Optically Stimulated Luminescence Technique Research Articles

Surface mount multilayer ceramic capacitors as optically stimulated luminescent dosimeters

The choice of dosimetric materials for precise retrospective dose assessment in case of any emergencies is very challenging. Since few decades, electronic components like ceramic resistors, inductors, IC chips, surface mount resistors and inductors have been proven to be suitable candidates for dose estimation using thermoluminesce (TL)/optically stimulated luminescence (OSL) techniques. In this work, OSL technique is applied to study dosimetric properties of surface mount multilayer ceramic capacitors (SM MLCC) available in commonly used instruments like printer, computer mouse, USB flash drive and personal gadgets like mobile phone etc. To understand the OSL process involved, the elemental composition and crystallinity of the SM MLCCs were analyzed using Fourier transform infrared (FTIR) and X-ray diffraction (XRD) techniques. It is found that the main constituent is barium titanate with aluminium silicate as major impurity along with some trace elements and is responsible for the origin of the radiation induced OSL signal. Some important dosimetric characteristics like OSL sensitivity, repeatability, OSL dose response, and OSL signal stability upon storage were studied. The stimulation time was optimized as 50 s and used for all OSL measurements. The dose response was found to be linear from 500 mGy to 15 Gy and simply increased (up to 40 Gy). Fading analysis showed that the OSL signal decreases by ∼ 25 % in 1 day, ∼ 50 % in 4 days, and remained stable after that at least up to 8 days. The dose was recovered using single aliquot regenerative-dose (SAR) technique with very good accuracy. These results of dosimetric studies and validation study suggest that surface mount multilayer ceramic capacitors have potential use as retrospective dosimeters.

Further characterization of BeO detectors for applications in external and medical dosimetry

Measuring absorbed doses with high precision and accuracy for clinical applications using Optically Stimulated Luminescence (OSL) dosimeters can help to optimize treatment to patients. Beryllium Oxide (BeO) is a nearly tissue-equivalent material that has the potential to increase the applicability of OSL dosimetry in medical dosimetry, but there has been limited research into its characterization. We present here the characterization of BeO dosimeters in terms of annealing temperature and duration, the effect of preheat treatment on short-term fading, energy and angular dependence, and discuss possible errors in laboratory conditions by using the OSL technique. Shorter readoutof 30 s when using stimulation power of ∼30 mW cm2 is feasible but preheating then becomes necessary. The fading behavior of BeO was found to be dose-dependent in this case. Reproduciblity of an OSL measurement with repositioning of the dosimeter in the reader and for the short reaout times was found to be ∼1%. Energy response was close to the theoretical values, which agrees with some but differs from other published studies, indicating that the OSL efficiency might vary. The angular dependence presented the greatest uncertainty factor. In summary, BeO dosimeters have the potential to be used in clinical applications for dose evaluation. However, care should be taken while handling and applying an optimized measurement procedure is necessary due to the complex luminescence mechanism of the material.

An overview study on the TL and OSL dosimetry patent processes over time

Since its discovery, ionizing radiation has been used in many different applications. Materials and methods have been developed to measure and quantify radiation doses. Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) are two techniques used for radiation dosimetry. Both TL and OSL are primarily applied in several areas, such as dating of ancient materials, equipment quality control and individual monitoring. One of the parameters to measure the knowledge and development of a technology is the number of patents related to the field. In this work, we established a methodology for patent search on the World Intellectual Property Organization (WIPO) database aiming to review the development of TL and OSL dosimetry over time. We concluded that along with the OSL technique development, the TL technique should continue to be explored in radiation dosimetry.

Luminescence dating and firing temperature determination of ancient ceramics fragments from the Tunata-hill site in the Churajon archaeological complex in Arequipa, Peru

Ancient pottery fragments from the Tunata-hill site in Churajon archaeological complex, Arequipa, Peru, were dated by means of luminescence techniques such as thermoluminescence (TL) and optically stimulated luminescence (OSL) in order to provide absolute chronology. For TL, additive and regenerative methods were performed. For OSL a regenerative method was carried out for IRSL dating. A rigorous description of the study area and its context has been made. The ages of the samples were found to be between 0.50 ± 0.06 ky and 0.49 ± 0.03 ky for TL methods, and 0.49 ± 0.02 ky for OSL methods. On average, the estimated age by TL and OSL techniques is 490 ± 70 yr (1600 AD and 1460 AD). This means that Churajon ceramics under study would belong to the Late periods which corresponds to the Inca region, and the North sub-region of the Late Churajon phase, and the beginning of European colonization in Peru. X-ray fluorescence technique (XRF) analysis has shown the main presence of Fe (39.5%), Si (30.0%), and Al (10.4%) in fine pottery powder. Furthermore, the electron paramagnetic resonance (EPR) technique was used to study the firing temperature using the iron signal (Fe3+) as a firing temperature reference. The firing temperature of ceramics was found to be around 550 ± 50 °C.

