Double-pulse Configuration Research Articles

Effect of single and double pulse laser-induced breakdown spectroscopy towards steel alloy in different gaseous media

In recent years, laser-induced breakdown spectroscopy (LIBS) technique showed its promising for material analysis, quality control, forensic science, and environmental safety monitoring. Besides, due to its rapid measurement capability and minimal sample-preparation requirements, it is a widely recognized elemental analysis approach used in a variety of study domains. The current work compares spatially resolved single (SP) and double pulse (DP), especially orthogonal DP, setups for LIBS to examine and enhance the limit of detection (LOD) in duplex stainless steels alloy. Using the Boltzmann plot method and the Stark broadening mechanism, the electron temperature and density of local arc plasma are highlighted due to single pulse and orthogonal pre-pulse double pulse configurations. With delay time, the circumstances of arc plasma's local thermodynamic equilibrium (LTE) of emission spectral lines are investigated. The experimental results show that there are significant increases in the spectral intensities of the Fe lines in double pulse LIBS under Ar-gas compared to those under He-gas. Internal standardization was used to create calibration curves for the spectral lines of Cr, Cu, and Mn in the alloy sample for the both studied media. It demonstrated that argon outperforms helium in determining the elemental composition of steel alloys. Furthermore, LOD for SP-LIBS and DP-LIBS in both media were calculated, which showed a higher detection LOD for DP-LIBS in the presence of Ar-gas compared to that in He-gas.

Comparison of single and double pulse laser-induced breakdown spectroscopy for the detection of biomolecules tagged with photon-upconversion nanoparticles

BackgroundLaser-induced breakdown spectroscopy (LIBS) is a well-recognized analytical technique used for elemental analysis. This method is gaining considerable attention also in biological applications thanks to its ability for spatial mapping and elemental imaging. The implementation of LIBS in the biomedical field is based on the detection of metals or other elements that either naturally occur in the samples or are present artificially. The artificial implementation of nanoparticle labels (Tag-LIBS) enables the use of LIBS as a readout technique for immunochemical assays. However, one of the biggest challenges for LIBS to meet immunoassay readout standards is its sensitivity. ResultsThis paper focuses on the improvement of LIBS sensitivity for the readout of nanoparticle-based immunoassays. First, the LIBS setup was optimized on photon-upconversion nanoparticle (UCNP) droplets deposited on the microtiter plate wells. Two collection optics systems were compared, with single pulse (SP) and collinear double pulse (DP) LIBS arrangements. By deploying the second laser pulse, the sensitivity was improved up to 30 times. The optimized SP and DP setups were then employed for the indirect detection of human serum albumin based on immunoassay with UCNP-based labels. Compared to our previous LIBS study, the detection limit was enhanced by two orders of magnitude, from 10 ng mL−1 to 0.29 ng mL−1. In addition, two other immunochemical methods were used for reference, based on the readout of upconversion luminescence of UCNPs and absorbance measurement with enzyme labels. Finally, the selectivity of the assay was tested and the practical potential of Tag-LIBS was demonstrated by the successful analysis of urine samples. Significance and noveltyIn this work, we improved the sensitivity of the Tag-LIBS method by combining new labels based on UCNPs with the improved collection optics and collinear DP configuration. In the instrumental setup optimization, the DP LIBS showed better sensitivity and signal-to-noise ratio than SP. The optimizations allowed the LIBS readout to surpass the sensitivity of enzyme immunoassay, approaching the qualities of upconversion luminescence readout, which is nowadays a state-of-the-art readout technique.

