Дисертації з теми "CO₂ laser"
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1
Al-Mashaabi, Fahad Saleh. "DC-excited cw CO₂ metal waveguide laser." PDXScholar, 1988. https://pdxscholar.library.pdx.edu/open_access_etds/3756.
Повний текст джерелаАнотація:
A novel design for a DC excited cw C02 metal waveguide laser has been developed in which a slotted hollow-cathode in a transverse discharge also doubles as a metal waveguide. This design has been implemented in a compact design that produces up to 1 watt of cw, 10.6 μm radiation. The discharge characteristics, laser gain and laser output has been studied as functions of various discharge parameters. The advantages of the new transverse discharge of the slotted hollow cathode geometry include low voltage, positive impedence and high optical gain. Overall efficiency is comparable with those of conventional longitudinal CO2 lasers. The output laser modes were very clean low order Gaussian modes.
2
Cassard, Philippe. "Verrouillage par injection des lasers impulsionnels de grande puissance : le laser TEA CO₂." Paris 11, 1985. http://www.theses.fr/1985PA112338.
Повний текст джерелаАнотація:
Cette thèse concerne l’étude du verrouillage par injection dans les lasers impulsionnels de grande puissance. Une analyse théorique du verrouillage de mode dans les lasers impulsionnels est présentée. Une théorie multimode est développée sur la base du traitement semi-classique du laser à champ faible. Le verrouillage par injection continue fait l’objet d’une étude approfondie. Il est clairement démontré que le verrouillage par injection d’un champ faible dans un laser impulsionnel multimode est un verrouillage de mode(s) quelle que soit la durée du champ d’injection. Le traitement présenté décrit tout aussi bien la génération d’impulsions brèves par injection. Une revue des propriétés énergétiques de l’oscillateur-laser TEA CO₂ est présentée, que ce soit en présence ou en l’absence d’injection. Une étude expérimentale fine de l’injection continue est appliquée au cas du laser TEA CO₂ muni d’un résonateur stable. Des mesures de fréquence ont été réalisées suivant un schéma original d’hétérodynage à haute fréquence. Les limites du verrouillage par injection sont étudiées. De plus, le rôle important de la densité électronique de la décharge TEA sur le verrouillage par injection est démontré. Une seconde étude expérimentale met en évidence le verrouillage par injection des modes d’ordre supérieur d’un résonateur instable dans un laser TEA CO₂ de très grande puissanceThis thesis is directed at the study of injection-locking of high power pulsed lasers. Chapter I give a theoretical analysis of injection mode-locking in such lasers. A multimode theory is developed on the basis of the semi-classical treatment in the weak field regime. A detailed investigation of CW injection-locking is reported. It is clearly demonstrated that locking by injection of a weak field in a pulsed multimode laser stems from injection mode-locking whatever is the injection field time history. Thus the generation of short pulses by injection is described as well. Chapter II theoretically overviews the energetic features of the TEA CO₂ laser, with or without injection. Chapter III presents an experimental investigation of CW injection-locking in stable resonator TEA CO₂ lasers. Frequency measurements are performed with a new high frequency heterodyning scheme. The limits of CW injection locking are studied. Moreover, the influence of the transient discharge electron density on injection-locking is demonstrated. Chapter IV gives an experimental evidence of high order transverse mode injection-locking in unstable resonator TEA CO₂ lasers
3
Kästle, Ralf. "CO-laser photoacoustic spectroscopy of fatty acid molecules /." [S.l.] : [s.n.], 1995. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=11154.
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4
Schroeder, Brett Robert. "Laser induced epitaxy of Ni and Co silicides." Master's thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/16013.
Повний текст джерелаАнотація:
Includes bibliographical references.Laser annealing of metal layers on silicon substrates failed to produce uniform silicide layers. This can be attributed to constitutional supercooling effects. Laser annealing of thermally grown monosilicides gave low (~5%) minimum yields for Co and Ni on <111> substrates1 as well as Ni on <100> substrates. The best yield achieved for Co on <100> substrates is 35%. The formation of a non-equilibrium epitaxial monosilicide was also achieved. Numerical calculations based on a heat flow approach gave fair quantitative agreement with experiment.
5
Hennequin, Daniel. "Chaos dans un laser CO à modulation interne." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376058583.
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6
Thompson, Alexander W. J. "Multimode absorption spectroscopy of CO and CO₂ gas mixtures." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:ebcb2031-1165-414e-88d8-69465bdaf291.
Повний текст джерелаАнотація:
The development of multimode absorption spectroscopy (MUMAS) for multi-species detec- tion and its potential for process control or environmental monitoring is reported. The simultaneous detection of CO and CO2 is demonstrated in a proof-of-principle experiment for applications in industrially relevant gas species monitoring. The technique of MUMAS is extended to the near infrared in order to detect these and other industrially relevant species. A laser was designed and constructed to emit a multimode spectrum in the region of 1.57um to take advantage of the spectral overlap of the second vibrational overtone of CO and the combination band 3ν1 + ν3 of CO2. The laser consisted of a semi-confocal cavity employing an Er:Yb glass chip as the gain medium. The laser was pumped by a 1W laser diode at 980nm and emitted up to 30mW in a bandwidth of 180GHz. The laser emitted between 6-10 modes depending upon the selective cavity length. Mode spacings varied between 18GHz to 33GHz with an individual mode linewidth of less than 8MHz. The laser modes were simultaneously scanned using a piezo-electric transducer (PZT) in order to modulate the cavity length at frequencies between 1Hz and 10Hz. A system for linearizing the MUMAS spectra with respect to frequency was devised based on a transmission spectra of a confocal Fabry-Perot etalon. Refinements to the MUMAS fitting code were developed to improve the computational efficiency. An initial demonstration of MUMAS on a known gas mixture of CO and CO2 was per- formed. The ratio of CO:CO2 concentrations in the gas mixture was measured with an accuracy of 0.4% which was within the supplier’s quoted uncertainty. MUMAS is then applied to the detection of CO and CO2 concentrations in exhaust gas produced by a 1.3 litre 4-cylinder turbo-charged spark ignition engine. Relative and absolute concentrations were derived from MUMAS signals and values compared to measurements using a 4-gas analyser. Concentrations of CO and CO2 were measured using MUMAS to a precision of 0.17% and 0.23% respectively compared to less than 0.1% for the 4-gas analyser. Ratios of CO and CO2 were determined with a precision of 0.28 using MUMAS compared to 0.11 with the 4-gas analyser. The detection limit of CO was found to be 1486ppm in these circumstances. Finally a discussion is presented of potential improvements arising from wavelength mod- ulation spectroscopy and cavity enhancement techniques.
