Optically Stimulated Luminescence Method Research Articles

High-resolution sedimentological and stratigraphic framework for the Pehuen Co Paleoichnological site, late Pleistocene, Buenos Aires, Argentina

The Pehuen Co Paleoichnological site (Buenos Aires Province, Argentina) contains one of the more diverse and well-preserved mammal and bird fossil footprint assemblages from the Late Pleistocene. The purposes of this paper were a detailed paleoenvironmental assessment of the footprint-bearing unit (middle member of the Agua Blanca Sequence) and to date key stratigraphic surfaces to constraint the temporal development of the site. A total of twenty-two detailed sedimentological sections were measured and correlated and five sediment and fossil remain samples were dated by the Optically Stimulated Luminescence (OSL) and Electron Spin Resonance (ESR) methods, respectively. The lower part of the local sequence represents dense to dilute alluvial deposits that were pedogenized. The middle part contains an alternance of sandy sheet-flood and lacustrine mudflat deposits with sand patches of eolian origin. Most of the fossil footprints with better preservation quality were recorded in the mudflats of a shallow lake sourced by unconfined fluvial currents. The participation of eolian deposits increases up section. Locally, a sandy plain of fluvial origin is developed at the top of the section. The new OSL ages along with a previous radiocarbon date led us to propose that sedimentation of footprint-bearing levels would have extended approximately between 28.5 and 12.0 ka. Reworked marine shell remains from the lowermost levels of site with fossil footprints gave considerably older analytical ages in the range of 97.6–62.5 ka, which is probably the maximum age for the middle member of the Agua Blanca Sequence. The “marine levels of Pehuen Co”, which are exposed at very low tides and contains in situ specimens of Ophiomorpha nodosa, are dated 7.0 ± 0.4 ka (OSL method). They reflect a Middle Holocene sea level rise in the area.

Trap Parameters for the Fast OSL Signal Component Obtained through Analytical Separation for Various Quartz Samples

Trap stability is essential in luminescence dating and thermochronometry. Trap depth and frequency factors determining the stability of the fast component of optically stimulated luminescence (OSL) in quartz, which is the most important in dating, have yet to be uniquely determined, especially for samples with an OSL signal not dominated by this component. One can determine them in OSL thermal depletion curve (OTDC) experiments. The separation of the fast OSL signal undisturbed by other OSL components is vital for obtaining accurate parameters for the traps of interest. This work presents a method of simultaneous thermal and optical stimulation using red light (620 nm) to separate the fast OSL component (the thermally modulated OSL method-TM-OSL). The OTDC experiment with the TM-OSL stimulation was used for the trap parameter determination on a variety of quartz samples, leading us to report for the first time, the trap parameters for the fast OSL component analytically separated in quartz from rock samples. The results obtained for these samples with the fast component of low intensity are consistent with those with an intensive fast OSL component. Results of OTDC measurements for all investigated quartz samples were tested for a wide range of irradiation doses.

Recent paleoseismic investigations at the hidden Thakhek fault in Thailand

• The branches of the Thakhek Fault zone were first studied in Northeast Thailand. • A single paleoearthquake in the trench (M 7.1 moment magnitude) was examined. • This fault is active based on the inferred age of the displacement events. We conducted a preliminary paleoseismological study at the branches of the Thakhek fault zone in Northeast Thailand. Locating the fault in Thailand is challenging as there are no evident morphotectonic landforms indicative of an active fault. We utilized remote sensing to delineate fault traces, supplemented by geological and geophysical ground-based surveys. We identified a suitable site for trenching through a 2D electrical resistivity tomography (ERT) survey. Trenches were excavated to determine the succession of sedimentary units. The trench-log stratigraphy was compiled and sedimentary samples were dated by optically-stimulated luminescence (OSL) for determining the age sedimentary layers, thereby inferring the putative seismic events. Analysis of the digital elevation model revealed three minor faults extending from Laos into Northeast Thailand with lengths of 138, 159, and 35 km. The ERT survey indicated a clear resistivity contrast, which was interpreted as mudstone with low resistivity juxtaposing sediment layers with higher resistivity. Subsequently, two trenches were excavated. Displacement resulting from reverse faulting appeared to have moved older mudstone over the Quaternary sediment layers with vertical offsets of >3.5 m in the first trench; thrust faulting resulted in a transition fold to fault-bend fold with mudstone ramping over the sediment layers in the second trench. The sediment units cut by the fault plane were dated by the OSL method between 18,120 ± 1920 and 36,960 ± 2780 years in the Pleistocene. Results indicated a single paleoearthquake in the trench with greater than M 7.1 moment magnitude and 0.009 mm/a average slip rate. This fault is potentially active based on the inferred age of the displacement events.

