Thermoluminescence Signal Research Articles

Induced thermoluminescence as a method for dating recent volcanism: Hawaii County, Hawaii, USA

We have measured the induced thermoluminescence (TL) properties of fifteen samples of basalts collected from the Big Island of Hawaii in order to continue our investigation into the possible utility of this technique as a chronometer. Previous studies of basalts from Idaho have suggested the induced TL of basalts increases with age. Meteorite data suggest two possible explanations for this observation which are that (1) the initial glassy or amorphous phases crystalize with time to produce feldspar, the mineral producing the TL signal, and (2) feldspars lose Fe as they equilibrate and since Fe is a quencher of TL this would cause an increase in TL. The old basalts from Kohala (>100ka), which are mostly alkali basalts, have TL sensitivities 10–100 times higher than the much younger tholeiites from Kilauea and Mauna Loa (<50ka). The thermoluminescence of feldspars is strongly dependent on composition and when this is corrected for, using literature data, the slope of the regression line for the plot of log TL sensitivity against historic or radiometric age for the Hawaii basalts is within 2 sigma of the regression line for the analogous plot for the Idaho basalts, although the Hawaii line is much shallower (0.0015±0.0012 for Hawaii cf. 0.0039±−0.0014 for Idaho, 2σ uncertainties). However, the intercepts are significantly different (0.78±0.18 for Hawaii cf. −0.079±0.28 for Idaho, 2σ uncertainties). These results suggest that TL sensitivity has the potential to be a means of dating volcanism in the 0–800ka range, although the scatter in the data – especially for the <50ka samples – needs to be understood, and a means found for its removal, before the technique has the possibility of being practically useful.

Can thermoluminescence be used to determine soil heating from a wildfire?

The Silverado wildfire occurred from September 12 to 20, 2014, burning 960 acres in Orange County, California. Soil samples from within the burn area were obtained and the thermoluminescence (TL) properties of those samples were compared against a control sample to understand wildfire heating. We performed a series of experiments investigating the degree to which the control differed from the wildfire soil samples. This work showed that soil heated by a wildfire had a distinctly different glow curve shape than the unburned soil sample. Moreover, it was possible to see changes in the TL signal as a function of soil depth in wildfire-heated samples. Our experiments suggest that minimal soil heating occurred below approximately 10 cm. Estimates of wildfire temperatures, however, were nuanced.

Thermoluminescence of chip inductors and resistors in new generation mobile phones for retrospective accident dosimetry

Luminescence dosimetric properties of inductors and resistors in mobile phones have attracted wide attention for their use in retrospective accident dosimetry. Thermoluminescence (TL) signal following optically stimulated luminescence (OSL) readout, which has been recently shown to be useful for dose re-estimation (Lee et al., 2016), when measured by a Risoe OSL reader without a Hoya U-340 optical filter, was found to be up to 85 times of that recorded with the Hoya filter (with transmission window 270–380 nm, necessary for recording the usual OSL signal) placed in front of the photomultiplier tube (PMT) in the reader. In view of this, a study of dosimetric TL properties, namely sample-to-sample variation, fading, zero-dose signal, minimum measurable dose, effect of room light, dose response and emission spectrum, was undertaken to explore the use of TL of inductors and resistors in new generation mobile phones for accident dosimetry. The hitherto unknown TL emission spectrum was found to exhibit an intense emission beyond 550 nm (peaking at 700 nm) when recorded in the range from 250 nm to 750 nm. Emission below 500 nm was smaller by orders of magnitude than that at 700 nm. As the TL and OSL signals have been attributed to alumina substrates of inductors and resistors, the TL emission spectrum was compared with that of dosimetry grade Al2O3:C. The emission spectra of inductors and resistors were found to differ significantly, not only from that of Al2O3:C, but also from each other. Although the differences in TL glow curves, optical emission spectra, fading, etc. Indicated a lack of universality in luminescence properties of alumina substrates in different electronic components, it was concluded that the TL of inductors and resistors in new generation mobile phones offers a better option for accident dosimetry than OSL, with the specific advantage of much lower post-irradiation fading.

