Leosson, KristjanPadamata, Sai KrishnaMeirbekova, RauanSaevarsdottir, Gudrun...
5页
查看更多>>摘要：We report Ti concentration measurements in dilute Al-Ti alloys, acquired from direct analysis of the molten metal by laser-induced breakdown spectroscopy (LIBS). The LIBS analysis showed approximately constant Ti concentrations at melt temperatures above the liquidus, while at lower temperatures the measured concentration followed the L/(L + Al3Ti) liquidus of the phase diagram, confirming that the LIBS measurement accurately detects the dissolved Ti concentration in the melt. The LIBS measurements furthermore demonstrated that the Al3Ti phase forms or dissolves within minutes when the melt temperature is decreased or increased, respectively. For the first time, the liquidus line at low Ti concentrations in the Al-Ti phase diagram has thus been mapped using LIBS analysis instead of the more conventional but time-consuming thermal analysis methods. We conclude that LIBS analysis of molten metal offers a unique opportunity to monitor accurately the chemical composition of the liquid phase and reveal the formation of solid precipitates in real time.& nbsp;
查看更多>>摘要：Radioactive particles, so-called hot particles, are of great importance in the risk assessment of environmental pollution and human health hazards. Since most of these particles are only a couple of micrometers in size and thus have correspondingly small atomic inventory, information on origin and composition is difficult to obtain. Many analytical methods do not give insight into isotopic details or require the complete use up of the particle. Resonant laser secondary neutral mass spectrometry (rl-SNMS) has been proven to be a well-suited method for quasi-non-destructive analysis of trace elements. The technique provides high suppression of isobaric interferences and high spatial resolution without necessitating extensive chemical preparation. To measure multiple elements, it is often necessary to switch between laser excitation schemes, requiring elaborate adaptation of the laser setup. Here we present a novel rL-SNMS system capable of multi-element measurements in short succession without any manual adjustment to the laser system. For demonstration, ten micrometer sized hot particles from the Chernobyl Exclusion Zone are analyzed and the obtained isotopic ratios of uranium, plutonium and americium are discussed.
Hull, GregoryMcNaghten, Edward D.Sharrad, Clint A.Martin, Philip A....
11页
查看更多>>摘要：Laser-induced breakdown spectroscopy (LIBS) can provide immediate in situ elemental characterisation of a sample from a stand-off distance with no sample preparation for bulk, minor and trace species. These attributes suggest the technique could be applied to many processes in the nuclear industry. However, at present, LIBS cannot quickly and easily be used to determine the isotopic composition of a sample, which limits its potential. We report the development of a system comprising laser ablation-tuneable diode laser absorption spectroscopy (LA-TDLAS) and LIBS which can maintain the benefits of traditional LIBS and enable isotopic analysis of certain elements, including lithium and uranium. In this feasibility study, we used this approach to analyse a uranium metal wire sample under ambient conditions of pressure and temperature. Simultaneously, from the same laser produced plasma, the U-235 isotope fraction was determined with LA-TDLAS while the plasma emission was used to obtain the electron density of the plasma using Stark broadening of uranium and sodium emission lines. The accuracy of the isotopic analysis performed with LA-TDLAS was limited by the noise of the absorption spectra and low concentration of the minor U-235 isotope (0.7%). The limit of detection was estimated to be 1.5 wt%. Using the Doppler broadening of absorption lineshapes, the plasma temperature was calculated to drop from 25,000 K to 2000 K during the plasma lifetime. The electron density rapidly decreased from 6 x 10(16) cm(-3) immediately after laser ablation to around 3 x 10(16) cm(-3) after a few mu s. The combination of LIBS and LA-TDLAS opens the possibility of rapid elemental and isotopic analysis which would be useful across the nuclear fuel cycle. Furthermore, the LA-TDLAS technique could be further developed for a portable measuring instrument for nu-clear forensics applications.& nbsp;
查看更多>>摘要：Laser resonance ionization spectroscopy of atomic thulium (Tm) has been performed at TRIUMF's off-line laser ion source test stand with a system of pulsed titanium sapphire (Ti:Sa) lasers. Automated continuous laser frequency scans across Rydberg states and autoionizing (AI) states were carried out using a pulsed, frequency doubled grating-tuned Ti:Sa laser. A combined analysis of the convergence limits resulting from odd-parity Rydberg series and AI Rydberg series improved the value for the ionization potential to 49,880.57(6)stat(4)sys cm-1, one order of magnitude more precise than the currently accepted value of 49,879.8(5) cm-1. An efficient resonance ionization scheme has been deduced from the photoionization spectra, and applied to online radioactive Tm isotope beam delivery at ISAC-TRIUMF. The ionization scheme will be useful for the extraction of Tm isotopes for nuclear medicine. The production yields of 153-165Tm were measured by evaluating the characteristic gamma lines of the Tm isotopes at the ISAC yield station.
