TL Techniques Research Articles

Application of optically stimulated luminescence technique to evaluate simultaneously accumulated and single doses with the same dosimeter

Optically stimulated luminescence dosimeters (OSLD) can be read several times with a negligible loss (degradation) of signal. In this work, we explore this OSL property to estimate simultaneously the accumulated and single doses using a unique Al2O3 dosimeter, irradiated repeated times along over 4 months. This was done through several irradiations of OSLD (Landauer Luxel Dots) with two energies (28keV X-rays and 1.25MeV Co-60 gamma rays) and several doses distributed over time. Thermoluminescent dosimeters (TLD) were used as a reference to compare the estimated doses obtained with OSLD. For each irradiation, and both energies, a calibration curve was evaluated with OSLD and TLD to estimate the dose values. The OSL readouts were made with a MicroStar (Landauer) OSL reader. To estimate background (BG) over time, a set of OSLD and TLD (Bycron TLD100) was not irradiated and BG was monitored at each readout section. After irradiations, the OSL and TL signals were converted to dose and values were compared. As a set of OSLD suffered no bleaching after the readouts, it was possible to estimate simultaneously the accumulated and single doses with a unique OSLD. Each single dose was estimated through the subtraction of successive accumulated doses determined for each single OSLD. We concluded that the single doses determined by OSL and TL techniques were compatible, and that the accumulated dose, obtained with OSL technique was comparable to the sum of single doses determined with TLD. We can conclude that using OSL technique and Al2O3 dosimeters it is possible to estimate simultaneously accumulated and single doses with the same dosimeter irradiated with low or high energy photons.

Geoarchaeological reconstruction of the Caverna de las Brujas (Mendoza, Argentina) for the planning of an archaeological intervention

Archaeological prospection and excavation in the Caverna de las Brujas (southern part of the province of Mendoza, Argentina) has offered the first known data on human presence in this cave. This is of great interest for understanding the evolution of peopling in the southern Mendoza province during the Holocene. Four archaeological pits were excavated, two in the gallery known as the Sala de la Virgen and another two near the cave entrance. Three volcanic ash levels were dated by TL techniques (7780 ± 600, 4700 ± 500; 765 ± 200 years) and a level with enough organic material was dated by 14C analysis (3695 ± 65 years BP). The available data is sufficient to establish the origin and make a geomorphological reconstruction of the Holocene levels. At the same time, a hypothetical model is proposed that uses geomorphological criteria to predict the stratigraphy of the unexcavated lower levels at the cave entrance. The aim of this model is to help direct future archaeological excavations of the cave's oldest deposits.

Persistent luminescence in Ca8Zn(SiO4)4Cl2:Eu2+

A new persistent, green emission is reported for europium activated Calcium Zinc Chlorosilicate (CZCS). The phosphor was prepared by the solid state reaction and characterized using XRD, PL and TL techniques. The decay was characterized by admixture of two exponential components with decay constants 20.2 and 101s.

Identification of low amount of irradiated spices (red pepper, garlic, ginger powder) with luminescence analysis

For the identification of irradiated food, current analysis methods have limitations regarding presence and stability of radiation-induced markers. In this study, different spice blends with small quantity of different irradiated (0, 1 and 10kGy) spice powders, such as red pepper, garlic or ginger, were investigated using PSL and TL techniques. In PSL-based screening analysis, the spice blends containing 10% of irradiated materials (1 or 10kGy) were determined as intermediate or positive. In TL results, the blends containing 1% of 1 or 10kGy-irradiated spices showed the typical TL glow curves that could be interpreted as positive. The blends with irradiated garlic powder provided more good results where identification was possible at 0.5% mixing of irradiated sample. However, the TL ratios of all spice blends were <0.1 and only TL glow curve shape and intensity may be used to discriminate the samples having irradiated component.

