Or Optically Stimulated Luminescence Research Articles

Absorbed doses in bricks and TL-dosimeters due to anthropogenic and natural environmental radiation sources

Radiation doses accumulated in ceramic or brick and assessed by thermoluminescence (TL) or optically stimulated luminescence (OSL) measurements are commonly used as a source of independent dosimetric information, helpful for validation of retrospective estimates of population exposures to anthropogenic radiation sources. This work systematically evaluates contributions to the cumulative dose in brick samples located at different heights in a wall from anthropogenic and natural radiation sources and provides data for quantification of the natural background component of the total dose in the brick derived in TL/OSL-measurements. Al- and Cu-cased thermoluminescence dosimeters (TLD) based on Al2O3:C are used to measure contemporary doses in brick walls as benchmarks and for validation of the dose reconstruction procedures. Correspondingly, doses in TLD and in brick in the same locations and under the same irradiation conditions are obtained by Monte Carlo simulations of radiation transport in realistic geometries. The data obtained in the simulations indicate that energy response of Al-cased dosimeters agrees better with the energy response of the brick than the response of Cu-cased TLD. The dosimetric data and relationships between doses in TLD and in brick are systematically derived for different locations in the wall and above the ground and used in other dose reconstruction studies with luminescence techniques.

U-Th age distribution of coral fragments from multiple rubble ridges within the Frankland Islands, Great Barrier Reef: Implications for past storminess history

Prograded coral rubble ridges have been widely used as archives for reconstructing long-term storm or storminess history. Chronologies of ridge systems in previous studies are often based on a limited number of low-resolution radiocarbon or optically-stimulated luminescence (OSL) ages per ridge (usually only one age per ridge), which carry intrinsic age uncertainties and make interpretation of storm histories problematic. To test the fidelity of storm ridges as palaeo-storm archives, we used high-precision U-Th dating to examine whether different samples from a single ridge are temporally constrained. We surveyed three transects of ridge systems from two continental islands (Normanby Island and High Island) within the Frankland Islands, Great Barrier Reef (GBR), and obtained 96 U-Th dates from coral rubble samples collected from within and between different ridges. Our results revealed significant differences in age ranges between the two islands. The steeper and more defined rubble ridges present on Normanby Island revealed that the majority of U-Th ages (over 60%) from a single ridge clustered within a narrow age range (∼100 years). By contrast, the lower and less defined ridges on High Island, which were more likely formed during both storm and non-storm high-energy events, revealed significant scatter in age distribution (>>200 years) with no notable clustering. The narrower age ranges obtained from the steeper and more defined rubble ridges suggest that previous approaches of using either limited samples from a single ridge or low-precision dating methods to establish chronologies are generally valid at centennial to millennial timescales, although caution must be taken to use such approaches for storm history reconstruction on shorter timescales (e.g. decadal). The correlation between U-Th mortality ages of coral rubble and historical stormy periods highlights the possibility of using coral rubble age distribution from rubble ridges to reconstruct the long-term regional storminess history. U-Th age distribution of all dated coral rubble samples, combined with previously published storm-transported coral block data from the same region, revealed at least six relatively stormy periods in the past 500 years in the Frankland Islands region: 1570–1590, 1760–1780, 1800–1830, 1860–1880, 1940–1960, 1980–2010 CE. Wavelet power analysis of the relative probability of U-Th age distribution indicates that the Pacific Decadal Oscillation (PDO) and El Nino-Southern Oscillation (ENSO) may be partially responsible for the long-term variability in storminess.

Formation of the Yalong Downstream Terraces in the SE Tibetan Plateau and Its Implication for the Uplift of the Plateau

