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1.
Marcos A.P. Chagas Maíra G. Nunes Letícia L. Campos Divanizia N. Souza 《Radiation measurements》2010,45(3-6):550-552
CaSO4:Tm is excellent phosphors for dosimetry of ionising radiations due to their high sensitivity, wide dose range (from 10?6 to 1 Gy), relatively simple trap structure, good chemical, thermal and physical stability and ease of preparation. Since 1968 have been developed new methods of preparing aim to increase the sensitivity and the linearity of the CaSO4:Tm thermoluminescence. The objective of this work is to obtain single crystals of CaSO4:Tm under controlled crystal growth conditions, such as temperature, atmosphere and velocity, aiming to improve the TL sensitivity of the crystals and investigate its dosimetric properties in order to evaluate the applicability of this material to dosimetry. 相似文献
2.
J. Manam 《辐射效应与固体损伤》2013,168(12):955-965
Thermally stimulated luminescence (TSL) of undoped and doped CaSO4 with activators such as Cu and Mn has been investigated. The polycrystalline samples of undoped and doped CaSO4 are prepared by the melting method. The formation of CaSO4 compound is confirmed by X-ray diffraction and Fourier transform infrared studies. Scanning electron microscopic studies of CaSO4 are also carried out. The TSL glow curves of undoped CaSO4, Cu- and Mn-doped CaSO4 are studied. Comparison of the thermoluminescence (TL) intensity of the most intensive glow peak of Cu-doped CaSO4 compound with that of undoped CaSO4 shows that addition of Cu impurity in CaSO4 compound enhances the TL intensity by about four times. However, the addition of Mn impurity to undoped CaSO4 increases the TL intensity by about three times when compared with that of undoped CaSO4. The TL-dose dependence of all three samples was studied and was observed to be almost linear in the studied range of irradiation time. Among the samples studied, namely undoped CaSO4 and Cu- and Mn-doped CaSO4, Cu-doped CaSO4 is found to be the most sensitive. The trap parameters, namely order of kinetics (b), activation energy (E) and frequency factor (s) associated with the most intensive glow peaks of CaSO4:Mn, CaSO4:Cu and CaSO4 phosphors were determined using the glow curve shape (Chen's) method. 相似文献
3.
The XRD and SEM and TSL studies of the as prepared pure, Cu and Mn doped CaSO4 have been carried out. From the comparative TSL studies it has been seen that the 137 °C glow peak of CaSO4:Cu is superior to undoped and Mn doped CaSO4 compounds as well as other Cu doped alkaline earth sulphates. Evaluation of trapping parameters of the most intensive glow peak Cu (0.5 mol%) doped CaSO4 is accomplished by a technique named isothermal luminescence decay method and comparison of these parameters with the previously calculated trapping parameters by glow curve shape method (Chen’s method) have been done. It is observed that the most intensive glow peak of Cu doped CaSO4 is found to obey second order kinetics, because of availability of vacant traps for retrapping to take place. Moreover the effect of various doping concentration of Cu on the TSL glow curve and reproducibility of Cu doped CaSO4 has also studied. 相似文献
4.
The effects of sub-ambient temperatures of irradiation and dose response of CaSO4:Dy phosphor was investigated. The irradiation dose in the range 0.5–7.0 kGy was chosen to meet the requirement of commercial food irradiation at low temperature. Commercially available phosphor showed no significant change in glow curve structure with low temperature of irradiation. In order to enhance the sensitivity of the low temperature glow peak (142 °C), the phosphor was subjected to different post-preparation thermal treatments at 700–900 °C. The change in glows and improvement in dose response characteristics were explained by Electron Paramagnetic Resonance (EPR) spectroscopy. At sub-ambient temperature of irradiation, the behavior of thermally treated CaSO4:Dy phosphor with increasing dose revealed improved linear response of the low temperature glow peak and could be an efficient dosimetry system for the food commodities irradiated at low temperatures. 相似文献
5.