7
Mullins, Stephanie Lauren MacNeill Simon R. "Morphologic and microbiological effects of a third generation CO₂ laser on the treatment of periodontal pockets a pilot study /." Diss., UMK access, 2006.
Знайти повний текст джерелаАнотація:
Thesis (M.S.)--School of Dentistry. University of Missouri--Kansas City, 2006."A thesis in oral biology." Advisor: Simon R. MacNeill. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Nov. 12, 2007. Includes bibliographical references (leaves 56-60). Online version of the print edition.
8
Yurkovich, Matt. "Electrically Excited, Supersonic Flow CO Laser Operated with Air Species in the Laser Mixture." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480577301983725.
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9
Zhu, Yueqiang. "Measurement of harmonics in a underdense CO₂ laser produced plasma." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26679.
Повний текст джерелаАнотація:
Second harmonic(2ω₀) and three halves harmonic(3/2ω₀) are studied in the interaction of CO₂ laser of frequency ω₀, with an underdense plasma. It is shown theoretically that filamentation can lead to sizable second harmonic generation. The 2ω₀-radiation is emitted into a forward directed cone, its angle determined by the wavelength of the fundamental radiation in the plasma filament. Experimental observations confirm the theoretical predications. Aside from the forward directed emission cone, non negligable 2ω₀ power is detected over a broad angular range in the backward direction showing a broadened red shifted spectrum. The dependence of the backward emitted 2ω₀-radiation on the plasma density, and the red shifted spectrum strongly support the argument that the backward emitted 2ω₀-radiation is related to the SBS(Stimulated Brillouin scattering) instability. Based on the wave vector matching conditions, the angular distribution of 3/2ω₀-radiation is predicted. The experimental results confirm the prediction. It is shown experimentally that the fusion of three plasma waves produced in the TPD(Two Plasma Decay) instability dominates the generation of 3/2ω₀-radiation when the incident beam energy is high.Science, Faculty of
Physics and Astronomy, Department of
Graduate
10
Cottam, Christopher Andrew. "TEA CO₂-laser treatment of coated and corroded metals." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/27042.
Повний текст джерелаАнотація:
A selection of corroded, painted and lacquered metals have been subjected to high-powered, pulsed TEA C02-laser radiation to investigate self-limiting cleaning and treatment processes. Changes in the surface chemistry were observed and recorded using a variety of surface analysis techniques including X-ray Powder Diffraction, Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy. Changes in surface appearance were recorded using colour macro-photography and Scanning Electron Microscopy. The effects of both plasma and sub-plasma laser fluences were investigated.
11
Greses-Juan, Jose. "Plasma/plume effects in CO₂ and Nd:YAG laser welding." Thesis, University of Cambridge, 2003. https://www.repository.cam.ac.uk/handle/1810/284019.
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12
Pruneau, Godmaire Xavier. "Micro-usinage de fibres optiques avec un laser CO₂." Master's thesis, Université Laval, 2011. http://hdl.handle.net/20.500.11794/23028.
Повний текст джерелаАнотація:
Le mandat initial de ce projet de maîtrise visait l'élaboration de procédures de microusinage de fibres optiques à l'aide d'un laser C0₂ puisé. L'efficacité d'usinage d'une fibre optique a d'abord été mise en évidence via l'étude théorique des phénomènes engendrés par l'absorption du rayonnement infrarouge. Suite à une caractérisation spatiale et temporelle du système laser, des méthodes sans contact de dégainage, de clivage et de polissage ont été mises sur pied en exploitant les propriétés uniques du rayonnement à 10,6/xm. Des fibres optiques de silice, de ZBLAN et de verre de chalcogénure ont toutes trois été soumises à ces procédures de micro-usinage. En définitive, l'étude de l'interaction entre un laser CO₂ et des réseaux de Bragg a permis de mettre en lumière quelques applications intéressantes.
13
Chiang, Shichan. "Plume attenuation effects in CO₂ laser welding of steel /." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487687115924614.
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14
Haddad, Ali. "Mise en oeuvre et modulation d'un laser à CO." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb375980945.
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15
Schwaller, Christoph Andreas. "Rezidivhäufigkeit von Condylomata acuminata nach Behandlung mit CO₂-Laser /." [S.l : s.n.], 1993. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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16
Thöny, Andreas. "New developments in CO₂-laser photoacoustic monitoring of trace gases /." Zürich, 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10345.
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17
Meyer, Peter. "Air-pollution monitoring with a mobile CO₂-laser photoacoustic system /." Zürich, 1988. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=8651.
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18
Davis, Donald D. Jr. "Long-period fiber gratings fabricated with focused CO₂ laser pulses." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15764.
