Megapixel multi-elemental imaging by Laser-Induced Breakdown Spectroscopy, a technology with considerable potential for paleoclimate studies

Paleoclimate studies play a crucial role in understanding past and future climates and their environmental impacts. Current methodologies for performing highly sensitive elemental analysis at micrometre spatial resolutions are restricted to the use of complex and/or not easily applied techniques, such as synchrotron radiation X-ray fluorescence micro-analysis (μ-SRXRF), nano secondary ion mass spectrometry (nano-SIMS) or laser ablation inductively coupled plasma mass spectrometry (LAICP-MS). Moreover, the analysis of large samples (>few cm²) with any of these methods remains very challenging due to their relatively low acquisition speed (~1–10 Hz), and because they must be operated in vacuum or controlled atmosphere. In this work, we proposed an imaging methodology based on laser-induced breakdown spectroscopy, to perform fast multi-elemental scanning of large geological samples with high performance in terms of sensitivity (ppm-level), lateral resolution (up to 10 μm) and operating speed (100 Hz). This method was successfully applied to obtain the first megapixel images of large geological samples and yielded new information, not accessible using other techniques. These results open a new perspective into the use of laser spectroscopy in a variety of geochemical applications

Quantification of surface contamination on optical glass via sensitivity-improved calibration-free laser-induced breakdown spectroscopy

We report quantitative analysis of manufacturing-induced trace contaminants of optical glass surfaces by laser-induced breakdown spectroscopy (LIBS). Therefore, spectra recorded with an echelle spectrometer coupled to a gated detector were analysed using a calibration-free LIBS approach based on the calculation of the spectral radiance of a plasma in local thermodynamic equilibrium. The measurements were carried out in experimental conditions that enable both accurate modelling of plasma emission and high sensitivity for trace element analysis. Depth-resolved measurements were performed by recording spectra for successive laser pulses applied to the same irradiation sites. Validated via inductively coupled plasma atomic emission spectroscopy for the bulk glass composition, the measurements evidence a surface contamination that originates from polishing during glass manufacturing. The measured penetration depths of the contaminants are discussed in the frame of the underlying mechanisms of surface contamination and related to the changes of the optical properties evidenced by ellipsometric measurements. Demonstrated here for optical glass, the sensitivity-improved calibration-free LIBS approach can be used to quantify contaminations of surfaces in all kind of technological applications

Investigation of signal extraction in the frame of laser induced breakdown spectroscopy imaging

International audienceLaser-induced breakdown spectroscopy (LIBS)-based imaging techniques have become well known among spatially resolved elemental approaches due to their mature instrumentation and outstanding advantages and applications. Data processing and in particular signal extraction are key in all LIBS-based imaging analyses to provide robust and reliable results. To date, there has not been a statistical evaluation of this issue when processing large and complex LIBS datasets. In this work, we aimed to test the performance of three extraction methods applied to micro-LIBS-based imaging. We also proposed a new conditional data extraction procedure relying on the statistical uncertainty associated with the extracted signal. We built a synthetic spectral dataset with controlled spectral features and tested the linearity, dynamic range and operating speed of different extraction approaches. The results of this study demonstrate the importance of data extraction and provide evidence for its optimization. This procedure is of particular relevance for the extraction of weak line intensities and in cases where the presence or absence of certain elements is critical (i.e., biomedical applications or trace analysis). In addition, the proposed conditional approach offers new insights into the means of providing LIBS imaging results

Multiscale viscoplastic modeling of recycled glass fiber-reinforced thermoplastic composites: Experimental and numerical investigations

One of the main challenges facing fiber-reinforced polymer composites is the lack of options for end-of-life recycling. The environmental impact of waste materials disposed of at landfill sites, by incineration, or by erratic dispersion in the environment is accelerating the need to find innovative solutions to increase the value of recycled materials. This research aims to investigate the relationship between microstructural parameters and the mechanical properties of a recycled thermoplastic composite material. The latter is processed by thermo­ compression molding of a polyamide (PA66) matrix reinforced with chopped glass strands. An innovative approach is proposed to link the local microstructure of the composite to the mechanical behavior of the recycled material. It exploits an experimental characterization of the material microstructure using optical microscopy and X-ray micro-computed tomography (mCT). The experimental findings are implemented into a numerical modeling strategy to mimic the flexural behavior, based on a micromechanical approach coupling mean and full-field analysis. The region of interest is reconstructed from detailed 3D images using a modified random sequential adsorption (MRSA) algorithm, while other regions are modeled as homogenized macro-scale continua. Furthermore, the abilities of the proposed approach are proven by incorporating the viscoplastic behavior of the random heterogeneous material induced by the polymer matrix. The originality of the present research consists of the multi-scale FE analysis and the experimental validation for the viscoplastic behavior of the recycled composite material, taking into account influences from the microstructure.This work was partially supported by the French Region Grand Est, and the European Community (#AL0029234). The author from the University of Nottingham also gratefully acknowledges the support from the Engineering and Physical Sciences Research Council, as part of the “EPSRC Future Composites Manufacturing Research Hub” (EP/P006701/1)

