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[en] 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 MicrosoftR 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. (authors)
[en] Coefficient (ECC) of TLD-100 thermoluminescent cards, to ensure that all cards obtain factors with the least possible variation. This will ensure uniformity in the sensitivity of the cards when they are used for individual radiological surveillance . I know used a Harshaw Model 6600 Plus thermoluminescent card reader, TLD-100 cards (LiF: Mg, Ti), a radioactive source of Sr-90 incorporated in the reader and a standard source of Cs-137. The ECC of a random sample from a batch of new cards automatically, where TLD cards they were exposed to 200 gU (generic units) with the Sr-90 source . Then the ECC was determined from the same TLD cards but with an irradiation of 5 mSv using a standard source of Cs-137 from the Secondary Laboratory of Dosimetric Calibrations . The calibration dosimeters used were the same in both cases, in the first case everything was done in generic units and in the second in dosimetric units. When comparing the results obtained, a variation in the response of the thermoluminescent cards evaluated. However, most cards they presented a variation within the 30% allowable. Oberhofer M .; Scharmann A., Applied Thermoluminescence Dosimetry, Ispra, Italy, November 1979. Thermo Fisher Scientific; Model 6600 Plus Automated TLD card reader Operator's Manual, November 2010. CEI / IEC - Thermoluminescence Dosimetry Systems for Personal and Environmental Monitoring - IEC 61066, Second Edition 2006.
[en] Response of Al2O3:C-based nanoDot optically stimulated luminescence (OSL) dosimeter was studied for the dosimetry of 6, 9, 12, 16, and 20 MeV therapeutic electron beams. With reference to ionization chamber, no change in the response was observed with the change in the energy of electron beams for the field size from 6 cm × 6 cm to 25 cm × 25 cm, dose rates from 100 MU/min to 600 MU/min, and the linearity in the response up to 300 cGy. The fading of the transient signal was higher for 20 MeV electron beam than that of 6 MeV electron beam by about 5% as compared to value at 20 min after irradiation. The depletion of OSL signal per readout in 200 successive readouts was also found to change with dose and energy of electron beam from 6 MeV (9% and 12% per readout at 2 and 10 Gy, respectively) to 20 MeV (9% and 16% at 2 and 10 Gy, respectively). The OSL sensitivity changed in the range from 2% to 6% with accumulated doses from 2 to 8 Gy and with electron energy from 6 to 20 MeV, but the sensitivity could be reset using an optical annealing treatment. Although negligible fading for postirradiation storage from 20 min to several months, acceptable precision and linearity in the desired range, and high reproducibility makes nanoDot dosimeters very attractive for the dosimetry of therapeutic electron beams, a note should be made for changes in sensitivity at doses beyond 2 Gy and electron beams energy dependence in reuse, short-term fading, and signal depletion on repeated readout. (author)
[en] The effect of previous irradiation on the sensitivity of the glow peaks of LiF:Mg,Ti (TLD-100) is investigated up to levels of dose of 400 Gy in both slow-cooled and naturally cooled materials following the 400 deg. C/1 hour pre-irradiation anneal. It is demonstrated that the naturally cooled samples can be re-used up to accumulated levels of dose of 50 Gy without recalibration. At 400 Gy a significant decrease in sensitivity of approximately 25% is observed for all the glow peaks (excluding peak 3). In slow-cooled materials even 100 Gy does not alter the sensitivity of the material. (authors)
[en] The OSL and the TL techniques are used in several fields of radiation dosimetry. The dosimeters are affected by a signal loss in the time between the irradiation and readout (fading). This undesirable characteristic can cause an underestimation of the irradiation dose. The fading estimation of SOL-GEL α-Al2O3 with several different concentrations of impurities is reported. The thermal fading and the light-induced fading of the SOL-GEL α-Al2O3 detectors were estimated. Furthermore, the exponential equations used to interpolate the experimental results were presented. (author)
