C. Furetta

Effect of thermal treatment on TL response of CaSO4:Dy obtained using a new preparation method

We report the effect of thermal treatment on thermoluminescent (TL) sensitivity property of CaSO4:Dy obtained by a new preparation method at Instituto Nacional de Investigaciones Nucleares (ININ) of Mexico. Samples of phosphor powder were subjected to different thermal treatments respectively at 773, 873, 973 and 1,173K for 1h and then irradiated from 0.1 to 1,000 Gy gamma doses. Low energy dependence was analyzed too by irradiating with X-rays in the range of 16-145 keV. The results were normalized to the energy (1,252 keV) of (60)Co and they were compared with those obtained using the commercial dosimeters TLD-100. Also the kinetic parameters were determined by deconvolution of glow curve.

Isothermal decay method for analysis of thermoluminescence: a new approach

A variant of the isothermal decay method to determine the trap activation energy E in thermoluminescence is put forward. The area under the phosphorescence curve recorded at different temperatures is employed to calculate E by re-arranging the original equations by Randall–Wilkins, Garlick–Gibson and May–Partridge. As an example, the proposed method is applied to calculate E for a real phosphor and compared with other well-established methods.

Thermoluminescence characteristics of hydrogenated amorphous zirconia

This paper reports the experimental results concerning the thermoluminescent (TL) characteristics of hydrogenated amorphous zirconium oxide (a-Zr:H) powder prepared by the sol–gel method. The advantages of this method are the homogeneity and the purity of the gels associated with a relatively low sintering temperature. Hydrogenated amorphous powder was characterized by thermal analysis and X-ray diffraction. The main TL characteristics investigated were the TL response as a function of the absorbed dose, the reproducibility of the TL readings and the fading. The undoped a-Zr:H powder presents a TL glow curve with two peaks centered at 150 and 260 °C, respectively, after beta irradiation. The TL response a-Zr:H as a function of the absorbed dose showed a linear behavior over a wide range. The results presented open the possibility to use this material as a good TL dosimeter.

Computerized Glow Curve Deconvolution of Thermoluminescent Emission from Polyminerals of Jamaica Mexican Flower

The aim of this work is to study the main thermoluminescence (TL) characteristics of the inorganic polyminerals extracted from dehydrated Jamaica flower or roselle (Hibiscus sabdariffa L.) belonging to Malvaceae family of Mexican origin. TL emission properties of the polymineral fraction in powder were studied using the initial rise (IR) method. The complex structure and kinetic parameters of the glow curves have been analysed accurately using the computerized glow curve deconvolution (CGCD) assuming an exponential distribution of trapping levels. The extension of the IR method to the case of a continuous and exponential distribution of traps is reported, such as the derivation of the TL glow curve deconvolution functions for continuous trap distribution. CGCD is performed both in the case of frequency factor, s, temperature independent, and in the case with the s function of temperature.

Thermoluminescent properties of NaCl monocrystal double doped with CaCl2 and CdCl2

In the frame for searching new and very sensitive thermoluminescent (TL) materials for their use in dosimetric applications, this paper reports the TL properties of a new production of monocrystal NaCl, doubly activated by Ca and Cd in various concentrations. This TL material could be interesting for measurements in clinical dosimetry, i.e. radio therapy and radio diagnostic, for its effective atomic number, Zeff, which is 15.2, similar to the one of the bones. This paper reports the results concerning the TL response as a function of the absorbed dose and its analysis based on the track model [1–4], fading characteristics, kinetic parameters using the computerized glow curve deconvolution (CGCD) and some optical measurements.

Evaluation of thermoluminescent kinetics parameters of inorganic dust from the camomile

The polymineral dust extracted from the camomile herb was exposed to gamma radiation. The glow curves from these polyminerals show a large, single thermoluminiscence (TL) peak, centred at about 440 K. Because the large structure of the glow curves, it seems that the TL signal could be produced by a trap distribution instead of a single level of traps. The kinetic parameters of the glow curves have been accurately analysed using the computerized glow curve deconvolution (CGCD) method applied at different steps during a fading experiment at room temperature (RT). Deconvolution has been performed using a continuous distribution of trapping levels, uniformly distributed, including one additional peak in the high temperature region. This peak has been modelled with second-order kinetics of trap motion.

Thermoluminescence characterization of the irradiated minerals extracted from nopal

The mineral fraction from dehydrated nopal leaves (Opuntia ficus indica) belonging to the Cactaceae family was extracted and selected by sizes of 10 and 74 μm and exposed to 60Co gamma radiation at different doses in the range 70 Gy–20 kGy. The glow-curves from these polyminerals show a thermoluminescence (TL) band with one very intense peak at a temperature around 150 °C and a second one emerging in the high temperature region, moving in a large zone of temperature values according to the preparation used and the level of irradiation. The XRD analysis shows a composition of both biominerals as whewellite and weddellite and a mineral fraction as anorthoclase and quartz. The main TL characteristics of the polymineral content of the nopal was analyzed, i.e. the TL response at different doses and fading during storage at room temperature. The activation energy of the traps responsible for the TL emission was also investigated and a possible continuous distribution of traps is discussed. A review of the scientific literature shows that this is the first time that a TL study on nopal ionized by irradiation has been carried out.

Variation of the peak temperature at the maximum as a function of dose in thermoluminescent phosphors

A feature of the second and general-order kinetics equations is the shift of the peak temperature at the maximum towards lower temperatures as the dose increases. In this article, this effect is theoretically discussed. Some hypotheses are also given in order to explain this behaviour.

Luminescence detection and dose assessment of irradiated Yerba Mate (Ilex paraguariensis) tea leaves.

Imported commercial samples of Yerba Mate (Ilex paraguariensis) tea leaves were characterized by thermoluminescence (TL) and photoluminescence (PSL) physical methods. Samples of Yerba Mate were irradiated between 0.5-50Gy and 20Gy-5kGy gamma doses by using two different dose rates from (60)Co irradiators. The Electron Dispersive Analysis (EDS) shows that the inorganic fraction is mainly composed by quartz and Ca-feldspars minerals. These polyminerals show a good sensitivity to gamma radiation and to UV light (530nm). Linear dose-response curves were obtained between 0.5 and 12Gy at low dose-rate, and with 20 to 500Gy at high dose-rate of gamma radiation. At higher doses (600Gy) an apparent slow saturation effect was observed. Low fading of the TL signal was found. The detection limits of TL and PSL are 6Gy and 300Gy, respectively. Results show that luminescence emission (TL and PSL) is a reliable method for detection of irradiation Yerba Mate.

A fading-based method for checking the presence of closely overlapping peaks in thermoluminescent (TL) materials

The paper describes a method, based on fading experiment, for determining the presence of a complex structure in the thermoluminescent glow curve emission from herbs, e.g. oregano and nopal. Because of the polymineral content of the inorganic part of these herbs, the emitted glow curve is the result of several overlapping glow peaks, each one corresponding to another mineral. The initial rise method is also used for determining the activation energy of each component.