AbstractThe Yalong River is an important river that runs across the abruptly changing terrain of the SE Tibetan Plateau. The terraces and Quaternary sediments in its valleys preserve the information of tectonic uplift, climate changes, and landform evolution since the Middle Pleistocene. Based on geomorphological, sedimentological, and chronological investigations, 6–8 terraces are identified in the lower reaches of Yalong catchment and its tributary—the Anning River. The electron spin resonance (ESR) or optically stimulated luminescence (OSL) data on the alluvial sediments in the upper portion of terraces indicate that they formed in 1.10, 0.90, 0.72, 0.06–0.04, 0.03–0.02, and 0.01 Ma. Tectonic uplift and the climatic cycle controlled the formation of the Yalong River terraces. The former dominated the dissection depths and incision rates, whereas the latter controlled the transformation between accumulation, which developed during the glacial period, and incision, which developed during the glacial‐interglacial transition. The Yalong downstream incised rapidly from 1.10 to 0.72 Ma and rapidly from 0.06 Ma until the present; the terraces developed during these two periods. The incision rates in space during the two periods indicate the uplifting extent of the Jinpingshan area, which decreases toward the east and the south. The results reveal two rapidly uplifting stages in the SE Tibetan Plateau, including an accelerated uplifting since 0.06 Ma. Since the Middle Pleistocene, the tectonic uplift of the SE and NE parts of the Tibetan Plateau is synchronous, according to the same development stages of the river terraces of the Yalong downstream and the Yellow River in the Lanzhou area of the NE Tibetan Plateau. The difference in the horizontal displacement between the Xianshuihe Fault and the Anninghe Fault bend resulted in the rapid uplift of the Jinpingshan area. The incision rate for the spatial distribution of the Yalong downstream is the geomorphological response of crustal shortening and uplift differences in the SE margin block of the Tibetan Plateau. The southeastward diffusion process of the Tibetan Plateau was recorded.

Underestimated 14C-based chronology of late Pleistocene high lake-level events over the Tibetan Plateau and adjacent areas: Evidence from the Qaidam Basin and Tengger Desert

The palaeolake evolution across the Tibetan Plateau and adjacent areas has been extensively studied, but the timing of late Pleistocene lake highstands remains controversial. Robust dating of lacustrine deposits is of importance in resolving this issue. This paper presents 14C or optically stimulated luminescence (OSL) age estimates from two sets of late Quaternary lacustrine sequences in the Qaidam Basin and Tengger Desert (northeastern Tibetan Plateau). The updated dating results show: (1) the radiocarbon dating technique apparently underestimated the age of the strata of >30 ka BP in Qaidam Basin; (2) although OSL and 14C dating agreed with each other for Holocene age samples in the Tengger Desert area, there was a significant offset in dating results of sediments older than ∼30 ka BP, largely resulting from radiocarbon dating underestimation; (3) both cases imply that most of the published radiocarbon ages (e.g., older than ∼30 ka BP) should be treated with caution and perhaps its geological implication should be revaluated; and (4) the high lake events on the Tibetan Plateau and adjacent areas, traditionally assigned to MIS 3a based on 14C dating, are likely older than ∼80 ka based on OSL chronology.

TL Properties of Pure Al<sub>2</sub>O<sub>3</sub> Grown by the Micro-Pulling down Method

Carbon-doped Al2O3is used as a material for dosimeter using thermoluminescence (TL) technique or optically stimulated luminescence (OSL) technique, and the emission bands are originated from defect emission. We have an original crystal growth named micro-pulling down (μ-PD) method which had higher temperature graduation during the crystal growth. Thus, crystal defect is easy to be formed without some dopant using the μ-PD method. We grew pure Al2O3samples with different heating condition, and different peaks in TL spectra were obtained among the pure Al2O3.

The role of simulations in the study of thermoluminescence (TL)

The traffic of charge carriers in a luminescent material during its excitation by irradiation and during readout either in the measurement of thermoluminescence (TL) or optically stimulated luminescence (OSL) is governed by sets of coupled nonlinear differential equations. The analytical solution of these sets is usually not possible, and one can resort to one of two options. Some researchers preferred to make simplifying assumptions and thus got approximate solutions whereas others performed simulations by solving the simultaneous equations numerically. Each of these routes has its pitfalls. The simplifying assumptions, mainly the quasi-equilibrium assertion or the assumption that certain relations between the relevant parameters and functions hold, may be valid in certain ranges of the TL or OSL curve, and may cease to be valid, say at the high-temperature range in TL. Performing simulations using the numerical solution of the relevant set of equations may yield results which are accurate, but cannot be considered as being general because they depend on the specific choice of the parameters. Repeating the simulations with several sets of the physically plausible parameters would add credibility to the conclusions drawn. The combination of the two approaches is highly recommended, i.e, if similar results are found by approximations and simulations, the validity of the conclusions is strengthened. Evidently, the comparison of these theoretical results to experimental effects is essential. In the present work we consider the occurrence of unusually high and unusually low values of the activation energy and the effective frequency factor. In particular, we can simulate a recently discovered behavior of TL in LiF:Mg, Cu, P at the ultra-high dose range and get qualitatively the main elements of the experimentally found results.

