Portable Optically Stimulated Luminescence Reader Research Articles

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.

Assessing paraglacial processes at Nexpayantla Gorge (Popocatépetl volcano, Central Mexico) using OSL and14C

AbstractWe evaluate the paraglacial activity in Nexpayantla, a subtropical mountainous gorge in Popocatépetl volcano (Central Mexico), fully deglaciated in the 20th century. Glacial advances are evidenced by the presence of moraines. Fluvio‐glacial terraces and an alluvial megafan resulted from the gorge deglaciation. Current reworking of the glacigenic material is done by landslides and debris flows produced on the moraines and terraces. To study the different phases of mobilization of glacigenic sediment, we used an approach based on the study of the optically stimulated luminescence (OSL) signals obtained from a portable OSL (POSL) reader in samples extracted from both glacigenic and paraglacial deposits. The luminescence (POSL) results obtained at moraines increase as altitude decreases, which is expected for deglaciated valleys where the oldest moraines are located at lower elevations. We evaluate the grade of luminescence signal reset of the glacigenic sediments during the proglacial stage, and the subsequent deglaciation phases. Our results indicate that there is a marked transition between glacial and fluvially dominated processes at Nexpayantla Gorge. We find that the grade of luminescence signal resetting in the paraglacial deposits is a good indicator to trace paraglacial stages and the beginning of exhaustion of the paraglacial activity in mountain areas. OSL ages confirm that the oldest fluvio‐glacial terraces found at the middle sector of Nexpayantla Gorge are ~2 ka, which is also supported by an AMS14C age. OSL dating was found challenging, since quartz grains have low sensitivity because of their volcanic origin; POSL signals, however, are in good agreement with the location and distribution of geomorphic markers. We propose that luminescence data obtained from the POSL unit can be useful to provide information about sediment mobilization in paraglacial environments during different climatic pulses – even for the case where mineral grains have low sensitivity, such as in volcanic sediments. © 2020 John Wiley & Sons, Ltd.

Using portable OSL reader to obtain a time scale for soil accumulation and erosion in archaeological terraces, the Judean Highlands, Israel

Abstract Current conventions on the fate of agricultural bench terraces in the mountainous Mediterranean climatic zones, assume that after abandonment terraces undergo rapid degradation and soil loss. First walls crumble, followed by soil washed out of breaches in the walls by runoff, resulting in rapid erosion of soil from the slopes downhill into the streams. Additionally, soil erosion may explain why previous optically stimulated luminescence (OSL) dating of terrace soils in the Judean Highlands, Israel, found mostly young soils dating to the past 700 years, and only occasionally were older ages obtained for soils at the very base of these terraces. In contrast, observations made in the same region show that slopes with degraded terraces appear to still retain much soil even though only faint remains of the terraces exist. To test if terraces and soils indeed erode entirely and how long this might take, a relatively smooth hill slope showing remains of highly degraded sets of terraces was studied. Samples were collected from excavated pits for full OSL dating, in addition to samples densely collected for OSL measurements using a portable OSL reader (PR). Air-born photogrammetry was used to obtain high spatial resolution Digital Elevation Model. Results show that the main body of terraces was first built ∼800 years ago and maintained until 175-100 years age when they were abandoned and subsequently degraded. Since then 30–45% of soil volume was lost to erosion, however steady-state was reached at a relatively high slope of 65%, with stabilization by vegetation. The thick soil present on most of the slope suggests that after the first stage of rapid degradation the slopes reache equilibrium, most likely due to vegetation that reduces direct soil erosion, so most of the soil is retained on the slope. Finally, the PR allows for a much more nuanced understanding of terrace soil history.

Luminescence dating of cyclone-induced washover fans at Point Lefroy (NW Australia)