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19
Von, Klitzing Wolf Dietrich Carl. "Ultra-high resolution CO₂ laser spectroscopy and transient line narrowing." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627129.
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20
Butorac, J. "Femtosecond laser studies of CO and NO on Pd(111)." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1335711/.
Повний текст джерелаАнотація:
The ultimate goal of any branch of chemistry, including surface chemistry, is to understand the dynamics of reactions. The typical time scale for bond making and breaking is the femtosecond time scale. Femtochemistry has led to enormous progress in the understanding, and even control, of chemical reactions in the gas and solution phases over the past decades. However, a comparable level of sophistication in the analysis of surface chemical reactions has not been achieved due to the complexity of the energy dissipation channels. For this thesis, a new experimental set-up was built with the goal to monitor the femtosecond laser-induced desorption (fs-LID) and femtosecond laser-induced reaction (fs-LIR) of CO and NO co-adsorbed on a Pd(111) surface. In addition, a femtosecond extreme ultraviolet (XUV) source was designed and commissioned. All the femtosecond laser-induced studies were accompanied by temperature programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS). First, fs-LID experiments were performed for pure CO and NO adsorbed on Pd(111) in order to test the apparatus. The CO and NO photodesorption dynamics were compared and the different photoreactivity was explained qualitatively using two theoretical models: electron friction and desorption induced by multiple electronic transitions (DIMET). The power law behaviour was also tested and a new method of fitting proposed. The photodesorption behaviour of CO co-adsorbed with NO on Pd(111) was then studied and compared qualitatively with the photodesorption behaviour of pure CO and NO within the empirical friction model.
21
Haddad, Ali. "Mise en oeuvre et modulation d'un laser a co : :(2)." Caen, 1986. http://www.theses.fr/1986CAEN2013.
Повний текст джерелаАнотація:
L'effet stark moleculaire sur nh::(2)d est utilise pour moduler la raie p 20 (10,6mu m) d'un laser a co::(2). Comme application de cet effet, une liaison video, avec cette raie comme porteuse, a ete realisee. Le laser utilise, de type scelle, a ete concu et realise au laboratoire. Une partie de ce travail, a consiste a asservir la longueur de la cavite pour optimiser la puissance emise. D'autres experiences ont ete entreprises: modulation "intra-cavite", bistabilite electrooptique
22
Valko, N., S. Anufric, A. Ivanov, and S. Vasiliev. "Laser Modification of the Microstructure of Zn-Co Electroplating Alloys." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42658.
Повний текст джерелаАнотація:
In this study we report the experimental results of researches of the effect on the microstructure of the Zn-Co coatings with laser radiation generated by a ruby laser operating of free oscillators regime (1.2 ms pulse duration, wavelength 0.69𝜇𝑚 and the power density of 104 to 106 W / cm2). It is shown how the microstructure of the investigating alloys after its modification by an impulse laser radiation depends on the
power density.
23
DUBOUCHET, CATHERINE. "Traitements thermomecaniques de surfaces metalliques a l'aide de lasers co#2 continus et de laser impulsionnel." Paris 11, 1993. http://www.theses.fr/1993PA112360.
Повний текст джерелаАнотація:
Une nouvelle technique de renforcement, le traitement thermomecanique, est etudiee ici. Celui-ci consiste en la superposition de deux traitements, l'un thermique, l'autre mecanique. Le traitement thermique est une operation de trempe superficielle de l'acier 55c1 realisee a l'aide d'un laser co#2 continu. Le traitement mecanique est lui, realise a l'aide d'un laser nd-verre impulsionnel et n'induit que des transformations mecaniques dans le materiau. La superposition de ces operations confere a l'acier etudie une durete elevee en surface et un champ de contrainte de compression s'etendant sur une profondeur importante. Dans le cas de la trempe, les caracterisations (thermiques, metallurgiques et mecaniques) realisees experimentalement sont comparees aux resultats de simulations numeriques. Ceci permet, entre autres, de valider les mesures de temperatures effectuees en temps reel. Les experiences realisees a l'aide du laser impulsionnel montrent que l'effet d'un choc laser sur l'acier est purement mecanique. L'influence des parametres de traitements sur le resultat induit dans le materiau est determinee experimentalement et comparee aux resultats d'un modele analytique existant. Enfin, la superposition des deux traitements met en evidence que grace a un choc mecanique, il est possible de transformer un champ de contrainte initial (du a l'operation de trempe). La replastification engendree par l'onde de choc peut meme entrainer la mise en compression d'un champ de contrainte de traction. Les effets induits par traitement thermomecanique dans un acier sont, parallelement aux experiences, analyses a l'aide d'un modele analytique developpe au cours de ce travail
24
Wazen, Paul. "Laser NH moyen-infrarouge continu pompe optiquement par lase CO laser et amplificateur de puissance de type Raman, laser à inversion de population accordable en fréquence par effet stark /." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376106932.
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25
Bousquet, Philippe. "Étude d'une maquette de laser CO₂ à décharge transverse haute pression adaptée à des expériences spectroscopiques." Paris 11, 1988. http://www.theses.fr/1988PA112344.
