Component resolved IR bleaching study of the blue LM-OSL signal of various quartz samples

The present work provides an initial component resolved analysis concerning the effect of infra-red (IR) exposure at elevated temperatures on the blue LM-OSL signal of quartz (stimulated at 470 nm). The study was performed on a total of seven quartz samples, among which five originated from Turkey, one from Greece and one synthetic quartz sample. For these quartz samples, the presence of 6 or even 7 independent LM-OSL components was previously reported, after the application of a computerized decomposition analysis. IR bleaching of each one of these components is studied and compared to the respective signal reduction due to the same thermal treatment solely. It is clearly demonstrated that IR stimulation at temperatures above 50 degrees C does not deplete only the fast component in most sedimentary quartz samples studied. Net depletion of fast and medium components resulting from IR exposure is sample-dependent and occurs faster as the stimulation temperature increases. Weak IR bleaching of slow components is also reported in some cases, being more effective for stimulation temperatures up to 100 degrees C. No depletion of either the medium or the slow components was detected for stimulation temperatures above 150 degrees C. Finally, IR does not stimulate any of the LM-OSL components in the case of the synthetic quartz sample.The present work was partially funded by the Greek General Secretariat of Research and Technology and the E.C., under the programme “Excellence in Research Institutes GSRT (2nd round)”, sub-programme “Support for Research Activities in C.E.T.I.”.Publisher's Versio

Investigation of the OSL signal from very deep traps in natural quartz

It has been recently reported by several studies that a thermally transferred optically stimulated luminescence (TT-OSL) signal from quartz grains can be used to extend the dating range for quartz samples. The TT-OSL signals are believed to consist of a recuperated OSL (ReOSL) component and a basic-transferred OSL (BT-OSL) component. In the present work the TT-OSL signals from several types of unfired quartz samples were studied. A special protocol was used, which allowed the measure the OSL from very deep traps (VDT) as a function of the OSL stimulation temperature. It was found that all quartz samples exhibit TT-OSL signals, which are depended on sample and on the OSL stimulation temperature. The activation energy of the process was evaluated and the influences of the TT-OSL on the ReOSL dating protocol are discussed.Publisher's Versio

Preliminary results towards the equivalence of transformed continuous-wave Optically Stimulated Luminescence (CW-OSL) and linearly-modulated (LM-OSL) signals in quartz

The present paper presents a comparative experimental study of two commonly measured Optically Stimulated Luminescence (OSL) signals in quartz. The experimental study measures both the continuous wave OSL (CW-OSL) and the linearly modulated (LM-OSL) signals from the same quartz sample for a range of stimulation temperatures between 180 and 280A degrees C, while the former is transformed to pseudo LM-OSL (ps LM-OSL). A computerized deconvolution curve analysis of the LM-OSL and ps LM-OSL signals was carried out, and the contributions of several OSL components to the initial OSL signal (0.1 s) were shown to be independent of the stimulation temperature used during the measurement. It was also found that the composite OSL (0.1 s) signal consists mainly of the first two OSL components present in the OSL curves. The equivalence of the ps LM-OSL (transformed CW-OSL) and of LM-OSL measurements was also examined by an appropriate choice of the experimental stimulation times, and of the stimulation power of the blue LEDs used during the measurement.George S. Polymeris is financially supported by TUBITAK (The Scientific and Technological Research Council of Turkey), in the framework of a Post-doc Fellowship for foreign citizensPublisher's Versio

Preliminary TL and OSL investigations of obsidian samples

Obsidian is a volcaniclastic mineral extremely hard to break, which was used in prehistoric Greece (and elsewhere in the World), in order to provide tools, weapons, knives and arrowheads. The present work aims to characterize this extremely precious tool stone by using both thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques and investigate its potential use for luminescence dating purposes. Basic TL and OSL properties, such as TL and OSL thermal and optical stability, repeatability, TL and LM-OSL glow curve shape and mainly the linearity of the TL and OSL signals as a function of beta dose were investigated. Artificially irradiated samples indicate all promising luminescence features, such as the 110 degrees C TL peak and dose response sub-linearity for intermediate doses, quick and effective bleaching all over the entire TL glow curve, along with quite linear CW-OSL dose response for doses larger than 5 Gy. The lack of predose sensitisation indicates the suitability of the material for single aliquot measurements. Furthermore, several features provide indications that the signal does not relate to quartz, but in fact to other silicates. Unfortunately, both lack of bleaching ability for NIL signal, along with a peculiar shape of NOSL, provide major difficulties in dating applications.Publisher's Versio

TL and OSL response of turquoise for dosimetric application

Turquoise is one of the amongst first gem stones used in jewelry and possessing cultural value since 2000 BC (at least). This work attempts characterize this stone scientifically using both thermally (TL) and optically stimulated luminescence (OSL) techniques. The experimental investigation included 1) the study of the natural TL and OSL signals, 2) the reproducibility of TL sensitivity over repeated irradiation and TL readout cycles, 3) dependence of sensitivity on annealing temperatures and 4) the TL and OSL dose response curves. The potential use of the TL and OSL techniques in determination of provenance, accidental dosimetry and probably to authenticity and dating purposes are then discussed.Publisher's Versio

IRSL dating of a deep water core from Pylos, Greece; comparison to post ir blue OSL and TL dating results