Thermoluminescence (TL) characteristics of recently developed high sensitive mixed halosulphate phosphors, NaMgSO4Cl: Cu and NaMgSO4Cl: Ce were studied in comparison with CaSO4: Dy in order to assess the possibility of their use in personal monitoring and TLD phosphors at very low dose of 5 Gy. It was found that NaMgSO4Cl: Cu is 5.59 times and NaMgSO4Cl: Ce is 6.18 times more sensitive as compared to standard CaSO4: Dy. UV photo-excited luminescence from Cu to Ce doped NaMgSO4Cl halosulphate phosphors has been investigated. The intense emission of the spectrum is assigned to electronic transitions 3d94s1→3d10 in monovalent copper ion and 5d→4f in Ce3+ ions. Increase in PL peak intensity suggesting that Cu and Ce play an important role in PL emission in the present matrix. These phosphors were synthesized by the wet chemical method. XRD, photoluminescence (PL) and thermoluminescence (TL) characterization of phosphors has been reported in this paper. The preparation of an inexpensive and high sensitive NaMgSO4Cl: Cu and NaMgSO4Cl: Ce with TL glow peaks for different concentrations are observed between 160 and 195 °C and between 200 and 225 °C, respectively, exposed to gamma-rays of 60Co for their thermoluminescence (TL) properties. The glow curves have been recorded at a heating rate of 2 K s?1 and irradiated at a dose rate of 0.995 kGy h?1 for 5 Gy. In present study the trapping parameters such as order of kinetics (b), activation energy (E) and frequency factors (s) have been calculated for the 195 and 200 °C glow peaks of NaMgSO4Cl: Cu and NaMgSO4Cl: Ce, respectively by using Chen's method. The paper discusses the luminescence of Cu+ and Ce3+ by simple method of incorporation in NaMgSO4Cl host. 相似文献
6.
The thermoluminescence (TL) of rare earth (RE) activated sulfates of Cd, Sr and Ba was studied above room temperature. Many of the phosphors prepared exhibit an extremely bright TL following X-irradiation (most notably with Sm, Eu, Tb, Dy and Tm dopants), having an efficiency comparable to that of the highest sensitivity phosphors available for TL dosimetry, and exhibiting activator-induced glow peaks between 405 and 480°K. In a given lattice, the RE3+ ions produce a characteristic glow peak at the same temperature (independent of the particular RE ion), whereas Eu2+ produces a single glow peak at a different temperature. A decrease in glow peak temperature with increasing interatomic spacing was observed in the homologous SrSO4-BaSO4 system - this shift being most pronounced in the Eu2+ -doped materials. TL emission spectra were obtained for trivalent Sm, Tb, Dy and Tm and for divalent Eu in these sulfates (and also in CaSO4). 相似文献
7.
N.S. Rawat M.S. Kulkarni M. Tyagi P. Ratna D.R. Mishra S.G. Singh B. Tiwari A. Soni S.C. Gadkari S.K. Gupta 《Journal of luminescence》2012,132(8):1969-1975
Lithium borate (LBO) single crystals doped with Cu and Ag (0.25 mol% each) (Li2B4O7:Cu,Ag) are grown by the Czochralski method. The thermoluminescence readout on Li2B4O7:Cu,Ag crystals showed three glow peaks at~375, 441 and 516 K for the heating rate of 1 K/s. The thermoluminescence sensitivity of the grown Li2B4O7:Cu,Ag single crystals is found to be 5 times TLD-100 and a linear dose response in the range 1 mGy to 1 kGy. The glow curve deconvolution reveals nearly first order kinetics for all the three peaks with trap depths 0.77, 1.25 and 1.34 eV respectively and corresponding frequency factors 1.6×109, 1.3×1013 and 6.8×1011 s?1. The continuous wave optically stimulated luminescence (CW-OSL) measurements were performed on the LBO:Cu,Ag single crystals using blue light stimulation. The traps responsible for the three thermoluminescence peaks in Li2B4O7:Cu,Ag are found to be OSL sensitive. The qualitative correlation between TL peaks and CW-OSL response is established. The photoluminescence studies show that in case of co-doping of Ag in LBO:Cu the emission at 370 nm in Cu states dominates over the transitions in Ag states implying doping of Ag plays a role as sensitizer when co-doped with Cu and increases overall emission. 相似文献
8.
