sensitivity 2.44 times higher than the commercial dosimeter TLD-100 (LiF:Ti,Mg).

Effect of IRSL-BLSL-TSL reading modes combination on thermoluminescence (TL) response of BeO dosimeter.

The ultimate goal of this work is the study of the effect of luminescence stimulations and signals reading modes combinations on the thermoluminescence intensity and glow curve behaviour for the same X-ray irradiation dose. Three interesting stimulating and reading modes are considered, namely, infrared stimulated luminescence (IRSL), blue light-emitting diode stimulated luminescence (BLSL) and thermally stimulated luminescence (TSL). The studied stimulation and reading modes combination protocols are (Protocol 1) IRSL-TSL, (Protocol 2) IRSL-BLSL-TSL and (Protocol 3) BLSL-IRSL-TSL. Experiments are performed on beryllium oxide (BeO) dosimeter. Results demonstrate well that the combination of reading modes have direct impact on the TL signal in terms of intensity and glow curve shape. It was also found that when reading modes are correctly combined, particularly when IRSL is applied first, then BLSL and TL, it is possible to collect two or more exploitable signals of different stimulation types for the same irradiation that can be used for different purposes and final applications.

Structural Properties of Thermoluminescence Dosimeter Materials, Preparation, Application, and Adaptability: A Systematic Review

Thermoluminescence dosimeters (TLDs) are widely used in radiation dosimetry due to their excellent properties, such as high sensitivity, small size, and ability to measure low doses of radiation. This review focuses on the structural properties of TLD materials, as well as their preparation, application, and adaptability. The review covers the various types of TLD materials, crystal structure, and properties, including energy response and fading characteristics. The different methods used to prepare TLD materials, such as solid-state synthesis, sol-gel synthesis, and solution growth methods, are discussed in detail. The review also includes a detailed discussion of the various applications of TLDs, including medical, environmental, and industrial radiation dosimetry. Extensive information on TLD is reviewed, and the TL characteristics that have a noticeable impact on the TL dosimetry potential for human and other purpose utilisation, such as mineral, oil, and gas resource investigation, can be done using natural and artificial TL signals. Information on TL measurement process requirements and the TL characteristics that have a noticeable impact on a compound TL dosimetry potential are also addressed. Finally, the review concludes by highlighting the adaptability of TLD materials to different dosimetry applications and their potential use in the future.

On the use of new vs. heated sample carriers for luminescence measurements

To ensure precise luminescence measurements, it is crucial to carry out measurements on clean sample carriers. Moreover, it is essential to ensure that the light emitted by the studied sample is reproducibly reflected towards the detector, particularly when the sample exhibits dim luminescence. This study reports observations made by three laboratories working in the field of retrospective dosimetry. The study discusses the results obtained using new sample carriers (made of stainless steel), instead of sample carriers previously heated to a temperature of 450 °C. The article describes the cleaning protocols routinely used by each laboratory and the treatment with distilled water that effectively removed spurious signals. When measuring TL signals of resistors using new sample carriers, a signal reduction of 10% was observed in the second measurement compared to the initial TL. For display glass samples from a mobile phone, a signal reduction between 15% and 32% was observed. However, there was negligible change in reproducibility when using the previously heated sample carriers. The reflectance of the sample carrier surface was indirectly measured using breakthrough signal measurements using violet or blue LEDs. A signal reduction of 12–14 % was observed when heating was applied for 20 new, unheated sample carriers using violet LEDs. The impact on dose estimation is discussed, and some recommendations are provided to guarantee precise luminescence measurements.

Assessing whether a thermoluminescence peak at ∼100 °C in calcitic opercula can be used to monitor thermal reproducibility

