CHAPTER ONE (original) (raw)
Related papers
Radiation Measurements, 2012
Pre-dose sensitization of various components of LM-OSL signal of a Nigerian annealed quartz sample has been investigated along side with that of 110 C TL peak in this work. Successive cycles of irradiations and TL/OSL readings using different heating rates were employed to attain pre-dose sensitization. The results showed that the pre-dose sensitization factor of 110 C TL peak depends strongly on the heating rate of thermal activation. The pre-dose sensitization of 110 C TL and all components of RT LM-OSL yield HR dependence on the sensitization after TA. This dependence was ascribed to the different heating time associated with each HR. Sensitization of LM-OSL measured at 125 C generally does not show dependence on HR of TA. This was with the exception of components C 1 and C 3 . Increasing sensitization pattern with increasing HR suggests a correlation between the TL glow-peak at 110 C, the component C 4 of RT LM-OSL and the component C 3 of the LM-OSL signal at 125 C. Extension of the present investigation to diverse quartz kinds from different origins was suggested in order to study the prevalence of the predose sensitization on component C 4 of RT LM-OSL. Finally fast heating is suggested for lower sensitization of fast component while applying OSL dating protocols.
The correlation of fast OSL component with the TL peak at in quartz of various origins
Journal of Luminescence, 2010
The fast component of the optically stimulated luminescence (OSL) signal in quartz is the basic tool for the optical dating. Its relation with the thermoluminescence (TL) glow-peak at about 325 3 C is well established for naturally irradiated quartz. This relationship is also an important part of a general model for quartz on which many theoretical simulations of various OSL experimental results have been based. In the present work this relationship is systematically investigated in nine quartz samples of different origin. The linearly modulated OSL (LM-OSL) curves of all quartz samples for stimulation time less than 50 s consists of two components discriminated easily by a computerized curve deconvolution (CCD) analysis. By comparing the un-bleached to the respective bleached TL glow-curve, it is found that the system of these two fast OSL components is directly related with only a small portion of the electron traps responsible for the TL glow-peaks in the temperature region 2002400 3 C. By increasing the stimulation times, besides the two fast components, the medium and the slow components are also obtained. The medium and slow components are clearly related with the main body of the electron traps responsible for TL glow-peaks in the same temperature region 2002400 3 C. Despite their different origin all quartz samples show an appreciable homogeneity concerning the number and time position of the individual components, whereas, the relative TL/OSL intensities vary strongly from sample to sample with the integrated TL intensity being generally much less than the integrated OSL intensity.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2015
The access to the OSL signals from very deep traps is achieved by an alternative experimental method which comprises combined action of thermal and optical stimulation, termed as thermally assisted OSL (TA-OSL). This experimental technique was suggested in order to not only measure the signal of the deep traps without heating the sample to temperatures greater than 500°C, but also use the former for dosimetry purposes as well, due to exhibiting a number of interesting properties which could be effectively used towards dosimetry purposes, especially for large accumulated artificial doses. The present study provides for the first time in the literature with preliminary results towards the feasibility study of the naturally occurring TA-OSL signal in coarse grains of natural quartz towards its effective application to geological dating. The samples subjected to the present study were collected from fault lines in Kütahya-Simav, Western Anatolia Region, Turkey; independent luminescence approaches yielded an equivalent dose larger than 100 Gy. Several experimental luminescence features were studied, such as sensitivity, reproducibility, TA-OSL curve shape as well as the correlation between NTA-OSL and NTL/ NOSL. Nevertheless, special emphasis was addressed towards optimizing the measuring conditions of the TA-OSL signal. The high intensity of the OSL signal confirms the existence of a transfer phenomenon from deep electron traps. The increase of the integrated TA-OSL signal as a function of temperature is monitored for temperatures up to 180°C, indicating the later as the most effective stimulation temperature. At all temperatures of the studied temperature range between 75 and 260°C, the shape of the signal resembles much the shape of a typical CW-OSL curve. However, a long-lived, residual NTA-OSL component was monitored after the primary, initial NTA-OSL measured at 180°C; the intensity of this component increases with increasing stimulation temperature. The prevalence of these luminescent features was investigated, while the implications on dating applications of these features were also discussed.
