Theoretical modeling and numerical solutions of the some standard thermoluminescence detector crystals (original) (raw)
Related papers
Radiation Measurements, 2008
By employing a model of interactive traps which conforms to experimental findings the glow curve of K 2 YF 5 : Pr 3+ compounds has been analysed. A novel algorithm, which allows the decoupling of the equations describing the carrier traffic among traps, recombination centres and energy bands, is reported. An important conclusion drawn from the results is that it is not always correct to think of each single peak as related only to one trap.
On the theoretical basis for the duplicitous thermoluminescence peak
Journal of Physics D: Applied Physics, 2009
The simultaneous release of electrons and holes by what seems to be a single trap has been observed experimentally. We previously performed numerical simulations on a phenomenological model which showed similar behaviour. Here, we provide an analytical solution to this model. This model explains trends in radioluminescence, thermoluminescence and thermally stimulated conductivity of a material with one electron trap, one hole trap and one radiative recombination centre, in which thermal excitation of the electron trap occurs before that of the hole trap. It is shown that TL emission due to electron recombination at centres can be controlled by a hole trap and the electron recombination will have a peak shape associated with the hole trap's parameters. When this happens, the peaks in free electron concentration, free hole concentration and TL all occur nearly simultaneously. The analytical model allows this to be explained along with scaling laws and initial rise behaviour. Under the conditions illustrated by this model, the usual methods used to distinguish between electron traps and hole traps will give incorrect results.
Radiation Measurements
A thermoluminescence (TL) glow peak may result from a transition of electrons from traps into the conduction band, followed by a recombination with holes trapped in a luminescence center. Another possibility is that holes trapped in a hole trap are thermally released into the valence band and recombine with electrons in an electron recombination center. A series of glow peaks emitted from a given sample may include peaks of both kinds. In some cases, peaks may be identified as being of one kind or the other, say, by using thermally stimulated electron emission (TSEE), which can take place when the free carriers are electrons. In the present work, we demonstrate by the use of simulation that two peaks may result from one electron and one hole trapping states and a single hole recombination center. The first TL peak is observed when thermally stimulated electrons recombine with holes in the center. The TL peak is terminated when the holes in the center are exhausted. At higher temperatures, holes from a hole trap are released into the valence band and then captured by the hole center, thus this center is replenished. More electrons from the electron trap are thermally released now and recombine with the newly arrived holes in centers. A second TL peak may be observed which carries some information concerning the hole trap. It is thus demonstrated that some of the usual methods for distinguishing between electron and hole traps can lead to incorrect conclusions. It is possible for a hole trap, for example, to induce an increase in electron recombination in such a way that it produces a peak that looks nearly identical to TL from an electron trap. This simulation may bring about a new look at TL peaks occurring in materials used in TL dosimetry and dating. A new interpretation may also be given to "Auger" TSEE associated with the thermal release of electrons from the surface of a material, which indirectly results from the thermal release of holes from traps. The performance of some methods for evaluating the activation energies and the significance of the results in the present situation are discussed.
Journal of Luminescence, 2014
An overview of the successes and failure of the computerized glow curve deconvolution (CGCD) and the peak shape methods in describing the glow peaks generated from the fundamental one trap-one recombination center (OTOR) model was discussed. Also, the existing method, and a new developed one, to test the applicability of the existing thermoluminescence (TL) expressions to describe the glow peaks were discussed. The new TL expressions deduced by Kitis and Vlachos ([17] G. Kitis, N.D. Vlachos, Radiat. Meas. 48 were tested in the cases in which the other existing TL expressions failed. The results showed that the error in the calculated activation energy (E) using the existing expressions may reach up, in some cases, to 50%. While, using the new TL expressions, the error in the calculated E did not exceed 0.5%.
Mechanism of thermoluminescence
2012
This investigation presents the theory for the phenomenon of thermoluminescence (TL). The basic principle gives simple model to the emission of light from an insulator or semiconductor by released charge carriers from traps when it is heated. In this study has be explain the three essential ingredients necessary for the production of thermoluminescence, first, second and generalorder kinetic. This work lead to explain methods to analysis TL glow peaks to determine various parameters, such as the trap depths E and the frequency factors S. This work provides simple information to understand the thermoluminescence.
