Nanoparticle-enhanced thermoluminescence in silica gels

The results of transmission electron microscopy and thermoluminescence (TL) studies in silica samples containing Fe and Cu nanosized particles show an important enhancement of their TL response when compared with known reports for pure silica samples. The effect of surface electronic states in the nanoparticles, interacting with the matrix, may be responsible for this new size-dependent effect.     

Natural thermoluminescence in some feldspars

Natural thermoluminescence (NTL) in some feldspars namely microcline, orthoclase, albite and oligoclase has been investigated. The study reveals the existence of as many as four peaks in the NTL of both microline and albite in the temperature range 200 to 400° C, whereas in the case of orthoclase three peaks could be located. The results are discussed in the light of the findings of the previous workers. Some of the NTL peaks observed in this study are analysed by curve fitting method, and their trapping parameters, namely thermal activation energy (E), frequency factor (sn ₀) and order of kinetics (b) established. A one to one correspondence between these peaks and the ones observed in the laboratory X-ray-irradiated sample is demonstrated.     

Topology-dependent thermoluminescence kinetics

Standard kinetic models for thermoluminescence (TL) relate to the simple trap model (STM) and the model of localised transitions (LT). This paper presents a review of TL properties in various spatially correlated systems (SCS), which span the two limiting cases. A classification of kinetic models for SCS is proposed. Numerical results are presented for the isolated clusters model (IC) and the interacting one-dimensional (1-D) and three-dimensional (3-D) systems. For these systems an influence of external electric field on TL is demonstrated. Analytical formulation for the IC model is possible using trap structural functions (TSFs). To calculate the TSFs (analytically or numerically) it is convenient to use their structural and symmetry properties. Analytical equations are presented also for the semi-localised transitions (SLT) model, which is a generalised version of LT. It is shown that in some cases the SLT model leads to the cascade detrapping (CD) phenomenon. The CD mechanism produces very narrow TL peaks that are apparently well described by the first order kinetics with very high frequency factors and very high activation energies.     

Mechanism of thermoluminescence in magnesium oxide

Thermoluminescence (TL) induced by γ-rays in nominally pure polycrystalline MgO powders has been investigated. In addition to a high temperature peak around 650 K, which is also present in the unirradiated specimens, TL glow peaks are observed around 365, 435, 510 and 545 K. The role of transition metal impurities on TL behaviour has been studied by the doping technique. It is observed that Cr³⁺, Mn²⁺ and Ni²⁺ act as emission centres while Fe³⁺, Co²⁺ and Cu²⁺ act as quenchers. For a particular sample all γ-induced glow peaks give a similar emission spectrum which is characteristic of the activators present. Optical bleaching, isothermal decay and ESR studies have been used to study the trapping centres. It is shown that the charge carriers involved are holes from V-type defects. The dominant 365 K peak has been assigned to V_M centres. A hole-release mechanism involving recombinations with electrons trapped at activators is proposed to explain the TL behaviour. Based on the thesis submitted by A. Sathyamoorthy to the University of Bombay (1976).     

Phototransferred thermoluminescence for use in UVB dosimetry

Results are reported of a study of phototransferred thermoluminescence (PTTL) as a potential method for ultraviolet (UV) radiation dosimetry using several different TL materials. The materials studied in depth include Al2O3:C, CaF2:Cu, MgO and MgO:Cu. The experimental features discussed in this paper include the PTTL response as a function of exposure time at 307 nm and the PTTL wavelength dependence over the range 250-450 nm, using a fixed photon flux at the sample. The study confirms the attractive properties of Al2O3:C as a UV dosimetry material, while CaF2:Cu is shown to have potential as a UVC dosemeter.     

Thermal quenching of thermoluminescence in natural quartz

The thermal quenching properties of the thermoluminescence (TL) from several natural quartz specimens were examined, at two different wavelengths, using the heating rate dependence of the TL signal. As the heating rate varies the TL peaks shift to different temperatures and become affected by thermal quenching to different extents. In this work the heating rate was varied over several orders of magnitude and, through deconvolution of the TL glow curve the behaviour of the main TL peaks was followed as a function of the temperature at which the peak appeared in the glow curve. Through an analysis of the glow peak areas as a function of glow peak temperature the decrease in the efficiency of TL production with increasing temperature could be monitored, at the different emission wavelengths. The analysis supports the contention that the quenching phenomenon is a result of a Mott-Seitz mechanism.     

