Characterization Of Laser-induced Plasma Research Articles

Effect of Femtosecond Ultraviolet and Infrared Laser Wavelength on Plasma Characteristics of Metals, Ceramics and Glass Samples Using Femtosecond Laser-Induced Breakdown Spectroscopy.

In this work, we present studies on the effect of laser wavelengths on the laser-induced plasma characterization using a femtosecond (fs) ytterbium-doped potassium-gadolinium tungstate (Yb:KGW) laser. Plasma plumes of copper, steel, ceramics, and glass samples were induced using a multiple shot of 200 fs laser pulses with 1030 nm and 343 nm wavelengths at fixed laser fluence () and analyzed using the laser-induced breakdown spectroscopy (LIBS) technique. Time-resolved fs-LIBS measurements were performed on the same set of samples and under the same experimental conditions. For the calculation of plasma parameters, the set of spectral lines of Cu(I) (for copper sample), Fe(I) (for steel sample), and Ca(I), K(I) (for glass and ceramics samples) were observed. The plasma electron temperature and density were evaluated from the Boltzmann plots and Stark-broadening profiles of the plasma spectral lines, assuming the local thermodynamic equilibrium condition. Time-resolved plasma temperature and electron density for fs-LIBS using ultraviolet (UV) and infrared (IR) laser wavelengths were analyzed and no significant dependence on fs laser wavelength was observed for any of the samples. However, for all samples the signal-to-noise ratio (SNR) significantly increased using UV laser radiation: copper (), steel (), glass (), and ceramics (). Therefore, by using a fs UV laser wavelength for laser-induced breakdown spectroscopy experiments, for certain materials the SNR and at the same time the limit of detection can be significantly enhanced.

Spectroscopic Diagnostic of Laser-Induced Zn Plasma

The sample's physical characteristics and laser parameters impact the generation and characterization of Laser-Induced Plasma (LIP), which is a relevant phenomenon in many applications. We investigated the effect of laser energy on laser-induced Zn plasma characterization in this study. A Zn plasma with a repeating frequency of 6 Hz, a first wavelength of 1064 nm, a pulse duration of 10 ns, and a laser energy range of 300 mJ to 500 mJ was created using a Q-switched ND: YAG laser. The basic plasma properties, such as electron temperature and density, were estimated using optical emission spectroscopy (OES). The electrons' temperature was measured by the Boltzmann plot method, and the value of the electrons' temperature ranged from 1.6 eV to 2.051 eV in the laser energy range (300-500) mJ. In electron density estimation using the Stark broadening methods, the density value range from 12.75×1017 cm-3 to 19.50×1017 cm-3, in laser energy range (300-500 ) mJ. In addition, various plasma characteristics such as plasma frequency (fp), the number of particles in the Debye sphere (ND), and Debye length (λD) were estimated. We found that laser energy affects every plasma parameter.

Spectroscopic Diagnostics of Spectral Lines Emission from Cu Plasma within the Visible Spectrum Range

The creation and characterization of laser-induced plasma (LIP), a significant phenomenon in several applications, are influenced by the sample’s physical qualities as well as the laser’s parameters. In this research, we created Cu plasma in the atmosphere using an Nd: YAG laser operating at a wavelength of 532 nm with a laser irradiance energy range (400-800) mJ. The effect of the laser’s irradiance energy on the plasma characteristics was investigated using optical emission spectroscopy (OES). Using the two ratio and Stark broadening methods, we successfully measured the two most important plasma properties (electron temperature and electron density). The electron’s plasma temperature value ranged from 2.3 to 3 eV. The value of electron plasma density is in the range from 6.75×1017 to 15×1017 cm−3. Also, we found that other plasma parameters like plasma frequency (fp), particles in the Debye sphere (ND), and Debye length (?D) are affected by laser energy. Where plasma frequency ranged from 7.378 to 10.998×1012 Hz, the Debye sphere ranged from 7.294 to 7.022×103, and the range of Debye length from 1.372 to 1.038×10−5 cm.

