Laser-induced Breakdown Spectroscopy Instrument Research Articles

Feasibility of a Low-Power, Low-Resolution Laser-Induced Breakdown Spectroscopy Instrument for Analysis of Nickel Alloys: Quantification of the Major Alloying Elements and Classification.

A simple cost-effective laser-induced breakdown spectroscopy (LIBS) instrument was used for quantification of major elements in several nickel alloys and also sorting them. A compact low-power diode-pumped solid-state laser and a miniature low-resolution spectrometer were assembled for the LIBS instrument. Material properties of the nickel alloys depend mainly on the composition of the major elements, Ni, Cr, and Fe, ranging from a few to ∼60 wt%. The emission peaks at 547.7 nm, 520.4 nm, and 438.1 nm for Ni, Cr, and Fe, respectively, were chosen for this analysis. The analytical performance was found to be enough for the quantification of Ni, Cr, and Fe in the nickel alloys. Limits of detection and accuracy were estimated to be a few weight percent (wt%) and measurement precisions were less than 10% in terms of relative standard deviation. The calibration performance of this intensity-based method was compared with that of the "ratio method" which is used in conventional optical emission spectroscopy analyses. The comparison indicates that the intensity-based method is more appropriate with the low-performance LIBS instrument that detects emission peaks of only a few major elements. Also, multivariate modeling of the six different nickel alloy samples based on the emission peak intensities of Ni, Cr, and Fe was performed using k-nearest neighbors (KNN) and linear discriminant analysis (LDA). The KNN and ordinary LDA models showed 95.0% and 98.3% classification correctness for the separate test data set, respectively. To improve classification performance further, the two-step LDA model was trained. In this approach, the two closest sample classes responsible for the decrease in the classification correctness were separately modeled in the second step to exploit their difference effectively. The two-step LDA model showed 100% correctness in classifying the test objects. Our results indicate that such a low-performance LIBS instrument can be effectively utilized for quantitative analysis of the major elements in the nickel alloys and their rapid identification or sorting in combination with an appropriate multivariate modeling algorithm.

Accurate Quantitative Analysis of LIBS With Image Form Spectra by Using a Hybrid Deep Learning Model of a Convolutional Block Attention Module-Convolutional Neural Network-Long Short-Term Memory

With the development of miniaturized Laser-induced breakdown spectroscopy (LIBS) instruments, the desire for accuracy and stability of quantitative analysis of portable LIBS systems is growing. In this research, a hybrid deep learning model of a convolutional block attention module combined with a convolutional neural network and a long short-term memory (CBAM-CNN-LSTM) was for the first time used for quantitative analysis in a LIBS system with a portable spectrometer. Among them, the spectra collected by LIBS were in the form of the image, the CNN module was responsible for feature extraction of image spectra, mining deep features through the CBAM, and the simultaneous accurate quantitative analysis of Ca, Mg, Na and Ba was realized by the LSTM module. Meanwhile, a linear regression (LR), a CNN and a CNN-LSTM model were compared to the CBAM-CNN-LSTM model. The results showed that the performance of this model was much better than the LR model. More importantly, compared to CNN and CNN-LSTM, the average relative error of CBAM-CNN-LSTM was reduced by 80.5% and 68.1%, the average root mean square error was reduced by 56.7% and 53.4%, and the average stability was increased by 62.3% and 58.8%, respectively. In addition, the feature visualization results of CNN-LSTM and CBAM-CNN-LSTM displayed that CBAM can more effectively extract the features of characteristic peaks of corresponding elements and suppress the irrelative features. It indicated that the model can achieve an accurate and stable quantitative analysis of LIBS, which has the potential to be applied in the in-site analysis.