TL and OSL characteristics of the fluoroperovskite KMgF3:Eu,Yb, Li for dosimetry applications

The purpose of this work was to investigate the dosimetric and luminescence properties of the novel KMgF3:Eu0.5%,Yb0.1%,Li15% fluoroperovskite synthesized using the sol-gel method. The luminescence signals were characterized using Optically Stimulated Luminescence (OSL) spectra, Linearly-Modulated OSL (LM-OSL), Continuous-Wave OSL (CW-OSL), and Thermoluminescence (TL) techniques. The blue light (470 nm) stimulated OSL associated with Eu2+, and Eu3+ emissions was correlated with the TL peaks up to 300 °C. The photoionization cross-section of each OSL component was evaluated using deconvolution analysis following two different optical stimulation modes, namely LM-OSL and CW-OSL. The activation energy values were evaluated using the Tm-Tstop and CGCD methods. OSL signal fading of 5% and 13% was observed at the end of 24 h and over the next three months, respectively. The results indicate that the OSL from KMgF3:Eu0.5%,Yb0.1%,Li15% fluoroperovskite has suitable properties for dosimetry, including high sensitivity to ionizing radiation and a wide linear dose range (0.1–500 Gy). These results enhance the understanding of the origin of the luminescence properties in this material and this work paves the way toward its utility for dosimetry purposes.

Extended-Range Luminescence Dating of Central and Eastern Amazonia Sandy Terrains

The Amazonia biome hosts upland closed and open vegetation ecosystems, in which the current biogeographical patterns relate to the evolution of the physical landscape. Therefore, understanding the origin and timing of the substrates supporting different ecosystems is indispensable for better comprehension of Amazonian biogeography. Here we used quartz optically stimulated luminescence (OSL) and thermally transferred optically stimulated luminescence (TT-OSL) for dating sandy substrates of closed and open vegetation environments in Central and Eastern Amazonia, from both outcrop and drill core samples (Autazes core: PBAT-15-43). These sandy substrates present ages ranging from 1 ka up to almost 2 Ma, that were primarily interpreted as depositional ages of fluvial terraces. Moreover, ages are discussed in terms of potential geomorphic processes leading to the formation of substrates, such as soil mixing and apparent age of quartz from the parent bedrock. The coupling between OSL and TT-OSL techniques allow us to date sedimentary deposits covering the whole Quaternary, which implies a new time window for the Amazonia history.

Dating stone arrangements using optically stimulated luminescence and fallout radionuclides

AbstractBuildings and monuments constructed from stone provide some of the best‐preserved surface archaeology, but their construction ages can be difficult to determine using radiocarbon techniques. In Australia, stone arrangements are recognised as architectural or symbolic features belonging to Aboriginal societies. The structures are predominantly inorganic with shallow infill, hampering attempts to determine their antiquity. Optically stimulated luminescence (OSL) techniques have the potential to date these features, but their complex geometry requires careful consideration of the background radiation. Here, we present the first ages for Australian Aboriginal stone construction using single‐grain OSL techniques on quartz from stone arrangements in central Australia. Beta and gamma dose rates and the cosmic ray dose have been estimated from mapping the gross geometry of stone and sand courses. The resulting OSL ages are internally consistent and, together with fallout radionuclides 137Cs and 210Pb, indicate a minimum age for construction between 1959 and 1981 AD. We demonstrate that single‐grain OSL techniques can be used to determine the age of emplaced sand between stones and, assuming a stable substrate, can be used to date stone building construction as well as building occupation, providing chronologies for sites where organic material for radiocarbon analysis is limited or unavailable.