The opercula of the gastropod Bithynia tentaculata is composed of calcite and exhibits three main thermoluminescence peaks at ∼100, 280 and 360 °C when heated at 0.5 °C.s−1. The two higher temperature peaks can be used for geological and archaeological dating, whilst the lower temperature peak has a lifetime of hours and is only seen after laboratory irradiation. This study explores whether this lower temperature TL peak can be used to assess the reproducibility of laboratory heating of opercula. As found in previous studies, the TL peak at ∼100 °C is seen to consist of at least two signals which have different lifetimes at room temperature. By fixing the interval between irradiation and measurement of the TL signal, the impact of these different lifetimes on the temperature at which the TL peak occurs (Tm) can be reduced, and replicate measurements on a single operculum using the same radiation dose yield values of Tm within 1 °C. Comparison of different opercula shows variation in Tm of 9 °C when heating at 5 °C.s−1, interpreted as primarily arising from variation in thermal lag between the hotplate and the different samples assessed. Reducing the heating rate to 0.5 °C.s−1 reduces the variation in Tm between opercula to 2 °C. Imaging the TL emission from opercula using an EMCCD shows spatial variation in heating, and also demonstrates the reduction in variability that can be achieved by using a slower heating rate. Thus, monitoring the position of the TL peak at ∼100 °C can be used to assess thermal reproducibility of TL measurements on calcitic opercula.

Solution Cathode Glow Discharge – Atomic Emission Spectrometry (SCGD-AES) With an Interference Filter for Spectral Discrimination for the Determination of Thallium in Surface Water

Solution cathode glow discharge atomic emission spectrometry (SCGD-AES) using wide-bandpass (10-nm) interference filters (IF) as a spectral discrimination device was used for the determination of thallium (Tl) in surface water. The use of wide-bandpass interference filters greatly reduces the cost of traditional detection instruments. The influence of solution flow rate, discharge current and pH on the detection limit was characterized. Moreover, matrix effect experiments were performed to study the effect of different concentrations of Na+, K+, Ca2+, and Mg2+ on the Tl signal intensity. Using a solution flow rate of 2.8 mL/min, a discharge current of 50 mA, and pH of 1.0 with HNO3 as the supporting electrolyte, SCGD coupled with an interference filter provided a detection limit of 7.76 μg/L for Tl in water samples, comparable to traditional SCGD-AES. Furthermore, the spiked recovery rate of Tl is quantitative in real water samples and comparable to the performance of inductive coupled plasma – optical emission spectrometry (ICP-OES).

Personnel dosimetry for the mixed beta (Kr-85)/photon (gamma, X-ray) beams using Harshaw 8814 TL dosimeters: Performance Test Applicability Study

Performance of Harshaw 8814 TL dosimeters was evaluated in the mixture of low energy beta (Kr-85, average energy 251 keV) and X-ray/gamma photon beams, when many doses obtained using existing dose calculation algorithms show a high bias. 264 TLDs were exposed at the Radiological and Environmental Sciences Laboratory to the pure Kr-85 energy beam as well as to different combinations of beta and photon beams of various energies (including Cs-137 and Co-60 gamma sources and M50, M200 and H300 X-ray beams). The TLDs were irradiated to different beta-to-photon dose ratios; 22 different combinations of radiation energy beams and beam dose ratios were tested. After exposure, the TLDs were readout at Brookhaven National Laboratory facility using a Harshaw 8800 reader. The doses were determined with the Harshaw Combined DOELAP dose calculation algorithm and compared to the known values. The results showed a significant deviation from the corresponding nominal values for some of the tested TLDs exposed to pure Kr-85 or a combination of Kr-85 and photon beam mixed energies. The different ratios of TL signals from chips 1–4 of the 8814 TL cards were analyzed, and an algorithm was proposed to identify the radiation beam energy to which each individual TLD was irradiated to. Finally, correction coefficients were developed which improves the performance of TL dosimetry dose calculation algorithm in the cases of exposure to a low energy beta beam and to a mixture of such beam with photons.

Preparation and Thermoluminescence Properties of Polycrystalline Na2SO4/SiO2 composite

A sodium sulphate/silica (Na2SO4/SiO2) composite was prepared by a sol-gel procedure using a geode as the silica source. The prepared sample was characterized by XRD, XRF and IR techniques. The Na2SO4/SiO2 has an orthorhombic phase, and an average crystalline size is about 51 nm. Thermoluminescence characteristics of Na2SO4/SiO2 were studied at different parameters. The glow curve resulting from Na2SO4/SiO2 showed one clear peak between 150 oC to 200 oC, depending on the energy. The general peak structure of the TL glow curve remains unchanged as a result of repeated cycles of irradiation at various X–ray energies, and exhibits good linearity over the used exposure. There were no significant changes in the TL reading after ten times of reuse, and the fading was observed at 56% after 15 days of irradiation and after one month about 82.3% of the TL signal was lost, and the value of Zeff of Na2SO4/SiO2 was found to be 13.56.