Generation and evolution of laser-induced shock waves under martian atmospheric conditions

SuperCam on NASA's Mars 2020 mission is the first laser-induced breakdown spectroscopy (LIBS) instrument on Mars that also employs a microphone to help with the evaluation of the LIBS spectra. When a LIBS measurement is performed in an atmosphere, an acoustic signal is emitted that can be recorded and used, for example, as a normalization standard to help in the interpretation of spectral data. The investigation of this pressure wave in Martian atmospheric conditions is important to better understand the relation between the acoustic signals and the LIBS spectra that are measured by SuperCam. However, the mechanisms involved in the generation of the pressure wave in Martian atmospheric conditions have not been studied in detail yet. To improve our understanding of how the acoustic signal is generated and how it can be used to aid in the analysis of the spectroscopic data, we developed an experimental setup combining different experimental methods to study the pressure waves generated during LIBS measurements in a simulated Martian atmosphere. It incorporates a schlieren imaging system for shock wave analysis, a plasma imaging setup for spatially and temporally resolved plasma analysis and a microphone to study the acoustic signal generated by the shock wave. The schlieren system is used to investigate the shock wave's density structure and expansion dynamics. The system was designed to record schlieren images in low-pressure Mars-analogue atmosphere with a high temporal resolution. We present first measurements including schlieren images of the laser-induced shock wave expanding from an iron target in a simulated Martian atmosphere. The measurements confirm numerical simulations of the density structure of laser-induced shock waves for the first time. Furthermore, we find that the Taylor-Sedov model gives a good estimate of the shock wave dynamics up until sonic speeds, when a linear model is appropriate. By comparing the dynamics of the shock wave to the expansion of the plasma, we find that the shock wave decouples from the luminous plasma between 400 ns and 500 ns after plasma ignition. We demonstrate the capabilities of this new setup by giving a detailed description of how the acoustic signal is generated from the expanding plasma. In future studies, the presented setup will be used to investigate the influence of material properties and experimental parameters on the generation of the shock wave and the acoustic signal to support the analysis of SuperCam measurements on Mars.

VOILA on the LUVMI-X Rover: Laser-Induced Breakdown Spectroscopy for the Detection of Volatiles at the Lunar South Pole

The project Lunar Volatiles Mobile Instrumentation-Extended (LUVMI-X) developed an initial system design as well as payload and mobility breadboards for a small, lightweight rover dedicated for in situ exploration of the lunar south pole. One of the proposed payloads is the Volatiles Identification by Laser Analysis instrument (VOILA), which uses laser-induced breakdown spectroscopy (LIBS) to analyze the elemental composition of the lunar surface with an emphasis on sampling regolith and the detection of hydrogen for the inference of the presence of water. It is designed to analyze targets in front of the rover at variable focus between 300 mm and 500 mm. The spectrometer covers the wavelength range from 350 nm to 790 nm, which includes the hydrogen line at 656.3 nm as well as spectral lines of most major rock-forming elements. We report here the scientific input that fed into the concept and design of the VOILA instrument configuration for the LUVMI-X rover. Moreover, we present the measurements performed with the breadboard laboratory setup for VOILA at DLR Berlin that focused on verifying the performance of the designed LIBS instrument in particular for the detection and quantification of hydrogen and other major rock forming elements in the context of in situ lunar surface analysis.

Quantitative laser-induced breakdown spectroscopy mapping of centerline segregation via optical emissions of Mn and Cr in steel wire rod products

A steel wire rod is one of the cast steel products used for springs to absorb repeated shocks, particularly in harsh conditions. Quality assessment of steel wire rods is critically important to prevent unwanted breakage during their lifetime. However, centerline segregation is the most common cause of weakened steel wire rods. Currently, centerline segregation is monitored using an optical microscope and an electron probe microanalyzer (EPMA). Herein, we demonstrate quantitative concentration mapping of Mn and Cr, the representative alloying elements, in steel wire rods using laser-induced breakdown spectroscopy (LIBS) as an alternative centerline segregation monitoring methodology. Sensitivity, detection limit, precision, and spatial resolution were found to be enough to observe centerline segregation. Concentration maps obtained by LIBS were very similar to those from EPMA. Microscopic matrix changes due to segregation were also identified. The resulting decrease in plasma temperatures was rationalized by formation of metal carbides that hardened local segregated areas. Considering the rapid multi-elemental mapping capability of LIBS in open air, LIBS is suggested as a practical alternative to optical microscope limited to carbon mapping and EPMA that needs high-vacuum equipment for screening faulty steel wire rod products. The centerline segregation of Mn and Cr in steel wire rods are rapidly monitored by laser-induced breakdown spectroscopy mapping. • A LIBS instrument for rapid elemental mapping for steel wire rods was developed • Centerline segregation of Mn and Cr was well observed by the LIBS instrument • Microscopic matrix changes due to the centerline segregation were identified and rationalized • LIBS outperforms optical microscopy in terms of simplicity in sample preparation and multiple element mapping for monitoring centerline segregation • LIBS is faster and more cost-effective than EPMA for monitoring centerline segregation