Non-monotonic dose dependence of thermoluminescence

The thermoluminescence (TL) intensity in different materials is usually a monotonic increasing function of the dose, which quite often reaches a saturation value. In several materials, however, non-monotonic dose dependence has been observed. The TL intensity reached a maximum at a certain dose and decreased at higher ones. Some authors refer to this effect as 'radiation damage'. In the present work, we show that the non-monotonic dependence can easily be demonstrated to result from competition between transitions model with two trapping states and two kinds of recombination centres. Two kinds of competition are considered. One in which competition during excitation dominates, the filling of the active luminescence centre is non-monotonic, and the resulting TL is non-monotonic. In the other, the filling of traps and centres is monotonically increasing, but the competition during heating causes TL intensity to reach a maximum and decline at higher doses.     

High dosage thermoluminescence diamond dosimeters

Diamond thin films have been irradiated with high doses (up to 12.8 kGy) of ⁹⁰Sr beta particles. The diamond thin films have been synthesized from commercial Tequila as a precursor using Pulsed Liquid Injection by the Chemical Vapor Deposition (PLICVD) technique reported recently. Thermoluminescence (TL) phenomena at these doses exhibit peak curve shift to higher temperatures (from 370 to 440 K) in the glow curve and the integrated TL curve show a linear behavior. Therefore, it has been considered that diamond thin films could be used as high doses dosimeters.     

Genetic search for model parameters in fitting thermoluminescence curves

Thermoluminescence (TL) processes in a crystal have been simulated by means of a genetic algorithm using models with a single trap and a system of competitive traps. The proposed approach ensures satisfactory approximation of the experimental TL curves for various relationships between the characteristics of the trapping and recombination centers.     

Efficiency-corrected dose verification with thermoluminescence dosemeters in heavy-ion beams

One of the most essential difficulties in heavy-ion dosimetry by means of thermoluminescence dosemeters (TLDs)--often seen as a serious disadvantage of TLD utilisation--regards the changing TL-efficiency with increasing linear energy transfer (LET) of the particle. This behaviour leads to a falsification of absorbed dose that can be significant for many applications, e.g. in space or radiotherapeutic dosimetry. The high-temperature TL emission of LiF:Mg,Ti TL detectors can be exploited to obtain information about the LET of the heavy-ion radiation field under study. The high-temperature ratio (HTR) is used as a parameter to determine average LET. To correct the absorbed dose according to the TL-efficiency, the detailed dependence of HTR- and TL-efficiency on LET was recorded. These investigations were accomplished at the Heavy Ion Medical Accelerator (HIMAC) in Chiba, Japan, with a variety of high-energy ion beams (helium, carbon, neon, silicon and iron) ranging in LET from 2.2 to 393 keV microm(-1). The obtained relationships HTR vs. LET and TL-efficiency vs. LET were combined into a TL efficieny vs. HTR relationship. This enables correction of the absorbed dose (HTR-B method). The methodology is demonstrated by means of TLD 700 ((7)LiF:Mg,Ti) measurements in carbon beams of 290 and 400 MeV n(-1) available from HIMAC.     

A thermoluminescence dosimetry system for personal monitoring in Ireland

In 1993 the decision was taken to replace film badges with thermoluminescence dosemeters (TLDs) as the main form of dosemeter for both whole-body and extremity monitoring at the Dosimetry Service of the Radiological Protection Institute of Ireland (RPII) in Dublin. A review of commercially available automatic TLD systems was carried out to identify the system which best met the RPII's requirements. This paper describes the dosimetry system used, and, in addition, discusses the problems encountered and how these were addressed.     

