GlowFit—a new tool for thermoluminescence glow-curve deconvolution

Comparison of linear energy transfer measurement for therapeutic carbon beam using CR-39 and TLD

The measurement of linear energy transfer (LET) is crucial for the evaluation of the radiation effect in heavy ion therapy. As two detectors which are convenient to implant into the phantom, the performance of CR-39 and thermoluminescence detector (TLD) for LET measurement was compared by experiment and simulation in this study. The results confirmed the applicability of both detectors for LET measurements, but also revealed that the CR-39 detector would lead to potential overestimation of dose-averaged LET compared with the simulation by PHITS, while the TLD would have a large uncertainty measuring ions with LET larger than 20 keVμm-1. The results of this study were expected to improve the detection method of LET for therapeutic carbon beam and would finally be benefit to the quality assurance of heavy ion radiotherapy.

Synthesis, characterization and thermoluminescence of MgO:Li,Tb,Sm phosphor for high dose gamma dosimetry applications

A detailed TL investigation on MgO:Li,Tb,Sm phosphor has been carried out by studying several TL characteristics - TL glow curve structure, dose response, linearity dose behaviour, fading and reproducibility. TL glow curve structure of the phosphor reveals the presence of two TL glow peaks. The main TL glow peak of high intensity is observed at high temperature side i.e. at 162 °C and another peak of low intensity is observed at 316 °C. Further, the effect of dose on TL response of the phosphor has been studied and a new behaviour is noticed. With increasing doses, the position of main TL glow peak is similar while the second TL glow peak vanishes at higher doses. A linear TL response is observed from 10 Gy-700 Gy and becomes sublinear above 700 Gy. Low TL fading characteristics and good reproducibility have also been observed. Encouraging results suggest the applicability of doped MgO phosphor for the detection of gamma rays.

Photoluminescence and thermoluminescence dosimetry properties of Ag/Y co-doped ZnO nanophosphor for radiation measurements

This work explores the thermoluminescence (TL) and photoluminescence (PL) properties of Ag/Y co-doped zinc oxide (ZnO) nanophosphor. The proposed dosimeter was prepared by the coprecipitation method and sintered at temperatures from 400°C to 1000°C in an air atmosphere. Raman spectroscopy was studied to investigate the structural features of this composition. The new proposed dosimeter revealed two peaks at 150°C and 175°C with a small shoulder at high temperature (225°C). The PL spectrum showed strong green emissions between 500 to 550 nm. The Raman spectrum showed many bands related to the interaction between ZnO, silver (Ag), and yttrium oxide (Y2 O3 ). The rising sintering temperature enhanced the TL glow curve intensity. The Ag/Y co-doped ZnO nanophosphor showed an excellent linearity index within a dose from 1 to 4 Gy. The minimum detectable dose (MDD) of the Ag/Y co-doped ZnO nanopowder (pellets) equaled 0.518 mGy. The main TL properties were achieved in this work as follows: thermal fading (37% after 45 days at 1 and 4 Gy), optical fading (53% after 1 h and 68% after 6 h by exposure to sunlight), effective atomic number (27.6), and energy response (flat behavior from 0.1 to 1.3 MeV). Finally, the proposed material shows promising results nominated to be used for radiation measurements.

Development of the Composite Thermoluminescent Detectors Based on the Single Crystalline Films and Crystals of Perovskite Compounds

This work is dedicated to the development of new types of composite thermoluminescent detectors based on the single crystalline films of Ce-doped GdAlO₃ perovskite and Mn-doped YAlO₃ and (Lu_0.8Y_0.2)AlO₃:Mn perovskites as well as Ce and Pr-doped YAlO₃ single crystal substrates. These detectors were obtained using the Liquid Phase Epitaxy growth method from the melt solution based on the PbO-B₂O₃ fluxes. Such composite detectors can by applied for the simultaneous registration of different components of mixed ionization fluxes using the differences between the thermoluminescent glow curves, recorded from the film and crystal parts of epitaxial structures. For creation of the new composite detectors, we considered using, for the film and crystal components of epitaxial structures (i) the different perovskite matrixes doped with the same type of activator or (ii) the same perovskite host with various types of activators. The thermoluminescent properties of the different types of epitaxial structures based on the abovementioned films and crystal substrates were examined in the conditions of β-particles and X-ray excitation with aim of determination of the optimal combination of perovskites for composite detectors. It was shown that, among the structures with all the studied compositions, the best properties for the simultaneous thermoluminescent detection of α- and X-rays were the GdAlO₃:Ce film/YAlO₃:Ce crystal epitaxial structure.