Application of elastic net in quantitative analysis of major elements using Martian laser-induced breakdown spectroscopy datasets

Multiple sets of laser-induced breakdown spectroscopy (LIBS) instruments, including ChemCam (Curiosity), SuperCam (Perseverance), and the Mars Surface Composition Detector (MarSCoDe, Zhurong), are working currently on the surface of Mars, a booming scene of LIBS technology application to planetary exploration. One of the primary challenges faced by those LIBS instruments is accurate and quantitative chemical composition determination of unexplored geological targets. Elastic net is a linear regression model that combines ridge regression and lasso model, which inherits the sparseness of lasso and the stability of ridge. In this work, we investigated the spectral features selected by elastic net model, the model performance and application to over 23,000 LIBS points. Selected features exhibit significant emission lines that are attributed to a certain single element and a few lines attributed to other related elements. These features enhance the interpretability of the model and weaken the matrix effect in LIBS quantitative analysis. In comparison, the results of elastic net are comparable and may be slightly better in some cases than other common linear regression models. For igneous calibration targets (norite, picrite, and shergottite), the predictions of elastic net are closer to the values measured in Earth laboratory than the final multivariate oxide composition values predicted by ChemCam team. Finally, we predicted the oxide abundances of 8 major elements from Mars LIBS spectra of over 23,000 points using elastic net. The predicted values of the elastic net models are highly correlated with those from the ChemCam team model. These results indicate that elastic net is viable for quantitative analysis Mars LIBS spectra. We propose that elastic net is an important candidate model for the quantitative analysis of the Zhurong MarSCoDe LIBS spectra.

Model transfer method based on piecewise direct standardization in laser-induced-breakdown spectroscopy.

A large number of certified samples are usually required to build models in the quantitative analysis of complicated matrices in laser-induced-breakdown spectroscopy (LIBS). Because of differences among instruments, including excitation and collection efficiencies, a quantitative model made on one instrument is difficult to apply directly to other instruments. Each instrument requires a large number of samples to model, which is very labor intensive and will hinder the rapid application of the LIBS technique. To eliminate the differences in spectral data from different instruments and reduce the cost of building new models, a piecewise direct standardization method combined with partial least squares (PLS_PDS) is studied in this work. Two portable LIBS instruments with the same configuration are used to obtain spectral data, one of which is called a master instrument because its calibration model is directly built on a large number of labeled samples, and the other of which is called a slave instrument because its model is obtained from the master instrument. The PLS_PDS method is used to build a transfer function of spectra between the master instrument and slave instrument to reduce the spectral difference between two instruments, and thus one calibration model can adapt to different instruments. Results show that for multiple elemental analyses of aluminium alloy samples, the number of samples required for slave modeling was reduced from 51 to 14 after model transferring by PLS_PDS, and the quantitative performance of the slave instrument was close to that of the master instrument. Therefore, the model transfer method can obviously reduce the sample number of building models for slave instruments, and it will be beneficial to advance the application of LIBS.

Electrolyte Analysis in Blood Serum by Laser-Induced Breakdown Spectroscopy Using a Portable Laser.