The TL response of LiF:Mg,Ti microdosimeters and CaSO4:Dy dosimeters were studied for 12 MeV electron beams using PMMA, liquid water and solid water (SW) phantoms. The different phantom materials affect the electron spectrum incident on the detector and it can alter the response of dosimeters to different radiation types, so this fact should be considered in clinical dosimetry. The dosimeters were irradiated with doses ranging from 0.1 up to 5 Gy using a Varian Clinac 2100C linear accelerator of Hospital Israelita Albert Einstein – HIAE using a 10 × 10 cm2 field size and 100 cm source-phantom surface distance, with the dosimeters positioned at the depth of maximum dose. The TL readings were carried out 24 h after irradiation using a Harshaw 3500 TL reader. This paper aims to compare the TL response relative to 60Co of the dosimeters for different phantoms used in radiotherapy dosimetry. CaSO4:Dy dosimeters presented higher TL sensitivity relative to 60Co and intrinsic efficiency than microLiF:Mg,Ti dosimeters for all phantoms. 相似文献
9.
Thermoluminescence emission spectra are presented for lithium doped variants of CaSO4:Dy or CaSO4:Tm dosimetry material. All three dopants (Li, Dy and Tm) variously introduce different changes in both the glow peak temperatures and the luminescence efficiency. In every case the emission signals display the line emission characteristic of the rare earth ions. At temperatures below ∼50 K the relative peak intensities differ for Dy and Tm doped samples, and there are small temperature shifts between the Dy:Li and Tm:Li co-doped materials. Above room temperature the rare earth ions do not show peak temperature movements when co-doped with lithium. However they do influence the peak temperature by ∼5 °C when they are the sole dopant. Inclusion of lithium dramatically moves the high temperature glow peak from ∼200 °C down to 120 °C. All these changes are consistent with a single defect model in which the trapping sites and luminescence occur within the complexes formed of the rare earth ion, an intrinsic sulphate defect and lithium. The evidence and rationale for such a model are presented. There is discussion which suggests that such defect complexes are the norm in thermoluminescence. 相似文献
10.
In this study, Li2BPO5 doped with Cu and that co-doped with Mg are synthesized by the wet chemical technique and exposed to γ rays of 60Co to determine their thermoluminescence (TL) properties. The X-ray diffraction technique shows the crystalline nature of the prepared material. The photoluminescence (PL) emission spectra of Li2BPO5:Cu phosphor show the strong prominent peak at 368 nm in the violet region of the visible spectrum due to the transition of 3d94s1 ? 3d10 of monovalent copper ion. The PL emission of Li2BPO5:Cu is enhanced by the addition of Mg. The TL glow curves of γ-irradiated Li2BPO5:Cu sample show one glow peak at 143°C, indicating that only one set of traps is being activated within the particular temperature range each with its own value of activation energy (E) and frequency factor (s). The trapping parameters associated with the prominent glow peak of Li2BPO5:Cu are calculated using the glow curve shape (Chen's) method. The release of hole/electron from defect centers at the characteristic trap site initiates the luminescence process in these materials. A linear TL response is observed in Li2BPO5:Cu in a long span of exposures. The sensitivity of Li2BPO5:Cu sample is observed to be 7.8 times that of (TLD-100) LiF:Mg, Ti. 相似文献
11.
An abundant set of published experimental NMR/NQR data on electric field gradients in ReBa2Cu3O7−δ
high temperature conductors, where Re=Y and Tm, is used as a test for the singlet-correlated band theory. Because of the
unusual spectral weight (“capacity”) of this band, it has been possible to match the number of holes per lattice site to photoemission
data on the energy spectrum and the location of the Fermi level. In the framework of a unified picture of the distribution
of holes (charges) it has been possible for the first time to explain satisfactorily the observed electric field gradients
at the Cu(1), Cu(2), O(1), O(2), O(3), and O(4) sites, as well as NMR and inelastic neutron scattering data on the crystal
electric field at the Tm ions.
