Optically Stimulated Luminescence Signal Research Articles

A Tissue‐Equivalent, Reusable Dosimeter for 3D Verification of Radiotherapy

AbstractA new tissue‐equivalent, reusable material for dosimetric verification of radiotherapy is developed and characterized. The material comprises a hydrogel matrix containing copper‐doped lithium fluoride nanoparticles that exhibit optically stimulated luminescence (OSL). Using a laser light sheet and a sensitive camera equipped with appropriate filters, the OSL signal is read out layer by layer thus constructing the 3D dose distribution. The good tissue equivalence allows the new material to register the dose from a prescribed treatment plan as if delivered to a patient. Cubic dosimeters measuring 50 × 50 × 50 mm3 are developed and used to measure 3D dose distributions (from voxels measuring 0.8 × 0.8 × 1.0 mm3) with a statistical dose precision of 5% at 100 Gy dose levels. The spatial precision of offsets in dose gradients between planned and measured dose distributions is below the voxel size. A 3% / 3 mm gamma analysis between a prescribed treatment plan and the retrieved and corrected readout yields a pass rate of 89.5%. Light scattering within the dosimetric volume affects the dosimeter performance, indicating the potential for future improvements of spatial and dose precision. In conclusion, the dosimeter system shows high promise for future clinical validation of radiotherapy.

Structural, vibrational, and luminescent properties of pure and Ce-doped magnesium lithium aluminoborate glass

The objective of this work was to study the properties of new vitreous samples of pure BAlMgLi and Ce-doped BAlMgLi produced by the melt-quenching method. The structural and vibrational characteristics of the samples were analyzed using x-ray diffraction (XRD), vibrational Raman spectroscopy, and vibrational Fourier transform infrared spectroscopy (FTIR). Optically stimulated luminescence (OSL) and thermoluminescence (TL) techniques were also used to identify whether the samples showed a response to ionizing radiation. XRD analyses confirmed the predominance of the amorphous phase of the samples. The Raman spectra revealed that the atomic bonds present in the material matrix are of the pyroborate and metaborate type, enabling stretching vibrations in isolated BO4 and/or Al–O or Al–O–B units. The band at approximately 810 cm−1 is characteristic of the formation of the boroxol ring, indicating that the presence of other elements in the matrix does not affect its glassy characteristics. The FTIR analyses reinforce the results found by Raman spectroscopy, because bands characteristic of low hygroscopic glasses were observed, due to the conversion of BO3 units into BO4 in triborate, tetraborate, and pentaborate groups. This conversion is due to dopant entrainment, which contributes to the high optical transparency of the samples. Their OSL and TL signals were reproducible with intensities dependent on the dopant concentration and radiation dose, with the most intense emissions resulting from 0.5% Ce concentrations.

Effect of optical stimulation temperature on the TA-OSL background and signal

The impact of readout temperature on background during optically stimulated luminescence (OSL) measurement is reported in this study. The background signal on un-irradiated phosphors has been found to increase significantly with readout temperature for the samples studied in this work, Al2O3:C and CaSO4:Dy. This increase in background signal with rising stimulation temperature on un-irradiated phosphors may overlap with the thermally assisted OSL (TA-OSL) signal. This phenomenon was observed only in the case of phosphors and not with bare stainless steel (SS) discs/planchets, and hence, this background emission should not be confused with blackbody radiation. Moreover, the reported background emission was seen to be much larger than the blackbody radiation. Although the TA-OSL signal does increase with temperature, it does not increase proportionally to the background signal. Therefore, to determine the net increase in TA-OSL due to the rise in readout temperature, the increase in background signal should be taken into consideration.

Light-induced fading effects on TL and OSL signals and feasibility of dose re-assessment with PTTL signals in BeO dosimeters