RECENT DEVELOPMENTS IN COMPUTERISED ANALYSIS OF THERMOLUMINESCENCE GLOW CURVES: SOFTWARE CODES, MECHANISMS AND DOSIMETRIC APPLICATIONS

The computerised deconvolution of thermoluminescence glow curves into component glow peaks is discussed in detail with special emphasis on advances of the subject post 2013. A plethora of computer codes have been developed using models based on first-order kinetics, second-orders kinetics, interactive traps and continuous distributions of activation energies. The glow curves of several materials are displayed and discussed along with new and improved dosimetric applications:precision effects of heating rate, heavy charged particles, mixed field α/ϒ dosimetry, fading and dose-response linearity. Finally recommendations are made for future efforts.

Dosimetric characteristics of Gd-doped silica glass subjected to neutron and gamma irradiations

The dosimetric characteristics of newly developed gadolinium (Gd) glass dosimeter produced via sol-gel method are reported. Irradiation were made using a 750 kW neutron flux thermal power and 1.25 MeV ⁶⁰Co gamma rays with entrance doses from 2 to 10 Gy. Investigation has been done on various Gd dopant concentrations, ranging from 1 to 10 mol%. The Gd-doped silica glass have been characterised for thermoluminescence (TL) dose response, sensitivity, linearity index, glow curve and kinetic parameter analysis. For particular dopant concentration obtained in 6 mol% Gd, the least squares fit shows the change in TL yield, correlation coefficient (r²) of better than 0.980 (at 95% confidence level), with neutron and gamma exposure to be 8 and 4 times greater than that of 1 mol% Gd, respectively. Broad peaks in the absence of any sharp peak observed in the glow curve confirms the amorphous nature of the prepared glass. A glow curve of Gd-doped SiO₂ sample is observed with a single prominent peak (T_m) within 200-250 °C (peak shifting appears with respect to the increment of dopant concentration) and 350 °C (for all respective Gd dopants) for neutron and gamma irradiations, respectively. Deconvolution shows the glow curves of the Gd-doped SiO₂ glass to be formed of seven and five overlapping peaks, with figures of merit below 2% (FOM) of between 1.38-1.79 and 1.30-1.97 for the particular neutron and gamma irradiations, respectively. Through use of Glowfit deconvolution software, the key trapping parameters of activation energy, E and frequency factor, s^-1 were calculated for the Gd-doped SiO₂ glass. The mechanism of TL yield with the gradual increase in Gd concentrations and doses is explained upon the incorporation of Gd and radiation damage that change the structure of the electron traps in the glass matrix. These early results indicate that selectively screened Gd-SiO₂ glass can be developed into a promising TL system towards dosimetric applications.

Impact of the Synthesis Method on the Conventional and Persistent Luminescence in Gd3-xCexGa3Al2O12

The series of Gd_3-xCe_xGa₃Al₂O₁₂ nanopowders doped with different concentrations of Ce³⁺ ions were prepared by Pechini (sol-gel) and combustion methods. The structure and morphology of the powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. It was found that the synthesis method has a great impact on the morphology and, consequently, spectroscopic properties of the powders. Optical properties of the powders were examined using excitation, emission, and luminescence kinetic measurements. For all powders, persistent luminescence and emission decay processes were studied. The most intense luminescence was observed for the powder with 0.5 mol % of Ce³⁺ synthesized using the combustion method and 1 mol % in the case of the sol-gel sample. The longest and brightest persistent luminescence was observed for the powders doped with 0.1 mol % (combustion) and 0.2 mol % of Ce³⁺ ions (sol-gel). The thermoluminescence measurements were done for the powders prepared using different methods to understand the impact of the synthesis conditions on the number and depths of the traps involved in persistent luminescence. On the basis of spectroscopic measurements, the mechanism of persistent luminescence was constructed and discussed.