OSL at elevated temperature of smart chip cards for retrospective dosimetry

Smart chip cards are a promising material in retrospective dosimetry due to their high collectability with low replacement cost. In this study, dose reconstruction using OSL at elevated temperatures for various chip cards was investigated. The approximate spectral emission of the chip cards was determined through a comparison of radiation-induced and intrinsic background TL signals using different detection filters. In the OSL decay curve, a fast component (0.0–0.4 s) was integrated to avoid high intrinsic background signals. To minimize sensitivity changes due to heat treatment, a protocol to measure OSL at 100 °C was developed and the data were compared with those from a similar protocol for OSL measured at room temperature. In the 0.1 - 5 Gy range, linear and power functions were fitted for room temperature and 100 °C OSL protocols, respectively. The minimum detectable dose was evaluated immediately after exposure, with values of 25 mGy for room temperature and 240 mGy for 100 °C OSL being determined. Signal fading was measured up to 30 days after irradiation for the investigated protocols. A dose recovery test was made 10 days after irradiation using various chip cards, and the 100 °C OSL protocol produced more reliable results than the room temperature OSL protocol. As a result, the study emphasizes the necessity of further investigation of OSL at high temperatures using chip cards.

Unravelling the impact of unusual heating rate, dose-response and trap parameters on the thermoluminescence of Sm3+ activated GdAl3(BO3)4 phosphors exposed to beta particle irradiation

The thermoluminescence of GdAl3(BO3)4 (GAB) doped with various concentrations of Sm3+ (i.e. from 0.5 to 7 wt%), prepared by gel combustion, was studied. TL glow peaks at 78 °C and 225 °C are observed. The intensity of the glow peak at 225 °C increased with a faster heating rate. To gain insight into the trap activation energies, the methods of Hoogenstraaten and Booth-Bohun-Parfianovitch were used, where the calculated activation energies are 0.57 eV and 0.60 eV for Peak I and 1.69 eV and 1.71 eV for Peak II respectively. The dose-response of GAB:0.5 wt%Sm3+ demonstrates robust linearity up to 40 Gy, with a strong correlation coefficient of 0.999. Both TM-Tstop combined with the Initial Rise (IR) and Computerized Glow Curve Deconvolution (CGCD) techniques were employed, which revealed six overlapping glow peaks beneath the main peaks. Additionally, the results suggest that the TL signal can be efficiently exploited for radiation dosimetry applications.

Thermoluminescence of beta irradiated SrHfO3 powders synthesized by the Pechini-type sol-gel method

Here, we report on the thermoluminescence response of beta irradiated SrHfO3 powders synthesized by the Pechini-type sol-gel process. Powders calcined at 900 °C for 6 and 8h exhibited the orthorhombic phase of SrHfO3. The intensity TL response of SrHfO3 samples, exposed to beta irradiation doses from 0.085 to 1530 Gy, was found to increase with the irradiation dose. The TL signal of both samples showed a linear behavior in the range of 2.55–51 Gy and a sublinear behavior for higher irradiation doses. At the dose of 25.5 Gy, the TL response of the sample processed with a calcination time of 6h had the best repeatability with a standard deviation of 3.48% and the lowest fade (12.85%) in the first 48 h. The Tmax-Tstop process, initial rise method and glow curve fitting by computerized deconvolution were employed to determine the trap distribution and kinetic parameters. The TL glow curves of the samples were conveniently fitted by five glow peaks of first and second orders with activation energies ranging from 0.56 to 0.99 eV. Overall, the TL response of the samples showed to be influenced by the density and distribution of defects, mainly originated by oxygen and cation vacancies.

Investigating the OSL components and the sensitivity changes in a natural quartz crystal showing an intense post-sensitization TL signal

This study aims to investigate the optically stimulated luminescence of quartz grains exhibiting an intense thermoluminescent signal between 250 and 350°C after sensitization with a high dose of gamma radiation and moderate heat treatments. Pellet discs produced with zeroed and sensitized grains were irradiated with test doses ranging from 0.5 to 40 Gy. After sensitization, the OSL signal of the fast component stimulated with blue light increased more than 1000 times. Annealing at 400°C was adopted to erase the residual signal. The sensitivity changes were assessed after various TL and OSL readings. The annealing cycles were responsible for a significant increase in OSL and a 20% reduction in TL signals. The analysis of the residual TL indicated that the traps responsible for the main components of the sensitized peak (280°C) are harder to bleach than those related to the so-called 110, 325, and 375°C peaks. The sensitivity changes and the relationship between OSL and TL signals were explained in terms of a mechanism of competition involving active and deep electron traps. No correlation was observed between the fast OSL component and the 325°C TL peak.