Повний текст джерелаАнотація:
Le but de ce travail est de concevoir, améliorer et fiabiliser un laser CO2 adapté aux études spectroscopiques en laboratoire. Ce laser pulsé, à décharge transverse haute pression (10 atm), utilise un mélange gazeux CO₂ – N₂ - He : 1 – 1 – 8 et à une émission accordable en fréquence autour de 9,6 μm, 10,2 μm et 10,6 μm. La décharge est préconisée par UV et une cadence de tir maximale de 4Hz a été obtenue. L’insertion dans la cavité d’un étalon (Fabry-Pérot) a permis de sélectionner un seul mode d’oscillation. Les principales difficultés rencontrées proviennent de la tenue des éléments optiques, plus particulièrement des hublots, utilisés dans la cavité. Différents matériaux sont testés : ZnSe, NaCI ou KCI traités antireflets ou encore ZnSe, sous incidence de Brewster. Enfin, le laser est utilisé dans des expériences de spectroscopie. En focalisant le laser sur un cristal de chalcopyrite (Cd Ge As₂), la fréquence du laser est doublée. Ce laser accordable autour de 5 μm, a permis d’exciter une bande d’absorption du CO piégé en matrice d’argon ou d’azote et de mesurer la durée de vie du niveau excité de CO par fluorescence induite.
26
Kälin, Armin Walter. "Development and optimization of OFID-10 {mü}m CO₂ laser systems /." Zürich, 1991. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=9584.
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27
Steinmann, C. M. (Christine Margarete). "Vacuum ultraviolet laser spectroscopy of CO molecules in a supersonic jet." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53709.
Повний текст джерелаАнотація:
Thesis (PhD)--Stellenbosch University, 2003.ENGLISH ABSTRACT: A tunable narrow-bandwidth laser source combined with a supersonic gas jet as sample is wellsuited for obtaining high-resolution spectra of cold isolated molecules and complexes. In the present study such a laser source in the vacuum ultraviolet was applied to the spectroscopic investigation of rare carbon monoxide (CO) isotopomers and CO-noble gas van der Waals complexes in supersonic gas pulses seeded with natural CO gas. Tunable coherent vacuum ultraviolet radiation was generated by two-photon resonant fourwave sum-frequency mixing of two pulsed dye laser beams in a magnesium vapour medium. Laser induced fluorescence excitation spectra of the A(v'=3)-X(v"=0) vibronic band of CO molecules in a noble gas (neon or argon) jet were obtained by measuring the total undispersed fluorescence from the irradiated sample volume in dependence of the excitation wavelength. The dynamics of the flow-cooling process in the supersonic jet were investigated and the experimental parameters optimised using the rotational temperature of 12C160as determined from rotational line intensities. Rotational temperatures as low as 2 ± I K were observed. Spectroscopic detection of the rare 12C170and 12C180isotopomers was facilitated by the low rotational temperature and high spectral resolution. Six rotational lines of 12C170and four of 12C180were detected in the A(v'=3)-X(v"=0) vibronic band. This demonstrates the low detection limit (circa 3 parts per million) obtained in the experiment. The line wavelengths were determined to an accuracy of 0.2 pm using the well-documented 12C160and 13C160lines for calibration. The spectral results on 12C170are, to our knowledge, the first rotationally resolved laboratory measurements published on the A-X band of this isotopomer. Accurate wavelength data of the stable isotopomers of CO is of importance in the interpretation of astrophysical observations of CO in the interstellar medium. The newly determined 12C170wavelengths were successfully applied to a recent problem in astrophysics (Astrophys. J. Lett. 2003). The conditions in a supersonic jet facilitate the study of weakly bound van der Waals complexes, of which CO-noble gas complexes are prototypes. However, there is no experimental data available on the electronic excitation spectra of the CO-noble gas complexes, lying in the vacuum ultraviolet region. In the present experiment evidence of extensive complexation of the CO in the noble gas jet has been found, but in the spectral region around the A(v'=3)-X(v"=O) band of CO no distinct spectral features that could be associated with these complexes were observed. Having considered the existing knowledge on CO and CO-noble gas complexes and experimental studies on the excitation and dissociation dynamics of Iz-noble gas complexes, we regard complex induced inter-system crossing or electronic predissociation as the most likely causes for these observations. The results on the rare CO isotopomers demonstrate the potential of our experimental setup for high-resolution, isotope and state selective spectroscopy in the vacuum ultraviolet with a high sensitivity for fluorescent species. The availability of the now well-characterised experimental setup in our laboratory opens the way for further investigation of molecular or complex species with spectroscopic features in the vacuum ultraviolet region.