Computerized glow curve deconvolution (CGCD): A comparison using asymptotic vs rational approximation in thermoluminescence kinetic models

In this study an open-source tool GCD Analyzer, based on Microsoft® Excel, for Computerized Glow Curve Deconvolution analysis (CGCD) of thermoluminescence (TL) glow peak has been developed using a more accurate rational approximation. It is capable of deconvolution of glow curves having discrete or continuous trap distribution and can be used for routine as well as emergency radiation dosimetric analysis. This tool has a unique feature of TL glow curve analysis by combining discrete and continuous energy distributions for crystalline, amorphous, and mixed materials. To obtain best values of trap parameters like activation energy (E), frequency factor (s), order of kinetics (b), GCD Analyzer has the capability of analyzing glow curve using selectable individual peak of various physical kinetic models i.e. FOK, SOK, GOK, MOK, and Continuous Traps Distribution (CTD) with subtraction of optional background signal. The residual graph gives a clear visual understanding of the Figure of Merit (F.O.M). A comparison of asymptotic and rational approximation to the built-in second order exponential integral function E₂(E/KT) for E/KT < 600 is also presented. The results are verified by deconvolution of test synthetic glow curves with F.O.M up to 0.0005%, experimental glow curve for CTD with F.O.M of 0.9781%, and in the case of GLOWCANIN project glow curves, the F.O.M is comparable to the least values achieved by inter-comparison participants.

Out-of-field mean photon energy and dose from 6 MV and 6 MV FFF beams measured with TLD-300 and TLD-100 dosimeters

PURPOSE

To measure the out-of-field mean photon energy and dose imparted by the secondary radiation field generated by 6 MV and 6 MV FFF beams using TLD-300 and TLD-100 dosimeters and to use the technique to quantify the contributions from the different sources that generate out-of-field radiation.

METHODS

The mean photon energy and the dose were measured using the TLD-300 glow curve properties and the TLD-100 response, respectively. The TLD-300 glow curve shape was energy-calibrated with gamma rays from ^99m Tc, ¹⁸ F, ¹³⁷ Cs, and ⁶⁰ Co sources, and its energy dependence was quantified by a parameter obtained from the curve deconvolution. The TLD-100 signal was calibrated in absorbed dose-to-water inside the primary field. Dosimeters were placed on the linac head, and on the surface and at 4.5 cm depth in PMMA at 1-15 cm lateral distances from a 10 × 10 cm² field edge at the isocenter plane. Three configurations of dosimeters around the linac were defined to identify and quantify the contributions from the different sources of out-of-field radiation.

RESULTS

Typical energies of head leakage were about 500 keV for both beams. The mean energy of collimator-scattered radiation was equal to or larger than 1250 keV and, for phantom-scattered radiation, mean photon energies were 400 keV for the 6 MV and 300 keV for the 6 MV FFF beam. Relative uncertainties to determine mean photon energy were better than 15% for energies below 700 keV, and 40% above 1000 keV. The technique lost its sensitivity to the incident photon energy above 1250 keV. On the phantom surface and at 1-15 cm from the field edge, 80%-90% of out-of-field dose came from scattering in the secondary collimator. At 4.5 cm deep in the phantom and 1-5 cm from the field edge, 50%-60% of the out-of-field dose originated in the phantom. At the points of measurement, the head leakage imparted less than 0.1% of the dose at the isocenter. The 6 MV FFF beam imparted 8-36% less out-of-field dose than the 6 MV beam. These energy results are consistent with general Monte Carlo simulation predictions and show excellent agreement with simulations for a similar linac. The measured out-of-field doses showed good agreement with independent evaluations.

CONCLUSIONS

The out-of-field mean photon energy and dose imparted by the secondary radiation field were quantified by the applied TLD-300/TLD-100 method. The main sources of out-of-field dose were identified and quantified using three configurations of dosimeters around the linac. This technique could be of value to validate Monte Carlo simulations where the linac head design, configuration, or material composition are unavailable.

