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1
Cousin, Agnès. "LIBS (Laser-induced breakdown spectroscopy) pour l'exploration martienne." Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1655/.
Abstract:
ChemCam est à bord de la mission Mars Science Laboratory (MSL) qui a décollé pour Mars le 26 novembre 2011. Cet instrument est très innovant car c'est la première fois que la technique du LIBS ("Laser-Induced Breakdown Spectroscopy") est utilisée pour l'exploration planétaire, afin d'étudier la géochimie des sols et roches à la surface de la planète rouge. Cette technique permet de déterminer la composition chimique de la cible analysée, en focalisant un laser à sa surface. Un plasma se créé alors par échauffement de la matière. L'analyse spectrale de la lumière émise du plasma permet d'identifier les éléments présents dans la roche, ainsi que leur concentration. Ce travail de thèse contribue à la préparation du retour scientifique de la mission MSL et de l'instrument ChemCam autour de quatre axes principaux : (i) identification et caractérisation des raies spectrales pertinentes, (ii) test des méthodes de classification des roches avec ces mesures, (iii) étude de la sensibilité aux vernis d'altération des roches ou à la couche de poussière, (iv) analyse des données pour extraire des informations sur la structure et la composition des roches. Une station sol a été développée afin de reproduire les conditions atmosphériques à la surface de Mars. Une bibliothèque de raies élémentaires a été réalisée. Cette dernière est spécifique à ChemCam et à la géochimie de Mars, et contient plus de 1300 raies. Les outils de classification des roches avec les données de ChemCam se sont montrés efficaces. ChemCam permet de réaliser des analyses quantitatives, que ce soit par des méthodes statistiques ou plus conventionnelles. Nous avons montré que cet instrument est capable d'analyser aussi-bien la couche d'altération d'un basalte que la roche saine au dessous. Il permet également d'effectuer des analyses très fines, comme la comparaison de différentes matrices de roches volcaniques, ou encore de la structure interne des argiles. Pour finir, ces études expérimentales réalisées durant la thèse ont démontré que ChemCam répondait à toutes les spécifications imposées au début de sa conceptionChemCham is onboard the Mars Science Laboratory (MSL) mission, which was launched the 26th November 2011. This instrument uses the LIBS (Laser-Induced Breakdown Spectroscopy) technique to study the geochemistry of the Martian surface. This technique is used for the first time for the Space and Planetary exploration. In LIBS technique a pulsed laser beam is focused on a target, creating a plasma. The spectral analysis of the plasma light is collected to observe the characteristic emission lines of the elements present in the sample. This work contributes to the preparation of the scientific returns of the MSL mission but also of ChemCam, with four principal axes: - identification and characterization of the significant elemental lines, - test of the method used to distinguish rocks with these measurements, study of the capacity to analyze the alteration coating on rocks, - data analysis to extract informations about the structure and/or composition of rocks A ground station was developed in order to be representative of the Martian surface conditions. An elemental lines database specific of ChemCam and Mars is performed, with up to 1300 lines. Several experimental studies let us to characterize some of the ChemCam capabilities. First, rocks classification is successful whatever the kind of the sample. Some parameters were studied to understand their influence on the classifications. Then, quantitative analysis with ChemCam are feasible, not only using statistical methods. We show that ChemCam is able to analyze the composition of the alteration coating before the one from the unaltered rock, deeper. It is also able to make some differences between several kinds of basalts with their texture and matrix, and between several kinds of clays, looking at their internal structure
2
Cousin, Agnès. "LIBS (Laser-Induced Breakdown Spectroscopy) pour l'observation martienne." Phd thesis, Université Paul Sabatier - Toulouse III, 2012. http://tel.archives-ouvertes.fr/tel-00717266.
Abstract:
ChemCam est à bord de la mission Mars Science Laboratory (MSL) qui a décollé pour Mars le 26 novembre 2011. Cet instrument est très innovant car c'est la première fois que la technique du LIBS ("Laser-Induced Breakdown Spectroscopy") est utilisée pour l'exploration planétaire, afin d'étudier la géochimie des sols et roches à la surface de la planète rouge. Cette technique permet de déterminer la composition chimique de la cible analysée, en focalisant un laser à sa surface. Un plasma se créé alors par échauffement de la matière. L'analyse spectrale de la lumière émise du plasma permet d'identifier les éléments présents dans la roche, ainsi que leur concentration. Ce travail de thèse contribue à la préparation du retour scientifique de la mission MSL et de l'instrument ChemCam autour de quatre axes principaux : (i) identification et caractérisation des raies spectrales pertinentes, (ii) test des méthodes de classification des roches avec ces mesures, (iii) étude de la sensibilité aux vernis d'altération des roches ou à la couche de poussière, (iv) analyse des données pour extraire des informations sur la structure et la composition des roches. Une station sol a été développée afin d'imiter les conditions atmosphériques à la surface de Mars. Une bibliothèque de raies élémentaires a été réalisée. Cette dernière est spécifique à ChemCam et à la géochimie de Mars, et contient plus de 1300 raies. La classification des roches est efficace, quelque soit le type de cible. Les différents paramètres (distance, traitement des données, ..) pouvant influencer ces classifications ont également été caractérisés. ChemCam permet de réaliser des analyses quantitatives, que ce soit par des méthodes statistiques ou plus conventionnelles. Nous avons montré que cet instrument est capable d'analyser aussi-bien la couche d'altération d'un basalte que la roche saine au dessous. Il permet également d'effectuer des analyses très fines, comme la comparaison de différentes matrices de roches volcaniques, ou encore de la structure interne des argiles. Pour finir, ces études expérimentales réalisées durant la thèse ont démontré que ChemCam répondait à toutes les spécifications imposées au début de sa conception.
3
Pořízka, Pavel. "Using Laser-Induced Breakdown Spectroscopy (LIBS) for Material Analysis." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-234214.
Abstract:
Tato doktorská práce je zaměřena na vývoj algoritmu ke zpracování dat naměřených zařízením pro spektrometrii laserem indukovaného plazmatu (angl. LIBS). Zařízení LIBS s tímto algoritmem by mělo být následně schopno provést třídění vzorků a kvantitativní analýzu analytu in-situ a v reálném čase. Celá experimentální část této práce byla provedena ve Spolkovém institutu pro materiálový výzku a testování (něm. BAM) v Berlíně, SRN, kde byl sestaven elementární LIBS systém. Souběžně s experimentílní prací byl vytvořen přehled literárních zdrojů s cílem podat ucelený pohled na problematiku chemometrických metod používaných k analýze LIBS měření. Použití chemometrických metod pro analýzu dat získaných pomocí LIBS měření je obecně doporučováno především tehdy, jsou-li analyzovány vzorky s komplexní matricí. Vývoj algoritmu byl zaměřen na kvantitativní analýzu a třídění vyvřelých hornin na základě měření pomocí LIBS aparatury. Sada vzorků naměřených použitím metody LIBS sestávala z certifikovaných referenčních materiálů a vzorků hornin shromážděných přímo na nalezištích mědi v Íránu. Vzorky z Íránu byly následně na místě roztříděny zkušeným geologem a množství mědi v daných vzorcích bylo změřeno na Univerzitě v Clausthalu, SRN. Výsledné kalibrační křivky byly silně nelineární, přestože byly sestaveny i z měření referenčních vzorků. Kalibrační křivku bylo možné rozložit na několik dílčích tak, že závislost intenzity měděné čáry na množství mědi se nacházela v jiném trendu pro jednotlivé druhy hornin. Rozdělení kalibrační křivky je zpravidla přisuzováno tzv. matričnímu jevu, který silně ovlivňuje měření metodou LIBS. Jinými slovy, pokud určujeme množství analytu ve vzorcích s různou matricí, je výsledná kalibrační křivka sestavená pouze z jedné proměnné (intenzity zvolené spektrální čáry analytu) nepřesná. Navíc, normalizace takto vytvořených kalibračních křivek k intenzitě spektrální čáry matrčního prvku nevedla k výraznému zlepšení linearity. Je obecně nemožné vybrat spektrální čáru jednoho matričního prvku pokud jsou analyzovány prvky s komplexním složením matric. Chemometrické metody, jmenovitě regrese hlavních komponent (angl. PCR) a regrese metodou nejmenších čtverců (angl. PLSR), byly použity v multivariační kvantitatvní analýze, tj. za použití více proměnných/spektrálních čar analytu a matričních prvků. Je potřeba brát v potaz, že PCR a PLSR mohou vyvážit matriční jev pouze do určité míry. Dále byly vzorky úspěšně roztříděny pomocí analýzy hlavních komponent (angl. PCA) a Kohonenových map na základě složení matričních prvků (v anglické literatuře se objevuje termín ‚spectral fingerprint‘) Na základě teorie a experimentálních měření byl navržen algoritmus pro spolehlivé třídění a kvantifikaci neznámých vzorků. Tato studie by měla přispět ke zpracování dat naměřených in-situ přístrojem pro dálkovou LIBS analýzu. Tento přístroj je v současnosti vyvíjen v Brně na Vysokém učení technickém. Toto zařízení bude nenahraditelné při kvantifikaci a klasifikaci vzorků pouze tehdy, pokud bude použito zároveň s chemometrickými metodami a knihovnami dat. Pro tyto účely byla již naměřena a testována část knihoven dat v zaměření na aplikaci metody LIBS do těžebního průmyslu.
4
Zwilling, Melissa. "Analysis of White Latex Paints using Laser Induced Breakdown Spectroscopy for Forensic Applications." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1590.
Abstract:
The analysis of white latex paint is a problem for forensic laboratories because of difficulty in differentiation between samples. Current methods provide limited information that is not suitable for discrimination. Elemental analysis of white latex paints has resulted in 99% discriminating power when using LA-ICP-MS; however, mass spectrometers can be prohibitively expensive and require a skilled operator. A quick, inexpensive, effective method is needed for the differentiation of white latex paints.
In this study, LIBS is used to analyze 24 white latex paint samples. LIBS is fast, easy to operate, and has a low cost. Results show that 98.1% of variation can be accounted for via principle component analysis, while Tukey pairwise comparisons differentiated 95.6% with potassium as the elemental ratio, showing that the discrimination capabilities of LIBS are comparable to those of LA-ICP-MS. Due to the many advantages of LIBS, this instrument should be considered a necessity for forensic laboratories.
5
Hudson, Shaymus W. "Inclusion Detection in Liquid Aluminum Via Laser-Induced Breakdown Spectroscopy." Digital WPI, 2016. https://digitalcommons.wpi.edu/etd-dissertations/540.
Abstract:
Aluminum alloy castings are becoming commonplace for critical applications in the automotive and aerospace industries where materials failure is not an option. In order to meet such property demands, tight control over the cleanliness of the melt (mitigation of solid particle inclusions) and microstructure must be achieved. In order to control cleanliness, it must first be well defined and measured. Very few techniques exist in industry that can quantitatively measure inclusion levels in-situ. Laser-induced breakdown spectroscopy (LIBS) is presented as a promising technique to quantify solid particles, desired or undesired, in aluminum melts. By performing LIBS with subsequent statistical analysis on liquid aluminum with varying concentrations of Al2O3, AlB2, TiB2, and SiC particles, calibration curves relating particle concentration and elemental intensity were drawn. Through metallography and automated electron microscopy, it was found that inclusions less than 10 um in size could be detected with LIBS. Concentrations down to at least one part-per-million could be detected and accurately measured, allowing for LIBS to be use as a tool for complete, real-time melt cognition.