AFRIKAANSE OPSOMMING: Vakuum ultraviolet laser spektroskopie van CO molekules in 'n supersoniese gasstraal: 'n Afstembare smal bandwydte laserbron en 'n supersoniese gasstraal as monster is 'n geskikte kombinasie vir hoë-resolusie spektroskopie van geïsoleerde afgekoelde molekules en komplekse. In hierdie studie is so 'n laserbron in die vakuum ultraviolet gebruik in die spektroskopiese ondersoek van skaars koolstofmonoksied (CO) isotopomere en CO-edelgas van der Waals komplekse in supersoniese gaspulse wat 'n klein persentasie natuurlike CO gas bevat. Afstembare koherente vakuum ultraviolet lig is verkry deur twee-foton resonante vier-golf som-frekwensie vermenging van twee gepulseerde kleurstoflaserbundels in 'n magnesiumdamp medium. Laser-geïnduseerde fluoressensie opwekkingspektra van die A(v'=3)-X(v"=0) vibroniese band van die CO molekules in die edelgasstraal (neon of argon) is uitgemeet deur die totale fluoressensie van die beligte gasmonster, sonder golflengteskeiding, te meet as funksie van die opwekkingsgolflengte. Die dinamika van die vloeiverkoelingsproses in die supersoniese gasstraal is ondersoek en die eksperimentele parameters geoptimeer deur gebruik te maak van die rotasionele temperatuur van 12Cl60 soos bepaal uit die intensiteitsverhoudings van die rotasielyne. Rotasionele temperature tot so laag as 2 ± 1 K is waargeneem. Spektroskopiese waarneming van die skaars 12C170 and 12Cl80 isotopomere is moontlik gemaak deur die lae rotasionele temperatuur en die hoë spektrale resolusie. Ses rotasielyne van 12C170 en vier van 12C180 is waargeneem in die A(v'=3)-X(v"=0) vibroniese band. Dit demonstreer die lae deteksielimiet (ongeveer 3 dele per miljoen) wat bereik kon word. Die golflengtes van die lyne is bepaal met 'n akkuraatheid van 0.2 pm deur die bekende lyne van 12C160en 13C160vir kalibrasie te gebruik. Die resultate ten opsigte van 12C170 is sover vasgestel kon word die eerste rotasioneel-opgeloste laboratorium metings van die A-X band van hierdie isotopomeer. Akkurate golflengte data vir die stabiele CO isotopomere is van belang vir die interpretasie van die astrofisiese waarnemings van CO in die interstellêre medium. Die nuwe 12C170 golflengtes is suksesvol aangewend in die oplossing van 'n onlangse interpretasieprobleem in astrofisika (Astrophys. J. Lett. 2003). Die toestande in 'n supersoniese gasstraal maak die bestudering van swak-gebonde van der Waals komplekse moontlik. Hoewel CO-edelgas van der Waals komplekse as prototipes beskou word, is daar geen eksperimentele data beskikbaar oor die elektroniese opwekkingspektra van hierdie spesies, wat in die vakuum ultraviolet gebied lê, nie. In hierdie studie is daar eksperimentele getuienis gevind vir uitgebreide kompleksering van CO in die edelgasstraal, maar in die spektraalgebied rondom die A(v'=3)-X(v"=O) band van CO is geen duidelike spektrale kenmerke wat met hierdie komplekse geassosieer kan word, waargeneem nie. Na oorweging van die bestaande kennins oor CO en CO-edelgas komplekse en eksperimentele studies oor die opwekking en dissosiasie-dinamika van Iz-edelgas komplekse, beskou ons kompleksgeïnduseerde intersisteemoorgange of elektroniese predissosiasie as die waarskynlikste redes vir hierdie waarnemings. Die resultate oor die skaars CO isotopomere toon die potensiaal van ons eksperimentele opstelling vir hoë-resolusie, isotoop- en toestandselektiewe spektroskopie in die vakuum ultraviolet met uitstekende sensitiwiteit vir fluoresserende spesies. Die beskikbaarheid van hierdie nou deeglik gekarakteriseerde eksperimentele opstelling in ons laboratorium maak verdere ondersoek na molekulêre of kompleks-spesies met spektroskopiese kenmerke in die vakuum ultraviolet moontlik.
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Gautier, Pierre. "Dosage des polluants NO et CO par imagerie de fluorescence induite par laser dans les écoulements réactifs." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMIR26/document.
Повний текст джерелаАнотація:
La thèse consiste à développer une technique d'imagerie quantitative de concentration de polluants dans les écoulements réactifs. Il s'agit d'une part de développer l'imagerie de fluorescence sur NO. Un modèle de fluorescence à n niveaux a été développé pour calculer l'évolution de la fluorescence avec la température, concentration des espèces et pression. Ce modèle a été validé avec des mesures de fluorescence et d'absorption obtenues dans une cellule optique fonctionnant jusqu'à 800 K et 20 bar puis dans un brûleur laminaire haute-pression. De ce modèle a été définie une stratégie permettant la mesure de la distribution instantanée de NO dans une flamme stratifiée. Une étude similaire pour détecter CO a été ensuite initiée. Des mesures de fluorescence à deux photons ont été obtenues dans la cellule et dans une flamme plate atmosphérique. Les résultats montrent que cet outil est opérationnel, répondant à un besoin pour l'amélioration des performances des systèmes de propulsionThis PhD work is to develop a quantitative imaging technique for measurements of the concentration of pollutants in reactive flows. On one hand, the concern was to develop the NO fluorescence imaging technique. For this purpose, an n-level fluorescence model was first developed to calculate the behavior of fluorescence signals with temperature, species concentration, and pressure. Then this model was validated with fluorescence and absorption measurements acquired in an optical cell up to 800 K and to 20 bar and in a high-pressure laminar burner. From this model, a strategy used to measure the instantaneous NO distribution in a stratified flame was defined. Then, a similar study to detect CO with fluorescence was then investigated. Two-photon fluorescence measurements were performed in the optical cell and in a flame. The results make clear that the spectroscopic diagnostic becomes operational with the need to improve the performances of propulsion systems
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Russell, Jared S. "An optimization approach to plant-controller co-design /." Online version of thesis, 2009. http://hdl.handle.net/1850/10769.
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Tamburrini, Simone. "Produzione e caratterizzazione di componenti in WC-Co mediante selective laser melting." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
Знайти повний текст джерелаАнотація:
Uno dei temi chiave della ricerca sull’Additive Manufacturing (AM) è l’accrescimento del campo di materiali processabili. La tecnologia garantisce diversi vantaggi rispetto alle normali tecniche di lavorazione ma richiede esperienza nella lavorazione e conoscenza del materiale. Nello studio oggetto di questa dissertazione si mostrano i risultati di un primo approccio alla lavorazione di WC-Co (carburo di tungsteno in matrice di cobalto) attraverso Selective Laser Melting (SLM). Lo scopo è di gettare le basi per un processo che permetta la produzione di utensili da taglio in WC-Co. Lo studio si è incentrato su un’attenta analisi microstrutturale di diversi gruppi di campioni processati attraverso SLM e prodotti a partire da due polveri a diverso contenuto di Co (9% e 17%). Le densità, le durezze e le microstrutture ottenute sono state confrontate con quelle relative a prodotti sinterizzati industriali. Lo studio ha portato a nuove conoscenze sulla microstruttura del materiale derivante dalla lavorazione ed ha permesso di stabilire relazioni tra parametri di processo e densità del prodotto finale. Per l’ultimo gruppo di campioni prodotto (17% di Co) si è ottenuto un miglioramento in termini di qualità del materiale prodotto, nel particolare si è incrementata la densità e ridotta l’estensione di difetti microstrutturali quali cricche e porosità.
