Multiple-aliquot Protocols Research Articles

The effect of water on the thermoluminescence properties in various forms of calcium sulfate samples

The present study investigates whether thermoluminescence (TL) features are prevalent over calcium sulfate samples, regarding their lever of hydration. Three groups of calcium sulfates -dihydrate (gypsum), hemihydrate (bassanite) and anhydrous (anhydrite)- are investigated, of both commercial and mineral origin. The study includes TL features such as TL glow curve shapes, the stability of TL peaks after successive cycles of measurements, and the estimation of the kinetic parameters of stable TL peaks. Moreover, the slurry of calcium sulfate with water is being studied, to investigate its prevalence as an effective zeroing mechanism. The results indicate the presence of stable TL peaks around 280 °C for all of the groups of calcium sulfates, while the TL sensitivity of the samples depends on their water content and stabilizes after three heating cycles up to 500 °C. Anhydrite shows stability even from the initial measurement, while the hemihydrates and dihydrates could be used for dating applications using TL by means of a multiple aliquot protocol.

Is there a common alpha-efficiency in polymineral samples measured by various infrared stimulated luminescence protocols?

Dating of polymineral silt-sized samples by use of post-infrared infrared stimulated luminescence (pIRIR) protocols at elevated temperature has recently gained attraction due to assumed lower rates of anomalous fading. The α-efficiency (or <i>a</i>-value) associated with the pIRIR signals as an integral part of age calculation has, however, not yet been sufficiently constrained. Here we present a set of 65 <i>a</i>-values determined for 47 samples collected across Europe with two different IRSL protocols in two laboratories. By testing the basic preconditions for application of the single-aliquot regeneration (SAR) procedure to constrain <i>a</i>-values and by comparing SAR results to <i>a</i>-values obtained by multiple-aliquot protocols, we demonstrate that SAR-derived <i>a</i>-values are reliable for the majority of samples. While aliquot size and signal resetting mode prior to α-regeneration do not appear to affect the resulting <i>a</i>-value, we detected significant differences in mean <i>a</i>-values measured in the two laboratories. For the pIRIR<sub>290</sub> signal, <i>a</i>-values average to 0.085 ± 0.010 (Bayreuth) and 0.101 ± 0.014 (Cologne), while a modified SAR protocol yields 0.081 ± 0.008 (Bayreuth). Whereas provenance-specific differences in <i>a</i>-values might be masked by overall scatter, systematic offsets between laboratories are attributed to technical issues such as heater and source calibration. Based on the present data set, use of the same routine dating equipment is strongly advised for both dose and <i>a</i>-value measurements.

A SAR protocol for heat-sensitive materials exhibiting sensitization (SARHS) for the estimation of the equivalent dose

Accurate estimation of the radiation released at incidents, such as nuclear accidents or radiological terrorist events is of major importance for the prediction of health effects following such an incident. The luminescence properties of several materials are studied in order to assess their potential use as dosimeters in such cases.However, the protocols followed for such purposes are mainly those initially developed for dating. Multiple-aliquot protocols are mainly based on the Thermoluminescence response of the dosimeter used and require the availability of abundant material, while homogeneity of the luminescent substance in the entire sample is also a prerequisite in order to prepare similar aliquots. To account for the above drawbacks, several single-aliquot protocols have been suggested based on Optically Stimulated Luminescence (OSL), which however involve steps of heating the sample up to 300 °C, and as a result they can only be used for heat-resistant materials.In the present work, a novel single aliquot regenerative-dose protocol suitable for heat-sensitive materials exhibiting sensitization (called SARHS) for the estimation of the equivalent dose with OSL is proposed. The protocol eliminates any sensitization effects without encompassing any heating of the sample. Validation of the SARHS protocol was accomplished with three different heat-sensitive materials which exhibit sensitivity changes with the repeated use of the same sample (sensitization), i.e., dragonfly wings, a commercial solid drug (Daktarin) and chicken bones, in which the natural equivalent dose could be successfully recovered with negligible error even when fading, after exposure to irradiation, of the natural OSL signal was taken into account.

Dating results on sedimentary quartz, bones and teeth from the Middle Pleistocene archaeological site of Coudoulous I (Lot, SW France): A comparative study between TT-OSL and ESR/U-series methods

This study presents palaeodosimetric results from the Middle Pleistocene archaeological site of Coudoulous I (Lot, SW France). Nine sedimentary quartz samples (41–60 μm) have been analyzed using a multiple aliquot protocol based on the measurement of the TT-OSL signal. In addition, 7 teeth and 7 bones have been dated by combining the ESR method with U-series analyses. Both methods gave consistent age results allowing correlation of the Early Middle Paleolithic Human occupation of the site to MIS 6 and part of the Lower Paleolithic tools to MIS 7. Beyond the establishment of a radiometric chronology for the Coudoulous I sequence, this study focuses on the information extracted from the intercomparison of the methods. Our data suggest that 1) the TT-OSL signal is stable over at least the last 230 ka (considering the age range of the studied samples), 2) there are not significant problems of incomplete bleaching leading support to the applicability of the TT-OSL technique for sedimentary deposits associated with karstic contexts. This approach highlights the interest of combining luminescence and ESR/U-series methods to discuss the reliability of the dating results.

