Thermoluminescence Properties of Bioglass for Radiation Dosimetry

The thermoluminescence technique was employed to study bioglass matrices prepared using the traditional technique of glass making. The synthesized bioglass matrices were investigated using X-ray diffraction (XRD), and differential thermal analysis (DTA) has been studied. The highest thermoluminescent intensity was found for the bioglass matric of 26.91% CaO, 46.134% SiO2, 2.60% P2O5, 24.34%Na2O (mol%), with only one glow peak at 460 k. The TL response illustrations linearity in high gamma dose range from 25 to 1000 Gy. This new bioglass matric might become useful in high-dose fields for dosimetry.

Three-Point Area Method for Thermoluminescence Glow Curve Analysis and Its Application to the Glow Peak of K2SrP2O7:Pr

A method has been proposed to evaluate the kinetic parameters, viz. activation energy ($E$) and order of kinetics ($b$) from a single or isolated thermoluminescence (TL) glow peak. Along with the area under the entire curve, this method uses a set of three arbitrary data points and calculates the partial area under the curve from each point to the endpoint. In this way, the entire information associated with the curve is used and the method is named as ‘Three-Point Area’ (TPA) method. We have applied it successfully on a number of theoretically simulated TL curves generated in One Trap One Recombination centre (OTOR) model and General-Order Kinetics (GOK) model under quasi-equilibrium approximations with linear heating scheme. The activation energies are found in good agreement with input values for both the models. For OTOR model, temperature average of order of kinetics is estimated to compare with the present result. Systematic analysis is carried out for estimation of errors inherent in the method in the purview of GOK model. A closer look on the results reveals that any set of three points, preferably chosen from the rising side of the curve, can yield activation energy and order of kinetics. The validity of the method to extract $E$ and $b$ from experimental glow curves is exemplified by considering experimental TL data reported in literature. Finally, a complete study starting from the synthesis of a new phosphor $\mathrm{K_2SrP_2O_7:Pr} $ and analysis of the recorded TL data to estimate $E$ and $b$ employing the TPA method has been reported.

Thermo-luminescence Response of Carbon Nanotubes and Some Other Familiar TL Materials Using Medical LINAC

Strain and impurity defects in carbon nanotubes (CNTs) particularly their potentiality as a new TL material has been studied over the years. In this research, our main objective is to explore the suitability of using CNTs and its composites in the area of TL dosimeter. For this purpose, a study was carried out between the TL responses of the dosimeters TLD-100, TLD-7000 and NaI-LiF pellets. To carry out this research, equivalent irradiations were performed with these pellets using clinical linear accelerator (LINAC) under 6 MV X-ray photon beam. The dose range was from 0.5 to 5 Gy. During irradiation, the dose rate was kept constant at 300 MU/min. TLD reader was used to readout the samples in a flowing N2 atmosphere to reduce surface oxidation.During readout, pre-heat temperature was set initially at 50 °C, acquired temperature rate 10 °C/s and maximum annealed temperature was 300 °C. Response of TLD-100 under varying dose was typically linear for any doses but other dosimeters TLD-7000 showed supra-linearity beyond 2 Gy and NaI-LiF pellets showed sub-linearity response after 2 Gy. The TL glow peak of CNTs indicated that it was lying somewhere away from 300 °C.

Component resolved equivalent dose estimation using TL glow curves of travertine samples from Anatolia, Turkey