6
Bridge, Candice. "DISCRIMINATION OF FORENSIC TRACE EVIDENCE USING LASER INDUCED BREAKDOWN SPECTROSCOPY." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2906.
Abstract:
Elemental analysis in forensic laboratories can be tedious and many trace evidence items are not analyzed to determine their elemental composition. Presently, scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDS) is the primary analytical tool for determining the elemental composition of trace evidence items. However, due to the time it takes to obtain the required vacuum and the limited number of samples that can be analyzed at any one time, SEM-EDS can be impractical for a high volume of evidence items. An alternative instrument that can be used for this type of analysis is laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). While LA-ICP-MS is a very precise and quantitative analytical method that determines elemental composition based on isotopic mass measurements; however, the instrumentation is relatively expensive and therefore is budgetarily prohibitive for many forensic laboratories. It is the purpose of this research to evaluate an inexpensive instrument that can potentially provide rapid elemental analysis for many forensic laboratories. Laser induced breakdown spectroscopy (LIBS) is an analytical method that meets these requirements and offers information about the elemental composition based on ionic, atomic and diatomic molecular emissions.Ph.D.
Department of Chemistry
Sciences
Chemistry PhD
7
Effenberger, Andrew Jay. "Methods for measurement of heterogeneous materials with laser-induced breakdown spectroscopy (LIBS)." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3369015.
Abstract:
Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed September 15, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
8
Cervantes, Cesar. "Laser induced breakdown spectroscopy (LIBS) applied to the quantification of elements in fertilizers." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/75/75135/tde-20042017-101150/.
Abstract:
A capacidade do instrumento Laser Induced Breakdown Spectroscopy (LIBS) foi investigada para a possibilidade de atuar como uma ferramenta de quantificação. Um instrumento de baixo custo fechado do dispositivo de acoplamento de cargas (CCD) foi utilizado a fim de quantificar (K), (Ca), (Mn), (Mg), e (Cu) presente em 26 amostras de fertilizantes constituídos de diferentes matrizes, alguns fosfato de organo-mineral e outros de material inorgânico (quantificação de elementos presentes em fertilizante organominerais nunca tinha acontecido). Duas técnicas de referências foram utilizadas para validar as habilidades de quantificação: Plasma Acoplado Indutivo-Espectroscopia de Emissão Ótica (ICP-OES) e Espectroscopia de Absorção Atômica (AAS). O melhor pico representando cada elemento foi encontrado para produzir a melhor correlação entre cada pixel CCD e a concentração de elementos obtidos a partir das técnicas de referência. O pico mais adequado de LIBS foi tratado com um procedimento de normalização, a fim de corrigir os efeitos de matriz e as pequenas flutuações no plasma. Após o pico produzido por LIBS ser normalizado, foi linearmente montado contra os dados das duas técnicas de referência e duas curvas de calibração para cada um dos elementos foram construídas. Quando o procedimento de normalização não foi aplicado, valores de R-quadrado diminuiu entre 0,1-0,2 em quase todos os elementos. No entanto, entre os resultados produzidos pelas duas curvas de calibração, após o procedimento de normalização ser aplicado, os valores de correlação R-quadrado variaram de 0,8-0,98, o que foi considerado adequado para os elementos de interesse. O LOD para LIBS também foi calculado e verificou-se que quando os valores estavam abaixo do limite de determinação, a validade de LIBS como uma ferramenta de quantificação diminuiu. Além disso, uma análise de erro de validação cruzada foi feita com LIBS-ICP e LIBS-AAS, o que originou valores de erro de 22% - 28% para alguns dos elementos, quando todas as amostras foram incluídas. Mas quando as amostras abaixo do LOD foram excluídas, aqueles valores de erro desceram significativamente, e resultou na gama de 7% - 20%. Uma análise de validação cruzada também foi feita para as concentrações dos elementos determinados pelas técnicas de referência e esses resultados produziram valores de erro variando de 9% - 23%. As semelhanças entre os valores de erro LIBS e os valores de erro das técnicas de referência, dá credibilidade para a capacidade de LIBS para atuar como uma ferramenta para a quantificação de elementos presentes em fertilizantes compostos de diferentes matrizes.The ability of the instrument Laser Induced Breakdown Spectroscopy (LIBS) was investigated for the possibility of acting as a quantification tool of analysis. A low-cost gated charged coupled device (CCD) was used in order to quantify (K), (Ca), (Mn), (Mg), and (Cu) present in 26 fertilizer samples made up of different matrixes, some of organic-mineral phosphate and others of inorganic material; evaluation of elements in organomineral fertilizers had never been done by LIBS. Two reference techniques were used in order to validate the quantification abilities: Inductive Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Atomic Absorption Spectroscopy (AAS). The best peak representing each element was found by finding the best correlation between each CCD pixel and the element concentration obtained from the reference techniques. The most appropriate peak from LIBS was treated with a normalization procedure in order to correct for physical matrix effects and small plasma fluctuations. After the LIBS peak was normalized, it was linearly fitted against the data from the two reference techniques, thus two calibration curves for each element were built. When the normalization procedure was not applied, R-squared values decreased between 0.1 - 0.2 in almost all the elements. However, amongst the results of the two calibration curves after the normalization procedure was applied, R-squared correlation values ranged from 0.8-0.98, which were considered adequate for the elements of interest. The LOD for LIBS was also calculated and it was found that when values were below the LOD, the validity of LIBS as a quantification tool decreased. Moreover, a cross-validation error analysis was done with LIBS-ICP and LIBS-AAS, which yielded error values of 22% - 28% for some of the elements when all samples were included, but when samples below the LOD were excluded, those error values went down significantly, and resulted within the range of 7% - 20%. A cross-validation analysis was also done for the element concentrations determined by the reference techniques and those results yielded error values ranging from 9%- 23%. The similarities between the LIBS error values and the reference techniques error values, gives credibility to the ability of LIBS to act as a tool for quantifying elements in fertilizers composed of different matrixes.
9
Bernon, Céline. "La spectroscopie de plasma induit par laser ou LIBS (Laser-Induced Breakdown Spectroscopy) appliquée à l’analyse de surfaces contaminées par des toxiques liquides." Thesis, Paris, CNAM, 2013. http://www.theses.fr/2013CNAM0917.
Abstract:
La spectroscopie de plasma induit par laser ou LIBS (Laser-Induced Breakdown Spectroscopy)est aujourd’hui utilisée dans de nombreux secteurs d’activités du fait des atouts qu’ellepossède. Cette technologie permet de caractériser la composition élémentaired’échantillons quel que soit leur phase (gaz, solide et liquide), rapidement (10-6s), de façon insitu et sans contact, et à pression et température ambiantes. Ces caractéristiques présententun intérêt pour des applications militaires de détection de traces d’agents chimiquescontaminant une surface. L’objectif de cette étude est d’étudier le potentiel de cettetechnologie afin de détecter les espèces chimiques présentes dans les agents réels, tels quele phosphore, le fluor, le chlore et le soufre sur des surfaces d’échantillons polluésreprésentatifs de milieux opérationnels. Pour améliorer les performances analytiques de latechnique LIBS classique à simple impulsion, la configuration double impulsion estdéveloppée et comparée à la méthode simple impulsion. Son principe repose sur l’envoisuccessif de deux impulsions laser résolues générant au point focal un plasma thermique serelaxant in fine en émettant des raies spécifiques de la composition élémentaire. Les gainsanalytiques, ainsi que les limites de détection sont évalués pour plusieurs typesd’échantillons représentatifs. Une comparaison avec les seuils de détection attendus estétablieLaser-Induced Breakdown Spectroscopy (LIBS) is currently used in many fields of activity,thanks to its numerous uses. This technology allows fast measurement (10-6 s), with in situconfiguration, at ambient pressure and temperature, of different samples in gaseous, liquidor solid phase. These performances present a high interest for military applications to detectchemical agent traces on surfaces. The aim of this study is to investigate the potential of thistechnology in the detection of specific chemical atoms of live agents such as phosphorus,fluorine, chlorine, and sulfur on the surface of contaminated samples representing thetheatre. In order to improve the analytical performances of classical technical LIBS of singlepulse, a double pulse method was developed and compared to single pulse method. Itsprinciple is based on the emission of two successive laser impulsions resolved in space andtime, generating in the focal point thermal plasma which relaxes in fine emitting specificradiation of the elementary composition. The analytical gains, as for detection thresholdsare evaluated for each type of samples. A comparison of the detection thresholds isestablished
10
Subedi, Kiran. "Elemental Analysis of Printing Inks Using Tandem Laser- Induced Breakdown Spectroscopy and Laser Ablation Inductively Coupled Plasma Mass Spectrometry." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2263.
Abstract:
As a consequence of the widespread use of computers coupled to high-quality printers and different types of papers, forgery, counterfeiting, change of wills, anonymous letter writing and felonious use of the documents have become serious problems. Forensic analysts are always seeking methods that can provide reliable information on whether a specimen collected at the crime scene is linked to the crime or to a source of known origin. Sensitive methods that can provide more detailed characterization of natural or man-made materials or even provide information not previously available to forensic examiners.
Recent advances in rapid solid sampling of materials using laser ablation (LA) coupled to inductively coupled plasma mass spectroscopy (ICP-MS) have led to this analytical method to be regarded as the “gold standard” in the field of elemental analysis for trace level components in solids. Another, emerging, analytical technique that uses the same laser pulse to generate a plasma that can be interrogated with spectroscopy is laser induced break down spectroscopy (LIBS).
The analysis of ink and paper is also possible because of the surface removal effect of laser interactions with the samples. In the present study, printing inks were analyzed using LIBS, LA-ICP-MS and both of them in tandem mode. In the tandem setup, the light generated during the relaxation of the excited species (LIBS) was used to create a spectral signature of the elements, and the mass-to-charge ratio of the ejected particles (ICP-MS) was used to create a mass spectrum.
For a set of 319 printing ink samples, LA-ICP-MS alone provided discrimination greater than 99%. A subset of 43 printing inks, having a very similar elemental profile, was analyzed by tandem LIBS/LA-ICP-MS. The fusion of LIBS and LA-ICP-MS provided additional discrimination through the detection of elements like Ca, Si, Fe, and K by LIBS, that are difficult to detect and confirm using standalone ICP-MS because of the spectral interferences (isobaric and polyatomic) involved. The combination of these two sensors was found to minimize the individual limitations and provide a more complete and representative chemical characterization of printing inks.
11
Yurdanur, Tasel Elif. "Elemental Analysis Of Materials Including Silicon (100) And (111) Crystals With Single And Double Pulsed Libs." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12614304/index.pdf.
Abstract:
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.
12
Markus, Susanne. "Die laser induced breakdown spectroscopy (LIBS) als Inline-Verfahren zur Detektion von Oberflächenkontaminationen im Bereich der Klebtechnik." Aachen Shaker, 2007. http://d-nb.info/988348721/04.
13
Kurt, Mustafa. "Time Resolved Spectroscopy Of Laser Induced Air Plasma." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608985/index.pdf.