Abstract This study aims to investigate both light-induced fading effects on thermoluminescence (TL) and optically stimulated luminescence (OSL) signals under three different light sources (fluorescent, UV-254 and daylight) and dose reassessment with phototransferred TL (PTTL) signals in Beryllium oxide dosimeters. TL and OSL signals were deconvoluted for each light source. Accordingly, variations in the maximum peak temperature, activation energy, peak area value for the TL signal, and intensity and lifetime values for the OSL signal were monitored. Each peak, OSL component, and total area value exhibited different behaviors depending on the light source. Considering the total area condition, the TL intensity decreased by ∼90%, ∼80%, and ∼70% in UV-254, daylight, and fluorescent light exposure, respectively, at the end of the 120 min. On the other hand, the OSL total area intensity faded quickly for both UV-254 and daylight, while it decreased by ∼45% for fluorescent light. According to these results, regardless of TL and OSL measurements, the dosimeters should be kept primarily away from daylight and fluorescent light after irradiation, instead of UV-254, which is rarely encountered in daily life. The feasibility of dose reassessment using PTTL signals under UV-254 light was investigated within a wide dose range from 0.1 to 128 Gy. It is feasible to reassess doses between 0.5 and 32 Gy considering the total area intensity of PTTL signals. In conclusion, PTTL signals can be easily used in fields of the order of Gy, such as in reevaluating doses in radiotherapy applications.

Ce-doped magnesium borate glass-ceramic for optically stimulated luminescence dosimetry

Despite intensive research in optically stimulated luminescence (OSL) dosimetry, the number of materials with suitable properties for practical application remains limited. Among these, magnesium tetraborate (MgB4O7) has attracted attention as a potential host because of its effective atomic number, similar to those of water and living tissues, and the possibility of producing neutron-sensitive material by controlling the content of the 10B isotope. Specifically, Ce-doped MgB4O7 has been proposed as a promising OSL material for 2D dosimetry because of its rapid luminescence. While the literature on polycrystalline sintered MgB4O7:Ce is extensive, the objective of this work is to produce this material in glass-ceramic form, offering many advantages such as excellent formability into complex shapes, rapid mass production, easily controlled microstructure, and higher density (zero porosity) compared to conventional powder-sintered materials, potentially leading to dosimetric improvements. This paper describes the synthesis route and the effects of various thermal treatments of magnesium borate glass and the resulting glass-ceramics, along with their fundamental dosimetric properties. The samples heat-treated at 814 °C for 3 h (GC814) exhibited the most intense and stable thermoluminescence peaks, accounting for their lowest signal fading among the investigated treatment conditions. However, during the OSL readout, diminished intensity was observed. Analysis of the GC814 emission spectrum revealed TL peaks predominantly outside the used optical filter's primary transmittance range, likely contributing to the OSL signal reduction. Regardless of the thermal-treatment condition, all the samples presented excellent repeatability of the OSL response, with standard deviations ranging from 0.1 % to 0.7 %, underscoring the advantages of glass-ceramics over sintered ceramics. From step-annealing analysis, an optimal preheat treatment temperature was identified, and the activation energy of the three main peaks was determined. The encouraging results indicate the potential of this glass-ceramic as a practical OSL dosimeter and justify further investigation to optimize its OSL properties.

OSL and radiocarbon dating of core TBF-1 on the outer shelf of the East China Sea and implications for late Quaternary stratigraphic correlation

It is crucial to establish a robust chronology for understanding late Quaternary sedimentation processes and environment changes in response to sea-level fluctuation on shelves. The shelf of the East China Sea (ECS) is featured by huge terrigenous sediment input and striking land -sea interaction during the late Quaternary. However, there remains controversy in chronostratigraphic rebuilding of transgression and regression deposits during eustatic-glacial cycles, mainly due to a lack of reliable dating data. In this study, an extensive comparison of 17 optically stimulated luminescence (OSL) and 15 AMS 14C ages from core TBF-1 (upper 40 m) provides a constraint in chronostratigraphic reconstruction since Marine Isotope Stage (MIS) 5. OSL ages range from 9.5 ± 0.7 to 67.3 ± 4.8 ka at depths from 2.00 to 28.00 m, while 14C ages range from 6645 to 41435 cal a BP at depths from 0.02 to 17.52 m. Regression analysis demonstrates a high level of agreement between OSL and 14C ages, with r2 values of 0.91 and 0.90, respectively. For Holocene sediments (U1), both OSL and 14C methods are applicable in tidal sand ridges, however, it should be noted that 14C ages may exhibit a young bias of up to 3 ka. For pre-Holocene sediments (U6-U2), OSL ages are robust within saturation limitation of OSL signal (De up to ca. 166 Gy), cross-checked by feldspar post-IR IRSL (pIRIR) dating protocol. Nevertheless, the shell 14C ages (11620 and 10390 cal a BP at depths of 13.95–14.56 m) in Last Glacial Maximum (LGM) fluvial sediments of U2 are significantly underestimated, because of their susceptibility to recrystallization and overgrowth, resulting in carbon exchange with environment. While the peaty layer's14C age in deltaic deposition (17.50 m, U5) was determined to be 36420 cal a BP, coincided with OSL age of 39.6 ± 3.9 ka. The chronostratigraphy since MIS 5 for core TBF-1 exhibits a significant correlation with previously published cores SFK-1, DZQ4, and DH02, on the ECS outer shelf. Through the evaluation of those underestimated 14C ages and saturated OSL ages, we re-elucidated the primary sedimentary facies and their respective formation periods. This sedimentary stratigraphic illustration exhibits significant consistency with eustatic-glacial cycles. The renewed chronological framework for ECS shelf allows better correlation between the late Quaternary sedimentary evolution and the land-sea interaction on open shelves dominated by siliciclastic sedimentation.