UV femtosecond single-pulse and collinear double-pulse laser-induced breakdown spectroscopy (LIBS) for depth-resolved characterization of nano-scaled films

In the current work, we demonstrate the UV femtosecond (248 nm, 450 fs) single-pulse and double-pulse laser-induced breakdown spectroscopy (LIBS) as an effective method for depth profiling of nanometer-thick multi-layered structures, including photovoltaic thin films. Femtosecond LIBS enabled selective detection of both organic and inorganic materials at different depths within nanometer-scale (10–250 nm) multi-layered samples having thicknesses comparable to the etching depth produced by a single laser shot ablation. To enhance the analytical capabilities of the method, we applied the collinear double-pulse LIBS technique, using a Michelson interferometer to split the laser pulse into two equal-energy pulses. Results obtained with Indium Tin Oxide (ITO) nanofilms (115 nm layer thickness) present a clear increase of the intensity emission by a factor of 3 to 10, depending on laser fluence, when the double-pulse approach is used. Single-pulse LIBS achieved an ablation rate of around 60 nm, while the double-pulse configuration achieved 40 nm/pulse, in a sequence of seven laser shots. Furthermore, via double-pulse LIBS spectra were recorded even at fluences as low as 150 mJ/cm2, compared to 250 mJ/cm2 required for capturing spectra, when the same total energy per pulse was maintained.

Impulse and Plasma Plume Generated By Ablating Aluminum Target with Nanosecond Laser in Double-Pulse Configuration

For laser ablation propulsion, the enhancement of the impulse is very challenging to realize without increasing the laser energy. In this paper, the enhancement of the impulse in vacuum is achieved by laser ablation in double-pulse mode. The impulse produced by irradiating the aluminum target for different energy combinations in double-pulse mode was measured with the torsion pendulum. The plasma plume was observed at the same time by fast photography to analyze the cause of the impulse characteristics. The effect of the energy combinations for double-pulse mode on the ablation impulse was investigated at typical interpulse delay time. When the delay time between the pulses is set to 80 ns, the maximum impulse is increased by approximately 11% compared to that of the single-pulse mode at the same total energy, wherein the energy of the first pulse is 125mJ in total energy of 200mJ. Therefore, the enhancement of the impulse can be achieved by choosing the suitable energy combination in the double-pulse configuration. However, when the time delay is 300ns, the difference in energy combinations has little influence on the impulse. The results reported here provide guidance for the application of laser ablation propulsion in space.

Double-pulse laser ablation in liquids: nanoparticle bimodality reduction by sub-nanosecond interpulse delay optimization

Applications of nanoparticles (NPs) in medicine, energy, catalysis, or additive manufacturing demand the development of NP production methods that are offering material and solvent versatility, high purity, morphology, and size control, together with industrial-scale production capabilities. Pulsed laser ablation in liquids (PLAL) is a technique that comes close to meeting these demands; however, NP size control remains a challenge. To reduce the characteristic bimodality in NPs synthesized by high-intensity PLAL, a double pulse configuration with inter-pulse delays between 300 ps and 1200 ps is proposed. In this temporal delay window, the plume and initial bubble are still flat so that shielding of the second laser pulse by the cavitation bubble is avoided; minimizing pulse shielding that could reduce NP productivity. At a pulse delay of 600 ps, a (9 ± 1) wt% reduction of the large NP fraction is demonstrated (at the expense of mass yield), showing the possibility of modifying the NP size distribution produced in PLAL by temporal pulse shaping.

Characterization of CdTe Thin Films Using Orthogonal Double-Pulse Laser-Induced Breakdown Spectroscopy

Orthogonal reheating double-pulse laser-induced breakdown spectroscopy (LIBS) was applied to the elemental analysis of CdTe thin film samples. Films were grown through nanosecond pulsed laser ablation over silicon and glass substrates. The analysis was performed by applying a 266 nm pulsed laser devised to minimize sample damage. Re-excitation was conducted using a nanosecond laser emitting at 1064 nm that induced air breakdown 1 mm above the target. Emission enhancement was investigated as a function of both time acquisition delay and inter-pulse delay. The plasma temperature and electron density calculations made showed that the double-pulse scheme produced higher temperature values and a longer plasma duration than single-pulse LIBS. The self-absorption coefficient of the lines was determined from the measured ablated matter, plasma volume and collected spectra. The results of the double-pulse LIBS configuration showed a significant increase in emission intensity, reducing the self-absorption effect. In addition, the relative concentration of the thin films was determined for both experimental schemes. The calculated elemental values for the double-pulse configuration coincide with those expected and are more accurate than those obtained using a single laser.