Paleoseismic study of the east Kalpintage fault in southwest Tianshan based on deformation of alluvial fans and 10Be dating

Multiple earthquakes produced by thrusting deformation have been recorded over the last century in the Tianshan area. Paleoseismic studies are very important in the exploration of the active quaternary tectonics and the risk assessment of great earthquakes in the Tianshan orogenic region. However, in this area, paleoseismic research is still lacking because of the lack of samples dated by 14C or optically stimulated luminescence (OSL) methods. We determined the ages of the alluvial fans by 10Be terrestrial cosmogenic nuclide (TCN) dating, measured the surface deformation of the fault scarp in a GPS survey, and evaluated the vertical displacements of the events in trenches in the east Kalpintage fault in the southwest Tianshan region. We estimated the displacement and recurrence intervals of the paleoseismic events and constrained the errors of the 10Be ages and slip rates using a Monte Carlo simulation method. Our study suggests that each paleoseismic event shows a similar displacement of ~1.5 m with a recurrence interval of ~5 kyr in the east Kalpintage fault. The calculated slip rate is 0.31(+0.21/−0.18) mm/yr. In such arid regions with large areas of coarse gravel that lack 14C or OSL samples, the integration of TCN dating, geomorphic deformation survey, and trenching methods is a reliable alternative for studying the active regional tectonics.

Palaeoclimate in the Saharan and Arabian Deserts during the Middle Palaeolithic and the potential for hominin dispersals

To disperse out of sub-Saharan Africa, it was necessary for hominins to cross the deserts of either the Sahara and/or Arabia. Thus, understanding the palaeoclimate of the Saharo-Arabian region is central to determining the role these deserts played in the peopling of the planet; when did they act as barriers and when were they more humid, opening dispersal routes across them? To address these questions we have conducted a temporal and spatial evaluation of dated sites from 20 to 350 ka using combined probability density function (PDF) and geographical Information System (GIS) analyses of all sites dated using uranium/thorium (U/TH) or optically stimulated luminescence (OSL) methods. Radiocarbon dates were not considered because of contamination problems in this time range. The results show that during MIS 2 there is little evidence for humidity in Arabia as would be expected during the height of the last glacial maximum, however, the Sahara shows a sharp rise in probability at the beginning of MIS 2, peaking near the boundary with MIS 3 at ∼29 ka. There appear to be brief periods of humidity in MIS 3 and 6, though at different times in the Sahara (ca. 37, 44, 138, 154 and 180 ka) and Arabia (ca. 40, 54 and 163 ka). During MIS 5, both regions show much evidence for humidity, with PDF peaks corresponding to insolation maxima, though not all maxima are represented in either the Saharan or Arabian record. This situation can be explained by eccentricity-modulated precession: when eccentricity is strong, insolation is enhanced (but also more variable) and the desert climate is generally more humid, particularly at times of high insolation. The opposite happens when eccentricity is low, and deserts tend to be more arid, but local factors exert more of an influence on climate, affecting the timing and strength of the brief humid periods experienced, so that they no longer coincide with insolation maxima. The spatial distribution of humid sites is compatible with a number of different modern human dispersal theories. Southern Arabia experienced humid periods centred on 54 ka and 125 ka, and this could have facilitated dispersal from east Africa to southern Arabia and beyond via the Bab el Mandab. The Sahara shows considerable evidence for humidity during MIS 5 and may have had dispersal across its expanse at this time.