[en] Full text: Thermoluminescence properties (TL) of some ceramic materials as SiO2 and Al2O3 exposure to artificial irradiation are wide used for development a dosimeter device, where the dating of lifetime and TL intensity are important parameters that induce clarification of the radiological accident . In this work, building material like brick samples collected around Gama-DF, were prepared by sintering fine grain powders and characterized by X-ray diffraction technical were observed peaks characteristic of Quartz (SiO2) and Alumina (Al2O3). TL yield curves with influence of heating rate was relevant because with these results for temperature between 150 – 250ºC showed more stability and increasing in the dose measurements in radiological accident. Besides this, some parameters kinetic as activation energy (ET), frequency factor (s) and kinetic order (b) were calculated. It was possible to determine the lifetime of each TL curves found to be in the order of year. These studies using micrometric ceramic were important as reference, because we are currently synthesizing and studying nanoceramics based on nanoparticles of Alumina and Quartz with a large surface area in order to improve theses nanomaterials to evaluated the prospects of their use as dosimeters of short-range particles . References:  Trinkler, L.; Christensen, P.; Larsen, N. A. and Berzina, B. Thermoluminescence Properties of AIN Ceramics. Radiation Measurements, 29, 341-348 (1998)  Kortov, V. S.; Ermakov, A. E.; Zatsepin, A. F. and Nikiforov, S. N. Luminescence Properties of Nanostructured Alumina Ceramic. Radiation Measurements, 43, 341-344 (2008). (author)
[en] Highlights: • New software for thermoluminescence glow curve deconvolution has been developped. • Accurate algebraic equations for first order and general order kinetics have been obtained. • New equation for a continuous trap distribution has been obtained. • Both discrete and continuous trap equations, the considered parameters can be estimated from the glow curve analysis. • Results with simulated glow curve is presented and discussed. - Abstract: 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.
[en] In high energy accelerator facilities the neutron radiation should be continuously measured during operation to control the ambient dose. This requires a reliable neutron dosimeter in a wide energy range. In this work we present an optimization of a compact cylindrical passive neutron dosimeter based on thermoluminescence dosimetry (TLD) for the usage in wide energy neutron fields. In TLD devices, neutrons are detected via a 6Li(n, α)3H reaction whose cross section increases for low energy neutrons. To perform neutron fluence to equivalent ambient dose conversion an appropriate combination of a neutron moderator and absorber layouts should be used. The choice of materials and dimensions of different layers were tested with simulations using the FLUKA code. The final neutron dosimeter design improves the fluence-to-ambient dose conversion and provides almost angular independent equivalent dose reading. The dosimeter response covers almost 12 orders of magnitude of neutron energies which is rather sufficient for using it at high energy accelerators
[en] Background and purpose: Since 1969 the International Atomic Energy Agency (IAEA), together with the World Health Organization (WHO), has performed postal TLD audits to verify the calibration of radiotherapy beams in developing countries. Materials and methods: A number of changes have recently been implemented to improve the efficiency of the IAEA/WHO TLD programme. The IAEA has increased the number of participants and reduced significantly the total turn-around time to provide results to the hospitals within the shortest possible time following the TLD irradiations. The IAEA has established a regular follow-up programme for hospitals with results outside acceptance limits of ±5%. Results: The IAEA has, over 30 years, verified the calibration of more than 3300 clinical photon beams at approximately 1000 radiotherapy hospitals. Only 65% of those hospitals who receive TLDs for the first time have results within the acceptance limits, while more than 80% of the users that have benefited from a previous TLD audit are successful. The experience of the IAEA in TLD audits has been transferred to the national level. The IAEA offers a standardized TLD methodology, provides guidelines and gives technical back-up to the national TLD networks. Conclusion: The unsatisfactory status of the dosimetry for radiotherapy, as noted in the past, is gradually improving; however, the dosimetry practices in many hospitals in developing countries need to be revised in order to reach adequate conformity to hospitals that perform modern radiotherapy in Europe, USA and Australia.