Optically Stimulated Luminescence Signal Research Articles

Luminescence characteristics of newly-developed MgB4O7:Ce3+,Na+ phosphor as an OSL dosimeter

In this study, dosimetric properties of Ce3+ and Na+ doped magnesium tetraborate (MgB4O7) phosphors synthesized by the solution combustion synthesis (SCS) method were investigated using optically stimulated luminescence (OSL) technique to develop OSL radiation dosimetry. The concentrations of Ce3+0.3%wt and Na+1–14%wt dopants in MgB4O7 were incorporated into it to improve the efficiency of luminescence. The results showed that the effect of Na+ substitution on MgB4O7:Ce3+0.3%wt lattice induced a remarkable improvement of both its thermoluminescence (TL) and OSL signals. The highest OSL signal of the synthesized phosphor was recorded at the MgB4O7:Ce3+0.3%wt,Na+14%wt phosphor. Its TL glow curve consists of two peaks located at ~70 °C and ~230 °C with a heating rate of 2 °C/s. These TL peaks were found to be optically sensitive to blue light excitation (λ = ~470 nm). X-ray diffraction (XRD), scanning electron microscopy (SEM), radioluminescence (RL) techniques have been employed to characterize the synthesized phosphor. The XRD pattern of MgB4O7:Ce3+0.3%wt,Na+14%wt phosphor with orthorhombic phase was observed in the specimen sintered at 900 °C. The RL spectrum of the MgB4O7:Ce3+0.3%wt,Na+14%wt phosphor revealed a strong and a weak emission peak located UV and red regions, respectively. OSL dosimetric properties of the phosphor were studied under beta radiation of 90Sr/90Y. The phosphor exhibited good linearity between 1 and 100 Gy. Minimum detectable dose (MDD) of the phosphor was calculated as 0.73 mGy. A good reusability property was determined up to 20 experimental cycles with a deviation of 4.5%. Short-time fading up to 24 h and long-time fading up to 4 weeks were studied. The results shows the MgB4O7:Ce3+0.3%wt,Na+14%wt phosphor can be proposed as a potential OSL dosimetry for radiation dose measurements in medicine using OSL technique.

Evaluation of MgB4O7:Ce, Li and Ce-doped 80MgB2O4–20MgB4O7 as alternative OSL materials for use in quality assurance of 6 MV photon beams

We investigated the potential use of two new borate matrices for quality assurance (QA) tests in radiotherapy. Both matrices, MgB4O7:Ce, Li (MBO) and Ce-doped 80MgB2O4–20MgB4O7 (80-20MBO), were doped with 0.5% cerium oxide. The following dosimetric properties of these materials prepared as pellets were tested: optically stimulated luminescence (OSL) sensitivity, dose response, fading, reproducibility, and the supralinearity index. Subsequently, the pellets were exposed to a 6 MV photon beam, and the percentage depth dose (PDD) curve, OSL response to different dose rates, and radiation field size dependencies were compared with those obtained with a reference detector (ionization chamber, I.C.) used in QA. The results indicated a higher OSL sensitivity of 80–20MBO as compared with MBO, on the order of 6- to 8-fold. The dose response of MBO presented a linear behavior within the range evaluated (20 mGy–2 Gy), unlike 80-20MBO, which had a supralinear behavior. The OSL signal of 80–20MBO was also marked by 60% fading within 5 h post irradiation; afterwards, the OSL signal stabilized. A better reproducibility of 80–20MBO compared with MBO was also observed. No dose rate dependence of the OSL response was observed; moreover, a maximum 5% standard deviation was seen in this test. For the field size tests, the pellets over-responded by 3.1% (80-20MBO) and 3.4% (MBO), in a 3 × 3 cm2 field, compared with the I.C. For the PDD, a high deviation was observed if compared with the I.C. data at the build-up region (at a depth d ≤ 2 cm), maximum 4.3% and 7.8% for 80-20MBO and MBO, respectively, and beyond this value, good agreement among detectors was seen. Our preliminary results indicate the potential utility of these pellets in QA for radiotherapy.