A TL study of protective glasses of mobile phones for retrospective dosimetry

Several studies have shown that certain components of mobile phones, such as electronic components, display or touch screen glass, are suitable as emergency dosimeters in case of radiological incidents. However, so far the methods are frequently destructive and in case of a dose assessment the mobile phone will be destroyed. In order to overcome this problem, alternative materials need to be sought and further research is necessary. Building on results of a previous study, we further investigated protective glasses in this work, which have become an alternative material for dose reconstruction. Protective glasses are easy to sample and cheap, have become very popular to protect the surface of phones, can be easily replaced without complete destruction of an expensive smartphone, thus a dose assessment method based on this material will potentially find much greater public acceptance. The aim of this study was to optimize the detection window by systematically investigating the radiation-induced TL signals and intrinsic zero dose signals. Using two selected detection windows, the long-term and optical stability of the TL signals were investigated. The set of nine different protective glass samples studied fell into two groups with different fading and optical bleaching characteristics. Further research is necessary in order to reduce the zero dose signal, to reinvestigate the dosimetric properties and to verify the final protocol using a realistic irradiation test.

Optically stimulated luminescence of K2SO4:Ce and its relationship with TL glow-curves

K2SO4:Ce was investigated with respect to its OSL and TL properties. Due to the doping with Ce3+ ions, the material shows strong emission in the range of 300–400 nm with a maximum of approx. 330 nm. The spectrum of OSL stimulation is wide and enables stimulation with visible light and infrared. When comparing the 550 nm and 900 nm stimulation, differences in the initial intensity, decay rate and total counts can be seen. The higher total counts are obtained for 550 nm green light, with the initial intensity being higher for 900 nm infrared. The OSL signal, for both stimulations, is sensitive to preheat, however, this relationship is different in both cases. The study of the mutual correlation of the TL and OSL signal showed that only a part of the peaks in the TL curve are bleached by optical stimulation. The result indicates that there are both optically active and non-optically active traps in the material. The OSL-TL correlation study involves the deconvolution of the TL curves and the estimation of the bleaching of two main TL peaks and one minor peak. At least three traps are optically active but are emptied to varying degrees by different stimulations.

Evaluation of argon ion impact parameters in aluminium oxide by means of SRIM program and investigation of the effect of argon ion implantation on the thermoluminescence properties aluminium oxide

The thermoluminescence properties of aluminium oxide (alumina) implanted with 80 keV argon ions at fluences in the range of were investigated. The unimplanted and implanted samples were irradiated at a dose of 40 Gy and heated at a rate of 1°C/s. The glow curve of unimplanted and implanted samples shows 5 distinct peaks; the main dosimetric peak and four other peaks of lower intensity. In this study, our analysis has focussed on the main dosimetric peak located at 180°C, 191°C, 177°C, 208°C, 219°C and 207°C for the unimplanted sample and implanted samples respectively. It was observed that the TL intensity decreases with fluence of implantation. This suggests that ion implantation decreases the concentration of electron traps responsible for thermoluminescence. It can also be suggested that competition effects involving radiative pathways and non-radiative competitor traps may lead to a low thermoluminescence signal in the implanted samples in comparison to the unimplanted thermoluminescence signal. These competitive processes will tend to favour first-order kinetics, and consequently lead to a strong stability of the glow curve shapes. The creation of defect clusters as well as extended defects could also be responsible for the reduction in TL signal. The stopping and range of atoms in matter (SRIM) was used to evaluate the ion impact parameters including ion range, vacancy distribution and energy loss in Al2O3. Subsequent to ion implantation, it was found that the number of oxygen vacancies which are related to electron traps are higher than the number of aluminium vacancies. Kinetic analysis was carried out by means of the initial rise, Chen’s peak shape, various heating rate, the whole glow curve, glow curve fitting and isothermal decay methods. The activation energy was found to be around and the frequency factor to be of the order regardless of the implantation fluence. The dosimetric features of samples were also investigated at doses in the range of 40–200 Gy. Samples generally showed a superlinear response at doses less than 140 Gy and sublinear response at doses higher than 160 Gy.