Comprehensive evaluation of electron radiation dose using beryllium oxide dosimeters at breast radiotherapy

AbstractIntroduction:In this study, the differences between calculated and measured dose values were then analysed to assess the performance, in terms of accuracy, of the tested treatment planning system (TPS) algorithms applied to calculate electron beam dose targeted and non-targeted the breast region.Materials and methods:The beryllium oxide (BeO) dosimeters placed on the female RANDO phantom were irradiated 12 MeV electron energy with medical linear accelerator and repeatedly read in the Risø thermoluminescence (TL)/optically stimulated luminescence (OSL) system via OSL method at least three times.Results:For electron treatment, one made quantitative comparisons of the dose distributions calculated by TPSs with those from the measurements by OSL at various points in the RANDO phantom.The mean dose measured from the dosimeters placed on the female RANDO phantom target left breast region was 160 cGy and non-target right breast region was 1·2 cGy. Analysis of Generalised Gaussian Pencil Beam (GGPB) and Electron Monte Carlo (eMC) algorithms for determined region mean point dose values, respectively, 174 and 164 cGy. Two algorithms for non-targeted region calculated same point dose values of 0·2 cGy.Conclusions:The results of this study showed that BeO dosimeters can be used with OSL method in radiotherapy applications and it is a very important tool for the determination of targeted/non-targeted absorbed dose.

Development of cryostat integrated TL/OSL reader for its application in radiation dosimetry

Abstract A cryostat based integrated TL/OSL reader has been designed and developed to study the temperature dependence of photoionization cross-section at various low temperatures. The system has the facility to record thermoluminescence (TL) as well as optically stimulated luminescence (OSL) at various low temperatures from −150 to 250 ∘ C. It facilitates the measurement of OSL at various temperatures thus; temperature dependence of OSL at various low temperatures can be studied. A PID (Proportional–Integral–Derivative) based temperature controller has been designed and incorporated for generating and controlling user defined heating profiles for the TL measurements in the reader system. The reader system can measure the temperature of the planchet within ± 1 ∘ C precision. The optical stimulation unit consists of two high power LEDs fitted in two channels and optically focused on the sample. In the OSL operation, besides the conventional CW-OSL, LM-OSL modes a non-linear OSL (NL-OSL) method has been incorporated in the reader system. The sensitivity of the system is found to be comparable to that of commercial Riso reader system in OSL mode. The OSL grade α -Al2O3:C phosphor was used to test the reader system and investigate the temperature dependence of OSL in this phosphor at low temperature regime. We report the results of OSL experiments on α -Al2O3:C, and of generalized numerical simulations of potential OSL behaviour with temperature. The photoionization cross-section of shallow as well as dosimetric traps has been evaluated numerically as well as experimentally. The design concept of the reader system and the results of low temperature OSL are discussed.