Thermoluminescence properties of irradiated commercial color pencils for accidental retrospective dosimetry

Color pencils are widely used mostly in kindergartens, in schools and could be found in all houses with families having young children. Their wide spread use in modern times as well as their chemical composition, consisting mostly of Si and Al, constitute two strong motivations towards exploiting their use as accidental retrospective thermoluminescent dosimeters. The present manuscript reports on the study of colored pencils manufactured by a commercial brand in China which is very common throughout Turkey. The preliminary results discussed in the present work illustrated encouraging characteristics, such as the presence of a trapping level giving rise to natural TL in a temperature range that is sufficiently high. Specific thermoluminescence features of this peak, such as glow peak shape and analysis, anomalous fading, thermal quenching, reproducibility, linearity and recovery ability to low attributed doses were studied. The results suggest that the color pencils could be effectively used in the framework of retrospective thermoluminescent dosimetry with extreme caution, based on multiple aliquot protocols.

Comments on: Palaeoclimatic considerations of talus flatirons and aeolian deposits in Northern Fuerteventura volcanic island (Canary Islands, Spain). Mateo Gutiérrez-Elorza, Pedro Lucha, F.-Javier Gracia, Gloria Desir, CintaMarín, Nicole Petit-Maire

1) As we are working in the same and similar settings on the eastern Canary Islands and also endeavouring to establish reliable ages based on luminescence dating, we followed the numerical ages published in this paper with great interest. Since besides a wellestablished stratigraphy it is always preferable to have a robust time control, we should be happy to accept these new ages from the Rosa Negra quarry at this time (Fig. 4). However, it is essential to have some detailed explanations (methods) on the dating procedure applied by the authors. In particular, we would like to know on what material luminescence dating was conducted: Was it IRSL on feldspar, or was it OSL on quartz? Were fine or coarse grains used? Were single or multiple aliquot protocols applied? How were dose

Testing heated flint palaeodose protocols using dose recovery procedures

Thermoluminescence (TL) dating of materials from archaeological contexts has been shown to be an accurate method when comparisons are made with other chronometric dating methods; however, little has been published on the verification of the measurement protocols used to determine the equivalent dose (palaeodose). Instead of testing TL dating protocols for heated flint using archaeological material with unknown thermal and radiation history, dose recovery tests for three samples of different geological origin are presented. These samples exhibit TL emission in the UV, blue and orange–red wavelengths. In addition to the two multiple aliquot protocols (standard additive-regeneration and normalization) generally used to determine the palaeodose, the single-aliquot-regenerative-dose (SAR) TL and OSL procedure, a ‘short’ SAR–TL and isothermal luminescence (IT) decay procedures are applied using detection windows limited to these emissions. Accurate dose recovery is obtained for the standard and normalization protocols in the commonly employed detection window (UV-blue), the ‘short’ SAR in the orange–red window and some IT measurements. While the standard techniques give the most accurate and precise results, detection of the TL and IT orange–red emission in connection with a ‘short’ SAR protocol also gave accurate and precise results. Such procedures are especially suitable for samples too small for standard multiple aliquot techniques, which require large samples.

Optical dating using feldspar from Quaternary alluvial and colluvial sediments from SE Brazilian Plateau, Brazil

Opticallly stimulated luminescence (OSL) dating has been applied to a wide variety of materials such as loess, sand dunes, colluvium, alluvium, volcanic products, etc., helping geologic geomorphologic studies. OSL dating results using feldspar crystals extracted from alluvial and colluvial deposits of SE Brazilian Plateau will be presented in this work. The methodology used is based on the regeneration method, with multiple aliquot protocol. A total of 23 sample ages were obtained spanning 6.5–97.2kyr. Results of radioactive contents and comparison with radiocarbon ages will be discussed.

Optical dating results of beachrock, eolic dunes and sediments applied to sea-level changes study

Quartz and feldspar crystals were selected from the samples as eolic dunes, beach-rock and marine terraces, all collected in the coast area of Paraiba State, located in northeastern Brazil, in order to obtain ages of deposition of the sediments. It is a systematic study in the area. The results of the ages will be used in local sea-level changes study and a correlation between highstands of marine oxygen-isotopes stages will be made. Optically stimulated luminescence and thermoluminescence have been measured and the regeneration method with multiple aliquot protocol was applied to obtain the paleodose values. Preliminaries ages spanning 3.2–229kyr were evaluated.