Abstract:
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 µm) 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 (&
#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 µ
s, and the decay start 5 µ
s after the initiation of plasma. Air has 12 µ
s lifetime, and the decay start 3 µ
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.
14
Devismes, Damien. "Développement d’un système analytique pour la datation in situ des roches martiennes par la méthode K-Ar." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112254/document.
Abstract:
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 biotiteCrater 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
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Markus, Susanne. "Die Laser Induced Breakdown Spectroscopy (LIBS) als Inline-Verfahren zur Detektion von Oberflächenkontaminationen im Bereich der Klebtechnik /." Aachen : Shaker, 2008. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=017021037&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Naes, Benjamin E. "Elemental Analysis of Glass and Ink by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Laser Induced Breakdown Spectroscopy (LIBS)." FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/207.
Abstract:
The necessity of elemental analysis techniques to solve forensic problems continues to expand as the samples collected from crime scenes grow in complexity. Laser ablation ICP-MS (LA-ICP-MS) has been shown to provide a high degree of discrimination between samples that originate from different sources. In the first part of this research, two laser ablation ICP-MS systems were compared, one using a nanosecond laser and another a femtosecond laser source for the forensic analysis of glass. The results showed that femtosecond LA-ICP-MS did not provide significant improvements in terms of accuracy, precision and discrimination, however femtosecond LA-ICP-MS did provide lower detection limits. In addition, it was determined that even for femtosecond LA-ICP-MS an internal standard should be utilized to obtain accurate analytical results for glass analyses. In the second part, a method using laser induced breakdown spectroscopy (LIBS) for the forensic analysis of glass was shown to provide excellent discrimination for a glass set consisting of 41 automotive fragments. The discrimination power was compared to two of the leading elemental analysis techniques, µXRF and LA-ICP-MS, and the results were similar; all methods generated >99% discrimination and the pairs found indistinguishable were similar. An extensive data analysis approach for LIBS glass analyses was developed to minimize Type I and II errors en route to a recommendation of 10 ratios to be used for glass comparisons. Finally, a LA-ICP-MS method for the qualitative analysis and discrimination of gel ink sources was developed and tested for a set of ink samples. In the first discrimination study, qualitative analysis was used to obtain 95.6% discrimination for a blind study consisting of 45 black gel ink samples provided by the United States Secret Service. A 0.4% false exclusion (Type I) error rate and a 3.9% false inclusion (Type II) error rate was obtained for this discrimination study. In the second discrimination study, 99% discrimination power was achieved for a black gel ink pen set consisting of 24 self collected samples. The two pairs found to be indistinguishable came from the same source of origin (the same manufacturer and type of pen purchased in different locations). It was also found that gel ink from the same pen, regardless of the age, was indistinguishable as were gel ink pens (four pens) originating from the same pack.
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Lei, Wenqi. "Temporal and spatial characteristics of laser-induced plasma on organic materials and quantitative analysis of the contained inorganic elements." Phd thesis, Université Claude Bernard - Lyon I, 2012. http://tel.archives-ouvertes.fr/tel-00967250.
Abstract:
This PhD work was devoted to the understanding of the laser-induced plasma on organic materials and theapplication of laser-induced breakdown spectroscopy (LIBS) to quantitative analysis of these materials. Itcontributes to deepen our knowledge on the physical mechanisms involved in laser-matter interaction, plasmageneration, evolution and expansion of the plasma into the ambient gas, with emphasis on plasmas induced onorganic targets. It also intends to improve the performance of LIBS for the analysis of organic materials. Thespecificity for organic targets fits the current focus of the international community working on LIBS, toimprove the control of the plasma induced on this kind of material which has a distinguished optical prosperitywith respect to that of metals, better known for laser ablation. It addresses also the growing need to apply theLIBS technique to organic materials for different applications in the environmental, food, or biomedicaldomains. The works in this thesis were therefore presented in this thesis document according to the followingorganization.After the General Introduction which introduces the scientific and technological contexts, Chapter Irecalls the basic theoretical elements necessary to understand the phenomenon of plasma generation by laserablation, and its evolution in the background gas. Ablation of organic material is emphasized. Procedures andtechniques of diagnostics of laser-induced plasma were then presented with a focus on the transient andinhomogeneous nature of the expanding plasma. Chapter II focuses on the generation and the evolution of theplasma induced on the skin of a potato, a typical sample of agricultural product. The characteristics of plasmainduced on a soft and wet organic target, such as a fresh potato, was something unknown when the thesis workstarted. These characteristics provide the necessary basis for the quantitative analysis of the trace andultra-trace metallic elements in these samples. Following this characterization, semi-quantitative analyticalresults were extracted from LIBS spectra corresponding to potato skin. Chapter III is presented in thecontinuity of Chapter II for the application of LIBS to the quantitative analysis of organic materials. Acomparative study on the analytical results with LIBS and ICP-AES for milk powders allows an assessment ofthe performances of quantitative analysis by LIBS for organic materials, and a validation of the CF-LIBSprocedure that we have developed. Different from Chapters II and III where attention was paid to trace metalelements, Chapter IV studies the behavior of the major elements that make up the matrix of organic material,which are 4 known organic elements: H, C, O, N. During the decomposition of organic material by laserablation, these elements can be found in the form of molecular fragments, or recombined into molecularspecies. We then study in this Chapter the evolution of these species as a function of the laser ablationparameters, the laser wavelength in particular. The thesis document ends with a general conclusion andoutlooks.
18
Michel, Anna Pauline Miranda. "Laboratory evaluation of laser-induced breakdown spectroscopy (LIBS) as a new in situ chemical sensing technique for the deep ocean." Cambridge, Mass. : Woods Hole, Mass. : Massachusetts Institute of Technology ; Woods Hole Oceanographic Institution, 2007. http://hdl.handle.net/1912/1957.
Abstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2007.Title from Web page (viewed on Mar. 24, 2008). "September 2007." Includes bibliographical references.
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Mandrell, Christopher. "IMPROVING SPECTRAL ANALYSIS WITH THE APPLICATION OF MACHINE LEARNING: STUDY OF LASER-INDUCED BREAKDOWN SPECTROSCOPY (LIBS) AND RAMAN SPECTROSCOPY WITH CLASSIFICATION AND CLUSTERING TECHNIQUES." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2665.
Abstract:
AN ABSTRACT OF THE THESIS OFChristopher T. Mandrell, for the Master of Science degree in Physics, presented on April 8, 2020, at Southern Illinois University Carbondale.TITLE: IMPROVING SPECTRAL ANALYSIS WITH THE APPLICATION OF MACHINE LEARNING: STUDY OF LASER-INDUCED BREAKDOWN SPECTROSCOPY (LIBS) AND RAMAN SPECTROSCOPY WITH CLASSIFICATION AND CLUSTERING TECHNIQUESMAJOR PROFESSOR: Dr. Poopalasingam SivakumarAtomic and molecular spectroscopy, in the form of LIBS emissions and Raman scattering, respectively, are tools that provide a vast amount of information with little to no sample preparation. For this reason, these techniques are finding their way into a wide range of fields. However, each spectrum is notoriously complicated to analyze, with many complex interactions at play. Machine learning is the result of work on artificial intelligence. It provides tools to train a computer to look for connections in complex data sets that would likely be missed, or not even looked for, by other analytical methods. The combination of highly informative yet complex data with an analysis that is specifically designed to probe highly complex data for meaningful information is a logical step in the analysis of these spectra. Here we apply statistical analysis and classification algorithms to Raman spectra of pancreatic cancer cells and clustering algorithms to LIBS spectra of Mars Curiosity Rover simulants and Raman spectra of Mars Perseverance Rover simulants. We report here high accuracy in the classification of different types of pancreatic cancer cells, and informative clustering of the two Mars rovers’ simulant data.
20
Farah, Sougueh Ali. "Spectroscopie optique d’émission et spectroscopie laser pour le diagnostic des plasmas induits par laser." Thesis, Orléans, 2015. http://www.theses.fr/2015ORLE2066/document.
Abstract:
Les plasmas induits par laser (PIL) ont depuis leurs apparitions dans les années soixante suscité un très grand intérêt notamment comme source de données spectroscopiques. Ils ont également acquis des nombreuses applications, comme sources des rayons X pour la lithographie, l’allumage plasma, la déposition par laser pulsé, ou sont devenues la base d’une technique d’analyse très populaire – la LIBS (laser induced breakdown spectroscopy). Cette dernière peut s’appliquer in situe à tout type d’échantillon et sans préparation. Toutefois, les mesures faites par cette méthode sont latéralement intégrées nécessitant des techniques d’inversion, mais dépendent également des conditions d’équilibre thermodynamiques local (ETL) dans le plasma. Afin de valider les mesures effectuées par LIBS, la diffusion Thomson qui est une méthode spatialement résolue et indépendante des hypothèses d’équilibre thermodynamique a été appliquée pour caractériser les PIL. Des plasmas d’ablation et de claquage ont donc été caractérisés à la fois par spectroscopie d’émission et par diffusion Thomson. La comparaison des paramètres température et densité électronique obtenues par les deux méthodes d’une part, et le critère de McWhirter ainsi que les temps de relaxation et les longueurs de diffusions des espèces contenues dans le plasma d’autre part, ont permis de statuer sur l’ETLLaser induced plasma (LIP) which was first reported in the beginning of sixties, has achieved a great interest as a source of spectroscopic data. It has also many applications like X-ray sources for lithography, plasma igniters, pulsed laser deposition or it has become a basis of a very popular analytical technique – LIBS (laser induced breakdown spectroscopy). The latter is mainly due to its applicability to different kinds of samples, no sample preparation or in-situ and remote sensing capability. However, LIBS measurements are laterally integrated and Abel inversion must be performed. Also the method assumes the plasma to be in local thermodynamic equilibrium (LTE). In order to validate LIBS measurements, Thomson scattering (TS) method which is spatially resolved and free from equilibrium assumption was applied. Thus, ablation and breakdown plasmas were characterized by both two methods. Comparison between plasma parameters (temperature and electron density) obtained by the two methods and McWhirter criterion as well as relaxation times and diffusion lengths of species in the plasma allowed to estimate LTE
21
Markus, Susanne [Verfasser]. "Die Laser Induced Breakdown Spectroscopy (LIBS) als Inline-Verfahren zur Detektion von Oberflächenkontaminationen im Bereich der Klebtechnik / Susanne Markus." Aachen : Shaker, 2008. http://d-nb.info/1162790814/34.
22
Pliutau, Dzianis. "Computer simulation of stand-off LIBS and Raman LIDAR for remote sensing of distant compounds." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002208.
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Williams, Ammon N. "MEASUREMENT OF RARE EARTH AND URANIUM ELEMENTS USING LASER-INDUCED BREAKDOWN SPECTROSCOPY (LIBS) IN AN AEROSOL SYSTEM FOR NUCLEAR SAFEGUARDS APPLICATIONS." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4631.