查看更多>>摘要：Spectral features have a crucial influence on the qualitative analysis performance of portable laser-induced breakdown spectroscopy (LIBS) technology. To solve the problem of poor classification performance caused by the weak characterization ability of conventional single feature forms such as spectral intensity feature, a classification method based on spectral feature augmentation (SFA) was proposed. It was realized through the mining, extraction and fusion for 6 different types of features including spectral intensity (SI), spectral peak area (SPA), full width at half maximum (FWHM), standard deviation (SD), signal-to-background ratio (SBR), and signal-to-noise ratio (SNR). Using this method, the classification accuracy of 75 sedimentary rock samples was increased from 87.2% of the conventional spectral intensity method to 95.5% of the SFA method. In addition, the classification experiment of 24 metallic mineral samples was used to test its generalization ability, and their classification accuracy was increased from 77.5% to 91.7%. The results indicate that the SFA method can improve the characterization ability of feature vectors and the classification model's accuracy by mining more effective information from a limited number of spectra and then successfully integrating and utilizing it. This method provides a new approach for improving the qualitative analysis performance of portable LIBS
查看更多>>摘要：Determination of trace elemental concentrations in presence of heavy Z matrix like uranium using X-Ray Fluorescence (XRF) based technique requires separation of major matrix from the sample matrix. This separation process is laborious and also produces large amount of organic waste. To counter this problem we have developed a Micro-XRF based technique for the trace elemental analysis in uranium matrix without applying any matrix separation steps. The main challenge of trace elemental analysis in presence of heavy matrix like uranium is severe matrix effect which deteriorates the detection limit as well as the analytical result. In order to assess the matrix tolerance for the direct trace elemental analysis in uranium by X-Ray Fluorescence technique, a detailed study has been conducted to observe the effect of uranium matrix on the analytical results like detection limits or recovery rate etc in the present paper. Based on the detail studies, a limiting concentration for uranium as major matrix has been optimized, up to which matrix effect can be tolerable for trace elemental analysis without further matrix separation. However if the matrix concentration goes beyond that limit, the sample has to be diluted to maintain the uranium matrix concentration below that limit. The presently developed methodology has been validated by determining trace elemental concentration in real natural uranium samples down to few hundred ng/mL concentration level. The methodology reported in this work is simple, cost-effective and less time consuming, with detection limits comparable to other well established trace analytical methods. Moreover it is having an added advantage of avoiding the complex matrix separation steps up to a certain level of matrix concentration.
Maity, U. K.Manoravi, P.Joseph, M.Sivaraman, N....
6页
查看更多>>摘要：Quantitative analysis of lanthanides (Ln's) in actinides matrix in aqueous medium using laser-induced breakdown spectroscopy (LIBS) is presented in this article. Mixture of lighter rare earth elements (REEs) such as La, Ce, Pr, Nd and Sm in U matrix is analysed. Results on identifying non-overlapping peaks, calibration plot, detection limit, deviation from the true values, and precision are discussed. The data obtained is compared with reported results for similar kind of systems. The method also describes the potential for determination of atom percentage fission of a nuclear fuel using LIBS. An in-housed designed sample cell is adopted for analysis of liquid sample which requires minimal quantity (<1 mL). Minimum sample quantity is advantageous for analysis of highly radioactive irradiated nuclear sample because of lesser radiation exposure to the analyst.
Pacer, Emily J.Palmer, Christopher D.Parsons, Patrick J.