Reliable age dating of coastal sedimentary landforms is crucial for inferring storm frequencies and magnitudes from geological archives. However, in highly energetic coastal settings, radiocarbon dating is often biased by reworking and/or poorly constrained marine reservoir effects. Due to this, most cyclone-driven sediment archives from the semiarid coast of NW Australia – a region frequently affected by tropical cyclones but with a historical record limited to ∼150 a, and therefore strongly in need of long-term data inferred from geological evidence – are affected by chronological inaccuracies. Optically stimulated luminescence dating (OSL) may overcome these shortcomings by dating the transport of sediment directly. In turn it may be related to other challenges when applied to cyclone deposits from semiarid environments. The cyclone-induced washover fans at Point Lefroy, NW Australia, are composed of a heterogeneous mixture of coral fragments, shell hash and siliciclastic sand. This makes them particularly prone to high dose scatter resulting from a combination of partial bleaching, sediment mixing and dose-rate heterogeneity. The washover fans are further characterised by a discontinuous nature of cyclone deposition, as indicated by erosional features and macroscopic brunification horizons. By using a combination of quartz single grain dating, autoradiography, alpha counting and gamma spectrometry, sediment mixing and dose rate heterogeneity are identified as the main sources of dose scatter. The resulting chronology allows us to discriminate at least four well constrained phases of washover fan activity at ∼180, ∼360, ∼870, and ∼1300 a ago. Older but less well constrained activity phases occurred ∼1950, ∼2300, and ∼2830 a ago. While these phases of increased cyclone activity correlate with depositional units separated by potential palaeosols, OSL ages, quasi-continuous portable OSL reader measurements and gamma spectrometry measured with increased sampling resolution point to deposition of distinct washover units within a very short period of time. However, unambiguous discrimination between deposition of individual units by single events and deposition by several cyclones within periods of only a few decades is currently not possible.

Feasibility of dosimetry with optically stimulated luminescence detectors in magnetic fields

The objective of this study was to analyze the applicability of optically stimulated luminescence detectors (OSLDs) for dosimetry in magnetic resonance (MR) guided radiation therapy devices with focus on dose dependence and angular dependence on the magnetic field strength.Precise detectors for dosimetry in high magnetic fields for such devices are still subject to research. In contrast to ionization chambers, OSLDs contain no air cavities, such that only minor changes in detector response with increasing magnetic field strengths are expected.To study the behavior of OSLDs in magnetic fields, Al2O3:C detector packages were irradiated at a 6 MV linac in a water phantom, while magnetic fields between 0.0 T and 1.0 T were applied. In order to study the angular dependence, the OSLD packages were rotated around the vertical axis for three different magnetic field strengths (0.0 T, 0.5 T, 1.0 T). Additionally, the angular dependence was measured at a clinical 0.3 T 60Co device. The OSLDs were read out using a portable OSL reader and an automated Risø TL/OSL-DA-15 reader.Readout with the portable reader yielded package standard deviations of 1–2% and revealed no significant relation between dose response and magnetic field strength, while readout with the Risø reader resulted in standard deviations of only 1% and a significant decrease in response of −1.3% per T (95%-confidence interval: −1.9% to −0.7%). The angular dependence was not significantly influenced by the magnetic field. The small decrease in dose response supports the applicability of the OSL technique in MR-guided radiation therapy devices. We expect that no additional magnetic field correction factor has to be used when a calibration of the detectors in the magnetic field of such a device is performed.

Landscape preservation under post‐European settlement alluvium in the south‐eastern Australian tablelands, inferred from portable OSL reader data

AbstractHuman land‐use changes leading to widespread erosion and gully incision have been well studied, but the effects that erosion and sediment mixing, which accompany the deposition of post‐(European) settlement alluvium (PSA), have in valley bottoms and wetlands receive considerably less attention. PSA overlying pre‐disturbance swampy meadow (SM) wetland sediments is commonly exposed along incised stream channel gully walls throughout the south‐eastern Australian Tablelands, providing an ideal setting in which to assess and understand better how PSA deposition affects valley bottoms and the wetland environments that often occupy them. Portable optically stimulated luminescence (pOSL) reader data were measured on bulk sediment samples from SM‐PSA stratigraphies at 16 locations throughout the south‐eastern Australian Tablelands to assess the effects of erosion and sediment mixing at the SM‐PSA boundary. Trends of pOSL data with depth at each profile were used in conjunction with visual profile descriptions to identify the stratigraphic boundary between SM and PSA sediment and to infer the degree of valley bottom erosion and sediment mixing during PSA deposition. At most sites, SM sediments experienced minimal, if any, disturbance during PSA deposition, and we refer to these as non‐eroded sites. Many sites, however, experienced a significant degree of erosion and sediment mixing – eroded sites – often corresponding to visually diffuse sedimentary boundaries between the two stratigraphic units. Our findings demonstrate that SM landscapes in the Tablelands can be preserved with minimal disturbance under PSA at non‐eroded sites and are preserved beneath a mixing zone at all eroded sites. Copyright © 2016 John Wiley & Sons, Ltd.