Abstract:
The primary objective of this research is to develop an applied technology and provide an assessment for remotely measuring and analyzing the real time or near real time concentrations of used nuclear fuel (UNF) elements in electrorefiners (ER). Here, Laser-Induced Breakdown Spectroscopy (LIBS) in UNF pyroprocessing facilities was investigated. LIBS is an elemental analysis method, which is based on the emission from plasma generated by focusing a laser beam into the medium. This technology has been reported to be applicable in solids, liquids (includes molten metals), and gases for detecting elements of special nuclear materials. The advantages of applying the technology for pyroprocessing facilities are: (i) Rapid real-time elemental analysis; (ii) Direct detection of elements and impurities in the system with low limits of detection (LOD); and (iii) Little to no sample preparation is required. One important challenge to overcome is achieving reproducible spectral data over time while being able to accurately quantify fission products, rare earth elements, and actinides in the molten salt. Another important challenge is related to the accessibility of molten salt, which is heated in a heavily insulated, remotely operated furnace in a high radiation environment within an argon gas atmosphere. This dissertation aims to address these challenges and approaches in the following phases with their highlighted outcomes:
1. Aerosol-LIBS system design and aqueous testing: An aerosol-LIBS system was designed around a Collison nebulizer and tested using deionized water with Ce, Gd, and Nd concentrations from 100 ppm to 10,000 ppm. The average %RSD values between the sample repetitions were 4.4% and 3.8% for the Ce and Gd lines, respectively. The univariate calibration curve for Ce using the peak intensities of the Ce 418.660 nm line was recommended and had an R2 value, LOD, and RMSECV of 0.994, 189 ppm, and 390 ppm, respectively. The recommended Gd calibration curve was generated using the peak areas of the Gd 409.861 nm line and had an R2, LOD, and RMSECV of 0.992, 316 ppm, and 421 ppm, respectively. The partial least squares (PLS) calibration curves yielded similar results with RMSECV of 406 ppm and 417 ppm for the Ce and Gd curves, respectively.
2. High temperature aerosol-LIBS system design and CeCl3 testing: The aerosol-LIBS system was transitioned to a high temperature and used to measure Ce in molten LiCl-KCl salt within a glovebox environment. The concentration range studied was from 0.1 wt% to 5 wt% Ce. Normalization was necessary due to signal degradation over time; however, with the normalization the %RSD values averaged 5% for the mid and upper concentrations studied. The best univariate calibration curve was generated using the peak areas of the Ce 418.660 nm line. The LOD for this line was 148 ppm with the RMSECV of 647 ppm. The PLS calibration curve was made using 7 latent variables (LV) and resulting in the RMSECV of 622 ppm. The LOD value was below the expected rare earth concentration within the ER.
3. Aerosol-LIBS testing using UCl3: Samples containing UCl3 with concentrations ranging from 0.3 wt% to 5 wt% were measured. The spectral response in this range was linear. The best univariate calibration curves were generated using the peak areas of the U 367.01 nm line and had an R2 value of 0.9917. Here, the LOD was 647 ppm and the RMSECV was 2,290 ppm. The PLS model was substantially better with a RMSECV of 1,110 ppm. The LOD found here is below the expected U concentrations in the ER. The successful completion of this study has demonstrated the feasibility of using an aerosol-LIBS analytical technique to measure rare earth elements and actinides in the pyroprocessing salt.
24
Klus, Jakub. "Vývoj algoritmu pro automatickou charakterizaci vzorku na základě dat získaných spektroskopií laserem indukovaného plazmatu (LIBS)." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-364620.
Abstract:
Submitted work concerns with the theoretical and practical requirements for an automatic characterization of samples by means of Laser-Induced Breakdown Spectroscopy (LIBS). Theoretical aspects of laser-matter interaction, plasma expansion, and plasma emission are described theoretically within this work. The description of the plasma emission is enhanced with the spectral detection systems and statistical properties of the plasma. The principle of the automatic characterization is based on the multivariate data analysis theoretical background, which presents recent trend and fundamental approach for automatic spectra analysis in LIBS. Theoretical knowledge is manifested in six applications, which are presented as a comment to published manuscripts. These publications push the frontiers of automatic spectra processing in LIBS.
25
Klie, Benjamin Verfasser], Edmund [Akademischer Betreuer] Haberstroh, and Christian [Akademischer Betreuer] [Hopmann. "Bewertung der stofflichen Homogenität von Kautschukmischungen durch Einsatz der Laser Induced Breakdown Spectroscopy (LIBS) / Benjamin Klie ; Edmund Haberstroh, Christian Hopmann." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1129875997/34.
26
Michel, Anna Pauline Miranda 1976. "Laboratory evaluation of laser-induced breakdown spectroscopy (LIBS) as a new in situ chemical sensing technique for the deep ocean." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42296.
Abstract:
Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2007.Includes bibliographical references.
Present-day expeditionary oceanography is beginning to shift from a focus on short-term ship and submersible deployments to an ocean observatory mode where long-term temporally-focused studies are feasible. As a result, a critical need for in situ chemical sensors is evolving. New sensors take a significant amount of time to develop; thus, the evaluation of techniques in the laboratory for use in the ocean environment is becoming increasingly important. Laser-induced breakdown spectroscopy (LIBS) possesses many of the characteristics required for such in situ chemical sensing, and is a promising technique for field measurements in extreme environments. Although many LIBS researchers have focused their work on liquid jets or surfaces, little attention has been paid to bulk liquid analysis, and especially to the effect of oceanic pressures on LIBS signals. In this work, laboratory experiments validate the LIBS technique in a simulated deep ocean environment to pressures up to 2.76 x 10⁷ Pa. A key focus of this work is the validation that select elements important for understanding hydrothermal vent fluid chemistry (Na, Ca, Mn, Mg, K, and Li) are detectable using LIBS. A data processing scheme that accurately deals with the extreme nature of laser-induced plasma formation was developed that allows for statistically accurate comparisons of spectra. The use of both single and double pulse LIBS for high pressure bulk aqueous solutions is explored and the system parameters needed for the detection of the key analytes are optimized. Using both single and double pulse LIBS, the limits of detection were found to be higher than expected as a result of the spectrometer used in this experimentation. However, the results of this validation show that LIBS possesses the characteristics to be a viable chemical sensing method for in situ analyte detection in high pressure environments like the deep ocean.
by Anna Pauline Miranda Michel.
Ph.D.
27
Lucas, Natasha S. "The application of Laser Induced Breakdown Spectroscopy (LIBS) to the analysis of geological samples in simulated extra-terrestrial atmospheric environments." Thesis, University of Salford, 2007. http://usir.salford.ac.uk/22723/.
Abstract:
Laser induced breakdown spectroscopy (LIBS) is a technique that can determine the elemental composition and quantities of a sample by the spectral analysis of a laser induced plume. This study was undertaken to develop, characterise and assess the use of the LIBS technique on geological samples in different pressure and gaseous environments. The experimental range chosen was dictated by the planetary conditions on Titan and other extra-terrestrial bodies with the samples analysed chosen to complement a range of rock types. A LIBS system was developed, together with associated experimental apparatus able to acquire results in varying pressure and gaseous environments. The capability of LIBS to analyse weathered rock samples was investigated under various ambient conditions; pressures of 160x103 Pa to 0.4x10-3 Pa and ambient gaseous mixtures of air, nitrogen and methane. Particular attention was paid to temporal and power considerations under such regimes. As was expected, the chosen delay time to optimise the emission signals needed to be increased with increasing ambient pressure. At power values as low as 28.5 mJ/pulse (using a 6 ns pulse from a doubled Nd:YAG laser at 532 nm) a valid emission signal could be obtained. Increasing the laser power resulted in a reduction in the overall signal to noise ratio. It was observed that ambient methane quenches the optical emission signal due to non-radiative transitions. In spite of this, valid qualitative data are obtainable, even when emissions due to carbon transitions from both the sample and the gaseous environment, are present. Results are presented which support the premise that the LIBS technique can be used to investigate both the surface and depth compositions of geological samples under extra-terrestrial conditions.
28
El, Rakwe Maria. "Approches multivariées innovantes pour le traitement des spectres d'émission de plasmas produits par laser. Application à l'analyse chimique en ligne par LIBS en milieu nucléaire." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066316/document.
Abstract:
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 LIBSOnline 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
29
Cahoon, Erica M. "The Discrimination and Association of Float Glass and The Quantitative Analysis of Liquids from Aerosols and Microdrops using Laser Induced Breakdown Spectroscopy." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/621.
Abstract:
Glass is a common form of trace evidence found at many scenes of crimes in the form of small fragments. These glass fragments can transfer to surrounding objects and/or persons and may provide forensic investigators valuable information to link a suspect to the scene of a crime. Since the elemental composition of different glass sources can be very similar, a highly discriminating technique is required to distinguish between fragments that have originated from different sources.
The research presented here demonstrates that Laser Induced Breakdown Spectroscopy (LIBS) is a viable analytical technique for the association and discrimination of glass fragments. The first part of this research describes the optimization of the LIBS experiments including the use of different laser wavelengths to investigate laser-material interaction. The use of a 266 nm excitation laser provided the best analytical figures of merit with minimal damage to the sample. The resulting analytical figures of merit are presented. The second part of this research evaluated the sensitivity of LIBS to associate or discriminate float glass samples originating from the same manufacturing plants and produced at approximately the same time period. Two different sample sets were analyzed ranging in manufacturing dates from days to years apart. Eighteen (18) atomic emission lines corresponding to the elements Sr, K, Fe, Ca, Al, Ba, Na, Mg and Ti, were chosen because of their detection above the method detection limits and for presenting differences between the samples. Ten elemental ratios producing the most discrimination were selected for each set. When all the ratios are combined in a comparison, 99% of the possible pairs were discriminated using the optimized LIBS method generating typical analytical precisions of ~5% RSD.
The final study consisted of the development of a new approach for the use of LIBS as a quantitative analysis of ultra-low volume solution analysis using aerosols and microdrops. Laser induced breakdown spectroscopy demonstrated to be an effective technique for the analysis of as low as 90 pL for microdrop LIBS with 1 pg absolute LOD and 20 µL for aerosol LIBS with an absolute LOD of ~100 fg.
30
Jantzi, Sarah C. "Elemental Analysis and Forensic Comparison of Soils by Laser-Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS)." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/967.
Abstract:
The elemental analysis of soil is useful in forensic and environmental sciences. Methods were developed and optimized for two laser-based multi-element analysis techniques: laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and laser-induced breakdown spectroscopy (LIBS). This work represents the first use of a 266 nm laser for forensic soil analysis by LIBS.
Sample preparation methods were developed and optimized for a variety of sample types, including pellets for large bulk soil specimens (470 mg) and sediment-laden filters (47 mg), and tape-mounting for small transfer evidence specimens (10 mg). Analytical performance for sediment filter pellets and tape-mounted soils was similar to that achieved with bulk pellets.
An inter-laboratory comparison exercise was designed to evaluate the performance of the LA-ICP-MS and LIBS methods, as well as for micro X-ray fluorescence (μXRF), across multiple laboratories. Limits of detection (LODs) were 0.01-23 ppm for LA-ICP-MS, 0.25-574 ppm for LIBS, 16-4400 ppm for µXRF, and well below the levels normally seen in soils. Good intra-laboratory precision (≤ 6 % relative standard deviation (RSD) for LA-ICP-MS; ≤ 8 % for µXRF; ≤ 17 % for LIBS) and inter-laboratory precision (≤ 19 % for LA-ICP-MS; ≤ 25 % for µXRF) were achieved for most elements, which is encouraging for a first inter-laboratory exercise. While LIBS generally has higher LODs and RSDs than LA-ICP-MS, both were capable of generating good quality multi-element data sufficient for discrimination purposes.
