TL Intensity Research Articles

Identification of low amount of irradiated spices (red pepper, garlic, ginger powder) with luminescence analysis

For the identification of irradiated food, current analysis methods have limitations regarding presence and stability of radiation-induced markers. In this study, different spice blends with small quantity of different irradiated (0, 1 and 10kGy) spice powders, such as red pepper, garlic or ginger, were investigated using PSL and TL techniques. In PSL-based screening analysis, the spice blends containing 10% of irradiated materials (1 or 10kGy) were determined as intermediate or positive. In TL results, the blends containing 1% of 1 or 10kGy-irradiated spices showed the typical TL glow curves that could be interpreted as positive. The blends with irradiated garlic powder provided more good results where identification was possible at 0.5% mixing of irradiated sample. However, the TL ratios of all spice blends were <0.1 and only TL glow curve shape and intensity may be used to discriminate the samples having irradiated component.

Thermoluminescence analyses of irradiated dried sea foods using different methods of mineral separation

This research was conducted to find the most suitable parameters to separate minerals from irradiated dried shrimps and mussels (0 and 5kGy) for thermoluminescence analysis using density separation and modified acid hydrolysis (at 50°C with continuous agitation) methods. Nonirradiated samples gave TL glow curve of low intensity with peak after 300°C except dried mussel sample, which gave false positive result. This problem was absent in minerals separated by acid hydrolysis. TL ratios of all nonirradiated samples were <0.1 irrespective of method used for mineral separation. Minerals separated from irradiated samples by density separation showed very high intensity of TL glow peak before 200°C, where results from irradiated dried shrimp samples were better because of good availability of minerals. The minerals separated from irradiated samples by acid hydrolysis showed slightly low TL intensity and glow curve peak was found at about 200°C. However, acid hydrolysis method was less laborious and required less sample weight as compared to density separation method. TL ratios of all irradiated samples were >0.1 confirming the quality of minerals on TL discs.

Luminescent characteristics of CaSO4:Dy films obtained by spray pyrolysis method

The present paper reports the experimental results of dysprosium doped calcium sulphate (CaSO4:Dy) films deposited by spray pyrolysis method. CaSO4:Dy films were deposited on three different surfaces: glass, aluminum and quartz substrates at temperatures in the range from 450 to 600°C. Structural and morphological characteristics of CaSO4:Dy films were observed. Thermoluminescent characteristics of films were determined by irradiating ultraviolet energy region. Thermoluminescent glow curve of CaSO4:Dy films with glass and aluminum substrates showed a peak under environmental irradiation. Both TL response glow shape and intensity of CaSO4:Dy films UV irradiated as a function of substrates were studied.

Synthesis and luminescence in some fluoro-silicates for the possible applications in OSL dosimetry

Various fluoro-silicates, viz. M 2SiF 6 (M=Li, Na, K) were synthesized by reacting the mixture of corresponding salt and silicic acid with Hydrofluoric acid. The thermal analysis of these materials was performed. These materials were doped with ions Ce 3+, Cu +, Ag + and photoluminescence, TL, OSL properties were studied. Intense TL and OSL was observed from these materials. Due to decomposition during heating, these materials may not be suitable as TL Phosphors, but will be good phosphors for radiation dosimetry using OSL.

Synthesis and luminescence properties of rare earth doped gamma-ray-irradiated GdCa4O(BO3)3 phosphors

Undoped and rare earth (RE = Ce, Dy, and Eu) doped GdCa4O(BO3)3 phosphors were synthesized by solid-state diffusion technique. Formation of the sample was confirmed by taking X-ray diffraction (XRD) pattern of the sample. Photoluminescence (PL) emission spectrum showed characteristic emission of RE doped in the GdCa4O(BO3)3 sample. It is observed that doping of RE ion initially enhanced the TL yield, attained an optimum TL for a particular concentration of dopant (i.e., 0.5 mol%) then decreased with further increase in dopant concentration for all the samples. We found that Ce is the best activator for enhancing the TL yield in GdCa4O(BO3)3 system. Fading of TL intensity of the sample was studied and it is found that fading of the TL is about 5% over the period of 15 days. The simple glow curve, linear response to γ-ray dose and less fading; makes the GdCa4O(BO3)3:Ce(0.5 mol%) phosphors a suitable candidate for TL dosimetry.