7页
查看更多>>摘要：Lead is ubiquitous in the environment and exposure can have adverse health effects even at low concentrations, particularly in young children. Blood Pb levels are the best indicator of recent Pb exposure. The Centers for Disease Control and Prevention (CDC) recently lowered the blood Pb reference value from 5 mu g/dL to 3.5 mu g/dL, based on data calculated from the 97.5th percentile of children 1-5 years old in the National Health and Nutrition Examination Survey (NHANES). The established method for determining Pb in blood by GFAAS has an estimated detection limit (LOD) of approximate to 1 mu g/dL. This presents an analytical challenge for its clinical use in the US, given that the current population mean blood Pb level is 0.82 mu g/dL. Accuracy and precision may be insufficient to quantitate low blood Pb levels in the 1-5 mu g/dL range, which is essential now that the CDC blood Pb reference value is 3.5 mu g/dL. The original GFAAS method for blood Pb published in 1993 has been significantly improved to achieve a lower LOD of 0.2 mu g/dL, with the ability to quantitate blood Pb levels down to 1 mu g/dL. This method is fit for the purpose of detecting blood Pb levels currently, with excellent accuracy and precision in the 1-5 mu g/dL range. Results from analyzing SRMs, PT materials and human blood samples were in good agreement between two different GFAAS platforms, as well as with results obtained by ICP-MS. The improvements provide evidence of an GFAAS method capable of achieving lower LODs with improved accuracy and precision at lower blood Pb levels, which can support the lower blood Pb reference value for children at 3.5 mu g/dL.
Fernandez-Menendez, Luis JavierMendez-Lopez, CristinaAbad, CarlosFandino, Jonatan...
9页
查看更多>>摘要：The entire process involving the determination of Cl by molecular emission detection in Laser-Induced Breakdown Spectroscopy (LIBS) is thoroughly studied in this paper. This critical evaluation considers how spectra are normalized, how interferences from other molecular species signals are removed, and how signal integration is applied. Moreover, a data treatment protocol is proposed to achieve reliable and accurate Cl determination from the CaCl molecular spectral signal, not requiring the use of more complex numerical approaches. Calcium chloride dihydrate (CaCl2 center dot 2H(2)O) and high purity anhydrite samples (CaSO4) are used to optimize the acquisition conditions and data treatment of CaCl emission signal. Using the developed protocol, calibration curves for Cl, covering the concentration range from 0 mu g/g to 60,000 mu g/g of Cl, are successfully achieved. Finally, the suitability of the proposed methodology for Cl determination is successfully applied in industrial gypsum waste samples, where the results obtained by LIBS are validated using high-resolution molecular absorption spectroscopy (HR-CS-MAS) and potentiometric titration.
查看更多>>摘要：Knowledge of electron temperature and electron number density of laser-induced plasma (LIP) is needed for both fundamental and applied researches. Typically, these parameters are derived from plasma emission spectra. It can cause uncertainties due to plasma inhomogeneity and self-absorption of emission lines. Another approach for diagnostics of LIP supposes registration and further analysis of Thomson scattering (TS) spectra. However, it is also a challenging way due to high level of spectral interferences (plasma emission, Rayleigh and Mie scatterings) from such a low-temperature plasma and low signal-to-noise ratio. The present paper evaluates the possibility of preprocessing of Thomson scattering spectra by wavelet denoising and suggests the approach of LIP diagnostics based on TS spectra. We used numerical simulations to select wavelets appropriate for retrieving TS signal from noisy spectra. The results indicate that wavelet denoising outperforms FFT filtration and provides high-quality results down to extremely small values of signal-to-noise ratio. Also, it was shown that wavelets efficiency varies for different values of TS parameter alpha, but some of them with "Sym 6" as the best representative are more universal that was proved by processing of experimental spectra.We describe two approaches of plasma parameters determination by numerical fitting of electron features of TS with Salpeter function or by fitting them with Lorentzian profile with further use of calculated nomograms. The first approach can successfully work with TS spectra in the absence of intense Rayleigh scattering. Nomograms approach demonstrated reliable results even in the presence of strong spectral interferences. Therefore, we consider wavelet denoising (Sym 6, Rbio1.3 and Bior 2.2) combined with nomograms approach for parameters calculation to be the most reliable and robust way of LIP diagnostics by TS.
NSTL
Elsevier