On application of low doses from beta radiation source in OSL retrospective dosimetry

Poster zaprezentowany na miedzynarodowej konferencji naukowej 1st International Conference on Dosimetry and its Applications, Prague, Czech Republic, 23-28 June 2013; w formie artykułu, po recenzjach został przyjęty do druku w Radiation Physics and Chemistry (2014); DOI: 10.1016/j.radphyschem.2014.05.045The paper reports on three levels of dose rates obtainable from single beta source: (133±3) mGy/s, (17.8±0.3) mGy/s and (1.94±0.04) mGy/s, as calibrated for quartz sand grains. These values were achieved for different attenuation stages of beta radiation emitted by standard Sr-90/Y-90 source with the nominal activity of 1.48 GBq attached to an automatic luminescence reader. Lower dose rates give opportunity for exact dosing, which is especially required in luminescence dating applied to young samples as well as in environmental dosimetry. Moreover new method for determining time lag in opening the source in the Riso beta irradiator is presented. This allowed to resolve the contradiction appearing in the literature. The time delay was found to be (0.15±0.01) s per single irradiation. For improving accuracy the dose rate correction is suggested to be taken into account for irradiations shorter than 30 seconds

Quartz TL decay due to optical bleaching

In spite of many years of research our knowledge of the traps responsible for the OSL in quartz is not complete. Many papers report the complexity of this signal, determine its components and discuss their usefulness for dating procedures. However the experiments carried out so far do not clearly show the source of carriers which recombine on the luminescence centres emitting the OSL. The trap connected with TL peak around 325 C commonly accepted as easily bleachable, can not be the only one responsible for the many observed OSL components. There should exist TL peaks corresponding to these various OSL components, although it is possible that they are related to very deep traps (that is having large energy of thermal ionisation) which are not detected in the conventional TL measurements carried out up to 500∞C. With this in mind detailed analysis was made, using sedimentary quartz, of TL curves measured after successively increased time of bleaching performed during the OSL measurement. TL components were determined using fitting procedures and the effect of bleaching on each of these components is demonstrated

Analysis of Optical Bleaching of OSL Signal in Sediment Quartz

The aim of this work was to study the effect of the quality of optical bleaching on the results of OSL (Optically Stimulated Luminescence) dating method. The large aliquots of coarse quartz grains extracted from fluvial deposit were used in the study. The poor, medium and good bleaching were simulated in laboratory with help of Blue LED light source in series of experiments. Then the samples were irradiated with a common laboratory dose. The equivalent doses (DE) were measured by the help of standard Single Aliquot Regeneration (SAR) technique, but obtained DE distributions are analysed in a new way. The method for recognizing and compensating for partial bleaching is proposed. The conclusions for dating sediment quartz samples are presented and discussed

Dosimetric features of strontium orthosilicate (Sr2SiO4) doped with Eu2+

Poster zaprezentowany na miedzynarodowej konferencji naukowej 1st International Conference on Dosimetry and its Applications, Prague, Czech Republic, 23-28 June 2013; w formie artykułu, po recenzjach został przyjęty do druku w Radiation Physics and Chemistry (2014); DOI: 10.1016/j.radphyschem.2014.05.043Thermoluminescence (TL) of strontium orthosilicate doped with Eu2+ has been investigated in the range RT- 750 K. Trap parameters of a TL peak at 450 K established by means of glow curve analysis suggest the possibility of applying this sensitive peak for TL dosimetry. The thermal stability test shows that the 450 K peak is partially unstable. The isothermal decay experiments reveal that the traps responsible for this peak can be emptied by a competitive way that is efficient during storage at a constant temperature, and is characterized by lower values of activation energy and frequency factor

Using the TL Single-Aliquot Regenerative-Dose Protocol for the Verification of the Chronology of the Teutonic Order Castle in Malbork

The Teutonic Order Castle in Malbork is one of the precious medieval monuments in Europe. Because of the lack of natural rock resources in Pomerania, its walls are built almost exclusively of bricks. The huge volume and rich historical knowledge about the Malbork Castle makes it a marvellous object for TL dating. The parts of well known age can serve for the verification and improvement of dating method. Subsequently, gained in such way knowledge and experience can be applied for discovering the history of the rest of the castle. Here, the preliminary results of investigations which are still in progress, are presented for 5 brick samples. The applied TL dating procedure is described in detail. The very good accuracy of equivalent dose is achieved by the TL single-aliquot regenerative-dose protocol. The effect of wall inhomogeneity connected with the difference between the activity of the brick and mortar is discussed