Early dynamics of laser-induced plasma and cavitation bubble in water

The knowledge of early laser-induced plasma and cavitation bubble dynamics are of great importance for a better understanding of underwater laser-induced breakdown spectroscopy. In this work, we investigated the temporal evolution of the plasma and bubble at an early stage before 2 μs, by using fast imaging and shadowgraph techniques. It showed that the initial plasma forms at the laser focal point and then grows up toward the incident laser. As time evolves, the plasma expands simultaneously forward and backward to its peripheral region and a sub-plasma structure can be observed at low laser energies. The plasma has a good pulse-to-pulse repeatability during the laser pulse, while soon after the laser pulse (from 20 to 50 ns), it undergoes a severe pulse-to-pulse fluctuation with an inhomogeneous emission distribution. At longer times, the plasma becomes much stable again. To clarify the interrelationship between the bubble dynamics and the plasma characteristics, shadowgraph images of the bubble were shown and compared with the plasma images. It showed that the morphology of the bubble and its evolution have a good consistency with the morphology of plasma. The bubble radius as a function of time can be well expressed by the equation R=at0.4, and a is a constant related to the laser energy. By inspecting the evolution curve of the bubble wall and the bubble pressure calculated based on the Gilmore model, a transition phase from 20 to 50 ns can be identified between the moving breakdown phase and the thermal expansion phase. In this transition phase, both the bubble expansion speed and the bubble pressure drop drastically that may account for the severe plasma fluctuations as observed in this period. These results of early bubble dynamics provide insights into the critical role of bubble-plasma interaction on the characterization of laser-induced plasma in water.

Laser induced plasma characterization in direct and water confined regimes: new advances in experimental studies and numerical modelling

Optimization of the laser shock peening (LSP) and LASer Adhesion Test (LASAT) processes requires control of the laser-induced target’s loading. Improvements to optical and laser technologies allow plasma characterization to be performed with greater precision than 20 years ago. Consequently, the processes involved during laser–matter interactions can be better understood. For the purposes of this paper, a self-consistent model of plasma pressure versus time is required. The current approach is called the inverse method, since it is adjusted until the simulated free surface velocity (FSV) corresponds to the experimental velocity. Thus, it is not possible to predict the behavior of the target under shock without having done the experiments. For the first time, experimental data collected in different labs with the most up-to-date laser parameters are used to validate a self-consistent model for temporal pressure-profile calculation. In addition, the parameters characterizing the plasma (temperature, thickness and duration) are obtained from the ESTHER numerical code, together with the amount of ablated matter. Finally, analytic fits are presented that can reproduce any pressure–temporal profiles in the following domains of validity: intensities, I, ranging from 10 to 500 GW cm−2 and pulse durations, T pul, between 5 and 40 ns for the direct-illumination regime at 1053 nm, I ranging from 1 to 6 GW cm−2 and T pul between 10 to 40 ns in the water-confined regime at 1053 nm, and I from 1 to 10 GW cm−2 and T pul between 7 and 20 ns in the water-confined regime at 532 nm. These temporal pressure profiles can then be used to predict the aluminum target’s behavior under laser shock using mechanical simulation software.

Complementary Characterization of Laser-Induced Plasmas by Optical Emission Spectroscopy and Triple Langmuir Probe

In this article, we study the temporal evolution of the electron density and temperature of carbon laser-produced plasmas (LPP) using a combination of optical emission spectroscopy (OES) and the triple Langmuir probe (TLP) method. OES has been widely used to characterize LPPs but it is limited to distances relatively close to the target. On the other hand, the main advantage of TLP over the single-probe method is that it allows to obtain simultaneous measurements of electron temperature ( $T_{e}$ ) and density ( $N_{e}$ ), without any voltage sweeping. In this article, we compare both techniques; measurements by OES were performed at distances from the target 5 cm. The plasma was generated by focusing nanosecond laser pulses onto a high purity graphite target placed inside a vacuum chamber. Our results show that the values of $T_{e}$ measured using both techniques predict decreasing exponential behavior. $N_{e}$ determined by the spectral line Stark broadening in OES ( 5 cm). This difference in the electron density can be explained by radiative recombination and the presence of different kinds of plasma species detected by the TLP technique. The results show that both methods are complementary and their combination can be used to characterize LPP in a wide range of distances and timescales.