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Bernegger, Stefan. "Co-laser photoacoustic spectroscopy of gases and vapors for trace gas analysis /." [S.l.] : [s.n.], 1988. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=8636.
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Repond, Philippe. "Photoacoustic spectroscopy on gases with a continuously tunable high pressure CO₂ Laser /." Zürich, 1995. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=11047.
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Baumgartner, Michael Oliver. "Nonlinear interactions of 10 {mü}m TEA-CO₂ laser pulses with ammonia /." Zürich, 1997. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=12513.
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McIntosh, Grant William John. "A study of stimulated Raman scattering in a CO₂ laser produced plasma." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27440.
Повний текст джерелаАнотація:
Stimulated Raman scattering (SRS) has been studied experimentally in a CO₂ laser plasma interaction. A N₂ gas jet target was irradiated with CO₂ laser light (wavelength, ⋋ = 10.6 µm and frequency, ѡ₀) at intensities up to 10¹⁴ Wcm⁻². SRS occurs at intensities greater than 3 x 10¹³ Wcm⁻², which is fair agreement with threshold predictions for a plasma with an electron temperature of 300eV and a density scale length of 300µm. After this intensity is reached, the plasma waves grow exponentially in time with a growth rate of 6 x 10⁻³ѡ₀. This was measured with ps resolution ruby laser Thomson scattering. Spatial growth was also observed. Scattered infrared light at 2⋋ was found. Weak IR light in a broad band near 15µm was also found. The saturated plasma wave level and the number of hot electrons at 150 keV are well correlated, which indicates that trapping is responsible for the electrons. However, trapping is not responsible for the saturation of the instability. Frequency resolved Thomson scattering revealed that ion acoustic waves start at the peak of the SRS fluctuations. Once the ion acoustic waves grow to a large amplitude, SRS is quenched and does not reappear.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Gu, Hongping. "Real-time monitoring and adaptive control of CO¦2 laser beam welding." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0020/NQ38242.pdf.
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Fraser, Alex. "Réalisation d'un banc de micro-usinage de fibres optiques avec laser CO₂." Master's thesis, Université Laval, 2008. http://hdl.handle.net/20.500.11794/19889.
Повний текст джерелаАнотація:
Un système de micro-usinage de fibres optiques utilisant un laser CO₂ comme source de chaleur a été fabriqué. Il s'agit d'un système hybride pouvant réaliser l'étirage et l'usinage de fibres optiques. Le système utilise un laser puisé dont la puissance moyenne peut atteindre deux cents Watts combiné à un modulateur acousto-optique (AOM). On présente une méthode permettant de générer dans la fibre une zone chaude uniforme de longueur ajustable. Cette uniformité est obtenue en synchronisant correctement les impulsions laser avec le scanner. Une méthode pour mesurer le diamètre d'une fibre effilée en temps réel durant son étirage est présentée. Elle consiste en un deuxième laser qui balaye la fibre de façon perpendiculaire et une photodiode qui capte le signal transmis au-delà de la fibre. L'efficacité d'usinage ([mu]m³/J) et l'efficacité de perçage (
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Wazen, Paul. "Laser NH₃ moyen-infrarouge continu pompe optiquement par laser CO₂ : laser et amplificateur de puissance de type Raman, laser à inversion de population accordable en fréquence par effet Stark." Paris 11, 1987. http://www.theses.fr/1987PA112164.
Повний текст джерелаАнотація:
Cette thèse concerne le laser NH3 moyen-infrarouge continu pompé optiquement par laser C02·Le chapitre 1 rappelle les données spectroscopiques sur la molécule NH3 et l'influence d'un champ électrique sur son spectre de rotation-vibration (effet Stark). Le chapitre II concerne Je pompage optique hors résonance et le développement de sources Raman de puissance. Il est divisé en deux parties : La partie A porte sur l'analyse du gain local à 12 μm en fonction des principaux paramètres. L'étude, la réalisation et l'optimisation d'un laser Raman en anneau continu à 12 μm à puissance modérée sont décrites à la suite. La partie B porte sur l'étude d'un amplificateur Raman continu. Un premier modèle de propagation, simplifié, mais analytique est développé. Un second modèle numérique est mis au point qui tient compte des distributions transverses des intensités (pompage et Raman) et des effets d'échauffement. Les expériences sur un système oscillateur-amplificateur à 12,08 μm confirment la validité du modèle élaboré. Des lois d'échelle pour des systèmes de haute puissance sont établies. Le chapitre III concerne l'accordabilité en fréquence du laser NH3 à inversion de population pompé optiquement en résonance. Un modèle à taux de population du gain à faible signal est établi. La directionnalité des émissions et le fonctionnement multi-raie sont exposés brièvement. L'accordabilité en fréquence par élargissement en pression est étudiée ainsi que la mise au point d'une cavité sélective de type Fox-Smith. Les résultats d'accordabilité en fréquence par effet Stark, la réalisation d'un guide d'onde hybride sont décrits ensuite. Un modèle simple est développé pour interpréter les résultats expérimentauxThis thesis is directed at the study of the C02-pumped Mid-Infrared NH3 Chapter 1 gives some spectroscopic data for the ammonia molecule. The influence of an electric field on its rotation-vibration spectrum (Stark effect) is recalled. Chapter II which concerns the off-resonance pumping of NH3 and the development of powerful Raman sources is divided into two parts: In part A the 12 μm local gain is analyzed as a function of the main parameters. The sudy, realization and optimization of a ring CW 12 m Raman laser are described. In part B, a CW Raman amplifier is studied. A first simplified, but analytical propagation model is developed. A second numerical model is elaborated which includes both the transverse intensity profiles (Raman and pump) and the heating effects. Experiments carried out on a 12. 08 μm oscillator-amplifier system confirm the validity of this model. Scaling laws are established for high power systems. Chapter III is related to the frequency tunability of an NH3 laser with population inversion (on-resonance pumping). A rate equation model is established for the small signal gain. Results on Multiline operation and bidirectional emissions are briefly reported. The frequency tunability of the pressure-broadened emissions is inverstigated using a Fox-Smith laser cavity. The Stark tuning of the laser and the realization of a hybrid waveguide are then described. A simple line shape model is developed to interprete the experimental results
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Remy, Bertrand. "Étude et réalisation d'un imageur actif laser à compression d'impulsion." Paris 11, 1986. http://www.theses.fr/1986PA112346.