Analysis of crosstalk effects in phase-OTDR system using fiber Bragg grating array

In this paper, the parasitic components (i.e., multi-reflections, Rayleigh scattering, photodetector noise, and phase variations due to external perturbations) are analysed and based on this analysis, a new signal to noise ratio (SNR) definition is provided suitable for the FBG-assisted Phase-OTDR system. A detailed analysis of performance parameters in the presence of multi reflection crosstalk (including its first- and second-order components) and spectral shadowing crosstalk is presented. SNR was calculated for different reflectivity and spacing lengths showing that the maximum number of cascaded FBGs can be significantly increased by using lower FBG reflectivity. It was also observed that the spacing length distance does not have a significant impact on the maximum number of FBGs that can be interrogated. By comparing single-pulse and double-pulse configurations, the use of double pulse was shown to provide higher SNR values when the number of FBGs is around 100 FBGs. The multi-reflection crosstalk when combined with the spectral-shadowing effect was demonstrated to create secondary crosstalk components making the interpretation of spectral analysis more difficult.

Laser ablation molecular isotopic spectroscopy: A novel tool to characterise the distribution of 13C and 12C on graphite after 13CH4 tracer injection in Wendelstein 7-X

Wendelstein 7-X (W7-X) operation with inertially cooled graphite Test Divertor Unit (TDU) was finalised in a series of identical hydrogen plasmas with injection of 13C isotopically marked methane. The break-up of 13CH4, injected through gas inlets at one toroidal position of W7-X, and the subsequent transport and deposition of 13C in the device was studied ex-situ. The TDU was therefore extracted from the vessel and some of the removed TDU elements were examined regarding their 13C distribution in deposited layers on the surface using Laser Ablation Molecular Isotopic Spectroscopy (LAMIS). This study shows the 13C/12C distinction capabilities of LAMIS used to analyse the carbon deposition pattern on Plasma-Facing Components (PFCs) on two of the removed TDU elements. The resulted pattern was compared with complementary results from Nuclear Reaction Analysis (NRA) and simulations of 13C deposition by ERO2.0, a material transport and plasma-surface interaction code. Ultra- short laser pulses of a Nd:YAG laser were used in collinear double-pulse configuration for LAMIS. The first pulse (l1 = 355 nm, t1 = 35 ps, F = 2.3 J/cm 2 ) produced a laser- induced plasma on the surface and 50 ns later, the second laser pulse (l2 = 1064 nm, t2 = 35 ps) was directed into this plasma to enhance the signal. Each pulse pair ablates in total 200 nm of the surface material. The analysis is conducted in 1.5 mbar N2 environment for improved signal-to-noise ratio relative to vacuum conditions. A high throughput custom-made spectrometer in Littrow-arrangement (f = 750 mm, A = 6000 at l = 473 nm, lspan = 14 nm) was used to analyse the C2 Swan bands (d3 ⊓ g - a3 ⊓ u, v = 1 to v’ = 0) of laser-induced plasma emission. • Laser Ablation Molecular Isotopic Spectroscopy is a method for isotopical analysis of materials. • Similar to Laser-Induced Breakdown Spectroscopy with analysis of molecular spectra. • This method has in-situ potential for material deposition studies in fusion devices. • This study shows good agreement with results from Nuclear Reaction Analysis. • General agreement with ERO2.0 simulations were found far from the injection location.

Quantitative analysis of chlorine in cement pastes based on collinear dual-pulse laser-induced breakdown spectroscopy

