Aluminium beverage can; Life Cycle Assessment; Recycling; Solid state recycling; Laser induced breakdown spectroscopy; Abiotic resource depletion;LIFE-CYCLE ASSESSMENT; IMPACT ASSESSMENT; ALLOY SCRAP; WASTE; ECONOMY; SYSTEMS; LOOP; METHODOLOGY; COLLECTION; MANAGEMENT

It is undisputed that the recycling of aluminium is desirable as long as the environmental and economic implications of its reintegration do not exceed the burdens of its primary production. The efficiency of any aluminium recycling system can be expressed by the total material losses throughout the entire process chain, ideally reaching 0%, thus equivalent to 100% metal recovery. However, in most cases metals are recycled in open/cascade recycling loop where dilution and quality losses occur. Innovations in aluminium beverage can (ABC) design as well as in sorting and recycling technologies have the potential to increase recyclability and avoid downcycling issues due to mixed alloy scrap streams. By means of Life Cycle Assessment (LCA) seven scenarios, comprising specific systemic changes, are compared to the current recycling practice of the used beverage can in the UK. The End-of-Life modelling of recycling is performed in accordance with the equal share method to account for impacts both on the recyclability and the recycled content. The results confirm the primary aluminium production and energy consumption in the ABC production as the hotspots in the life cycle of the ABC. The toxicity and energy-related impact categories show the highest susceptibility to increasing recycled content and recycling rate, while the technological novelties show little effect. In terms of abiotic resource depletion the introduction of novel technologies could have the potential to retain quality of the aluminium alloys by either establishing dedicated waste streams or upgrading the aluminium scrap by dedicated sorting strategies.

INDUCED BREAKDOWN SPECTROSCOPY; STAINLESS-STEEL; PROPAGATION; REMOVAL; MEDIA

High Energy Lasers (HELs) used for defense applications require operational distances ranging from few hundred meters to several kilometers. As the distance increases, the incident beam properties and, consequently, the anticipated effect delivered to the sample become less predictable. Therefore, the direct observation of the event induced by the laser can become an asset. In this paper, we propose a novel spectroscopic method that analyses in real time the spectral components present in the flames produced during the interaction of a HEL with a metallic piece at a long distance. This method was used on aluminum and carbon steel samples placed 200 m away from the laser system. It was discovered that the aluminum and iron oxides created as a by-product of the HEL reaction with the samples emitted clear fingerprint signatures that could be detected remotely using a spectroscopic receiver placed beside the HEL beam director. The real-time assessment of the laser-induced effect can be achieved by monitoring the temporal evolution of the oxide signatures, hence providing information to the operator about the reaction and the nature of the sample illuminated.

LIBS; Water; Hydrogen; ChemCam; Mars; Low pressure; Roughness;CHEMCAM INSTRUMENT SUITE; QUANTITATIVE-ANALYSIS; INDUCED DESORPTION; SOLID-SURFACES; INDUCED PLASMA; LOW-PRESSURES; GALE CRATER; MARS; CONFINEMENT; IMPROVEMENT

On Mars, Laser-Induced Breakdown Spectroscopy CUBS) as performed by the ChemCam instrument can be used to measure the hydrogen content of targets in situ, under a low pressure CO2 atmosphere. However, unexpected variations observed in the Martian dataset suggest an effect related to target roughness. Here, we present a series of laboratory experiments that reproduce the effect observed on Mars and explore possible causes. We show that the hydrogen peak intensity increases significantly with increasing exposure of the target surface to the LIBS plasma, and that these variations are specific to hydrogen, as other emission lines in the spectra are not affected. The increase of the signal could be related to an addition of hydrogen to the plasma due to interaction with the surrounding target surface, yet the exact physical process to explain such effect remains to be identified. More generally, this effect should be taken into account for the quantification of hydrogen in any LIBS applications where the roughness of the target is significant. (C) 2017 Elsevier B.V. All rights reserved.