Post-sterilization radiation dosimetry of commercial pharmaceuticals using optically stimulated luminescence

Sterilization with gamma irradiation has been established as an acceptable method highly advantageous compared to other methods for the sterilization of several products, including pharmaceutical preparations. However, the effects of irradiated drugs on the consumer when they are introduced in the human body are still unknown. Thus, consumers should be aware if a drug has been irradiated and freely choose whether to consume it or not. Consequently, development of drug irradiation detection methods, useful for regulatory compliance purposes, is an active area of investigation.To this respect, new OSL measurements on five commercial solid drugs (Daktarin®, Aspirin®, Panadol®, Brufen® and Procef®) for radiation doses up to several kGy were conducted in order to investigate if the OSL method can identify irradiated drugs. Dose response study, computerized curve deconvolution analysis (CCDA), fading test and sterilization dose recovery test with the SARHS protocol were conducted to investigate the optically stimulated luminescence (OSL) characteristics of the drugs and the properties of the involved traps.Results indicate that all drugs have a linear dose range up to 1–2 kGy, while the entire dose range can perfectly be fitted with an exponential decay curve. Although the fading rate varies, an appreciable signal remains unaffected even 6 months post irradiation in all drugs. The CCDA revealed that the kinetics are of second order and that all drugs have a very fast component with a lifetime of approximately 0.3–5.6 s. The single aliquot regenerative protocol for the calculation of the equivalent dose in heat-sensitive materials exhibiting sensitization (SARHS), developed in a previous work, was also tested on the solid drugs. The SARHS, which can correct for the sensitization effect without involving any heating, but introducing an optical bleaching procedure between the repeated irradiation/stimulation cycles during the construction of the calibration curve, proved capable of calculating the sterilization dose of irradiated drugs.The new findings are very promising towards the post-sterilization dosimetry of solid drugs, rendering the OSL and the SARHS protocol capable of the detection and the determination of the radiation dose applied in irradiated drugs, after the fading factor has been estimated.

Optically Stimulated Luminescence (OSL) dosimetric properties of Li2B4O7:Ag,Gd and its relationship with thermoluminescence (TL) glow-curves

The aim of this work was to develop a new lithium tetraborate luminophore with impurities that are strong co-activators for Optically Stimulated Luminescence (OSL) and to investigate its dosimetric properties using OSL method. Li2B4O7:Ag,Gd phosphor consisting of polycrystalline powder was synthesized using Solution Combustion Synthesis method. The structural characterization of the synthesized phosphor was performed using X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) methods. OSL dosimetry properties as a function of step-annealing procedure, radiation dose response, reproducibility of response and loss of stored signal in dark were investigated. Thermoluminescence (TL) glow curve of Li2B4O7:Ag,Gd phosphor consists of two separated glow peaks located at ∼80 and ∼210 °C with a heating rate of 2 °C/s. The traps responsible for these two TL peaks in Li2B4O7:Ag,Gd phosphor were found to be optically sensitive. Li2B4O7:Ag,Gd exhibits high OSL sensitivity and a good OSL signal reproducibility to ionizing radiation. The beta dose-response was performed in the range from 0.1 Gy to 500 Gy. The time-integrated total OSL signal intensity increases linearly with increasing dose from ∼6 Gy to 500 Gy. The minimum detectable dose was found to be ∼17.1 ± 0.9 μGy. The stored energy increased ∼6 % within 4 weeks following a strong fading value of 27 % of the initial OSL intensity after 24 h. Indeed, the X-ray Luminescence (XL) emission spectra are the characteristic of the expected f-f transitions. Luminescence spectrum of Gd doped Li2B4O7 exhibits major red emissions (590 nm, 607 nm, 621 nm) and a weak blue emission (450 nm) along with the emission bands from undoped Li2B4O7. These results strongly suggest that the luminescence properties of Li2B4O7:Ag,Gd deserves more attention as possible dosimeter material. Explanations of many TL/OSL phenomena observed in the study of Li2B4O7:Ag,Gd phosphor and improvements based on the better knowledge in the mechanism of TL/OSL in Li2B4O7:Ag,Gd, a boron-based compound were achieved by this study.