Laser-induced plasma characterization through self-absorption quantification

A self-absorption quantification method is proposed to quantify the self-absorption degree of spectral lines, in which plasma characteristics including electron temperature, elemental concentration ratio, and absolute species number density can be deduced directly. Since there is no spectral intensity involved in the calculation, the analysis results are independent of the self-absorption effects and the additional spectral efficiency calibration is not required. In order to evaluate the practicality, the limitation for application and the precision of this method are also discussed. Experimental results of aluminum-lithium alloy prove that the proposed method is qualified to realize semi-quantitative measurements and fast plasma characteristics diagnostics.

Laser-induced plasma characterization using self-absorption quantification method

Laser-induced breakdown spectroscopy (LIBS) is a well-known analytical technique based on the atomic emission spectroscopy.The elemental composition and relative abundance information can be obtained by analyzing the plasma radiation generated by focusing high-energy pulsed laser on the sample.It has a wide range of applications due to its many advantages,such as minimal-to-no sample preparation,broad applicability,and in-situ capability.But in LIBS,the self-absorption effect of the emitted line can reduce the spectral line intensity,and then affect the precision and accuracy of LIBS quantitative analysis.So there are many methods and researches to reduce or eliminate the adverse effects of selfabsorption on spectral lines.In this paper,a self-absorption quantification analysis method is proposed to characterize the laser-induced plasma quantitative parameters.This self-absorption quantification analysis method,which utilizes the intensity independent information in the self-absorbed spectral lines,is proposed to characterize the induced plasma and perform quantitative measurements.The plasma characteristics including electron temperature,elemental concentration ratio,and absolute species number density can be derived directly through quantifying the self-absorption degree of the analytical spectral lines.Compared with the traditional laser-induced breakdown spectroscopy,the new method is weakly related to the spectral intensity:neither the analysis results are affected by the self-absorption effects,nor the additional spectral efficiency calibration is required.The LIBS spectrum of an aluminum-lithium alloy (nominal weight compositions are Al 94.6%,Mg 1.8%,Li 0.8%,Cu 2.59%,and Mn 0.21%) is used to calculate the spatiallyaveraged electron temperature and the concentration ratio between Mg and Al,and the species number densities is obtained by using the proposed self-absorption quantification method.The results of experiment on aluminum-lithium alloy show that the mean electron temperatures obtained by the modified Saha-Boltzmann plots determined by Mg and Al are 0.96 eV and 0.97 eV,respectively.The weight ratio wMg/wAl in the plasma is calculated to be 0.0171,which is approximately coincident with the nominal value of 0.0169.The absolute singly ionized number density of matrix element Al is 1:65×1017 cm-3,which is comparable to the electron density calculated from the Hα line broadening (1:72×1017 cm-3).Evidently,the free electrons present in the plasma are mainly contributed by the singly ionized matrix element Al.These experimental results of aluminum-lithium alloy validate that the proposed method is qualified to realize accurate absolute quantitative measurements and fast diagnose the plasma characteristics,which verifies the practicability,advantages,and precision of this method.This self-absorption quantification method is of great significance for quantitative LIBS analysis,especially the CF-LIBS analysis.

Characterization of laser-induced plasmas as a complement to high-explosive large-scale detonations

Experimental investigations into the characteristics of laser-induced plasmas indicate that LIBS provides a relatively inexpensive and easily replicable laboratory technique to isolate and measure reactions germane to understanding aspects of high-explosive detonations under controlled conditions. Spectral signatures and derived physical parameters following laser ablation of aluminum, graphite and laser-sparked air are examined as they relate to those observed following detonation of high explosives and as they relate to shocked air. Laser-induced breakdown spectroscopy (LIBS) reliably correlates reactions involving atomic Al and aluminum monoxide (AlO) with respect to both emission spectra and temperatures, as compared to small- and large-scale high-explosive detonations. Atomic Al and AlO resulting from laser ablation and a cited small-scale study, decay within ∼10-5 s, roughly 100 times faster than the Al and AlO decay rates (∼10-3 s) observed following the large-scale detonation of an Al-encased explosive. Temperatures and species produced in laser-sparked air are compared to those produced with laser ablated graphite in air. With graphite present, CN is dominant relative to N2+. In studies where the height of the ablating laser’s focus was altered relative to the surface of the graphite substrate, CN concentration was found to decrease with laser focus below the graphite surface, indicating that laser intensity is a critical factor in the production of CN, via reactive nitrogen.

