Laser Plasma Plume Research Articles

Self-absorption correction method based on intensity self-calibration of doublet lines.

The self-absorption effect in an optically thick plasma seriously affects the spectral line intensity and the measurement accuracy of laser-induced breakdown spectroscopy (LIBS). In this work, a self-absorption correction method based on intensity self-calibration of doublet lines belonging to the same multiplet is proposed. The K/Δλ0 parameter and self-absorption coefficient (SA) of the doublet lines of the analytical element can be calculated based on the measured actual lines intensity ratio and the K parameters ratio. Compared with the generally applied self-absorption correction methods, this method can effectively reduce the influence of laser energy and plasma plume fluctuations and the non-uniformity distribution of the element in the plasma, and is independent of the availability of Stark broadening coefficients. So it has obvious advantages of high computation efficiency, high analysis accuracy and good applicability. Univariate quantitative analysis results of aluminum (Al) show that the correlation coefficient of calibration curves and the measurement accuracy of elemental content have been significantly improved with the self-absorption correction.

Green Production of Planar Aligned Dense 2D Nano-oxides on CNT Paper by Ultrafast Laser-Induced High-Pressure Photochemistry for Stable High-Rate LIB Anodes

Green production of functional nano-oxides on a large scale is crucial for the modern manufacturing industries. Traditional hydrothermal methods and ball milling are usually time-consuming and require long-term energy input with undesired by-products. Herein, an ultrafast laser-induced high-pressure photochemistry manufacturing technique is developed to massively produce planar-aligned graphene-coated two-dimensional (2D) SnO 2 nanoplatelet on carbon nanotube (CNT) paper under the green chemistry guidelines. The unique design of Z-axis confinement added to the ultrafast laser irradiation provides an exceptional high temperature of 1772 K and a high pressure of 24 GPa in the localized laser plasma plume. This transient nonequilibrium condition controls the formation of 2D SnO 2, and the ablated C atoms cool down afterward as in-situ “glue” to intactly seal the oxides on the CNT substrate. The resultant hierarchical Graphene@2D SnO 2 @CNT paper anode for Li-ion battery has an outstanding capacity of 819 mAh g −1 (1637 mAh cm −3 ) at 0.5 A g −1 and retains 622 mAh g −1 (1245 mAh cm −3 ) at 5.0 A g −1 . The high capacity at 0.5 A g −1 has a retention of 92% after 600 cycles. This work provides an environmental-friendly scalable manufacturing technique to produce functional nanocomposites in 1 step.

Shock interactions between plasma jets from conical wire array Z-pinches and laser-produced plasma plume

The interaction of a supersonic plasma jet outflow with a background laser-produced plasma plume is experimentally studied. The aim of these studies is to provide an experimental platform to study jet-ambient interactions in an environment relevant to high energy density physics scenarios. The jet outflow is produced by a conical wire array Z-pinch composed of 16 aluminum wires (40 μm diameter each) acting as load of the Llampudken generator (∼400kA, ∼350 ns). The laser plasma plume is produced by focusing a 2 × 1010 W/cm2 laser pulse onto an aluminum target. Our experimental results show that in the absence of laser plasma plume, there is no significant photoionized plasma from the target that interacts with the jet outflow. On the contrary, when combining both plasma sources, a new structure appears at the interaction region. The thickness of this structure is of the order of the inter-particle ion-ion mean free path, which was calculated for a wide range of parameters for each plasma. These results indicate the presence of a collisional shock layer created after the interaction. Further details and potential applications are shown and discussed.

Magnetically Aligned Ultrafine Cobalt Embedded 3D Porous Carbon Metamaterial by One-Step Ultrafast Laser Direct Writing.

Spatial manipulation of nanoparticles (NPs) in a controlled manner is critical for the fabrication of 3D hybrid materials with unique functions. However, traditional fabrication methods such as electron‐beam lithography and stereolithography are usually costly and time‐consuming, precluding their production on a large scale. Herein, for the first time the ultrafast laser direct writing is combined with external magnetic field (MF) to massively produce graphene‐coated ultrafine cobalt nanoparticles supported on 3D porous carbon using metal–organic framework crystals as precursors (5 × 5 cm2 with 10 s). The MF‐confined picosecond laser scribing not only reduces the metal ions rapidly but also aligns the NPs in ultrafine and evenly distributed order (from 7.82 ± 2.37 to 3.80 ± 0.84 nm). ≈400% increment of N‐Q species within N compositionis also found as the result of the special MF‐induced laser plasma plume. (). The importance of MF is further exmined by electrochemical water‐splitting tests. Significant overpotential improvements of 90 and 150 mV for oxygen evolution reaction and hydrogen evolution reaction are observed, respectively, owing to the MF‐induced alignment of the NPs and controlled elemental compositions. This work provides a general bottom‐up approach for the synthesis of metamaterials with high outputs yet a simple setup.

