Laser-ablation Spark-induced Breakdown Spectroscopy Research Articles

Deep learning assisted femtosecond laser-ablation spark-induced breakdown spectroscopy employed for rapid and accurate identification of bismuth brass

BackgroundOwing to its excellent machinability and less toxicity, bismuth brass has been widely used in manufacturing various industrial products. Thus, it is of significance to perform rapid and accurate identification of bismuth brass to reveal the alloying properties. However, the analytical lines of various elements in bismuth brass alloy products based on conventional laser-induced breakdown spectroscopy (LIBS) are usually weak. Moreover, the analytical lines of various elements are often overlaped, seriously interfering with the identification of bismuth brass alloys. To address these challenges, developing an advanced strategy enabling to achieve ultra-high accuracy identification of bismuth brass alloys is highly desirable. ResultsThis work proposed a novel method for rapidly and accurately identifying bismuth brass samples using deep learning assisted femtosecond laser-ablation spark-induced breakdown spectroscopy (fs-LA-SIBS). With the help of fs-LA-SIBS, a spectral database containing high quality LIBS spectra on element components were constructed. Then, one-dimensional convolutional neural network (CNN) was introduced to distinguish five species of bismuth brass alloy. Amazingly, the optimal CNN model can provide an identification accuracy of 100 % for specie identification. To figure out the spectral features, we proposed a novel approach named “segmented fs-LA-SIBS wavelength”. The identification contribution from various wavelength intervals were extracted by optimal CNN model. It clearly showed that, the differences of spectra feature in the wavelength interval from 336.05 to 364.66 nm can produce the largest identification contribution for an identification accuracy of 100 %. More importantly, the feature differences in the four elements such as Ni, Cu, Sn, and Zn, were verified to mostly contribute to identification accuracy of 100 %. SignificanceTo the best of our knowledge, it is the first study on one-dimensional CNN configuration assisted with fs-LA-SIBS successfully employed for performing identification of bismuth brass. Compared with conventional machine learning methods, CNN has shown significant more superiority. To reveal the tiny spectra differences, the classification contribution from spectra features were accurately defined by our proposed “segmented fs-LA-SIBS wavelength” method. It can be expected that, CNN assisted with fs-LA-SIBS has great promising for identifying the differences from various element components in metallurgical field.

Rapid and accurate identification of steel alloys by femtosecond laser-ablation spark-induced breakdown spectroscopy and machine learning

This work investigates the application of femtosecond laser-ablation spark-induced breakdown spectroscopy (fs-LA-SIBS) combined with machine learning algorithms for the rapid and accurate identification of steel alloys. Three algorithms, namely random forest (RF), support vector machine (SVM), and partial least squares identification analysis (PLS-DA), were compared and evaluated. The results indicate that, in 100 independent classifications, the RF model demonstrated an average accuracy of 0.9337, significantly surpassing the accuracies of the SVM model at 0.8281 and the PLS-DA model at 0.8646. In addition, in the evaluation of 5-fold cross-validation and the prediction set, the RF model achieved a near-perfect micro-average area under curve (AUC) of 0.9996, surpassing the AUCs of the SVM model at 0.9761 and the PLS-DA model at 0.9847. The PCA results provided valuable insights into the spectral features that most significantly contributed to the classification accuracy, further confirming the RF model's robustness and effectiveness. This integrated approach offers a powerful tool for the rapid classification and accurate identification of steel alloys in industrial applications.

Accurate prediction analysis of steel alloy elements by femtosecond laser-ablation spark-induced breakdown spectroscopy and out-of-bag random forest regression

Femtosecond laser-ablation spark-induced breakdown spectroscopy (fs-LA-SIBS) and out-of-bag random forest regression (OOB-RFR) were developed for accurate quantitative analysis of the elements manganese (Mn), chromium (Cr), and nickel (Ni) in steel alloys.

