GlowFit—a new tool for thermoluminescence glow-curve deconvolution

Thermoluminescence properties of gamma-irradiated nano-structure hydroxyapatite

The suitability of nano-structured hydroxyapatite (HAP) for use as a thermoluminescence dosimeter was investigated. HAP samples were synthesized using a hydrolysis method. The formation of nanoparticles was confirmed by X-ray diffraction and average particle size was estimated to be ~30 nm. The glow curve exhibited a peak centered at around 200 °C. The additive dose method was applied and this showed that the thermoluminescence (TL) glow curves follow first-order kinetics due to the non-shifting nature of Tm after different doses. The numbers of overlapping peaks and related kinetic parameters were identified from Tm -Tstop through computerized glow curve deconvolution methods. The dependence of the TL responses on radiation dose was studied and a linear dose response up to 1000 Gy was observed for the samples.

An investigation of the dosimetric and kinetic properties of sand using ESR and TL techniques

In this research, the general dosimetric and kinetic properties of sand from a beach in southern Turkey were investigated using electron spin resonance (ESR) and thermoluminescence (TL) techniques. The ESR dose response curve presents linear behaviour in the dose range of 250-1000 Gy followed by sublinear behaviour in the dose range of 2-8 kGy. Kinetic behaviors and activation energy of the free radical were also calculated using the data obtained from annealing studies performed at four different temperatures (220, 240, 260 and 280°C). The activation energy value was calculated as 1.47 eV. The long-term fading of the ESR signal at room temperature turned out to be best described by a second-order kinetic decay function. The presence of measurable ESR signal intensity even after a storage period of 90 days was considered as providing an opportunity in the dose estimation of irradiated sand sample. Although the TL glow curve of the natural (unirradiated) sand sample only has a single broad peak at 317°C, the glow curve of the irradiated sample has four glow peaks located at ~115°C, ~156°C, ~231°C and ~308°C and their intensity tends to be increased with absorbed dose.Tmax-Tstop and glow curve fitting results showed that presence of at least five peaks located at ∼116°C, 149°C, 228°C, 306°C and 360°C. This result suggests that the apparently single glow peak D may consist of two or more overlapping glow peaks. According to the thermal fading of the sand sample at room temperature, the TL signal intensities (23°C and 308°C) were found to be quite large after 30 days of storage this allows a more accurate measurement of the glow peak intensity. The additive dose method, variable heating rate method (VHRM), Tmax-Tstop and glow curve fitting method were used to number of peaks, dosimetric properties and kinetic parameters. This study shows that ESR and TL techniques could be successfully used to investigate the kinetics and dosimetric properties of sand sample. Furthermore, the results in this study plus the previous work done by the authors suggest that sand could, by using the ESR and TL techniques, be a suitable material for alternative dose measurement.

Evolution of the CaF₂:Tm (TLD-300) glow curve as an indicator of beam quality for low-energy photon beams

We study the high- to low- temperature signal ratio (HLTR) of the CaF2:Tm glow curve as a function of beam quality for low-energy photon beams with effective energy between 15.2 and 33.6 keV, generated with W, Mo and Rh anodes. CaF2:Tm dosemeters (TLD-300) were exposed to x-rays and (60)Co gamma-rays. Glow curves were deconvoluted into 7 peaks, using computerized glow curve deconvolution and HLTR was evaluated. Air kerma and dose in water were between 2.1-15.0 mGy and 49.8-373.8 mGy, respectively. All peaks in the glow curve showed a linear response with respect to air kerma and dose in water. HLTR values decreased monotonically between 1.029  ±  0.010 (at 15.2 keV) and 0.821  ±  0.011 (33.6 keV), and no effects due to the use of different anode/filter combinations were observed. The results indicate a relatively high value of HLTR (about 1 for 17 keV effective energy, or 3 keV μm(-1) track-average LET) and a measurable dependence on the photon beam quality. Comparison of these photon data with HLTR for ions shows good quantitative agreement. The reported evolution of the CaF2:Tm glow curve could facilitate the estimation of the effective energy of unknown photon fields by this technique.

