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Investigation of the multi-elemental self-absorption mechanism and experimental optimization in laser-induced breakdown spectroscopy
摘要： The self-absorption effect reduces the accuracy of elements measurement in laser-induced breakdown spectroscopy (LIBS) experiments. In this paper, the mechanism of the self-absorption effect was studied. First, we established a plasma concentration distribution model and plasma dynamics model of the plasma expansion in three directions during LIBS based on physical laws. By coupling a plasma concentration distribution model with a self-absorption model, the LIBS self-absorption effect value model was obtained. Second, the models were applied in a numerical simulation to determine plasma spatial distribution characteristics during LIBS. The self-absorption effect values of spectral lines were calculated. Finally, experiments were conducted with an optical spectrometer to obtain the Na, K, and Al atomic emission spectra. On the theoretical plane, the Boltzmann plot method and the Stark broadening method were used to obtain the plasma characteristic parameters. The spectral line intensities of the Na, K and Al atom lines were obtained without and with microwave-assisted LIBS experiments for comparison. The experimental analysis showed that during the LIBS process, microwave assistance can enhance the emission spectroscopy intensity and inhibit or reduce the LIBS self-absorption effect. The experimental samples were in good agreement with those of theoretical simulation, indicating the effectiveness and practicability of the created LIBS self-absorption effect value model, which can improve the optimization of the LIBS process.
关键词： Self-absorption,LIBS,Numerical simulation,Spectral analysis,Material surface
更新于2025-09-23 15:19:57
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Rapid qualitative evaluation of velvet antler using laser-induced breakdown spectroscopy (LIBS)
摘要： The aim of this work is to study a rapid analysis method to evaluate velvet antler products qualitatively, using laser-induced breakdown spectroscopy (LIBS). We used principal component analysis to select feature lines of LIBS spectra of velvet antler, and built two partial least squares-discriminant analysis (PLS-DA) classification models to distinguish between inferior and good quality velvet antler by using the intensities of all lines and feature lines as input variables, respectively. The correct classification rates (CCRs) of these two models were both 100%. In order to test the robustness of the models, we used these two models to discriminate the samples not included in the training set to build the model, and the CCRs were 87.5% and 100%, respectively. The results demonstrated that combining LIBS with PLS-DA could evaluate the quality of velvet antler, and the robustness could be improved by using the intensities of feature lines as inputs.
关键词： qualitative evaluation,partial least squares-discriminant analysis (PLS-DA),velvet antler,principal component analysis (PCA),laser-induced breakdown spectroscopy (LIBS)
更新于2025-09-23 15:19:57
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[IEEE 2019 Workshop on Recent Advances in Photonics (WRAP) - Guwahati, India (2019.12.13-2019.12.14)] 2019 Workshop on Recent Advances in Photonics (WRAP) - Development of picosecond standoff libs system for the identification of the metals and alloys
摘要： We report the development and optimization of a standoff laser-induced breakdown spectroscopy (ST-LIBS) system for identification of metals and alloys. A simple convex lens and low-cost portable CCD spectrometer were utilized as collection system instead of conventional big telescope coupled to ICCD. Good signal to noise ratio has been achieved with minimum pulse energy of 2.5 mJ at a standoff distance of 6 m. This is the first report on picosecond ST-LIBS combined with compact detection system to the best of our knowledge. The developed system can work as a promising tool for process control and defense applications.
关键词： f-number,Standoff LIBS,Principal component analysis
更新于2025-09-23 15:19:57
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Spectral characteristic of laser-induced plasma in soil
摘要： The spectral characteristic of laser-induced plasma in soil was studied in this work, plasma under the condition of different time delays and irradiances. Moreover, the time evolution characteristics of plasma temperature and electron density were discussed. Within the time delay range of 0–5 μs, the spectral intensity of the characteristic lines of Si Ⅰ: 288.158 nm, Ti Ⅰ: 336.126 nm, Al Ⅰ: 394.400 nm and Fe Ⅰ: 438.354 nm of the four main elements in two kinds of national standard soil decayed exponentially with time. The average lifetime of the spectral lines was nearly 1.56 μs. Under the condition of different time delays, the spectral intensity of Pb Ⅰ: 405.78 nm in soil increased linearly with laser energy. However, the slope between the spectral intensity and laser energy decreased exponentially with the increase of time delay, from 4.91 to 0.99 during 0–5 μs. The plasma temperature was calculated by the Boltzmann plot method and the electron density was obtained by inversion of the full width at half maximum (FWHM) of the spectrum. The plasma temperature decreased from 8900 K to 7800 K and the electron density decreased from 1.5×1017 cm-3 to 7.8×1016 cm-3 in the range of 0–5 μs.