Analysis of Cu and Zn contents in aluminum alloys by femtosecond laser-ablation spark-induced breakdown spectroscopy

Abstract To enhance the sensitivity of detecting Cu and Zn in aluminum alloys, we incorporated a spark discharge unit into the femtosecond laser-induced breakdown spectroscopy (fs-LIBS) system, forming a femtosecond laser ablation spark-induced breakdown spectroscopy (fs-LA-SIBS) system. We utilized both fs-LA-SIBS and fs-LIBS techniques to detect Cu and Zn in various aluminum alloy samples with different contents. Our results reveal that the spark discharge extends the duration of laser-induced plasma atomic radiation and amplifies the peak intensity of atomic radiation, thereby significantly increasing the time-integrated signal intensity of laser-induced plasma. Under the present experimental conditions, the limits of detection (LoDs) of Cu and Zn in aluminum alloy by fs-LA-SIBS are 16 and 12 ppm, respectively. In contrast, the LoDs of Cu and Zn by fs-LIBS technique under the same laser pulse energy are 96 and 84 ppm, respectively. Hence, for Cu, the LoDs by the fs-LA-SIBS technique are 1/6 of those by the fs-LIBS technique, and for Zn, the LoDs by the fs-LA-SIBS technique are 1/7 of those by the fs-LIBS technique. Our findings demonstrate that the fs-LA-SIBS technique is more sensitive than the fs-LIBS technique in the quantitative analysis of elements and may be a practical approach for elemental analysis in alloys.

One-Point and Multiline Calibration Fiber-Optic Laser-Ablation Spark-Induced Breakdown Spectroscopy for Quantitative Analysis of Elements in Aluminum Alloys

Rapid and accurate analysis of element concentrations in aluminum alloys is crucial due to their widespread use in modern industry. This paper proposes a one-point and multiline calibration fiber-optic laser-ablation spark-induced breakdown spectroscopy (OP-MLC FO-LA-SIBS) for the quantitative analysis of elements in aluminum alloys. The experimental system utilizes a compact fiber laser as the laser-ablation source and spark discharge to enhance the atomic emission. A portable multichannel fiber spectrometer is used to quickly collect spectra in the nongated mode. The concentrations of four elements (Mg, Cr, Cu, and Mn) in four aluminum alloy samples were calculated using the simple and efficient OP-MLC method, which involves taking another sample with a similar matrix as the standard sample. The average relative errors (AREs) for Mg, Cr, Cu, and Mn were 6.38%, 28.09%, 21.92%, and 18.97%, respectively. When the certified concentrations are greater than 0.02 wt.%, the ARE is only 13.04%. The OP-MLC FO-LA-SIBS system is compact, features simple spectra processing, and offers effective measurement, providing a convenient method for rapid and efficient quantitative analysis of elements in aluminum alloys in industrial production.

Quantitative elemental analysis of bismuth brass by microchip laser-ablation spark-induced breakdown spectroscopy

A compact microchip laser-based LIBS coupled with spark discharge was developed to realize sensitive and high spatial resolution elemental analysis.

Quantitative analysis of elemental concentrations of aluminum alloys using calibration-free femtosecond laser-ablation spark-induced breakdown spectroscopy

In this work, the calibration-free (CF) methodology combined with femtosecond laser-ablation spark-induced breakdown spectroscopy (fs LA-SIBS) was applied for the quantitative analysis of elements in aluminum alloy. A femtosecond laser (800 nm) operated at a repetition rate of 1 kHz with a pulse width of 35 fs was used as the laser-ablation source, and the plasma emission was enhanced by the spark discharge. Spectra were acquired using a compact fiber spectrometer coupled to a charge-coupled device and recorded at 200–500 nm. The aluminum alloy sample was mounted on a two-dimensional motion platform, and the effect of the sample moving speed on the spectral intensity was investigated. To evaluate the analysis performance of this technique, five standard aluminum alloy samples with certified elemental concentrations were tested. The average estimated electron density from these five transitions was (1.5 ± 0.3) × 1017 cm−3, which was determined by fitting the ion spectrum of Al II (281.62 nm) with Lorentz fitting. The plasma temperature was calculated to be 6300 ± 300 K using Saha–Boltzmann plots under the local thermodynamic equilibrium state. Trace elements with the content of <0.1% were detected by the proposed technique, and the analysis error of Al was <0.3%. This study shows that the CF fs LA-SIBS technique can be employed for quantitative analysis of major, minor, and trace elements in multi-composition alloys.