Laser plasma plume parameters for cascade fission of metal micro- and nanodroplets

The cascade fission under the action of Coulomb forces of metal droplets charged up to the Rayleigh limit in a vacuum has been well studied and it is widely used in vacuum technology. Experimental works using the laser electrodispersion method showed that such a division can be carried out in the plasma of a laser plasma plume during the process of nanosecond ablation of metals. The previously published analytical model made it possible to work out requirements for plasma parameters, at which droplets can be divided to nanometer scales, but the limits of applicability of this model were not known. In this paper we present a more accurate numerical model for charging metal droplets in a laser plasma plume, which was used to obtain laser plasma parameters for implementation of cascade metal droplet fission. A comparison with the results obtained using the analytical model is presented.

Novel use of a hand-held laser induced breakdown spectroscopy instrument to monitor hydride corrosion in uranium

Using a compact hand-held laser-induced breakdown spectroscopy (LIBS) instrument, studies were conducted on specimens of uranium charged with controlled hydrogen concentrations for a qualitative evaluation of hydride corrosion. Four samples of depleted uranium with two different starting microstructures (cast and rolled) were used for this study. The hydrogen charged samples (rolled 1.8 wppm H and cast 14 wppm H by weight) are representative of the pre-corrosion states with hydrides distributed throughout the bulk. In-depth LIBS measurements were carried out, after the thick surface corrosion layer was removed, by applying 100 laser pulses from sample surface into the bulk on five different sample locations. Three additional areas on each sample were studied by laser ablation using a 12-point grid approach. The atomic emission signals of elemental uranium, carbon, hydrogen, and oxygen were identified and analyzed. All four samples showed similar uranium and carbon concentrations, as expected. Hydrogen content was consistent with each sample's specification, such that the hydrogen charged samples exhibited higher hydrogen concentration than their references. Both specimens charged with hydrogen showed elevated oxygen content as well, due to rapid oxidation of uranium and uranium hydrides. The oxidation process was facilitated by the laser ablation and plasma plume's high temperature effects on the sample combined with the glovebox environment. The uranium surface damage produced by laser ablation was quantitatively evaluated by optical microscopy.

A direct comparison of high-speed methods for the numerical Abel transform.

The Abel transform is a mathematical operation that transforms a cylindrically symmetric three-dimensional (3D) object into its two-dimensional (2D) projection. The inverse Abel transform reconstructs the 3D object from the 2D projection. Abel transforms have wide application across numerous fields of science, especially chemical physics, astronomy, and the study of laser-plasma plumes. Consequently, many numerical methods for the Abel transform have been developed, which makes it challenging to select the ideal method for a specific application. In this work, eight published transform methods have been incorporated into a single, open-source Python software package (PyAbel) to provide a direct comparison of the capabilities, advantages, and relative computational efficiency of each transform method. Most of the tested methods provide similar, high-quality results. However, the computational efficiency varies across several orders of magnitude. By optimizing the algorithms, we find that some transform methods are sufficiently fast to transform 1-megapixel images at more than 100 frames per second on a desktop personal computer. In addition, we demonstrate the transform of gigapixel images.

Size-controlled growth of nanoparticles and clusters during pulsed laser ablation into an ambient wave induced plasma

The interaction of a laser plasma plume with aluminum (Al) targets in an ambient microwave induced plasma is investigated. The expanding metallic laser plasma plume interacts with the gaseous wave induced plasma resulting in the formation of nanoparticles and clusters. The ambient plasma is obtained in molecular and atomic gases of different atomic weights such as hydrogen (H2), argon (Ar) and krypton (Kr), keeping the gas pressure in the range 0.04–0.15 Pa. The plasma is well confined and uniformly distributed within a radius of ∼3 cm in a twelve-pole magnetic multicusp (MC, surface magnetic field ∼0.4 T). The electron temperature (Te) and density (ne) of the ambient plasma are ∼7–10 eV and ∼1010 cm−3 respectively at 200 W of microwave power. The growth and size distribution of the nanoparticles (NPs) formed are investigated. The mean size of the NPs is found to depend directly on Te and gas species of ambient microwave induced plasma. The largest NP size (∼55 nm) is obtained in H2 plasma while the minimum size (∼5 nm) is achieved in Kr plasma. As the atomic weight of the ambient gas increases, the plasma ion thermal velocity decreases and so does the size of the NPs.

