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1.
In the course of this work, the possibility of the measurement of ambient dose equivalent H*(10) with the BeOSL dosimetry system was evaluated. Calculations for the energy response of the 2-element BeOSL dosimeter for irradiation with H*(10) were performed. The response doesn't fulfil the requirements of IEC 62387-1. Especially the response for photon energies of 60–100 keV is to low. It is possible to correct this under response using a modified BeOSL 2-element dosimeter and a linear algorithm. So the national requirements for a H*(10) dosimeter in Germany can be fulfilled. An incidence angle independent measurement is not possible because for several angles of incidences (>60°) the filters of the 2-element dosimeter doesn't shield the correct element. Another material which is more suitable for the H*(10) measurement was tested. So the doping of BeO with Lanthanum leads to an enhanced energy response for measurement of H*(10). Furthermore a higher OSL sensitivity was found for this material. Further tests on the influence of Lanthanum concentration on the dosimetric properties are necessary. 相似文献
2.
The widely known LiF TL detectors: LiF:Mg,Ti (MTS-N) and LiF:Mg,Cu,P (MCP-N), were investigated with respect to their OSL properties. It was found that both materials exhibit quite substantial OSL sensitivity. In particular, in the case of LiF:Mg,Cu,P this sensitivity was very high, significantly exceeding that of BeO, the standard OSL dosimetric material. LiF:Mg,Cu,P could be a very promising candidate for application in dosimetry, if not for the fading, which was found to be quite high, reaching nearly 80% loss of the signal within 60 h. The OSL signal intensity shows a correlation with the peak 2 of the TL glow curves indicating that the same trapping sites are responsible for both processes. Peak 2 of LiF:Mg,Ti shows a peculiar property, that blue light stimulation removes only about half of its initial intensity, disregarding the duration of stimulation. This suggests, that this peak may have a composite structure and originates from both light-sensitive and light-insensitive trapping centres. 相似文献
3.
Time Resolved Optically Stimulated Luminescence (TR-OSL) from BeO ceramics was investigated using blue (445 nm) and near-IR light (852 nm) for stimulation. Stimulation spectrum of the TR-OSL signal – as measured in the interval 700 to 420 nm- was observed to increase monotonically with the decreasing stimulation wavelength. In addition to the “fast” and “slow” components observed with blue light stimulation, IR stimulated TR-OSL spectra of irradiated BeO ceramics were observed to have two components with average lifetimes around ∼2.5 μs and ∼17 μs. Emission spectra of the both IR stimulated TR-OSL components were observed to have a broad emission band peaking around 330 nm. Thermal stability of the IR stimulated TR-OSL signal was studied by making preheating experiments in the range from 100 °C to 190 °C. It was observed that the IR stimulated OSL signal is stable up to ∼150 °C and decay afterwards. Radiation dose response of the IR stimulated luminescence signal was obtained in the range from 5 to 500 Gy. Both blue and IR stimulated TR-OSL signals grew up to 100 Gy and exhibited saturation for higher doses. Additionally, measurement temperature dependence of the components was also investigated and for the ∼2 μs component thermal assistance with activation energy around 0.16 eV was observed. It seems that the fast component of the blue stimulated TR-OSL component can be correlated to the ∼2 μs IR stimulated TR-OSL component. 相似文献
4.
Time-resolved OSL (TR-OSL) from natural zircon (ZrSiO4) minerals was investigated using 445 nm blue laser light for stimulation. Analyses of the TR-OSL spectra have showed that the decay is composed of two exponential components with lifetimes varying around ∼17 μs and around ∼110 μs respectively. The behaviour of these signal components, was examined under various sample treatments and experimental conditions. Preheating experiments showed that the OSL signal is stable up to temperatures ∼250 °C then becomes unstable. The dose response of the TR-OSL signal from zircon was determined in the range from 1 Gy to 1 kGy and observed to be increasing linearly. Practically, no effect of radiation dose on the lifetimes of signal components was observed. In addition, the effect of measurement temperature on the TR-OSL decay lifetimes was also investigated. Thermal quenching energies of the “fast” and the “slow” components were found to be very close to each other i.e. 0.18 and 0.24 eV respectively. 相似文献
5.