Comparison of quartz OSL protocols using Lateglacial and Holocene dune sands from Brandenburg, Germany

We present the results obtained using various different protocols in the quartz optically stimulated luminescence dating of a Late Glacial and Holocene aeolian dune sequence near Eberswalde, north of Berlin, Germany. The Allerød `Finow’ palaeosol and the Laacher See tephra layer serve as chronostratigraphic markers, and further independent age control is provided by eight 14 C ages. The application of the single-aliquot regenerative-dose protocol (using blue light stimulation) and the multiple-aliquot regenerative-dose and additive-dose protocols (using broad-band blue and green light stimulation) are discussed. A comparison of radionuclide analyses using high-resolution gamma-spectrometry and neutron activation analysis is also presented. It is concluded that the two dosimetry methods give indistinguishable results, although the gamma spectrometry data are more precise. In contrast, the single-aliquot regenerative-dose protocol is between 2 and 10 times more precise than the multiple-aliquot protocols, and systematic differences in performance are also observed. The uncertainties in the dosimetry calculations are the largest contributor to the overall age uncertainties. The accuracy of the resulting ages is considered very satisfactory when tested against the independent age controls, over the entire age range from the present to 15 ka.

Effect of heating on the quartz dose-response curve

We have investigated the effects of annealing quartz at temperatures up to 1000°C on both the absolute sensitivity and on the growth curve shape, using quartz extracts from three sedimentary samples from widely separated locations. Growth curves up to 670 Gy were measured using the single-aliquot regenerative-dose protocol, which allows all heat treatments and OSL measurements to be performed on a single sub-sample, with a corresponding improvement in precision when compared with multiple-aliquot protocols. It is found that the degree of dose-dependent sensitivity change is dependent on the annealing temperature. Despite this, and absolute sensitivity changes of more than three orders of magnitude, the growth-curve shape is relatively independent of annealing temperature, especially at low doses.

Comparison of regenerative-dose single-aliquot and multiple-aliquot (SARA) protocols using heated quartz from archaeological sites

We have tested the suitability of a new regenerative-dose single-aliquot protocol (Murray and Roberts, Radiation Measurements, in press) for dating 16 samples of heated quartz, taken from 11 different archaeological sites. Representative examples of changes in sensitivity with preheat temperature and with regenerative cycle are presented, and it is shown that the sensitivity changes in the optically stimulated luminescence response are linearly correlated with those of the 110°C thermoluminescence (TL) response. We deduce that the new single-aliquot protocol, which corrects for sensitivity change using the 110°C TL response, should be applicable to these fired samples. Estimates of the 16 equivalent doses derived using the new protocol are compared with values obtained using the multiple-aliquot protocol SARA (single-aliquot regeneration and added dose; Mejdahl and Bøtter-Jensen, 1994) and the agreement is satisfactory. A simplification of the new protocol is also tested. For our samples, we do not find any significant dependence of the equivalent dose on preheating (for 10 s) in the temperature range 160–300°C. We conclude that the new single-aliquot regenerative-dose protocol is a fast and reliable method for estimating the equivalent dose in heated quartz. It has considerable potential in many archaeological applications, especially for small samples and/or heterogeneous material.

Equivalent dose measurement using a single aliquot of quartz

The principles behind an additive-dose single-aliquot protocol and the need for such a protocol are outlined. It is shown for two Australian sedimentary quartz samples that the decay of OSL during a repeated measurement cycle, consisting of a 10 s preheat at a given temperature followed by a 0.1 s exposure to green light at 110°C, can be well represented by exponential decay. The decay constant of about 8% per cycle is insensitive to preheat temperatures below about 250°C, but increases to about 35% per cycle at 280°C. This increase is attributed to increasing thermal erosion of the main OSL trap. The decay constant is also shown to be insensitive to dose. An additive-dose protocol is presented which requires only one aliquot for the estimation of the equivalent dose ( D e). This protocol has been applied to quartz from 11 Australian sites. To illustrate the value of the single-aliquot approach, the apparent values of D e for 14 samples, containing doses of between 0.01 and 100 Gy, have been measured in triplicate at preheat temperatures of between 150 and 300°C, using a single aliquot for each D e measurement. It is shown that low temperature preheats (≈200°C for 10 s) are appropriate for the younger samples containing the smaller doses, but a much higher temperature preheat (≥280C for 10 s) is required for the older samples containing the larger doses. Excellent agreement is found between these single-aliquot estimates of D e and those from additive-dose multiple-aliquot protocols, over the entire dose range.