Thermoluminescence properties of Li2B4O7:Cu, B phosphor synthesized using solution combustion technique

To determine the effects of various concentrations of the activators copper (Cu) and boron (B) on the thermoluminescence (TL) properties of lithium tetraborate, the phosphor was first synthesized and doped with five different concentrations of copper (0.1–0.005wt%) using solution combustion method. 0.01wt% Cu was the concentration which showed the most significant increase in the sensitivity of the phosphor. The second sort of Li2B4O7:Cu material was prepared by adding B (0.001–0.03wt%) to it. The newly developed copper-boron activated lithium tetraborate (Li2B4O7:Cu, B) material with 0.01wt% Cu and 0.001wt% B impurity concentrations was shown to have promise as a TL phosphor. The material formation was examined using powder x-Ray Diffraction (XRD) analysis and Scanning Electron Microscope (SEM) imaging. Fourier Transform Infrared (FT-IR) spectrum of the synthesized polycrystalline powder sample was also recorded. The TL glow curves were analyzed to determine various dosimetric characteristics of the synthesized luminophosphors. The dose response increased in a “linear” way with the beta-ray exposure between 0.1–20Gy, a dose range being interested in medical dosimetry. The response with changing photon and electron energy was studied. The rate of decay of the TL signal was investigated both for dark storage and under direct sunlight. Li2B4O7:Cu, B showed no individual variation of response in 9 recycling measurements. The fluorescence spectrum was determined. The kinetic parameters were estimated by different methods and the results discussed. The studied properties of synthesized Li2B4O7:Cu, B were found all favorable for dosimetric purposes.

Radio-Optically- and Thermally Stimulated Luminescence of Zn(BO2)2:Tb3+ exposed to Ionizing Radiation

The optical absorption of zinc tetraborate at different concentrations of the terbium impurity (0, 0.5, 1, 2, 4, 8 mol%) was analyzed. The radioluminescence (RL) emission spectra was obtained after beta irradiation of a 90Sr/90Y source. The RL spectrum showed the characteristics bands of Tb3+ with two main emissions at 489 nm and 546 nm which corresponding to the5D4→7F6 and 5D4→7F5 transitions respectively in this ion. The OSL and TL characteristics have been analyzed. The stimulation blue light (497 nm) of a diode laser at 500 mA was used to bleach the thermoluminescent (TL) signals obtained with 5Gy of 60Co source. The two main glow peaks (79 and 161 °C) are sensitives under 497 nm stimulation, and they were shifted to higher temperature values and faded their TL intensities. Similar behavior of TL glow curves before and after OSL stimulation with blue light was observed when the samples were exposed to 30 Gy gamma dose of 137Cs irradiator. The OSL signal response was linear with the dose range of 1-10 Gy and increased their response up to 200 Gy gamma dose. The OSL shows a bleaching sensitive shallow traps and diminishing the intensity of the TL glow curves remaining a complex traps distribution. The RL, TL and OSL properties were investigated in Zn(BO2)2:Tb3+ phosphor.

Using thermoluminescence signals from feldspars for low-temperature thermochronology

Abstract Natural thermoluminescence (TL) signals from feldspar crystals extracted from thermally stable drill cores ( T = − 4.1 − 60.2 ∘ C) exhibit a strong dependence on geologic and laboratory thermal conditions. As burial temperature increases, the position of the TL glow curve at half-maximum intensity (i.e., the T 1 / 2 parameter) shifts to higher measurement temperatures. This shift is also observed following isothermal treatments in the laboratory. This relationship can be explained using a kinetic model originally developed for the optical luminescence dating of feldspar grains. The thermal history of a sample is preserved in the degree of electron trap saturation as a function of thermal detrapping probability, which varies with recombination distance. A natural feldspar sample contains a range of thermal stabilities: the least stable traps will remain empty, the most stable will be full, and those traps which are partially filled will, in the case of thermal equilibrium, be diagnostic of the storage temperature. The T 1 / 2 parameter of a TL glow curve reflects which sites remain occupied. This interpretation is further borne out by additive dose measurements which illustrate that samples buried at lower temperatures are fully saturated at lower TL measurement temperatures ( ∼ 200 − 300 ∘ C) relative to warmer samples. This signal is estimated to be useful in rapidly-cooling bedrock and should grow measurably for ∼ 10 2 − 10 6 years.