Zh. éksp. Teor. Fiz. 111, 144–157 (January 1997) 相似文献
12.
Thermoluminescence (TL) and photoluminescence studies have been carried out on CaSO4:Tb, CaSO4:Ce and CaSO4:Tb,Ce phosphors with the aim of studying energy transfer process in the CaSO4:Tb,Ce phosphor. CaSO4:Tb,Ce shows TL peaks at 150, 220, 320 and 400°C. Changes in Tb and Ce concentrations influence the relative heights of these glow peaks. Co-doping with 0.1 mol% of Ce in CaSO4:Tb enhances the sensitivity of 320oC TL peak by a factor of 15. Fluorescence results show that there is energy transfer from Ce to Tb ion. The defect centres formed in CaSO4:Tb,Ce phosphor are studied using electron spin resonance technique. The 320oC glow peak correlates with a centre (SO3−radical) with g-values: g||=2.0061 and g⊥=2.0026. 相似文献
13.
This work evaluates the dosimetric properties of crystals of CaSO4 doped with unusual elements, such as europium (Eu) and silver (Ag), including their nanoparticle forms, after the incorporation of glass or Teflon and compares them with well-known thermoluminescent dosimeters (TLD). X-ray diffraction analyses showed that samples of doped CaSO4 exhibit only a single phase corresponding to the crystal structure of anhydrite. Optical spectroscopy confirmed the presence of Eu3+ in the crystal matrix and a luminescent gain due the presence of silver nanoparticles. The composites showed thermoluminescent emission glow curves, with a single peak centered at approximately 200 °C for pellets with Teflon and at 230 °C for pellets with glass. The dosimeters based on calcium sulfate doped with europium and silver nanoparticles provided the most intense thermoluminescent (TL) emission of the composites studied. In comparison with commercial TLD, such as LiF:Mg,Ti and CaSO4:Dy, the CaSO4:Eu,Ag(NP)+glass produced in this work presented similar low detection limits and higher sensitivity. The new methods for the preparation of dosimeters and the incorporation of glass are shown to be viable because all of the samples presented a linear, reproducible and first order kinetic TL emission. 相似文献
14.
用电子束蒸镀工艺制备了自旋阀型[NiFe/Cu/Co/Cu]N多层膜.研究了工艺过程及磁层、非磁层厚度和矫顽力对磁电阻的影响.还研究了磁电阻的稳定性和降低中心磁场等问题.用较优化的方法,制备了中心磁场为(10—20)(103/4π)A/m,优值大于0.2%((103/4π)A/m)-1的多层膜.实验表明,磁电阻随磁场的变化在中心区内是可逆的.经200℃退火15min,中心磁场略有减小,磁电阻稍有增加.一些样品经一年多老
关键词: 相似文献
15.
S. Atalay V. YagmurF.E. Atalay N. Bayri 《Journal of magnetism and magnetic materials》2011,323(22):2818-2822
Co19Ni49.6Fe31.4 layer was electrodeposited onto a twisted Cu wire and helical anisotropy was induced in the magnetic Co19Ni49.6Fe31.4 shell. The magnetic and coil-less fluxgate (CF) properties are presented. The Co19Ni49.6Fe31.4/Cu wire, produced at zero torsional strain, shows a CF output of nearly zero. The samples produced under torsional strains of 29.5π and 59π rad/m show a linear change in CF output in the low-frequency range. At higher frequencies the CF output shows two linear ranges. A maximum sensitivity of 150V/T is observed at 20 kHz driving-current frequency and 67 mA driving current for a wire produced under 59π rad/m torsional strain. It is also found that the slope of the CF curve depends on the direction of induced anisotropy. 相似文献
16.