LUMINESCENCE DATING OF AN ANCIENT WALLED SETTLEMENT IN ORKHON VALLEY, MONGOLIA

We investigated the potential of the optically stimulated luminescence (OSL) method to date young (<1000 years) samples collected in the Orkhon Valley Cultural Landscape, Mongolia. Quartz showed an infrared signal; therefore the post-IR OSL method was applied to small aliquots which are considered proxies for single grain measurements. Statistical analysis of the dose distribution produced CAM De of 5.14±0.10 Gy and over dispersion of 47.5%, and MAM De of 3.7±0.6 Gy. Since no partial bleaching was suspected, the analysis of signal composition was done and the fast quartz post-IR OSL lead to De of 4.9±0.2 Gy. Based on the quartz fast component and CAM De we propose the new chronology of ancient construction at 785±80 AD, rather than 906-1125 AD as suggested by archaeological evidence. However, the MAM age is in good agreement with independent age control for construction of the ramparts suggesting the date of reconstruction, collapse or reuse for the square walled enclosure MOR3 during 1090±80AD.

Chronology of a lacustrine core from Lake Linggo Co using a combination of OSL, 14C and 210Pb dating: implications for the dating of lacustrine sediments from the Tibetan Plateau

Vast palaeolakes once occupied the Qinghai‐Tibetan Plateau (TP). Analyses of the sedimentary records of these lakes could potentially provide an extensive dating archive. Many previously constructed age‐depth models simulating lacustrine cores have been principally based on radiocarbon (14C) dating. However, such dating could have been hampered by the so‐called ‘lake reservoir effect’ (LRE) and the reworking of lakebed sediments, resulting in inaccurate 14C age‐depth models and limiting interpretations of existing lacustrine palaeoclimatic records. Lake Linggo Co is located on the central TP, in one of the coldest and most arid regions of Tibet. We dated a 9.87‐m‐long lacustrine core extracted from the lakebed at a water depth of ~60 m using a combination of 210Pb, 14C and optically stimulated luminescence (OSL) techniques. Some 14C ages showed significant age reversals; all the 14C ages were much older than the 210Pb and OSL ages for the same depths. This could possibly be attributed to the presence of old, inherited carbon, causing the inherited 14C age to appear unstable during the deposition period. The 210Pb and OSL ages were roughly concordant, and were also consistent with the stratigraphical succession. We therefore suggest that 14C dating may, on its own, be inadequate for accurate dating of lacustrine sediment sites on the TP, and that the OSL method should also be applied in order to evaluate the reliability of any 14C ages. With this approach, we constructed an age‐depth model, revealing sedimentation rates of 1.7, 0.8, 6.8 and 0.6 mm a−1 between 0–1.9, 1.9–4.2, 4.2–4.4 and 4.4–9.4 ka, respectively.

The chronology of a sediment core from incised valley of the Yangtze River delta: Comparative OSL and AMS 14C dating

Optically stimulated luminescence (OSL) dating has gained increased use in dating deltatic deposits, however, its application can be hindered by the problem of incomplete bleaching. To address this limitation, we test the single-grain OSL method for the first time in the Yangtze River delta. A total of eight OSL and 14 AMS 14C samples were obtained from a 50.8m long sediment core from the incised valley of the delta. Quartz extracted from eight OSL samples from the core was first measured with small multi-grain aliquots using medium- (45–63μm) and coarse-grained (90–125μm or 150–180μm) fractions to test the internal consistency of their respective ages. The results showed that four of five medium-grained quartz samples appeared to be well bleached. In contrast, the coarse-grained quartz samples revealed poor bleaching, except for two samples from the delta front facies. Five coarse-grained quartz OSL samples were further analyzed using a single-grain OSL technique. Only 0.5–0.7% of the grains passed the rejection criteria. Single-grain OSL dating is appropriate for age determination of coarse-grained sediments which have been affected by incomplete bleaching. However, it consumes a lot of instrument time. Central and minimum age models (CAM and MAM) were used to calculate the burial age of the samples; MAM ages fit best in the stratigraphic sequence. Small aliquots are recommended as effective in identifying incomplete bleaching for medium- or coarse-grained quartz. A comparison of AMS 14C dates and OSL ages shows that 14C values are 1–3ka older than OSL ages. According to the OSL ages, core SD experienced rapid accumulation 10–8ka and in the last 2ka. The former is linked to rapid sea-level rise in early Holocene, while the latter is primarily due to the migration of depo-center towards the core site, rather than entirely increased sediment delivery caused by human activities.