The fast and reliable analysis of electrolytes such as K, Na, Ca in human blood serum has become an indispensable tool for diagnosing and preventing diseases. Laser-induced breakdown spectroscopy (LIBS) has been demonstrated as a powerful analytical technique on elements. To apply LIBS to the quantitative analysis of electrolyte elements in real time, a self-developed portable laser was used to measure blood serum samples supported by glass slides and filter paper in this work. The partial least squares regression (PLSR) method was employed for predicting the concentrations of K, Na, Ca from serum LIBS spectra. Great prediction accuracies with excellent linearity were obtained for the serum samples, both on glass slides and filter paper. For blood serum on glass slides, the prediction accuracies for K, Na, Ca were 1.45%, 0.61% and 3.80%. Moreover, for blood serum on filter paper, the corresponding prediction accuracies were 7.47%, 1.56% and 0.52%. The results show that LIBS using a portable laser with the assistance of PLSR can be used for accurate quantitative analysis of elements in blood serum in real time. This work reveals that the handheld LIBS instruments will be an excellent tool for real-time clinical practice.

Probabilistic multivariable calibration for major elements analysis of MarSCoDe Martian laser-induced breakdown spectroscopy instrument on Zhurong rover

Mars Surface Composition Detector (MarSCoDe) is one of the major payloads onboard the Zhurong rover. The laser-induced breakdown spectroscopy (LIBS) component within MarSCoDe is capable of acquiring LIBS emission from 240 to 850 nm at targets ranging from 1.6 to 7 m. To address the previous issue of the indirect uncertainty estimation on the calibrations of other Martian LIBS, a recently developed natural gradient boosting probabilistic prediction (NGBoost) ensemble learning method was adopted for the LIBS calibration of MarSCoDe. Probabilistic Major Element Composition (PMEC) models based on NGBoost were established with the capacity of predicting the concentrations of 8 major element oxides (SiO2, TiO2, Al2O3, Fe2O3T, MgO, CaO, Na2O, K2O) in the form of normal distributions. The models were trained based on a ground spectral repository from MarSCoDe LIBS records of various reference samples. Optimizations for robustness and performance of the models were carried out with tunable max-pooling feature extraction and cross-validation-controlled hyperparameter tuning. The models were tested on an independent portion of the ground spectral repository and were checked with LIBS spectra of onboard calibration targets from Mars for their accuracy, error significancy relative to predicted uncertainty, consistency among single and averaged shots, and tolerance to mocked wavelength shifts. The PMEC models are presumably competent for basic elemental analysis of Martian silicate soil and rock along Zhurong's expedition. The limitation and interpretability of the models were also discussed to guide further works.

Laser-induced breakdown spectroscopy analysis of palladium in rock ore

An emerging geochemical analytical technique, laser-induced breakdown spectroscopy (LIBS), was applied to determine the concentration of palladium (Pd) in a one-meter-long quarter-core ore sample from the Lac des Îles palladium mine (Ontario, Canada). This paper demonstrates for the first time the analytical applicability of LIBS as a large-scale, high-performance analyzer for assessing the palladium content of ore. Principal component analysis of LIBS spectra shows three main mineralogical phases: a major silicon-rich and moderately iron-rich (5%) phase, a sulfide-rich phase, and a predominantly silicate phase. To calibrate the LIBS instrument, we used three sets of certified reference materials in the form of compressed powders with a quasi-homogeneous concentration of palladium ranging from around one part per million (ppm) to 500 ppm. Pearson correlation between the unknown spectra and the reference material spectra was used to select the appropriate reference material for quantitative Pd analysis for each single laser shot on the core sample. The palladium concentration of the three sides of nine quarter-core solid fragments was determined by LIBS using the Pd line at 348.115 nm and the average Pd concentration was compared to that obtained from the mine laboratory assay results for the remainder of the core. The LIBS analysis highlighted the significant heterogeneity of the palladium distribution on the surface of the ore and revealed that the sulfide-rich zones are particularly rich in palladium.

Constraining the chemical depth profile of a manganese-rich surface layer in Gale crater, Mars

Geochemical analyses by X-ray spectrometry and laser-induced breakdown spectroscopy (LIBS) instruments on the surface of Mars enable detailed studies of surface materials. The two techniques are utilized in concert by rovers to glean information in a complementary fashion. However, fundamental differences in how these analytical techniques function can produce perceived discrepancies in results, such as those resulting from variation in sampling volume. Here we utilize data acquired by the APXS (X-ray spectrometer) and ChemCam (LIBS) instruments on the Curiosity rover to investigate a manganese-rich surface layer, and, in the process, provide an improved chemical depth profile. We also demonstrate a method whereby current and future spacecraft capable of utilizing both techniques can potentially improve estimates of martian material near-surface density.