Effects of oxygen vacancies on luminescence characteristics of BeO ceramics

Understanding whether the luminescence of BeO ceramics synthesized by co-precipitation technique is due to oxygen vacancies (Vo) or not is very important concerning the development of this material as an OSL dosimeter. This study investigates the effect of oxygen vacancies in undoped and alkali-metal doped BeO ceramics, on luminescence properties following laboratory and argon sintering processes. We created oxygen deficiencies in the BeO-based ceramics and obtained high-sensitivity OSL dosimeters. Considering that Vo defects are formed by sintering in an inert gas environment, we compared the structural and luminescence properties of this material with that of sintered in the air atmosphere. The crystallite properties of undoped and alkali-metal doped BeO ceramics were defined by XRD analysis. The presence of Vo defects was confirmed by ESR analyses. On the other hand, the smoother and non-porous surface structures were observed in SEM images. We observed an emission band originating from Vo appearing between 600 and 800 nm in BeO(Vo) ceramics in comparison with the RL signals of BeO ceramics. In addition, it was observed that the characteristic BeO emission band located between 200 and 400 nm increased significantly with sintering in an argon gas environment. A remarkable enhancement for TL and OSL signals was observed in BeO(Vo), BeO:Na5 %(Vo), BeO:Li5 %(Vo), and BeO:K5 %(Vo) ceramics when compared with the BeO, BeO:Na, BeO:Li, and BeO:K ceramics. Through this study, it can be concluded that the source of luminescence of BeO ceramics may originate from the oxygen vacancies that occur during synthesis in the structure. Eventually, the significant enhancement in luminescence from undoped and alkali-metal doped BeO ceramics can be controlled by applying the appropriate conditions during the synthesis.

Thermoluminescent and photoluminescent studies on the phosphor material from waste compact fluorescent lamps

The aim of this work was to investigate the photoluminescent and thermoluminescent properties of the recovered phosphor powder from the CFL when it is exposed to UV radiation of 254 and 365 nm of wavelength. This study was complemented with their photoluminescent analysis. Thermoluminescent results showed that UV radiation of 254 nm induced an intense TL signal characterized by a width glow curve with two peaks located at 162 and 292 °C, while UV radiation of 365 nm induced a weak TL signal. The photoluminescent studies showed that the emission spectra of the phosphorous materials are composed by three major emissions at 451, 512 and 611 nm corresponding to Ce3+, Tb3+and Eu3+, responsible for the white light produced by these lamps.

Thermoluminescence study of Pink Himalayan salt from Khewra mines, Pakistan

In this study thermoluminescence characteristics of the pink Himalayan salt has been studied. For this purpose, pellets of pink Himalayan salt weighing 40 mg were prepared. The ICP-OES and EDX analytical techniques were used to find the elemental composition of the sample. It confirms the presence of Al, Mg, Ca, Sr, S, Zn, K, Mn and Fe etc. along with the main matrix. The XRD analysis shows that the salt has face centered cubic (FCC) structure with average crystallite size of 70.6 nm. The scanning electron microscope (SEM) was used for surface morphology. To investigate the thermoluminescence properties, the pellets were irradiated with 137Cs source in the dose range of 1–5000 mGy. The glow curve indicated the presence of three peaks namely P1, P2 & P3 with two very prominent peaks occurring at 135 °C and 260 °C. The Tmax-Tstop procedure revealed the coinciding peaks in the glow curve and their relative positions. The trapping/kinetic parameters, such as electron trap depth (E), order of kinetic (b) and frequency factor (s) were explored by employing CGCD technique. The values of figures of merit (FOM) calculated at different doses (500 mGy, 1 Gy, 2 Gy & 5 Gy) were found to be 1.14%, 1.24%, 1.11% and 1.13% respectively. This indicates excellent agreement between the experimental and theoretical fitting. The post irradiation fading of the sample pellets were studied at dose of 500 mGy for different time intervals up to 8 week and 30% loss in TL signal was observed within first 24 h which becomes stable after 2 week. On the basis of these results it can be concluded that pink Himalayan salt has a potential to be used in radiation dosimetry.