The automated Risø TL/OSL Reader Model DA-20, often used in dating and retrospective dosimetry, was examined for possible applications in thermoluminescent dosimetry related to radiation protection. The investigations revealed that performance of the DA-20 is comparable with that of the Harshaw 3500 manual reader, which was used as a reference instrument. All studied parameters, like stability, reproducibility, low-dose measuring capabilities, were at the same level or only somewhat inferior to those of Harshaw 3500. In particular, using the highly-sensitive LiF:Mg,Cu,P dosimeters, it is possible to measure doses at the microgray level.The DA-20 reader possesses built-in alpha and beta sources, which cause an increased radiation background. At positions just under the closed sources the dose-rate rises to about 50 μGy/h. When the 90Sr/90Y source is open a quite high dose-rate of 100 mGy/h was measured at the position adjacent to the one being irradiated. Additionally the TLD response to the background radiation significantly depends on the TLD type (atomic number), as the radiation leaking through shielding is composed of low-energy photons. The dose-rate under the closed 241Am source was over 10 times higher, when measured with CaF2 dosimeters, than with LiF.In spite of these problems, the DA-20 reader due to its good stability, reproducibility and sensitivity, combined with such obvious benefits as a 48-dosimeter carousel, temperatures up to 700 °C and full automatics of measurements control, encourages the opinion that the DA-20 Risø reader can be successfully used in practical dosimetric measurements. 相似文献
6.
Time-Resolved Optically Stimulated Luminescence (TR-OSL) from BeO ceramics was investigated using a blue laser (445 nm) as stimulation light source. It was observed that, at relatively low dose levels (up to ∼25 Gy) the TR-OSL decay curve can be approximated with a single exponential decay function with a lifetime of ∼26 μs at room temperature. Beyond 25 Gy a new decay component with a lifetime of a ∼2 μs was observed in addition to the ∼26 μs component. Thermal stability, radiation dose response, optical bleaching, measurement temperature dependence of the components of the TR-OSL signal were investigated in detail. As result of these studies, a new OSL component which becomes unstable after 150 °C was observed. OSL decay rate of this component was found to be higher than the one which becomes unstable after 300 °C. In order to obtain information about the temperature dependence of the luminescence efficiency, luminescence emission lifetime was determined in the temperature range from 30 to 130 °C with 10 °C steps. Using the temperature dependence of the lifetime, thermal quenching energy was determined to be around 0.56 eV for the 26 μs component. For the ∼2 μs component an enhancement in the component intensity was observed pointing to a thermally assisted process with activation energy of 0.15 eV. 相似文献
7.
Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the thermoluminescence (TL) and optically stimulated luminescence (OSL) processes in BeO phosphor. Two defect centres were identified in irradiated BeO phosphor by ESR measurements, which were carried out at room temperature and these were assigned to an O− ion and Al2+ centre. The O− ion (hole centre) correlates with the main 190 °C TL peak. The Al2+ centre (electron centre), which acts as a recombination centre, also correlates to the 190 °C TL peak. A third centre, observed during thermal annealing studies, is assigned to an O− ion and is related to the high temperature TL at 317 °C. This centre also appears to be responsible for the observed OSL process in BeO phosphor. 相似文献
8.
Isothermal heating is commonly used in luminescence dosimetry and trap parameter studies. It is often observed that the isothermal luminescence signal has a peak shape instead of a monotonous decay form. We provide here evidence that this peak shape in quartz may equally result from a ‘thermal lag’ problem in contrast to the earlier propositions of non first-order kinetics. Temperature modelling suggests that the peak-shaped signal contains elements of both the ramped — and isothermal — thermoluminescence (TL). The modelled changes in the peak movement as a function of isothermal temperature and the ramp-rate show an excellent agreement with those obtained experimentally. This understanding of thermal lag is extended to optically stimulated luminescence (OSL) measurements for which the effects of isothermal TL contamination and changing thermal assistance during thermal equilibration are discussed. Appropriate methods are suggested to identify thermal lag on the basis of the peak structure, and to circumvent this effect in isothermal methods. 相似文献
9.
10.
