Laser-induced Breakdown Plasma Research Articles

Spatial, spectral, and temporal properties of laser-induced plasma in air near an aqueous solution and comparison with ambient air

Laser-induced breakdown and subsequent plasma are produced in ambient air in the proximity of an aqueous surface using a Nd:YAG Q-switched laser at 1064 nm with a pulse width of 9 ns and a delivered focused input energy of 170 mJ. The distance between the focal point of a 10 cm convex lens and the aqueous surface is 4 mm with laser propagation perpendicular to the surface. Using an intensified CCD camera attached to a 1-m spectrometer, spatial and wavelength-resolved plasma emission data are obtained for delay times after breakdown ranging from 50 ns to 10 μs with a gate window typically 5 ns. Plasma electron density is determined by applying Lorentzian fitting and FWHM extraction to three Stark-broadened spectral lines: N II 3P-3Do multiplet (593.85 nm), Hα (656.27 nm), and the Na D doublet (589.00 and 589.59 nm). One-dimensional spatially resolved measurements of the total emission intensity and electron density are obtained by binning the camera image along the laser axis in intervals of 250 μm and are reported as a function of time from 50 ns to 10 μs. Two plasmas are ignited from a single laser pulse; one from laser breakdown at the water surface and the other a few nanoseconds later from laser-induced air breakdown at the focal point of 4 mm above the water surface. Comparisons between the evolution of the air plasma near and far from the water surface are presented along with data for the water surface plasma itself.

Spectroscopy of Laser-Induced Dielectric Breakdown Plasma in Mixtures of Air with Inert Gases Ar, He, Kr, and Xe.

The generation of ozone and nitrogen oxides by laser-induced dielectric breakdown (LIDB) in mixtures of air with noble gases Ar, He, Kr, and Xe is investigated using OES and IR spectroscopy, mass spectrometry, and absorption spectrophotometry. It is shown that the formation of NO and NO2 noticeably depends on the type of inert gas; the more complex electronic configuration and the lower ionization potential of the inert gas led to increased production of NO and NO2. The formation of ozone occurs mainly due to the photolytic reaction outside the gas discharge zone. Equilibrium thermodynamic analysis showed that the formation of NO in mixtures of air with inert gases does not depend on the choice of an inert gas, while the equilibrium concentration of the NO+ ion decreases with increasing complexity of the electronic configuration of an inert gas.

Ignition Characteristics of Scramjet Combustor with Laser Ablation and Laser-Induced Breakdown

The ignition characteristics of an ethylene-fueled scramjet combustor with a cavity flame holder were experimentally investigated in a Mach 2.92 inflow using laser ablation (LA) and laser-induced breakdown (LIB). For the LA method, a 532 nm Nd:YAG laser was focused directly on the cavity floor composed of stainless steel. Meanwhile, for the LIB method, the laser was focused at 2 mm above the cavity floor to ignite the combustor. Optical techniques, including optical emission spectroscopy, x-ray diffraction, and schlieren imaging, were utilized to analyze the characteristics of the two different laser-induced plasmas. High-speed chemiluminescence imaging was employed to visualize the ignition process by the LA and LIB methods. The LA plasma could successfully ignite the flame at more positions than the LIB plasma with the same laser energy, showing an improved ignition capability due to the higher energy utilization, longer lifetime, and more components with a longer existence time than that of the LIB plasma. The initial flame kernel ignited by the LIB plasma could propagate faster than the LA plasma once the flame is successfully ignited, possibly due to the direct heat convection in the airflow.

Analysis of Metal Elements Contained in Graphite Target Coated With Chinese Medicinal Material Nanoparticles Using LIBS

A nanoparticle-coated graphite target (NCGT) is presented to improve the analysis accuracy and stability of laser-induced breakdown spectroscopy (LIBS). A stable, relatively homogeneous, and close to optically thin laser-induced breakdown plasma was obtained by dispersing sample nanoparticles on a high-purity graphite substrate. Spectral structures dominated by the characteristic lines of carbon and the samples can greatly simplify spectral identification and avoid line interference. To maximize the analysis accuracy and stability, a series of experimental conditions were optimized step by step according to the spectral intensity and signal-to-noise ratio of the lines. Based on the final optimized conditions, the relative standard deviation values of Mg, Fe, and Sr elemental content in Chinese medicinal material (CMM) samples were reduced from 17.7, 16.6, 12.1% of the pressed target to 4.8, 9.5, and 4.5% of the NCGT, respectively. Comparisons with the inductively coupled plasma mass spectrometry (ICP-MS) results demonstrated that the present method has great potential for detection of LIBS.