Further investigation of spatially resolved single grain quartz OSL and TL signals

The use of luminescence signals from single mineral grains for optical dating has become a valuable and frequently utilised tool in Quaternary Geochronology. Single grain luminescence dating is particularly beneficial in complex depositional settings, however the ability to measure single grain signals also offers the opportunity to assess intrinsic luminescence properties of individual mineral grains. The use of spatially resolved luminescence technologies such as an electron multiplier charge coupled device is of benefit when making luminescence measurements at single grain scales because they allow stimulation with light emitting diodes, and this offers a number of key benefits related to stimulation power when it comes to the assessment of characteristics such as optically stimulated luminescence (OSL) decay rate and the calculation of parameters such as the fast ratio and photo ionisation cross-sections. In this paper, the intra- and inter-sample variability of sensitised single grain thermoluminescence (TL) and OSL signals is considered. A comparison between TL and OSL signals is undertaken, as well as calculation of the fast ratio, OSL component photo ionisation cross-sections, thermal stability, and characteristic dose for a suite of quartz samples from a range of geographic locations and depositional settings. For these heated signals, key findings include the lack of relationship between OSL signal intensity and dominance of the fast component, the fitting of two components (a fast and slow component) is the most common fit for single grain OSL signals, characteristic doses from fast dominated signals suggesting saturation at c. 150 Gy, and the identification of the ultrafast OSL component. Intra-sample variability across all measured parameters is observed, suggesting that for this suite of samples, variability is the norm rather than the exception, and that the intrinsic luminescence characteristics of quartz are variable and diverse.

OSL dosimetry with table salt for mass screening of individual doses during radiological or nuclear emergencies

The ongoing war in Ukraine is associated with unprecedented radiological threats to the public in Ukraine and the neighboring countries. This calls for fundamental revision of the preparedness plans and established approaches to radiological monitoring of the populations affected by potential radiological emergencies. Dosimetric information will be needed for triage of victims and support to decision makers for prioritizing mitigation actions. Retrospective dosimetry methods strive to find a solution that would achieve this and enable fast and accurate feedback with information on individual doses to the concerned public. All known approaches to emergency dosimetry, both in biological and physical (instrumental) dosimetry have limitations, in particular – preventive cost, limited availability of samples for analysis, insufficient sensitivity (high dose threshold) and/or stability of radiation-induced markers (i.e. high fading). At the moment each of considered dose assessment methods possesses some combination of the aforesaid limitations. A suggestion to overcome these deficiencies is to use ordinary table salt (NaCl), read by optically stimulated luminescence (OSL), with well-known good dosimetric properties, and which allows anybody to prepare improvised individual dosemeters at home to be carried like a regular personal dosemeter until readout of the OSL signal is possible. This paper considers pros and cons of the use of NaCl as an OSL dosemeter in an emergency situation, with emphasis on practical aspects of its application for mass dose assessments for individuals among populations affected by radiological emergency situations.