Using three different approaches of OSL for the study of young fluvial sediments at the coastal plain of the Usumacinta–Grijalva River Basin, southern Mexico

AbstractWe use three different approaches of optically stimulated luminescence (OSL) to study young fluvial sediments located at the main channels of one of the largest fluvial systems of North America: the Usumacinta–Grijalva. We use the pulsed photo‐stimulated luminescence (PPSL) system also known as portable OSL reader, full OSL dating and profiling OSL dating in samples extracted from vertical sediment profiles (n = 9) of riverbanks to detect changes in depositional rates of sediments and to obtain the age of the deposits. The results of the PPSL system show that the luminescence signals of vertical sediment profiles highly scattered from the top to the bottom contrast with the luminescence pattern observed on well‐reset sequences of fluvial deposits where luminescence increase from the top to the bottom of the profile. The profiling and full OSL ages yielded large uncertainty values on their ages. Based on the inconsistencies observed in both ages and luminescence patterns of profiles we suggest that these fluvial deposits were not fully reset during their transport. As an explanation, we propose that in the Usumacinta and Grijalva rivers the cyclonic storms during the wet season promote the entrainment of large volumes of sediments due to high‐erosional episodes around the basin resulting from hyper‐concentrated and turbid flows. We conclude that the PPSL, profiling and full OSL dating of sediments are useful tools to quantify and to assess the depositional patterns in fluvial settings during the Holocene. These techniques also can yield information about sites where increases in the sediment load of rivers may produce poorly resetting of grains affecting the results of OSL dating. Copyright © 2015 John Wiley & Sons, Ltd.

SU‐C‐16A‐02: A Beryllium Oxide (BeO) Fibre‐Coupled Luminescence Dosimeter for High Dose Rate Brachytherapy

Purpose:Beryllium oxide (BeO) ceramics have an effective atomic number, zeff ∼7.1, closely matched to water, zeff ∼7.4. The purpose of this study was to evaluate the use of a beryllium oxide (BeO) ceramic fibrecoupled luminescence dosimeter, named RL/OSL BeO FOD, for high dose rate (HDR) brachytherapy dosimetry. In our dosimetry system the radioluminescence (RL) of BeO ceramics is utilized for dose‐rate measurements, and the optically stimulated luminescence (OSL) can be read post exposure for accumulated dose measurements.Methods:The RL/OSL BeO FOD consists of a 1 mm diameter × 1 mm long cylinder of BeO ceramic coupled to a 15 m long silica‐silica optical fibre. The optical fibre is connected to a custom developed portable RL and OSL reader, located outside of the treatment suite. The x‐ray energy response was evaluated using superficial x‐rays, an Ir‐192 source and high energy linear accelerators. The RL/OSL BeO FOD was then characterised for an Ir‐192 source, investigating the dose response and angular dependency. A depth dose curve for the Ir‐192 source was also measured.Results:The RL/OSL BeO FOD shows an under‐response at low energy x‐rays as expected. Though at higher x‐ray energies, the OSL response continued to increase, while the RL response remained relatively constant. The dose response for the RL is found to be linear up to doses of 15 Gy, while the OSL response becomes more supralinear to doses above 15 Gy. Little angular dependency is observed and the depth dose curve measured agreed within 4% of that calculated based on TG‐43.Conclusion:This works shows that the RL/OSL BeO FOD can be useful in HDR dosimetry. With the RL/OSL BeO FODs current size, it is capable of being inserted into intraluminal catheters and interstitial needles to verify HDR treatments.

Rapid equivalent dose estimation for eolian dune sands using a portable OSL reader and polymineralic standardised luminescence growth curves: Expedited sample screening for OSL dating

Portable optically stimulated luminescence (OSL) readers are robust devices that allow rapid determination of luminescence signals of polymineralic coarse-grained samples. To date, however, the utility of portable OSL readers has largely been confined to the construction of luminescence profiles that depict variations of luminescence signal intensities with depth. Because the luminescence signals used to construct such profiles are uncalibrated, it is neither practical to quantitatively compare portable OSL data from different sites nor is it possible to approximate sample ages. Such comparisons could be facilitated by converting portable OSL signals into equivalent doses (De). However, determining De requires the construction of unique growth curves for each sample; a laborious procedure that negates the rapidity associated with portable measurements. To circumvent that limitation, we construct standardised growth curves (SGCs) using normalized regeneration dose signals obtained using a portable OSL reader from the feldspar component of polymineralic sands from five disparate eolian dune sites in Alberta, Canada. Comparison of SGCs from different samples indicates general congruence and we merge these to construct a regionally applicable curve which we test by comparing the De obtained from given samples with that obtained using conventional OSL dating protocols. Results show that, though the uncertainties associated with the portable OSL data are high, the De values from the two approaches are linearly proportional. This direct variation enables portable OSL SGC De values to be used independently in reconnaissance studies that aim to screen samples for more detailed analysis using standard OSL methods. The affordability of portable OSL readers suggests that the approach could be attractive to researchers who do not have ready access to conventional OSL readers.