OSL and TL retrospective dosimetry with leucite glass-based dental ceramics

Dental ceramics are radiation sensitive materials and exhibit luminescent properties. Their samples can be potentially used for individual dose assessment in situations where retrospective dosimetry is required. In this work, we investigated dosimetry properties of two leucite glass-based dental ceramics using Optically Stimulated Luminescence (OSL) and Thermoluminescence (TL). We concentrated on characteristics as reproducibility, fading, optical bleaching, minimum detectable dose (MDD), dose response and photon energy response of TL and OSL signals. Both the dental ceramics exhibited very good reproducibility (<5% at 2σ level) when irradiated and measured repeatedly. Their luminescence response was found to be linear for a wide range of doses up to 8.5 Gy. The MDD values for the samples investigated were a few mGy. The ceramics are not tissue equivalent materials, and their luminescent signals measured were strongly dependent on incident photon energy. Because of fading and optical bleaching the OSL and TL signals were not stable in time. Especially optical bleaching represents a main limiting factor for dose reconstruction. However, one of the ceramics provided a relatively resistant high temperature TL peak for dosimetry.

Studying CaSO4:Eu as an OSL phosphor

This study was carried out to investigate the properties of the OSL signal from Eu-doped calcium sulfate (CaSO4:Eu) phosphor and study on its thermal behavior as a function of temperature under a series of luminescence experiments. The suitability of its usage as an optically stimulated luminescence (OSL) dosimeter was also checked. CaSO4:Eu was synthesized using the precipitation method and prepared in pellet form. The dopant concentration value was performed as 0.1mol%. The synthesized CaSO4:Eu was analyzed by X-ray diffraction (XRD) method to confirm the product. To have an idea about the crystallography and microstructure morphology of the material, scanning electron microscope (SEM) analysis were carried out. It was found that the OSL signal is a resultant signal having three components and exhibits thermal quenching above 150°C. The excitation spectrum of CaSO4:Eu showed different peaks in the region 220–360nm with the highest one at 269nm. Thermoluminescence (TL) signals of CaSO4:Eu pellets were obtained and compared with the TL signals obtained after OSL measurements of the same pellets by blue light stimulation. The low temperature peak near 180 °C did not show any significant change in TL after OSL measurement whereas the high temperature peak at 240°C was bleached with the blue light illumination and might be responsible for the observed OSL signal.The dosimetric properties such as dose response, minimum detectable dose, energy response, reusability, fading properties, thermal stability and effect of reading temperatures on OSL signals were examined. OSL signals of CaSO4:Eu pellets were decreased by approximately 8% at the end of the 24h and by about 7% at the end of 28days when compared with the first readout. The thermal stability of the ∼240 °C TL peak and OSL signal using isothermal decay measurements were used to determine the trap parameters. The CaSO4:Eu OSL dosimeter in accordance with the presented study allows a high-sensitivity OSL phosphor whose host material was previously known as conventional synthetic CaSO4 TLD material.

Luminescence characteristics of some common polyester fabrics: Application to emergency dosimetry

A set of garment polyester-mix fabrics was tested for their potential suitability as surrogate dosimetry materials using optically and thermally stimulated luminescence techniques. A strong native blue-stimulated optically stimulated luminescence and thermoluminescence signal was observed with unirradiated samples, but this could be avoided by measurement of infra-red stimulated luminescence, and a sample of blue polyester-cotton mix fabric exhibited particularly high sensitivity to radiation dose. However, near complete fading at room temperature within several hours and rapid bleaching of the signal when exposed to daylight limit the deployment of this mode of measurement. The fading behaviour is critically dependent on the atmosphere in which the material is measured and on the storage conditions, where a reduction in oxygen significantly reduces the rate of fading. A cathodoluminescence study of the samples performed in a scanning electron microscope revealed complex emission spectra obtained with spatially integrated measurements and, in one fabric examined in more detail, the spatially resolved emission was found to vary in intensity and wavelength within the polyester fibre filaments which is likely to be associated with differences in crystallinity.