Dynamics of laser produced annular plasmas

We present preliminary experimental observations of the plasma dynamics of laser produced annular plasmas, expanding freely in a 80 mTorr Argon background. A Nd:YAG laser, 340 mJ, 3.5 ns, at 1.06 µm, operating at 10 Hz, is used in the experiments. To produce the annular plasma the laser pulse is focused on a titanium target using a combination of axicon and convergent lens. The dynamics of the laser plasma is characterized by 50 ns time resolved plasma imaging of the visible plasma emission. The inwards radial expansion of the initial plasma ring result in on-axis stagnation, giving rise to an expanding axial laser plasma plume. A quantitative description of the laser plasma dynamics is presented.

Formation of Amorphous Carbon Nanoparticles by the Laser Electrodispersion Method

Experimental results on the laser ablation of the highly oriented pyrolytic graphite by using light pulses of an Nd:YAG laser (pulse width 25 ns, pulse energy 220 mJ) are presented. Analysis of the surface profile of the carbon target shows that the target material melts in the course of the laser ablation. As a result of ablation, a coating consisting of carbon nanoparticles about 10 nm in size is formed on the substrate placed at a distance of 4 cm from the target. It is assumed that such particles are formed as a result of the electrodispersion of carbon droplets detached from the target surface and charged to an unstable state in the laser plasma plume. Raman spectra of the coatings indicate that the carbon nanoparticles being formed have an amorphous structure.

Deposition of nanocomposite Cu–TiO2 using heterogeneous colliding plasmas

The formation of CuTiO2 nanocomposites has been observed in an experiment in which laser plasma plumes of Cu and Ti collide and stagnate in an oxygen atmosphere. The inherent advantage of this technique lies in its simplicity and flexibility where laser, target composition and geometry along with ambient atmosphere are all controllable parameters through which the stoichiometry of the deposited nanocomposites may be selected. The experiment has been performed at three oxygen ambient pressures 10−4, 10−2, 100 mbar and we observe its effect on stoichiometry, and morphology of the deposited nanocomposites. Here, we show how the stoichiometry of deposited nanocomposites can be readily controlled by changing just one parameter, namely the ambient oxygen pressure. The different peaks of photoluminescence spectra \(\lambda =390{\text{ nm}}\;\left( {E=3.18{\text{ eV}}} \right)\) corresponding to the anatase phase of TiO2, along with the peaks at λ = 483 nm (E = 2.56 eV) and 582 nm (E = 2.13 eV) of deposited nanocomposites, shows the doping/blending effect on the band gaps which may potentially be of value in solar cell technology. The technique can, in principle, be extended to include nanocomposites of other materials making it potentially more widely applicable.

Laser machining micro-structures on diamond surface with a sub-nanosecond pulsed laser

Micro-structure surface on diamond material is widely used in a series of industrial and scientific applications, such as micro-electromechanical systems (MEMS), nanoelectromechanical systems (NEMS), microelectronics, textured or micro-structured diamond machining tools. The efficient machining of micro-structure on diamond surface is urgently demanded in engineering. In this paper, laser machining square micro-structure on diamond surface was studied with a sub-nanosecond pulsed laser. The influences of laser machining parameters, including the laser power, scanning speed, defocusing quantity and scanning pitch, were researched in view of the ablation depth, material removal rate and machined surface topography. Both the ablation depth and material removal rate increased with average laser power. A reduction of the growth rate of the two parameters was induced by the absorption of the laser plasma plume at high laser power. The ablation depth non-linearly decreased with the increasing of the scanning speed while the material removal rate showed an opposite tendency. The increasing of the defocusing quantity induced complex variation of the ablation depth and the material removal rate. The maximum ablation depth and material removal rate were achieved at a defocusing position. The ablation depth and material removal rate oppositely varied about the scanning pitch. A high overlap ratio was meaningful for achieving a smooth micro-structure surface topography. Laser machining with a large defocusing quantity, high laser power and small scanning pitch was helpful for acquiring the desired micro-structure which had a large depth and smooth micro-structure surface topography.