Color center studies in KBr–NaI mixed crystals doped with gold

Abstract Mixed Alkali halide crystals containing KBr and NaI in different compositions were grown by slow evaporation technique. Obtained transparent crystals were doped with gold to study the role of dopant on the mixed crystals. Crystals were subjected to 60Co γ-radiation. The irradiated samples were subjected to Thermoluminescence, Optical Absorption and Electron Spin Resonance studies. Effect of Au + doping on TL intensity and absorption coefficient is discussed in the present paper.

Proposal for a new method to extract quartz from materials used for retrospective dosimetry and dating

Methods of luminescence induced by radiation, including thermoluminescence and optically stimulated luminescence, have been widely used for the determination of accumulated dose in crystals for retrospective dosimetry and archaeological dating. The determination of the radiation dose begins with the extraction of quartz from the sample studied. The methodology commonly applies acids, such as HCl and HF, to remove other compounds present in the natural samples. In this work, the effectiveness of this method is questioned, and an alternative method for the extraction of quartz is proposed. ► We examined the efficiency of chemical treatments for quartz extraction. ► TL intensity may varies up to 300%, depending on the chemical treatment used to quartz extraction. ► HF does not eliminate feldspars from archaeological and retrospective dosimetric samples. ► HNO 3 instead HF is suggested to extract quartz from samples in retrospective dosimetry and dating.

중첩중력에너지가 방사선 조사된 밀과 대두의 판별특성에 미치는 영향

The aim of this study was to investigate the changes in identification markers of irradiated foods after treatment of the full-overlapped gravitational field energy (FGFE). Wheat and soybean samples were irradiated at 0-5 kGy of Co-60 gamma energy, and analyzed for photostimulated and thermo luminescence characteristics (PSL and TL) and sprouting rate at 0 and 6th month after FGFE treatment. As a screening method for irradiated samples, PSL photon counts (PCs) for the non-irradiated samples appeared negative (5,000 PCs). But FGFE-treated irradiated samples appeared intermediate (700-5,000 PCs), showing decreased PCs during storage. The TL analysis on irradiated samples exhibited glow curve peaks in range of and TL ratio () was also >0.1. Therefore, identification of irradiated samples was possible using thermoluminescence. But the glow curve range of FGFE-treated irradiated samples shifted from to and TL intensity was decreased 37-60% resulting from FGFE treatment. After 6 months of storage, all the samples showed a decrease in TL intensity, but identification was still possible. The sprouting rate of irradiated samples decreased by about 72%, whereas that of FGFE-treated irradiated samples showed by about 85%, as compared to non-irradiated samples. More detailed study is required to investigate sprouting phenomena for FGFE-treated samples.

LiF:Mg,Cu,Si material with intense high-temperature TL peak prepared by various thermal treatment conditions

Abstract The LiF:Mg,Cu,Si thermoluminescence materials, recently developed at the laboratory, gain uprising popularity because the materials show several outstanding performance results such as high sensitivities for gamma radiation, flat energy responses with little fluctuation for photons, linear responses over the wide ranges of radiation doses and few residual electrons trapped in the holes. In this study, we investigated the impacts of the Mg concentration and the final thermal treatment conditions on the glow curve structure of LiF:Mg,Cu,Si material to enhance the ratio of high-temperature peak to main peak for the extended application of the two peaks in the high LET radiation dosimetry and in the high-temperature environment. Change in Mg concentration did not affect significantly the ratio of TL responses of high and main dosimetric glow peaks. With Mg concentration in the range from 0.35 to 0.45 mol% and a thermal treatment of 10 min in the range from 400 °C to 440 °C followed by the thermal treatment at 260 °C for 10 min (dual-step thermal treatment) resulted in the highest value of the ratio of TL response of high and main dosimetric glow peaks.