INDUCED BREAKDOWN SPECTROSCOPY; INDUCED ALUMINUM PLASMA; FEMTOSECOND LASER; ISOTOPIC SPECTROMETRY; TEMPORAL EVOLUTION; EMISSION-SPECTRA; ABLATION; ALO; DYNAMICS; CARBON

Measurements with Laser Ablation Molecular Isotopic Spectrometry (LAMIS) are usually performed in atmosphere for rapid isotope analysis, and an understanding of molecule formation via plasma-air chemical reactions is important for quantitative analysis by LAMIS. In this work, the expansion of a plasma plume from ablation of pure aluminum in air is studied with time-and space-resolved monochromatic imaging and emission spectroscopy. The distributions of neutral Al and O atoms and AlO radicals formed through plasma chemical reactions are characterized. The emission spectra of the AlO bands of a B-2 Sigma(+)-X-2 Sigma(+) system are recorded and the rotational-vibrational temperature was obtained through fitting experimental spectra. Inter-molecular vibrational band interference is well reconstructed, and self-absorption of bandheads, especially for the (0-0) band, is corrected. Interpretation of the spatial-temporal evolutions of plasma species and plasma temperature provides insights into the formation mechanism of AlO radicals in laser-induced plasma.

MOLECULAR ISOTOPIC SPECTROMETRY; MASS-SPECTROMETRY; AB-INITIO; EMISSION-SPECTRA; ALO; AL2O; ABSORPTION; CHEMISTRY; SURFACE; SYSTEM

Identification of chemical intermediates and study of chemical reaction pathways and mechanisms in laser-induced plasmas are important for laser-ablated applications. Laser-induced breakdown spectroscopy (LIBS), as a promising spectroscopic technique, is efficient for elemental analyses but can only provide limited information about chemical products in laser-induced plasmas. In this work, time-resolved resonance fluorescence spectroscopy was studied as a promising tool for the study of chemical reactions in laser-induced plasmas. Resonance fluorescence excitation of diatomic aluminum monoxide (AlO) and triatomic dialuminum monoxide (Al2O) was used to identify these chemical intermediates. Time-resolved fluorescence spectra of AlO and Al2O were used to observe the temporal evolution in laser-induced Al plasmas and to study their formation in the Al-O-2 chemistry in air. (C) 2017 Optical Society of America

EMISSION-LINES; ALUMINUM; PLASMAS; COAL

A novel self-absorption-free laser-induced breakdown spectroscopy (SAF-LIBS) technique is proposed to directly capture the optically thin spectral line by matching the measured doublet atomic lines intensity ratios with the theoretical one. To realize the experimental SAF-LIBS, the integration time, the fiber collection angle, and the delay time are optimized. The optically thin conditions are validated by comparing the linearity of Boltzmann plots with the traditional self-absorption (SA) correction method and evaluating the SA coefficients. The applicability and limitation of SAF-LIBS on element concentration and laserenergy are also discussed. Univariate quantitative analysis results show that, compared with ordinary LIBS, the average absolute error of aluminum concentration has been reduced by an order of magnitude, which proves that this SAF-LIBS technique is qualified to realize accurate chemical composition measurements. (C) 2017 Optical Society of America

INDUCED BREAKDOWN SPECTROSCOPY; EMISSION-SPECTROSCOPY; MOLECULAR-EMISSION; ABLATION; AIR; CARBON; ALO; TEMPERATURE; GENERATION; CHEMISTRY

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 similar to 10(-5) s, roughly 100 times faster than the Al and AlO decay rates (similar to 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 N-2(+). 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. (C) 2017 Author(s).

Laser ablation (LA); Laser induced fluorescence (LIF); Laser-induced breakdown spectroscopy (UBS); Plasma chemistry; Combustion;INDUCED BREAKDOWN SPECTROSCOPY; EXCITED ATOMIC FLUORESCENCE; INDUCED ALUMINUM PLASMA; SELECTIVE EXCITATION; URANIUM; ALO; SOLIDS; SPECTROMETRY; EVOLUTION; DYNAMICS

Oxygen present in the ambient gas medium may affect both laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) emission through a reduction of emission intensity and persistence. In this study, an evaluation is made on the role of oxygen in the ambient environment under atmospheric pressure conditions in LIBS and laser ablation (LA)-LIF emission. To generate plasmas, 1064 nm, 10 ns pulses were focused on an aluminum alloy sample. LIF was performed by frequency scanning a CW laser over the 396.15 nm (3s(2)4s S-2(1/2) -> 3s(2)3p P-2 degrees(3/2)) Al I transition. Time-resolved emission and fluorescence signals were recorded to evaluate the variation in emission intensity caused by the presence of oxygen. The oxygen partial pressure (p(o)) in the atmospheric pressure environment using N-2 as the makeup gas was varied from 0 to 400 Torr O-2. 2D-fluorescence spectroscopy images were obtained for various oxygen concentrations for simultaneous evaluation of the emission and excitation spectral features. Results showed that the presence of oxygen in the ambient environment reduces the persistence of the LIBS and LIF emission through an oxidation process that depletes the density of atomic species within the resulting laser-produced plasma (LPP) plume. (C) 2017 Elsevier B.V. All rights reserved.

