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1.
Qiuyun WANG 《等离子体科学和技术》2019,21(6):65504-146
The combination of spark discharge and laser-induced breakdown spectroscopy (LIBS) is called spark discharge assisted LIBS. It works under laser-plasma triggered spark discharge mode, and shows its ability to enhance spectral emission intensity. This work uses a femtosecond laser as the light source, since femtosecond laser has many advantages in laser-induced plasma compared with nanosecond laser, meanwhile, the study on femtosecond LIBS with spark discharge is rare. Time-resolved spectroscopy of spark discharge assisted femtosecond LIBS was investigated under different discharge voltages and laser energies. The results showed that the spectral intensity was significantly enhanced by using spark discharge compared with LIBS alone. And, the spectral emission intensity using spark discharge assisted LIBS increased with the increase in the laser energy. In addition, at low laser energy, there was an obvious delay on the discharge time compared with high laser energy, and the discharge time with positive voltage was different from that with negative voltage. 相似文献
2.
Qiuyun WANG Anmin CHEN Miao LIU Yitong LIU Qingxue LI Suyu LI Yuanfei JIANG Xun GAO Mingxing JIN 《等离子体科学和技术》2021,23(4):45504-82
In this study, a femtosecond laser was focused to ablate brass target and generate plasma emission in air. The influence of lens to sample distance(LTSD) on spectral emission of brass plasma under linearly and circularly polarized pulses with different pulse energies was investigated. The results indicated that the position with the strongest spectral emission moved toward focusing lens with increasing the energy. At the same laser energy, the line emission under circularly polarized pulse was stronger compared with linearly polarized pulse for different LTSDs. Next, electron temperature and density of the plasma were obtained with Cu(Ⅰ) lines,indicating that the electron temperature and density under circularly polarized pulse were higher compared to that under linearly polarized pulse. Therefore, changing the laser polarization is a simple and effective way to improve the spectral emission intensity of femtosecond laserinduced plasma. 相似文献
3.
In the field of dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) research, the pursuit of methods for determining pulse intervals and other parameters quickly and conveniently in order to achieve optimal spectral signal enhancement is paramount. To aid researchers in identification of optimal signal enhancement conditions and more accurate interpretation of the underlying signal enhancement mechanisms, theoretical simulations of the spatiotemporal processes of coaxial DP-LIBS-induced plasma have been established in this work. Using a model based on laser ablation and two-dimensional axisymmetric fluid dynamics, plasma evolutions during aluminum–magnesium alloy laser ablation under single-pulse and coaxial dual-pulse excitations have been simulated. The influences of factors, such as delay time, laser fluence, plasma temperature, and particle number density, on the DP-LIBS spectral signals are investigated. Under pulse intervals ranging from 50 to 1500 ns, the time evolutions of spectral line intensity, dual-pulse emission enhancement relative to the single-pulse results, laser irradiance, spatial distribution of plasma temperature and species number density, as well as laser irradiance shielded by plasma have been obtained. The study indicates that the main reason behind the radiation signal enhancement in coaxial DP-LIBS-induced plasma is attributed to the increased species number density and plasma temperature caused by the second laser, and it is inferred that the shielding effect of the plasma mainly occurs in the boundary layer of the stagnation point flow over the target surface. This research provides a theoretical basis for experimental research, parameter optimization, and signal enhancement tracing in DP-LIBS. 相似文献
4.
Miao LIU Anmin CHEN Yutong CHEN Xiangyu ZENG Qiuyun WANG Dan ZHANG Dapeng YANG Mingxing JIN 《等离子体科学和技术》2021,23(7):75501-126
In this paper, we investigated the emission spectra of plasmas produced from femtosecond and nanosecond laser ablations at different target temperatures in air. A brass was selected as ablated target of the experiment. The results indicated that spectral emission intensity and plasma temperature showed similar trend for femtosecond and nanosecond lasers, and the two parameters were improved by increasing the sample temperature in both cases. Moreover, the temperature of nanosecond laser-excited plasma was higher compared with that of femtosecond laser-excited plasma, and the increase of the plasma temperature in the case of nanosecond laser was more evident. In addition, there was a significant difference in electron density between femtosecond and nanosecond laser-induced plasmas. The electron density for femtosecond laser decreased with increasing the target temperature, while for nanosecond laser, the electron density was almost unchanged at different sample temperatures. 相似文献
5.