Multivariate methods using principal components analysis (PCA) and linear discriminant analysis (LDA) were developed for discriminations of soils from different sources. Specimens from different sites that were indistinguishable by color alone were discriminated by elemental analysis. Correct classification rates of 94.5 % or better were achieved in a simulated forensic discrimination of three similar sites for both LIBS and LA-ICP-MS. Results for tape-mounted specimens were nearly identical to those achieved with pellets.
Methods were tested on soils from USA, Canada and Tanzania. Within-site heterogeneity was site-specific. Elemental differences were greatest for specimens separated by large distances, even within the same lithology. Elemental profiles can be used to discriminate soils from different locations and narrow down locations even when mineralogy is similar.
31
Kadenkin, Alexander. "High throughput LIBS analysis." Doctoral thesis, Humboldt-Universität zu Berlin, 2017. http://dx.doi.org/10.18452/18654.
Abstract:
Ziel dieser Arbeit war die Untersuchung der Eignung der laserinduzierten Plasmaspektroskopie (LIBS) bei der Online-Analyse der Materialströme in einer Sortieranlage zwecks Identifizierung der Legierungen am Beispiel der Aluminiumknetlegierungen. Als Ansatz sollten hierbei neuartige Laserquellen wie Faserlaser oder diodengepumpte Festkörperlaser verwendet werden, die mit deutlich höheren Repetitionsraten als häufig verwendete blitzlampengepumpte Festkörperlaser betrieben werden können.
Im Rahmen dieser Arbeit wurde eine systematische Untersuchung der laserinduzierten Plasmaspektroskopie mit diodengepumpten Festkörperlasern als Anregungsquelle durchgeführt. Hierbei konnte festgestellt werden, dass die LIBS mit solchen Anregungsquellen ein gutes Nachweisvermögen und eine gute Stabilität besitzt. Ferner wurde ein Prototyp für die Online-Analyse der Aluminiumlegierungen entwickelt und mit einem kommerziell erhältlichen System verglichen. Es konnte festgestellt werden, dass das Nachweisvermögen des Prototyps für einige Fragestellungen bei der Sortierung von Aluminiumlegierungen ausreichend ist. Bei dem kommerziell erhältlichen System konnten dagegen selbst bei einer Fördergeschwindigkeit von 3 m/s Nachweisgrenzen erreicht werden, die für sämtlichen aktuellen analytische Fragestellungen auf diesem Gebiet ausreichend sind.
Anschließend wurden die analytischen Güteziffern des kommerziell erhältlichen Systems verbessert, indem verschiedene multivariate Analysemethoden und Datenvorverarbeitungstechniken untersucht und optimiert wurden. Im nächsten Schritt wurde das System mit den optimierten Analysemethoden für die Sortierung der realen Produktionsschrotte eingesetzt. Hierbei konnte gezeigt werden, dass die Sortierung von Aluminiumlegierungen in verschiedene Gruppen der Aluminiumknetlegierungen bei einer Fördergeschwindigkeit von 3 m /s mittels LIBS möglich ist.
Im letzten Schritt wurden die Möglichkeiten der Übertragung der Methoden von einem Gerät auf ein anderes untersucht. Hierbei konnte ein Algorithmus ermittelt werden, bei dem ein derartiger Transfer möglich ist. Somit kann dieser bei einer Serienproduktion der Systeme eingesetzt werden, um den experimentellen Aufwand bei der Kalibrierung drastisch zu reduzieren.The aim of this study was the investigation of the suitability of laser-induced breakdown spectroscopy (LIBS) for online analysis of material flow in a sorting plant for identification of alloys on example of aluminum wrought alloys. As a new approach in this study, new laser sources such as fiber lasers or diode-pumped solid state lasers, which can be operated with significantly higher repetition rates as broadly used flash lamp pumped lasers, were used. In this work, a systematic study of laser-induced breakdown spectroscopy with diode-pumped solid-state laser as an excitation source has been studied. It was found that LIBS with such excitation sources has good detection capability and good stability. In addition, a prototype for the online analysis of the aluminum alloys was developed and compared with a commercially available system. It could be determined that the detection capability of the prototype was sufficient for some analytical tasks in sorting of aluminum alloys. The limits of detection of the commercially available system were even at conveyor belt speed of 3 m/s sufficient for all current analytical tasks in this field. Subsequently, the analytical figures of merit of the commercially available system were improved by the study and optimization of the different multivariate analysis techniques and data pretreatment algorithms. In the next step, the system with the optimized analytical methods was used for sorting the real production scrap. It could be demonstrated that the sorting of aluminum alloys in different groups of aluminum wrought alloys at a conveyor speed of 3 m /s is possible by the use of LIBS. In the last step, the possibilities of transfer of the methods from one device to the other one were investigated. Here, an algorithm has been found, which makes such transfer possible. Therefore, this can be used for the reduction of the experimental effort during calibration drastically in a series production of the systems.
32
Carvalho, Alexandrina Aparecida Costa. "Estudo de parâmetros na medição de Cr em amostras ambientais por LIBS." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-15092016-081523/.
Abstract:
Nos últimos anos, a Espectrometria de Emissão Atômica com Plasma induzido por Laser (LIBS) vem despertando grande interesse e pesquisas voltadas às aplicações analíticas dessa técnica tem aumentado significativamente. No entanto, sua aplicação na análise de amostras líquidas não é trivial, podendo haver comprometimento na sensibilidade e na precisão do método. Além disso, a análise quantitativa é considerada o \"calcanhar de Aquiles\" da técnica, especialmente devido à falta de materiais de referência certificados e à forte interferência de matriz. Nesse contexto, com a intenção de viabilizar a análise de matrizes líquidas por LIBS, esse trabalho propõe o uso de cerâmica como fase sólida para extração, pré-concentração e especiação de Cr em amostras de água. Foi realizado também um estudo de otimização dos parâmetros instrumentais do LIBS para o desenvolvimento de um método de medição de Cr na fase sólida, empregando cerâmica enriquecida com concentrações crescentes desse analito como material calibrante sintético. Os resultados obtidos mostraram que a cerâmica adsorve seletivamente a espécie Cr(III) em pH 7, sendo este um processo rápido, de baixo custo, cuja eficiência é pouco afetada pela presença de outros eletrólitos. Os estudos relacionados à otimização dos parâmetros instrumentais do LIBS indicaram que um diâmetro de focalização de 65 µm, um tempo de atraso de 0,75 µs, a energia por pulso de 20 mJ, uma taxa de repetição de 10 Hz e um número de pulsos igual a 403 podem ser recomendados para a quantificação de Cr no material cerâmico. Nessas condições, obteve-se uma curva de calibração analítica que possibilitou a medição Cr adsorvido em cerâmica. Uma amostra de água de torneira foi então enriquecida com 0,9 mg L-1 de Cr(III) e 0,9 mg L-1 de Cr(VI) para que um teste de recuperação fosse realizado com a finalidade de se verificar a aplicabilidade do método proposto, foi possível constatar a adsorção seletiva da espécie Cr(III), com recuperação de 105±2%. A quantificação da espécie Cr(VI) por LIBS também é possível após a redução dessa espécie a Cr(III) utilizando Fe(II) como agente redutor. Os limites de detecção (LOD) e quantificação (LOQ) estimados para o método foram respectivamente 21 mg kg-1 e 70 mg kg-1, equivalentes a 0,1 mg L-1 e 0,35 mg L-1, considerando-se o coeficiente de pré-concentração igual a 200 (m/m).In recent years, Laser Induced Breakdown Spectroscopy (LIBS) has deserved attention of scientific community and researches using this technique have increased significantly. However, its application in the analysis of liquid samples is not trivial, because the sensitivity and accuracy of the method can be affected. In addition the quantitative analysis is considered the \"Achilles\' heel\" of the technique, especially due to the lack of certified reference materials and to the strong interference matrix. To enable the analysis of liquid matrices by LIBS, this work proposes the use of ceramic as solid phase in the extraction, preconcentration and speciation of Cr in water samples. LIBS instrumental parameters were also optimized to allow the measurement of Cr in this solid phase, for the development of a method for measuring the analyte in the solid phase, which was also used as synthetic calibrating material by the addition of increasing concentrations of the analyte. Results showed the ceramic selectively adsorbs Cr(III) species at pH 7, which is a low cost and rapid process, whose efficiency is not significantly affected by the presence of other electrolytes. Studies related to the optimization of LIBS instrumental parameters indicated that spot size of 65 µm, delay time of 0,75 µs , energy per pulse of 20 mJ, repetition rate of 10 Hz and a number of pulses equal to 403 can be recommended for the quantification of Cr the ceramic material. Under these conditions, it was obtained an analytical calibration curve which allowed a Cr measurement in ceramics. A tap water sample was enriched with 0.9 mg L-1 of Cr(III) and 0.9 mg L-1 of Cr (VI) and a recovery test was done in order to verify the applicability of the proposed method. It was observed the selective adsorption of the Cr(III) species, with recovery of 105 ± 2 %. The quantification of Cr(VI) species by LIBS was also possible, after reduction of this species to Cr(III) using Fe(II) as reducing agent. The limit of detection (LOD) and the limit of quantification (LOQ) obtained by the proposed method were respectively, 21 mg kg-1 and 70 mg kg-1, equivalent to 0.1 mg L-1 and 0.35 mg L-1, considering the preconcentration coefficient of 200 (on a w/w basis).
33
Ohnesorge, Alexander. "Bestimmung des Aufmischungsgrades beim Laser-Pulver-Auftragschweißen mittels laserinduzierter Plasmaspektroskopie (LIPS)." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1233310151669-10595.
Abstract:
Ziel der vorliegenden Arbeit ist die Untersuchung der Methode der Laserinduzierten Plasmaspektroskopie (LIPS) zur Bestimmung des Aufmischungsgrades ([Eta]) in durch Laserstrahl-Präzisionsauftragschweißen (LAP) hergestellten Beschichtungen. Grund- und Zusatzwerkstoff müssen sich hierbei in ihrer Elementzusammensetzung voneinander unterscheiden. Als Substratmaterial diente unlegierter Baustahl, als Zusatzwerkstoff wurde Stellit 21 eingesetzt. [Eta] stellt eine wichtige Qualitätskenngröße dar und kann nach vorheriger Kalibrierung des LIPS-Messsystems sowohl offline als auch online detektiert werden. Der Aufmischungsgrad korreliert mit dem detektierten Emissionslinienverhältnis. Im untersuchten Fall besteht in guter Näherung ein linearer Zusammenhang zwischen beiden Größen. Die Vorteile von LIPS gegenüber anderen Verfahren liegen insbesondere in der berührungslosen Analyse und der entfallenden Probenpräparation. Prinzipiell lässt sich das Vorgehen auf andere Werkstoffsysteme übertragen. Das verwendete LISP-Messsystem kann in den Fertigungsprozess integriert werden und steht als Technologiemodul für eine qualifizierte Überwachung des Aufmischungsgrades beim LAP-Prozess zur Verfügung.