Using OSL to assess hypotheses related to the impacts of land use change with the early nineteenth century arrival of Europeans in south‐eastern Australia: an exploratory case study from Grabben Gullen Creek, New South Wales

ABSTRACTA common explanation for intense soil erosion and gullying in SE Australia is the introduction by Europeans of new land use practices following their arrival in Australia in the late 18th century. Eucalyptus woodlands were cleared to introduce farming, and valley bottoms, characterized by chains of ponds with organic‐rich swampy meadow (SM) soils, were subsequently buried by thick deposits of ‘post‐settlement alluvium’ (PSA) generated by erosion in the catchment. In this study, optically stimulated luminescence (OSL) is used to evaluate the source(s) of the PSA in Grabben Gullen Creek (GGC), Australia. We use a portable OSL reader to measure total photon counts on bulk polymineral and polygrain‐size samples from nine profiles along the Creek. We use these luminescence signals as geotracers of sediment source(s) and transport pathways. We obtained higher luminescence signals in the PSA than in the SM sediments, suggesting different sources and fluvial transport conditions for these two widespread sedimentary units. Portable OSL reader data from soils in the GGC catchment that are potential sources for the SM sediments and PSA show that the high luminescence signals recorded in the PSA are similar to those from subsoil samples in granite soils, suggesting that the PSA was derived by gullying of granite subsoils. In the SM sediments, luminescence signals decrease upwards from the base of the profile, as expected in well‐reset fluvial deposits, but with one or more changes in gradient in the profile of photon counts with depth, most likely indicating changes in sediment deposition rates. To calculate deposition rates in the SM sediments, several samples were dated using OSL. The OSL ages produced low scatter in the equivalent doses, confirming the well‐reset nature of the grains composing the SM and indicating a process of sediment transport in dilute flows, as is interpreted from the portable OSL signals. Copyright © 2014 John Wiley & Sons, Ltd.

Determining the Applicability of the Landauer nanoDot as a General Public Dosimeter in a Research Imaging Facility

The Research Imaging Institute (RII) building at the University of Texas Health Science Center at San Antonio (UTHSCSA) houses two cyclotron particle accelerators, positron emission tomography (PET) machines, and a fluoroscopic unit. As part of the radiation protection program (RPP) and meeting the standard for achieving ALARA (as low as reasonably achievable), it is essential to minimize the ionizing radiation exposure to the general public through the use of controlled areas and area dose monitoring. Currently, thirty-four whole body Luxel+ dosimeters, manufactured by Landauer, are being used in various locations within the RII to monitor dose to the general public. The intent of this research was to determine if the nanoDot, a single point dosimeter, can be used as a general public dosimeter in a diagnostic facility. This was tested by first verifying characteristics of the nanoDot dosimeter including dose linearity, dose rate dependence, angular dependence, and energy dependence. Then, the response of the nanoDot dosimeter to the Luxel+ dosimeter when placed in a continuous, low dose environment was investigated. Finally, the nanoDot was checked for appropriate response in an acute, high dose environment. Based on the results, the current recommendation is that the nanoDot should not replace the Luxel+ dosimeter without further work to determine the energy spectra in the RII building and without considering the limitation of the microStar reader, portable on-site OSL reader, at doses below 0.1 mGy (10 mrad).

Delineating stratigraphic breaks at the bases of postglacial eolian dunes in central Alberta, Canada using a portable OSL reader

ABSTRACTTemporal constraints for the Late Pleistocene deposition of eolian dunes that occur in central and northern Alberta, Canada can be provided by dating sediments from the dune bases using luminescence techniques. In places, however, the postglacial dunes overlie glaciofluvial sands that resemble the eolian deposits in texture such that demarcating the bases of the dunes is often problematic. In this study we address the problem by employing a portable optically stimulated luminescence (OSL) reader to construct luminescence profiles that depict luminescence signal variation with depth. With the portable OSL reader, measurement can be performed on bulk sediments, negating the need for laborious separation procedures to isolate pure mineral fractions, as is required in regular luminescence dating. Measurements can also be carried out in the field, permitting quicker decision making during sample collection. Results from this study, presented as depth variations of feldspar derived infrared stimulated luminescence (IRSL) signals and predominantly quartz‐generated post‐IR blue OSL signals, show that luminescence profiling enables one to distinguish between eolian deposits that make up the dunes from the underlying non‐eolian sands. The identification of such cryptostratigraphic interfaces is made possible by differences in the dosimetric histories of the sediments. The delineation of the dune bases allows targeted sampling that yields best luminescence age approximations for the initiation of postglacial eolian deposition in the region. Luminescence profiling of eolian sequences would also, in theory, permit the identification of depositional breaks of extended duration. Copyright © 2012 John Wiley & Sons, Ltd.