Формирование аморфных наночастиц углерода методом лазерного электродиспергирования

AbstractExperimental results on the laser ablation of the highly oriented pyrolytic graphite by using light pulses of an Nd:YAG laser (pulse width 25 ns, pulse energy 220 mJ) are presented. Analysis of the surface profile of the carbon target shows that the target material melts in the course of the laser ablation. As a result of ablation, a coating consisting of carbon nanoparticles about 10 nm in size is formed on the substrate placed at a distance of 4 cm from the target. It is assumed that such particles are formed as a result of the electrodispersion of carbon droplets detached from the target surface and charged to an unstable state in the laser plasma plume. Raman spectra of the coatings indicate that the carbon nanoparticles being formed have an amorphous structure.

Effect of ambient pressure on interaction between laser radiation and plasma plume in fiber laser welding

Fiber laser welding of aluminum alloy under vacuum was performed in this study. To understand the increases in weld penetration depth and changes in weld cross section profile in laser welding under vacuum or subatmospheric pressure, the effect of ambient pressure on interaction between laser radiation and plasma plume was studied. The electron temperature, electron density and inverse bremsstrahlung absorption of laser energy were calculated by spectroscopic analyses. The attenuation and refraction of laser energy from plasma plume were studied by probe laser beam measurements. It was found that the inverse bremsstrahlung absorption, attenuation and refraction of laser energy were sensitive to ambient pressure and decreased with the decrease of ambient pressure. Based on the effect of ambient pressure on boiling temperature of materials and interaction between laser radiation and plasma plume, the laser energy absorption mechanisms between atmosphere and vacuum was compared. The finding suggested that the decreasing of plasma plume disturbance, the increasing of the laser energy in keyhole and the decreasing of boiling temperature changed the absorption mechanism of laser energy, resulting in a large aspect ratio with narrow and parallel sides of weld cross section profile under vacuum.

Laser-Induced Plasma on a Titanium Target, a Non-equilibrium Model

We use a comprehensive model to investigate the interaction of ultraviolet nanosecond laser pulses with a titanium material. We calculate plasma ignition thresholds and study the effect of the laser-plasma interaction and the importance of the electronic non-equilibrium in the laser-induced plume and its expansion in the background gas. Our calculations of plasma ignition thresholds on titanium targets are validated and compared with experimental and theoretical results. A comparison with experimental data indicates that our results agree well with those reported in the literature. Results for titanium and copper are also compared under the same conditions. The inclusion of electronic non-equilibrium in our work indicates that this important process must be included in laser ablation and plasma plume formation models.

Observation of collisionless shocks in a large current‐free laboratory plasma

AbstractWe report the first measurements of the formation and structure of a magnetized collisionless shock by a laser‐driven magnetic piston in a current‐free laboratory plasma. This new class of experiments combines a high‐energy laser system and a large magnetized plasma to transfer energy from a laser plasma plume to the ambient ions through collisionless coupling, until a self‐sustained MA∼ 2 magnetosonic shock separates from the piston. The ambient plasma is highly magnetized, current free, and large enough (17 m × 0.6 m) to support Alfvén waves. Magnetic field measurements of the structure and evolution of the shock are consistent with two‐dimensional hybrid simulations, which show Larmor coupling between the debris and ambient ions and the presence of reflected ions, which provide the dissipation. The measured shock formation time confirms predictions from computational work.

Iron Distribution in Size‐Resolved Aerosols Generated by UV‐Femtosecond Laser Ablation: Influence of Cell Geometry and Implications for In Situ Isotopic Determination by LA‐MC‐ICP‐MS

The influence of ablation cell geometry (Frames single‐ and HelEx two‐volume cells) and laser wavelength (198 and 266 nm) on aerosols produced by femtosecond laser ablation (fs‐LA) were evaluated. Morphologies, iron mass distribution (IMD) and 56Fe/54Fe ratios of particles generated from magnetite, pyrite, haematite and siderite were studied. The following two morphologies were identified: spherules (10–200 nm) and agglomerates (5–10 nm). Similarity in IMD and ablation rate at 198 and 266 nm indicates similar ablation mechanisms. 56Fe/54Fe ratios increased with aerodynamic particle size as a result of kinetic fractionation during laser plasma plume expansion, cooling and aerosol condensation. The HelEx cell produces smaller particles with a larger range of 56Fe/54Fe ratios (1.85‰) than particles from the Frames cell (1.16‰), but the bulk aerosol matches the bulk substrate for both cells, demonstrating stoichiometric fs‐LA sampling. IMD differences are the result of faster wash out of the HelEx cell allowing less time for agglomeration of small, low‐δ 56Fe particles with larger, high‐δ 56Fe particles in the cell. Even with a shorter ablation time, half the total Fe ion intensity, and half the ablation volume, the HelEx cell produced Fe isotope determinations for magnetite that were as precise as the Frames cell, even when the latter included an aerosol‐homogenising mixing chamber. The HelEx cell delivered a more constant stream of small particles to the ICP, producing a more stable Fe ion signal (0.7% vs. 1.5% RSE for 56Fe in a forty‐cycle single analysis), constant instrumental mass bias and thus a more precise measurement.