ZnS:Cu nanophosphors were prepared by wet chemical methods and characterized by X-ray diffraction (XRD). The typical morphologies of the nanophosphors were investigated by scanning electron microscopy (SEM). The thermoluminescence (TL) properties of inorganically and organically passivated ZnS:Cu nanophosphors were investigated after γ-irradiation using a 60Co source at room temperature. The TL glow curve of capped ZnS:Cu showed variation in TL peak and intensity as the capping agent was changed. Amongst the synthesized samples the TL glow curve of SiO2 capped ZnS:Cu showed the highest TL intensity. It has been found that TL response of SiO2 capped ZnS:Cu is linear in the range 10-550 Gy. A discussion of the obtained results is also presented. 相似文献
17.
A new OSL phosphor CaSO4:Eu was developed. The phosphor shows good OSL sensitivity which is about 55% of commercially available Al2O3:C. The phosphor also shows good TL sensitivity and the dosimetric peak, which appears around 186 °C, has sensitivity nearly 50% of Al2O3:C. After OSL readout of the irradiated sample, the TL peak around 250 °C depletes completely, with partial depletion of peak around 186 °C. Since the traps responsible for the high temperature peak are involved for the observed OSL, the sample shows low post-irradiation fading. The OSL decay is similar to Al2O3:C. Thus this phosphor due to its good OSL sensitivity, linear dose response, low fading and simple preparation technique could be useful for radiation dosimetry applications. 相似文献
18.
P. Alippi Vincenzo Fiorentini 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(2):82
We study a selection of Cu-containing magnetic quadruple perovskites
(CaCu3Ti4O12
LaCu3Fe4O12, and
YCu3Co4O12) by ab initio calculations, and show that Cu
is in an effective divalent Cu(II)-like state or a trivalent Cu(III) state depending on
the choice of octahedral cation. Based on the electronic structure, we also discuss the
role of Mott and Zhang-Rice physics in this materials class. 相似文献
19.
以高纯α-Al2O3和石墨为原料,采用温梯法生长了α-Al2O3:C晶体,使用Ris TL/OSL-DA-15型热释光和光释光仪研究了其热释光和光释光特性.α-Al2O3:C晶体在462K附近有单一热释光峰,发射波长位于410nm.随着辐照剂量的增加,热释光强度逐渐增强,462K的热释光特征峰位置保持不变.α-Al2O3:C晶体的
关键词:
2O3:C')" href="#">α-Al2O3:C
热释光
光释光 相似文献
20.
Two experiments were performed to determine the distribution of beta dose in a target medium as a function of distance from a planar source (2π geometry). In Experiment 1 planar absorbers were used to simulate depth in the target medium, and the attenuated dose that penetrated the intervening absorbers was detected using thermoluminescence from CaSO4:Tm. In experiment 2 pellets of powdered tooth enamel were situated in a cavity in solid tooth enamel. Dose response of the electron spin resonance (ESR) signals in the pellets allowed direct detection of dose distribution within the target medium. The dose distributions were found to agree more closely with Monte Carlo calculations and with one-group transport theory (Prestwich et al., 1997 and Brennan et al., 1997) than with approximations used widely in ESR dating applications (Grün, 1986). Although the latter were supported by experiments by Aitken et al. (1985), the results of experiment 1 provided data to suggest that departure from 2π geometry was unacceptably large in the Aitken et al. (1985) configuration. The beta doses obtained by one-group theory in typical target volumes of enamel were 17 to 40% lower than those obtained using the Grün approximation. It was concluded that one-group transport theory provides the best available routine tool for calculations of beta dose attenuation in near-planar target materials (e.g. tooth enamel and shell) irradiated by natural sources, although Monte Carlo methods are better and could eventually be introduced into the ROSY ESR dating program (Brennan et al., 1997). It was also concluded that a revision of previously published ESR ages using one-group transport for beta dosimetry will be needed. For cases where the U concentrations in enamel are generally low (less than a few ppm), previously published ESR ages on tooth enamel are systematically too young by 5–30%. 相似文献