Luminescence Dating of Late Pleistocene Lacustrine Deposits in Badain Jaran Desert, North China

Abstract There are still controversies for the lakes evolution time during late Pleistocene in arid/semiarid north China. Badain Jaran Desert (BJD) features the coexisting of modern lakes in the lowland of megadunes. Also, lots of lacustrine relics could be found distributed widely in the desert, some of them just beside the modern lakes. These lacustrine relics indicated the paleo lakes evolution and the paleo environmental changes in the desert. In this study, one 3.9 m depth lacustrine deposits section was studied in the southeastern BJD which is close to a modern lake Zongzegedan (ZZGD). The deposit ages of the section were obtained by using optical dating with both of quartz and K-feldspar grains. Optically stimulated luminescence (OSL) dating of quartz grains shows that this paleolake was appeared during 65–34 ka, which is in the Marine Isotope Stage (MIS) 3 period, without the saturation of the OSL signals. On the other hand, the high temperature infrared stimulated luminescence (pIR IRSL) dating results from K-feldspar grains show that the paleolake was existed from late MIS 5 to late MIS 4 (86–60 ka) period with also good luminescence characteristics. The further study suggested that the OSL signals from quartz grains in this section show thermal instability, which may lead to the age underestimation. So the reliable age of the existed paleolake should be obtained by using pIRIR signals from K-feldspar, indicated that the relative humid environment in the desert happened at late MIS 5. The paleolake has same position with modern lake in the desert may contain geomorphological indications.

Investigations on the Luminescence Properties of Quartz and Feldspars Extracted from Loess in the Canterbury Plains, New Zealand South Island

Abstract The applicability of the single-aliquot regenerative-dose (SAR) protocol, by using the optically stimulated luminescence (OSL) signal of quartz as well as the post-infrared–infrared (pIRIR) signals of polymineral fine grains, namely pIRIR225 and pIRIR290, was assessed for dating loess in New Zealand South Island. OSL signals of quartz grains displayed low sensitivity. However, the application of repeated irradiation/bleaching cycles did not result in an increase in sensitivity; annealing in the 300–500°C temperature range generated the sensitisation of both the 110°C thermoluminescence (TL) peak as well as the OSL signal, likely by activation of yet unidentified luminescence centres. After heating, the quartz signal is comparable to that of ideal samples, but the annealing is precluding successful dating. On the other hand, feldspar infrared-stimulated signals displayed satisfactory properties, allowing estimation of ages ranging from 14 ± 1–29 ± 3 ka for the investigated deposit. It was shown that pIRIR225 and pIRIR290 methods have potential for dating loess in the South Island of New Zealand, based on the following observations: (i) Dose recovery tests were successful with recovered-to-given dose ratios with a <10% deviation from unity, (ii) constant residual values of about 4 Gy and about 10 Gy were obtained after exposures for 48 h in the case of pIRIR225 signals and 96 h in the case of pIRIR290 signals, respectively, (iii) while a slight dose-dependence of the residual was reported, and for a dose as large as 1600 Gy the residual values are ≅9 Gy and ≅19 Gy for pIRIR225 and pIRIR290 signals, respectively.

OSL CHARACTERISTICS: THEORY AND EXPERIMENTS.

Fundamental effects such as the participation of crystal lattice vibrations should be taken into account while considering photo-ionisation in solids at measurement temperatures characteristic for dosimetric applications. The impact of these effects on the optically stimulated luminescence (OSL) can be recognised for example by changes in the optical cross-section of the trap with the stimulation energy and the temperature. The OSL signal observed during the stimulation with variable energy, during the linear heating of a sample or during the stimulation with modulation of the shape of a spectral band can provide important information about the properties of the trap. Moreover, such methods when applied with carefully selected experimental parameters enable the effective separation of the OSL signal originating from different traps. The consequences of such an approach to optical stimulation will be presented using the modelling of the OSL process and compared with experimental results.