Miniaturized fractal-shaped branch-line coupler for dual-band applications based on composite right/left handed transmission lines

In this paper, novel dual-band (DB) branch-line couplers (BLCs) employing a composite right/left handed transmission line (CRLH TL) and fractal geometry are presented for the first time. The CRLH TL, with specified characteristic impedance and phase shift, consists of lumped elements for the left handed (LH) part and fractal-shaped microstrip lines (MLs) for the right handed (RH) part, which can be designed separately. Two designed BLCs are involved in size reduction, one using a 3/2 fractal curve of first iteration, the other constructed based on a hybrid shape of fractal and meandered lines. A miniaturized principle for CRLH TL realization is derived and an exact design method for fractal implementation is developed. For verification, an example coupler was fabricated and measured. Consistent numerical and experimental results confirmed the design concept, showing that the BLCs obtain DB behavior centered at 0.9 GHz and 1.8 GHz respectively with good in-band performance, except for slightly larger coupled insertion loss for the hybrid-shaped BLC case. In addition, the proposed fractal- and hybrid-shaped BLCs obtained a 49.7% and 64.1% size reduction respectively relative to their conventional counterparts working in the lower band. The most important contributions of this article are the demonstration of compatibility between the fractal and CRLH TL techniques and the provision of an alternative approach and a new concept for designing devices.

RADIATION ACCIDENT DOSIMETRY ON GLASS BY TL AND EPR SPECTROMETRY

Retrospective dosimetry using glass has been investigated. Radiation-induced signals have been surveyed for a large number of watch glasses and display windows of mobile phones with TL and EPR techniques in order to study the variability of dosimetric properties among the different types of samples. Dose response, signal stability, and effects of storage conditions are presented.

Correlated ESR, PL and TL studies on copper activated thermoluminescence dosimetry phosphors

Abstract Cu doped lithium borate and lithum fluoride are two important phosphors in dosimetry of ionizing radiations using thermoluminescene. It is not yet known whether Cu+, Cu2+ or Cu0 are responsible for imparting the desired dosimetric characteristics. It is also not known whether the thermal instabilities of these samples are related to valence conversion of copper. Results of the experiments using TL, PL and ESR techniques which can be useful in answering these queries are presented in this paper.

Thermoluminescence dating of the orkutsay loess section in Tashkent region, Uzbekistan, Central Asia

The chronology of loess in Central Asia was investigated by means of thermoluminescence dating (TL) in the 1970s, when age estimates ranging from 20 ka to over 800 ka were taken as providing an absolute chronology. This has caused major misinterpretation of Central Asian loess stratigraphy and palaeoclimatic reconstruction. We present a new TL study of a loess section at Orkutsay in the Tashkent Region, Uzbekistan. Nine samples spreading over a large stratigraphic interval yield apparent TL ages ranging from 20 ka to 134 ka. We interpret our TL results with reference to recent TL dating studies of loess from other regions. We consider most of our TL age estimates obtained by the regeneration method to be underestimated. A single TL date of 92.8 ka obtained by the total bleach method for loess just below the first pedocomplex (PC 1) of the last interglacial is also significantly younger than expected. We attribute the underestimation to sensitivity change induced by the laboratory optical bleach and instability of the TL signal. We conclude that the current TL techniques as employed in this study cannot provide a reliable absolute chronology for the sequence below PC 1 and cannot provide even a relative chronology for the loess below PC2. For the Orkutsay section the dating limit is around 130 ka. The results of this study suggest that the previous Central Asian loess chronology based on early TL studies is not valid.

A pleistocene origin for shore platforms along the Northern Illawarra Coast, New South Wales

SUMMARY This paper examines the composition, structure and age of clastic deposits situated behind shore platforms at Austinmer and Coledale on the northern Illawarra coast, New South Wales. Our results support earlier chronological evidence of a Pleistocene history for shore platforms along the Illawarra coast. The size and fabric of sediments within these deposits indicate rapid, high‐energy deposition of bedrock eroded from platforms adjacent to the deposits. The elevations of the deposits above the modern shoreline suggest higher sea levels or higher wave energy gradients than presently occurs across these platforms. Dating of sediments within these deposits using 14C, AAR and TL techniques indicates Late Pleistocene and Late Holocene erosion of the shore platforms. Platform development was initiated before the Last Interglacial as correlative sediments lie atop relict platform surfaces landward of the modern platforms.

