Elevated concentrations of mercury in soils are quite hazardous to flora and fauna and water bodies near these soils. This makes continuous monitoring of mercury very essential. This work compares two potential spectroscopic methods LIBS and SIBS at their optimum experimental conditions for mercury monitoring. The experimental conditions for Hg measurements with LIBS and SIBS were determined and calibration was developed. The limits of detection (LODs) of Hg in soil were calculated from the Hg calibration curves. The LOD for mercury (Hg) in soil calculated using LIBS and SIBS are 483 parts-per-million and 20 parts-per-million, respectively. The present study indicates that SIBS is more efficient with powder samples in a low concentration region for quantification of mercury in soils while LIBS is efficient in the region of higher concentrations using pellet samples. Both these techniques can be further investigated and improved for in-situ analysis of soils.

The detection of trace amounts of H and D present in Zr-2.5%Nb in the form of ZrH and ZrD, respectively, by LIBS was explored. The intended use case for this experimentation was CANada Deuterium Uranium (CANDU) nuclear reactor pressure tube inspections where hydride buildup can lessen the mechanical strength of these components. As these tubes carry coolant and house the fuel bundles, their integrity is paramount. A LIBS inspection method is of interest in the nuclear industry due to the operational flexibility it would introduce and its ability to reduce the cost, time, and radiation dose associated with inspection campaigns of pressure tubes in CANDU nuclear reactors. Using LIBS, simultaneous detection of H and D was achieved in a low-pressure air environment using a microjoule, picosecond pulsed laser and emission being captured by a high-resolution spectrometer. The emission lines of the two species were blended, however, two peaks can be seen. Experiments using a milijoule, nanosecond pulsed laser in a LIBS setup were also conducted at atmospheric pressures. These experiments failed to show D emission, however. In addition to detecting emission from H and D, a Monte Carlo algorithm was developed for estimating the error associated with a LIBS inspection of a pressure tube segment. ZrH and ZrD form heterogeneous structures in the bulk of the Zr-2.5%Nb pressure tube material, meaning that a single measurement would not be indicative of the entire tube. Using metallographs of artificially hydrided pressure tube samples, the error within a given confidence interval was found as a function of number of measurement sites and ablation diameter. Furthermore, the impacts to Zr-2.5%Nb based on intense laser-matter interactions was investigated by optical microscopy and interferometry, allowing for 3-dimensional reconstructions of ablation craters. The morphology of millijoule, nanosecond pulsed laser-matter interaction and microjoule, picosecond pulsed laser-matter interaction were the subjects of this investigation. The salient difference between the two interactions is the evidence of substantial melting and subsequent re-deposition of material in the case of nanosecond interactions, whereas picosecond ablation yielded little melting. These results support the further development of a LIBS-based inspection method for determining the concentration of H and D in Zr-2.5%Nb. It was found that a vacuum environment allows for the simultaneous detection of H and D emission. Further experimentation should explore using low-pressure buffer gas environments as a method to further distinguish emission between the two species. / Thesis / Master of Applied Science (MASc)

The laser beam interaction with matter and the plasma generation have been studied for many years. In some applications what is really important is to understand the composition and the temporal evolution of the species in the interested medium. In this thesis, time resolved optical spectroscopy was employed to understand the evolution of the plasma which is produced by interaction of Infrared (1.064 &micro / m) laser beam with air. In this thesis, a new technique is suggested to analyze the time evolution of laser induced breakdown spectroscopy. The suggested method and the instrumentation of the setup are tested with a single gas (He). After the tests, we analyzed time sequence spectra of Laser Induced Air Breakdown. The suggested method is based on triggering the laser and the spectrometer at different time and applying the spectrometer trigger time by adding the time delay (&amp / #916 / t) between them by using the pulse generator. The results show that the decay rates are slowing down microseconds after the excitation of the plasma. The results of the time-resolved measurements of the line spectra show that different component of the air has different decay rate, and lifetime. The lifetime of helium is 20 &micro / s, and the decay start 5 &micro / s after the initiation of plasma. Air has 12 &micro / s lifetime, and the decay start 3 &micro / s after the initiation of the plasma. Also, the decay rate and the lifetime depend on the state. We also calculate Doppler velocity for different component and different emission states. Doppler velocities show that the component which has great mass has small velocity, the component which has small mass has high velocity.