This study provides methodological aspects on the equivalent dose estimation for travertine samples, namely heated calcium carbonate, using the TL multiple-aliquot additive-dose approach. Large equivalent doses (EDs), within the range 750–1300 Gy, were calculated using the plateau method based on the NTL glow curve. Moreover, a component resolved TL glow-peak analysis was carried out, using the integrated intensity of the NTL glow peaks for the ED estimation after deconvolution based on the OTOR model. Three different TL peaks were used, termed P4, P5 and P6. The integrated intensity of TL glow peak P4 resulted in age overestimation (15–26%), compared to the age provided using the plateau method. This overestimation could be attributed to the fact that the temperature range of P4 does not coincide with the plateau region of each sample. Milder overestimation (8–14%) was noticed using the integrated intensity of TL glow peak P6, mostly due to the poor deconvolution resolution. Only the integrated intensity of TL glow peak P5 after deconvolution provides ED values compatible with those yielded using the plateau method, with good accuracy. The present study suggests not using the TL intensity (neither in terms of integrated intensity nor of peak height intensity) for ED estimation; instead it is highly recommended to use either the plateau method, or alternatively integrated intensity of TL peak P5 after deconvolution. Unfortunately, using the peak height of TL P5 is not recommended, due to overlapping with P6.

STUDY OF EFFECT OF CONSECUTIVE HEATING ON THERMOLUMINESCENCE GLOW CURVES OF MULTI-ELEMENT TL DOSEMETER IN HOT GAS-BASED READER SYSTEM

The objective of this paper is to study the effect of consecutive heating of TL elements of a thermoluminescence dosemeter (TLD) card in hot N2 gas-based TLD badge reader. The effect is studied by theoretical simulations of clamped heating profiles of the discs and resulting TL glow curves. The simulated temperature profile accounts for heat transfer to disc from hot gas as well as radiative and convective heat exchanges between the disc and the surrounding. The glow curves are simulated using 10 component glow peak model for CaSO4:Dy using the simulated temperature profile. The shape of the simulated glow curves and trend in total TL signal of the three discs were observed to match closely with the experimental observations when elevated surrounding temperature was considered for simulation. It is concluded that the readout (heating) of adjacent TLD disc affects the surrounding temperature leading to the changes in temperature profile of the next disc.

Đánh giá các giá trị năng lượng bẫy từ đường cong nhiệt huỳnh quang để phát hiện bột ớt chiếu xạ

This report presents the estimation of the activation energy (E) values from the thermoluminescence (TL) glow curves showed by the whole glow peak (WGP) method that allows us to distinguish between irradiated and non-irradiated chilli powder samples. The E values of non-irradiated samples maintain 0.65 eV whereas irradiated ones reach 0.84 eV or upper. Furthermore, the E values are obtained from the result of comparison between the chilli powder irradiated with different doses (2, 4, 6 and 8 kGy) stored for 30 days and other unknown chilli powder samples in Vietnam.

Study on Luminescence of KCl:Eu2+ Crystals after X-ray Irradiation at Room Temperature

Bleaching with the F-light at the excitation bandpass of 20 nm results in the phenomenon that F-centre peak and thermoluminescence (TL) glow peaks due to Fz- and F-centres identically decrease with the F-bleach time, whereas TL glow peak due to Fz-centre only remains almost constant irrespective of its time in the case of that at the excitation bandpass of 5 nm. Analysing the data on bleaching effects, absorption spectrum of X-ray irradiated KCl:Eu2+ crystal has a peak due to Fz-centre approximately within 20 nm of the wavelength 560 nm at F-centre peak. Electrons released from Fz-centres at 370 K and from F-centres at 450 K combine with Eu3+ ions, leading to the excited Eu2+ ions from which the luminescence at 420 nm is emitted.

A NEW THERMOLUMINESCENCE GENERAL ORDER GLOW CURVE FIT FUNCTION CONSIDERING THERMAL QUENCHING EFFECT

A new thermoluminescence (TL) general order glow curve fit function in terms of the intensity of peak maximum, Im and the peak temperature, Tm is presented in which thermal quenching (TQ) effect has been taken into account. Also, the conventional general order model and the new presented function were fitted to the glow peak 5 of LiF:Mg,Ti (TLD-100) and the kinetic parameters were obtained for different heating rates as the results of fitting procedure. It was found that increasing the heating rate, which makes the TQ more prominent, causes more divergence between the kinetic parameters extracted by applying two models. Considering that the TL intensity and the glow peak area reduce with shifting the glow peak to higher temperatures as a result of TQ, the new presented function gives more reliable results for the kinetic parameters.