Niyazi Meriç

INFRARED STIMULATED LUMINESCENCE AND THERMOLUMINESCENCE DATING OF ARCHAEOLOGICAL SAMPLES FROM TURKEY

Infrared Stimulated Luminescence and Thermoluminescence Dating of Archaeological Samples From Turkey In this study, the potential of Infrared Stimulated Luminescence (IRSL) and thermoluminescence (TL) for dating the archaeological samples (pottery sherds and soil sample adhered to surface of human bone) which were taken from a Necropolis was investigated. Archaeological sherds taken from Nusaybin (Mardin, Turkey), an archaeological site of archaic and Hellenistic period (from 330 BC to 30 AD), were dated. Samples were prepared by the fine grain technique and paleodose values were estimated by using multiple aliquot additive dose (MAAD) and single aliquot regenerative dose (SAR) procedures. The annual doses of uranium and thorium were determined by using the low level alpha counter. The potassium contents, which have no alpha activity, were determined by XRF equipment. The average age of the sherds were found to be 2375±170 years which is in good agreement with the archaeological evidence involving architecture of castle wall, Necropolis and column sherds in the vicinity of the site.

Determination of scatter fractions of some materials by experimental studies and Monte Carlo calculations

Abstract Scatter fractions have been determined experimentally for lucite, polyethylene, polypropylene, aluminium and copper of varying thicknesses using a polyenergetic broad X-ray beam of 67 kVp. Simulation of the experiment has been carried out by the Monte Carlo technique under the same input conditions. Comparison of the measured and predicted data with each other and with the previously reported values has been given. The Monte Carlo calculations have also been carried out for water, bakelite and bone to examine the dependence of scatter fraction on the density of the scatterer.

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.

Calculation of radiation dose to the lens of the eye using Monte Carlo simulation

The radiation dose to the lens of the eye of patients undergoing diagnostic and interventional radiological procedures of the lacrimal drainage system has been calculated using a Monte Carlo technique. The technique has also been suggested for the retrospective estimation of the lens dose: when applied to individual patients, good correlation is obtained. In such study, data is required for image acquisition frame numbers and fluoro on-time, mean exposure values for these parameters, and the ratio of lens-to-air dose (viz, the head factor, HF) derived for a standard adult head.

Determination of trapping parameters in BeO ceramics in both quenched as well as reconstructed thermoluminescence glow curves using various analysis methods

The trapping parameters of BeO thermoluminescence peaks 2 and 3 (with delocalization temperatures of 192 and 308°C respectively, obtained with heating rate of 1K/s) have been calculated using various analysis techniques, including the peak shape methods, isothermal decay, variable heating rates, the fractional glow technique and de-convolution. However, as BeO has been reported to undergo thermal quenching, both intensity as well as trapping parameters are affected, because the glow curve is distorted. Therefore, trapping parameters were calculated for both quenched and unquenched data of the aforementioned thermoluminescence peaks. The unquenched glow curves were determined by reconstructing the corresponding quenched; the following thermal quenching parameters were adopted: W = 0.60eV and C = 1.3 × 106 for peak 2 and W = 0.80eV and C = 1.2 × 107 for peak 3. The obtained activation energies and frequency factors before and after reconstruction were compared both for every method and also to previous studies. This study emphasizes the importance of reconstruction process on trapping parameters for peak 3, as this peak lies within a special temperature range where the efficiency gets values < 0.54. The main dosimetric peak is mildly affected by thermal quenching; thus before and after reconstruction the corresponding values do not yield significant variations. The average values for the activation energy and frequency factor after reconstruction were calculated as 1.14 ± 0.07eV and 9.9 × 1010 ± 0.4 × 1010 s-1 for peak 2; the corresponding values for peak 3 are 1.34 ± 0.08eV, 6.9 × 1011 ± 0.6 × 1011 s-1 respectively. Both peaks are described by first order of kinetics even after reconstruction has occurred. Individual peculiarities of each analysis technique has been both presented and discussed.

Measurement of radiation dose with BeO dosimeters using optically stimulated luminescence technique in radiotherapy applications.

The radiation dose delivered to the target by using different radiotherapy applications has been measured with the help of beryllium oxide (BeO) dosimeters to be placed inside the rando phantom. Three-Dimensional Conformal Radiotherapy (3DCRT), Intensity-Modulated Radiotherapy (IMRT) and Intensity-Modulated Arc Therapy (IMAT) have been used as radiotherapy application. Individual treatment plans have been made for the three radiotherapy applications of rando phantom. The section 4 on the phantom was selected as target and 200 cGy doses were delivered. After the dosimeters placed on section 4 (target) and the sections 2 and 6 (non-target) were irradiated, the result was read through the OSL technique on the Risø TL/OSL system. This procedure was repeated three times for each radiotherapy application. The doses delivered to the target and the non-target sections as a result of the 3DCRT, IMRT and IMAT plans were analyzed. The doses received by the target were measured as 204.71 cGy, 204.76 cGy and 205.65 cGy, respectively. The dose values obtained from treatment planning system (TPS) were compared to the dose values obtained using the OSL technique. It has been concluded that, the radiation dose can be measured with the OSL technique by using BeO dosimeters in medical practices.

Infrared stimulated luminescence (IRSL) properties of natural aluminum corrosion

In this paper, the infrared stimulated luminescence (IRSL) property of naturally corroded aluminum and its possible applications in retrospective dosimetry have been briefly studied. Results are interesting, in particular with regard to the efforts of finding new and widely available materials for accident dosimetry. For aluminum corrosion, the dose response was found to be approximately linear between 2–80 Gy and to reach saturation before 300 Gy. The signal also showed good repro-ducibility without significant fading over storage durations of up to four mounts at room temperature. In addition to the luminescence, the corrosion samples were also analysed by X-ray Fluorescence (XRF) and X-ray Diffraction (XRD), but conclusive identification of the luminescent phase could not be made. It is concluded that the IRSL signals of this material can be favourable for dosimetry research.

Component-resolved bleaching correlation between OSL and IRSL signals in various geological materials

The primary aim of the present study includes establishing a qualitative as well as quantitative correlation between OSL and IRSL signals in various materials of geological origin, by investigating the influence of the IR stimulation to the OSL signal. The materials which are the subject of the present study include one K-feldspar belonging to the group of microcline, two different grain size fractions of Durango apatite at the edge of the nano-scale and gypsum. A two-step stimulation protocol was applied, including an exposure of the irradiated sample to infrared stimulation for various time and a subsequent continuous wave OSL using blue light. In the framework of a component-resolved analysis, the IRSL decay curves were fitted using analytical equations describing the localized tunneling recombination model; the subsequent OSL decay curves were also fitted using a linear superposition of analytical expressions describing both delocalized and localized recombination processes. The selection of number and type of components in the latter case is also elaborated, based on the physical meaningfulness of the de-convolution results.