Influence of Ti4+ on the long lasting luminescence of Sr2SiO4:Eu2+

The Sr₂Si_0.95Ti_0.05O₄:Eu²⁺ phosphor was synthesized using titanium modified silica SBA-15 or titania as titanium precursors via a solid state synthesis method.

Thermally stimulated luminescence glow curve structure of β-irradiated CaB4O7:Dy

Thermally stimulated luminescence glow curves of CaB4O7:Dy samples after β-irradiation showed glow peaks at ~335, 530 and 675 K, with a heating rate of 2 K/s. The main peak at 530 K was analyzed using the Tmax-Tstop method and was found to be composed of at least five overlapping glow peaks. A curve-fitting program was used to perform computerized glow curve deconvolution (CGCD) analysis of the complex peak of the dosimetric material of interest. The kinetic parameters, namely activation energy (E) and frequency factor (s), associated with the main glow peak of CaB4O7:Dy at 520 K were evaluated using peak shape (PS) and isothermal luminescence decay (ILD) methods. In addition, the kinetics was determined to be first order (b =1) by applying the additive dose method. The activation energies and frequency factors obtained using PS and ILD methods are calculated to be 0.72 and 0.72 eV and 8.76 × 10(5) and 1.44 × 10(6) /s, respectively.

Deconvolution and simulation of thermoluminescence glow curves with Mathcad

The paper reports two quite general and user-friendly calculation codes (called TLD-MC and TLS-MC) for deconvolution and simulation, respectively, of thermoluminescence (TL) glow curves, which have been implemented using the well-known engineering computing software PTC Mathcad. An advantage of this commercial software is the flexibility and productivity in setting up tailored computations due to a natural math notation, an interactive calculation environment and the availability of advanced numerical methods. TLD-MC includes the majority of popular models used for TL glow-curve deconvolution (the user can easily implement additional models if necessary). The least-squares (Levenberg-Marquardt) optimisation of various analytical and even some non-analytical models is reasonably fast and the obtained figure-of-merit values are generally excellent. TLS-MC implements numerical solution of the original set of differential equations describing charge carrier dynamics involving arbitrary number of interactive electron and hole traps. The programs are freely available from the website http://www.physic.ut.ee/~kiisk/mcadapps.htm.

Effects of heating rate and dose on trapping parameters of TLD-100 crystals

The characteristics of the thermoluminescence glow curve and dosimetric peak of LiF:Mg,Ti (TLD-100) crystals are studied, with emphasis on the evaluation of the influence of the irradiation dose and heating rate on the dosimetric peak (peak 5) trapping parameters. These parameters were obtained using a computerized deconvolution routine that assumed first-order kinetics for each peak composing the glow curve. This routine was able to fit accurately (1.2% < FOM < 3.4%) all measured glow curves. It was found that for the evaluated range of photon doses (0.2 to 20 cGy) and heating rates (7 to 25 K/s), the behavior of the dosimetric peak was consistent with the predictions of the Randall-Wilkins first-order kinetic model. In particular, it was confirmed that the activation energy of the dosimetric peak is independent of the heating rate and irradiation dose, as expected from this model. The mean activation energy obtained for peak 5 was 2.27 ± 0.08 eV. The area under the experimental glow curves for the same dose remained stable regardless of the heating rate used, indicating that the thermal quenching effect did not have a significant influence within the studied range. By fixing the heating rate and varying the dose, it was found that the integral was proportional to the irradiation dose, as expected.

Highlights and pitfalls of 20 years of application of computerised glow curve analysis to thermoluminescence research and dosimetry

The technical and dosimetric aspects of computerised glow curve analysis are described in detail including a review of the current 'state-of-the-achieved' in applications to environmental and personal dosimetry, clinical dosimetry, quality control, characterisation of new materials, continuing characterisation of 'old' materials, heavy charged particle dosimetry, mixed field n-gamma dosimetry, X-ray dosimetry and other aspects of thermoluminescence dosimetry. Fearless emphasis is placed on 'pitfalls' as well as successes.