Study of effect of mechanical deformation on thermoluminescence of gamma-ray-irradiated Dy doped MgSO4 phosphors

Abstract In order to find the mechanical stability of traps/luminescence centers responsible for TL in MgSO 4 :Dy system, effect of deformation on TL of MgSO 4 :Dy was studied. TL glow curve of MgSO 4 :Dy phosphor is complex and peaks around 110, 150 and 220 °C were observed. Optimum TL was obtained for the sample having 0.1 mol% concentration of Dy in MgSO 4 system. Slight increase in intensity of 110 °C peak was observed when the TL glow curve was recorded after deforming the irradiated samples by dropping a piston of mass 0.4 kg onto it from the height of 0.2 m. Further increasing the height from which the piston was being dropped TL peak intensity of 110 °C decreased. However, 150 °C and 220 °C TL peak intensity decreased with deformation. Result showed that trap centers associated with 150 °C and nearby TL peaks were most mechanically unstable. TL spectrum of MgSO 4 :Dy phosphors was also recorded. Two peaks one at 490 nm and another at 590 nm were observed. In the TL emission spectra recorded for deformed samples, no significant change was seen in the peak positions. However, peak intensity was reduced. It is suggested that the recombination of electrons released from the traps during the thermal excitation is responsible for the TL emission in this system. It seems that in MgSO 4 :Dy system deformation does not cause any appreciable change in the recombination mechanism, it causes redistribution of traps and therefore change in relative TL intensity occurs in the same spectral region.

Mechanoluminescence and thermoluminescence of Mn doped ZnS nanocrystals

This paper reports the synthesis of ZnS:Mn nanocrystals by the chemical route in which mercaptoethanol was used as the capping agent. The particle size of such nanocrystals was measured using XRD and TEM patterns and was found to be in between 3and 5 nm. It was found that the peak position of TL glow curve and the TL intensity of ZnS:Mn nanoparticles increases as the particle size is decreased. The isothermal decay technique is used to determine the trap-depth. The stability of the charge carriers in the traps increase with the decrease in size of the nanoparticles. The higher stability may be attributed to the higher surface/volume ratio and also to the increase in the trap-depth with decreasing particle size. When a ZnS:Mn nanocrystal is deformed the peak intensity I m increases linearly with the increasing height of the load. After I m, initially the ML intensity decreases at a fast rate, and later on it decreases at a slow rate. The ML in ZnS:Mn nanocrystals can be understood on the basis of the piezoelectrically induced electron detrapping model.

Investigation of the trap state of Sr2MgSi2O7: Eu2+, Dy3+ phosphor and decay process

The thermoluminescence glow curves of Sr 2 MgSi 2 O 7 : Eu 2+ , Dy 3+ phosphor were measured after various delay times. A single trap center is confirmed that conforms to a kinetics model with order greater than 1, leading to a suppression of TL intensity and a high temperature shift of the TL peak with longer delay times. A constant trap depth supports this phenomenon. Further, the decay curve of the afterglow and the change in initial trapped carrier concentration can be fitted using general-order kinetics and the fitting results show that the afterglow is close to a second-order kinetics process, which implies that most of the released carriers are retrapped.

Investigation on the enhancement and the suppression of persistent luminescence of Re 3+ doped Sr 2EuMgSi 2O 7 (Re = Dy, Yb)

The enhancement and the suppression of persistent luminescence on Sr 2EuMgSi 2O 7 are investigated by Dy 3+ or Yb 3+ doping. The TL curves show the deep traps induced by Yb 3+ besides the intrinsic traps. The TL intensity of deep traps is stable whereas it decreases with preheating, indicating a charge carriers transfer process from the intrinsic traps to the deep ones. The mean lifetime of charge carriers in the deep traps is longer because of greater activation energy, restraining the detrapping. The similar process dominates the Dy 3+ doped sample with an optimum trap depth, resulting in the enhancement of persistence luminescence.