34
Belica, Martin. "Vývoj univerzálního softwarového rozhraní pro detekční jednotky v optické spektroskopii." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2020. http://www.nusl.cz/ntk/nusl-413006.
Abstract:
This master's thesis deals with the design and implementation of universal user interface for detection devices used in Laser-induced breakdown spectroscopy. The design and implementation are based on analysis of current state of instrumentation used in laser spectroscopy. The user interface should be able to work with high repetition frequency of measurement. Acquired spectra should be visualised to user and it is also necessary to save this data on hard drive. The resulting application must be universal. It means the application must support various types and vendors of detection devices.
35
Švábíková, Anna. "Návrh optomechanického modulu pro chemické mapování metodou spektroskopie laserem buzeného plazmatu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-402524.
Abstract:
Tato diplomová práce se zabývá návrhem optomechanického modulu pro chemické mapování metodou spektroskopie laserem buzeného plazmatu (LIBS). Cílem je vyvinout modul, který bude umožňovat analýzu spektrálních čar zinku v ultrafialové (UV) oblasti. V práci jsou popsány teoretické základy metody LIBS a následně je provedena rešerše zaměřená na problematiku dálkové LIBS analýzy. V diplomové práci jsou prezentovány možné optické návrhy fokusační a sběrné optiky, z nichž jsou vybrané následně otestovány. Výsledkem práce je konstrukční návrh modulu.
36
Leone, Nicolas. "Développement d'une technique d'analyse hautement sensible et polyvalente par spectroscopie de plasma induit par laser : applications aux aérosols et aux matériaux biologiques." Phd thesis, Paris 6, 2007. http://pastel.archives-ouvertes.fr/pastel-00004873.
Abstract:
La spectroscopie de plasma (10e4 K et 10e16 électron.cm-3) induit par laser pulsé ns (LIBS) est développée pour caractériser tout échantillon chimique ou biologique (gaz, surface homogène ou hétérogène, aérosol), de façon in situ, rapide (~10e-6 s), sensible et reproductible, à des fins de classification, voire d'identification. Le volume échantillonné optiquement est reproductible pour les plasmas dans les gaz (~1 mm3) et sur surfaces (diamètre d'impact~10e2 µm2). Cela permet d'étalonner la technique pour le dosage multiélémentaire à des seuils de l'ordre du ppm, voire du ppb, y compris pour des particules microniques. Les marqueurs spectraux des matériaux biologiques (Ca, Mg, Na, K, P et C) sont identifiés par traitement statistique selon une analyse en composantes principales permettant de classer les échantillons par nature. On vérifie comment les observables discriminantes sont détectés pour diverses formes bactériennes : pastilles compressées de bactéries lyophilisées, cultures végétatives sur boîtes de Pétri à un seuil minimal déterminé d'environ 10e3 bactéries, et aérosols suspendus. L'exploitation statistique des identifiants permet de distinguer les bactéries par rapport à des milieux nutritifs et des leurres. Dans le cas de l'analyse au vol de bactéries aérosolisées, la détection est plus complexe et aléatoire du fait des faibles teneurs élémentaires disponibles, ce qui nécessite leur concentration préalable. La LIBS, calibrée pour les gaz, surfaces et aérosols, est alors transposée en outil transportable, polyvalent et sensible ouvrant de vastes champs applicatifs : diagnostics biomédicaux, suivi en ligne de procédés industriels, contrôle qualité environnementale...
37
Gregoire, Sylvain. "Etude et optimisation de la méthode LIBS (Laser Induced Breakdown Spectroscopy) pour l'identification de matériaux organiques appliquée au recyclage des plastiques et à la conservation du patrimoine." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01062281.
Abstract:
La LIBS est une technique d'analyse élémentaire dont la rapidité d'exécution et la portabilité en font une technique idéale pour l'analyse des matériaux sur site. Elle a déjà largement fait ses preuves dans le cadre de l'analyse de matériaux inorganiques. Mais les molécules organiques usuelles présentent des compositions atomiques similaires (C, O, H, N), rendant leur identification en LIBS difficile. L'utilisation de traitements de données tels que les rapports de raies ou la chimiométrie est donc inéluctable pour séparer efficacement plusieurs types de molécules organiques en LIBS. Malgré le caractère élémentaire de cette technique, les spectres obtenus lors de l'analyse de matériaux organiques montrent la signature spectrale de molécules diatomiques C2 et CN. Longtemps considéré comme des recombinaisons aléatoires des atomes présents dans le plasma, le signal de ces molécules s'avère d'dépendant de la nature des liaisons moléculaires de la molécule d'origine. Ce travail de thèse s'oriente autour de trois grands axes d'études - L'utilisation de traitements de données tels que la chimiométrie pour établir un protocole de traitements optimal visant à la discrimination des polymères dans le cadre du tri des plastiques. Un protocole optimisé a pu être avancé en UV et en IR. - L'identification des matières organiques utilisées en peinture murale (liants, adhésifs et consolidants) a pu être réalisée sur des échantillons de peinture de référence. Les traitements de données utilisés précédemment ont pu être appliqués sur ces échantillons présentant une matrice majoritairement inorganique. - La compréhension des procédés de formation des molécules diatomiques dans le plasma pour améliorer leur utilisation et ainsi optimiser la discrimination des matériaux organiques sur la base du signal moléculaire en LIBS. Le développement d'un système d'imagerie a permis de suivre le comportement spatio-temporel des espèces atomiques et moléculaires dans le plasma sous régimes UV et IR. Une hypothèse de formation des molécules sous ablation UV et IR a pu être établie.
38
Kunati, Sandeep Reddy. "Trace Measurements of Tellurium, Tin and Other Metals by Atomic and Laser Spectroscopy Techniques." Connect to resource online, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1219695278.
39
Ohnesorge, Alexander. "Bestimmung des Aufmischungsgrades beim Laser-Pulver-Auftragschweißen mittels laserinduzierter Plasmaspektroskopie (LIPS)." Doctoral thesis, Technische Universität Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A23904.
Abstract:
Ziel der vorliegenden Arbeit ist die Untersuchung der Methode der Laserinduzierten Plasmaspektroskopie (LIPS) zur Bestimmung des Aufmischungsgrades ([Eta]) in durch Laserstrahl-Präzisionsauftragschweißen (LAP) hergestellten Beschichtungen. Grund- und Zusatzwerkstoff müssen sich hierbei in ihrer Elementzusammensetzung voneinander unterscheiden. Als Substratmaterial diente unlegierter Baustahl, als Zusatzwerkstoff wurde Stellit 21 eingesetzt. [Eta] stellt eine wichtige Qualitätskenngröße dar und kann nach vorheriger Kalibrierung des LIPS-Messsystems sowohl offline als auch online detektiert werden. Der Aufmischungsgrad korreliert mit dem detektierten Emissionslinienverhältnis. Im untersuchten Fall besteht in guter Näherung ein linearer Zusammenhang zwischen beiden Größen. Die Vorteile von LIPS gegenüber anderen Verfahren liegen insbesondere in der berührungslosen Analyse und der entfallenden Probenpräparation. Prinzipiell lässt sich das Vorgehen auf andere Werkstoffsysteme übertragen. Das verwendete LISP-Messsystem kann in den Fertigungsprozess integriert werden und steht als Technologiemodul für eine qualifizierte Überwachung des Aufmischungsgrades beim LAP-Prozess zur Verfügung.
40
Bruder, Romain. "Etude et développement de la spectroscopie d'émission optique sur plasma induit par laser pour l'analyse de terrain : un exemple d'application aux œuvres d'art." Paris 6, 2008. http://www.theses.fr/2008PA066123.
Abstract:
La LIBS est une technique d’analyse élémentaire encore peu utilisée pour l'analyse de terrain du patrimoine culturel. Trois grandes problématiques ont été le sujet de cette thèse, afin de mieux maîtriser son utilisation dans ce domaine :Passage du laboratoire vers le terrain : la faisabilité de l’identification de pigments sur un chantier de restauration a été illustrée. La complémentarité LIBS-spectroscopie Raman a été démontrée pour l’identification de pigments et les études stratigraphiques. Impact visuel de l’analyse LIBS sur l’œuvre : les dimensions du cratère d'ablation sont contrôlées par la mise en forme et la focalisation du faisceau laser. Les décolorations périphériques observées sont dues à des dépôts oxydés. Des seuils de perception ont été établis en fonction de l’énergie délivrée, ce qui donne la possibilité d'éviter ces décolorations. Effets de matrice : la normalisation de droites d'étalonnage de Cu dans diverses matrices métalliques par la quantité de matière ablatée, la température et la densité électronique du plasma ne corrige pas complètement les variations entre matériaux. Pour les expliquer, la proportion d'atomes ablatés présents sous forme de vapeur atomique dans le plasma est déterminée. Ce paramètre dépend de la nature et de la concentration de l'élément, ainsi que de la matrice considérée, ce qui implique que l'émission du plasma ne semble pas représentative de la composition du matériau et qu'une quantification fiable ne peut être menée qu'à l'aide d'étalons.
41
Schiffer, Štěpán. "Způsoby korekce a standardizace signálu v laserové spektroskopii." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-392852.
Abstract:
The subject of this diploma thesis is the study of a sample position influence on results of an experiment in laser spectroscopy. The aim is to design an appropriate way for standardization of signal obtained at different conditions with the respect to its applicability for stand-off analysis. In the theoretical part of the diploma thesis there are the basics of LIBS method described together with the issues of stand-off experiment and both, basic and advanced approches for the processing and correction of obtained spectra. Also the experiment is designed here, which is used for the analysis of the sample inclination and distance influence on the detected signal. The choice of appropriate ways for the signal correction follows and their applicability and efficiency is then experimentally tested.
42
Šrenk, David. "Vizualizace spektroskopických dat pomocí metody analýzy hlavních komponent." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-401532.
Abstract:
This diploma thesis deals with using laser-induced breakdown plasma spectroscopy for determining the elemental structure of unknown samples. It was necessary to design an appropriate method to qualify material by laser-induced emission spectrum. Pretreatment of data and using a variety of chemometrics methods had to be done in order to qualify the structure of elements. We achieved a required solution by projecting the data to a new PCA space, creating clusters and computing the Euclidean distance between each cluster. The experiment in the practical part was set to detect an interface of two elements. We created a data file simulating the ablation on the interface. This data set was gradually processed applying a mathematical-chemical-physical view. Several data procedures have been compiled: approximation by Lorenz, Gauss and Voigt function and also a pretreatment method such as the detection of outliers, standardization by several procedures and subsequent use of principal components analysis. A summarization of processes for input data is fully described in the thesis.
43
Koch, Sandra [Verfasser], Rainer [Akademischer Betreuer] Reuter, Walter [Akademischer Betreuer] Neu, and Gottfried H. [Akademischer Betreuer] Bauer. "Qualitative and quantitative trace analysis on liquids and solid samples by laser-induced breakdown spectroscopy (LIBS) / Sandra Koch. Betreuer: Rainer Reuter ; Walter Neu ; Gottfried H. Bauer." Oldenburg : BIS der Universität Oldenburg, 2012. http://d-nb.info/104865138X/34.
44
Acevedo, Turbi Pahola Annette. "Single biοmass pellet degradatiοn during cοmbustiοn : influence οf raw elemental cοmpοsitiοn determined by LΙBS." Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMIR01.