Sur Mars, la datation par comptage de densité de cratères est actuellement la seule méthode utilisée pour dater les surfaces planétaires. Cependant, sur Mars, elle n’a pas encore été corrigé et complété par des datations absolues. Ce travail consiste à développer un prototype démontrant le potentiel d’une nouvelle approche expérimentale basée sur la méthode K-Ar pour dater les roches martiennes in situ. L’objectif à terme est de proposer une solution instrumentale de datation absolue pour un futur rover d’exploration.Un laser Nd :YAG quadruplé pour tirer à 266 nm ablate un échantillon basaltique mis sous vide secondaire. L’observation du plasma par « Laser Induced Breakdown Spectroscopy » apporte des informations sur la concentration en K et sur la nature chimique et minéralogique de la cible. Puisque l’ablation est faite par un laser UV et sous vide secondaire, l’ablation est reproductible par minéralogie. La reconnaissance stoechiométrique permet donc d’estimer la masse vaporisée. Après purification des gaz libérés, un spectromètre de masse quadripolaire détermine la quantité d’argon.L’ensemble de ces mesures pourvoit un âge avec une incertitude théorique de 13% dans les meilleures conditions.Les calibrations du dispositif expérimental ont apporté de nombreuses informations sur des effets sur les spectres LIBS provoqués par l’ablation sous vide secondaire. L’augmentation de la pression e tla variation de géométrie du cratère d’ablation ont des effets opposés sur les pics des éléments.Nous avons aussi démontré que l’instrument était capable de mesurer l’âge de la mésostase de roche basaltique et qu’il offre des perspectives intéressantes sur certaines phases minérales comme la biotite. / Crater counting is the only method used on Mars to give relative geochronological information but it never had been fitted and corrected by absolute geochronology. This work is about the development of a new prototype demonstrating the ability of a protocol using in situ K-Ar dating. The goal is to propose a solution of an absolute geochronology for the next explorations rovers. A quadrupled Nd:YAG laser at 266 nm ablates a basaltic sample under high vacuum. The light collection by a spectrometer (Laser Induced Breakdown Spectroscopy) gives the rate of potassium and the chemical or the mineralogy of the target. Thanks to the specificities of the ablation in highvacuum and with a UV laser, the ablated mass has a good reproducibility per mineralogy. Thus, theLIBS identification gives an estimation of the ablated mass. After the purification of the released gas,a quadrupole mass spectrometer determines the quantity of argon. All these measures give an age with a theoretical uncertainty of 13% in the best conditions.The calibration of the experiment had given new information about the effects on LIBS spectrarelated to the ablation under high vacuum. The rise of the pressure and the variation of geometry of the pit have opposite effects on the elements peaks. We also demonstrated that the instrument was capable of measuring the age of the groundmass of basalt and has some interesting perspectives on some mineral phases such as biotite.

Laser Induced Breakdown Spectroscopy (LIBS) which is used to determine the elemental content of various samples, inspects the emission spectroscopy of samples of interest for searching certain elements or identifying the unknown content. In this study, spectroscopic analyses of various kinds of metals, namely, Cu, Fe, Mo, Ti, W, some compounds such as CuBe, ZnSe, ZnS, GaSe, some semimetals like Si, Ge and even gases were investigated by means of a compact-commercial portable LIBS system and an independently constructed experimental set-up consisting of a single pulse system and various kinds of double pulse configurations using Nd:YAG lasers. The contributions of this thesis to the LIBS community can be classified into two main groups- which are experimental and code development. One of the experimental contributions was the investigation of the different crystal surfaces of silicon in which dangling bond density were taken into account for a more precise comparison of atomic emissions. The second experimental contribution was the polarization experiments by which polarization dependency, to some extent, was demonstrated. The third and final one was the orthogonal double pulse configuration with a 45 o incidence angle for both lasers in opposite directions by which it was shown that the positioning becomes straightforward yielding the desired reproducible results. The second major contribution was to develop a basic code for analyzing the experimental data more accurately. In conclusion, by means of the different experimental approaches, factors relating to the enhancement in intensity were investigated and as a result of developing the code, flexibility in upgrading the constraints of element searching was obtained and the updating of the database was accomplished.