Access to quantitative analysis of carbonates using a portable LIBS instrument: First applications to single minerals and mineral mixtures

Natural carbonate standards of calcite structure were analysed using a handheld Laser-Induced Breakdown Spectroscopy (LIBS) device to investigate the spectral applicability for quantitative analysis in the Ca-Mg-Fe-Mn carbonate system. To obtain an initial understanding of the relationship between the elemental concentrations and LIBS signals, the determination coefficient (R2), root mean square error (RMSE) and mean arctangent absolute percentage error (MAAPE) for cross-validation and forecast accuracy were used, respectively. To relate the changes in spectral characteristics to the mineral content of carbonate mixtures, different spectral ratios were compared with mixture ratios between the two carbonate minerals. We found that spectral information from LIBS emission lines showed high correlations to their elemental concentration (Ca, Mg, Fe, and Mn), and their spectral ratios in carbonate mixtures showed a linear correlation with mineral content. Principal component analysis (PCA) was investigated the chemometric capability of the discrimination for carbonate minerals. This study demonstrates that handheld LIBS can be effectively applied in the field for the discrimination and identification of carbonate endmembers and their quantification for the case of mixtures.

Handheld LIBS analysis for in situ quantification of Li and detection of the trace elements (Be, Rb and Cs)

The world's lithium demand is currently increasing due to its use in batteries and in green energy technologies. As a consequence, Li has recently been added to the list of critical materials in Europe. Finding new deposits is necessary in order to guarantee a mid- to long-term stable supply. Granites and associated pegmatites are the primary ‘hard-rock’ source for Li, where it is present in a variety of aluminosilicate minerals. Li is a light element that typically occurs at low concentrations in rocks and minerals, which presents challenges for some analytical techniques (e.g., portable X-ray fluorescence) for exploration. Laser induced breakdown spectroscopy (LIBS) is a powerful analytical technique for the acquisition of simultaneous almost all elements of the periodic table. LIBS has particular sensitivity to the light elements (Z < 13) and, therefore, handheld LIBS has significant potential for the exploration of pegmatite- or granite-related Li mineralization. For this study, a suite of 16 pegmatite-hosted Li ore minerals comprising the three main aluminosilicate species (spodumene, lepidolite and petalite) that contained between 1.36 and 3.54 wt% Li was analyzed using a handheld LIBS instrument. A univariate calibration curve was developed for LIBS quantification of Li in these minerals using the strong Li emission lines at 610.36 nm and 670.79 nm (R2 > 0.9, RMSD = 0.2 wt% Li). Simultaneous quantification of Li contents and measurement of major element ratios (e.g., Si/Al) using portable LIBS permits rapid discrimination between different Li-bearing silicates, such as spodumene and petalite, that can be difficult to identify in the field on the basis of macroscopic criteria. Moreover, the detection of minor/trace elements such as Be, Rb and Cs is possible by handheld LIBS, which can provide useful information for rare metal pegmatite and granite exploration. Thus, qualitative and quantitative analysis by handheld LIBS represents a very promising approach for Li exploration.

Laser Induced breakdown spectroscopy (LIBS): Application to geological materials

Laser-induced breakdown spectroscopy (LIBS) is emerging as an analytical tool for investigating geological materials. The unique abilities of this technique proven its potential in the area of geology. Detection of light elements, portability for in-field analysis, spot detection, and no sample preparation are some features that make this technique appropriate for the study of geological materials. The application of the LIBS technique has been tremendously developed in recent years. In this report, results obtained from previous and most recent studies regarding the investigation of geological materials LIBS technique are reviewed. Firstly, we introduce investigations that report the advancement in LIBS instrumentation, its applications, especially in the area of gemology and the extraterrestrial/planetary exploration have been reviewed. Investigation of gemstones by LIBS technique is not widely reviewed in the past as compared to LIBS application in planetary exploration or other geological applications. It is anticipated that for the classification of gemstones samples, huge data set is appropriate and to analyze this data set, multivariate/chemometric methods will be useful. Recent advancement of LIBS instrumentation for the study of meteorites, depth penetration in Martian rocks and its regolith proved the feasibility of LIBS used as robotic vehicles in the Martian environment. Keywords: LIBS, gemstone, geological samples, extra-terrestrial.