Abstract Two types of bombardment experiments were performed. A first series on metallic spheres, examined by replicas, and a second series on thinned crystals, examined by transmission electron microscopy. The observations lead us to propose a model for the formation of the surface microrelief. This model enables one to correlate the observation of regular dislocation networks, due to the segregation in perfect loops of the induced point-defects, to the formation of the relief structure by a preferential sputtering mechanism. En s'appuyant sur les résultats obtenus à partir de deux types d'expériences de bombardement, les unes sur des sphères métalliques examinées par répliques, les autres sur des cristaux amincis examinés par transmission, un modéle est proposé pour la formation du microrelief de surface. Ce modèle permet de relier l'observation de résaux réguliers de dislocations dus à la ségrégation des défauts induits en boucles parfaites, à la formation du relief par un mécanisme de pulvérisation différencié. 相似文献
11.
In this work, three design configurations of a sonoreactor are considered under various operating conditions, and the acoustic characteristics during water sonication are investigated while using an immersed-type ultrasonic flat transducer probe in a sonoreactor model. Numerical models are also developed to simulate the sonication process, and they are successfully validated and compared with available data in the literature. Several sets of numerical investigations are conducted using the finite-element method and solved by the computational acoustics module in the COMSOL Multiphysics. The effects of the acoustical and geometrical parameters are investigated, analyzed, and reported, including the ultrasonic frequency, acoustic intensity, and scaling-up the reactor. The present study includes a parametric investigation examining the change of the ultrasonic frequency, intensity, and probe immersion depth on the performance. The results of the parametric study show that the highest cavitation energy corresponds to the maximum magnitude of negative pressure that takes place in the range of 60–80 kHz. The cavitation energy analyses are conducted under the conditions of 20 kHz of frequency and at 36 W input power. It is found that the cavitation energy of 15.87 W could produce 2.98 × 10−10 mol/J of sonochemical efficiency. In addition, the effect of altering the transducer probe depth changes the acoustic pressure field insignificantly. Furthermore, a recommendation is made to improve the sonochemical efficiency by introducing more considerable ultrasound input power while operating the sonoreactor at an ultrasonic frequency lower than 60 kHz. The results presented in this paper provide a comprehensive assessment of different sonoreactors and the feasibility of scaling-up their production rate. 相似文献
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13.
Small size (25 nm) Li2B4O7 nanoparticles doped with different concentrations of Cu, Ag and co-doped with Cu, Ag were prepared by solid state sintering at 700 °C. The crystalline phase and particle sizes analysis were carried out by XRD and TEM. FTIR study reveals the formation of vibrational bonds at 1600–1200 cm−1, 1500–700 cm−1, 950–870 cm−1 and 870–415 cm−1. The kinetic parameters of the TL glow curves were evaluated using CGCD procedure in R-software. The CW-OSL decay curves were fitted with third order exponential decay curves and photoionization cross sections of each component were evaluated. The lifetime of the main TL dosimetric peak were also calculated to check the stability of the signal. Dose responses of the synthesized Li2B4O7 nanoparticles for both the TL and CW-OSL were studied in the range of 0.02 mGy to50 Gy and found to be linear upto this range. Fading of the CW-OSL decay curves were also studied. The MDD of the synthesized samples were also calculated and observed to be 15 μGy. 相似文献
14.
《核聚变与等离子体物理》2010,29(1)
对ITER中子通量监测器(NFM)建立了简化模型并进行了计算分析。利用MCNP程序模拟计算了具有不同慢化剂材料/类型的NFM的探测效率能量响应和时间响应;通过对结果的分析确定了不同NFM上所使用的慢化剂种类及其用量;同时给出了对ITER NFM的初步物理认识。 相似文献
15.
For the first time the feasibility of using beryllium oxide (BeO) ceramics as a fibre-coupled radioluminescent dosimeter is investigated. BeO ceramic exhibits both radioluminescence (RL) and optically stimulated luminescence (OSL), and has the potential to be a near tissue equivalent alternative to Al2O3:C. A BeO fibre-coupled radioluminescence dosimeter is demonstrated and characterised for 6 MV X-rays and superficial X-ray energies, 150 kVp and 120 kVp. Based on the results, we demonstrate the capability of the RL BeO FOD for accurate and reproducible dose measurements with a linear dose rate and dose response. It has also been found that the percentage depth dose curves for 6 MV agreed with ion chamber measurements to within 2%, except in the build up region. For the 150 kVp and 120 kVp photon beams, the depth dose measurements agreed with ion chamber measurements to within 2.5% and 4%, respectively. 相似文献
16.