APPLICATION OF OSL METHOD IN DATING PAST EARTHQUAKES

The aim of this study was to establish a chronological frame of paleoseismic events of Gyrtoni Fault, (Thessaly, Central Greece), with the use of OSL dating method. The Gyrtoni Fault, defines the north-eastern boundary of the Middle-Late Quaternary Tyrnavos Basin, and was previously investigated with geological methods. Twenty five fluvial-colluvial sediment and pottery samples were collected from two paleoseismological trenches, excavated along the Gyrtoni Fault, from both the upthrown and the downthrown fault blocks. Optically Stimulated Luminescence (OSL) dating was applied to coarse grain quartz using the single-aliquot regenerative-dose (SAR) protocol. Investigations of luminescence characteristics using various tests confirmed the suitability of the material for OSL dating using the SAR protocol. Radioactivity measurements were performed in order to estimate the annual dose rateof the surrounding soils to which the quartz grains were submitted during the burial period of the collected samples. The estimated OSL ages agreed well with the available stratigraphical data, and archaeological evidence. The occurrence of three surface faulting events in a time span between 1.42 ± 0.06 ka and 5.59 ± 0.13 ka was revealed while an earlier faulting event (fourth) was also recognized to be older than 5.59 ± 0.13 ka.

Luminescence dating of prehistoric hearths in Northeast Qinghai Lake and its paleoclimatic implication

Archeological research has been trying to provide evidence relevant to understanding both the timing of and processes responsible for human colonization of the Qinghai-Tibetan Plateau (QTP). Hearth is one of the most extensive, important, and typical prehistoric humanity activity evidence on the QTP. However, there are a number of hearths lacking charcoal material because of the wind and water erosion. Fortunately, most of these hearths can be dated by luminescence dating on the remnant sediments around the hearth. In this study, 18 optically stimulated luminescence (OSL) samples from 14 hearths in Yandongtai site (YDT) and Bronze Wire site (BW) in the northeast of Qinghai Lake area were systematically dated. The OSL ages range from 6.8 ± 0.7 to 14.4 ± 1.2 ka. There is a good agreement between OSL dating results and charcoal ages during the last deglaciation period, which indicates that OSL method has great potential in dating hearth on QTP. Combined with the previous dating results from other hearths, the age of hearths concentrates in 11–13 ka BP, i.e., the Younger Dryas (YD) chronozone. The increased number of hearths indicates reinforced colonization in the Qinghai Lake area during YD cold event, implying that the cold climate during YD event was not severe enough to hinder the inhabitation of prehistoric humanity at an elevation of 3.2 km.

Influence of thermal treatment on OSL regeneration in potassium chloride

Optically stimulated luminescence (OSL) of pure analytical potassium chloride (KCl) prepared in two different forms (crystals and pellets) was studied. The occurrence of regeneration effect (self-renewal of the OSL signal) in the material was examined. The experiments using the variable delay OSL (VD-OSL) method were carried out. Performed measurements allowed to determine time scale of the phenomenon, as well as quantitative changes of regeneration depending on thermal treatment before and after irradiation. Significant increase of the OSL regeneration was noticeable for pellets after the application of the annealing before irradiation, while for crystals a substantial decrease of regeneration was observed. Preheating applied after irradiation caused that self-renewal of OSL signal was drastically reduced or completely suppressed depending on the form of KCl samples.