On-line detection of chlorine in cement is the key to evaluate the corrosion of the reinforced concrete inside the structure. A collinear dual-pulse LIBS system based on two nanosecond lasers with a total energy of 30 mJ is developed to detect the chlorine in cement. The key parameters of the dual-pulse LIBS system are optimized to improve the detection sensitivity of trace chlorine element in cement pastes, and the optimal values of the parameters are obtained to be: 4 L/min helium gas flow rate, 2000 ns inter-pulse delay, 800 ns gate delay, 19 mJ/11 mJ pulse energy ratio, and 42.8 mm lens-to-sample distance. After the optimization of the dual-pulse system, the signal-to-noise ratio of the trace chlorine emission line at 837.6 nm has been improved from 1.75 to 2.68 for a sample containing 0.706 wt% chlorine. The temperatures of plasma are obtained based on Saha-Boltzmann plot for exploring the plasma radiation features in the dual-pulse system. The results show that the plasma temperature which is influenced by laser irradiance and parameters of the double pulse configuration, is closely related to the signal-to-noise ratio of chlorine spectrum line. Sixteen standard cement pastes made from a series of sodium chloride solutions with various concentration are used for LIBS calibration. Two calibration methods including internal standardization and partial least squares regression are adopted for determining chlorine concentrations within a series of standard cement pastes, and the limit of detection based on internal standardization model is calculated to be 103.4 ppm. The prediction performance of IS and PLSR is evaluated by Leave-One-Out Cross-Validation with the root mean square error of calibration of 0.0910 and 0.0859, respectively.

Double pulse laser-induced plasmas on W and Al by ps-LIBS: Focus on the plasma-second pulse interaction

The LIBS (laser-induced breakdown spectroscopy) method can be implemented to determine the multi-elemental composition of solid samples. Unfortunately, the precision of the usual LIBS configuration (single pulse) is rather low for light elements in metallic matrices. The double pulse configuration can help to overcome this difficulty. Indeed, the electron temperature and density are significantly increased by the second pulse absorbed by the plasma produced by the first pulse which leads to a higher signal-to-noise ratio. The present paper reports preliminary results in double pulse configuration on fusion-relevant materials, i.e. aluminum (considered as a beryllium surrogate) and tunsgten, in the perspective of the test of this technique to measure in situ the hydrogen isotopes concentration of the divertor and the first wall of an ITER-like tokamak.The plasma spectroscopic analysis is performed to derive the gain in electron density reached by the absorption of the second pulse. In parallel, the spectral absorptivity of the plasma regarding the second pulse is determined to correlate the electron density dynamics to the energy deposit. The absorption by the plasma of the second pulse is then quantified at the atomic and macroscopic scales.

Absorption of a nanosecond laser pulse by a picosecond laser-induced preformed aluminum plasma

The LIBS (Laser-Induced Breakdown Spectroscopy) method has already demonstrated its reliability and its robustness in many situations for the multi-elemental composition determination of samples. However, certain conditions prevent a totally satisfactory determination. For instance, the method is weakly efficient to measure with accuracy the light elements concentration in metallic matrices. Since the laser pulse used to produce the plasma contributes to its heating, using an additional pulse (double pulse configuration) provides the increase in electron temperature and density without additional ablation. A better signal-to-noise ratio and a lower limit of detection can be reached. The present paper reports the results of different experiments performed to quantify the modifications induced (1) on the electron density by the second laser pulse in a preformed aluminum plasma, and (2) on the second laser pulse itself. The related experiments have been done in the case where the plasma is produced by a picosecond laser pulse and the second laser pulse is of the nanosecond type. The electron density reaches a maximum resulting from the total ionization of the aluminum plasma volume irradiated by the second laser pulse.

Role of carbon clusters in high-order harmonic generation in graphite plasmas

Laser ablation is able to produce plasmas containing neutrals, ions, clusters, and nanoparticles, which can all act as emitters of harmonics from ultrashort laser pulses. Here the efficient low- and high-order harmonic generation (HHG) of femtosecond pulses from the carbon plasmas produced by nanosecond pulses is demonstrated. The efficiencies of harmonic generation from carbon clusters are analyzed using delayed ablation of graphite. We show that carbon clusters can be considered as the sources of efficient harmonics in the 40-100 nm spectral range. This approach of harmonic generation from the plasmas in double-pulse configuration of HHG can be applied for studying other clusters to determine the best conditions for HHG and the influence of multi-particle species on the nonlinear optical processes.