关键词： soil,time delay,electron density,laser energy,LIBS,plasma temperature
更新于2025-09-23 15:19:57
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Quantitative in situ mapping of elements in deep-sea hydrothermal vents using laser-induced breakdown spectroscopy and multivariate analysis
摘要： This study describes a method to quantify the chemical composition of deep-sea hydrothermal deposits in situ using laser-induced breakdown spectroscopy (LIBS). Partial least squares (PLS) regression analysis is applied to spectra obtained using a long laser pulse with a duration of 150 ns. The number of measurements needed to address the spatial heterogeneity of samples is determined through high-resolution mapping of the elemental distribution in rock samples. PLS applied to laboratory measured seawater-submerged samples achieved an average relative error (RE) of 25% for Cu, Pb, and Zn compared to benchmark concentration values in cross-validation and validation studies, where both the benchmark concentration values and LIBS spectral data are made available with this publication. The PLS model was applied to LIBS signals obtained in situ from hydrothermal deposits at 1000 m depth in the ocean. The results show that target inhomogeneity limits the accuracy of the surface LIBS measurements compared to benchmark values from bulk analysis of samples. Making multiple measurements with small position offsets at each location improves the accuracy of estimates compared to an equivalent number of measurements at a single position. Maps of element distribution generated using quantified in situ data demonstrate how chemical survey outputs can be generated by combining LIBS with multivariate analysis. This enables real-time chemical feedback during deep-sea operations and chemical surveys in situations or with platforms where sample recovery is not possible.
关键词： Multivariate analysis,Laser-induced breakdown spectroscopy (LIBS),Deep-sea explorations,In situ chemical analysis,Seafloor mineral resources,Partial least squares regression analysis
更新于2025-09-23 15:19:57
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Geographical authenticity evaluation of Mentha haplocalyx by LIBS coupled with multivariate analyses
摘要： Mentha haplocalyx (mint) is a significant traditional Chinese medicine (TCM) listed in the Catalogue of “Medicinal and Food Homology”, therefore, its geographical origins (GOs) are critical to the medicinal and food value. Laser-induced breakdown spectroscopy (LIBS) is an advanced analytical technique for GOs certification, due to the fast multi-elemental analysis requiring minimal sample pretreatment. In this study, LIBS data of sampled mint from five GOs were investigated by LIBS coupled with multivariate statistical analyses. The spectral data was analyzed by two chemometric algorithms, i.e. principal component analysis (PCA) and least squares support vector machines (LS-SVM). Specifically, the performance of LS-SVM with linear kernel and radial basis function (RBF) kernel was explored in sensitivity and robustness tests. Both LS-SVM algorithms exhibited excellent performance of classification in sensitive test and good performance (a little inferior) in robustness test. Generally, LS-SVM with linear kernel equally outperformed LS-SVM based on RBF kernel. The result indicated the potential for future applications in herbs and food, especially for in situ GOs applications of TCM authenticity rapidly.
关键词： laser-induced breakdown spectroscopy (LIBS),geographical origin,herb authenticity,least squares support vector machines,Mentha haplocalyx
更新于2025-09-23 15:19:57
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Laser induced breakdown spectroscopy application to reaction-diffusion studies in nuclear materials
摘要： We explore the possible use of Laser Induced Breakdown Spectroscopy (LIBS) to analyze active materials in hot cells or even inside nuclear reactors where high radiation levels prevent the use of conventional techniques. LIBS measurements of the reaction-diffusion process in alloys used in the nuclear industry were compared with standard techniques such as micrography, scanning electron microscopy, and energy dispersive X-rays spectroscopy. The LIBS capability to qualitatively detect the above process was established. Also, the average speed of the reaction-diffusion process was measured through a temperature-dependent effective parameter K.