Chronostratigraphy of the Vistulian Glaciation (Weichselian) on the Kujawy Moraine Plateau (Central Poland) Based on Lithostratigraphic Research and OSL Dating

The subject of the investigations presented here is fixing dilemmatic character (transgressive or recessive) of the Poznań phase of the Vistulian (Weichselian) Glaciation and answering the question about the possibility of lithostratigraphic separation of this phase from the Leszno phase in the region of so called Vistula lob. Here we present the outcomes of the research project carried out on a few tills exposures, which constitute the sedimentological record of the last ice sheet advance on the Kujawy Moraine Plateau. The absolute ages of 17 samples (collected from fluvial deposits uncovered in the geological logs) have been determined by means of the OSL method applying the single aliquots regenerative (SAR) dose protocol. The OSL data are analysed with regard to supposed bleaching conditions at the moment of the last transport and deposition of the material. In conclusion, some remarks on suitability of fluvial sands for OSL dating are made. In most of the investigated sites, there appears to exist only a single till level associated with the main stage of the Vistulian Glaciation. This fact and the results of OSL dating support the hypothesis, that the Poznań phase in Kujawy Moraine Plateau is not a distinct lithostratigraphic unit, but it is a recessive phase of the last glaciation

The relation between optical bleaching and sedimentological features of fluvial deposits in the Toruń Basin (Poland)

Distributions of equivalent doses (DE) obtained by the Single Aliquot Regenerative-dose (SAR) OSL method applied for large aliquots of coarse quartz grains extracted from fluvial sediments are presented and analysed with respect to a fluvial palaeoenvironment. The Nowe Dąbie and Łochowo fluvial succession from the western part of Toruń Basin (eastern part of Noteć–Warta streamway, Torun-Eberswalde ice-mar ginal valley) was analysed. The fluvial depositional conditions controlling the extent of daylight bleaching are reconstructed by sedimentological studies. The relation between the amount of bleaching and sedimentological properties of fluvial deposits indicate that ripple cross-laminated sands that accumulated on the floodplain and horizontally-bedded sands deposited in shallow channels are more appropriate for OSL dating than sands derived from the deep channel. Along with luminescence results obtained for the river deposits, data measured from an ancient pottery sample, en suring complete reset of the OSL signal, are presented, compared to and discussed. On this base the poorly bleached sediment samples are identified and an adjustment factor is introduced for correcting their OSL dating results in order to avoid age inversion. The application of the adjustment factor is found to minimize overestimation of OSL ages of sediments

Trap spectra of annealed quartz

The trap energy density spectra of natural quartz were investigated by the fractional glow technique. The thermal treatment before excitation induces the changes of thermoluminescence sensitivity as well as the changes of trap spectrum. After annealing at temperature higher than 400 C, a new kind of trap is observed. The frequency factor was determined by the fitting of the theoretical glow curve calculated using the trap depth measured by fractional glow technique to experimental one

A systematic multi-technique comparison of luminescence characteristics of two reference quartz samples

MB did the experiments using the equipment belonging to the Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University in Torun, ul. Wilenska 4, 87–100 Torun, Poland (e-mail: [email protected]) and has been financed by the grant of the National Science Centre, Poland, No. 2018/31/B/ST10/03917.International audienceFurther developments in luminescence dating, dosimetry and temperature-sensing require a deep understanding of luminescence processes and their driving parameters. Natural quartz is one of the most widely used minerals for these purposes. Still, poor reproducibility of results often hampers comparability and credibility of findings in the literature. We identified the lack of suitable natural reference samples as a pivotal problem impeding significant progression. Ideally, basic investigations involve several laboratories working on well-characterised reference quartz samples with different characteristics. Investigations should include multiple complementing methods to analyse luminescence properties and mineralogical and geochemical composition.Here, we present such a multi-technique luminescence comparison of two natural quartz samples. Next to the recently introduced Fontainebleau (FB) reference quartz, we propose another reference sample derived from the ‘Silver Sands of Morar’ (lab code ‘MR’; Scotland, UK). Our experiments confirm that both quartz samples behave fundamentally different in terms of signal composition and sensitivity. The comparative characterisation of both samples targeted electron traps via thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques and luminescence centres via radioluminescence and time-resolved OSL spectrometry. In summary, we conclude that all observed differences are likely the results of divergent defect concentrations rather than variances in defects' composition (nature). The measurement data of our study are accessible open-access for inspection by others