Long range stand-off Raman and Laser-Induced Breakdown Spectroscopy (LIBS) lidar signal simulations have been carried out using a modified UV-visible atmospheric transmission program and a modified lidar equation. The Hitran-PC atmospheric transmission program which normally operates over the wavelength range of 400 nm to the far-IR was modified to provide UV atmospheric attenuation (200 nm -- 400 nm) using the optical cross section data contained in the HITRAN database. The two-way lidar equation was modified in order to simulate the one-way propagation of the Raman and LIBS spectral, and thus provide calculations of the expected Raman or LIBS signal as a function of range. Estimation of the LIBS and Raman spectral intensity was then calculated for several remote sensing cases. In particular, the atmospheric attenuation spectra generated with the modified Hitran-PC program were combined with the calculated LIBS and Raman lidar emission spectra at the remote excitation site using a modified lidar equation to determine for the first time to our knowledge the power and S/N ratio versus range of the LIBS and Raman Lidar complete spectrum as a function of wavelength in the UV -- IR region. Previous simulations had only made S/N versus range calculations at a single wavelength or for the total integrated emission. These results are important as they can be used for future design of stand-off LIBS and Raman lidar systems, and for comparisons with experimental measurements. In particular, we are planning to use our simulations for comparison of 266 nm excited LIBS and Raman lidar measurements of energetic compounds at ranges of a few tens of meters.

Thesis (Ph.D.)--Mississippi State University. Department of Physics and Astronomy. / Title from title screen. Includes bibliographical references.

La recherche des phases hydratées à la surface de Mars est essentielle à la compréhension de son passé habitable et des changements climatiques globaux qu'elle a subis. Le rover MSL/Curiosity apporte de nouveaux moyens pour caractériser l'hydratation de la surface. En particulier, la spectroscopie de plasma induite par laser (LIBS) de l'instrument ChemCam mesure la composition élémentaire à distance. Il permet une détection de l'hydrogène par le pic d'émission H Balmer alpha à 656.6 nm. Cependant la quantification de cet élément n'a été que très peu étudiée. Le modèle de qualification de l'instrument ChemCam a été intégré à un banc LIBS afin d'analyser des séries d'échantillons hydratés au laboratoire. A l'exception de quelques échantillons révélant des phénomènes spécifiques à l'hydrogène, ces tests montrent qu'un étalonnage linéaire est obtenu avec la teneur en eau. Sur Mars, dans le cratère Gale, cette calibration révèle l'hydratation de différentes phases : la bassanite (CaSO4 × 0.5H2O) dans les veines remplissant les fractures des roches, les sulfates de magnésium, les sédiments opalifères et argileux découverts in situ. Les mesures d'abondances en eau effectuées jusqu'à présent étaient restreintes à de rares expériences de pyrolyse ; cette étude montre que ChemCam apporte maintenant un nouveau moyen opérationnel pour la mesure de l'hydrogène à la surface, à l'échelle submillimétrique et couvrant un très grand nombre de roches. / The search for hydrated phases lying at the surface of Mars is essential to understand its habitable past and the fate of water on a planet disrupted by global climate changes. The MSL/Curiosity rover provides new tools to characterize surface hydration in situ. Among these, laser induced breakdown spectroscopy (LIBS) performed by the ChemCam instrument enables remote measurement of elementary abundance. However, measuring the LIBS emission peak of hydrogen at 656.6 nm (Balmer alpha) to quantify target water content is poorly documented in the literature. Using the instrument replica, large series of hydrated samples have been analyzed in the laboratory under Martian atmospheric conditions. Except for some samples on which effects specific to the hydrogen signal have been observed, these tests show that a linear calibration can be obtained with target water content. On Mars, at Gale crater, this calibration reveals the hydration of different phases: bassanite (CaSO4 × 0.5H2O) in the veins filling the bedrock fractures, magnesium sulfates, opaline and clay rich sediments discovered in situ. Measurement of water content performed to date have been limited to sparse and bulk pyrolysis experiments; this study shows that ChemCam provides a new technique to measurement hydrogen on the surface, at a submillimeter scale and sampling a very large number of rocks.