Fundamental Study on Laser Induced Breakdown Plasma and Engine Ignition

Fundamental Study on Laser Induced Breakdown Plasma and Engine Ignition

Investigation of the laser-induced breakdown plasma, acoustic vibrations and dissociation processes of water molecules caused by laser breakdown of colloidal solutions containing Ni nanoparticles

In this work the process of optical breakdown under laser irradiation by nanosecond pulses with an energy of 650 mJ of aqueous solutions of Ni nanoparticles is investigated. A monotonic change in the number of breakdowns, the average distance between closest breakdowns, the average plasma size of an individual breakdown, the luminosity of a plasma flash, the intensity of acoustic signals, and the rate of formation of dissociation products—O2, H2, OH•, and H2O2 with an increase in the irradiation time was established. With an increase in the concentration of nanoparticles, the measured values change non-monotonically. The maximum luminosity of a plasma flash is observed at a nanoparticle concentration of 109 NP ml−1 and 1010 NP ml−1 and reaches 350 cd m−2. The maximum pressure at the shock front is 1.5–2 MPa at a nanoparticle concentration of 1010 NP ml−1. The maximum rates of generation of O2, H2, OH• and H2O2 are observed at concentrations of 109 NP ml−1 and 1010 NP ml−1. Correlation analysis of the studied physicochemical phenomena shows that the formation of molecular gases is associated with acoustic processes, and the formation of radical products and hydrogen peroxide correlates with the physicochemical properties of plasma.

Laser-induced breakdown in liquid water: Influence of repeated laser pulses on plasma formation and emission

We have experimentally investigated the influence of repeated laser pulses on laser-induced breakdown (LIB) in water following a focused 1064 nm laser pulse, for repetition rates between 0.5 and 20 Hz and up to 100 pulses. LIB plasma image data are collected as a function of repetition rate and laser pulse number, using an intensified CCD camera with sub-nanosecond camera-laser timing. Each pulse induces multiple breakdowns, shockwaves, and macroscopic cavitation bubbles. These effects disappear by the time the next pulse arrives. Even so, we find that the water target retains effects from previous pulses that persist up to roughly a second and that modify subsequent LIB properties including plasma location, spatial extension, and total emission intensity. We quantify the effects by tracking the first moment of the plasma emission intensity, which we call the “center of intensity” (CoI). Three distinct reproducible repetition-rate-dependent phases are identified with repeated pulses. In particular, (1) with initial pulses, emission intensity decreases and the CoI broadens and propagates downstream from the laser focus reaching a maximum axial distance away from the focal point, (2) with additional pulses, the CoI narrows and travels back upstream toward the laser, and (3) with continued pulses, the plasma gains back a portion of the lost intensity and the CoI reaches a steady state position, not at the focal point. Two possible causal effects are highlighted; particle inclusion concentration changes and microbubbles in the laser path.

NO PLIF flow visualization and time-resolved temperature distributions in laser induced breakdown plumes

NO planar laser induced fluorescence (PLIF) is used to obtain images of laser-induced breakdown plasma plumes in NO-seeded nitrogen and dry air at near atmospheric pressure. Single-shot PLIF-images show that the plume development 5–50 μs after the breakdown pulse is fairly reproducible shot-to-shot, although the plume becomes increasingly stochastic on longer timescales, 100–500 μs. The stochastic behavior of the plume is quantified using probability distributions of the loci of the plume boundary. Analysis of the single-shot images indicates that the mixing of the plume with ambient gas on sub-ms time scale is insignificant. The induced flow velocity in the plume is fairly low, up to 30 m s−1, suggesting that laser breakdowns are ineffective for mixing enhancement in high speed flows. The ensemble-averaged PLIF images indicate the evolution of the plume from an initially elongated shape to near-spherical to toroidal shape, with a subsequent radial expansion and formation of an axial jet in the center. Temperature distributions in the plume in air are obtained from the NO PLIF images, using two rotational transitions in the NO(X, v′ = 0 → A, v″ = 0) band, J″ = 6.5 and 12.5 of the QR12 + Q2 branch. The results indicate that the temperature in the plume remains high, above 1000 K, for approximately 100 μs, after which it decays gradually, to below 500 K at 500 μs. The residual NO fraction in the plume is ∼0.1%, indicating that repetitive laser-assisted ignition may result in significant NO-generation. These measured temperature and velocity distributions can be used for detailed validation of kinetic models of laser-induced breakdown and assessment of their predictive capability.

Electrical Conductivity in a Laser Beam Channel

Electrical conductivity in a laser beam channel has been investigated. Oscillations of the conductivity caused by the oscillation motion of electrons in laser-induced breakdown plasma are established in an external electric field. An expression for estimation of charged particle concentration has been obtained.