Luminescence characteristics of perovskite type LaAlO3:Dy3+ for radiation detector

Thermally and Optically Stimulated Luminescence (OSL) are known stimulated phenomena in condensed matter that can be used for luminescent material characterization. Both thermally and optically processes have become a successful practical tool in radiation dosimetry. Special attention is dedicated to bioceramic as a material of choice for many dosimetric applications. This paper reports experimental results of dysprosium trivalent ion doped lanthanum aluminate (LaAlO3:Dy3+) using thermally stimulated luminescence (TSL) and optically stimulated luminescence (OSL) techniques. Samples of LaAlO3:Dy3+ were irradiated to beta doses, in air, from 1.6 Gy up to 26 Gy and then were analyzed using both TL and OSL techniques to determine their luminescent properties. Nanostructured powders were confirmed by the X-ray diffraction technique. Luminescent phosphors show a thermoluminescent glow curve obtained being exposed beta radiation of two peaks: one located at around 160 °C and the second one at 215 °C. Meanwhile, OSL decay is exponential form. TL and OSL response as a function beta radiation dose was linear in the studied dose interval (from 1.6 Gy up to 26 Gy). The very good sensitivity and moderate fading will make this phosphor suitable for beta radiation detection, using both TL and OSL techniques.

OSL dating of Zhuangbianshan site in the humid subtropical coastal region of China

Establishing a reliable chronology is the basis of archaeological research; this is normally undertaken using radiocarbon dating and, more recently, optically stimulated luminescence (OSL). The application of the latter to Neolithic sites in the Fujian Province of China is still quite limited. In this study, a total of eight OSL samples were collected from the Zhuangbianshan site (ZBS). The single‐aliquot regenerative‐dose (SAR) protocol was applied to coarse silt (38–63 μm) quartz. The results showed that the 38–63 μm grains appeared to be well bleached. The ages for the samples range from 5.5 to 3.3 ka for the ZBS sections, which is in general internally coherent within the limits of experimental errors and with respect to their stratigraphical order. Two OSL ages (ZBSH03‐2 and ZBST05H) of the ZBS were significantly older than their expected archaeological ages, while most of those from the ZBS core generally showed good agreement with their archaeological ages and stratigraphical succession. Based on the OSL ages, two periods (~6.3 and 3.5–3.3 ka, approximately) of rapid cultural accumulation can be identified at this site. These investigations indicate that the OSL technique is an effective method with which to date Holocene cultural accumulations, especially sites in the humid subtropical areas of South China where organic carbon material is sparse.

A systematic study on luminescence characterization of lanthanide-doped BeO ceramic dosimeters

This work aimed to investigate the luminescent characteristics of lanthanide and alkali metal ion-doped BeO ceramic pellets prepared using the co-precipitation synthesis technique for Optically Stimulated Luminescence (OSL) dosimetry applications. In this study, BeO nano phosphor was doped with lanthanides (Ln3+) Eu3+, Ce3+, Nd3+, Yb3+, Er3+, Gd3+, Tb3+, Tm3+, Sm3+, Pr3+, and Dy3+ and co-doped with Na+, and characterized using radioluminescence (RL), thermoluminescence (TL) and OSL techniques. Lanthanides introduced as dopants not only affected the luminescence centers but also changed the luminescence mechanisms. The RL spectra of lanthanide-doped BeO samples showed that they mostly possess dominant emissions in the narrow bands (between 200 and 450 nm) in the UV region. OSL emission bands were found to be located between ~250 and ~390 nm. The results have demonstrated that the incorporation of appropriate Ln3+ and alkali metal ion dopants and their optimum concentrations enhanced the luminescence intensity of undoped BeO. The studied BeO:Na5%,Ce0.01%,Er0.01%, BeO:Na5%,Ce0.005%,Tb0.05%, and BeO:Na5%,Ce0.01%,Dy0.01% ceramics can be regarded as highly sensitive controllable luminescence dosimeters. The range of sensitivity of those samples is such that their most probable use in clinical therapy dosimetry rather than in health physics.

Extending the range of optically stimulated luminescence dating using vein-quartz and quartzite sedimentary pebbles