Major elements in the Holocene loess-paleosol sequence in the upper reaches of the Weihe River valley, China

Palaeohydrological investigations were carried out in the Guchuan Basin in the upper reaches of the Weihe River valley, China. A set of palaeoflood slackwater deposits (SWDs) was found interbedded in the Holocene loess-paleosol sequence at the Guchuanzhen site (GCZ). These palaeoflood SWDs were studied by field observations and laboratory analyses including concentrations of chemical elements and optically stimulated luminescence (OSL) dating. The results showed that the palaeoflood SWDs were the result of the secondary separations of the surface soil and weathered soil layers during the process of water transport and deposition, and without obvious weathering during soil development. These extraordinary flood events were dated back to 3,200−3,000 a B.P. with the OSL method and checked by archaeological dating of the human remains retrieved from the profile. These extraordinary flood events were therefore considered as regional expression of known climatic events and demonstrated the climatic instability in the Holocene. This result is important for understanding the effects of global climate change on the dynamics of river systems.

First direct age determination for the Baltic Ice Lake/Yoldia Sea transition in Finland

The drainage of the Baltic Ice Lake (BIL) to the Yoldia Sea level occurred at around 11 600 years ago and can be considered as one of the most important events in the Late-Glacial Baltic Basin history. Distinctive sandy deposits were formed as a result of the water-level fall. These deposits form a marker horizon at the Pleistocene–Holocene boundary, which has been used as the 0-varve in Finnish clay varve chronology. These sandy deposits have not been dated, and in general, there is lack of direct age determinations from the Pleistocene–Holocene transition. Sediments from three localities: backshore, beachface and upper shoreface environments, interpreted to be connected with BIL drainage, were sampled and dated with an optically stimulated luminescence (OSL) method. Only the beachface deposit appeared to be the suitable material, giving the expected dates of 11 400 ± 1100 and 11 200 ± 1300 years BP for the water-level fall. The other samples were interpreted as only partially bleached, or they represented a mixture of different age generations. This is the first direct dating of a Yoldia shore deposit in Finland and provides a reference for shore displacement studies in Finland. The results also verify the potential of the OSL method in dating ancient shorelines or land uplift history.

Holocene paleofloods related to climatic events in the upper reaches of the Hanjiang River valley, middle Yangtze River basin, China

Holocene slackwater deposits along the river channels were used to study the magnitude and frequency of the paleofloods that occurred prior to gaged and historical data sets all over the world. Paleoflood hydrological investigations were carried out in the upper reaches of the Hanjiang River, China. Four bedsets of paleoflood slackwater deposits were found interbedded in the Holocene loess–soil sequence within the cliff riverbanks. They were studied by field observations and laboratory analysis including magnetic susceptibility, particle size distribution and optically stimulated luminescence (OSL) dating. These provide a complete catalog of Holocene flood events at a watershed scale that is very important in understanding the regional hydrological response to monsoonal climatic change. Four episodes of Holocene overbank flooding have been recorded over the basin. These hydroclimatic events were dated to 8500–8400, 4200–4000, 3200–2800, and 1800–1700YBP by using the OSL method in combination with pedostratigraphic correlations with the previously studied Holocene pedostratigraphy in the Hanjiang River basin. The peak discharges of these flood episodes vary in a range from 26,610 to 47,900m3s−1 as estimated by using the slope–area method of streamflow measurement. These flood events are therefore considered a regional expression of known climatic events and demonstrate Holocene climatic instability. The study provides a solid reference that magnitudes and recurrence frequencies of floods are highly sensitive to climate change in the monsoonal zone in other parts of the world.