Application of quantitative analysis for aluminum alloy in femtosecond laser-ablation spark-induced breakdown spectroscopy using one-point and multi-line calibration

To achieve the quantitative elemental analysis of aluminum alloy samples, the one-point and multi-line calibration (OP-MLC) method and femtosecond laser-ablation spark-induced breakdown spectroscopy (fs-LA-SIBS) were combined in this study. An ultrafast Ti: sapphire laser with high single-pulse energy and high repetition–rate operation was used as the laser source to ablate the sample at a 1k Hz pulse repetition rate and achieve re-excitation using spark discharge. Subsequently, an enhanced spectral peak intensity was achieved, which increased the sensitivity and analytical capabilities of laser-induced breakdown spectroscopy (LIBS) technique. Considering only one confirmed sample, the OP-MLC method was used to calculate the concentration ratios of trace elements Mg, Cr, Cu, Mn and Zn in four aluminum alloy samples to the calibration samples by the integral intensity ratio of the elemental characteristic lines between the two samples. The average relative errors with the identified concentrations were 3.99%, 15.13%, 8.76%, 9.30% and 9.64%, respectively. The results showed that the combination of OP-MLC method and fs-LA-SIBS has good accuracy in the quantitative analysis of elements, and has the advantages of simplicity, rapidity and high sensitivity.

Elemental Analysis of V, Mo, Cr, Mn, Al, Ni, and Cu in Steel Alloy with Femtosecond Laser Ablation Spark-Induced Breakdown Spectroscopy

Femtosecond laser ablation spark-induced breakdown spectroscopy (fs LA-SIBS) was developed to quantitatively analyze vanadium, molybdenum, chromium, manganese, aluminum, nickel, and copper in a steel alloy. In the experiment, a femtosecond laser operating at a repetition rate of 1 kHz was used as the laser ablation source, and spark discharge was utilized to re-excite the plasma and enhance the atomic intensity. A compact fiber spectrometer was used to record and analyze the plasma emission spectra in a nongated signal-recording mode. The calibration curves of V, Mo, Cr, Mn, Al, Ni, and Cu elements in steel alloy samples were established, and the detection limits of these elements were determined to be 10.9, 12.6, 4.0, 5.7, 8.7, 7.9, and 3.1 ppm with fs LA-SIBS, respectively, which were 4–12-fold better than those achieved with femtosecond laser-induced breakdown spectroscopy (fs LIBS). Compared with conventional LIBS, the fs LA-SIBS technique provided a rapid and high spatial resolution approach to quantitative elemental analysis, with better analytical sensitivity.

Accurate elemental analysis of alloy samples with high repetition rate laser-ablation spark-induced breakdown spectroscopy coupled with particle swarm optimization-extreme learning machine

High repetition rate laser-ablation spark-induced breakdown spectroscopy (HRR LA-SIBS) coupled with particle swarm optimization-extreme learning machine (PSO-ELM) was developed to realize quantitative elemental analysis of aluminum alloy accurately. A compact Nd: YAG laser operated at 1 kHz was used as the ablation laser and a spark discharge was utilized to enhance the plasma emission. The characteristic lines of the elements were selected as input variables and the parameters of ELM were optimized by the PSO algorithm. The PSO-ELM calibration models were established. The correlation coefficient of prediction set reached to 0.9996, 0.9972 and 0.9999, the root mean square error of prediction set decreased to 0.0138%, 0.0045% and 0.0095% for Mg, Cr, and Cu analysis, respectively. Better predictive performance has been demonstrated in comparison with the univariate and SVM methods. HRR LA-SIBS coupled with PSO-ELM can give convenient, rapid and accurate elemental analysis of alloy samples. Moreover, it will extend the potential applications of HRR LA-SIBS in intelligent manufacturing and on-line monitoring in the future.

Quantitative elemental analysis of aluminum alloys with one-point calibration high repetition rate laser-ablation spark-induced breakdown spectroscopy

A one-point calibration method has been successfully used to improve the analytical accuracy of the calibration free HRR LA-SIBS technique.

Quantitative analysis of trace elements in bismuth brass with high repetition rate laser-ablation spark-induced breakdown spectrum