Multi-method luminescence dating of young aeolian dunes in the central Tibetan plateau

The environment of the Tibetan Plateau (TP) is extremely sensitive to global climate change, and the frequent aeolian activity on the central TP generates large amounts of dust with the result that the region has a major impact on regional and global environmental change. The extensive aeolian dunes on the central TP provide a direct and valuable archive of aeolian activity; however, the age and sediment deposition processes of these dunes are still poorly understood. Optically stimulated luminescence (OSL) dating, an effective method for dating aeolian sediments, has been used sparingly in the region. In this study, we applied quartz single-aliquot regenerative-dose (SAR) OSL, K-feldspar post-infrared infrared-stimulated luminescence (pIRIR), and single-grain K-feldspar pIRIR methods to determine the ages of two well-preserved sand dunes in the Lunpola (LD) and Tuotuohe (TTH) river basins in the central TP. Our results showed that the quartz OSL signal of the TTH dune was dim, while the LD dune quartz exhibited a higher OSL sensitivity than that of the TTH dune. The high recuperation observed could be attributed to the low signal-to-noise ratio of the OSL signals. The K-feldspar signal was bright and the pIR50IR170 signal could be used to date young dune samples in the central TP, whereas it could be affected by the residual dose, or incomplete bleaching in the TTH profile, resulting in age overestimation. The single-grain K-feldspar protocol had a good potential for dating the young TP dunes. Multi-method luminescence dating is recommended for the cross-checking of young dune samples with low OSL sensitivity in the TP. Our luminescence dating reveals that aeolian dunes in the central TP formed approximately 385 to 330 a and persisted to the present, possibly in response to climate change since the late stage of Little Ice Age (1400−1850 CE).

Investigating luminescence signals of pharmaceuticals and dietary supplements for emergency dosimetry

This study investigates the potential use of dietary supplements and pharmaceuticals containing magnesium, calcium or potassium for emergency dosimetry applications using the phenomenon of optically stimulated luminescence (OSL). Signal measurements were carried out using different stimulation wavelengths, and blue light stimulation was found to be the most efficient. More than half of the samples exhibited a measurable OSL signal and relatively high radiation sensitivity compared to other previously measured emergency detectors. Moreover, samples generally demonstrated a linear dose response. Possible causes of their high zero-dose signal were investigated: mechanical processing and UV light excitation. As variability in sensitivity was observed, the test-dose protocol was used during measurements. Furthermore, the study showed a significant loss of OSL signal intensity within 24 h after irradiation, which suggests the necessity for a fading correction. Finally, a dose recovery test was performed to evaluate the materials and the test-dose protocol under realistic conditions. The findings indicate the potential for using pharmaceuticals and dietary supplements in the event of a radiation emergency due to their dosimetric properties and ease of obtaining.

Single grain pIRIR dating of glacigenic deposits in the Yuzhu Peak area of Kunlun Mountains of Tibetan Plateau revealed the glaciations during Holocene period

The variations of glaciers in the Kunlun Mountains of the northern Tibetan Plateau are influenced by the complex interaction of the East Asia summer monsoon (EASM), Indian summer monsoon (ISM) and Westerlies, as well as human activity during the Holocene period. Consequently there is ongoing debates regarding the evolution of glaciers and the factors driving their changes. The reconstruction of glacial evolutions in these regions has been hindered by insufficient chronological data for moraines and other glacial landforms. In this study, glacial sediment samples were collected from five moraine sequences located on the southern and northern slopes of the Yuzhu Peak in the Kunlun Mountains. These poorly bleached moraine samples were dated using the single-grain quartz optically stimulated luminescence (OSL) and K-feldspar post-infrared infrared stimulated luminescence (pIRIR) dating methods. The luminescence characteristics analysis of quartz grains shows that single grain quartz OSL dating cannot be used to date Holocene moraine samples due to the low brightness of quartz OSL signals. Various tests were conducted to assess the reliability of K-feldspar pIR50IR170 dating, including anomalous fading tests, dose recovery, and residual dose tests. The K-feldspar pIR50IR170 ages, determined using the Minimum Age Model (MAM), indicate that during the early Holocene, glaciations have expanded by ∼800 m in length at ∼ 8 ka, and during the end of the Neoglacial period, they extended by ∼200 m in length at ∼ 1 ka. The strengthened ISM precipitation and northward movement of ISM boundary likely contributed to the glacial expansion in the early Holocene. During the end of the Neoglacial period, the increase in westerlies precipitation and cold events may have played a role in the advancement of glaciers.