The influence of the target temperature on the molecular emission of femtosecond laser-induced breakdown spectroscopy (LIBS) was investigated experimentally.An Al target was ablated to produce laser-induced plasma.The Al target was uniformly heated to a maximum of 250 ℃.The measured molecular emission was AlO (△υ =0) from the femtosecond LIBS of the Al target.The measurements indicated that the molecular emission of AIO increased as the temperature of the A1 target increased.In addition,a two-temperature model was used to simulate the evolution of the electron and lattice temperature of the Al target with different initial temperatures.The simulated results showed that the electron and lattice temperatures of Al irradiated by the femtosecond laser increased as the initial temperature of the A1 target increased;also,the simulated ablated depth increased.Therefore,an increase in the initial A1 target temperature resulted in an enhancement in the spectral signal of AlO from the femtosecond LIBS of Al,which was directly related to the increase in the size of the ablated crater.The study suggested that increasing the temperature of the target improves the intensity of molecular emission in femtosecond LIBS. 相似文献
6.
Wei QI 《等离子体科学和技术》2021,23(4):45501-045501
The influence of the target temperature on the molecular emission of femtosecond laser-induced breakdown spectroscopy(LIBS) was investigated experimentally. An Al target was ablated to produce laser-induced plasma. The Al target was uniformly heated to a maximum of 250℃. The measured molecular emission was AlO(△ν=0) from the femtosecond LIBS of the Al target.The measurements indicated that the molecular emission of AlO increased as the temperature of the Al target increased. In addition, a two-temperature model was used to simulate the evolution of the electron and lattice temperature of the Al target with different initial temperatures. The simulated results showed that the electron and lattice temperatures of Al irradiated by the femtosecond laser increased as the initial temperature of the Al target increased; also, the simulated ablated depth increased. Therefore, an increase in the initial Al target temperature resulted in an enhancement in the spectral signal of AlO from the femtosecond LIBS of Al,which was directly related to the increase in the size of the ablated crater. The study suggested that increasing the temperature of the target improves the intensity of molecular emission in femtosecond LIBS. 相似文献
7.
Junfeng SHAO 《等离子体科学和技术》2020,22(7):74001-074001
Spectral intensity,electron temperature and density of laser-induced plasma(LIP) are important parameters for affecting sensitivity of laser-induced breakdown spectroscopy(LIBS).Increasing target temperature is an easy and feasible method to improve the sensitivity.In this paper,a brass target in a temperature range from 25℃ to 200℃ was ablated to generate the LIP using femtosecond pulse.Time-resolved spectral emission of the femtosecond LIBS was measured under different target temperatures.The results showed that,compared with the experimental condition of 25℃,the spectral intensity of the femtosecond LIP was enhanced with more temperature target.In addition,the electron temperature and density were calculated by Boltzmann equation and Stark broadening,indicating that the changes in the electron temperature and density of femtosecond LIP with the increase of the target temperature were different from each other.By increasing the target temperature,the electron temperature increased while the electron density decreased.Therefore,in femtosecond LIBS,a hightemperature and low-density plasma with high emission can be generated by increasing the target temperature.The increase in the target temperature can improve the resolution and sensitivity of femtosecond LIBS. 相似文献
8.
In this paper,an experimental study of collinear geometry double-pulse femtosecond LIBS was performed on a Ni sample in ambient air in an effort to clarify the contributing processes responsible for the signal enhancement observed in comparison with the single-pulse case.Doublepulse LIBS spectra show a very clear enhancement when an optimum inter-pulse delay was used.The influences of the inter-pulse delay between two pulses on the LIBS signal intensity,electron temperature and density were investigated.It is most remarkable that the evolutions of signal enhancement and electron temperature versus the inter-pulse delay showed the same behavior and revealed two main regimes of interaction.These results provide additional insight into the possible emission enhancement mechanisms in the double pulse configuration. 相似文献
9.