Characterization of laser-induced plasma during its expansion in air by optical emission spectroscopy: Observation of strong explosion self-similar behavior

We present measurements of the temporal evolution of temperature and electron density in laser-induced plasmas generated in air and on a glass sample at atmospheric pressure. The measurements are made over a wide range of time, from 35ns to 6μs, in order to study the evolution of the plasma. The procedure for selecting the lines suitable for characterization at each stage, based on the evolution of the densities of the ionization states, is discussed. At the initial stage of fast plasma expansion, the temperature and electron density evolve as t−6/5, a result compatible with the self-similar theory for strong explosions in homogeneous atmosphere, according to which the plasma is bounded by a Sedov–Taylor shock wave propagating in the atmosphere. From the experimental results, it is deduced that a change of trend of the cooling mechanism of the plasma from expansion to radiation takes place when the plasma ends its expansion as a shock wave (~0.5μs). The parameters of the plasmas generated in air and on the solid sample are compared.

Laser-induced plasma characterization using line profile analysis of chromium neutral atom and ion transitions

In this paper, line profile analysis of several Cr transitions was carried out for characterization of a laser-induced plasma. The plasma was generated on a metallic alloy (nominal Cr concentration 29.7%) in air at atmospheric pressure by using an infrared Nd:YAG laser. The emission intensities of 24 Cr I lines and 25 Cr II lines were measured spatially integrated along the line-of-sight with good resolution. Their line profiles were analyzed applying a computational fitting algorithm under a framework of a homogeneous plasma in thermodynamic equilibrium. The effects of self-absorption and spatial inhomogeneity were taken into account. The plasma temperature and the parameters Nl (the atom/ion concentration times the length of the plasma along the line-of-sight) were accurately determined, and the electron density was estimated. The results were properly interpreted under the employed approach, demonstrating the important influence of the issues investigated on characterizing the physical state of laser-induced plasmas.

Characterization of Laser-Induced Plasma in Nitrogen

We perform optical and spectroscopic studies of laser-induced plasmas (LIPs) in nitrogen under different experimental conditions. Our aim to determine the characteristics of LIPs associated with laser-ignition applications. The plasma is generated in nitrogen with the help of a 10 Hz and ~ 7 ns Nd:YAG laser operating at 532 nm. We investigate the effects of nitrogen pressure and laser irradiance on the electron temperature and laser-energy-absorption rate by LIPs. The electron temperatures are found almost unchanged from 2.85 to 2.98 eV. The laser-energy-absorption rate by the LIP increases with increase in the laser-pulse energy and nitrogen pressure. Consequently, the laser irradiance and increasing nitrogen pressure improve the plasma-particle density and plasma energy and thus improve the laser-ignition probability.

Characterization of Laser-Induced Plasma of Water Extracted From Orange Juice

Optical emission of laser-induced plasma on the surface of water extracted from fresh orange juices provides sensitive analysis of trace elements. This emergent technique promises applications with expected outcomes in food security or nutrition quality. Characterization of the plasma induced on such samples can represent a method to characterize the quality of soils where the oranges were planted. In this paper, we present the experimental setup and protocol that optimizes the plasma generation on liquid surfaces. We focus particularly on the detection of Ca, Mg, and Na. By way of stallion solutions (CaCl2, MgCl2 and NaCl), we try to determine the concentrations of these elements. We set as samples, oranges coming from Tunisia and Spain.