Enhancement of optical emission generated from femtosecond double-pulse laser-induced glass plasma at different sample temperatures in air

In double-pulse laser-induced breakdown spectroscopy (DP-LIBS), the collinear femtosecond double-pulse laser configuration is experimentally investigated with different initial sample temperatures using a Ti:sapphire laser. The glass sample is ablated to produce the plasma spectroscopy. During the experiment, the detected spectral lines include two Na (I) lines (589.0 nm and 589.6 nm) and one Ca (I) line at the wavelength of 585.7 nm. The emission lines are measured at room temperature (22 °C) and three higher initial sample temperatures (Ts = 100 °C, 200 °C, and 250 °C). The inter-pulse delay time ranges from −250 ps to 250 ps. The inter-pulse delay time and the sample temperature strongly influence the spectral intensity, and the spectral intensity can be significantly enhanced by increasing the sample temperature and selecting the optimized inter-pulse time. For the same inter-pulse time of 0 ps (single-pulse LIBS), the enhancement ratio is approximately 2.5 at Ts = 200 °C compared with that obtained at Ts = 22 °C. For the same inter-pulse time of 150 ps, the enhancement ratio can be up to 4 at Ts = 200 °C compared with that obtained at Ts = 22 °C. The combined enhancement effects of the different initial sample temperatures and the double-pulse configuration in femtosecond LIBS are much stronger than that of the different initial sample temperatures or the double-pulse configuration only.

Shielding and diagnostics of laser-induced air plasmas generated in collinear double pulse configuration

Plasma shielding in collinear double-pulse laser-induced breakdown spectroscopy was characterized in terms of its time-resolved absorptivity, photographic images, and emission spectra. In experiments performed with the double pulse beam configuration, one to generate plasma and another a probe beam, the transmission of the probe beam was measured at various inter-pulse delay times up to 1500 ns as the plasma opacity evolves rapidly with time. Photographic images obtained at the same time delay indicate that the plasma absorptivity becomes weaker as plasma evolves. At times up to 500 ns after plasma initiation, plasma absorptivity rose above 70% but later decreased markedly. When viewing the transmission and photographic images, the beam-plasma interaction realized with the double-pulse configuration is explainable as laser-supported absorption waves. To clarify the phenomenon and plasma properties when the probe beam and plasma are coupled, Stark broadening was used to obtain the electron number density, which is of the order of 1018 cm−3. Also, emission spectra under single- and double-pulse experimental configuration were obtained and analyzed using the Boltzmann-plot method to provide the plasma temperatures. The intensities from the double-pulse experiments were slightly stronger, in agreement with the laser energy absorption data. Moreover, from emission signal enhancements obtained from the double-pulse experiments, the increase in the intensity of the ionic emission was more than that obtained from the atomic emission for which a larger fraction of the probe beam energy was absorbed.

Analytical Technique for Designing an RC Snubber Circuit for Ringing Suppression in a Phase-Leg Configuration

Herein, we propose an analytical technique for use in designing a resistor capacitor ( RC ) snubber circuit for suppressing ringing in phase-leg configurations that are among the main components in electric power converters. In our study, a double pulse circuit is used to examine the effects of RC snubber circuit ringing suppression because the phase-leg and double pulse configuration ringing mechanisms are the same. First, a high-frequency equivalent circuit of the double pulse circuit is derived. Next, an RC snubber circuit for ringing suppression is analytically designed by scrutinizing the characteristic equations via the root locus method. Prior to using the root locus method, we conducted an investigation to determine if that method could be used to analyze the derived high-frequency equivalent circuit when RC snubber circuit parasitic inductances and inductances between the upper and lower modules connectors are small enough to ignore. Finally, the ringing suppression effect of the RC snubber designed by using the proposed analytical technique in a double pulse circuit with practical parasitic inductance values is confirmed via circuit simulations and experimental demonstrations.

Measurement of chlorine concentration on steel surfaces via fiber-optic laser-induced breakdown spectroscopy in double-pulse configuration

The corrosive environment provided by chlorine ions on the welds of stainless steel dry cask storage canisters for used nuclear fuel may contribute to the occurrence of stress corrosion cracking. We demonstrate the use of fiber-optic laser-induced breakdown spectroscopy (FOLIBS) in the double-pulse (DP) configuration for high-sensitivity, remote measurement of the surface concentrations of chlorine compatible in constrained space and challenging environment characteristic for dry cask storage systems. Chlorine surface concentrations as low as 5mg/m2 have been detected and quantified by use of a laboratory-based and a fieldable DP FOLIBS setup with the calibration curve approach. The compact final optics assembly in the fieldable setup is interfaced via two 25-m long optical fibers for high-power laser pulse delivery and plasma emission collection and can be readily integrated into a multi-sensor robotic delivery system for in-situ inspection of dry cask storage systems.