Bismuth brass has very good mechanical properties and is friendly to environment. Therefore, it can be widely used in different fields. In order to realize the convenient, rapid and sensitive elemental analysis of trace elements in bismuth brass, fiber laser based high repetition rate laser-ablation spark-induced breakdown spectroscopy (HRR LA-SIBS) is developed. In the experiments, a compact fiber laser operated at 5 kHz pulse repetition rate is used to ablate the sample and produce plasma, and the spark discharge is used to further break down the ablated sample and enhance the plasma emission for sensitive elemental analysis. A compact fiber-optic spectrometer coupled with non-intensified charge-coupled device (CCD) is used to record the spectra. Bismuth, lead and tin in several bismuth brass standard samples are quantitatively analyzed. The plasma temperature is determined to be about 7962 ± 300 K by using the Boltzmann plots of copper, zinc and tin elements; the electron density is determined to be about 1.049 × 10&lt;sup&gt;–17&lt;/sup&gt; cm&lt;sup&gt;–3&lt;/sup&gt; based on the Stark broadening of Cu (I) 510.47 nm analytical line. The plasma is determined to be in local thermodynamic equilibrium (LTE) state according to McWhirter criterion as well as appended criteria for transient plasma. Under the present experimental condition, the calibration curves of bismuth, lead and tin in bismuth brass are built with fitting goodness of higher than 95%. The detection limits of bismuth, lead and tin are determined to be 25.5 ppm, 64.2 ppm and 316.5 ppm, respectively. The weak transition probability of tin atoms leads to worse detection limit of tin than the scenarios of bismuth and lead. The ways to further improve the analytical sensitivity and minimize system dimensions are discussed in this article. It is demonstrated that high repetition rate laser-ablation spark-induced breakdown spectrometer based on compact fiber laser as well as compact fiber-optic spectrometer can be used to realize the convenient, rapid and sensitive elemental analysis of trace elements in bismuth brass. This study is also helpful in analyzing the trace harmful elements, including bismuth, lead and tin in high temperature alloys with HRR LA-SIBS. In comparison with laser-induced breakdown spectroscopy (LIBS), the HRR LA-SIBS technique has several intrinsic advantages, such as fast spectral data collection speed, cost-effective system and low continuum background and so on. This technique is very useful in implementing the elemental analysis of different alloy samples and can be potentially used in metallurgical industry in the future.

Application of calibration-free high repetition rate laser-ablation spark-induced breakdown spectroscopy for the quantitative elemental analysis of a silver alloy.

In this work, we report the application of a calibration-free (CF) method combined with high repetition rate laser-ablation spark-induced breakdown spectroscopy (HRR LA-SIBS) to the analysis of a silver alloy. The sample was ablated by a fiber laser operated at a 30 kHz pulse repetition rate, and a spark discharge was applied to enhance plasma emission. Electron number density and plasma temperature were estimated using Stark broadening of spectral lines and the Saha-Boltzmann plot method, respectively. The fulfillment of the local thermodynamic equilibrium (LTE) approximation of the measurement was verified. Averaged electron density and plasma temperature were calculated as 1.11×1017cm-3 and 7355 K, respectively. The elemental composition of a silver alloy sample was determined, and the result was compared with that analyzed with inductively coupled plasma optical emission spectrometry (ICP-OES). The analytical error was within a 15% range. It was demonstrated that the CF HRR LA-SIBS technique could potentially provide elemental analysis for silver alloys without requiring a standard sample.

高重复频率激光剥离-火花诱导击穿光谱中原子辐射的时域特性研究

高重复频率激光剥离-火花诱导击穿光谱中原子辐射的时域特性研究

Application of fiber optic high repetition rate laser-ablation spark-induced breakdown spectroscopy on the elemental analysis of aluminum alloys.

Fiber optic high repetition rate laser-ablation spark-induced breakdown spectroscopy was applied to realize elemental analysis of aluminum alloys. A compact fiber laser was used as source of laser-ablation and spark discharge was used to enhance the atomic emission of the laser-induced plasma. Plasma emission spectra were recorded with a compact fiber spectrometer in a nongated signal recording mode. Calibration curves of Cr, Cu, Mn, Mg, and Zn in aluminum alloys were built under appropriate experimental conditions and the detection limits of these elements were determined to be 4.4, 5.6, 4.9, 8.3, and 31.1 ppm, respectively. Compared to those obtained in fiber optic high repetition rate laser-induced breakdown spectroscopy using the same fiber laser, a 3-18 improvement factor in the detection limit has been demonstrated. This system is compact and cost effective, and the technique can be applied to rapid and convenient element analysis of different alloy samples.