Radiochromic film dosimetry is a promising technique, but at this time there are some artefacts, including non-uniformity, energy dependence and scanner artefacts. Accurate dosimetry with radiochromic films requires characterizing the film as well as the scanning and analysis procedures. In this work, the performance of the EBT3 films in combination with the EPSON Dual Lens Perfection V700 scanner for dose distribution measurements in stereotactic radiotherapy has been evaluated. It has been shown that it was necessary to perform 20 blank scans to obtain the stability of the scanner. In order to reduce the uncertainties due to the non-uniformity of the scan field, it was then decided to use the 12 × 12 cm2 central part of the scanner bed. Regarding EBT3 films, intra-sheet and inter-sheet uniformity of unexposed EBT3 films in terms of pixel value has been found to be respectively 0.27% (1 SD) and 0.15% (1 SD). No significant energy dependence has been observed above 30 keV and no angular dependence has been found. 相似文献
17.
采用第一性原理方法计算了BeO在零温时的高压相变和三种结构在零温零压时的声子谱.相变的计算表明,在122GPa左右的压力下BeO会发生从纤锌矿(B4)结构到氯化钠(B1)结构的相变,而闪锌矿(B3)结构在零温零压下是一种可能的亚稳态结构.采用冷声子方法计算了这三种结构的BeO在零温零压下的声子谱.计算结果表明:B1结构在零温零压下是一种不稳定的结构;尽管B4结构和B3结构具有明显的相似性,仍然可以通过声子谱来很好的区分.最后根据准简谐近似理论计算得到了BeO的高温高压相图. 相似文献
18.
α-Al2O3单晶的热释光和光释光特性 总被引：3，自引：0，他引：3
研究了纯α-Al2O3单晶的热释光发光曲线和三维发光谱,以及光释光衰变曲线,对它们的发光机理和剂量学特性进行了分析和讨论.实验观察到α-Al2O3单晶β射线照射后立即测量的热释光发光曲线,有峰温为76℃和207℃两个发光峰.经γ射线照射数小时后测量的三维发光谱,只有峰温207℃波长为416 nm发光峰,它与α-Al2O3:C晶体的发光波长基本相同,是受热激发到导带的电子与F<关键词：2O3')\" href=\"#\">α-Al2O3三维发光谱TL/OSL剂量响应 相似文献
19.
This study demonstrates the energy response of thermoluminescent (TL) detectors based on YAlO3:Mn crystals. Experimental results of the relative sensitivity of YAlO3:Mn2+ detectors to various kinds of photon radiation (from 60Со, 131Cs, 192Ir, and 137Cs isotopes; X-ray from 220 kVp; and photon radiation from a linear accelerator (LINAC) at 5, 10, and 15 MV) agree with the theoretical energy response from Monte Carlo simulation. In addition to YAlO3 (YAP), energy response was calculated for other yttrium-containing oxides such as Y2O3, Y3Al5O12 (YAG), and Y4Al2O9 (YAM). A possibility of filtering (modification) of the energy response of high atomic number (Z) materials by the metallic filters was shown. 相似文献
20.
The motivation of this work was to produce crystals of CaSO4 doped with an unusual combination of RE elements such as terbium (Tb) and europium (Eu) in different concentrations, and analyze its thermoluminescent (TL) properties. The crystals were produced by the slow evaporation route using calcium carbonate (CaCO3) as precursor, and incorporating the dopants (Tb2O3 and Eu2O3) in a solution of sulfuric acid, that is evaporated and collected again, leaving just CaSO4:Tb,Eu crystal powder. The terbium and europium ions were incorporated in concentration ratios of 1:1, 2:1 and 5:1 (weight proportions). X-ray diffraction analyses showed that samples of doped CaSO4 exhibit only a single phase corresponding to the crystal structure of anhydrite. The radioluminescence confirmed the presence of Tb3+ and Eu2+ in the crystal matrix. The CaSO4:Tb,Eu crystal powders showed TL emission glow curves with three peaks centered around 170 °C, 270 °C and 340 °C, after irradiation with a 90Sr/90Y source. Thermoluminescent (TL) characteristics such as linearity, reproducibility and fading were evaluated. Samples produced with concentration ratio of 2:1 of Tb and Eu showed the highest TL intensity. The produced CaSO4:Tb,Eu samples present TL properties useful for dosimetric purposes. 相似文献