Search results for "THERMOLUMINESCENCE"
showing 10 items of 85 documents
Self-trapped holes and recombination luminescence in LiBaF3 crystals
2001
Abstract We investigated electron paramagnetic resonance (EPR) angular dependencies, recombination afterglow and thermostimulated luminescence of undoped LiBaF3 crystals, X-irradiated at low temperatures. EPR parameters of the F2− molecule oriented along the [1 1 0] direction have been obtained. Based on the value of the g-shift Δg=g⊥−gII=0.02, characteristic for the VK-centres in similar perovskites, we propose that we indeed observed the VK-centres, not the H-centres. X-irradiation below 170 K results in creation of a long-time temperature-independent afterglow due to the tunnelling recombination between close electron and hole centres. The F-type electron centres and the VK as well as pr…
Dosimetry in mixed gamma–neutron radiation fields and energy compensation filters for CaF2:Tm TL detectors
2008
Abstract Strong fields of thermal and epithermal neutrons as used for Boron Neutron Capture Therapy (BNCT) show a relatively small gamma dose. However, for accurate dose estimation, both the neutron as well as the gamma component has to be considered. Different approaches have been studied with various thermoluminescence detectors (TLDs). As a result, CaF2:Tm detectors (TLD-300) are attributed to be most insensitive to thermal neutrons but not tissue-equivalent. In this paper we focus on the measurement of the gamma dose with TLD-300 in mixed irradiation fields. To overcome the disadvantage of being not tissue-equivalent, a study on energy compensation filters was performed. The paper compr…
Advanced trap spectroscopy using the glow rate technique based on bleaching of color centers
2001
Abstract The glow rate technique (GRT) is the extension of the known heating rate method to the full glow curve. The GRT like the fractional glow technique (FGT) offers a procedure for evaluation of the mean activation energy as a function of temperature in the case of arbitrary thermostimulated relaxation kinetics represented by trap distribution function. The experimental procedure involves at least two subsequent measurements of thermostimulated recombination kinetics at different heating rates. The extension of the GRT to the direct measurements of thermostimulated bleaching of the radiation-induced color centers is presented. The experimental procedure involves measurements of the deca…
Thermoluminescence properties of AlN ceramics
1998
Abstract The paper describes thermoluminescence (TL) properties of AlN:Y 2 O 3 ceramics irradiated with ionising radiation. A high TL sensitivity of AlN:Y 2 O 3 ceramics to radiation encouraged a study of the AlN ceramics for application as a dosimetric material. The paper presents experimental data on: glow curve, emission spectrum, dose response, energy dependence, influence of heating rate and fading rate. The measured TL characteristics were compared with those of well-known, widely used TLDs, i.e. LiF:Mg,Ti, LiF:Mg,Cu,P and Al 2 O 3 :C. It is concluded that AlN:Y 2 O 3 ceramics showing a radiation sensitivity which is approximately 50 times greater than that of LiF:Mg,Ti is an interest…
Stimulated luminescence of AlN ceramics induced by ultraviolet radiation
2001
Abstract Properties of thermally stimulated luminescence (TL) and optically stimulated luminescence (OSL) of the ceramic material AlN-Y 2 O 3 have been studied after exposure to ultraviolet radiation (UVR). The dosemeter material Al 2 O 3 : C has been used for comparative measurements. The spectral sensitivity of the samples has been studied and compared with spectral effectiveness of the UVR-induced biological processes. It has been shown that a very high yield and linear dose response characterise the UVR-induced TL from AlN-Y 2 O 3 . Although lower than the TL, the OSL signal from UV-exposed AlN-Y 2 O 3 is still higher than that of Al 2 O 3 : C in a broad spectral region. The possibilit…
Localised transitions in luminescence of AlN ceramics
2014
Abstract The photoluminescence (PL) and thermoluminescence (TL) properties of AlN ceramics revealed under UV irradiation are determined mainly by oxygen-related centres, giving rise to the UV (around 3.18 eV) and the Blue (2.58 eV) bands. It was found that the UV irradiation-generated donor–acceptor pairs (DAPs), responsible for the UV emission band, are randomly distributed with regard to separation distance. Luminescence properties of AlN are interpreted basing on the model of localised recombination involving electron tunnel transitions from the excited state of D to the ground state of A, proposed by Jain et al. (2012) . The observed features of PL, afterglow and TL of AlN ceramics are …
Radiation induced luminescence processes in c-BN
2004
Abstract Spectral properties of cubic boron nitride have been studied using methods of photoluminescence (PL), X-ray excited luminescence (XL), thermoluminescence (TL) and optically stimulated luminescence. It is found that emission of cubic boron nitride is presented by 4 subbands, their relative yield is determined by the excitation type: blue, green (dominant) and red bands are observed in PL, ultraviolet, blue (dominant), green and red bands—in XL. Three thermal peaks are found in TL curves in the 0–700°C temperature range, their presence and intensity depend on radiation type used. A tentative correspondence between thermal peaks and emission bands is found.
A practical and transferable methodology for dose estimation in irradiated spices, based on thermoluminescence dosimetry
2008
Abstract The thermoluminescence technique is recommended by the European Committee for Standardization for the detection of irradiated food containing silicates as contaminants. In this work, the applicability of the thermoluminescence technique as a quantitative method to assess the original dose in irradiated oregano was studied; the additive-dose method was used, with reirradiation doses up to 600 Gy. The proposed new procedure allows to clearly discriminate irradiated from unirradiated samples, even after one year storage, and it gives an acceptable estimation of the original dose; the overall modified procedure requires only one day to be completed.
The luminescence of ZnO ceramics
2010
Abstract The luminescence properties of ZnO ceramics with grains 100–5000 nm sintered by different techniques from nanopowders were studied. The luminescence decay times were compared with that obtained for ZnO single crystal. The temperature dependence of non-exponential decay of defect luminescence (2.0–2.6 eV) was measured in wide time, intensity and temperature range. The luminescence decay kinetic at T ≤ 20 K shows the decay close to I(t) ∼ t−1 dependence. At temperature region 50–250 K the decay kinetics is more complicate since the TSL was observed in this temperature region. It is shown that the luminescence properties of NP and ceramics strongly depend on defect distribution on gra…
Thermally and optically stimulated radiative processes in LiBaF3 crystals
2004
Abstract In LiBaF3 crystals both valence–core transitions (5.4– 6.5 eV ) and so-called self-trapped exciton luminescence (about 4.3 eV ) are important for practical application. Here, we present a study of 4.3 eV luminescence under photo- and thermostimulation after X-irradiation of undoped LiBaF3 crystals at various temperatures. Optically stimulated luminescence as a result of electron recombination with both self-trapped holes and holes localized at some defects, were observed after X-irradiation below 130 K and that of electron recombination with defect-localized holes was observed after X-irradiation above 130 K . The spectra of thermo-stimulated luminescence (TSL) contain a broad band…