Investigation of regeneration effect of blue luminescence in NaCl using variable delay optically stimulated luminescence (VD-OSL)

Optically stimulated luminescence (OSL) of pure analytical sodium chloride (NaCl) was studied. Performing series of CW-OSL (continuous wave OSL) readouts it was found that subsequent CW-OSL decay, after some delay, starts from significantly higher intensity level than the final intensity of the previous readout. To study this ‘regeneration effect’ a new type of measurements was implemented – the variable delay OSL (VD-OSL) method. The idea of VD-OSL is explained – it allows to study OSL kinetics at very long time scale. VD-OSL data confirm coexistence of two effects in NaCl – regeneration and fading of the OSL signal. After partial CW-OSL readout, regeneration predominates in the short time scale of the order of 103 s. Then, fading becomes dominant. The same measurements were applied to commonly used Al2O3:C material as well. Nevertheless, the results do not show such behavior at the studied time scale. Theoretical arguments are presented that the regeneration mechanism cannot be explained on the basis of the simple trap model.

Optically stimulated luminescence (OSL) as a chronometer for surface exposure dating

We pioneer a technique of surface‐exposure dating based upon the characteristic form of an optically stimulated luminescence (OSL) bleaching profile beneath a rock surface; this evolves as a function of depth and time. As a field illustration of this new method, the maximum age of a premier example of Barrier Canyon Style (BCS) rock art in Canyonlands National Park, Utah, USA, is constrained. The natural OSL signal from quartz grains is measured from the surface to a depth of >10 mm in three different rock samples of the Jurassic Navajo Sandstone. Two samples are from talus with unknown daylight exposure histories; one of these samples was exposed at the time of sampling and one was buried and no longer light exposed. A third sample is known to have been first exposed 80 years ago and was still exposed at the time of sampling. First, the OSL‐depth profile of the known‐age sample is modeled to estimate material‐dependent and environmental parameters. These parameters are then used to fit the model to the corresponding data for the samples of unknown exposure history. From these fits we calculate that the buried sample was light exposed for ∼700 years before burial and that the unburied sample has been exposed for ∼120 years. The shielded surface of the buried talus sample is decorated with rock art; this rock fell from the adjacent Great Gallery panel. Related research using conventional OSL dating suggests that this rockfall event occurred ∼900 years ago, and so we deduce that the rock art must have been created between ∼1600 and 900 years ago. Our results are the first credible estimates of exposure ages based on luminescence bleaching profiles. The strength of this novel OSL method is its ability to establish both ongoing and prior exposure times, at decadal to millennial timescales or perhaps longer (depending on the environmental dose rate) even for material subsequently buried. This has considerable potential in many archeological, geological and geo‐hazard applications.

Performance of a near-real-time KBr:Eu dosimetry system under computed tomography x-rays

Abstract The dynamic radiation fields used in Computed Tomography (CT) scans are difficult to characterize quickly using dosimetry techniques that utilize large-volume detectors (e.g. ionization chambers) or passive detectors (e.g., thermoluminescent dosimeters). In this study we demonstrate the feasibility of using the optically stimulated luminescence (OSL) of KBr:Eu for quantitative CT dose measurements. The particular OSL method used is capable of acquiring full OSL signals at a rate of 10 Hz, which allows for near-real-time active dosimetry. The portable reader system connects to the KBr:Eu dosimeter via a fiber-optic cable, through which both stimulation light and OSL propagate. The small volume (∼2 mm 3 ) of the KBr:Eu dosimeter also allows the system to resolve detailed structures in complex radiation fields. Testing of the KBr:Eu dosimetry system under axial and helical CT scanning showed that the fast data acquisition and small dosimeter volume allowed for high-resolution dose profiling using a cylindrical CT body phantom. The dose response of the dosimetry system compared favorably to exposure results reported by a standard 100 mm pencil ionization chamber. A dependence of the OSL output from the KBr:Eu crystal on x-ray energy was also observed. These and similar observations are discussed in detail.

Determination of transmission factors for beta radiation using Al 2O 3:C commercial OSL dosimeters

In recent years, the optically stimulated luminescence (OSL) technique has been used in personal dosimetry, and aluminum oxide (Al 2O 3:C) has become a very useful material for this technique. The objective of this work was the determination of the transmission factors for beta radiation using Al 2O 3:C commercial dosimeters and the OSL method. The obtained results were similar to the transmission factors reported in the beta source calibration certificates.