Radiation Dose Evaluation of Colorless Topaz by TL and ESR Spectroscopy

In the present work, colorless topaz was designed and developed a dosimeter for routine application. The samples were irradiated with gamma from 60Co at dose range 50 - 400 Gy and investigated by thermoluminescence (TL) and electron spin resonance (ESR). The TL grow curve of topaz were revealed two trapping levels at temperature 150 °C and 225 °C. The ESR signals of topaz shown that the g value at 1.966 and 2.012 due to Ti3+ and (AlO4)0 center, respectively. The intensities of TL and ESR were increased with increasing dose. The percentage error of dose from TL and ESR signal were 8 and 3, respectively. These experiment indicated that the colorless topaz could be used as a dosimeter.

Low temperature thermochronology using thermoluminescence signals from K-feldspar

Abstract Thermoluminescence (TL) and isothermal thermoluminescence (ITL) signals from K-feldspar were studied. The signals from K-feldspar have provided multiple thermometers for thermochronological study. Protocols of multiple aliquot (MA) additive-dose (A) and regenerative-dose (R) have been applied and tested for equivalent dose (De) determinations using TL and ITL signals (MAA-TL, MAR-TL, MAA-ITL and MAR-ITL). Single aliquot regenerative-dose (SAR) protocol was only applied for De determination using ITL signals (SAR-ITL). A 50–60°C translation of heating temperature was necessary for the ITL De values to agree with TL De values. Based on the experiment results and merits-drawbacks comparison of the five tested protocols, the MAR-TL and SAR-ITL are favorable because of their efficiency and accuracy in De determinations. These two protocols were further applied to the samples from the Nujiang River valley and both explicitly demonstrated the thermal history of the samples. They are suitable for K-feldspar thermochronology study. They, as a parallelism of the previous studies of quartz TL and ITL signals, can provide multiple measures for a rock sample with the same thermal history in geo-thermochronological studies.

The physical properties of phosphate calcium glass doped with titanium oxide nanoparticles

The present study was aimed to prepare and investigate the phosphate calcium glass doped with different concentrations of titanium oxide nanoparticles. The structures of xTiO2 (100−x) P2O5CaO glasses, with x=0, 5, 10, 15, 20, and 25 were studied by the X-ray diffraction (XRD) and the scanning electron microscope (SEM). The time-dependent fading behavior of TL characteristics was investigated. The kinetic parameters, such as kinetics order, activation energy, and frequency factor, related to the glow peak were determined using the TolAnal software. The thermoluminescence (TL) characteristics of these irradiated glasses with gamma radiation doses, were studied in the temperature range 50–400°C, and with a heating rate of 30°C/s. The gamma irradiation was performed in the range of 1–500Gy. The glow curves of the blank sample 50P2O5 50CaO, exhibited a dosimetric peak at temperature of nearly about 200°C, and the high-temperature peak was at 300°C; while after the addition of TiO2, only one peak was observed at 300°C. The sample 37.5P2O5 – 37.5CaO - 26TiO2 induced the generation of TL signals upon irradiation, and with the highest TL response. The linear dose response was observed up to 500Gy

The thermoluminescence response of Ge-doped flat fibre for proton beam measurements: A preliminary study

The aim of this study was to investigate the thermoluminescence (TL) response of fabricated 2.3 mol% and 6.0 mol% germanium (Ge) doped flat optical fibres to proton irradiation. The fundamental dosimetric characteristics of the fibres have been investigated including dose linearity, reproducibility and fading. The thermoluminescent dosimeters (TLDs) were used as a reference dosimeter to allow the relative response of the fibres. The results show that Ge-doped flat fibres offer excellent dose linearity over the dose range from 1 Gy up to 10 Gy with correlation of determination (R2) of 0.99. The fibres also demonstrated good reproducibility within the standard deviation (SD) of 0.86% to 6.41%. After 96 days post-irradiation, TLD-100 chips gave rise to the least loss in TL signal at around 18% followed by fabricated 2.3 mol% Ge-doped flat fibres about 24%. This preliminary study has demonstrated that the proposed fabricated Ge-doped flat fibre offers a promising potential for use in proton beam measurements.

Study of Residual TL of CaSO4:Dy-based ThermoluminescenceDosemeter.

