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1.
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
2.
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
3.
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
4.
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
5.
In double-pulse laser-induced breakdown spectroscopy(DP-LIBS), the collinear femtosecond double-pulse laser configuration is experimentally investigated with different initial sample temperatures using a Ti:sapphire laser. The glass sample is ablated to produce the plasma spectroscopy. During the experiment, the detected spectral lines include two Na(I) lines(589.0 nm and 589.6 nm) and one Ca(I) line at the wavelength of 585.7 nm. The emission lines are measured at room temperature(22 ℃) and three higher initial sample temperatures(T_s?=?100 ℃, 200 ℃, and 250 ℃). The inter-pulse delay time ranges from-250 ps to 250 ps.The inter-pulse delay time and the sample temperature strongly influence the spectral intensity,and the spectral intensity can be significantly enhanced by increasing the sample temperature and selecting the optimized inter-pulse time. For the same inter-pulse time of 0 ps(single-pulse LIBS), the enhancement ratio is approximately 2.5 at T_s?=?200 ℃ compared with that obtained at T_s?=?22 ℃. For the same inter-pulse time of 150 ps, the enhancement ratio can be up to 4 at T_s?=?200 ℃ compared with that obtained at T_s?=?22 ℃. The combined enhancement effects of the different initial sample temperatures and the double-pulse configuration in femtosecond LIBS are much stronger than that of the different initial sample temperatures or the double-pulse configuration only. 相似文献
6.
We investigated the dependence of laser-induced breakdown spectral intensity on the focusing position of a lens at different sample temperatures(room temperature to 300 ℃) in atmosphere.A Q-switched Nd:YAG nanosecond pulsed laser with 1064 nm wavelength and 10 ns pulse width was used to ablate silicon to produce plasma. It was confirmed that the increase in the sample's initial temperature could improve spectral line intensity. In addition, when the distance from the target surface to the focal point increased, the intensity firstly rose, and then dropped.The trend of change with distance was more obvious at higher sample temperatures. By observing the distribution of the normalized ratio of Si atomic spectral line intensity and Si ionic spectral line intensity as functions of distance and temperature, the maximum value of normalized ratio appeared at the longer distance as the initial temperature was higher, while the maximum ratio appeared at the shorter distance as the sample temperature was lower. 相似文献
7.
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
8.
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
9.
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
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.
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
12.
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
13.
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
14.
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
15.
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
16.
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
17.
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
18.
With the rapid advancement of laser decontamination technology and growing awareness of microbial hazards, it becomes crucial to employ theoretical model to simulate and evaluate decontamination processes by laser-induced plasma. This study employs a two-dimensional axisymmetric fluid dynamics model to simulate the power density of plasma bombardment on bacteria and access its decontamination effects. The model considers the transport processes of vapor plasma and background gas molecules. Based on the destructive impact of high-speed moving particles in the plasma on bacteria, we investigate the bombardment power density under various conditions, including different laser spot sizes, wavelengths, plate’s tilt angles, and plate-target spacing. The results reveal that the bombardment power density increases with a decrease in laser spot size and wavelength. For instance, when the plate is parallel to the target surface with a 1 mm spacing, the bombardment power density triples as the laser spot size decreases from 0.8 mm to 0.5 mm and quadruples as the wavelength decreases from 1064 nm to 266 nm. Notably, when the plate is parallel to the target with a relatively close spacing of 0.5 mm, the bombardment power density at 0° inclination increases sevenfold compared to 45°. This simulation study is essential for optimizing optical parameters and designing component layouts in decontamination devices using laser-induced plasma. The reduction of laser spot size, wavelength, plate-target spacing and aligning the plate parallel to the target, collectively contribute to achieving precise and effective decontamination. 相似文献
19.
Aqueous ruthenium was detected in real-time under ambient conditions using microwave-assisted laser-induced breakdown spectroscopy (MW-LIBS). A 10 mJ laser energy and 750 W microwave power were directed at an open liquid jet sample of ruthenium. It was observed that, for liquid flow, the coupling efficiency between the microwave and the laser-induced plasma was limited to 43%. The improvement in the ruthenium's signal-to-noise ratio with MW-LIBS, with respect to LIBS, was 76-fold. Based on MW-LIBS, the limit of detection for aqueous ruthenium was determined to be 957 ± 84 ppb. 相似文献
20.
The effect of the matrix temperature on laser-induced plasma generated in bulk water by using a532 nm pulsed laser beam has been studied.Ca Ⅰ and Ⅱ emission line intensities were recorded for an aqueous solution of CaCl_2 in the temperature range of 7℃-70℃.The emission line intensities did not follow the matrix temperature in our experiments.Maximum intensities were observed at ～18℃ for both lines.Herein,a possible mechanism responsible for the observed variation in intensity is suggested,in which laser-produced bubbles play important roles.Bubble formation is essential to ignite plasma in the liquid and more feasible at the higher liquid temperature.However,the abundant bubbles at the higher temperature can scatter the incident laser beam more effectively to decrease the energy delivered for the laser-induced plasma.Thus,these two roles have effects on the optical emission intensities in opposite ways.The validity of the suggested mechanism is discussed based on the plasma temperature,temperature dependence of the refractive index of water,plasma electron density,scattered light intensity,and plasma ignition threshold energy.Our result indicates that the temperature of the liquid is also an important parameter to be considered in the laser-induced breakdown spectroscopy analysis of bulk liquid samples and its application in deep-sea exploration. 相似文献