Long pulse; dual-pulse laser-induced breakdown spectroscopy; DP-LIBS; enhancement; plasma temperature stabilization; underwater measurement;CO2-LASER PULSE; AMBIENT GAS; ABLATION; ENHANCEMENT; PRESSURES; FEASIBILITY; MAGNESIUM; DISCHARGE; SPECTRUM; LIQUIDS

Collinear long and short dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) was employed to clarify the emission characteristics from laser-inducedplasma. The plasma was sustained and became stable by the long pulse-width laser with the pulse width of 60s under free running (FR) conditions as an external energy source. Comparing the measurement results of stainless steel in air using single-pulse LIBS (SP-LIBS) and DP-LIBS, the emission intensity was markedly enhanced using DP-LIBS. The temperature of plasma induced by DP-LIBS was maintained at a higher temperature under different gate delay time and short pulse-width laser power conditions compared with those measured using short SP-LIBS. Moreover, the variation rates of plasma temperatures measured using DP-LIBS were also lower. The superior detection ability was verified by the measurement of aluminum sample in water. The spectra were clearly detected using DP-LIBS, whereas it cannot be identified using SP-LIBS of short and long pulse widths. The effects of gate delay time and short pulse-width laser power were also discussed. These results demonstrate the feasibility and enhanced detection ability of the proposed collinear long and short DP-LIBS method.

INDUCED BREAKDOWN SPECTROSCOPY; DUAL PULSE EXCITATION; BEAM-DEFLECTION; SINGLE-PULSE; WATER; UNDERWATER; SPECTRA; NANOMATERIALS; SCATTERING; INTERFACE

In this work, the impact of the cavitation bubble on a plasma emission produced after the interaction of the strong focused laser radiation with the target in the liquid was studied. Several experimental techniques were applied to assess different aspects of the complex phenomena of the laser induced breakdown in the liquid media. The results of the fast photography, Schlieren and shadowgraphy techniques were compared with the results of simpler probe beam techniques, transmission and scattering. In addition, emission from the plasma was analysed using optical emission spectroscopy, with aim to relate the quality of the recorded spectral lines to the bubble properties. Bubble had proved to be more convenient surrounding than the liquid for the long lasting plasma emission, due to the high temperature and pressure state inside of it and significantly lower density, which causes less confined plasma. Changes in refractive index of the bubble were also monitored, although in the limited time interval, when the bubble was sufficiently expanded and the refractive index difference between the bubble and the water was large enough to produce glory rings and the bright spot in the bubble's centre. Reshaping of the plasma emission due to the optical properties of the bubble was detected and the need for careful optimization of the optical system was stressed.

INDUCED BREAKDOWN SPECTROSCOPY; SELF-ABSORPTION; EMISSION-LINES

The temporal evolution of doublet lines intensity ratio, plasma temperature (T) and electron density (N-e) of different radial parts of aluminum plasma as well as the relationship between optically thin condition and plasma characteristics are investigated. With respect to doublet lines intensity ratio, the optimal delay time (t(ot)) when the plasma is optically thin is determined by comparing the experimental intensity ratio of doublet Al(I) lines with the theoretical value. The optimal integration time, fiber collection angle, and delay time corresponding to the optically thin condition are 400 ns, 45 degrees, and 500 ns, respectively, in which case the linearity of the calibration curve reaches 0.98, enabling more accurate composition measurements. The maximum temperature values are reached within 300 ns at 10 degrees, 30 degrees, 45 degrees, and 80 degrees, but after 900 ns at 55 degrees, 60 degrees, and 70 degrees. Combined with the morphologic image of the plasma, we infer that the time at which a radial part of plasma reaches the highest temperature is related to the extent of its expansion. It is generally understood that the faster the radial part of plasma expands, the sooner the temperature reaches its maximum. The radial part of plasma may not be optically thin when the corresponding temperature reaches its maximum. If the highest temperature is obtained earlier, the optically thin condition is likely to appear in the descending stage of the temporal evolution curve of temperature. Otherwise, it may appear in the ascending stage. There seems to be no simple positive correlation between electron density and optically thin condition.