Development of Ce3+ and Li+ co-doped magnesium borate glass ceramics for optically stimulated luminescence dosimetry

Magnesium tetraborate, MgB4O7, is an attractive host material for dosimetry due to the two characteristics: its low effective atomic number (Zeff = 8.4) and high neutron capture cross-section of the 10B isotope. Particularly, Ce3+ and Li+ ions co-doped MgB4O7 has shown optically stimulated luminescence (OSL) signal comparable to that of Al2O3:C, which is a well-known OSL dosimetry material. In this work, for further improvement of the dosimetric properties, a new synthesis route for MgB4O7:Ce3+-Li+ is described: glass-ceramic (GC) MgB4O7:Ce3+-Li+ samples were prepared by heat treatment of the magnesium borate glass with the composition, 25MgO–72B2O3–3Li2O-0.3Ce3+. The prepared GC samples show UV-blue radioluminescence assigned to the Ce3+ 5d → 4f transition under X-ray irradiation and two thermoluminescence (TL) glow peaks related to the shallow and deep electron traps. Although fading of the TL and OSL signal was observed due to electron release from the shallow traps, the electrons captured by deep traps were stable at room temperature. Particularly, GC samples annealed at 750 °C and 800 °C, named GC750 and GC800, showed stable OSL up to 10 h following β-ray irradiation, after an initial fading mainly due to the presence of shallow traps in the material. From the viewpoint of this fading ratio, GC750 and GC800 showed potential as a practical OSL dosimeter.

Inter-comparison of optically stimulated luminescence (OSL) ages between different fractions of Holocene deposits from the Yangtze delta and its environmental implications

In fluvial and deltaic environments, different grain-size fractions experience varying degrees of bleaching of OSL signals due to variations in hydrodynamics and depositional processes. This has led to ambiguity for selection of grain-size fraction suitable for OSL dating. Comparison of OSL results from multiple grain-size fractions is one approach to ensure the reliability of OSL ages. We determined the quartz OSL ages of four grain-size fractions from fine silt to sand, together with the single grain OSL sensitivity in a Holocene sediment core from the Yangtze delta. For samples from the lower part of the sediment succession (including tidal river, tidal trough fill, estuarine front, tidal sand and delta front facies), OSL ages determined for different grain-size fractions were generally mutually consistent within the age range of ~2–9 ka, implying minor portion of incompletely bleached grains in the sediment at the time of burial. In contrast, significant partial bleaching was observed for three samples from younger delta front facies deposited during 0.4–0.6 ka. In these three samples, fine-silt quartz OSL ages were overestimated by ~0.5–2.0 ka compared with ages of coarser fractions. Based on the investigation of quartz luminescence sensitivity, we suggest that the southward shift of the Yellow River and increasing erosion in the Yangtze River catchment have led to enhanced water turbidity, resulting in partial bleaching of the sediment and substantial overestimation of the quartz OSL ages of fine silt during 0.4–0.6 ka. Alternatively, the erosion of older deposits and their redeposition elsewhere could retain large residual OSL ages. Notably, fine-silt quartz provides reliable ages for the period of 9–2 ka, suggesting that there was a lower degree of water turbidity compared with that since 2 ka. Therefore, the degree of OSL age overestimation may provide an indication of changes in water turbidity and sedimentary environment. Overall, our findings highlight the complexity of OSL dating in delta environments, and that an understanding of sediment transport and depositional processes is critical for reliable OSL dating.

Extending the age limit of quartz OSL dating of Chinese loess using a new multiple-aliquot regenerative-dose (MAR) protocol with carefully selected preheat conditions