L’analyse en ligne et in situ constitue aujourd’hui un axe de développement stratégique pour la chimie analytique. C’est particulièrement vrai dans le domaine nucléaire pour lequel les contraintes de sécurité liées à la radioactivité des échantillons, et la nécessité de limiter au maximum les déchets issus des analyses, plaident en faveur de techniques de mesure à distance, sans prélèvement ni préparation d’échantillon. La spectroscopie d’émission de plasma créé par laser (ou LIBS pour laser-induced breakdown spectroscopy), technique d’analyse élémentaire des matériaux basée sur l’ablation laser et la spectroscopie d’émission optique, possède ces qualités. C’est donc une technique de choix pour l’analyse en ligne. Cependant, la maîtrise de la mesure est délicate pour plusieurs raisons. D’abord, la LIBS est multiparamétrique et l’effet des paramètres expérimentaux sur les performances analytiques n’est pas toujours clairement établi. Ensuite, les phénomènes physiques donnant lieu au signal LIBS sont non linéaires, couplés, et transitoires. Enfin, un système d’analyse en ligne doit être le plus robuste possible face aux variations non contrôlées des conditions de mesure. L’objectif de cette thèse est donc d’améliorer la maîtrise et les performances de l’analyse quantitative par LIBS en utilisant des méthodes multivariées capables de gérer la multidimensionalité, la non linéarité et le couplage des paramètres et des données. Pour cela, le travail se décompose en deux parties. Dans un premier temps, nous avons réalisé un plan d’expériences composite centré visant à relier les paramètres expérimentaux de l’ablation laser (énergie de l’impulsion et paramètres de focalisation du faisceau) et de la détection du signal (délai après le tir laser) aux caractéristiques physiques du plasma (masse ablatée, température) et aux performances analytiques (intensité et répétabilité du signal). L’optimisation des paramètres qui en résulte est alors interprétée comme le meilleur compromis, pour l’analyse quantitative, entre efficacité d’ablation laser et chauffage du plasma. Dans un deuxième temps, nous avons développé une méthodologie multivariée basée sur les techniques MCR-ALS, ICA et PLS, pour quantifier certains éléments dans différentes matrices métalliques en exploitant, en plus de la dimension spectrale habituelle, la dimension temporelle du signal LIBS. Cette dernière, pourtant essentielle, est généralement négligée dans la littérature. Dans cette partie, nous discutons donc de l’intérêt de cette approche par rapport aux méthodes usuelles de quantification (univariée et multivariée), et de l’apport de cette méthodologie pour diagnostiquer, comprendre et éventuellement compenser les effets de matrice observés en LIBS. / Online and in situ analysis is now a strategic development for analytical chemistry. This is especially true in the nuclear field for which the security constraints related to the radioactivity of samples, and the need to minimize waste from analyzes argue for remote measurement techniques without sampling or sample preparation. Laser-Induced Breakdown Spectroscopy (LIBS) technique for elemental analysis of materials based on laser ablation and the optical emission spectroscopy, has these qualities. It is a technique of choice for online analysis. However, the processes involved in LIBS, namely laser ablation, atomization, plasma formation and emission, are quite complex and difficult to control because the underlying physical phenomena are coupled and nonlinear. In addition, the analytical performance of the LIBS technique depends strongly on the choice of experimental conditions. Finally, an online analysis system should be as robust as possible face to uncontrolled variations in measurement conditions. The processes involved in LIBS, namely laser ablation, atomization, plasma formation and emission, are quite complex and difficult to control because the underlying physical phenomena are coupled and nonlinear. In addition, the analytical performance of the LIBS technique depends strongly on the choice of experimental conditions. The objective of this thesis is to improve control and performance of quantitative analysis by LIBS using multivariate methods capable of handling multi-dimensionality, nonlinearity and the coupling between parameters and data. For this, the work is divided into two parts. First the optimization is carried out using a central composite design to model the relationship between the experimental parameters of laser ablation (pulse energy and beam focusing parameters) and signal detection (delay time) to the physical characteristics of plasma (ablated mass, temperature) and the analytical performance (intensity and repeatability of the signal). The optimization parameters that results is then interpreted as the best compromise for the quantitative analysis between efficiency of laser ablation and plasma heating. Secondly, we developed a multivariate methodology based on MCR-ALS, ICA and PLS techniques to quantify certain elements in different metallic matrices operator, in addition to the usual spectral dimension, the time dimension of LIBS signal. In this part, we discuss the value of this approach over conventional methods of quantification (univariate and multivariate) and the contribution of this methodology to diagnose, understand and possibly compensate matrix effects observed in LIBS.

Táto diplomová práca sa zaoberá klasifikáciou kovov pomocou spektroskopie laserom indukovanej plazmy (LIBS) a chemometrických metód. Práca poskytuje prehľad o štúdiách na danú tému. Sú vybrané tri široko používané chemometrické klasifikačné metódy: "Soft Independent Modeling of Class Analogy" (SIMCA), "Partial Least Squares Discriminant Analysis" (PLS-DA) a variácia umelých neurónových sietí (ANN), "Feedforward Multilayer Perceptron". Rôzne prístupy k prieskumovej analýze su tiež preskúmané. Metódy sú stručne opísané. Následne sú klasifikátory experimentálne porovnané.