INDUCED BREAKDOWN SPECTROSCOPY; SINGLY IONIZED ALUMINUM; DUAL PULSE EXCITATION; EXPANSION DYNAMICS; ELEMENTAL ANALYSIS; ABLATION PLUME; GENERATION; EMISSION; UNDERWATER; LIQUID

We report on the findings of double-pulse studies performed on an aluminium target submerged in water using Nd: YAG laser pulses. Shadowgraphy measurements were performed to examine the dynamic behaviour of the cavitation bubble that eventually forms some considerable time post-plasma ignition. These measurements were used to inform subsequent investigations designed to probe the bubble environment. The results of time-resolved imaging from within the cavitation bubble following irradiation by a second laser pulse reveal the full dynamic evolution of a plasma formed in such an environment. Rapid displacement of the plasma plume in a direction normal to the target surface followed by a diffusive outwards expansion is observed and a qualitative model is proposed to explain the observed behaviour. Line profiles of several ionic and atomic species were observed within the irradiated cavitation bubble. Electron densities were determined using the Stark broadening of the Al II line at 466.3 nm and electron temperatures inferred using the ratio of the Al II (466.3 nm) and Al I (396.15 nm) lines. Evidence of self-reversal of neutral emission lines was observed at times corresponding to growth and collapse phases of the cavitation bubble suggesting high population density for ground state atoms during these times.

Laser-induced breakdown spectroscopy; LIBS; long-wave infrared spectra; explosives;ARRAY DETECTION SYSTEM; ENERGETIC MATERIALS; SPECTRA; PHASE; ACID; HMX

Thin solid films made of high nitro (NO2)/nitrate (NO3) content explosives were deposited on sand-blasted aluminum substrates and then studied using a mercury-cadmium-telluride (MCT) linear array detection system that is capable of rapidly capturing a broad spectrum of atomic and molecular laser-inducedbreakdown spectroscopy (LIBS) emissions in the long-wave infrared region (LWIR; similar to 5.6-10 mm). Despite the similarities of their chemical compositions and structures, thin films of three commonly used explosives (RDX, HMX, and PETN) studied in this work can be rapidly identified in the ambient air by their molecular LIBS emission signatures in the LWIR region. A preliminary assessment of the detection limit for a thin film of RDX on aluminum appears to be much lower than 60 mg/cm(2). This LWIR LIBS setup is capable of rapidly probing and charactering samples without the need for elaborate sample preparation and also offers the possibility of a simultaneous ultraviolet visible and LWIR LIBS measurement.

DP-LIBS; Double-ionized Al spectral lines; Electron impact excitation coefficient; De-excitation rate coefficients for Al ions;ABLATION; SINGLE; ATOMS; FIELD

We built a collinear dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) system to study the aluminum (Al) plasma emission by installing a pair of Nd: YAG lasers operating at 266 and 1064 nm. The spectral intensities of selected aluminum doubly-ionized lines were employed to evaluate the optical emission spectra. The influences of the energy ratio of two pulsed lasers on the LIBS intensity for different Al doubly-ionized spectral lines were investigated. The de-excitation rate parameters of the excited ion and the electron impact excitation were computed using the analytical formulas proposed by Smeets and Vriens. The transition probabilities and energy states were computed using Hibbert's configuration interaction, computer package (CIV3). By solving the coupled rate equations including 1s(2)2s(2)2p(6)ns (S-2), 1s(2)2s(2)2p(6)np (P-2), 1s(2)2s(2)2p(6)nd (D-2) (n = 3-5) and 1s(2)2s(2)2p(6)nf (F-2) (n = 4, 5) states, the level population densities were computed. We also proposed a theoretical population model in order to investigate the effectiveness of the various processes that might affect the population of the upper levels in Al plasma by using the rate coefficients. In addition, the population densities for the 19 upper levels were also computed. Good compatibility between the experimental and the theoretical model data had been observed. Our results might be significant as reference data for the optimization of the DP-LIBS spectrometry and diagnostics of laser produced plasmas.