关键词： Zirconium Alloys,LIBS,Nuclear Materials,Diffusion
更新于2025-09-23 15:19:57
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In situ chemical composition analysis of a tungsten-inert-gas austenitic stainless steel weld measured by laser-induced breakdown spectroscopy
摘要： The chemical composition of a weld metal determines the resulting solidification mode of stainless steel and the consequent weld metal quality. In this work tungsten inert gas (TIG) welding of EN grade 1.4435 austenitic stainless steel was monitored using laser-induced breakdown spectroscopy (LIBS) for the in situ measurement of chemical composition changes. This research aims to prototype a real-time chemical composition analysis system for welding applications and prove the feasibility of such quality control loop. LIBS was used to investigate in situ the monitoring of metal vaporization during TIG welding. We found Mn vapor formation above the weld pool and subsequent condensation of Mn on the weld metal surface using LIBS. Post-weld line scans were conducted by LIBS on various welds produced with different welding currents. Local changes of Ni and Mn were observed at higher welding currents. The results are in good agreement with the literature and proved that LIBS can be used in situ to inspect the TIG welding process.
关键词： LIBS,In situ measurement,Metal vapor,Welding,Austenitic stainless steel
更新于2025-09-23 15:19:57
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In-situ measurement of potassium release during biomass combustion using laser-induced breakdown spectroscopy: effect of silicate on potassium release
摘要： In this study, an improved calibration method for the in-situ measurement of potassium (K), concentration in the flame field was developed using laser induced breakdown spectroscopy (LIBS). The temporal behaviors of K release and particle temperature were recorded simultaneously during biomass combustion. During combustion of raw willow wood, the majority of K was released during ash-cooking stage, followed by char combustion stage, only a small amount of K was released during the initial devolatilization stage. The results indicated during devolatilization stage K was released due to the decomposition of organic K. Char- K was subsequently converted to K2CO3 and most K2CO3 was subsequently released during final ash-cooking stage. In the case of rice straw combustion, K was mainly released during the initial devolatilization stage, most likely as KCl. The transformation of char-K and the K-Si reaction forming K-silicates mainly occurred during char combustion stage, K was found to be released slowly from K-silciates during ash-cooking stage. The combustion of willow wood with different Si contents demonstrated that Si significantly inhibited the K release during both char combustion and ash-cooking stage.
关键词： release,LIBS,biomass,combustion,Potassium,silicate
更新于2025-09-23 15:19:57
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A hybrid random forest method fusing wavelet transform and variable importance for quantitative analysis of K in potassic salt ore using laser-induced breakdown spectroscopy
摘要： Potash mine is the main raw material for the production of agricultural fertilizers. In this research, random forest(RF) models fusing variable importance and wavelet transform were proposed to determine the K content in potassic salt ore. 53 potassic salts samples were analyzed, 37 of which were treated as calibration set. An original RF model was developed for the regression with optimized parameters ntree and mtry. The R2P (0.7399) and the modeling time (251.8s) of RF model were not satisfied. We first explored the effect of different variable importance(VI) thresholds on quantitative results. As the VI threshold was set to 0.090, the variable number of VIRF model was reduced from 27620 to 3355. There were no significant improvements for VIRF in other model performance parameters like RMSEP and R2P. Then wavelet transform was adopted to screen the input variables of the RF model (defined as WTRF). Their promotion ratios are 16% (R2P from 0.7399 to 0.8555), 38% (RMSEP from 0.1798 to 0.1106) and 62% (MRE from 0.2740 to 0.1032), 11% (MRSD from 0.0686 to 0.0613), respectively. As for modeling time, it was promoted by about three orders of magnitude. When using the variable importance for the WTRF model further (defined as WT-VIRF), because all the selected input variables filtering by wavelet transform contributed a lot to the quantitative results, therefore no more variable were got rid of, and then WT-VIRF model got the exact same result with WTRF model. All the results demonstrated shows that the RF model combining WT is a promising methodology for quantitative analysis of K content in potassic salt ore.
关键词： Wavelet Transform,Potash,LIBS,Variable Importance
更新于2025-09-23 15:19:57