Abstract:
La demande mondiale croissante d’énergie et les préoccupations environnementales croissantes ont propulsé l’exploration d’alternatives durables aux sources de carburant conventionnelles. La biomasse se présente comme une ressource renouvelable prometteuse, capable d'atténuer la crise énergétique mondiale tout en garantissant la durabilité environnementale. Cette étude se penche sur le comportement de combustion de trois biomasses distinctes : le bois d'origine forestière, le miscanthus herbacé et la paille d'orge résiduelle agricole. En examinant le comportement des particules individuelles pendant la combustion, la recherche cherche à élucider les processus fondamentaux régissant la conversion de la biomasse en énergie et à comprendre les comportements de combustion uniques des différentes sources de biomasse. La complexité de la combustion de la biomasse, influencée par des facteurs tels que la composition chimique, la teneur en éléments et les étapes de combustion, est au cœur de l'enquête. Les premiers résultats mettent en évidence les effets catalytiques potentiels d’éléments mineurs comme le sodium (Na) et le potassium (K) sur le comportement de combustion, ce qui nécessite des études approfondies pour comprendre pleinement leur influence. Grâce à une caractérisation complète, l'étude identifie trois étapes critiques de combustion des particules de biomasse : la perte d'humidité, la dévolatilisation et l'oxydation du charbon, révélant des distinctions significatives dans les points d'inflammation entre les sources de biomasse étudiées. La thèse vise à contribuer de manière significative à la compréhension de la production d'énergie basée sur la biomasse et de ses implications environnementales, en fournissant une base pour les progrès futurs dans l'utilisation de la biomasse, la production d'énergie et les pratiques durablesThe escalating global demand for energy and mounting environmental concerns have propelled the exploration of sustainable alternatives to conventional fuel sources. Biomass stands out as a promising renewable resource capable of alleviating the worldwide energy crisis while addressing environmental sustainability. This study delves into the combustion behavior of three distinct biomass: forest-derived wood, herbaceous miscanthus, and agricultural residue barley straw. By scrutinizing individual particle behavior during combustion, the research seeks to unravel the fundamental processes governing biomass conversion into energy and understand the unique combustion behaviors of different biomass sources. The complexity of biomass combustion, influenced by factors like chemical composition, elemental content, and combustion stages, lies at the heart of the investigation. Initial findings highlight potential catalytic effects of minor elements like sodium (Na) and potassium (K) on combustion behavior, prompting the need for in-depth studies to fully comprehend their influence. Through comprehensive characterization, the study identifies three critical combustion stages for biomass particles: humidity loss, devolatilization, and char oxidation, revealing significant distinctions in ignition points among the investigated biomass sources. The thesis aims to significantly contribute to understanding biomass-based energy generation and its environmental implications, providing a foundation for future advancements in biomass utilization, energy production, and sustainable practices
45
Diaz, Rosado José Carlos. "Étude et développement de la spectroscopie d'émission optique sur plasma induit par laser pour la réalisation d'analyses de terrain : application à l’analyse en ligne de métaux dans les liquides." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA114805/document.
Abstract:
La contamination par métaux des eaux est un enjeu de santé publique important. Des contrôles et traitements de plus en plus drastiques sont ainsi effectués sur les eux destinés à la consommation humaine. Il est indispensable, pour cela, de posséder des outils analytiques fiables et sensibles, adaptés aux réglementations existantes et suffisamment souples d'utilisation. La technique de « Laser Induced Breakdown Spectroscopy » (LIBS), ayant fait ses preuves pour l’analyse des solides, y compris dans les explorations exo-terrestres, présente des avantages très intéressants pour les liquides dont, par exemple, sont caractère multi-élémentaire et la possibilité des mesures in-situ de la contamination des eaux par métaux.Un première volet d’étude de ce travail de thèse à permis d'étudier les potentialités de la spectroscopie sur plasma induit par laser (LIBS) pour l'analyse des métaux dissous ou en suspensions dans les eaux. Etude qu’a permis de constater un effet important lié à la taille des particules lors de l’analyse de suspensions. Un deuxième volet consisté à regarder les effets de matrice organique représentée par un acide humique et ceux des minéraux naturels représentés par la bentonite et des particules d’alumine. Effets matrice qu’ont étais corriges par une normalisation par étalon interneMetal contamination of water is a major public health issue. Controls and treatments are more drastic and performed on them for human consumption. It is essential for this to possess reliable and sensitive analytical tools adapted to the existing regulations and flexible enough to use. The technique of "Laser Induced Breakdown Spectroscopy" (LIBS), proven for the analysis of solids, including exo-terrestrial explorations, this very interesting advantages for liquids including, for example, are multi-character elementary and the possibility of in-situ measurements of water contamination by metals.A first part of this study thesis allowed to explore the potential (LIBS) for the analysis of dissolved metals or suspensions in water. Study has found an important effect related to the particle size in the analysis of suspensions. A second prong is to look at the effects of organic matrix represented by humic acid and those natural minerals represented by the bentonite and alumina particles. The matrix effect observed was corrected by normalization by internal standard
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Chide, Baptiste. "Le premier microphone sur Mars : contribution à la spectroscopie de plasma induit par laser et à la science atmosphérique." Thesis, Toulouse, ISAE, 2020. http://www.theses.fr/2020ESAE0041.
Abstract:
Le 18 février 2021, l'astromobile de la NASA Perseverance se posera dans le cratère Jezero à la recherche de traces de vie passée. A son bord l'expérience franco-américaine SuperCam ne contient pas moins de quatre techniques spectroscopiques, une caméra haute résolution et un microphone. Ce microphone sera le premier à enregistrer des ondes acoustiques audibles à la surface de Mars entre 100 Hz et10 kHz. Il ouvrira un nouveau champ d'investigation qui fait l'objet de cette thèse. Les objectifs scientifiques de cette thèse s'organisent autour des sons qui seront audibles par ce microphone : les phénomènes atmosphériques dans l'environnement proche du véhicule et les bruits artificiels générés par SuperCam lui-même. Parmi ces derniers, la technique de la spectroscopie de plasma induit par laser (LIBS) ablate les roches et les sols martiens avec un laser impulsionnel, ce qui produit un signal acoustique lors de la détente de ce plasma. Ce manuscrit propose une étude amont qui vise à caractériser le support du microphone à la LIBS et sa contribution à la science atmosphérique. Ces deux thèmes sont explorés expérimentalement en reproduisant en laboratoire les conditions d'écoute que le microphone rencontrera sur Mars.Premièrement, un banc de mesure LIBS sous atmosphère martienne est utilisé pour comparer le signal acoustique issu de l'ablation de différents minéraux. Une étude métrologique a déterminé la sensibilité de l'énergie acoustique par rapport aux paramètres expérimentaux de la LIBS : elle est proportionnelle à la pression atmosphérique et à l'éclairement déposé sur la cible. Ces relations permettront de normaliser le signal acoustique entre toutes les cibles échantillonnées par la LIBS sur Mars. De plus il est remarqué que la décroissance de l'énergie acoustique au cours d'une séquence de tirs est linéairement reliée au volume de la cavité d'ablation et que le taux de décroissance est corrélé à la dureté de la roche. Volume d'ablation et dureté seront deux informations utilisées pour caractériser les cibles de SuperCam et en particulier étudier celles présentant des vernis d'altération en surface.D'autre part, une campagne de tests dans une soufflerie martienne est effectuée pour corréler les propriétés d'un écoulement de vent avec le signal acoustique induit par ce dernier sur le microphone. Il est démontré que le microphone peut déterminer la vitesse de l'écoulement en étudiant le contenu basse fréquence du spectre, mais aussi sa direction en regardant le contenu haute fréquence. Ces résultats nécessiteront une calibration in situ sur Mars avec la station météo de Perseverance, MEDA. Il est également montré que la synchronisation du microphone avec le laser permet une mesure originale de la vitesse du son et donc de la température atmosphérique proche de la surface.Enfin, cette validation des objectifs scientifiques du microphone s'accompagne d'un soutien au développement instrumental du microphone, avec la validation de ses performances, la définition des modes d'observation et la préparation des opérations de SuperCam à la surface de MarsIn February 2021 the Mars 2020 Perseverance rover will land in Jezero to search for traces of past life.Part of the Perseverance payload, the SuperCam instrument suite includes four spectroscopy techniques,a high resolution imager and a microphone. This microphone will be the first microphone to record audible acoustic waves on the surface on Mars between 100 Hz to 10 kHz. It will open a new field of investigation which is the subject of this thesis. The scientific objectives of this thesis are organized around the sounds that will be recorded by this microphone : atmospheric phenomena in the close vicinity of the rover and artificial noises generated by SuperCam itself. Among the latest, the laser-induced breakdown spectroscopy technique (LIBS) ablates Martian rocks and soils with a pulsed laser. It creates an acoustic signal due tothe expansion of this plasma. These two topics are experimentally explored thanks to the development of laboratory test benches that simulate the conditions likely to be encountered by the microphone on Mars.On the one hand a LIBS setup under Mars atmosphere is used to compare acoustic signal from several minerals. A metrological study of the sensitivity of the acoustic signal with respect to LIBS experimental parameters is conducted : the acoustic energy is proportional to the CO2 background pressure and to the irradiance deposited on the sample. These two relationships will help to normalize the acoustic signal from multiple LIBS targets on Mars. Moreover, it is noticed that the decrease of the acoustic energy along a LIBS burst is linearly linked to the ablated volume. The decrease rate is correlated to the rock hardness.It provides new information relative to the ablation process that is independent from the LIBS emission spectrum. It could be used to better characterize geologic targets and rock, in particular the ones with asurface coating or a weathering rind.On the other hand, a test campaign in a Martian wind tunnel is dedicated to link wind properties withwind-induced signal recorded by the microphone. It is demonstrated that the microphone can determinethe flow velocity by studying the low frequency range of the acoustic spectrum whereas the wind directioncan be retrieved by looking at the high frequency range. An in situ cross-calibration with the weather station on board Perseverance, MEDA, will be required to validate these results. It is also shown that the synchronization of the microphone with the LIBS laser can be used to measure the speed of sound and therefore to estimate the atmospheric temperature close to the surface of Mars.This work also describes some progresses in the microphone development including the performances' validation, the implementation of operating modes and the preparation of SuperCam operations at the surface of Mars
47
Franco, Marco Aurélio de Menezes. "Efeitos de matriz nas propriedades do plasma LIBS para quantificação de carbono." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-13092017-135929/.