Sedimentological processes in lahars: Insights from optically stimulated luminescence analysis

A lahar is a sediment-laden flow capable of major destructive impacts on infrastructure and human life. How lahars transport sediment is thus a key issue for understanding lahar sedimentology and behavior, especially in terms of the lahar's hydraulic and rheological properties, which can be substantially altered as the lahar gains or loses material during its travel. In this research, we analyze lahar entrainment processes by evaluating luminescence signals (total photon counts) from lahar sediments using blue luminescence signals (BLSL). A portable OSL reader that analyzes several grams of polymineral and polygrain-size samples was applied. We use data from three lahars in the Tenenepanco and Huiloac gorges on Popocatépetl volcano (Mexico) to elucidate the ways in which lahars may gain, lose and transport sediment during flow. Sediment samples for luminescence analysis were taken through the full thickness of the lahar deposits at eight different sites for two lahars (1997 and 2001) and at one site for a lahar that occurred > 500 yrs ago. Mean luminescence values obtained for the 1997 lahar help to evaluate the relationship between the lahar entrainment processes and the drainage at the different sites. For the 2001 lahar this relationship was also established taking into account the channel slope. The main conclusion is that luminescence signals (total photon counts) can be used to detect entrained material in the flow because the bulked materials modify the final OSL signals. The application of this type of luminescence analysis thus has the potential to provide a better understanding of sediment entrainment in these sediment-laden flows.

Interpreting luminescence data from a portable OSL reader: three case studies in fluvial settings

AbstractOptically stimulated luminescence (OSL) is a technique that has been applied from the mid‐1980s, mainly for sediment dating. The OSL technique is based on sample stimulation by light to determine the luminescence signal that is stored in the crystal lattices of sediment grains after deposition, burial by later sediment and subsequent exposure to ionizing radiation from radioactive elements in the surrounding sediment. In such sediment dating, two parameters are required: the equivalent dose (i.e. the luminescence signal stored in the grains), and the dose rate (i.e. the ionizing energy from α, β and γ radiation emitted by naturally occurring radioisotopes in the deposit, plus the effects of cosmic radiation). In this research, the OSL technique is not used for dating. The study goal is to analyse only the luminescence signals (the total photon counts) in polymineral samples obtained after light stimulation in the blue (BLSL) and infrared (IRSL) wavelengths using a portable OSL reader designed and built at the Scottish Universities Environmental Research Centre (SUERC). Three fluvial case studies – from Cambodia, Australia and Mexico – are used to illustrate the geomorphological interpretations possible with the portable OSL reader data from sediments resulting from a range of different depositional processes. The case studies show that aspects of sediment's transport and depositional processes can be inferred from the portable OSL reader data, providing valuable insights into geomorphological history. Copyright © 2010 John Wiley & Sons, Ltd.

A portable multi-purpose OSL reader for UV dosimetry at workplaces

Optically stimulated luminescence (OSL) techniques are used for environmental radiation monitoring, luminescence dating and retrospective dosimetry. A portable and robust field instrument has been developed for the routine assessment of occupational exposure to ultraviolet (UV) radiation at workplaces. The design principles of hard- and software are described, along with preliminary measurements that illustrate the operation of the system and its capabilities.

Recent instrumental developments for trapped electron dosimetry

We review our continuing investigation and development of new facilities for irradiation, optical stimulation and luminescence signal detection. These facilities are aimed for use in luminescence-based retrospective dosimetry, and in investigations of luminescence processes. We describe progress in (i) the development, testing and documentation of mini X-ray generators as an alternative to 90Sr/ 90Y beta sources, (ii) the development of a pulsed-OSL unit as an attachment to the Risø TL/OSL reader, which has made it possible to achieve real-time separation of the quartz signal from a mixed sample, (iii) the measurement of red emission TL from natural samples for increasing the age range, (iv) the design of a compact portable OSL reader for direct dose measurements in the field and finally (v) fitting an electron detector to a Risø reader for measuring both thermally and optically stimulated exo-electrons to give insight into luminescence processes.

Disaster and generosity

Mineral Resources (DMR). We particularly thank the Director-General of the DMR, Mr Somsak Potisat, and the DMR's Chief of Foreign Affairs, Mr Sommai Techawan, for their support. We also thank the Royal Society of Edinburgh for an award under its International Exchange Programme for NC to visit Scotland for discussions on our joint OSL work. Simon Murphy (SUERC) and Peter Chung (University of Glasgow) provided invaluable assistance in building the portable OSL reader and/or measuring samples.