Preliminary Thermoluminescent Dosimeter Glow Curve Analysis with Automated Glow Peak Identification for LiF:Mg,Ti

ABSTRACT

When appropriately analyzed, thermoluminescent dosimeter glow curve analysis allows for improved quantification of thermoluminescent material behavior while flagging abnormalities. The mathematical separation of a glow curve into contributions from energetically unique trap states, or glow curve analysis, may be used to remove undesired effects of signal fading for complex materials. A generalized glow curve analysis software for the separation of glow curves is presented in this paper. Written in C++, the software uses the first-order kinetics model with automatic peak identification. The automatic identification of peaks is achieved through a unique peak-finding algorithm. The program was performance tested using experimental glow curve data from LiF:Mg,Ti, and comparative results are presented.

Stimulated luminescence; Analysis of complex signals and fitting of dose response curves using analytical expressions based on the Lambert W function implemented in a commercial spreadsheet

Thermoluminescence (TL) and optically stimulated luminescence (CW-OSL, LM-OSL) are widely used by the scientific community in different applications. In order for the information of a glow or decay curve to be used correctly, the deconvolution of the corresponding curve is essential. Nowadays, there are plethora of deconvolution methods with none of them being dominant and universal. Recently, researchers created some new analytical equations for the TL, CW-OSL and the LM-OSL phenomena, based on the Lambert W function, with the use of a single master equation, as well as some new dose response curves based on a) the simple One Trap One Recombination (OTOR) model and b) the more complex Two Traps One Recombination (TTOR) model. The main aim of the study is to recreate these five expressions in different Excel spreadsheets, for a more practical use. The first step is the creation of a computational code of the Lambert W function in VBA at Excel. After that aim is achieved, five spreadsheets were created, namely the TL deconvolution, the CW-OSL deconvolution, the LM-OSL deconvolution, the OTOR model Dose response and the TTOR Dose response. In order to run some tests using these spreadsheets, four different sets of experimental data originated from different sources were used each time, with the calculated values being compared to the literature. In the end, the present study provides some notes and discussion about the applications of the newly created deconvolution spreadsheets.

Design of the persistent luminescence colour of a novel Gd3-xTbxGa3Al2O12 phosphor: synthesis methods, spectroscopic properties and mechanism

The aim of this work was to check the influence of Tb³⁺ ion concentration and synthesis method on the persistent luminescence properties. A series of Gd_3-xTb_xGa₃Al₂O₁₂ nanopowders were obtained by using two different synthesis methods. The crystal structure refinement was performed to check the impact of the preparation method and doping level on the crystallization process. This revealed the influence of doping level on conventional and persistent luminescence color, intensity and decay time. It was demonstrated that it is possible to tune the persistent luminescence color by changing the Tb³⁺ doping level. The spectroscopic measurements show that persistent luminescence appears only under UV excitation, suggesting that the 5d levels of Tb³⁺ play an active role in this process. Thermoluminescence measurements indicate that the depth and number of electron traps in the samples are associated with the synthesis method and dopant concentration. Based on the results, the possible mechanism of energy transfer between the traps and luminescence centers is proposed and discussed.

Low-cost commercial borosilicate glass slides for passive radiation dosimetry

For x- and gamma- irradiations delivering entrance doses from 2- up to 1000 Gy to commercial 1.0 mm thick borosilicate glass microscope slides, study has been made of their thermoluminescence yield. With an effective atomic number of 10.6 (approximating bone equivalence), photon energy dependency is apparent in the low x-ray energy range, with interplay between the photoelectric effect and attenuation. As an example, over the examined dose range, at 120 kVp the photon sensitivity has been found to be some 5× that of ⁶⁰Co gamma irradiations, also with repeatability to within ~1%. The glow-curves, taking the form of a single prominent broad peak, have been deconvolved yielding at best fit a total of five peaks, the associated activation energies and frequency factors also being obtained. The results indicate borosilicate glass slides to offer promising performance as a low-cost passive radiation dosimeter, with utility for both radiotherapy and industrial applications.