Improving Calibration Strategy for LIBS Heavy Metals Analysis in Agriculture Applications

A new calibration procedure, known as mapping conditional-calibration laser-induced breakdown spectroscopy (LIBS), has been suggested to improve analysis results for heterogeneous samples. The procedure is based on LIBS elemental mapping, followed by signal conditioning in every sampling spot to skip signal outliers, then by finalizing the calibration curve construction. The suggested mapping conditional calibration procedure was verified for zinc analysis in soybean grist samples. The laser parameters correspond to those of the hand-held LIBS instrument in order to estimate the influence of sample surface heterogeneity under on-site analysis conditions. The laser spot (60 μm) was equal to or smaller than the typical size of grist particles (40–500 μm) but laser crater dimensions were significantly greater and varied widely (150–450 μm). The LIBS mapping of different spectral signals (atomic and ionic lines for major and minor components) was achieved. Elemental maps were normalized to achieve signal maps that were conditionally spotted to skip signal outliers. It was demonstrated that the suggested mapping conditional-calibration LIBS provided 15 ppm RMSECV for zinc determination in heterogeneous samples, which is typical for agricultural products.

Towards airborne laser-induced breakdown spectroscopy: A signal recovery method for LIBS instruments subjected to vibrations

Sample or instrument vibrations can scatter laser impacts across the sample surface, which increases the uncertainty of laser-induced breakdown spectroscopy (LIBS) measurements. The common sources of noise associated to mechanical vibration are described and a method for isolating LIBS measurements from artifacts introduced by such fluctuations is presented. The approach circumvents the use of mechanical stabilizers by leveraging simple components common in LIBS systems. A camera was used to capture close-up images of the sample for each laser shot and the laser spot position in the sample surface was measured using common image processing techniques. By associating spectra with spatial coordinates in the sample surface, it was possible to reduce the relative standard deviation of the Cu(I) 427.51 nm signal in a patterned Cu/Al sample from 122.0% to 53.31%, similar to that measured for a pure Cu sample in the same vibration conditions. The spatial resolution of the method was found to depend on the laser spot diameter, the illuminance at the sample, the camera sensitivity and trigger insertion delay, and the speed of the laser beam sweeping the sample surface. The spatial resolution obtained with the setup used was ±0.6 mm at 15 m, i.e., 40 μm per meter of separation between the instrument and the sample with a vibration speed limit of 12 cm·s−1.

From machine learning to transfer learning in laser-induced breakdown spectroscopy analysis of rocks for Mars exploration

With the ChemCam instrument, laser-induced breakdown spectroscopy (LIBS) has successively contributed to Mars exploration by determining the elemental compositions of soils, crusts, and rocks. The American Perseverance rover and the Chinese Zhurong rover respectively landed on Mars on February 18 and May 15, 2021, further increase the number of LIBS instruments on Mars. Such an unprecedented situation requires a reinforced research effort on the methods of LIBS spectral data analysis. Although the matrix effects correspond to a general issue in LIBS, they become accentuated in the case of rock analysis for Mars exploration, because of the large variation of rock compositions leading to the chemical matrix effect, and the difference in surface physical properties between laboratory standards (in pressed powder pellet, glass or ceramic) used to establish calibration models and natural rocks encountered on Mars, leading to the physical matrix effect. The chemical matrix effect has been tackled in the ChemCam project with large sets of laboratory standards offering a good representation of various compositions of Mars rocks. The present work more specifically deals with the physical matrix effect which is still lacking a satisfactory solution. The approach consists in introducing transfer learning in LIBS data treatment. For the specific application of total alkali-silica (TAS) classification of rocks (either with a polished surface or in the raw state), the results show a significant improvement in the ability to predict of pellet-based models when trained together with suitable information from rocks in a procedure of transfer learning. The correct TAS classification rate increases from 25% for polished rocks and 33.3% for raw rocks with a machine learning model, to 83.3% with a transfer learning model for both types of rock samples.