Evaluation of pressure in a plasma produced by laser ablation of steel

We investigated the time evolution of pressure in the plume generated by laser ablation with ultraviolet nanosecond laser pulses in a near-atmospheric argon atmosphere. These conditions were previously identified to produce a plasma of properties that facilitate accurate spectroscopic diagnostics. Using steel as sample material, the present investigations benefit from the large number of reliable spectroscopic data available for iron. Recording time-resolved emission spectra with an echelle spectrometer, we were able to perform accurate measurements of electron density and temperature over a time interval from 200 ns to 12 μs. Assuming local thermodynamic equilibrium, we computed the plasma composition within the ablated vapor material and the corresponding kinetic pressure. The time evolution of plume pressure is shown to reach a minimum value below the pressure of the background gas. This indicates that the process of vapor-gas interdiffusion has a negligible influence on the plume expansion dynamics in the considered timescale. Moreover, the results promote the plasma pressure as a control parameter in calibration-free laser-induced breakdown spectroscopy

Extensive preoperative workup in diffuse esophageal leiomyomatosis associated with Alport syndrome influences surgical treatment: A case report

Introduction: Diffuse esophageal leiomyomatosis is a rare disease. Misdiagnosis is frequent and previous surgeries can complicate surgical management. The only treatment described for severe symptomatic cases is esophagectomy. Presentation of case: We describe a case of diffuse esophageal leiomyomatosis associated with Alport syndrome in a 21 year-old female where endoscopic ultrasonography (EUS) with concomitant fluoroscopy and 3D-gastric computed tomography (3D-GCT) modified surgical management. Discussion: The diagnosis of diffuse esophageal leiomyomatosis is difficult but can be greatly facilitated by extensive endoscopic and radiologic workup. Esophagectomy should only be entertained after complete anatomic mapping of the lesions, especially after previous surgeries. Conclusion: EUS and 3D-GCT should strongly be considered as part of routine preoperative workup in these patients

Investigation on the material in the plasma phase by high temporally and spectrally resolved emission imaging during pulsed laser ablation in liquid (PLAL) for NPs production and consequent considerations on NPs formation

In this paper experimental temperature and density maps of the laser induced plasma in water during pulsed laser ablation in liquid (PLAL) for the production of metallic nanoparticles (NPs) has been determined. A detection system based on the simultaneous acquisition of two emission images at 515 and 410 nm has been constructed and the obtained images have been processed simultaneously by imaging software. The results of the data analysis show a variation of the temperature between 4000 and 7000 K over the plasma volume. Moreover, by the study of the temperature distribution and of the number densities along the plasma expansion axis it is possible to observe the condensation zone of the plasma where NPs can be formed. Finally, the time associated with the electron processes is estimated and the plasma charging effect on NPs is demonstrated. The set of observations retrieved from these experiments suggests the importance of the plasma phase for the growth of NPs and the necessity of considering the spatial distribution of plasma parameters for the understanding of one of the most important issues of the PLAL process, that is the source of solid material in the plasma phase

Imaging rare-earth elements in minerals by laser-induced plasma spectroscopy: Molecular emission and plasma-induced luminescence

International audienceLaser-induced breakdown spectroscopy (LIBS) of atoms and ions of rare earth elements (REEs) appears to be an effective tool for REE detection and identification, specifically in imaging applications. We propose to combine this technique with the molecular emissions of LaO and YO and the plasma-induced luminescence (PIL) of REEs in luminescent matrixes. Presently, PIL is mostly sensitive to Eu, Sm, Dy, Gd, and Pr. The main advantage of the proposed technique is that both molecular emission and PIL are characterized by long plasma lifetimes, tens and hundreds of microseconds, when nearly all interfering emissions do not practically exist. Furthermore, the relatively broad emission and luminescence bands and lines enable us to use spectroscopic equipment with a relatively low spectral resolution. It is important to emphasize that the proposed experiments (atomic LIBS, molecular LIBS and PIL) are performed with the same experimental setup and from the same plasma source. Only the detection parameters (spectral range and spectrometer slit, as well as the ICCD gain, delay and width) are modified. As result, imaging of REEs becomes more sensitive and less sophisticated. As an illustration, two imaging experiments are shown to emphasize the high complementarity of these three approaches for the detection of REEs