The influence of the energy of femtosecond laser pulses on the intensity of Fe I (371.99 nm) emission line and the continuous spectrum of the plasma generated on the surface of Fe3+ water solution by a Ti: sapphire laser radiation with pulse duration <45 fs and energies up to 7 mJ is determined. A calibration curve was obtained for Fe3+ concentration range from 0.5 g/L to the limit of detection in water solution, and its saturation was detected for concentrations above 0.25 g/L, which is ascribed to self-absorption. The 3σ-limit of detection obtained for Fe in water solution is 2.6 mg/L in the case of 7 mJ laser pulse energy. It is found that an increase of laser pulse energy insignificantly affects on LOD in the time-resolved LIBS and leads to a slight improvement of the limit of detection. 相似文献
10.
A diode-pumped solid-state laser(DPSSL) with a high energetic stability and long service life is applied to ablate the steel samples instead of traditional Nd:YAG laser pumped by a xenon lamp,and several factors, such as laser pulse energy, repetition rate and argon flow rate, that influence laser-induced breakdown spectroscopy(LIBS) analytical performance are investigated in detail.Under the optimal experiment conditions, the relative standard deviations for C, Si, Mn, Ni, Cr and Cu are 3.3%–8.9%, 0.9%–2.8%, 1.2%–4.1%, 1.7%–3.0%, 1.1%–3.4% and 2.5%–8.5%,respectively, with the corresponding relative errors of 1.1%–7.9%, 1.0%–6.3%, 0.4%–3.9%,1.5%–6.3%, 1.2%–4.0% and 1.2%–6.4%. Compared with the results of the traditional spark discharge optical emission spectrometry technique, the analytical performance of LIBS is just a little inferior due to the less stable laser-induced plasma and smaller amount of ablated sample by the laser. However, the precision, detection limits and accuracy of LIBS obtained in our present work were sufficient to meet the requirements for process analysis. These technical performances of higher stability of output energy and longer service life for DPSSL, in comparison to the Q-switch laser pumped by xeon lamp, qualify it well for the real time online analysis for different industrial applications. 相似文献
11.
Jelena PETROVIĆ Dragan RANKOVIĆ Miroslav KUZMANOVIĆ Jelena SAVOVIĆ Vasili KIRIS Alena NEVAR Mikhail NEDELKO Nikolai TARASENKO 《等离子体科学和技术》2023,62(4):045507-045507
Time-integrated optical emission analysis of laser-induced plasma on Teflon is presented. Plasma was induced under atmospheric pressure air using transversely excited atmospheric CO2 laser pulses. Teflon is a C-based polymer that is, among other things, interesting as a substrate for laser-induced breakdown spectroscopy analysis of liquid samples. This study aimed to determine the optimal experimental conditions for obtaining neutral and ionized C spectral lines and C2 and CN molecular band emission suitable for spectrochemical purposes. Evaluation of plasma parameters was done using several spectroscopic techniques. Stark profiles of appropriate C ionic lines were used to determine electron number density. The ratio of the integral intensity of ionic-to-atomic C spectral lines was used to determine the ionization temperature. A spectral emission of C2 Swan and CN violet bands system was used to determine the temperature of the colder, peripheral parts of plasma. We critically analyzed the use of molecular emission bands as a tool for plasma diagnostics and suggested methods for possible improvements. 相似文献
12.
The detection of manganese (Mn) in steel by laser-induced breakdown spectroscopy (LIBS) provides essential information for steelmaking. However, self-absorption greatly disrupts the LIBS spectral lines of Mn with high content. In this study, to minimize self-absorption for Mn spectral lines in LIBS, laser-induced fluorescence (LIF) was applied. Compared with conventional LIBS, the self-absorption factors (α ) of Mn I 403.08, 403.31, and 403.45 nm lines were reduced by 90%, 88%, and 88%, respectively; the root mean square errors of cross-validation were decreased by 88%, 85%, and 87%, respectively; the average relative errors were reduced by 93%, 90%, and 91%, respectively; and average relative standard deviations were decreased by 29%, 32%, and 33%, respectively. The LIBS-LIF was shown to successfully minimize the self-absorption effect and spectral intensity fluctuation and improve detection accuracy. 相似文献
13.