Temperature measurement with compositional correction of gas mixture based on laser-induced plasma

Laser-induced breakdown plasma was used for gas temperature measurement based on the residual energy of a laser pulse defined as the laser energy detected in the beam path as well as plasma emissions. Gas mixtures with different compositions (O2/N2, O2/CO2, and O2/N2/CO2) were used to simulate the main components of combustion products at different temperatures. First, the correlation of residual energy and gas temperature was investigated, which showed that the residual energy increased with an increase in the gas temperature. The results showed that it also relates to the gas composition, which would affect the characteristics of laser-induced plasma. Then the spectral emission ratio of the plasma (O/N, O/C, and C/N) was obtained simultaneously to correct the compositional effect on the temperature measurement. Finally, the gas temperature with different components can be obtained by the equation coupled with the gas temperature, residual energy, and gas composition. The corrected temperature is consistent with that obtained by thermocouple and the gas temperature measurement error is less than 3.5% in the range from 309 K to 548 K.

Focus on photonics, spectroscopy, and spectrometry

Focus on photonics, spectroscopy, and spectrometry

Research on laser polarization dependence of laser induced breakdown plasma.

Research on laser polarization dependence of laser induced breakdown plasma.

Methods and Devices for Monitoring the Process of Laser Cleaning of Artworks

A method of monitoring the process of laser cleaning of monuments and other works of art in the course of conservation is presented. The capabilities of the method of laser-induced breakdown plasma spectroscopy in cleaning of monuments made of metal are considered. A photometric device based on an integrating cavity in the form of a cylinder is developed and investigated. The capabilities gained with the use of the device for proximate analysis of the efficiency of the process of cleaning the surfaces of sculpture made of marble and limestone structures are shown.

Polarization investigation of laser-induced breakdown plasma emission from Al, Cu, Mo, W, and Pb elements using nongated detector

The polarization of plasma emission produced by ablation of Al, Cu, Mo, W, and Pb elements with nanosecond (ns)-laser pulses is explored in the air. A comparison of polarized plasma emission of these metal elements exhibits that the polarization degree increases with increasing the atomic number of elements. It is shown that plasma emission is polarized with no difference between polarization degree of discrete and continuum emission. No improvement in signal to background ratio was found to support the efficiency of polarization resolved laser-induced breakdown method without temporal gating. The estimated collision times of electron-electron and electron-ions ruled out the possibility of highly anisotropic electron distribution function as a case of observed polarization. The polarization due to Fresnel reflection for these elements as a function of wavelengths gives no agreement with the corresponding experimental measurements. In our opinion, polarization emission of laser-induced breakdown plasma may be due to the residual fluctuations from the anisotropic recombining plasma at early stages of the plasma formation and perhaps dynamic polarizability of the core. The enhancing behavior of polarization degree with increasing atomic number reinforces the possibility of the dynamic polarization of a core as a reason of observed polarized radiation in ns-laser-induced breakdown spectroscopy.

Optimization of experimental parameters about laser induced breakdown and measurement of soil elements

The experimental parameters for observing the characteristic of laser induced breakdown (LIB) plasma are optimized in the atmospheric environment. It shows that when the laser pulse energy is 21 mJ, the focal length of lens is 15 cm and the sample is 2 mm in front of the lens focus, the spectral intensity and the ratio of signal to noise (SBR) of LIB plasma are highest. It is helpful to improve the detection accuracy of the technique of laser induced breakdown spectroscopy (LIBS). The LIB spectra of a special soil samples are observed with the optimized parameters. The elements Fe, Mn, Ca, W, Co, Ti, Si, Cr and V contained in the soil sample are determined based on the spectral peaks. The electron temperature in plasma and the quantities of Mn, Ca in the soil are obtained further.

Time-resolved optical probing of nanosecond laser-induced breakdown plasma in polymethyl methacrylate (PMMA)

In this paper, laser-induced optical breakdown in a transparent dielectric was studied by pump–probe beam method. The breakdown was induced by Nd:YAG nanosecond laser beam in polymethyl methacrylate (PMMA). The main laser beam was separated by a splitter and used as probe beam. An appropriate optics used to direct the probe beam passing through the breakdown region perpendicularly to the pump laser beam. Using fast photodiodes and oscilloscope, the transmitted/ reflected signals (associated with the probe/ pump beam) were monitored. Analyzing these signals can be used to describe the breakdown process. The results show that the dynamics of transmissivity and reflectivity of the produced plasma depend on the pump laser intensity.

Temporal and Spectral Characterization of Breakdown Plasma Induced by Laser Radiation in Colloidal Solutions of Gold Nanoparticles

Temporal and spectral characteristics of laser-induced breakdown plasma in colloidal solutions of gold nanoparticles were experimentally studied. Near-infrared laser sources of nanosecond pulses were used. It was shown that under certain experimental conditions nanosized plasma around nanoparticles might change to laser-induced breakdown plasma in liquid. The dependencies of the plasma temporal and spectral characteristics on laser pulse duration as well as resulting nanoparticles properties were studied. Laser-induced breakdown plasma lifetime was shown to be comparable with laser pulse duration. The efficiency of gold nanoparticles fragmentation was shown to depend on laser pulse duration. Similar experiments were carried out under reduced external pressure. It turned out to affect the properties of both plasma plume and nanoparticles. Transmission electron microscopy and disc measuring centrifuge were used for nanoparticle morphology and size analysis. Extinction spectra of colloidal solutions and emission spectra of plasma were studied by means of optical spectroscopy.