Multivariate stoichiometric analysis of gadolinium-doped ceria using low-power low-resolution laser-induced breakdown spectroscopy

Gadolinium-doped ceria (GDC) is a functional ceramic material used for the electrolytes and electrodes in solid oxide fuel cells (SOFCs). As the more SOFCs are used in power generation, a demand on the practical and reliable analytical methodology for GDCs would increase further. In this work, we investigated feasibility of the laser-induced breakdown spectroscopy (LIBS) instrument assembled with a compact low-power diode-pumped solid-state laser and a hand-held low-resolution spectrometer for stoichiometric analysis of GDCs. LIBS uses laser ablation sampling that greatly simplifies the sample preparation process by removing acid digestion, high temperature treatment, and further dilution indispensable for conventional elemental analyses. In the observed wavelength region of 397 – 450 nm, Gd and Ce poured out rich emission lines and those were unable to be resolved by the low-resolution spectrometer. However, the characteristic spectral features of Gd and Ce were successfully extracted from the unresolved spectra and well correlated with the mole fractions of Gd in GDCs by means of partial least squares-regression (PLS-R). Our results indicate that the low-performance LIBS instrument and PLS-R calibration can be a cost-effective practical technique for stoichiometric analysis of GDCs.

Analyses of Li-Rich Minerals Using Handheld LIBS Tool

Lithium (Li) is one of the latest metals to be added to the list of critical materials in Europe and, thus, lithium exploration in Europe has become a necessity to guarantee its mid- to long-term stable supply. Laser-induced breakdown spectroscopy (LIBS) is a powerful analysis technique that allows for simultaneous multi-elemental analysis with an excellent coverage of light elements (Z &lt; 13). This data paper provides more than 4000 LIBS spectra obtained using a handheld LIBS tool on approximately 140 Li-content materials (minerals, powder pellets, and rocks) and their Li concentrations. The high resolution of the spectrometers combined with the low detection limits for light elements make the LIBS technique a powerful option to detect Li and trace elements of first interest, such as Be, Cs, F, and Rb. The LIBS spectra dataset combined with the Li content dataset can be used to obtain quantitative estimation of Li in Li-rich matrices. This paper can be utilized as technical and spectroscopic support for Li detection in the field using a portable LIBS instrument.

Quantification of manganese for ChemCam Mars and laboratory spectra using a multivariate model

We report a new calibration model for manganese using the laser-induced breakdown spectroscopy instrument that is part of the ChemCam instrument suite onboard the NASA Curiosity rover. The model has been trained using an expanded set of 523 manganese-bearing rock, mineral, metal ore, and synthetic standards. The optimal calibration model uses the Partial Least Squares (PLS) and Least Absolute Shrinkage and Selection Operator (LASSO) multivariate techniques, with a novel “double blending” technique. We determined the detection limit for manganese is 82 ppm using a method blank procedure and is possibly as low as 27 ppm based on visual inspection of the spectra. Based on a representative test set consisting of measurements on 93 standards, the double blended multivariate model shows a Root Mean Squared Error of Prediction (RMSEP) accuracy of 1.39 wt% MnO for the full blended model. Employing a local RMSEP estimate where the model performance is evaluated based on nearby test samples, the accuracy is 0.03 wt% at the quantification limit (0.05 wt% MnO), 0.4 wt% accuracy at 1.0 wt% MnO, and 4.4 wt% accuracy at 100 wt% MnO. Precision is estimated using the standard deviation of the test set measurements, and is ±0.01 wt% MnO at the quantification limit, ±0.09 wt% MnO at 1.0 wt% MnO, and ± 2.1 wt% MnO at 100 wt% MnO (all 1 standard deviation). This new calibration is important for understanding the variation of manganese in the bedrock with the Curiosity rover on Mars, which provides insight into past redox conditions on Mars.