Journal of Physics D: Applied Physics, 1998
In this paper, thermoluminescence glow curves of gamma irradiated magnesium borate glass doped with dysprosium were studied. The number of interfering peaks and in turn the number of electron trap levels are determined using the Repeated Initial Rise (RIR) method. At different heating rates (β), the glow curves were deconvoluted into two interfering peaks based on the results of RIR method. Kinetic parameters such as trap depth, kinetic order (b) and frequency factor (s) for each electron trap level is determined using the Peak Shape (PS) method. The obtained results indicated that, the magnesium borate glass doped with dysprosium has two electron trap levels with the average depth energies of 0.63 and 0.79 eV respectively. These two traps have second order kinetic and are formed at low temperature region. The obtained results due to the glow curve analysis could be used to explain some observed properties such as, high thermal fading and light sensitivity for such thermoluminescence material. In this work, systematic procedures to determine the kinetic parameters of any thermoluminescence material are successfully introduced.
On the quasi-equilibrium assumptions in the theory of thermoluminescence (TL)
Journal of Luminescence, 2013
The phenomenon of thermoluminescence (TL) is governed by a set of simultaneous differential equations. When one studies the properties of a single peak, resulting from the thermal release of electrons from a trap into the conduction band, followed by radiative recombination with holes in centers, the set consists of three non-linear equations. Even in this simple case, the equations cannot be solved analytically. In order to get approximate solutions, the conventional way has been to make the ''quasi-equilibrium'' assumptions, namely that 9dn c /dt9 is significantly smaller than 9dn/dt9 and 9dm/dt9, where n and m are the occupancies of traps and centers, respectively, n c is the concentration of electrons in the conduction band, and n c {n; n c {m. We show, using simulations as well as analytical arguments that the former condition often does not occur; however, its consequences are valid. The reason is that the conventional quasi-equilibrium assertion must be replaced by a different condition. As for the smallness of the concentration of free electrons, we show that it may not be fulfilled at the high-temperature end of a single glow peak or in the highest-temperature peak in a series. In some cases, this condition results in a broad high-temperature tail of the TL peak, as previously observed experimentally in several materials.
Thermoluminescence kinetics for multipeak glow curves produced by the release of electrons and holes
Journal of Physics D: Applied Physics, 1986
A model is described for the calculation of multipeak glow curves. A set of (km + jm + 2) equations are presentedwhich describe the flow of electrons and holes between km different electron trapping levels, jm different hole trapping levels and the conduction and valence bands. The model can be applied to complex cases where glow curves result from both electron and hole transport. A computer program has been written to solve the system of equations numerically. Calculated glow curves for a number of interesting cases are presented and some other applications of the model are briefly discussed.
The two-level version of semi-localized transitions (SLT) model for thermoluminescence dosimeter
Radiation Measurements, 2019
Mandowski (2005) has developed the semi-localized transitions (SLT) model which is the combination of both simple trap model (STM) and localized transition (LT) model. This model explained anomalous behaviours such as displacement peaks, double peaks, etc. The SLT allows trapped charge carriers to be excited to the conduction band. Calculated TL glow curves of the SLT model show two peaks that are related to transition of the charge carrier between trap and excited state. This additional peak named displacement peak was shown in several TL studies. The researchers have shown that, the main peak of LiF:Mg,Ti, consists of three overlapping glow peaks in which the peak 5a is believed to be related to LTs, while the peak 5 relates to carriers that escaped from the T-RC pair system. In this study, SLT model is simulated using Matlab code and numerical results are presented. Also, the two level version of SLT model is presented including all possible transitions. In new version of SLT model two excited states are considered. Recombination of trapped charge careers occur via two localized and one delocalized transitions simultaneously. Using the two-level version of SLT model, it is shown that existence of more peaks is possible in glow curve.