Extending the ESR and OSL dating comparison on coastal dune deposits from the Wilderness-Knysna area (South Africa)

Our work follows up on the initial methodological ESR dating study by Ben Arous et al. (2022) on several quartz samples from the Plio-Pleistocene to Holocene aeolian coastal dune deposits of the Wilderness-Knysna area (South Africa) that were previously dated by optically stimulated luminescence (OSL). Here, we extend this first ESR-OSL comparison with five additional optically-bleached quartz samples. We used the Multiple Aliquot Additive Dose (MAAD) method to specifically (i) evaluate the influence of the irradiation dose steps on the determination of low De values (<100 Gy) and (ii) obtain finite ESR ages for older samples that sometimes show saturated OSL signals. Following the Multiple Centre ESR dating approach, the Aluminium (Al) and Titanium (Ti) signals (Ti–H and Ti–Li–H, the latter resulting from a mixture of Ti centres) were systematically measured in all samples, and resulting De values and age estimates were compared with the corresponding OSL data. Our results show that for young samples (<50 ka) showing De values of a few tens of Grays (Gy), the use of smaller irradiation steps spaced by < 100 Gy has a noticeable impact on the MAAD dose evaluation from the Ti centres, usually leading to De results closer to the expected values (for 2/3 samples). However, this also makes the ESR measurements somewhat more challenging, with higher experimental uncertainties, lower measurement repeatability and lower goodness-of-fit resulting from the relatively weak Ti ESR intensities, ultimately impacting the robustness of the ESR data collected. In this sense, our study illustrates the limitations of the ESR method to detect very low dose irradiation values < 30 Gy with our experimental conditions (i.e., using MAAD procedure, a standard resonator and a measurement temperature of ∼90 K). On the contrary, it also highlights the greater potential of the Ti–H signal to date Late Pleistocene samples, confirming previous studies. Moreover, our results suggest that the transport and bleaching conditions of these aeolianite deposits may not be ideal for the reset of the radiation-induced Al and Ti ESR signals, which is consistent with the very few existing studies specifically focused on this type of samples, but contrasts with other previous dating applications centered on fluvial environments. Finally, we also provide additional chronological constraints to the Landward barrier complex and Coversands deposits, two of the oldest Plio-Quaternary formations in the Wilderness-Knysna area.

Using quartz OSL signals from SAR cycles for sediment provenance studies

Quartz optically stimulated luminescence (OSL) sensitivity is varied and related to Earth surface processes and, thus, it has been shown to be a useful tool for appraising sediment recycling and provenance investigations. These investigations are mainly based on OSL data purposely measured for sensitivity calculations. However, it has been recently shown that the relative sensitivity of the quartz OSL fast component (%BOSLF) from the first test dose (Tn) signal from an OSL dating measurement using the Single Aliquot Regenerative-dose (SAR) protocol can be used to discriminate sediment sources. Here, we investigate the possibility of characterizing %BOSLF for provenance purposes using not only Tn signals but all other OSL signals obtained over SAR protocol cycles from OSL dating measurements. We address the %BOSLF behaviour over SAR cycles (if conservative or not), the %BOSLF dependency on dose-size, differences between %BOSLF values given by natural/regenerative and test dose signals, and %BOSLF application for provenance studies. Quartz sand grains data from twenty Late Quaternary sediment samples, representing orogenic and cratonic sources and diverse depositional contexts from South America, Africa, and Asia, are included in the analysis. All calculations were performed using data that have been previously obtained for equivalent dose estimation. The key finding is that the averaged %BOSLF of all SAR signals was representative of the samples' characteristic sensitivity and could satisfactorily discriminate samples from known sources, mainly in the case of high-sensitivity samples. We could distinguish sediment source areas by averaging the %BOSLF of OSL signals from SAR natural/regenerative and test doses together. Likewise, laboratories worldwide could produce regional/global sediment provenance fingerprinting reference data using their dating measurements accumulated throughout the last decade.