Two-dimensional Observation of Surface Layer Formed on Chemically-treated Aluminum Alloy Using Laser-induced Breakdown Plasma Optical Emission Spectrometry with Scanning Laser Beam

Two-dimensional Observation of Surface Layer Formed on Chemically-treated Aluminum Alloy Using Laser-induced Breakdown Plasma Optical Emission Spectrometry with Scanning Laser Beam

Atomic and molecular LIBS spectra of Al alloys and composite materials for nanosecond and microsecond excitation

Spectral investigations in the UV-VIS range of selected Al alloys and composites, used in the construction of armament components as well as drones, were performed using LIBS technique. Two Nd:YAG lasers were applied: a short pulse 4 ns 60 mJ laser and a long pulse 200/400 (up to 1000) us (~ 2/4 up to 10 J) laser. In experiments with a short laser pulse only atomic spectra were observed while for long pulses, also molecular transitions have been recorded. Electron temperatures of created plasma were found on the base of Boltzmann law. Temperatures are clearly higher for short pulse excitation. Full Text: PDF ReferencesA. Miziolek, V. Palleschi and I. Schechter, Laser-Induced Breakdown Spectroscopy (Cambridge, Cambridge University Press 2006). CrossRef M. Sabsabi and P. Cielo, "Quantitative Analysis of Aluminum Alloys by Laser-Induced Breakdown Spectroscopy and Plasma Characterization", Appl. Spectrosc. 49, 499 (1995). CrossRef D.L. Death, A.P. Cunningham, and L.J. Pollard, "Multi-element analysis of iron ore pellets by Laser-induced Breakdown Spectroscopy and Principal Components Regression", Spectrochim. Acta B, 63, 763 (2008). CrossRef S. Laville, M. Sabsabi and F. Doucet, "Multi-elemental analysis of solidified mineral melt samples by Laser-Induced Breakdown Spectroscopy coupled with a linear multivariate calibration", Spectrochim. Acta B, 62, 1557 (2007), CrossRef D.M. Surmick, C.G, Parigger, "Aluminum Monoxide Emission Measurements in a Laser-Induced Plasma", Applied Spectroscopy, 2015, V.68, No.9, P.992-996. CrossRef J.B. Sirven, B. Bousquet, L. Canioni and L. Sarger,"Laser-Induced Breakdown Spectroscopy of Composite Samples: Comparison of Advanced Chemometrics Methods", Anal. Chem. 78, 1462 (2006). CrossRef E.J. Judge, G. Heck, E.B. Cerkez and R. J. Levis, "Discrimination of Composite Graphite Samples Using Remote Filament-Induced Breakdown Spectroscopy", Anal. Chem. 81, 2658 (2009). CrossRef L.M. Cabalin and J.J. Laserna, "Experimental determination of laser induced breakdown thresholds of metals under nanosecond Q-switched laser operation", Spectrochim. Acta B, 53, 723 (1998). CrossRef T.A. Labutin, A.M. Popov, V.N. Lednev and N.B. Zorov, "Correlation between properties of a solid sample and laser-induced plasma parameters", Spectrochim. Acta B, 64, 938 (2009). CrossRef J.S. Cowpe, R.D. Moorehead, D. Moser, J.S. Astin, and S. Karthikeyan, "Hardness determination of bio-ceramics using Laser-Induced Breakdown Spectroscopy", Spectrochim. Acta B, 66, 290 (2011). CrossRef G. Cristoforetti, , S. Legnaioli, V. Palleschi, A. Salvetti, and E. Tognoni, "Effect of target composition on the emission enhancement observed in Double-Pulse Laser-Induced Breakdown Spectroscopy", Spectrochim. Acta B, 63, 312 (2008). CrossRef

Enhancement of Laser-Induced Breakdown Spectroscopic Signals in a Liquid Jet with Glow Discharge.

In this work, emission signals of laser-induced breakdown (LIBS) plasma of a flowing liquid jet in the absence and presence of an air-supported glow discharge have been investigated. In combination with a needle-to-needle glow discharge, a Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (1064 nm, 5 ns) with power density ∼1010 W/cm2 was used to generate a plasma from a liquid jet. Emission lines of Mg, Ca, Al, Li, Na, and K all showed significant enhancements in the presence of the glow discharge. Lower continuum background was also observed. Mechanisms of the line emission enhancement and continuum radiation reduction were discussed.