Characterization of laser-induced plasmas by emission spectroscopy with curve-of-growth measurements. Part I: Temporal evolution of plasma parameters and self-absorption

Laser-induced plasmas have been characterized by emission spectroscopy, including the measurement of curves of growth. The plasmas have been generated in air at atmospheric pressure using an infrared Nd:YAG laser from a set of Fe–Ni alloys with varying Fe concentrations. The procedure used provides, in addition to the apparent temperature T and electron density N e, a parameter N′ l (the atom number density for 100% concentration times the length of the plasma along the line-of-sight), relevant to obtain the self-absorption and the intensity of the emission lines. The temporal evolution of the plasma parameters has been deduced from the measurement and fitting of the curves of growth. A fast temporal decrease of N′ l is obtained for ions, whereas a gradual increase takes place for neutral atoms. The temporal evolution of the line intensity in the optically thin limit and the self-absorption of neutral atom and ion lines have been obtained experimentally and calculated from the evolution of the plasma parameters. The usefulness of the curve-of-growth method in measurements with time integration, in spite of the fast variation of the plasma parameters, has been demonstrated.

Characterization of laser-induced plasmas by emission spectroscopy with curve-of-growth measurements. Part II: Effect of the focusing distance and the pulse energy

Laser-induced plasmas generated with different focusing distances and pulse energies have been characterized by a method based in emission spectroscopy that includes the measurement and calculation of curves of growth. An infrared Nd:YAG laser is used to generated the plasmas from Fe–Ni samples placed in air at atmospheric pressure. The characterization method provides a reduced set of plasma parameters ( N e, T, N′ l, αA) that describe the line emission in optically thin and optically thick conditions. For a pulse energy of 100 mJ, the plasma parameters for varying focusing distances are obtained. The apparent (population averaged) temperatures for neutral atoms and ions are shown to be different in the plasmas generated with all the focusing distances. For each pulse energy (in the range 20–100 mJ), the plasmas generated with the optimum focusing distance, which corresponds to a constant value of irradiance, have been investigated. In these conditions, simple laws have been obtained for the variation of the plasma parameters with the pulse energy E: the electron density N e and the apparent temperature T are independent of E while linear relations with E are obtained for the parameters N′ l, αA. These simple laws lead to a quadratic dependence on E of the line intensities in the optically thin limit and to a variation of the intersection concentration C int that characterizes self-absorption as E − 1 .

Time-resolved spectroscopy and imaging diagnostics of single pulse and collinear double pulse laser induced plasma from a glass sample

The characterization of laser-induced plasma from a glass sample was performed in the single- and double-pulse excitation regimes. The detailed information about density distributions of excited atoms and ions in the expanding plasma was obtained by using the imaging detection system providing measurements of the spatial, temporal, and spectral plasma emission characteristics. The expansion dynamics was shown to differ strongly between two excitation regimes. The enhancement factors of the line emissions in the double-pulse mode were found to be spatial dependent and to differ for the different elements in the plasma plume. The obtained results are useful for a better understanding of the main physical processes leading to the analytical improvement achieved by the use of double-pulse laser-induced breakdown spectroscopy (LIBS).

Characterization of laser-induced plasma in a vacuum using laser ablation mass spectrometry and laser-induced breakdown spectrometry

An analytical system for simultaneously monitoring laser-ablation mass spectra and laser-induced breakdown spectra for solid sample has been developed. The performance of the developed system is evaluated by measuring characteristics of laser-induced plasma such as lifetime of ions inside the plasma and laser power dependence of mass resolution for solid samples. Adopted samples are gadolinium plate, gadolinium coated on stainless steel plate, and one of the NIST standard samples, C-1248 (Ni–Cu alloy). The threshold laser energy in obtaining mass spectrum was dependent on the type of sample characteristics in the order of a few MW/cm 2, while a few hundred MW/cm 2 was necessary in order to observe emission signal. When laser energy was increased enough to produce emission signal, mass resolution of the time-of-flight mass spectrum was severely deteriorated. The lifetime of the continuum ion signal was estimated ∼200 and ∼250 ns for Gd plate and C-1248, respectively, by monitoring emission signals, while the lifetime of ions near sample surface was estimated as ∼400 ns and ∼430 ns for Gd plate and C-1248, respectively. The deterioration of mass resolution can be understood as originating from the space charge effect in high plasma density in a given space and different velocity distribution of ions inside the plasma, while longer lifetime of ions near sample surface can be understood as originating from speed of ion ejection near the sample surface. The details of the characteristics of laser-induced plasma are discussed and optimum experimental conditions for simultaneous monitoring are suggested.