Thermoluminescence (TL) signal obtained during second readout of aTL dosemeter disc previously exposed to ionising radiation is termed as residual TL. The origin of residual TL has not been discussed in detail so far in the literature. In this work, experimentally obtained residual TL signal and its origin is studied for CaSO4:Dy-based TL dosemeter through numerical simulation and role of deeper traps has been discussed.

Optically and thermally stimulated luminescence of CaB6O10:Ce,LiCl: Basic properties

The goal of the present investigation is to explore the optically stimulated luminescent (OSL) properties of CaB6O10:Ce,LiCl in order to verify its viability as detector of ionizing radiation. Here, we investigate basic dosimetric and luminescent properties of this material. To this end, we carried out radioluminescence (RL), thermoluminescence (TL) and OSL measurements. We investigated the dose-response to ionizing radiation, the luminescent emission spectra, stability of the TL signal, and lifetime of the associated luminescent centers. The crystalline phase was verified by X-ray diffraction. TL measurement shows that the material is highly sensitive to ionizing radiation with a dominant TL peak at ~290°C. RL measurement features a broad-band spectrum in contrast with the spectrum recorded during TL readout, which is narrow and was attributed primary to the 5d-4f transition from Ce3+. The time-resolved OSL is characterized by two fast components, namely, 70.1(6) ns and143(4) ns and thus, suitable for 2D laser scanning readout. Dose-response curve was linear over the tested range (2mGy−300Gy) without trend to saturation. The current drawback is the OSL signal fading of up to 80% within 24h by computing the initial intensity and of up to 50% by computing the integrated signal over 100s. In principle, this issue may be solved by a fast heating of up to 80°C prior to readout.

Phototransferred thermoluminescence (PTTL) dosimetry using Gorilla® glass from mobile phones

Samples of Gorilla® glass (Corning®) from several touchscreen mobile phones were prepared and analyzed using phototransferred thermoluminescence (PTTL) in an attempt to retrospectively assess radiation doses absorbed by the glass for potential applications in emergency dosimetry. Samples of glass were prepared by cleaning and cutting into small pieces. Glow curves were recorded after irradiation to different doses, pre-heating to a given temperature, and exposure to ultraviolet (UV) light (365 nm) for various times. The dependencies of the thermoluminescence signals so-obtained on the pre-heat temperature and the duration of UV light exposure were studied. The stability of the PTTL signals was also studied for samples stored under ambient conditions. The PTTL signals were quite stable with little change after storage over several days. Dose response curves (PTTL versus initial applied dose) were linear up to ∼20 Gy. Values of minimum detectable dose (MDD) evaluated using PTTL were determined for samples from different phone brands. A non-radiation-induced, UV-light-stimulated TL signal was also observed as a result of the UV exposure. Variability in the strength of this signal and in the PTTL sensitivity of the various glasses leads to a variation in, and places limits on, the obtained values for the MDD. Typical MDD values were found to range between 0.1 Gy and 5 Gy. A method for accounting for the UV-induced signal is suggested involving pre-heating to high temperatures (550 °C). An exploratory test of a suggested protocol for evaluating dose from smartphones using PTTL is described and the results are compared with those obtained using optically stimulated luminescence (OSL) and thermoluminescence (TL) methods from other phone components.

Spectroscopic account of the point defects related to the sensitization of TL peaks beyond 220 °C in natural quartz