Jinjia GUO 《等离子体科学和技术》2019,21(3):34022-187
Laser-induced breakdown spectroscopy (LIBS) has attracted extensive attention as a new technique for in-situ marine application. In this work, the influence of deep-sea high pressure environment on LIBS signals was investigated by using a compact LIBS-sea system developed by Ocean University of China for the in-situ chemical analysis of seawater. The results from the field measurements show that the liquid pressure has a significant effect on the LIBS signals. Higher peak intensity and larger line broadening were obtained as the pressure increases. By comparing the variations of the temperature and salinity with the LIBS signals, a weak correlation between them can be observed. Under high pressure conditions, the optimal laser energy was higher than that in air environment. When the laser energy exceeded 17 mJ, the effect of laser energy on the signal intensity weakened. The signal intensity decreases gradually at larger delays. The obtained results verified the feasibility of the LIBS technique for the deep-sea in-situ detection, and we hope this technology can contribute to surveying more deep-sea environments such as the hydrothermal vent regions. 相似文献
14.
Laser-induced breakdown spectroscopy(LIBS) combined with K-means algorithm was employed to automatically differentiate industrial polymers under atmospheric conditions.The unsupervised learning algorithm K-means were utilized for the clustering of LIBS dataset measured from twenty kinds of industrial polymers.To prevent the interference from metallic elements,three atomic emission lines(C I 247.86 nm,H I 656.3 nm,and O I 777.3 nm) and one molecular line C–N(0,0) 388.3 nm were used.The cluster analysis results were obtained through an iterative process.The Davies–Bouldin index was employed to determine the initial number of clusters.The average relative standard deviation values of characteristic spectral lines were used as the iterative criterion.With the proposed approach,the classification accuracy for twenty kinds of industrial polymers achieved 99.6%.The results demonstrated that this approach has great potential for industrial polymers recycling by LIBS. 相似文献
15.
Peng ZHANG 《等离子体科学和技术》2022,24(8):84006
The concentrations of SiO2, Al2O3, K2O, Na2O, CaO, MgO, Fe2O3 and TiO2, and loss on ignition (L.O.I.) are the main inorganic components of geological samples. Concentrations of the eight oxides and L.O.I. are also the main indicators of concern in the production of building ceramics. Quantitative analysis of the eight oxides and L.O.I. was performed using fiber-laser-based laser-induced breakdown spectroscopy (LIBS). A combination of continuous background deduction, full width at half maximum (FWHM) intensity integral and spectral sum normalization was proposed for data processing. After the data processing combined the continuous background deduction, FWHM intensity integral and spectral sum normalization, the mean absolute errors (MAEs) of the calibration of L.O.I., SiO2, Al2O3, K2O, Na2O, CaO, MgO, Fe2O3 and TiO2 was reduced from 2.03%, 12.06%, 4.84%, 1.10%, 0.69%, 0.31%, 0.11%, 0.20% and 0.10% to 1.80%, 9.48%, 2.12%, 0.36%, 0.58%, 0.11%, 0.08%, 0.19% and 0.05%, respectively. This multivariate method was further introduced and discussed to improve the analysis performance. The MAEs of L.O.I., SiO2, Al2O3, K2O and Na2O were further reduced to 1.12%, 2.07%, 1.38%, 0.35% and 0.43%, respectively. The results show that the overall prediction error can meet the requirements for the production of building ceramics. The LIBS desktop analyzer has great potential in detection applications on geological samples. 相似文献
16.
Spatial confinement can significantly enhance the spectral intensity of laser-induced plasma in air.It is attributed to the compression of plasma plume by the reflected shockwave.In addition,optical emission spectroscopy of laser-induced plasma can also be affected by the distance between lens and sample surface.In order to obtain the optimized spectral intensity,the distance must be considered.In this work,spatially confined laser-induced silicon plasma by using a Nd:YAG nanosecond laser at different distances between lens and sample surface was investigated.The laser energies were 12 mJ,16 mJ,20 mJ,and 24 mJ.All experiments were carried out in an atmospheric environment.The results indicated that the intensity of Si (I) 390.55 nm line firstly rose and then dropped with the increase of lens-to-sample distance.Moreover,the spectral peak intensity with spatial confinement was higher than that without spatial confinement.The enhancement ratio was approximately 2 when laser energy was 24 mJ. 相似文献
17.