INDUCED BREAKDOWN SPECTROSCOPY; MOLECULAR ISOTOPIC SPECTROMETRY; LASER-INDUCED PLASMA; SECONDARY EXCITATION SOURCE; PRESSURE GLOW-DISCHARGE; OPTICAL-EMISSION; STEEL ANALYSIS; LINE LISTS; BANDS; QUANTIFICATION

Enhancement of the emission intensity by a secondary electric pulse following a laser ablation pulse was investigated in application to the chemical analysis by Laser-Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Molecular Isotopic Spectrometry (LAMIS). A stable reheating pulsed discharge presumably sustained in a diffuse glow regime at atmospheric pressure was demonstrated as a rational approach to increase the sensitivity of the optical emission analysis over the conventional single-pulse laser ablation techniques. The enhancement in the emission intensity was illustrated by several examples of both atomic (Ca, Na) and molecular (OH, AlO, CaF) emission in LIBS and LAMIS, respectively. Especially large emission enhancement was realized for isotopologues (OH)-O-16, (OH)-O-18 and (OD)-O-16 at the transition A(2)Sigma(+)/X-2 Pi(i) (1-0) with clearly resolved lines of their rotational branches. An increase in rotational temperature from 3370 to 4560 K was measured subsequently to the reheating of plasma by a pulsed electric discharge. Such reheating can be especially useful for the minimally destructive analysis, chemical mapping and depth profiling by LIBS. Enhancement in the emission intensity of CaF can be used for further reduction of the detection limits in fluorine determination. A brief review of the earlier publications on the cross-excitation by an electric pulse after laser ablation is provided and a comparison is made to the similar reheating of the ablation plasma in double-pulse LIBS.

Double pulse laser ablation; Laser induced phase explosion; Plasma expansion; Pre plasma formation; Single pulse laser ablation; Water interaction ambient;INDUCED BREAKDOWN SPECTROSCOPY; PHASE-EXPLOSION; NANOSECOND; METALS; PLASMA; ENHANCEMENT; THRESHOLDS

In this paper, single pulse and double pulse laser ablation of an aluminum target in two interaction ambient was investigated experimentally. The interaction was performed by nanosecond Nd:YAG laser beam in air and four depths (i.e. 9, 13, 17, and 21 mm) of distilled water ambient. The irradiation was carried out in single and collinear double pulse configurations in both air and liquid ambient. Crater geometry (depth and diameter) was measured by an optical microscope. The results indicated that the crater geometry strongly depends on both single pulse and double pulse configurations and interaction ambient. In single pulse regime, the crater diameter is higher for all water depths compared to that of air. However, the crater depth, depend on water depth, is higher or lower than the crater depth in air. In double pulse laser ablation, there are greater values for both crater diameters and crater depths in the water. (C) 2016 Elsevier B.V. All rights reserved.

Double-pulse laser ablation; Molecular dynamics; Hydrodynamics; Crater depth; Plume reheating;INDUCED BREAKDOWN SPECTROSCOPY; SIGNAL ENHANCEMENT; MOLECULAR-DYNAMICS; METAL TARGETS; SPALLATION; SINGLE

We elaborated two numerical methods, two-temperature hydrodynamics and hybrid two-temperature molecular dynamics, which take into account basic mechanisms of a metal target response to ultra short laser irradiation. The model used for the description of the electronic subsystem is identical for both approaches, while the ionic part is defined by an equation of state in hydrodynamics and by an interatomic potential in molecular dynamics. Since the phase diagram of the equation of state and corresponding potential match reasonably well, the dynamics of laser ablation obtained by both methods is quite similar. This correspondence can be considered as a first step towards the development of a self consistent combined model. Two important processes are highlighted in simulations of double-pulse ablation: (1) the crater depth decrease as a result of recoil flux formation in the nascent plume when the delay between the pulses increases; (2) the plume reheating by the second pulse that gives rise to two three-fold growth of the electron temperature with the delay varying from 0 to 200 ps. (C) 2016 Published by Elsevier B.V.