Thermoluminescence characteristics of CaS doped with rare earth ions Ce and Sm

CaS:Ce, Sm nanophosphors have been synthesized using solid state diffusion method with an aim to study the thermoluminescence characteristics of CaS:Ce,Sm system with varying concentrations of cerium and smarium in CaS host. The structural characterization of nanophosphors was done using XRD and TEM spectroscopy. We have investigated the effect of different concentrations of cerium and smarium in CaS host on the TL intensity. TL intensity is found to be maximum for CaS:Ce 0.4Sm 0.6. The effect of different heating rates on the TL glow curves recorded after a UV exposure of 560 mJ/cm 2 has been investigated. Peak of the TL glow curve shifts toward higher temperature as the heating rate increases and the TL intensity decreases. Effect of different doses of UV on the TL glow curve of CaS:Ce 0.4Sm 0.6 at a heating rate of 10 K/s has been studied and all the glow curves show a single peak around 440 K. With increasing dose the TL intensity increases linearly upto 560 mJ/cm 2 of the dose and afterward saturation region is obtained upto 13.5 J/cm 2. Beyond it a fall is recorded upto 80 J/cm 2 of the exposure. Analysis of the TL glow curve and calculation of the trapping parameters has been done with the help of Glow curve deconvolution software.

Dosimetric Characterization of LiF Doped with Unusual Dopants

LiF with different dopants has been one of the most investigated materials to use as thermoluminescent dosimeter. Even so, in a previous work we observed that pellets produced with pure LiF have applicability to ionizing radiation dosimetry, showing dosimetric peaks in temperatures high enough to overcome most of fading problems. In this work we studied the thermoluminescent properties of pellets prepared with LiF and unusual dopants. As dopants were tested rare earth metals like europium, terbium, dysprosium and neodymium. The more intense TL response was showed by samples doped with Nd. Although they are bluish due to presence of the Nd, the pellets produced with LiF:Nd exhibited a TL emission two times more intense than the one in pure LiF.

Luminescence characteristics of Ca1−xSrxS:Ce nanophosphors

Luminescence characteristics of Ca1−xSrxS:Ce (x=0, 0.25, 0.50, 1) nanophosphors have been investigated. XRD of all the samples show a single cubic phase of Ca1−xSrxS:Ce. TEM micrographs exhibit the rod like structure of the samples with a decrease in diameter with decreasing amount of Ca. The results of TEM were found to be in good agreement with the XRD results. The photoluminescence spectrum comprises of a main peak in the range 480–510nm with a shoulder in the range 530–565nm, which may be ascribed to transitions from 5d–4f levels of cerium in the mixed host lattice. The red shift in the emission wavelength with increasing Ca content may be correlated with the change in crystal field of mixed host lattice for different Ca and Sr concentrations. We have also investigated TL response of Ca1−xSrx:Ce to 60Co-γ rays. All the samples with different Sr and Ca contents show different TL response. TL response for the sample with x=0.75 shows the simplest TL glow curve with the maximum TL intensity, for which we have calculated the activation energy using glow curve deconvolution functions.