Abstract Optically Stimulated Luminescence (OSL) dating on quartz is well established following the introduction of the Single-Aliquot Regenerative-dose (SAR) protocol. Despite its widespread use, it has a major drawback in frequently underestimating the age of samples with equivalent dose (De) larger than ~120 Gy. In this study, we investigate fine-grained quartz extracted from Chinese loess with fairly well known ages. For these samples, we determined that the Des obtained using the standard SAR protocol (i.e., with preheat and cut-heat temperatures of 260 °C and 220 °C respectively) significantly underestimated the expected burial doses larger than 100 Gy. The dependence of OSL intensity on preheating conditions was investigated using both natural and bleached aliquots. Both the natural and regenerative OSL intensities increase with the preheat temperature to a maximum at ~260 °C and decrease afterwards. However, the regenerated OSL intensity demonstrates a greater variability compared to the natural one. This difference in variability could not be corrected by the test dose OSL responses when a standard SAR protocol was used. A simple multiple-aliquot regenerative-dose (MAR) protocol with a carefully selected preheating condition can resolve the problem of inadequate sensitivity correction between the natural and subsequent regenerative cycles. The growth of the MAR dose-response curve (DRC) was in good agreement with the sensitivity-corrected natural OSL signals up to ~340 Gy, which extends the upper age limit of quartz OSL samples of Chinese loess back to at least 110 ka.

Synthesis, RL and OSL characterization of thulium doped NaMgF3 neighborite

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

First reliable chronology for the Early Khvalynian Caspian Sea transgression in the Lower Volga River valley

During the late Quaternary, dramatic changes in relative sea level (~170 m) are known to have occurred in the Caspian Sea. However, all previous attempts at resolving the uncertainty associated with the timing of these transgressive/regressive events, primarily using radiocarbon, have produced inconclusive or controversial results. Here we present the first reliable chronology for the largest known transgression (Early Khvalynian). This was derived using optically stimulated luminescence (OSL) analysis of sand‐sized quartz, with support from infrared stimulated luminescence (IRSL) from K‐rich feldspar grains, all extracted from 16 sediment samples collected along the Lower Volga River. These samples were taken from loessic sediments, marine clays (known as Chocolate Clays) and the overlying modern soils exposed at three sections (Srednyaya Akhtuba, Raygorod, Leninsk) ~200 km upstream of the present‐day estuary. The differential bleaching rates of the quartz OSL and feldspar IRSL signals were used to evaluate the degree of resetting of quartz (and feldspar) signals; it was possible to conclude that all signals, and particularly quartz OSL, were sufficiently reset at deposition to allow accurate age estimation. Our results show unambiguously that the Early Khvalynian marine Chocolate Clays present at all three sections were deposited post‐LGM, between ~17 and ~13.1 ka ago. These age estimates are further constrained by those from the overlying Kastanozem soils (9.6–0.7 ka) and underlying loess‐soil series (32–19 ka), confirming a young (17–13 ka) age of the transgressive stage of the Early Khvalynian. Relative sea level during this period must have been well above the sampling altitudes of 11.7 m a.s.l. (Srednyaya Akhtuba), 11.3 m a.s.l. (Raygorod) and 4.7 m a.s.l. (Leninsk) to explain the absence of significant alluvial sand and to allow the deposition of the fine Chocolate Clays marker horizon.

Optically Stimulated Luminescence Signal Resetting of Quartz Gouge During Subseismic to Seismic Frictional Sliding: A Case Study Using Granite‐Derived Quartz

AbstractAttempts to determine the age of faulting recorded by fault rocks have been made using K–Ar, fission‐track, electron spin resonance, and luminescence dating methods. Here we report the unambiguous reduction (resetting) of optically stimulated luminescence (OSL) signals of quartz gouge after friction experiments and estimate the seismological and geological conditions required for OSL signal resetting in natural fault zones. In the experiments, we used quartz sand with a particle size of <150 μm and equivalent dose of 31.5 ± 16.6 Gy. Friction experiments were conducted with a rotary‐shear, high‐velocity friction apparatus at slip rates (V) of 200 μm s−1 to 1.3 m s−1, normal stress of 1.0 MPa, and displacement of 10 m. In the experiments conducted under dry conditions, the OSL signal starts to decrease from V = 0.25 m s−1 and becomes near zero at V ≥ 0.65 m s−1. OSL signal resetting is also observed in the experiment sheared at 1.3 m s−1 under water‐added conditions. At V = 0.25 and 0.40 m s−1, partial resetting occurs, which is characterized by coexistence of particles with and without an OSL signal. OSL signal intensity shows a strong correlation with applied power density and frictional heat during high‐velocity friction, and the signal exponentially decreases with increasing power density and temperature. The power density required for partial and complete OSL signal resetting is ~0.17 and 0.6 MW m−2, respectively. Assuming a co‐seismic fault slip rate of 0.6 m s−1, the depths required for partial and complete resetting are expected to be ≥11 and ≥42 m.