plasma parameter; laser induced plasma; plasma electron density; Saha-Boltzmann method; Stark broadening method;INDUCED BREAKDOWN SPECTROSCOPY; SPECTROCHEMICAL ANALYSIS; ALUMINUM-ALLOYS; SOLID SAMPLES; ABLATION; LINES; EMISSION; PARAMETERS; TEMPERATURE; LIBS

We report spectroscopic studies on plasma electron number density of laser-induced plasma produced by ns-Nd: YAG laser light pulses on an aluminum sample in air at atmospheric pressure. The effect of different laser energy and the effect of different laser wavelengths were compared. The experimentally observed line profiles of neutral aluminum have been used to extract the excitation temperature using the Boltzmann plot method, whereas the electron number density has been determined from the Stark broadened as well as using the Saha-Boltzmann equation (SBE). Each approach was also carried out by using the Al emission line and Mg emission lines. It was observed that the SBE method generated a little higher electron number density value than the Stark broadening method, but within the experimental uncertainty range. Comparisons of N-e determined by the two methods show the presence of a linear relation which is independent of laser energy or laser wavelength. These results show the applicability of the SBE method for N-e determination, especially when the system does not have any pure emission lines whose electron impact factor is known. Also use of M-g lines gives superior results than Al lines.

chemometrics; ion recombination; laser-induced breakdown spectroscopy; LIBS; MCR-ALS; mean field-independent components analysis; MFICA; molecular formation; multivariate curve resolution-alternating least squares; temporal evolution;ARTIFICIAL NEURAL-NETWORKS; QUANTITATIVE-ANALYSIS; TEMPORAL EVOLUTION; WAVELET-TRANSFORM; ABSORPTION-SPECTROSCOPY; ANALYTICAL-CHEMISTRY; CHEMOMETRIC METHODS; LIBS; IDENTIFICATION; OPTIMIZATION

Laser-induced breakdown spectroscopy (LIBS) is an analytical technique allowing the determination of elemental concentrations in a variety of matrices in the solid, liquid, and gaseous phases. Because of the inherent complexity of the signal and to the high dimensionality of experimental data, chemometrics has been more and more applied in LIBS to perform samples identification or quantitative measurements. But multivariate methods can also be used for the description and physical interpretation of the plasma, particularly to exploit the temporal dimension of the LIBS signal, which is usually neglected in spectrochemical measurements. In this work, time-resolved spectra of a pure aluminum sample were treated with 2 methods, mean field-independent components analysis and multivariate curve resolution-alternating least squares, applying non-negativity constraints for scores and components in both cases. Results obtained were compared with reference univariate measurements of the emission of the species of interest (ions, neutral atoms, and molecules). The interpretation of scores and components provided a physical description of phenomena that take place between species in the plasma, like ionic recombination and molecules formation. Overall, mean field-independent components analysis and multivariate curve resolution-alternating least squares yield equivalent solutions with our dataset. This new approach is very promising for the treatment of time-resolved data obtained by LIBS.

SINGLE; INSTRUMENT; LIBS

This paper reports the development of a compact double-pulse laser system to enhance laser induced breakdown spectroscopy (LIBS) for field applications. Pumped by high-power vertical-surface emitting lasers, the laser system that produces 16 ns pulse at 12 mJ/pulse with total weight less than 10 kg is developed. The inter-pulse delay can be adjusted from 0 mu s with 0.5 mu s increment. Several LIBS experiments were carried out on NIST standard aluminum alloy samples. Comparing with the single-pulse LIBS, up to 9 times enhancement in atomic emission line was achieved with continuum background emission reduced by 70%. This has led to up to 10 times improvement in the limit of detection. Signal stability was also improved by 128% indicating that a more robust and accurate LIBS measurement can be achieved using a compact double-pulse laser system. This paper presents a viable and field deployable laser tool to dramatically improve the sensitivity and applicability of LIBS for a wide array of applications. Published by AIP Publishing.