Development of CaSO4:RE,Li (RE = Tm, Eu, Tb) composites for thermally or optically stimulated luminescence dosimetry

This work proposed the development of CaSO4:Tm,Li, CaSO4:Tb,Li and CaSO4:Eu,Li composites for application in radiation dosimetry, using luminescent techniques such as thermoluminescence (TL) and optically stimulated luminescence (OSL). The CaSO4 crystals were produced by the adapted slow evaporation route and characterized using X-ray diffraction (XRD), TL and OSL techniques. XRD analyses showed that the doped CaSO4 samples presented a single phase. The CaSO4:Eu,Li composites showed TL signals with peaks around 145 °C and 180 °C. The CaSO4:Tb,Li and CaSO4:Tm,Li composites showed TL signals with peaks centered at 165 °C and 275 °C. For the CaSO4:Tb and CaSO4:Tm samples, the addition of lithium as co-dopant resulted into a significant increase (2x) in the total TL signal of the samples. The CaSO4:Tm,Li samples presented a very intense OSL signal, about 80x greater than the signal of the other samples produced. This allows the applicability of TL/OSL detectors even more sensitives. The TL emission spectra of the samples showed typical emissions of Eu2+ ions (280 nm), Eu3+ (614 nm), Tb3+ (544 nm) and Tm3+ (455 nm). No emission corresponding to lithium was identified. All the samples produced showed linearity in the dose range used and good reproducibility, with variations below 10%. The CaSO4:Tm,Li samples showed the lowest limit of detection and fading. The evaluated dosimetric characteristics denote that these developed composites have potential application as TL/OSL detectors.

Limitations of quartz extracted from Antarctica sediments for luminescence dating

Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) properties of quartz samples extracted from soil of Fisher Island (76° 13ʹ 23.9ʺ E, 69° 23ʹ 31.9ʺ S) in Antarctica were studied. The nature of signals indicated presence of a dominant slow component in the OSL signal. The widely utilized Single Aliquot Regenerative (SAR) protocol for dose recovery was found unsuitable for this particular sample due to the dominating slow component in the OSL signal. Efforts to minimize the effect of slow component in dose recovery by adopting procedures like, bleaching with blue light, and early background subtraction were carried out. Additionally, thermally transferred OSL (TT-OSL) studies were conducted on the natural sample and dose estimation using the TT-OSL SAR protocol was carried out.

Chronology of late Holocene sediments related to the Qicheng ruins in central China

The Qicheng city wall is located in Puyang, Henan Province, China, and it is an important archaeological site from the Neolithic period in the North China Plain region. A trench across the northwest corner of the city wall revealed an 11 m thick sediment sequence, closely associated with human activities, which provides valuable records for the dating and environmental evolution of the site. In this study, we have applied field geological investigation, grain size analysis, optically stimulated luminescence (OSL) dating, and radiocarbon (14C) dating to reveal the history and changes in the site. The ancient city wall was built on the sedimentary sequence (U1) of the high terrace of the Ancient Yellow River. The upper 11 m thick sedimentary sequence (U2) recorded early moat sedimentation (U2L) and was followed by three cycles of paleosol-flooding deposits (U2U). The quartz OSL signals of the U2 silts are extremely bright, indicating high sensitivity. Partial bleaching was observed as well. The quartz OSL single-grain SAR dating results are consistent with that of charcoal 14C dating and are closer to the ‘true’ burial ages of the sediments than those obtained with multiple grains. By using a Bayesian statistical model, a chronological framework for the U2 sedimentary sequence was established. The earliest construction date of the Qicheng city wall is dating to 2100–1300 BC, during the late Longshan period, which is consistent with archaeological evidence (Li et al., 2015). The Qicheng city was not significantly affected by paleo-flooding prior to 870–960 AD, but experiences frequent flooding thereafter.

A formation record of modern Nitraria tangutorum nebkhas on the Ordos Plateau of northern China based on optically stimulated luminescence dating

Nebkhas, as special biologically mediated aeolian landforms, play an important role in indicating regional aeolian activities and aeolian environmental changes. The Ordos Plateau is located in arid and semiarid regions of northern China that have a wide distribution of Nitraria tangutorum nebkhas. There are few chronological records of nebkha formation, so the history of the formation and evolution of nebkhas in the plateau is still unclear. In addition, the optically stimulated luminescence (OSL) dating method, which has been widely used in the dating of Holocene aeolian sediments, has not yet been applied to the dating of nebkha sediments in the Ordos Plateau. In this study, OSL methods were used to discuss the formation age and relevant aeolian activities of Nitraria tangutorum nebkhas in the Ordos Plateau. The results demonstrated that (1) the coarse-grained quartz OSL signals of nebkha sediments were insensitive and thus were inapplicable by the single aliquot regenerative (SAR) protocol. (2) The luminescence characteristics of the K-feldspar fraction and internal checks of the post-infrared infrared-stimulated (pIRIR) dating indicated that the pIR50IR170 protocol with 200 °C of preheating was applicable for De determinations of nebkha sediments. (3) The residual doses of the pIRIR170 signals ranging from 0.02 to 0.14 Gy should be considered when calculating De values. (4) Bayesian age-depth models were used for the Nitraria tangutorum nebkha sedimentary sequences. The formation of nebkhas occurred during a relatively dry climate period accompanied by strong aeolian activity. That ∼0.38 ka was the main growth period of Nitraria tangutorum nebkhas. This study is the first report of the formation age of nebkhas of more than one hundred years in the region.