Study of TL Response in Heavily Irradiated Rock Salt

Abstract Within the framework of the CEC R&amp;D Programme 'Management and Storage of Radioactive Waste', the study of the generation of radiation damage in heavily irradiated rock salt is being carried out. This work describes the experiments carried out for the validation of the TL techniqus, in the assessment of the phenomena related to the energy absorbed by the rock salt, due to the high levels of irradiation. The samples analysed are natural rock salt coming from the Sallent mine (Spain). The chemical composition of the rocks is, in all cases, higher than 90% NaCl, having small amounts of SO4, Mg, K, Br and Sr as major impurities. A first set of irradiations was performed at the laboratory with a source of 137Cs. The doses reached were lower than 20Gy. A second set of irradiations was performed at an industrial facility with a source of 60Co, achieving doses up to 2.5 MGy. Afterwards the irradiated samples were analysed with TL and optical absorption techniques. The results have facilitated a study of the glow curves, their evolution in time and the influence of the chemical composition, the absorbed dose, and the absorbed dose rate. These experiments have increased knowledge of the behaviour of heavily irradiated rock salt.

Study of TL Response in Heavily Irradiated Rock Salt

Within the framework of the CEC R&D Programme 'Management and Storage of Radioactive Waste', the study of the generation of radiation damage in heavily irradiated rock salt is being carried out. This work describes the experiments carried out for the validation of the TL techniqus, in the assessment of the phenomena related to the energy absorbed by the rock salt, due to the high levels of irradiation. The samples analysed are natural rock salt coming from the Sallent mine (Spain). The chemical composition of the rocks is, in all cases, higher than 90% NaCl, having small amounts of SO4, Mg, K, Br and Sr as major impurities. A first set of irradiations was performed at the laboratory with a source of 137Cs. The doses reached were lower than 20Gy. A second set of irradiations was performed at an industrial facility with a source of 60Co, achieving doses up to 2.5 MGy. Afterwards the irradiated samples were analysed with TL and optical absorption techniques. The results have facilitated a study of the glow curves, their evolution in time and the influence of the chemical composition, the absorbed dose, and the absorbed dose rate. These experiments have increased knowledge of the behaviour of heavily irradiated rock salt.

Preparation and Characterization of the K3Na(SO4)2: Eu Phosphor

A new phosphor in the system K2SO4 Na2SO4 doped with Eu is reported. This is shown to be at least thrice as sensitive as the conventional CaSO4: Dy phosphor used in the thermoluminescence dosimetry of ionizing radiations. Characterization of this phosphor using XRD, PL, and TL techniques is described.

TL and TSEE Techniques for Skin Dose Measurements

TL and TSEE Techniques for Skin Dose Measurements

TL and TSEE Techniques for Skin Dose Measurements

TL and TSEE Techniques for Skin Dose Measurements

METEORITES AND THERMOLUMINESCENCE

The TL techniques that have been developed successfully for archaeological and dosimetric applications cannot be unambiguously applied to meteorites because of the possibility that most or all of the meteorite TL is in dynamic equilibrium — its rate of thermal decay balancing its rate of build‐up. In this situation, space irradiation temperature and, thereby, orbital information for the most recent eras (105‐106 years), can be determined. In only a few instances (e.g. meteorites with very low exposure ages) will the possibility exist that equilibrium may not have been reached, but even here it has to be shown that the exposure event had removed previously existing TL before normal TL dating techniques can be employed.There is some evidence to suggest that the TL sensitivity builds up with time. This raises the possibility of dating major shock and/or reheating events, if it can be shown that such events destroyed the TL sensitivity.