Investigation of luminescence properties of BeO ceramics doped with metals for medical dosimetry

Abstract The objective of this work was to investigate the luminescence properties of metal-doped BeO optical ceramics that were efficiently synthesized by the co-precipitation method in the presence of air. BeO nanophosphors individually doped with metal elements: Al, Ca, Mg, Na, Li, K, B, Si, Zn, Sr, In, and Cu in different dopant concentrations (0.1, 0.5, 1 and 5%). The phase formation and morphology of the samples were studied using x-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. The formation of the hexagonal wurtzite phase of BeO was confirmed by XRD data and SEM images showed that BeO ceramics exhibit different surface morphologies and have a narrow size distribution. Similar broad UV emission bands between 200 nm and 450 nm were observed in radioluminescence (RL) analyses of the single-metal doped BeO ceramics. The effect of metal doping on thermoluminescence (TL) and optically stimulated luminescence (OSL) signals were investigated to achieve a promising BeO dosimeter for medical dosimetry applications. While Al, Na, K, B, and Zn dopants increased the intensities of sensitivities of TL peaks responsible for traps settled up to 300 °C, Ca, Mg, K, B and In dopants significantly increased the intensities of higher-temperature TL peaks located between 300 and 650 °C. There was, in addition, an increase in OSL signal intensity of undoped BeO material with Na, Li, K, and Cu dopants by 47%, 37%, 18%, and 28%, respectively. To investigate the feasibility of the dosimetric utility of the studied BeO materials, dose-response, reusability, and fading properties of the promising ceramic dosimeters were investigated in medical applications.

NaCl pellets for prospective dosimetry using optically stimulated luminescence: Signal integrity and long-term versus short-term exposure

Optically stimulated luminescence (OSL) signal properties of pellets from three types of NaCl (two household salts and one analytical grade salt) were investigated for their use in prospective dosimetry. Special attention was given to the OSL signal behaviour with time. The readout protocol was optimised in terms of preheat temperature, and the OSL signal yield of the NaCl pellet with time as well as the fading of the OSL signal with time was investigated. The effects of acute and chronic irradiations were compared. Irradiations and readout were performed using a Risø TL/OSL reader (TL/OSL-DA-15, DTU Nutech, Denmark). The optimal preheat temperature was determined to be 100 ºC, yielding OSL signals similar to a 1 h pause before OSL signal readout. There was no OSL signal fading observed as a function of time, but a decrease in the OSL signal yield of the NaCl pellets with time resulted in an apparent inverse fading when converting the OSL signal to an absorbed dose. For chronic radiation exposures of up to five weeks, the sensitivity of the NaCl pellets was found to be stable. The results of this study show that the use of NaCl pellets for prospective dosimetry is a promising, cost-effective, and accessible complement to commercially available alternatives for accurate absorbed dose determinations.

Measurement of the paleodose in luminescence dating using the TM-OSL of quartz

The optically stimulated luminescence (OSL) of quartz is widely used in luminescence dating and retrospective dosimetry. The signal exploited up to now in measurement protocol is complex. It is hard to check by standard measurements whether the fast component which is the most appropriate for the age estimation dominates in the total OSL signal. Recently, a new method called thermally modulated OSL (TM-OSL) was developed which allows the selective detection of the OSL components. The new measurement protocol called SAR TM-OSL uses only the fast OSL component to estimate the age. The shape of TM-OSL curve makes possible to distinguish aliquots whose OSL signal is not dominated by the fast OSL component at the first stage of the dating protocol. The new protocol is 30% more time consuming, but it can be easily optimized by stimulation with more powerful LEDs than those used in current experiments.