Calibration-free elemental analysis combined with high repetition rate laser-ablation spark-induced breakdown spectroscopy

Calibration-free (CF) method combined with high repetition rate laser-ablation spark-induced breakdown spectroscopy (HRR LA-SIBS) was first utilized to realize elemental analysis of alloy samples. A compact fiber laser operated at 30 kHz pulse repetition rate was used to ablate the sample and the spectra were recorded with a compact fiber spectrometer in non-gated signal recording mode. Three standard aluminum alloy samples were analyzed to evaluate the performance of this technique. Median filtering method was applied to reduce the contribution of the continuum background to the intensity of the atomic lines. The averaged electron density was determined to be (2.36–2.49) × 1017 cm−3 according to the Stark broadening of four ionic lines. 11,800 K averaged plasma temperature was estimated from the Saha-Boltzmann plots. The plasma could be verified to be in a state close to local thermodynamic equilibrium. The analytical error was <0.5% for the major element and <35% for minor elements with >0.1% concentrations. It was demonstrated that CF method combined with HRR LA-SIBS was possible to realize reliable quantitative elemental analysis for aluminum alloy samples.

Sensitive elemental analysis with high repetition rate laser-ablation spark-induced breakdown spectroscopy combined with lock-in signal detection

High repetition rate laser-ablation spark-induced breakdown spectroscopy (HRR LA-SIBS) combined with lock-in signal detection was developed to realize sensitive trace elements analysis. In order to realize the lock-in signal detection, the repetition rate of laser pulses was increased to 4 kHz and the time duration of the plasma emission was prolonged to be about 10 microseconds by the spark discharge, thus the duty cycle has been increased to 4% approximately. The influence of the continuum background of the plasma emission to the signal detection was reduced with a gated preamplifier. Trace lead and aluminum in brass samples and trace chromium and manganese in aluminum alloy samples were analyzed experimentally. The detection limits of them were estimated to be about 112, 178, 235 and 202 ppb under current experimental condition, demonstrating an obvious improvement on the analytical sensitivity of this technique comparing with conventional single pulse laser-induced breakdown spectroscopy. The HRR LA-SIBS technique combined with lock-in signal detection can be potentially applied to realize direct and sensitive elemental analysis of different solid samples.

Elemental analysis of copper alloys with laser-ablation spark-induced breakdown spectroscopy based on a fiber laser operated at 30 kHz pulse repetition rate

The analytical sensitivity of a compact LIBS system consisting of a fiber laser and a fiber spectrometer was successfully improved by the spark discharge.

Elemental analysis of copper alloy by high repetition rate LA-SIBS using compact fiber spectrometer

High repetition rate laser-ablation spark-induced breakdown spectroscopy (HRR LA-SIBS) was first used to analyze trace elements in copper alloy samples. The 1064 nm output of an acousto-optically Q-switched Nd:YAG laser operated at a pulse repetition rate of 1 kHz was utilized to ablate copper alloy and to form original plasma, spark-discharge was applied to further breakdown the ablated samples and enhance the emission of the laser-induced plasma. A compact multichannel fiber spectrometer was used to analyze the plasma emission under non-gated operation mode. Under the assistance of high repetition rate spark discharge, the plasma emission was able to be improved significantly. The determined limits of the detection of lead and aluminum were 15.5 ppm and 1.9 ppm by HRR LA-SIBS, respectively, which were 11 and 6 folds better than that determined by HRR LIBS under the same laser-ablation condition. This work demonstrates the feasibility of using fiber spectrometer to analyze plasma emission under non-gated operation mode and the possibility of building a portable HRR LA-SIBS system for rapid elemental analysis of copper alloys and other solid samples.

Triggered parallel discharge in laser-ablation spark-induced breakdown spectroscopy and studies on its analytical performance for aluminum and brass samples

In laser-ablation spark-induced breakdown spectroscopy (LA-SIBS), the discharge channel is an important factor to affect both analytical sensitivity and lateral resolution on the sample surface. In order to study this effect, a gated pulsed high-voltage power supply was selected as the power source of the spark discharge, the dependence of the discharge channel on the time delay between the high voltage pulse and the laser pulse was studied in this work. It was demonstrated that under suitable laser pulse energy and geometrical arrangement of the electrodes, it was possible to change V-shape discharge to parallel discharge by increasing this time delay. In the V-shape discharge, the spark discharge could ablate more samples and increase the diameters and depths of the craters; however, in the parallel discharge, the spark discharge hardly ablated new samples, to make sure that the spatial resolution in LA-SIBS was only determined by the laser ablation. Under parallel discharge, the intensity of the atomic emission of the plasma decreases with the increasing of time delay but increases with the increasing of the discharge voltage. 4–10 folds enhancement factors have been achieved in the detection limits of the analytes in the employed targets under current experimental conditions. It is suggested that spark discharge under external trigger mode should be selected to realize parallel discharge if high spatial resolution elemental analysis of solid samples is required.