Luminescence and thermometry studies of plant opal phytoliths

We have investigated the luminescence properties of plant opal phytoliths to assess their suitability for determination of age and/or thermometric information from soil and sediment sequences. This study examined a <2.37 gcm−3 density fraction in parallel with quartz grains from samples collected from alluvial terraces. We observed comparable optically stimulated luminescence (OSL) from the phytolith fraction to the quartz, and thermoluminescence (TL) with broader peaks and continuum to higher temperatures. Scanning electron microscopy (SEM) data suggested the presence of opal clasts and contaminant minerals. To better understand the luminescence from opal phytoliths we analyzed a suite of biogenic materials including very pure diatoms, phytoliths, and quartz reference materials. We observe low sensitivity but measurable OSL signals in all the materials analyzed, and infrared stimulated luminescence (IRSL) signals with fast decay rates exceeding those of more typical feldspars in some of the purer materials. TL signals are similar to those observed for glasses and suggests dose response might extend beyond quartz saturation levels. Preliminary investigations of OSL dose response show very promising growth characteristics for opal phytolith samples and all other biogenic silica materials analyzed.

Fading performance on optically stimulated luminescence of LiMgPO4:Tb,Sm,B

This study aimed to investigate the fading of the optically stimulated luminescence (OSL) of LiMgPO4:Tb,Sm,B. Thermoluminescence (TL) glow curves were recorded immediately and 24 h after irradiation, as well as after OSL. Peaks 2 and 3 did not contribute to the fading of the TL signal, while peak 1 was identified as the primary source of TL signal fading in LiMgPO4:Tb,Sm,B. The fading was calculated by considering the OSL signal measured immediately after irradiation as the first measurement point. About 70% of the OSL signal was measured 30 days after irradiation if the pre-heat procedure was not applied. The intensity of LiMgPO4:Tb,Sm,B remains stable at 93.1% with a preheating program of 160 °C for 30 s.

Chronology by luminescence and radiocarbon on core sediments from the northeastern pearl river plain and implications for delta process

Accurate dating is the basis for deciphering eustatic and climatic changes on deltaic sedimentary processes. In the Pearl River Delta (PRD) plain of south China, scarce robust chronology hinders the detailed interpretation of sedimentary history. In this study, quartz optically stimulated luminescence (OSL) (21 samples), feldspar post-IR IRSL (pIRIR) (4 samples) and radiocarbon (14C) (2 samples) dating were applied to obtain detailed chronological framework of core SXG06 (23-m long to bedrock) from the northeastern PRD. SXG06 consists an upper marine unit (M1) and a lower marine unit (M2), separated by a terrestrial unit (mottled clay, T1). For M1, quartz OSL and 14C samples yielded ages from 5.2 ± 0.3 to 0.32 ± 0.02 ka. The sample on top of T1 produced a quartz OSL age of 35 ± 2 ka. For other 12 samples in T1 and M2, quartz OSL signals reached saturation and generated minimum ages (>51 ka). For these the saturated quartz OSL samples, feldspar pIR50IR250 provides an age range of 123 ± 7–105 ± 7 ka. The compilation of all the above ages and previous sedimentology data reveals that: (1) M2 was formed during marine transgression of Marine Isotope Stage (MIS) 5; (2) A hiatus with an age gap of between ∼35 ka and ∼5 ka was observed, which might be due to the low sea level and resultant weathering scouring; (3) Initial M1 deposits from the northeastern PRD postdated the central and southern PRD by ∼3 ka, indicating delayed delta development in the northeastern PRD during the Holocene. (4) SXG06 experienced slow deposition 0.3 m/ka in ∼5–3 ka because of the coevally decreased sediment supply, followed by accelerated deposition rate of 3 m/ka after ∼3 ka associated with strengthen human activity.