The potential of portable luminescence readers in geomorphological investigations: a review

AbstractThe development of functional portable optically stimulated luminescence (OSL) readers over the last decade has provided practitioners with the capability to acquire luminescence signals from geological materials relatively rapidly, which allows for expedient preliminary chronostratigraphic insight when working with complex depositional systems of late Quaternary age. Typically, when using the portable OSL reader, infrared (IR) or blue post‐IR OSL signals are acquired from bulk unprocessed materials, in contrast to regular luminescence dating, which is usually based on measurements on pure quartz or feldspar mineral separates, or on select silt‐sized polymineralic portions. To demonstrate the utility of portable OSL measurements, this paper outlines the basic features of portable OSL readers and their constraints. Subsequently, case studies in which the instrument has been used to elucidate cryptostratigraphic variations in sedimentary sequences for geomorphological applications are reviewed. The studies can generally be grouped into three main categories. The first includes studies where the variation of portable OSL reader luminescence signal intensities with depth are plotted to generate profiles that contextualize sediment stratigraphy. In the second group, portable OSL reader luminescence signal intensities are used to interpret sediment processes that shed light on depositional histories. In the last category, luminescence signals from the portable OSL reader are calibrated to approximate numerical burial ages of depositional units. The paper concludes with a discussion of possible future directions. © 2020 John Wiley & Sons, Ltd.

Feasibility of determining Entrance Surface Dose (ESD) and mean glandular dose (MGD) using OSL signal from BeO dosimeters in mammography

Mammography technique is based on imaging of human breast using low-x ray energies. The main purpose of mammography is to detect breast cancer and prevent deaths related to it. The breast is made up mainly of two types of tissue; one is fat and the second is glandular tissues which is the most sensitive tissue to radiation. The Mean Glandular Dose (MGD) is used to monitor the dose received by the breast during breast imaging procedures that use ionizing radiation, and could be associated to the risk of radiation induced cancer. The MGD cannot be measured directly but can be determined using measurements of the Entrance Surface Air Kerma (ESAK) at the breast surface and conversion factors calculated from Monte Carlo simulations. Beryllium oxide (BeO) dosimeters, which exhibit properties such as nearly tissue-equivalence, fast annealing protocol, easy to read in Optically Stimulated Luminescence (OSL) technique and low-cost commercially availability, has been attractive for radiation dosimetry. In this work, Entrance Surface Dose (ESD), Backscatter Factor (BSF) and MGD values were determined with BeO OSL, for polymethyl methacrylate (PMMA) phantoms of different thicknesses. This study is the first attempt in the literature to determine dosimetric quantities used in mammography, such as ESD and MGD using BeO dosimeters. Similar measurements were performed with TLD-100 dosimeters and ionization chamber and all results were compared with each other. The results for MGD are in good agreement both between each other and with EUREF protocol within error limits. BeO shows a linear response as a function of ESAK for values between 1.0 and 12.0 mGy. Good reproducibility, within 5%, of BeO OSL signal was observed when exposed to mammography X-ray beams. It is concluded that BeO dosimeters could be considered as an alternative dosimeter to determine MGD in mammography.

Study on intrinsic defects and copper doping in LiAlO2 crystal from combined first-principles and thermodynamic calculations

A large OSL (optically stimulated luminescence) response from copper replacing lithium (CuLi) in lithium aluminate (LiAlO2, LAO) has been reported in earlier studies, and the origin of the OSL response was isolated CuLi. However, other trapped-hole centers that are not involved in OSL response, such as CuLi–VLi and STH (self-trapped hole center, a hole localized at O ion adjacent to VLi), also appear in LiAlO2:Cu crystal after irradiation. To reach optimum OSL response of LAO crystal, a comprehensive analysis that integrates first-principles and thermodynamic calculations is employed to investigate the relative stability of intrinsic defects and Cu defects. Defect formation energies (DFE) of these defects are obtained from density functional theory (DFT), as well as corrected by finite-size corrections (FNV). To find the region of Fermi level where the crystal maintains electrical neutrality, we combine DFEs as a function of Fermi level for Cu defects and intrinsic defects to discuss the charge compensation mechanism. Then, the definite DFEs for these defects and the energetically preferred sites for substitutional Cu ions are shown after determining the locations of Fermi levels under different conditions. In O-rich conditions, the results show that CuAl is most stable with the decrease of the chemical potential of Al. Furthermore, CuLi is energetically preferred under O-poor conditions, and DFE of isolated CuLi is much lower than other Cu defects, thus, the optimum OSL signal occurs. To validate our conclusions, we also present the deformation charge density to study the chemical bonds of Li–O, Al–O, CuLi–O and CuAl–O. The results also suggest that it would cost more energy to destroy Al–O bond than Li–O bond.