Component resolved OSL dose response and sensitization of various sedimentary quartz samples
2007
The 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 • C of quartz in order to investigate the ability of the 110 • C glow-peak to act as a correction factor for all components of the LM-OSL curves examined.
Applicability of OSL pre-dose phenomenon of quartz in the estimation of equivalent dose
Radiation Measurements, 2010
The feasibility of utilizing the pre-dosed OSL signal in the estimation of the equivalent dose has been investigated. The results based on (i) the behavior of growth curve, (ii) dose recovery tests and (iii) nonbleachability of reservoir centres, R-centres, suggests that (i) the pre-dosed OSL does not seem to work satisfactorily in dose estimation unlike the pre-dosed 110 C TL emission and (ii) it may not be applicable in case of bleached specimen.
Radiation Measurements, 2008
The thermally activated characteristics (TAC) of the linearly modulated optically stimulated luminescence (LM-OSL) signals of seven quartz samples from different origin were studied relative to the TAC of their respective thermoluminescence (TL) glow-peaks at 110 • C. Within the framework of the study the TAC behavior of the LM-OSL was investigated by measuring the OSL signal at room temperature (RT) with the 110 • C glow-peak present during OSL measurements, as well as, at 125 • C without the glow-peak at 110 • C removed by a cut-heat at 180 • C prior to OSL measurement. The LM-OSL curves were analyzed into individual components using a computerized deconvolution procedure. It was found that all individual LM-OSL components of each kind of quartz follow the TAC behavior of the respective TL glow-peak at 110 • C. The fourth component of the LM-OSL curve, centered at about t m = 400 s, appeared when the OSL measurements were performed at RT, whereas it was absent when the OSL measurement were performed at 180 • C. It is suggested that this component is closely related with the TL glow-peak at 110 • C.
Radiation Measurements, 2011
Knowledge of the relative luminescence response to alpha and beta radiation is very important in TL and OSL dating. In the present study the relative alpha to beta response is studied in a sedimentary quartz sample, previously fired at 900 C for 1 h, in the dose region between 1 and 128 Gy, for both thermoluminescence (TL) and linearly modulated optically stimulated luminescence (LM e OSL). The LM e OSL measurements were performed at room temperature and at 125 C. All OSL signals were deconvolved into their individual components. Comparison of OSL curves after alpha and beta irradiation strongly supports that quartz OSL components follow first order kinetics in both cases. In the case of TL, the relative alpha to beta response is found to be very different for each TL glow-peak, but it does not depend strongly on irradiation dose. In the case of LM e OSL measurements, it is found that the relative behaviour of the alpha to beta response is different for three distinct regions, namely the fast OSL component, the region of medium OSL component originating from the TL glow-peak at 110 C when stimulation takes place at room temperature and finally the region of slow OSL component. Following stimulation at ambient temperature, the relative alpha to beta response of all components was not observed to depend significantly on dose, with the value of ratio being 0.03 and a tendency to decrease with increasing dose. However, in the case of measurements performed at 125 C, the relative response of the fast components is much enhanced, and for the remaining components it increases with increasing dose. Special care must be taken to examine the relative alpha to beta response of the fast component at 125 C which contrasts the relative response of the TL peak at ca. 325 C. The implications for the dating of annealed quartz are also briefly discussed.
Sources of variability in OSL dose measurements using single grains of quartz
Radiation Measurements, 2005
In luminescence-based measurements of dose distributions in unheated mineral samples, the observed spread in dose values is usually attributed to four main factors: uctuations in the number of photons counted, incomplete zeroing of any prior trapped charge (including signals arising from thermal transfer), heterogeneity in dosimetry, and instrument reproducibility. For correct interpretation of measured dose distributions in retrospective dosimetry, it is important to understand the relative importance of these components, and to establish whether other factors also contribute to the observed spread. In this preliminary study, dose distributions have been studied using single grains of heated and laboratory irradiated quartz. By heating the sample, the contribution from incomplete zeroing was excluded and at the same time the sample was sensitised. The laboratory gamma irradiation was designed to deliver a uniform dose to the sample. Thus it was anticipated that statistical uctuations in the number of photons counted and instrument reproducibility, both quantiÿable entities, should be able to account for all the observed variance in the measured dose distributions. We examine this assumption in detail, and discuss the origins and importance of the residual variance in our data.