LI Cheng 《等离子体科学和技术》2015,17(11):919-922
In this paper the spectral enhancement of laser-induced breakdown spectroscopy (LIBS) for copper plasma in the presence of a magnetic field is investigated and the temporal-and spatial-resolved plasma emission spectra are analyzed. Experimental results show that the copper plasma atomic and ion spectra have been enhanced in the presence of the external magnetic field. In addition, the Cu I 521.82 nm spectral intensity evolution with delay time appears to have a double peak around the delay time of 2 μs, but that of Cu II 507.57 nm has a sharp decrease because of the electron-atom three body recombination process. The plasma temperature with magnetic confinement is lower than that of the case in the absence of magnetic fields. Finally, the spectral enhancement mechanisms of laser induced breakdown spectroscopy with magnetic confinement are analyzed. 相似文献
18.
叶晋瑞;李亚举;张朝;王新威;陶科伟;曾强;陈良文;钱东斌;张少峰;杨磊;马新文 《等离子体科学和技术》2024,26(9):095501-1-095501-8
A non-contact method for millimeter-scale inspection of material surface flatness via Laser-Induced Breakdown Spectroscopy(LIBS)is investigated experimentally.The experiment is performed using a planished surface of an alloy steel sample to simulate its various flatness,ranging from 0 to 4.4 mm,by adjusting the laser focal plane to the surface distance with a step length of 0.2 mm.It is found that LIBS measurements are successful in inspecting the flatness differences among these simulated cases,implying that the method investigated here is feasible.It is also found that,for achieving the inspection of surface flatness within such a wide range,when univariate analysis is applied,a piecewise calibration model must be constructed.This is due to the complex dependence of plasma formation conditions on the surface flatness,which inevitably complicates the inspection procedure.To solve the problem,a multivariate analysis with the help of Back-Propagation Neural Network(BPNN)algorithms is applied to further construct the calibration model.By detailed analysis of the model performance,we demonstrate that a unified calibration model can be well established based on BPNN algorithms for unambiguous millimeter-scale range inspection of surface flatness with a resolution of about 0.2 mm. 相似文献
19.
ZHANG Dacheng 《等离子体科学和技术》2015,17(11):971-974
Laser-induced breakdown spectroscopy (LIBS) is regarded as a suitable method for the remote analysis of materials in any phase, even in an environment with high radiation levels. In the present work we used the third harmonic pulse of a Nd:YAG laser for ablation of uranium metal and measured the plasma emission with a fiber-optic spectrometer. The LIBS spectra of uranium metal and their features in different ambient gases (i.e., argon, neon, oxygen, and nitrogen) at atmospheric pressure were studied. Strong continuum spectrum and several hundreds of emission lines from UI and UII were observed. It is found that the continuum spectrum observed in uranium not only comes from bremsstrahlung emission but is also due to the complex spectrum of uranium. The influence of ambient gas and the gas flow rate for ablation of uranium metal was investigated. The experimental results indicate that the intensity of the uranium lines was enhanced in argon and nitrogen. However, the intensity of uranium lines was decreased in oxygen due to the generation of UO and other oxides. The results also showed that the highest intensity of uranium lines were obtained in argon gas with a gas flow rate above 2.5 L/min. The enhanced mechanism in ambient gas and the influence of the gas flow rate were analyzed in this work. 相似文献
20.
A non-contact method for millimeter-scale inspection of material surface flatness via Laser-Induced Breakdown Spectroscopy (LIBS) is investigated experimentally. The experiment is performed using a planished surface of an alloy steel sample to simulate its various flatness, ranging from 0 to 4.4 mm, by adjusting the laser focal plane to the surface distance with a step length of 0.2 mm. It is found that LIBS measurements are successful in inspecting the flatness differences among these simulated cases, implying that the method investigated here is feasible. It is also found that, for achieving the inspection of surface flatness within such a wide range, when univariate analysis is applied, a piecewise calibration model must be constructed. This is due to the complex dependence of plasma formation conditions on the surface flatness, which inevitably complicates the inspection procedure. To solve the problem, a multivariate analysis with the help of Back-Propagation Neural Network (BPNN) algorithms is applied to further construct the calibration model. By detailed analysis of the model performance, we demonstrate that a unified calibration model can be well established based on BPNN algorithms for unambiguous millimeter-scale range inspection of surface flatness with a resolution of about 0.2 mm. 相似文献