On the production of the medium component in quartz OSL: Experiments and simulations

Optically stimulated luminescence (OSL) production of the medium component was investigated using a coarse-grained quartz sample from Australia. Analysis of OSL decay curves measured at different stimulation temperatures revealed that there was strong interaction between the initial occupancies of fast and medium OSL components. Preheating experiments showed that the thermal stability of the medium OSL component was almost the same as that of the fast OSL component. These results suggested that both the fast and medium OSL components originate from the same source trap. The production of the medium OSL component was simulated using a kinetic model in which the medium OSL signal was originated from the 325 °C TL trap and the relevant charge is retrapped in the 170 °C TL trap due to the phototransfer effect. A good match between measured and simulated OSL decay curve was achieved.

Optical characterization of LiF:Mg,Cu,P – Towards 3D optically stimulated luminescence dosimetry

The introduction of radiotherapy beam delivery with high spatial modulation, including spot-scanning proton therapy, calls for development of 3D dosimeters for patient-specific treatment verifications. Inherently reusable methods like optically stimulated luminescence (OSL) pose a potential way to introduce a clinically viable 3D-dosimetry solution. Here we present a characterization of the OSL properties of the well-known thermoluminescence material LiF:Mg,Cu,P (MCP). The characterization was performed by monitoring the wavelength-dispersed emission of continuous-wave stimulated MCP pellets. We show that OSL emission is observed under blue (460 nm) and green (532 nm) laser stimulation, while no OSL signal is seen in MCP under red (664 nm) laser stimulation. Long-wavelength fluorescence including accumulating radiophotoluminescence is very intense under blue stimulation and must be suppressed for continuous use of a future 3D-dosimetry system. An evaluation of the number of emitted photons is used to estimate a measurable dose range of 0.1–10 Gy, which prompts further research in the use of MCP for 3D OSL-based dosimetry.

An alpine meadow soil chronology based on OSL and radiocarbon dating, Qinghai Lake, northeastern Tibetan Plateau

Extensive alpine meadow soil on the Tibetan Plateau (TP) plays a core role in the local ecological system, however, its ages of formation and pedogenic processes are relatively poorly understood. In this study, we reconstructed a soil development chronology for two alpine meadow soil sections on Riyue Mountain, southeast of Qinghai Lake (QHL), using quartz optically stimulated luminescence (OSL) and potassium-rich feldspar (K-feldspar) post-infrared infrared stimulated luminescence (post-IR IRSL, pIRIR) techniques. In addition, accelerator mass spectrometry 14C analysis of soil organic matter (SOM) was used to date alpine meadow soil profiles on Xiangpi Mountain, southwest of QHL. Bulk samples were collected from Riyue Mountain profiles for determination of soil grain size and magnetic susceptibility. The results show: (1) Consistency of quartz OSL and K-feldspar pIRIR ages, indicating both the quartz OSL and K-feldspar pIRIR signal for alpine meadow soil samples are well bleached before burial. (2) SOM radiocarbon ages most likely underestimate sample age due to modern organic contamination from plant roots. (3) A lower limit on alpine meadow soil development after the last deglaciation based on OSL dating of bottom deposits, and an upper limit of before 1450 ± 80 cal BP from radiocarbon dating of the upper SOM; alpine meadow soils developed mainly during the late Holocene (4–0 ka) on the mountains around QHL. (4) The grain size characteristics of alpine meadow soil are similar to atmospheric dust and loess at QHL; the rapid aeolian accumulation in the late Holocene implies conditions of relative arid and cold climate.