The feasibility of applying optically stimulated luminescence (OSL) techniques to obtain estimates of the burial age of lithic clasts in the form of pebbles of quartzose lithology is investigated in this study. We applied OSL measurement procedures to vein-quartz and quartzite pebbles from contexts at five sites with fluvial and coastal beach contexts of depositional age ranging from 500 ka to the mid Holocene. As in previous OSL studies with lithics, measured depth-dose profiles were interpreted to identify regions associated with key stages in the burial history of the pebbles, including the extent of pre-burial optical resetting, primary burial and any subsequent secondary stages of exposure to sunlight. While some of the pebbles had not been fully optically reset before burial, none were in field saturation, as commonly encountered with larger lithic clasts such as cobbles. The relatively low concentrations of radionuclides within vein-quartz and quartzite pebbles simplified the assessment of the radiation dose rate. OSL age estimates consistent with independent dating evidence were obtained for the three sites sampled in the UK (Langford Quarry, Leet Hill Quarry, Swanscombe Skull Site and Barnfield Pit) and one of two sites tested in Portugal (Forte Cão), whereas evidence of secondary optical bleaching detected in pebbles from a second site (Vale de Atela) underestimated the independent age for primary burial. The oldest depositional age of the contexts tested was ~500 ka (Leet Hill Quarry), and for some of the pebbles tested there was the capacity to extend the potential dating range further as the age equivalence of the limiting value of D e was in excess of 1 Ma. The advantages of working with smaller, portable, clasts in the form of pebbles and with a lithology of higher transparency opens up a wide range of potential applications, whether the depositional processes are environmental or anthropogenic in origin or modification. • New approach to the dating of Quaternary sediments containing vein-quartz and quartzite pebbles. • OSL techniques applied to sliced pebble cores produce depth-dose profiles that are related to optical exposure history. • Successful comparison of OSL ages with independently dated MIS 12, MIS 11, MIS 5 and Holocene depositional contexts. • Low dose rates for vein-quartz and quartzite pebbles potentially enable further extension of the dating range.

Luminescence characteristics of newly-developed MgB4O7:Ce3+,Na+ phosphor as an OSL dosimeter

In this study, dosimetric properties of Ce3+ and Na+ doped magnesium tetraborate (MgB4O7) phosphors synthesized by the solution combustion synthesis (SCS) method were investigated using optically stimulated luminescence (OSL) technique to develop OSL radiation dosimetry. The concentrations of Ce3+0.3%wt and Na+1–14%wt dopants in MgB4O7 were incorporated into it to improve the efficiency of luminescence. The results showed that the effect of Na+ substitution on MgB4O7:Ce3+0.3%wt lattice induced a remarkable improvement of both its thermoluminescence (TL) and OSL signals. The highest OSL signal of the synthesized phosphor was recorded at the MgB4O7:Ce3+0.3%wt,Na+14%wt phosphor. Its TL glow curve consists of two peaks located at ~70 °C and ~230 °C with a heating rate of 2 °C/s. These TL peaks were found to be optically sensitive to blue light excitation (λ = ~470 nm). X-ray diffraction (XRD), scanning electron microscopy (SEM), radioluminescence (RL) techniques have been employed to characterize the synthesized phosphor. The XRD pattern of MgB4O7:Ce3+0.3%wt,Na+14%wt phosphor with orthorhombic phase was observed in the specimen sintered at 900 °C. The RL spectrum of the MgB4O7:Ce3+0.3%wt,Na+14%wt phosphor revealed a strong and a weak emission peak located UV and red regions, respectively. OSL dosimetric properties of the phosphor were studied under beta radiation of 90Sr/90Y. The phosphor exhibited good linearity between 1 and 100 Gy. Minimum detectable dose (MDD) of the phosphor was calculated as 0.73 mGy. A good reusability property was determined up to 20 experimental cycles with a deviation of 4.5%. Short-time fading up to 24 h and long-time fading up to 4 weeks were studied. The results shows the MgB4O7:Ce3+0.3%wt,Na+14%wt phosphor can be proposed as a potential OSL dosimetry for radiation dose measurements in medicine using OSL technique.

APPLICATIONS OF OPTICALLY STIMULATED LUMINESCENCE IN MEDICAL DOSIMETRY.

If the first decade of the new millennium saw the establishment of a more solid foundation for the use of the Optically Stimulated Luminescence (OSL) in medical dosimetry, the second decade saw the technique take root and become more widely used in clinical studies. Recent publications report not only characterization and feasibility studies of the OSL technique for various applications in radiotherapy and radiology, but also the practical use of OSL for postal audits, estimation of staff dose, in vivo dosimetry, dose verification and dose mapping studies. This review complements previous review papers and reports on the topic, providing a panorama of the new advances and applications in the last decade. Attention is also dedicated to potential future applications, such as LET dosimetry, 2D/3D dosimetry using OSL, dosimetry in magnetic resonance imaging-guided radiotherapy (MRIgRT) and dosimetry of extremely high dose rates (FLASH therapy).