Thermoluminescence glow-curve deconvolution using analytical expressions: A unified presentation

This study provides a unified presentation of thermoluminescence (TL) glow-curve deconvolution within the framework of the open source R package "tgcd", according to various analytical expressions that describe first-, second-, general-, and mixed-order kinetics as well as the recently developed semi-analytical expressions that derive from the one trap-one recombination center (OTOR) model that utilizes the Lambert W function or the Wright Omega function. We provide a comprehensive, flexible, convenient, and openly accessible program to analyze TL glow curves according to different models and expressions. The consistency of kinetic parameters determined using different model expressions was assessed using measured TL glow curve of CaF2:Dy. The performance of the computerized glow curve deconvolution (CGCD) method was also tested using simulated glow curves. Results revealed the benefits of comparing kinetic parameters determined from different model expressions and those obtained using experimental TL evaluation methods to assess the reliability of deconvolution results. The accuracy of the CGCD method is dependent upon both the model expressions used and the intrinsic trapping parameters of the TL material.

Correlation between thermoluminescence and optically stimulated luminescence responses of natural alexandrite

Luminescent properties of alexandrite crystals (BeAl₂O₄:Cr³⁺) are studied. Partial readouts of thermoluminescence (TL) and optically stimulated luminescence (OSL) signals were obtained to infer the relations of OSL and TL trapping centers. Four TL peaks were studied; their intensities decrease at different rates by illumination with blue OSL light. The OSL curve shows two-time components (exponential decay constants 3.15 and 28.4 s). The short time component is preferentially diminished when the sample is heated to temperatures from 363 to 513 K. About 50% of the whole TL intensity remains after a complete 300s OSL readout.

Natural dead sea salt and retrospective dosimetry

Accidents resulting in widespread dispersal of radioactive materials have given rise to a need for materials that are convenient in allowing individual dose assessment. The present study examines natural Dead Sea salt adopted as a model thermoluminescence dosimetry system. Samples were prepared in two different forms, loose-raw and loose-ground, subsequently exposed to ⁶⁰Co gamma-rays, delivering doses in the range 2-10 Gy. Key thermoluminescence (TL) properties were examined, including glow curves, dose response, sensitivity, reproducibility and fading. Glow curves shapes were found to be independent of given dose, prominent TL peaks for the raw and ground samples appearing in the temperature ranges 361-385 ºC and 366-401 ºC, respectively. The deconvolution of glow curves has been undertaken using GlowFit, resulting in ten overlapping first-order kinetic glow peaks. For both sample forms, the integrated TL yield displays linearity of response with dose, the loose-raw salt showing some 2.5 × the sensitivity of the ground salt. The samples showed similar degrees of fading, with respective residual signals 28 days post-irradiation of 66% and 62% for the ground and raw forms respectively; conversely, confronted by light-induced fading the respective signal losses were 62% and 80%. The effective atomic number of the Dead Sea salt of 16.3 is comparable to that of TLD-200 (Z_eff 16.3), suitable as an environmental radiation monitor in accident situations but requiring careful calibration in the reconstruction of soft tissue dose (soft tissue Z_eff 7.2). Sample luminescence studies were carried out via Raman and Photoluminescence spectroscopy as well as X-ray diffraction, ionizing radiation dependent variation in lattice structure being found to influence TL response.

Determination of Thermoluminescence Kinetic Parameters of La2O3 Doped with Dy3+ and Eu3

Thermoluminescence (TL) properties of La₂O₃: Dy³⁺, Li⁺, and La₂O₃: Eu³⁺, Li⁺, exposed to 5.12 Gy of beta radiation, and recorded at different heating rates 0.5, 1, 2, 3, 4, and 5 °C s⁻¹ (from Molefe et al., paper 2019), were analyzed and the trap parameters were determined in this study. These parameters include the order of kinetics b, the activation energy E (eV), the frequency factor S (s⁻¹), or the pre-exponential factor S″ (s⁻¹), and the initial concentration of trapped electrons n_o (cm⁻³). A new non-linear curve fitting technique, based on the general order kinetic equation and the outcomes of Hoogenstraaten’s Method, was established and applied on the TL glow peaks of La₂O₃: Dy³⁺, Li⁺. The fitting technique was evaluated by calculating the R-square and figure of merit (FOM) values. The results revealed that the FOM values are <1%, and the R-square values are >0.997, which demonstrates an excellent convergence between experimental and fitted curves. A modified technique based on the three-points analysis method was exploited to deconvolute complex TL glow curves of La₂O₃: Eu³⁺, Li⁺, and in turn, to determine the trap parameters the method disclosed that each TL glow curve consists of four peaks. The trap parameters of the individual peaks were numerically determined. The fading, as a function of storage temperature and time, from the TL signals of the investigated materials was predicted and discussed based on the calculated trap parameters. The results support the value of the materials for employment in radiation dosimeter applications with a low fading fraction.