Abstract:
Nos últimos 20 anos, a espectroscopia de emissão ótica com plasma induzido a laser (LIBS) tem se tornado uma das mais promissoras ferramentas em química analítica, cujas aplicações são destinadas às análises multi-elementares em amostras nos estados sólido, líquido e gasoso. Suas aplicações são as mais diversas, pois sua instrumentação é relativamente simples e pode ser portátil. Em especial, a LIBS apresenta grande potencial de uso na agricultura, com diversas publicações que exploram, principalmente, a concentração de carbono em solos. Entretanto, a construção de modelos gerais de calibração é uma das maiores dificuldades da técnica, pois ela está suscetível aos efeitos de matriz que adicionam comportamentos não-lineares às intensidades das emissões. Com intuito de compreender quais são as principais causas dessa dependência, este trabalho avaliou relações entre propriedades físicas do plasma LIBS e as inclinações das curvas de calibração para cinco emissões de carbono em amostras sintéticas de diferentes potenciais de ionização, sendo elas KCl e H3BO3 com 1% de CuSO4 e concentrações entre 0 e 10 % de carbono. Constatou-se que temperatura e densidade de elétrons dependem inversamente da concentração de carbono nas amostras, o que provavelmente está associado às taxas de ablação de material da amostra e recombinação no interior do plasma. Ademais, esses parâmetros em plasmas originados das amostras de KCl + CuSO4 são maiores do que para a matriz de H3BO3 + CuSO4, além de que apenas plasmas originados da primeira matriz satisfizeram o critério de McWhirter para C I, Cu I e Cu II em todas as concentrações de carbono, indicando que eles devem apresentar condições de equilíbrio termodiâmico local. O mesmo não foi obtido para o caso da matriz de H3BO3 + CuSO4, o que pode explicar suas elevadas incertezas nos valores da temperatura e densidade de elétrons. Verificou-se ainda que as inclinações das curvas de calibração para o carbono foram maiores para o caso da matriz com elementos majoritários de menor potencial de ionização e que isso está diretamente relacionado às propriedades intrínsecas dos plasmas originados, o que corrobora a hipótese deste trabalho. Além disso, cálculos de correlação entre a área do pico de carbono em 247,89 nm e cada ponto dos espectros LIBS mostraram que a emissão de Cu II em 224,72 nm linearizou as curvas de calibração, minimizando os efeitos de matriz. Por fim, este trabalho contribuiu tanto com avanços no conhecimento até então existente a respeito dos efeitos de matriz quanto com um eficiente conjunto de técnicas analíticas para espectros, cujo potencial de aplicação é enorme.In the last 20 years, laser-induced breakdown spectroscopy (LIBS) has been one of the main tools in analytical chemistry, whose applications are destinated to multi-elementar analysis in solid, liquid or gaseous samples. Its use is diverse, since its instrumentation is relatively simple and can be portable. In particular, LIBS has a great potential for use in agriculture, with many publications that explore mainly the carbon concentration in soils. However, the construction of general calibration models is one of the greatest difficulties of the technique, since it is susceptible to matrix effects that add non-linear behaviors to the emission intensities. In order to understand the main causes of this dependence, this study evaluated the relationships between physical properties of the LIBS plasma and the slope of the calibration curves for carbon emissions in synthetic samples with different ionization potentials. Those samples were made of KCl and H3BO3 with 1% of CuSO4 and carbon concentrations ranging from 0 to 10%. It was found that the plasma temperature and electron density are inversely proportional to the carbon concentration in the samples, which is probably associated with rates of sample ablation and recombination within the plasma. In addition, these parameters in plasmas originating from the samples of KCl + CuSO4 are larger than those originating from the matrix of H3BO3 + CuSO4 at all carbon concentrations, indicating that the first matrix must be in local thermodynamics equilibrium. However, similar results were not found for the other matrix which may explain its high uncertainties in the values of temperature and electron density. It was verified that the slope of the carbon calibration curves were higher for the matrix with elements of low ionization potential than for the other matrix and that this is directly related to the intrinsic properties the plasmas originated, which corroborates the hypothesis of this study. Furthermore, the analysis of correlation between the carbon peak area at 247.89 nm and each point of the LIBS spectra have shown that the Cu II emission at 224.72 nm linearized the calibration curves, minimizing the matrix effects. Finally, this study contributed with advances in the knowledge about matrix effects and with an efficient set of analytical tools for spectra whose application potential is huge.
48
Képeš, Erik. "Klasifikace kovů pomocí spektroskopie laserem buzeného plazmatu a chemometrických metod." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318788.
Abstract:
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.
49
Tian, Ye. "Characterization of laser-induced plasma and application to surface-assisted LIBS for powder and liquid samples." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1292/document.
Abstract:
La spectroscopie de plasma induit par laser (En anglais LIBS: laser-induced breakdown spectroscopy) est une méthode analytique de spectroscopie d'émission optique qui utilise un plasma induit par laser comme source de vaporisation, d'atomisation et d'excitation. Bien que la LIBS ait démontré sa polyvalence et ses caractéristiques attrayantes dans de nombreux domaines, les aspects quantitatifs de la LIBS sont considérés comme son talon d'Achille. D'un point de vue fondamental, cela peut être dû à la nature complexe du plasma induit par laser comme source d'émission spectroscopique. La caractérisation temporelle et spatiale du plasma induit par laser est considérée comme l'un des points clés pour comprendre les fondements de la technique LIBS. D'autre part, la LIBS est habituellement caractérisée par l'utilisation d'une ablation laser directe, sans traitement préalable de l'échantillon. Cela pourrait être assez limitant en particulier pour certains types de matériaux tels que des poudres ou des liquides. Une préparation adéquate ou un traitement approprié de l'échantillon permettant le dépôt d'un film mince et homogène de l'échantillon sur une surface métallique pourrait grandement augmenter le potentiel de la LIBS en vue d'obtenir de meilleures performances analytiques, et notamment une meilleure sensibilité et un effet de matrice réduit. On parle alors de LIBS assistée par surface car la matrice métallique contribue à une augmentation de la température du plasma. Le présent travail de thèse est donc motivé par deux aspects importants de la technique LIBS: la connaissance du plasma induit par laser comme source d'émission spectroscopique, et de nouvelles méthodes de préparation des échantillons pour améliorer la performance analytique de la LIBS, notamment pour des échantillons comme poudres et liquides visqueux. La première partie de cette thèse (chapitre 2) est consacrée à la caractérisation du plasma induit sur des échantillons de verre, en fonction de la longueur d'onde du laser, infrarouge (IR) ou ultraviolet (UV), et du gaz ambiant, de l'air ou de l'argon. L'imagerie spectroscopique et la spectroscopie d'émission résolue en temps et en espace sont utilisées pour le diagnostic du plasma. La deuxième partie de cette thèse est de développer des méthodes de préparation d'échantillons, déposés sur des surfaces métalliques pour l'analyse LIBS de poudres ainsi que de vins comme exemples de liquide. Au chapitre 3, nous avons appliqué la LIBS pour l'analyse quantitative dans des poudres (exemples de poudres : cellulose, alumine ainsi que de la terre). Au chapitre 4, nous avons appliqué la LIBS pour la classification des vins français selon leurs régions de production. Deux modèles de classification basées sur l'analyse des composants principaux (PCA) et la forêt aléatoire (RF) sont utilisés pour la classification. A l'aide de ces applications, ce travail de thèse démontre l'efficacité de la méthode LIBS assistée par surface pour l'analyse de poudres (cellulose, alumine et sols) et de liquides (vins), avec une limite de détection dans l'ordre de ou sous la ppm et une réduction significative de l'effet de matriceLaser-induced breakdown spectroscopy (LIBS) is an analytical method with optical emission spectroscopy that uses a laser pulse to vaporize, atomize, and excite a hot plasma as the spectroscopic emission source. Although LIBS has demonstrated its versatility and attractive features in many fields, the quantitative analysis ability of LIBS is considered as its Achilles’ heel. From a fundamental point of view, this can be due to the complex nature of laserinduced plasma as the spectroscopic emission source for LIBS application. The temporal and spatial characterization of laser-induced plasma is considered as one of the key points for the LIBS technique. On the other hand, from the analytical point of view, LIBS is usually characterized by direct laser ablation. This can be however quite limiting, especially for some types of materials such as powders or liquids. Proper sample preparation or treatment allowing the deposition of a thin homogeneous film on a metallic surface could greatly improve the analytical performance of LIBS for these types of materials. Since the metallic surface is expected to contribute to increase the temperature and the density of the plasma and, consequently, to a better overall sensitivity, we call this technique surface-assisted LIBS. The present thesis work is therefore motivated by two basic aspects of LIBS analysis: the need of an improved knowledge of laser-induced plasma as a spectroscopic emission source, and new methods to improve the analytical performance of LIBS, including a higher sensibility and a reduced matrix effect. The first part of this thesis (Chapter 2) is dedicated to an extensive characterization of the plasma induced on glass samples, as a function of the laser wavelength, infrared (IR) or ultraviolet (UV), and the ambient gas, air or argon. Both the spectroscopic imaging and time- and space-resolved emission spectroscopy are used for plasma diagnostics in this work. The second part of this thesis is to develop a surface-assisted LIBS method for the elemental analysis in powders, and in wines as examples of liquids. We applied the surface-assisted LIBS for the quantitative elemental analysis in cellulose powders, alumina powders, and soils (Chapter 3). Special attentions are paid on the figures-of-merit, matrix effects, and normalization approaches in LIBS analysis. We also used the surfaceassisted LIBS for the classification of French wines according to their production regions (Chapter 4). Two classification models based on the principal component analysis (PCA) and random forest (RF) are used for the classification. Through these applications, this thesis work demonstrates the efficiency of the surface-assisted LIBS method for the analysis of powders (cellulose, alumina and soils) and of liquids (wines), with ppm or sub-ppm sensitivities and a reduced matrix effect
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El, Haddad Josette. "Chimiométrie appliquée à la spectroscopie de plasma induit par laser (LIBS) et à la spectroscopie terahertz." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00959288.
Abstract:
L'objectif de cette thèse était d'appliquer des méthodes d'analyse multivariées au traitement des données provenant de la spectroscopie de plasma induit par laser (LIBS) et de la spectroscopie térahertz (THz) dans le but d'accroître les performances analytiques de ces techniques.Les spectres LIBS provenaient de campagnes de mesures directes sur différents sites géologiques. Une approche univariée n'a pas été envisageable à cause d'importants effets de matrices et c'est pour cela qu'on a analysé les données provenant des spectres LIBS par réseaux de neurones artificiels (ANN). Cela a permis de quantifier plusieurs éléments mineurs et majeurs dans les échantillons de sol avec un écart relatif de prédiction inférieur à 20% par rapport aux valeurs de référence, jugé acceptable pour des analyses sur site. Dans certains cas, il a cependant été nécessaire de prendre en compte plusieurs modèles ANN, d'une part pour classer les échantillons de sol en fonction d'un seuil de concentration et de la nature de leur matrice, et d'autre part pour prédire la concentration d'un analyte. Cette approche globale a été démontrée avec succès dans le cas particulier de l'analyse du plomb pour un échantillon de sol inconnu. Enfin, le développement d'un outil de traitement par ANN a fait l'objet d'un transfert industriel.Dans un second temps, nous avons traité des spectres d'absorbance terahertz. Ce spectres provenaient de mesures d'absorbance sur des mélanges ternaires de Fructose-Lactose-acide citrique liés par du polyéthylène et préparés sous forme de pastilles. Une analyse semi-quantitative a été réalisée avec succès par analyse en composantes principales (ACP). Puis les méthodes quantitatives de régression par moindres carrés partiels (PLS) et de réseaux de neurons artificiels (ANN) ont permis de prédire les concentrations de chaque constituant de l'échantillon avec une valeur d'erreur quadratique moyenne inférieure à 0.95 %. Pour chaque méthode de traitement, le choix des données d'entrée et la validation de la méthode ont été discutés en détail.