A newly developed OSL dosimeter based on beryllium oxide: BeO:Na,Dy,Er

This study aims to develop a high sensitivity Optically Stimulated Luminescence (OSL) dosimeter based on tissue-equivalent BeO:Na,Dy,Er ceramic (Zeff = 7.31) using the precipitation method. The material structure was confirmed by performing X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDS) analyses. Thermoluminescence (TL), OSL, and X-ray luminescence (XL) techniques were used for the investigation of the luminescence properties. BeO:Na,Dy,Er has two TL peaks located at ~170 and 350 °C (at a heating rate of 2 °C/s) found to be associated with the OSL signals using the step annealing procedure. The OSL signals of newly developed BeO:Na,Dy,Er pellets were found highly sensitive to beta radiation and almost linear with a linearity coefficient of 1.03, i.e., described by a relation y=a+bx1.03at a range of 0.1–50 Gy. We investigated that the sensitivity of OSL from BeO:Na,Dy,Er pellets is the same after repeated exposure and reprocessing. Except for instability in short storage times, negligible long-term OSL signal fading was observed for up to three months at ambient temperature, in dark. In XL analyses, a broad band emission from 200 nm to 500 nm was observed at different dopant concentrations. The OSL characteristics of this material were found to be very encouraging and convenient for personal and medical dosimetry applications.

Radiation dosimeter utilizing optically stimulated luminescence of BeO:Na,Tb,Gd ceramics

This paper presents a systematic study of a new Optically Stimulated Luminescence (OSL) dosimeter based on BeO:Na,Tb,Gd ceramics synthesized using precipitation method. We confirm the product performing X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) analyzes. Luminescence signals are characterized by Thermoluminescence (TL), Radioluminescence (RL), and OSL techniques. BeO:Na,Tb,Gd ceramics have two TL peaks located at ∼180 and 370 °C associated with the OSL signals. Thermal quenching energies were evaluated as 0.52 eV using the OSL signals obtained at various readout temperatures and 0.55 eV using TOSL method. The results demonstrate that the OSL signals of BeO:Na,Tb,Gd ceramics with high sensitivity, dose linearity, low-fading, reusability, and thermal stability are very encouraging and convenient for medical applications.

Dating and determination of firing temperature of ancient potteries from Yumina archaeological site, Arequipa, Peru

Pottery fragments from the Yumina archaeological site, Arequipa, Peru, were dated by means of thermoluminescence (TL) and optically stimulated luminescence (OSL). Electron paramagnetic resonance (EPR) technique was used to study the firing temperature using the iron signal (Fe3+) as a firing temperature reference. The ages of the samples were found to be between 1190 ± 30 and 1240 ± 80 years (777 ± 80 and 827 ± 30 A.D.) determined by both techniques. The firing temperature of ceramics was found to be around 550 ± 50 °C. Our study, based on the combination of TL and OSL techniques to study Yumina archaeological site pottery, will be helpful for archaeologists in Peru. With the results of this investigation, we can understand the chronology and determine the areas of dispersion and density of the archaeological occupation in the Arequipa Valley. In addition, the calculated ages are consistent with the occupation period of the Yumina archaeological site estimated by stratigraphic analysis of the potteries.

Luminescence dating of sediment mounds associated with shaft and gallery irrigation systems

Optically stimulated luminescence (OSL) techniques, supported by geomorphological analysis, have been applied to date the construction of shaft and gallery irrigation systems, more commonly referred to as qanats, falaj and foggara. The approach developed was tested on four hydraulic systems located in semi-arid landscape settings, three in Murcia, Spain, and the fourth in the Sus Tekna region, Morocco. Excavation of the characteristic sediment mounds that surround each ventilation shaft enabled a detailed examination of strata containing upcast deposits and their assignment to the main stages in the construction and use of the hydraulic feature. OSL techniques with single grain resolution applied to samples taken from the key strata provided age estimates for their deposition on the mound and, from these, dating of the construction and use of the system. Of the four irrigation systems analysed, the OSL dates indicated that the youngest had been constructed in the 19th century AD and the oldest, located in Murcia, was dated to the Roman period. The latter is of archaeological significance because the introduction of this particular form of hydraulic technology to Spain is widely identified as an Islamic innovation of the early 8th century AD.