The 'double SAR' protocol procedure permits the determination of two equivalent dose (De) values for each polymineral aliquot; an IRSL De resulting mostly from feldspars along with a post-IR OSL De for a mixed signal for quartz (mostly) and feldspar grains. The objective of the present study is to test for the first time its usefulness for polymineral, coarse silt, closely-spaced deep-sea sediment samples. A new, 'double SAR' IRSL dataset is presented for the sedimentation ages of a deep-sea sediment core of the Hellenic Trench, drilled from a water depth of 4 km, near the deepest site of the Mediterranean Sea, outside Pylos, Greece. Post IR quartz-based optical dating was previously proved to be consistent with AMS radiocarbon ages, obtained from planktonic foraminifera from the same core. IRSL De values are, with one exception, always much greater than the corresponding (post-IR) OSL results. This result suggests that for the present study 'double SAR' protocol procedure was proved to be extremely effective method for separating the luminescence signals from quartz and feldspars. Furthermore, De values obtained after infra-red stimulation and thermoluminescence generally agree within errors. This quantitative equivalence of those two sets of De values implies that as in the case of IRSL, TL signal is also feldspar-dominated. IRSL ages vary between 3.5 and 7.8 ka with associated errors up to 9%. Application of 'double SAR' protocol to coarse silt, closely-spaced deep-sea sediment samples seems advisable, despite the fact that the post-IR blue OSL signal is the most stable signal, and is preferred for dating.Publisher's Versio

On the Need for Deconvolution Analysis of Experimental and Simulated Thermoluminescence Glow Curves

Simulation studies of thermoluminescence (TL) and other stimulated luminescence phenomena are a rapidly growing area of research. The presence of competition effects between luminescence pathways leads to the complex nature of luminescence signals, and therefore, it is necessary to investigate and validate the various methods of signal analysis by using simulations. The present study shows that in simulations of luminescence signals originating from multilevel phenomenological models, it is not possible to extract mathematically the individual information for each peak in the signal. It is further shown that computerized curve deconvolution analysis is the only reliable tool for extracting the various kinetic parameters. Simulation studies aim to explain experimental results, and therefore, it is necessary to validate simulation results by comparing with experiments. In this paper, testing of simulation results is performed using two methods. In the first method, the influence of competition effects is tested by comparing the input model parameters with the output values from the deconvolution analysis. In the second method, the agreement with experimental results is tested using the properties of well-known glow peaks with very high repeatability among TL laboratories, such as the 110 °C glow peak of quartz

Témoignage d’une Delphes préhistorique par la datation par luminescence

Une nouvelle recherche de la Delphes préhistorique (site de Koumoula, mont Parnasse) sur la base de la datation absolue d’un assemblage céramique archéologique et de murs en pierre provenant de fouilles récentes de sauvetage est présentée ici, en utilisant des techniques de luminescence. Pour l’estimation chronologique de l’assemblage céramique, des protocoles de luminescence stimulée optiquement (OSL) et de thermoluminescence (TL) ont été utilisés ; la technique de datation par luminescence de surface a été appliquée sur des échantillons de roches calcitiques extraites des fouilles. Des études de dosimétrie (terrain et laboratoire) ont été pratiquées en utilisant la combinaison d’un scintillateur Geiger calibré portable, d’un compteur alpha (technique des paires), de la microscopie électronique à balayage (SEM/EDS), cette dernière technique devant aussi fournir des informations quant à la chimie et aux conditions de cuisson des céramiques. Les résultats de l’étude ont fourni des dates remontant au Néolithique et au Bronze précoce à moyen (∼ 2000 à 5000 ans B.C.) de Grèce, formant un cadre chronologique absolu pour la zone étudiée ; en outre, ces premières données préhistoriques fournissent des liens archéologiques en faveur d’un usage en parallèle du site ici étudié et de l’habitation voisine dite Antre corycien.A new research of prehistoric Delphi (Koumoula site, Parnassus Mountain) based on the absolute dating of an archaeological ceramic assemblage and stonewalls from recent rescue excavation is presented using luminescence techniques. For the chronological estimation of the ceramic assemblage, optically stimulated luminescence (OSL) and thermoluminescence (TL) protocols were employed, and the surface luminescence dating technique was applied on excavated calcitic rock samples. Dosimetry studies (field and laboratory) were practiced using a combination of a portable calibrated Geiger scintillator, alpha counting (pairs technique) set up and scanning electron microscopy (SEM/EDS), the latter also to probe information about the chemistry and firing conditions of the ceramics. The results of the study provided dates that ascribe the site to the Greek Neolithic and Early/Middle Bronze Age (∼ 2000 to 5000 years B.C.), forming an absolute chronological framework for the studied area; moreover, these first prehistoric data provide archaeological links for the parallel use of the site with the nearby Corycian Cave habitation.</p

TL/OSL properties of crystalline inclusions from heavy, barytes loaded, concrete

In the present work, we report the luminescence data obtained from heavy, barytes loaded, concrete containing many crystalline inclusions, extracted from a shielding block located at CERN. The use of both Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) signals, resulting from a specific trap at about 200 degrees C, is investigated for retrospective dosimetry purposes. By applying thermal cleaning experiments the TL signal of interest was isolated. Basic TL and OSL properties as thermal and optical stability, repeatability and mainly the linearity of the TL and OSL signals as a function of beta dose were investigated. The implications of all these luminescence properties to retrospective dosimetry are also briefly discussed.Publisher's Versio