Stimulated Raman; Laser-induced breakdown; Pulses laser; The fluorescence lifetime;STIMULATED RAMAN-SCATTERING; MATERIAL REMOVAL; ENHANCEMENT; EMISSION; SINGLE

To study the time evolution characteristics of plasma fluorescence, aluminum feature spectrum was measured and analyzed through dual-pulse laser-inducedbreakdown spectroscopy in the standard ambient temperature and pressure experimental conditions. Two Nd:YAG lasers were used to perform the experiment; one laser ablated the target, and the other reheated the plasma in air. The plasma emission intensity was enhanced at an optimal inter-pulse delay time of 200 ns. The plasma fluorescence lifetime was measured in a dual-pulse laser excitation mode at different inter-pulse delays. The plasma fluorescence lifetime changed with the changing of inter-pulse delay under double pulse excitation. The results can further understand of the time evolution of the plasma under double-pulse laser excitation. (C) 2017 Elsevier GmbH. All rights reserved.

QUANTITATIVE-ANALYSIS; WASTE-WATER; SURFACE; ABLATION; DROPLET; LIBS; SUBSTRATE; SODIUM; DIESEL; OIL

Droplets of organic liquids on aluminum substrate were probed by an Nd:YAG laser, both in a steady state and during rotation at speeds 18-150 rpm. Rotation transforms the droplet into film, which estimated thickness at high speeds was below 3 mu m and 20 mu m for diesel and peanut oil, respectively. Line intensities from the liquid (C I) and the support (Al I) material were tracked as a function of the film thickness and the laser energy. By film thinning, the line intensities from liquid sample were enhanced up to a factor 100x; simultaneously, the LIBS signal fluctuations were reduced 5-10 times with respect to the steady droplet. In certain experimental conditions, the line intensities from the support material become very weak with respect to the C I line, indicating an efficient screening of the substrate by highly excited plasma from the liquid layer. At a fixed rotation speed, there is a laser energy threshold, dependent on the liquid thickness, above which the LIBS signal becomes stable. Here, we discuss the relative processes and optimization of the experimental conditions for the LIBS measurements frome one laser shot to another.

INDUCED BREAKDOWN SPECTROSCOPY; POLARIZATION SPECTROSCOPY

The polarisation anisotropy of the emission from a laser produced aluminium plasma has been studied using time and polarisation resolved spectroscopy at various background pressures of air. A Wollaston prism was used to resolve the emission from the plasma into polarisation components that are parallel and orthogonal to the plasma expansion axis. Spectroscopy reveals that as the background pressure is increased, strongly polarised continuum emission dominates at early stages of the plasma formation. The results are compared and contrasted to similar experiments and discussed in the framework of a recombining plasma. Published by AIP Publishing.

Aluminum; Tungsten; Collisional-radiative model; Laser-induced plasma; Non-equilibrium plasma; Ultrashort pulse;INDUCED BREAKDOWN SPECTROSCOPY; THERMODYNAMIC-EQUILIBRIUM; FACING COMPONENTS; FEMTOSECOND; ARGON; NANOSECOND; PICOSECOND; NITROGEN; LIBS; EXPANSION

The question of the Local Thermodynamic Equilibrium (LTE) of laser-induced plasmas is crucial regarding the Laser-Induced Breakdown Spectroscopy (LIBS) technique. The most relevant way to assess theoretically the possible departure from LTE is to develop state-to-state models of the chemical species involved. The present paper illustrates such an elaboration in the case of aluminum and tungsten. Based on this state-to-state approach, the two collisional-radiative models CoRaM-Al and CoRaM-W are elaborated. They include elementary processes under electron and heavy particle impact in thermal non-equilibrium, spontaneous emission, radiative recombination and thermal Bremsstrahlung. These models are applied to the case of ultrashort laser-induced plasmas expanding in an argon gas at different pressure, for which a relevant collisional-radiative model is also elaborated to predict the propagation of the shock wave. The laser conditions are close to those used for a typical LIBS analysis under ultrashort regime. At high argon pressure (10(5) Pa), the relaxation of the plasma takes place according to a rather low departure from LTE, as revealed by the thorough examination of the Boltzmann plots derived from the state-to-state models. This relaxation occurs at temperature higher for aluminum than for tungsten, but close to 10,000 IC from 200 ns. Conversely, at low pressure (10 Pa), the extinction of the plasma is observed at similar to 500 ns, just after a phase corresponding to significant departure from equilibrium. These results support the idea of the choice of short gate delays close to the laser pulse for the LIBS characterization of tungsten matrices in tokamak-like conditions. (C) 2016 Elsevier B.V. All rights reserved.