Determination of the limits of detection for aluminum-based alloys by spatially resolved single- and double-pulse laser-induced breakdown spectroscopy

A comparative study of LIBS with spatially resolved single- and double-pulse configurations is performed to investigate the capability of simultaneous multi-element detection in aluminum-based alloys.

Mapping of the spatial distribution of silver nanoparticles in root tissues of Vicia faba by laser-induced breakdown spectroscopy (LIBS)

The manuscript presents a procedure for optimal sample preparation and the mapping of the spatial distribution of metal ions and nanoparticles in plant roots using laser-induced breakdown spectroscopy (LIBS) in a double-pulse configuration (DP LIBS) in orthogonal reheating mode. Two Nd:YAG lasers were used; the first one was an ablation laser (UP-266 MACRO, New Wave, USA) with a wavelength of 266nm, and the second one (Brilliant, Quantel, France), with a fundamental wavelength of 1064nm, was used to reheat the microplasma. Seedlings of Vicia faba were cultivated for 7 days in CuSO4 or AgNO3 solutions with a concentration of 10µmoll−1 or in a solution of silver nanoparticles (AgNPs) with a concentration of 10µmoll−1 of total Ag, and in distilled water as a control. The total contents of the examined metals in the roots after sample mineralization as well as changes in the concentrations of the metals in the cultivation solutions were monitored by ICP-OES. Root samples embedded in the TissueTek medium and cut into 40µm thick cross sections using the Cryo-Cut Microtome proved to be best suited for an accurate LIBS analysis with a 50µm spatial resolution. 2D raster maps of elemental distribution were created for the emission lines of Cu(I) at 324.754nm and Ag(I) at 328.068nm. The limits of detection of DP LIBS for the root cross sections were estimated to be 4pg for Cu, 18pg for Ag, and 3pg for AgNPs. The results of Ag spatial distribution mapping indicated that unlike Ag+ ions, AgNPs do not penetrate into the inner tissues of Vicia faba roots but stay in their outermost layers. The content of Ag in roots cultivated in the AgNP solution was one order of magnitude lower compared to roots cultivated in the metal ion solutions. The significantly smaller concentration of Ag in root tissues cultivated in the AgNP solution also supports the conclusion that the absorption and uptake of AgNPs by roots of Vicia faba is very slow. LIBS mapping of root sections represents a fast analytical method with sufficient precision and spatial resolution that can provide very important information for researchers, particularly in the fields of plant science and ecotoxicology.

Semiquantitative analysis of mercury in landfill leachates using double-pulse laser-induced breakdown spectroscopy.

Laser-induced breakdown spectroscopy (LIBS) is showing to be a promising, quick, accurate, and practical technique to detect and measure metal contaminants and nutrients in urban wastes and landfill leachates. Although conventional LIBS presents some limitations, such as low sensitivity, when used in the single pulse configuration if compared to other spectroscopic techniques, the use of the double-pulse (DP) configuration represents an adequate alternative. In this work DP LIBS has been applied to the qualitative and quantitative analysis of mercury (Hg) in landfill leachates. The correlation analysis performed between each intensified charge-coupled device pixel and the Hg concentration allowed us to choose the most appropriate Hg emission line to be used for its measure. The normalization process applied to LIBS spectra to correct physical matrix effects and small fluctuations increased from 0.82 to 0.98 the linear correlation of the calibration curve between LIBS and the reference data. The limit of detection for Hg estimated using DP LIBS was 76 mg Kg-1. The cross validation (leave-one-out) analysis yielded an absolute average error of about 21%. These values showed that the calibration models were close to the optimization limit and satisfactory for Hg quantification in landfill leachate.

Single and double long pulse laser ablation of aluminum induced in air and water ambient

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 21mm) 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.