Eren Şahiner

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.

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.

TL and OSL dose response and stability properties of various commercially glass samples obtained from Turkey for dosimetric purposes in the UV emission spectral region

This paper reports Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) dose response characteristics of ten different commercial glass samples collected from Turkey. Nowadays, glass samples are widely used mostly in objects of everyday life. The study focuses to both TL and OSL dose responses, through a dose region within 1 and 512Gy. Lowest detectable dose limit (LDDL) as well as the respective linearity features of the corresponding dose response curves were studied for both TL and OSL. Moreover, signal reproducibility and fading behaviors have also been studied in detail. For specific samples, the lowest detectable dose was yielded at 2Gy, making thus these samples appropriate for retrospective dosimetry applications. Nevertheless, based on the features reported in the present study, the majority of the samples could be possibly used effectively for dosimetric applications of higher doses in the UV region emission.

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.