Luminescence dating of weathered sediments from the Paleolithic site of Fengshuzui in northern Hunan province, China

Abstract South China is an important region for the investigation of the origin of modern humans and the dispersal of Homo sapiens in Asia. However, the accurate dating of Paleolithic sites, especially for open-air sites, in the region has been difficult due to the lack of datable materials like bones that were destroyed due to intense chemical weathering. In this study, we applied optically stimulated luminescence (OSL) dating techniques to the Paleolithic site of Fengshuzui in south China, in which the deposits are intensely weathered. We first investigated the degree of chemical weathering of the deposits and the effect of weathering on dose rate, and then measured the equivalent dose of quartz extracts from five sediment samples from a ∼5 m thick archaeological section. The contents of mobile and immobile elements determined by different analysis methods show that the studied sediments are homogenous in chemical and mineral compositions. Enrichment or depletion of major and trace elements including U and Th were not detected. The sediments consist of ∼60% quartz, ∼30% illite and ∼6% feldspars, ∼3% kaolinite and ∼2% hematite. The calculated chemical weathering indices show that the sediments have been intensely weathered, and the weathering degree of the five studied samples at different depths are similar. Radioactive disequilibrium in the uranium decay series caused by weathering was not detected. All these indicate that the effect of chemical weathering on dose rate is negligible for our samples. The quartz extracts displayed excellent luminescence characteristics, and the five samples, from bottom to top, were dated to 123 ± 7, 98 ± 5, 98 ± 4, 81 ± 3, 68 ± 2 ka, respectively. The ages of the cultural layers range from 100 to 70 ka, mainly corresponding to MIS 5. This also implies that the OSL techniques can be employed to date open-air sites in south China, but the effect of weathering on dose rate should be investigated on a case by case basis.

Performance of TL and OSL techniques using CaSO4 and Al2O3 dosimeters for mean glandular dose (MGD) and entrance surface skin dose (ESD) determination in a digital mammographic unit as alternative dosimeters

The mammography is the most important and simple tool in the diagnosis of breast diseases in women. In digital mammography, the process of image acquisition, display and storage are separated which allows optimization of each. Despite the innumerous advantages of this technique, such as an accurate diagnosis for women with dense breast, it was noticed an increase of radiation doses to obtain the images by this system. As with any examination that includes x-rays, there is always a small stochastic risk of inducing cancer, it is therefore important to evaluate the risk from the dose delivered to the patient during the screening process. The mean glandular dose within the breast is the recommended quantity to evaluate the risk from radiation to the breast. To guarantee proper conditions of protection for patients, the radiation dose should be as low as reasonably achievable possible and simultaneously compatible with image quality requirements. Thus, this work proposes the use of the thermoluminescent (TL) CaSO4:Dy sintered discs, produced at IPEN, widely used in individual, environmental and area monitoring in Brazil, and Al2O3:C optically stimulated luminescence (OSL) ‘dot’ dosimeters, manufactured by Landauer® Inc., as application as easy-to-use and low cost alternative dosimeters to evaluate the entrance skin doses (ESD) delivered to patients, the half value layer (HVL) and the mean glandular doses (MGD) in a mammographic digital unit, comparing these two techniques with the results obtained using an All-in-one QC meter. The results obtained demonstrated that the TL and OSL dosimetry systems and the CaSO4 and Al2O3 dosimeters used are able to evaluate the entrance skin dose as well as mean glandular doses in a digital mammographic unit accurately within the requirements, and they can be considered a practical, simple, easy-to-use and low cost tools for verification of these items in a Quality Assurance Program.

Evaluation of the thermally and optically stimulated response of an Italian Obsidian irradiated in 60Co beams

From Obsidian silicate, in its natural form, pellets were manufactured adding Teflon to the material in powder. These pellets were exposed to the gamma radiation beams of a 60Co source in a dose interval from 10 Gy to 10 kGy. The Obsidian in powder was investigated in relation to its physical and chemical characteristics, by means of the X-ray diffraction, scanning electronic microscopy and energy-dispersive X-ray spectroscopy techniques. After the irradiation procedure, the signal of the samples was evaluated by means of three techniques: thermoluminescence (TL), optically stimulated luminescence (OSL) and thermally stimulated exoelectron emission (TSEE). The objective of this work was to verify the TL, OSL and TSEE response of the Obsidian+Teflon pellets after exposure to high doses of gamma radiation. Different response characterization tests were performed, as TL and TSEE emission curves, OSL signal decay, reproducibility, dose-response curves, lower detection limits and fading. From these results, it can be observed that the Obsidian+Teflon pellets present good conditions to be used as high dose gamma radiation detectors; the results obtained with the OSL technique were the most adequate in terms of response in function of absorbed dose. The fading of the signals, varying from about 26% (TSEE) to 44% (OSL), in a time interval of 360 h post-irradiation, also showed favorable results for the use of this material as radiation detector, when the measurements are taken after a defined time interval.