TLDECOXCEL: A DYNAMIC EXCEL SPREADSHEET FOR THE COMPUTERISED CURVE DECONVOLUTION OF TL GLOW CURVES INTO DISCRETE-ENERGY AND/OR CONTINUOUS-ENERGY-DISTRIBUTION PEAKS

The present work presents a new user-friendly and dynamic tool, TLDecoxcel, for the computerised curve deconvolution analysis (CCDA) of simple or complex TL glow peaks using Microsoft® Excel. TLDecoxcel can be applied for the fitting of glow curves consisting of discrete-energy peaks (general or mixed order) or continuous-energy-distribution peaks or combination of the above using widely accepted analytical expressions, with minimal user intervention.

Thermoluminescence glow curve deconvolution for discrete and continuous trap distributions

Deconvolution analysis of the thermoluminiscent (TL) glow curves proved to be a good complementary method to characterize the individual glow peaks by fitting their kinetic parameters. In this work, new software has been developed for the automatic deconvolution of TL glow curves, assuming either discrete or continuous distribution of trapping centres. The guess estimation of the kinetic parameters is done automatically and can be manually modified, thus allowing the use of the software for routine, processing a large number of measurements, as well as for research purposes. The equations, the methods and the results of the first test are described in detail. The software has been developed by integrating Fortran code and Visual Studio tools to create a graphic easy-to-use environment and permits to obtain the fitted values for the parameters according to the considered model.

Analysis of the BeO thermoluminescent glow curve by the deconvolution method

Results of studying the behavior of the thermoluminescent glow curve of beryllium oxide (BeO) obtained in a wide range of absorbed doses are presented. The kinetic parameters and the TL response as a function of dose were determined using two deconvolution methods: Glow-Fit (Puchalska and Bilski 2006) and "tgcd" in "R" (Peng et al., 2016). Both methods showed that the glow curve of BeO obtained at a heating rate of 5 Ks^-1 can be resolved in two peaks at temperatures of approximately 477 and 586 K respectively, with an activation energy of 1.1 eV for both peaks. The Glow-Fit method assumes first-order kinetics; while the "tgcd" in "R" method allows to determine the order of kinetics, finding that both peaks follow a kinetic of first order. Regarding the TL response as a function of dose, it was found that the first peak exhibits a quadratic dependence while the second peak exhibits a linear behavior with respect to the dose throughout the dose range studied, thus showing great advantages for its application as a TL dosimeter.

AN IMPROVED METHOD FOR THE COMPUTERISED ANALYSIS OF GR-200A LiF:Mg,Cu,P TL SIGNALS

The profile of the residual signals of LiF:Mg,Cu,P within the region of dosimetric interest was approximated by a cubic curve. The conventional analysis, the GCA developed in CIEMAT and the GCA developed in this laboratory were compared. For GCA developed in this laboratory, the 5 μGy test dose could be well measured even after measurement at 10 mGy and obviously at lower doses. The 20 μGy test dose could be well measured even after measurement at 50 mGy. The residual signals caused by previous irradiations in the case of using only reader anneal can be more effectively eliminated by GCA developed in this laboratory than GCA developed in CIEMAT. The program developed in this laboratory, effectively estimating the contribution of the residual signals caused by previous irradiations, permits work to be done using only reader anneal in a dose range of more than three orders of magnitude.

Dosimetry in a mammography phantom using TLD-300 dosimeters

PURPOSE

The purpose of this study was to evaluate the photon field effective energy (Eeff ) distribution and percentage depth-dose (PDD) within a mammography phantom by the analysis of the CaF2 :Tm (TLD-300) thermoluminescent (TL) glow curve. The experimental procedure involves the use of TLD-300 to determine with single dosimeter exposures both the relative dose and the beam quality.