Laser induced plasma on copper target, a non-equilibrium model

The aim of this work is to present a comprehensive numerical model for the UV laser ablation of metal targets, it focuses mainly on the prediction of laser induced plasma thresholds, the effect of the laser-plasma interaction, and the importance of the electronic non-equilibrium in the laser induced plume and its expansion in the background gas. This paper describes a set of numerical models for laser-matter interaction between 193-248 and 355 nm lasers and a copper target. Along with the thermal effects inside the material resulting from the irradiation of the latter with the pulsed laser, the laser-evaporated matter interaction and the plasma formation are thoroughly modelled. In the laser induced plume, the electronic nonequilibrium and the laser beam absorption have been investigated. Our calculations of the plasmas ignition thresholds on copper targets have been validated and compared to experimental as well as theoretical results. Comparison with experiment data indicates that our results are in good agreement with those reported in the literature. Furthermore, the inclusion of electronic non-equilibrium in our work indicated that this important process must be included in models of laser ablation and plasma plume formation.

Atomic mass dependent electrostatic diagnostics of colliding laser plasma plumes

The behaviours of colliding laser plasma plumes (Cp) compared with single plasma plumes (Sp) are investigated for 14 different atomic mass targets. A Faraday cup, situated at the end of a drift tube (L = 0.99 m), is employed to record the time-of-flight (TOF) current traces for all elements and both plume configurations, for a fixed laser intensity of Ip = 4.2 × 1010 W cm−2 (F = 0.25 kJ cm−2). The ratio of the peak current from the Cp relative to twice that from the Sp is designated as the peak current ratio while the ratio of the integrated charge yield from the Cp relative to twice that from the Sp is designated as the charge yield ratio. Variation of the position of the Faraday cup within the drift tube (L = 0.33, 0.55, and 0.99 m) in conjunction with a lower laser fluence (F = 0.14 kJ cm−2) facilitated direct comparison of the changing TOF traces from both plasma configurations for the five lightest elements studied (C, Al, Si, Ti, and Mn). The results are discussed in the frame of laser plasma hydrodynamic modelling to approximate the critical recombination distance LCR. The dynamics of colliding laser plasma plumes and the atomic mass dependence trends observed are presented and discussed.

Application of laser-induced breakdown spectroscopy for characterization of material deposits and tritium retention in fusion devices

Laser-induced breakdown spectroscopy (LIBS) is discussed as a possible method to characterize the composition, tritium retention and amount of material deposits on the first wall of fusion devices. The principle of the technique is the ablation of the co-deposited layer by a laser pulse with P (power density)≥0.5GW/cm2 and the spectroscopic analysis of the light emitted by the laser induced plasma. The typical spatial extension of the laser plasma plume is in the order of 1cm with typical plasma parameters of ne≈3×1022m−3 and Te≈1–2eV averaged over the plasma lifetime which is below 1μs. In this study “ITER-Like” mixed deposits with a thickness of about 2μm and consisting of a mixture of W/Al/C and D on bulk tungsten substrates have been analyzed by LIBS to measure the composition and hydrogen isotopes content at different laser energies, ranging from about 2J/cm2 (0.3GW/cm2) to about 17J/cm2 (2.4GW/cm2) for 7ns laser pulses. It is found that the laser energies above about 7J/cm2 (1GW/cm2) are needed to achieve the full removal of the deposit layer and identify a clear interface between the deposit and the bulk tungsten substrate by applying 15–20 laser pulses while hydrogen isotopes decrease strongly after the first laser pulse. Under these conditions, the evolution of the spectral line intensities of W/Al/C/hydrogen can be used to evaluate the layer composition.