This study investigates the origin of point defects involved with a strong sensitization of the thermoluminescence (TL) signal of natural quartz between 220 and 400°C. The sensitization was produced by the combined effect of high-dose of γ radiation and heat-treatments at moderate temperatures. The point defects related to silicon and oxygen vacancies and also with Al, Ge, Li, and OH impurities were assessed by infrared (IR) and electron paramagnetic resonance (EPR) spectroscopy in samples prepared from two single crystals with different sensitivities. The signal intensities of the point defects were measured in as-received, zeroed, γ-irradiated, sensitized and also after heat-treatments carried out up to 600°C. The deconvolution of the TL curves showed that the major peaks appeared around 240 and 325°C. The spectroscopic analysis showed the presence of several point defects identified as E’1, [E’1-GeO4]0, [O23-/Li+]0, [GeO4/Li]0, [AlO4]0, [AlO4/H]0, [BO4/H]0 and Li-dependent OH centers. The sensitization process was efficient to increase the number of electron traps by means of a stable coupling (up to 400°C) between E’1, [GeO4]0 and Li+ ions dislodged from [AlO4/Li]0 centers. It was concluded that the active electron traps responsible for the TL emission above 220°C were [GeO4/Li]0 and E’1 centers whereas [AlO4]0 was the main recombination center. The thermal behaviour observed for [E’1-GeO4]0 and [O23-/Li+]0 signals showed that the creation of these centers are connected each other. A sequence of reactions involving Li+ motion plus electron-hole recombination at localized transitions within ([GeO4/Li]0, [AlO4]0), (E’1, [AlO4/Li]-) and ([E’1-GeO4]0, [O23-/Li+]0) defect pairs were proposed to explain the TL process in sensitized samples after the impartment of a given test-dose. The precursors for [E’1-GeO4]0 and [O23-/Li+]0 centers were assumed to compete with the active traps responsible for TL peaks found at 240 and 325°C peaks.

Influence of optical fiber diameter on thermoluminescence response

Detailed investigation is made of the thermoluminescence (TL) response of various sizes of optical fiber, fibers being developed with either a fixed core-to-cladding ratio or various core-to-cladding ratios. Two Ge-doped optical fiber preforms have been used to reconfirm the experimental findings. For further clarification, a pure silica rod has also been used to fabricate different diameter rods. Experimental investigations show the main TL signal to be generated from the fiber core within which the Ge is doped, the fiber cladding producing insignificant TL signal. Prior to normalization, the results show that in doubling the fiber diameter the TL signal quadruples. Conversely, subsequent to normalizing the different sizes of optical fiber to their mass or fiber cross sectional area, the smaller diameter fibers show slightly greater sensitivity compared to the larger diameter fibers. Relating to the fiber drawing-down process, this is due primarily to the greater shearing effect that the smaller fibers experience compared to the larger fibers within the fiber preform neck-down region.

Photo-transferred thermoluminescence of shallow traps in β-irradiated BeO ceramics

Photo-transferred thermoluminescence signals from beryllium oxide (BeO) ceramics were measured in the low temperature range of 10–300K. Samples irradiated at room temperature using a Sr90/Y90 beta source were cooled down to 10K and trapped charges were photo-transferred at this low temperature using the light from a high power blue LED emitting at ~470nm (2.6eV). Thermoluminescence glow curve recorded at 0.2K/s heating rate exhibited three peaks around 90, 160 and 185K. The analyses of the TL peaks of the glow curve were accomplished using curve fitting, differential and peak shape methods. Results obtained from these techniques are in good agreement about the presence of three trapping centers in BeO ceramics with activation energies of 0.24, 0.48 and 0.56eV. Moreover, the analyses indicated that first-order kinetics (slow retrapping) is the dominant mechanism in the luminescence process. Heating rate dependence of the glow curves was also investigated between 0.2 and 0.8K/s rates.

Luminescence properties of common salt (NaCl) available in Nigeria for use as accident dosimeter in radiological emergency situation

In the event of a radiological accident or attack, it is important to assess and quantify radiation dose to the population. This could be done using materials in the vicinity that are sensitive to ionizing radiation. Common salt (NaCl) is known to be a sensitive thermoluminescence (TL) phosphor. Luminescence properties of common salt (NaCl) used in Nigeria were investigated using an automated luminescence reader Risø TL/OSL-DA-15, with attention focused more on the Optically Stimulated Luminescence (OSL). Strong radiation-induced TL and OSL signals were observed. The TL peaks occurred at about 100 °C, 240 °C and 280 °C. The dose response of both the TL and OSL signals showed a linear relationship. From the OSL pulse anneal curve with TL curve, a preheat temperature of 190 °C for 10 s was found adequate for the OSL measurements. There was no significant difference in the OSL decay for stimulation temperatures of 100 and 120 °C. Fading experiment over a storage period of 14 days showed about 13 and 3% decrease in the OSL signal of sample 1 and sample 2, respectively. The ratios of measured to given dose for dose recovery test were within ±19% of unity. Within the limit of error the samples could be used as a complementary emergency dosimeter in radiological accident situation.