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In this study, the feasibility of measuring the Sb content in different plastic materials by laser induced plasma spectroscopy (LIBS) is explored. Measurements were performed initially on a sample of pure Sb in order to identify the most prominent element transitions before different consumer plastics of varying matrix, composition and color were examined. The experimental set-up was based on a single pulse laser excitation at 1064 nm and a detection system consisting of an array of three compact spectrometers covering the range 236–796 nm. On pure Sb material, many atomic lines, particularly intense in the UV region, were observed, together with much weaker ionic transitions mainly in the visible spectral region. Unfortunately, all of the strong Sb transitions partially overlapped with those from Si, Fe and Ti, elements common in many plastic materials. For constructing the calibration curve for Sb content we exploited the Sb concentration values obtained by X-ray fluorescence (XRF) spectrometry, which varied from the detection limit (∼200 ppm) up to 65 000 ppm. The analytical Sb I line at 276.99 nm was selected because, even if it has a weak contribution from one Fe I transition, its empirical subtraction leads to a well-correlated linear calibration graph. The corresponding detection limit was around 1400 ppm while in the absence of Fe, having an intense ionic transition at 259.93 nm, it is possible to use a more intense Sb I transition at 259.81 nm, achieving sensitivity on the order of 100 ppm. [ABSTRACT FROM AUTHOR]

We studied changes in laser-induced breakdown spectroscopy (LIBS) signal intensity with the thickness of a liquid layer placed on a solid substrate, where an easily evaporating methanol sample was used. For a certain optimal liquid film thickness we obtained a manifold increase of the LIBS signal from methanol. Progressive liquid film thinning leads to a reduction and a successive disappearance of laser-induced splashes; the latter condition drastically reduces the sample consumption and allows measurements to be repeated many times on a single liquid droplet. In following, we developed two methods for actively controlled deformation, i.e., thinning of a liquid droplet (volume ~10 μl) prior to its sampling by LIBS. Control of the droplet's height was achieved on a Si-SiO2 wafer substrate by electro-wetting in the case of water solutions or by target rotation in the case of viscous liquids. The chosen substrate also has the advantages of low cost, easy manipulation, and very high purity, thus minimizing interference with analytes. Through the droplet deformation, in a single-pulse excitation at moderate laser energy (70 mJ), we clearly detected Fe and Mn in peanut oil, which represent trace elements in edible oils (~1 part per billion), according to results published in the literature. [ABSTRACT FROM AUTHOR]

Abstract: With the aim to study alteration processes of the rock hewn churches from Lalibela (Ethiopia), we applied Laser Induced Breakdown Spectroscopy (LIBS) technique to measure the elemental composition both of the bulk rock materials and their external layers, exposed to the environmental factors. The analytical plasma was generated by nanosecond pulses of an Nd: YAG laser emitting at 1064 nm. Different major and minor sample constituents were detected, including Ca, Mg, Na, Fe, Ti, Al and K. The detected O emission originates both from air surrounding and the sample, while the intensity of N lines, coming exclusively from air, was used for the LIBS signal normalization. By depth profiling of the weathered basalt rock, we observed a lower presence of K in the external layers, corresponding to the first 5 laser shots. The emission from this element is anti-correlated with the line intensities from O, and this was attributed to the variations in relative abundances of clay minerals and K-feldspar. The analogue measurements were performed on the tuff rock, and compared to the spectra from powder samples containing only the external soft material, scratched from the rocks. These analyses show an abundance of H in the weathered, wetted layers and suggest that cations are lost from the constituent primary minerals and replaced by H+; this process disrupts the lattice structure and causes a marked loss of strength. The studies presented here demonstrate that LIBS is a useful technique for studying the alteration processes in the rocks, caused by environmental factors. [Copyright &y& Elsevier]

Laser-induced breakdown spectroscopy (LIBS) was tested for all of the relevant issues in forensic examinations of commercial inks, including classification of pen inks on one paper type and on different paper types, determination of the deposition order of layered inks, and analysis of signatures and toners on one questioned document. The scope of this work was to determine the potential of a single LIBS setup that is compatible with portable instruments for different types of ink analysis, rather than building a very large database for inks and papers. We identified up to seven metals characteristic for the examined inks, which allowed to fully discriminate all eight black inks on one type of printing paper. When the inks were tested on ten different papers, the correct classification rates for some of them were reduced for reasons thoroughly studied and explained. The replicated tests on three crossing points, each one involving a pair of blue or black inks, were successful in five cases out of six. In the test simulating documents of forensic interest (questioned documents), LIBS was able to correctly identify the differences in three inks used for signatures on one of the three pages and the use of different printing inks on each page of the document. [ABSTRACT FROM AUTHOR]

Here, we describe an innovative Integrated Laser Sensor (ILS) that combines four spectroscopic techniques and two vision systems into a unique, transportable device. The instrument performs Raman and Laser-Induced Fluorescence (LIF) spectroscopy excited at 355 nm and Laser-Induced Breakdown Spectroscopy (LIBS) excited at 1064 nm, and it also detects Laser Scattering (LS) from the target under illumination at 650 nm. The combination of these techniques supplies information about: material change from one scanning point to another, the presence of surface contaminants, the molecular and elemental composition of top target layers. Switching between the spectroscopic techniques and the laser wavelengths is fully automatic. The instrument is equipped with an autofocus and it performs scanning with a chosen grid density over an interactively-selected target area. Alternative to the spectroscopic measurements, it is possible to switch the instrument to a high magnification target viewing. The working distances tested until now are between 8.5 and 30 m. The instrument is self-powered and remotely controlled via wireless communication. The ILS has been fully developed at ENEA for security applications and it was successfully tested in two outdoor campaigns where an automatic recognition of areas containing explosives in traces had been implemented. The strategies for the identification of nitro-compounds placed on various substrates as fingerprints and the results obtained at a working distance of 10 m are discussed in the following. [ABSTRACT FROM AUTHOR]

In this work we report on the Laser-Induced Breakdown Spectroscopy (LIBS) characterization of the Frascati Tokamak Upgrade (FTU) first wall (FW) and toroidal limiter after the spring-summer 2019 experimental campaign. We performed our analysis by using a compact LIBS system mounted on the FTU robotic arm, entering the FTU vacuum vessel (VV) and measuring the FW elements in-situ. The LIBS system was expressly designed and developed for this task and, to our knowledge, it represents the first prototype of LIBS mounted on a robotic arm for analyses inside a tokamak. It allows to perform measurements at (1) atmospheric pressure or (2) in vacuum (down to 10−2–10−3 mbar) or (3) under gas flux (He, Ne, Ar etc.) and is suitable for 4) single pulse or 5) double pulse LIBS measurements. The LIBS analyses revealed the main chemical components of the stainless-steel FTU FW, Mo and Ti from the Titanium-Zirconium-Molybdenum alloy (TZM) tiles of the toroidal limiter. A superficial contamination of Li, originating from past liquid lithium limiter experiments was also clearly revealed. To simulate a LIBS analysis of a component of the ITER divertor region we placed a metallic sample at the bottom of the FTU VV through a sample holder and we measured it with the LIBS system. The stratigraphy of this ITER-like sample, composed of an Al/D superficial layer 3 μm thick (D 5% atomic concentration, Al as proxy for Be) on a W substrate simulates ITER PFCs in the divertor baffle and was characterized with high axial resolution (few hundreds nm for each laser shot) although the D signal from the D α emission line at 656.1 nm was found strongly interfering with the corresponding H α emission at 656.28 nm from the environmental hydrogen. [ABSTRACT FROM AUTHOR]