Investigation of thermoluminescence characteristics of CaSrS: Ce nanophosphors

Thermoluminescence characteristics of Ca 0.75Sr 0.25S: Ce nanophosphors exposed to UV radiations have been investigated. Solid state diffusion method was employed to synthesize the nanophosphors. The confirmation for the formation of the mixed lattice was done by XRD. The particles formed were found to have 45 nm size as calculated by the Debye Scherrer formula. TEM results were in close agreement with the XRD as the nanoparticles formed possess capsule like structure with an average diameter of 50 nm. TL glow curves for the low doses (110–1680 mJ/cm 2) of UV show a main peak around 381 K and another peak of very low intensity around 570 K. The TL intensity increases up to 450 mJ/cm 2 of UV exposure. At higher doses (3.5–80 J/cm 2) the peak position varies slightly but the high temperature peak becomes more intense. Thermoluminescence characteristics of UV irradiated Ca 1− x Sr x S: Ce as a function of x (0.25, 0.50, and 0.75) have also been investigated. TL glow curves of Ca 1− x Sr x S: Ce (0.25, 0.50, and 0.75) recorded after 450 mJ/cm 2 of exposure of UV radiations show almost similar structure except slight variation in the peak position. Ca 0.25Sr 0.75S: Ce and Ca 0.50Sr 0.50S: Ce have single peak at 373 and 367 K, respectively, while Ca 0.75Sr 0.25S: Ce has a main peak at 381 K and a less intense peak at 570 K. Ca 0.75Sr 0.25S: Ce shows the most intense TL peak. The trap parameters namely, activation energy ( E), order of kinetics ( b), and frequency factor ( s) of Ca 0.75Sr 0.25S: Ce have been determined using Chen’s peak shape method and GCD function suggested by Kitis for second order kinetics.

Optical and thermoluminescence characteristics of gamma irradiated Mn doped Li 2B 4O 7 single crystals

Li 2B 4O 7 crystals doped with Mn were grown by the Czochralski technique. The crystalline phase was determined by powder X-ray diffraction. Energy dispersive analysis of X-rays (EDAX) technique was used to confirm the Mn doping in the grown crystal. Thermoluminescence and optical investigations were carried out on these crystals. The polished crystal wafers were irradiated with different gamma dose using Co-60 source. Transmission spectra were recorded and analyzed for irradiated crystal wafers. Different absorption peaks were observed in the transmission spectra. Thermoluminescence studies show that with increase in dose level the TL intensity increases and the peak position shifts toward higher temperature. The influence of irradiation on the photoconductivity of these crystals was also studied.

Influence of Cu and Mn impurities on thermally stimulated luminescence studies of MgSO 4 compound

Thermally stimulated luminescence (TSL) of undoped and doped MgSO 4 with activators such as Cu and Mn has been investigated which are prepared by recrystallization method. The formations of undoped and doped MgSO 4 compounds are confirmed by XRD and FTIR studies. Photoluminescence studies have been undertaken to ensure the successful incorporation of Cu and Mn impurities in the MgSO 4 host lattice. Comparison of TL intensity of the most intensive glow peak of Cu and Mn doped MgSO 4 compounds with that of undoped MgSO 4 shows that addition of Cu and Mn impurity in MgSO 4 compound enhances the TL intensity by about 2.5 and 6 times respectively. The trap parameters namely order of kinetics ( b), activation energy ( E), frequency factor ( s) and Balarin parameter ( γ) associated with the most intensive glow peak of MgSO 4:Cu and MgSO 4:Mn phosphors were determined by using isothermal decay method and glow curve shape (Chen’s) method and these parameters are in good agreement.

Thermoluminescence characteristics of gamma irradiated CaS:Ce nanophosphors

Thermoluminescence behavior of gamma irradiated CaS:Ce nanophosphors have been presented. CaS:Ce (0.2 mol%) shows two peaks one around 400 K and a high temperature peak around 560 K at a heating rate of 5 K/s. TL intensity increases up to 5.76 kGy of gamma exposure and afterwards it decreases. The linearity of CaS:Ce nanophosphors over a wide range of dose is explained on the basis of track interaction model (TIM) and large surface to volume ratio of nanoparticles. Effect of different heating rates on the TL glow curve has also been investigated. The trapping parameters: activation energy ( E) and order of kinetics ( b) for CaS:Ce (0.2 mol%) have been calculated.