Повний текст джерелаАнотація:
Cette thèse présente l'étude et la réalisation d'un imageur actif à laser CO₂ basé sur l'emploi d'un laser continu monomode, de la détection hétérodyne et de la compression d'impulsion. Un modèle théorique en est donné : bilan de portée, résolution angulaire, en distance et en vitesse Doppler ; l'influence sur l'hétérodynage optique des phénomènes de granularité laser, de turbulence atmosphérique, de la mauvaise adaptation des taches signal et oscillateur local au niveau du détecteur et des aberrations du système optique. On évalue également plusieurs systèmes de balayage angulaire et on compare leur performance en terme de précision Doppler. L'imageur réalisé après optimisation des choix comporte 64 lignes de 128 points dans un champ de 1 ° x 0,5 °. Les trois images Distance/Réflectance et Doppler sont four nies simultanément à une cadence de 1,5 Hz. Les essais ont confirmé la validité de la modélisation et permettent de juger de l'intérêt comparé de ces images nouvelles dont le domaine potentiel d'application apparait très vasteThe thesis describes the breadboard of an imaging CO₂ laser radar based upon the use of a CW waveguide single mode laser, heterodyne detection and chirp pulse compression. A theoretical model of the system is given: overall performance, angular, range and Doppler precisions are estimated, as well as the influence of heterodyne mixing, speckle, atmospheric turbulence and optical aberrations. An evaluation of several scanning devices is also given, that compares their performance as far as Doppler precision is concerned. Parametric optimization of this imaging system has 1ed to a total field of view of 0,5° x 1° (corresponding to 64 x 128 points). The 3 images Range-Doppler Velocity and Reflectivity are generated at a repetition rate of about 1,5 Hz. Field tests and experimental results confirm the theoretical investigations and help compare the relative interests of these new images in a wide range of applications
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Perron, Denis. "Fabrication d'un réseau à long pas à l'aide d'un laser au CO¦2." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ60913.pdf.
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Shafique, Muhammad Farhan. "Laser Prototyping of Low Temperature Co-fired Ceramics for System-In-Package Applications." Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521480.
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Cretteur, Laurent. "Etude du soudage des alliages d'aluminium par laser co#2 de forte puissance." Nantes, 1998. http://www.theses.fr/1998NANT2094.
Повний текст джерелаАнотація:
Les alliages d'aluminium, du fait de leur proprietes physiques, sont parmi les metaux les plus delicats a souder par laser co#2. En effet, ils demandent une energie incidente beaucoup plus elevee que les autres metaux. Ceci se traduit par des instabilites du bain de fusion et des exces de plasma. De plus le bain, relativement large, tend a s'effondrer sous la tole. Cette these vise a developper le soudage laser de deux alliages aluminium-magnesium utilises dans l'industrie (5086 et 6061). Son approche est essentiellement experimentale. Dans un premier temps, une etude de l'influence des parametres experimentaux a ete realisee. L'influence de la nature du gaz de couverture et de son mode d'injection a en particulier ete etudiee : l'utilisation d'un systeme d'amenee de gaz comprenant une buse annulaire et un tube chasse plasma lateral apporte une stabilisation significative du procede. Cependant, la qualite des cordons reste faible, en particulier sur leur cote envers. Pour reduire ces defauts, nous avons developpe une technique originale. Un melange de sels mineraux (flux-pate) a ete optimise dans le but de limiter l'oxydation du bain et de le maintenir en position lors du soudage. Ce flux-pate, compose d'un melange de chlorures et de fluorures, possede des proprietes tensioactives qui limitent l'effondrement du bain. De plus, il protege de l'oxydation l'envers de la soudure : les cordons obtenus sont donc parfaitement reguliers. La deuxieme partie de ce travail est une validation du produit mis au point. L'etude de l'influence du flux-pate sur les porosites montre un effet benefique vis a vis des grosses cavites. Des essais de traction normalises font d'autre part apparaitre un bon comportement mecanique des soudures produites. Ainsi, nous montrons que le flux-pate n'induit pas de fragilites des soudures, et que leurs capacites mecaniques dependent essentiellement des traitements thermiques post-soudage effectues.
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Ablikim, Utuq. "Fragmentation of molecular ions in ultrafast laser pulses." Kansas State University, 2015. http://hdl.handle.net/2097/18962.