METHODS

TLD-300 chips were exposed to x rays from a GE Senographe 2000D mammography unit at the surface and different depths within a BR12 phantom. X-ray beams were generated with Mo/Mo, Mo/Rh, and Rh/Rh anode/filter combinations and voltages between 25 and 34 kV. Glow curves were deconvoluted into component peaks and the high- to low-temperature ratio (HLTR) was evaluated. The photon field Eeff was obtained from the HLTR values using a calibration curve determined previously. PDD was established from the peak 5 TL signal (TLSP5 ) at depths between 0.0 and 3.5 cm inside the phantom. Taking into account the differences in density and composition between CaF2 :Tm and breast tissue, an energy-dependent correction factor (β(E)) was applied to TLSP5 . Measurements were compared with radiation transport Monte Carlo (MC) simulations performed with PENELOPE-2008.

RESULTS

A typical 5% change in the HLTR from the phantom top surface to 3.5 cm depth was measured, which corresponds to a 2.2 keV increase in photon field Eeff . Values of the β(E) correction factor were 0.33 and 0.13 for Eeff equal to 15.1 and 22.5 keV, respectively. This strong energy dependence of β(E) is mostly due to the differences in fluence attenuation between CaF2 and breast tissue. According to PDD measurements, dose decreased to half the surface value at depths between 0.7 and 1.0 cm for Mo/Mo/25 and Rh/Rh/34 beams, respectively. Values of PDD, less than 10% at 3.5 cm depth, would have been overestimated by about 3.5% (a large relative error) if an energy-independent correction factor had been assumed. Mean differences between experiments and MC simulations were 0.8 keV and 1.2% in the determination of Eeff and PDD, respectively.

CONCLUSION

The TLD-300 glow curve was used to accurately measure the photon field Eeff and PDD within a mammographic phantom. This work has demonstrated that Eeff and dose can be established simultaneously by using solely TLD-300.

Thermoluminescence properties of annealed natural quartz after beta irradiation

Here we investigated the effects of annealing, heating rate and fading (after annealing at 800 °C) on the thermoluminescence (TL) glow curves of natural quartz (NQ). All of the samples were annealed at different temperatures between 100 °C and 800 °C and then irradiated with a beta dose of about 34 Gray (Gy), in order to determine the effects of annealing treatments on TL peaks of natural quartz. TL glow curves of the samples were recorded. It was observed that the intensities of TL peaks were strongly sensitive to annealing temperatures at 800 °C. The heating rate and fading effect of TL peaks of natural quartz were examined for the annealed samples at 800 °C for 30 min. It was observed that the intensities of the TL peaks were differently affected from heating rate and fading. Additionally, TL kinetic parameters (activation energy, frequency factor and order of kinetics) of all peaks were determined for annealed samples using a computerized glow curve deconvolution (CGCD) method and Mathematica software. Copyright © 2016 John Wiley & Sons, Ltd.

Synthesis and characterization of Nd2O3 nanoparticles in a radiofrequency thermal plasma reactor

The synthesis of nanocrystalline Nd2O3 through an inductively coupled radiofrequency thermal plasma route is reported. Unlike in conventional synthesis processes, plasma-synthesized nanoparticles are directly obtained in a stable hexagonal crystal structure with a faceted morphology. The synthesized nanoparticles are highly uniform with an average size around 20 nm. The nanoparticles are characterized in terms of phase formation, crystallinity, morphology, size distribution, nature of chemical bonds and post-synthesis environmental effects using standard characterization techniques. X-ray diffraction, transmission electron microscopy, and scanning electron microscopy are used for structural and morphological studies. The thermo-gravimetric technique, using a differential scanning calorimeter, is used to investigate the purity of phase. Fourier transform infrared spectroscopy is used to investigate the nature of existing bonds. The optical response of the nanoparticles is investigated through the electronic transition of Nd(3+) ions in its crystalline structure via UV-visible spectroscopy. The presence of defect states and corresponding activation energies in the nanocrystalline Nd2O3 compared to those of the precursors are studied using thermoluminescence.