Comment on "The Clinical Features and Pathophysiology of Acute Radiation Dermatitis in Patients Receiving Tomotherapy"

Dear Editor: We read with interest the article by Lee et al.1, where a significantly more severe dermatitis was reported in patients receiving tomotherapy when compared to patients receiving radiation. However, the authors do not provide any reasons for their findings. Unfortunately, there is no information on contouring of the planning target volume (PTV); therefore, we can only speculate that grade 2 dermatitis in breast cancer patients might occur due to inclusion of voxels with low computer tomography (CT) numbers (air) as the target. Low density materials are less attenuating and require higher intensity of radiation for delivery of the same dose as to more dense tissues. If this is the case, the actual dose delivered to the surface layer might be higher than the prescription. In our institution, tomotherapy has been used clinically since September 2004, and we have not observed serious dermatitis in our tomotherapy patients, compared to conventional techniques. In order to verify the correspondence of calculated and actually delivered doses, either MOSFET dosimeters OneDose™ (Sicel Technologies, Morrisville, NC)2 or optically stimulated luminescence (OSL) dosimeters InLight® NanoDot™ (Landauer Inc., Glenwood, IL)3 are used during the first fraction of the treatment for lesions close to the surface. To stress the importance of careful contouring of the target and planning, we refer to one of our recent cases involving a 73-year-old male with a history of squamous cell carcinoma (SCC) on his scalp since 2004. He had undergone at least two surgical excisions with skin flaps in 2006 and 2008. He has had multiple recurrences of these lesions, mainly around flaps involving a large area of his scalp. The patient refused additional surgical procedures. He underwent photodynamic therapy (PDT) in 2007 for treatment of actinic keratosis of his scalp as an attempt at possible control of his SCC. However, due to skin irritation and pain from treatment, the patient did not tolerate PDT. Tomotherapy treatment was recommended in order to avoid critical organs, such as optic nerves, lens, and brain tissue. He underwent CT simulation and planning for tomotherapy treatment of his scalp lesion of 60 Gy in 1.8 Gy fractions over a period of 6 ½ weeks, resulting in the dose-volume histogram shown in Fig. 1A with good sparing of organs at risk. The PTV was contoured 2 mm below the surface in order to avoid air voxels in the target volume, as shown in Fig. 1B together with the planned dose distribution. During the course of tomotherapy, grade 1 radiation dermatitis developed after 4 weeks into treatment. The treating physician reviewed this patient during his course of treatment and recommended a skin moisturizing gel (hypo-allergenic Aloe Vera). Dry skin desquamation was observed in the irradiated area of the scalp during the last week of the therapy. He tolerated the course of the therapy without any treatment interruption. Two months after tomotherapy, the patient showed a clinically complete response, as shown in Fig. 2, and recovered from radiation dermatitis on follow-up assessment. To date, 5 months after completion of tomotherapy the patient has shown no disease recurrence. MRI of the brain showed no acute radiation effect on brain tissue. This example, with a very large superficial target, shows that careful contouring of targets close to the skin surface is necessary in order to avoid significant dermatitis. Fig. 1 (A) Cumulative relative dose-volume histogram and (B) dose distribution for the patient with large superficial target volume. GTV: gross tumor volume, PTV: planning target volume, unlabeled dose-volume histograms correspond to the right eye (purple), ... Fig. 2 Clinical photographs of the patient's scalp: (A) before and (B) 2 months after tomotherapy treatment.

Remote optical fiber dosimetry

Optical fibers offer a unique capability for remote monitoring of radiation in difficult-to-access and/or hazardous locations. Optical fiber sensors can be located in radiation hazardous areas and optically interrogated from a safe distance. A variety of remote optical fiber radiation dosimetry methods have been developed. All of the methods take advantage of some form of radiation-induced change in the optical properties of materials such as: radiation-induced darkening due to defect formation in glasses, luminescence from native defects or radiation-induced defects, or population of metastable charge trapping centers. Optical attenuation techniques are used to measure radiation-induced darkening in fibers. Luminescence techniques include the direct measurement of scintillation or optical excitation of radiation-induced luminescent defects. Optical fiber radiation dosimeters have also been constructed using charge trapping materials that exhibit thermoluminescence or optically stimulated luminescence (OSL).

