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Yayın Component resolved OSL dose response and sensitization of various sedimentary quartz samples(Elsevier Ltd, 2007-02) Güneç Kıyak, Nafiye; Polymeris, George S.; Kitis, GeorgeThe structure of the linearly modulated optically stimulated luminescence (LM-OSL) signal was studied for four sedimentary quartz samples, collected from different sites around Istanbul, Turkey. Applying a computerized deconvolution analysis to the LM-OSL curves, at least six individual components of first-order kinetics were identified and photoionization cross-section of each component was evaluated. The OSL dose-response curve of each component for each quartz sample was obtained, showing a remarkable differentiation from component to component. The behavior of a highly dosed sample to successive LM-OSL measurements was also studied showing a stable recuperation signal in the position of the "slow" and "medium" components and high resistance to OSL bleaching of the "slow" component. The individual sensitivity of each component as a function of the activation temperature was obtained. The sensitivity of each component was normalized over the respective sensitivity of the glow-peak at 110 degrees C of quartz in order to investigate the ability of the 110 degrees C glow-peak to act as a correction factor for all components of the LM-OSL curves examined.Yayın Thermally assisted OSL from deep traps in Al2O3:C(Pergamon-Elsevier Science Ltd, 2010-03) Polymeris, George S.; Raptis, Spyridoula; Afouxenidis, Dimitrios; Tsirliganis, Nestor C.; Kitis, GeorgeThe present work suggests an alternative experimental method in order to not only measure the signal of the deep traps in Al2O3:C without heating the sample to temperatures greater than 500 degrees C, but also use this signal for high dose level dosimetry purposes as well. This method consists of photo transfer OSL measurements performed at elevated temperatures using the blue LEDs (470 nm, FWHM 20 nm) housed at commercial Riso TL/OSL systems, after the sample was previously heated up to 500 degrees C in order to empty its main TL dosimetric trap. The influence of this procedure on specific features such as glow curve shape and sensitivity of the main TL glow peak was also studied.Yayın Effect of annealing temperature on determining trap depths of quartz by various heating rates method(Pergamon-Elsevier Science, 2001-12) Güneç Kıyak, Nafiye; Buluş, E.The aim of this study is to determine the trap parameters (trap depth E, frequency factors) of quartz using various heating rates method and also to investigate the effect of annealing temperature on determining trap depths. The method is based on the positions of the thermoluminescence peaks, obtained from the change in temperature of the peak at maximum caused by changing the heating rate at which the sample is measured. In the present work, powder quartz samples were annealed first at different temperatures before irradiation. Then samples irradiated to different doses were measured with a TL reader at different heating rates and the glow curves were recorded. In order to calculate the trap depth E and the frequency factor s, the glow parameter T-m was determined experimentally from the glow curve by measuring the shift of the maximum peak temperature depending on heating rate beta. The calculation of trap parameters was repeated for each annealing temperature. Then the effect of annealing temperature on trap depths calculated by the various heating rates method was evaluated.Yayın Luminescence ages of feldspar contaminated quartz from fluvial terrace sediments(Wind-J Wojewoda Publ Co, 2008-01-01) Güneç Kıyak, Nafiye; Erturaç, Mehmet KorhanThis study focuses on obtaining luminescence ages in feldspar contaminated quartz from well-developed fluvial terraces of the Yesilirmak (Iris) river located inside the eastern North Anatolian Fault Shear Zone (NAFZ). We applied a technique based on conventional single-aliquot regenerative-dose (SAR) protocol, modified with an IR pre-treatment to reduce the OSL contribution from feldspar for accurately measuring the dose in quartz. All investigated samples showed an ability to measure a beta dose given in the laboratory, a so called dose recovery test. The dependence of the equivalent dose on thermal treatment was also examined. Dose rate calculations were based on spectral analysis of gamma measurements by a field spectrometer on site. The efforts to establish a chronology using the IR modified SAR technique produced reliable dose results in stratigraphic order. Results were reproducible and grouped broadly between 35-109 ka for Bektemur, 32-36 ka for Kizilca, 19-47 ka for Aksalur and 35-44 ka for Sahinkaya. Obtained results show that the studied area was controlled by tectonic activities within the last 50 ka and the sample Aksalur 2 was the loess deposit formed by aeolian activity.Yayın TL/OSL properties of crystalline inclusions from heavy, barytes loaded, concrete(Pergamon-Elsevier Science Ltd, 2010-03) Güneç Kıyak, Nafiye; Polymeris, George S.; Kitis, GeorgeIn 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.