Thermal precipitation of silver nanoparticles and thermoluminescence in tellurite glasses

Silver metal and/or oxide precipitation of nanoparticles in thermally treated Ag-doped tellurite glasses was studied by optical absorption (OA) and transmission electron microscopy (TEM). The Lorentzian adjusted silver nanoparticles plasma resonance OA band was compared to the Drude model approach. The silver nanoparticles size distribution on the surface rather than in the bulk was determined by TEM. A model for the metallic silver precipitation is proposed. The characterization of the formation of silver nanoparticles was carried out with differential thermal analysis (DTA) to determine the glass transition temperature (Tg) and of crystallization (Tc). Previously γ-irradiated samples exhibited thermoluminescence (TL) peaks and the defect centers TeOHC, NBOHC and TeEC were identified by electron paramagnetic resonance (EPR), but no Ag⁰ signal was detected. The silver nanoparticles are known to introduce desired third-order optical nonlinearities in the composites, at wavelengths close to the characteristic surface-plasmon resonance of the metal precipitates. An increase of the glass density and refractive index with increasing AgNO₃ content was observed.     

Stability of defects and thermoluminescence in some doped KCl crystals

Thermal stability of interstitials in room-temperature γ-irradiated KCl:Li and KCl:Na crystals has been investigated by optical absorption and thermoluminescence (TL) methods. Results show that the activation energy increases with decreasing dopant-atomic size. The processes involved during TL appear to follow first-order kinetics and emission spectra are intrinsic but perturbed by impurities.     

Photo and thermoluminescence of Eu doped ZnO nanophosphors

The photoluminescence (PL) and thermoluminescence (TL) studies of un-doped and Eu doped zinc oxide (ZnO) nanophosphors are presented in this paper. The paper also includes characterization by XRD and SEM for structural and morphological studies of chemically synthesized ZnO nanoparticles by using zinc acetate and ammonia solution. Thiourea was used for capping. The hexagonal structure of the undoped and Eu doped ZnO nanoparticles was observed. The XRD of rare earth doped sample showed an extra peak attributed to Europium oxide. The sizes of samples were ranging from 55 to 80 nm. SEM image of undoped ZnO nanoparticle showed flower like structure, whereas, no such shape was found for Eu doped ZnO nanoparticles. The excitation wavelength dependent PL and colour chromaticity diagram for both undoped and Eu doped ZnO was studied. Five samples of Eu doped ZnO, with 0.5%, 1%, 2.5%, 3% and 3.5% molar concentration of Eu were prepared. The variations in PL and TL with different concentrations of Eu were also studied. The Maximam PL and TL intensity was recorded for the samples containing 3% of Eu. The increase in the TL intensity for both the samples was found with increasing γ dose (100–1500 Gy) without any saturation sign. The variations in TL intensity with changing heating rate (5–12 °C/s) were also studied. No change of TL glow peak position was seen for Eu doped sample. A linear increase of TL peak intensity with γ dose suggests that, this phosphor could be used for dosimetry.

     

In vivo thermoluminescence dosimetry for total body irradiation

An improvement in the clinical results obtained using total body irradiation (TBI) with photon beams requires precise TBI treatment planning, reproducible irradiation, precise in vivo dosimetry, accurate documentation and careful evaluation. In vivo dosimetry using LiF Harshaw TLD-100 chips was used during the TBI treatments performed in our department. The results of in vivo thermoluminescence dosimetry (TLD) show that using TLD measurements and interactive adjustment of some treatment parameters based on these measurements, like monitor unit calculations, lung shielding thickness and patient positioning, it is possible to achieve high precision in absorbed dose delivery (less than 0.5%) as well as in homogeneity of irradiation (less than 6%).     

Red thermoluminescence of quartz and its application in dating archaeometallurgical slag

Slag is often the only relic of early pyrometallurgical processes. In archaeological research information about the age of slag deposits is needed and diflicult to obtain with traditional methods. Thermoluminescence has a great potential in this field, because the smelting process leads to a well defined resetting of the 'Luminescence Clock'. Metallurgical slag generally consists of many components, artificial secondary minerals, e.g. fayalite and glass phases usually being the dominant parts. Primary minerals, called relics, are also components or slag. Such a complex composition leads to large difficulties in palaeodose determation if the bulk slag is used. To overcome these problems defined phases of the slag have been separated. Palaeodose determination has been carried out on separated quartz fractions by 'Single Aliquot Regeneration' procedures using the 620 nm emission. The dose rate was determined by high-resolution gamma spectrometry. Alpha autoradiography was carried out to get information about the distribution of radionuclides. The study includes first dating results.