Photon-stimulated luminescence of quartz from loess and effects of sensitivity change on palaeodose determination

In an attempt to improve the accuracy and precision of optical dating for loess deposits, we have measured photon-stimulated luminescence (PSL) or optically stimulated luminescence (OSL) of fine-grain quartz extracted from loess using blue–green light stimulation. The luminescence signal of quartz is shown to have three components which decay with markedly different rates upon stimulation. The preheat procedures employed during the measurements gave rise to changes in luminescence sensitivity. The sensitivity changes monitored by the 110°C TL peak and OSL responses to a test dose are shown to be dependent on factors such as preheat temperature, number of cycles and radiation doses. The preheat-induced sensitivity changes occur in both single- and multiple-aliquot based methods. We show that with an OSL sensitivity correction in the single-aliquot regeneration method, high-precision palaeodose values with uncertainty smaller than 5% can be obtained for fine-grain quartz from loess.

Infrared (IR) stimulated luminescence from modern bricks in retrospective dosimetry applications

It has frequently been observed that certain roof tiles and bricks, especially from relatively modern European buildings, do not contain enough quartz grains in a suitable grain size range to permit dose reconstruction using thermoluminescence (TL) or optically stimulated luminescence (OSL) methods. In this paper the feasibility of using infrared-stimulated luminescence (IRSL) on the feldspar fraction of such bricks and tiles has been investigated. Appropriate preheating treatments were employed in order to select the most stable signals, and procedures were developed to enhance the signal to noise ratio. The possible effect of anomalous fading under application of these procedures was tested. In the dose range above 100 mGy, it has been demonstrated that using IRSL on the feldspar fraction of such material provides a feasible alternative to the use of green-light-stimulated luminescence (GLSL) on the quartz fraction, for the purposes of retrospective dosimetry. Furthermore, since the use of IRSL as described in this paper involves the measurement of polymineral fine grain fractions of bricks, a technique for the calibration of the built-in β source against the γ source in Secondary Standard Dosimetry facilities for routine use of the technique is described.

An Integrating UVB Dosemeter System

Recent evidence of sharp increases in the number and severity of deformations in many amphibian species worldwide resulting from increased ultraviolet-B (UVB) exposure has prompted the development of a new integrating UVB dosemeter system. This dosemeter can be read out using either thermoluminescence (TL) or optically stimulated luminescence (OSL) techniques. The detection method takes advantage of the photqtransfer properties of Al 2 O 3 :C in the UVB region (280-320 nm). These UVB dosemeters have a linear dynamic range of several orders of magnitude and no significant temperature dependence. The inherent angular dependence of the interference filter has been flattened using diffusers and the increased phototransfer efficiency of Al 2 O 3 :C at shorter UVB wavelengths. The new UVB dosemeters can be used in air or in water and require no external power source. Their small, lightweight and watertight design make them ideally suited for measuring the UVB exposure of amphibian egg sacks in situ.

Comparison of ‘blue’ and ‘infrared’ emission bands in thermoluminescence of alkali feldspars

Dating quaternary sediments by thermoluminescence (TL) or optically stimulated luminescence (OSL) calls for a detailed knowledge of the luminescence of feldspars. TL of the various alkali feldspars ((K, Na) Si 3AlO 8) display many common features, and some of these cause great difficulties for dating. After long storage following ionizing irradiation, the TL of most alkali feldspars is known to fade away by “anomalous fading”, which is incompatible with dating. This effect had been attributed to tunnel recombination. Following irradiation, a very intense tunnelling afterglow is observed at temperatures down to liquid nitrogen, in accordance with the observed rate of fading. This emission has a Gaussian spectrum entirely in the infrared (IR) with a maximum at 1.7 eV. It displays an important thermal quenching from 77 to 300 K. Its intensity is related with the ‘disorder’ of the crystal lattice. At higher temperatures, in TL proper, two emission bands can be separated. One is the well-studied complex visible emission, distributed over the spectral region from UV to orange, but mostly ‘blue’. The other is the ‘infrared’ band already observed at lower temperatures, which is attributed to Fe 3+ ions. These two bands are clearly separated, with the spectral maxima, respectively, below and above 600 nm. They have also different kinetics, the glow peaks temperatures are different. But these two different bands are also coupled in many ways, they have parallel growth and fading. With ‘disordered’ feldspars, the ‘blue’ emission displays anomalous fading, which is stronger than that of the ‘infrared’. The infrared emission is more stable, which may be interesting for the purpose of dating.