Повний текст джерелаАнотація:
Master of ScienceDepartment of Physics
Itzhak Ben-Itzhak
Imaging the interaction of molecular ion beams with ultrafast intense laser fields is a very powerful method to understand the fragmentation dynamics of molecules. Femtosecond laser pulses with different wavelengths and intensities are applied to dissociate and ionize molecular ions, and each resulting fragmentation channel can be studied separately by implementing a coincidence three-dimensional (3D) momentum imaging method. The work presented in this master’s report can be separated into two parts. First, the interaction between molecular ion beams and femtosecond laser pulses, in particular, the dissociation of CO[superscript]+ into C[superscript]++O, is studied. For that purpose, measurements are conducted at different laser intensities and wavelengths to investigate the possible pathways of dissociation into C[superscript]++O. The study reveals that CO[superscript]+ starts to dissociate from the quartet electronic state at low laser intensities. Higher laser intensity measurements, in which a larger number of photons can be absorbed by the molecule, show that the doublet electronic states with deeper potential wells, e.g. A [superscript]2Π, contribute to the dissociation of the molecule. In addition, the three-body fragmentation of CO[subscript]2[superscript]+ into C[superscript]++O[superscript]++O[superscript]+ is studied, and two breakup scenarios are separated using the angle between the sum and difference of the momentum vectors of two O[superscript]+ fragments. In the second part, improvements in experimental techniques are discussed. Development of a reflective telescope setup intended to increase the conversion efficiency of ultraviolet (UV) laser pulse generation is described, and the setup is used in the studies of CO[superscript]+ dissociation described in this report. The other technical study presented here is the measurement of the position dependence of timing signals picked off of a microchannel plate (MCP) surface. The experimental method is presented and significant time spread over the surface of the MCP detector is reported [1].
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Eilers, Gerriet, Anders Persson, Cecilia Gustavsson, Linus Ryderfors, Emad Mukhtar, Göran Possnert, and Mehran Salehpour. "The Radiocarbon Intracavity Optogalvanic Spectroscopy Setup at Uppsala." Uppsala universitet, Tillämpad kärnfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-202651.
Повний текст джерелаАнотація:
Accelerator mass spectrometry (AMS) is by far the predominant technology deployed for radiocarbon tracer studies. Applications are widespread from archaeology to biological, environmental, and pharmaceutical sciences. In spite of its excellent performance, AMS is expensive and complicated to operate. Consequently, alternative detection techniques for 14C are of great interest, with the vision of a compact, user-friendly, and inexpensive analytical method. Here, we report on the use of intracavity optogalvanic spectroscopy (ICOGS) for measurements of the 14C/12C ratio. This new detection technique was developed by Murnick et al. (2008). In the infrared (IR) region, CO2 molecules have strong absorption coefficients. The IR-absorption lines are narrow in line width and shifted for different carbon isotopes. These properties can potentially be exploited to detect 14CO2, 13CO2, or 12CO2 molecules unambiguously. In ICOGS, the sample is in the form of CO2 gas, eliminating the graphitization step that h is required in most AMS labs. The status of the ICOGS setup in Uppsala is presented. The system is operational but not yet fully developed. Data are presented for initial results that illustrate the dependence of the optogalvanic signal on various parameters, such as background and plasma-induced changes in the sample gas composition.
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Ouyang, Donald N. B. "The dynamic modelling of industrial oxygen gas jet assisted CO₂ laser cutting of metal." Thesis, University of Glasgow, 1998. http://theses.gla.ac.uk/2475/.
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Bergh, Anna. "Defocused CO₂ laser irradiation in the rehabilitation of horses : an experimental and clinical study /." Uppsala : Dept. of Anatomy and Physiology, Swedish University of Agricultural Sciences, 2006. http://epsilon.slu.se/200654.pdf.
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Wei, Tao. "Fabrication of long-period fiber gratings by CO₂ laser irradiation for high temperature applications." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Wei_09007dcc804a8ac2.pdf.
Повний текст джерелаАнотація:
Thesis (M.S.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 31, 2008) Includes bibliographical references (p. 33-36).
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Bonilla, Francisco Javier. "Nanofils ferromagnétiques auto-assemblés de Co, Ni et d’alliages CoNi : croissance, structure et propriétés magnétiques." Paris 6, 2013. http://www.theses.fr/2013PA066244.
Повний текст джерелаАнотація:
Cette thèse est consacrée à l’étude de nanofils de Co, Ni et d’alliages CoNi auto-assemblés dans une matrice de CeO2/SrTiO3(001). La croissance de ces systèmes est effectuée par ablation laser pulsé. Les nanofils obtenus ont un diamètre compris dans la gamme 1. 5 - 7 nm, en fonction des conditions de croissance. Pour chaque type de nanofils (Co, Ni et alliages CoNi), la composition, la morphologie, la structure cristalline et les propriétés magnétiques ont été étudiées en utilisant une combinaison de techniques (spectroscopie d’absorption X, microscopie électronique en transmission, diffraction des rayons X, magnétométrie). Les nanofils de cobalt sont texturés et anisotropes avec une direction de facile aimantation le long de l’axe. Une corrélation est établie entre la structure des fils et leurs propriétés magnétiques. Elle est étayée par un modèle micro-magnétique de renversement de l’aimantation. Les nanofils de nickel sont monocristallins et épitaxiés dans la matrice. Leur comportement magnétique est très faiblement anisotrope contrairement au Co. Les études structurales révèlent une déformation axiale qui induit une anisotropie magnéto-élastique. Cette contribution magnétoélastique compense l’anisotropie de forme des fils, ce qui est reproduit qualitativement par des simulations micro-magnétiques. Des pistes sont proposées pour éviter cet effet et augmenter l’anisotropie magnétique. Les nanofils d’alliages sont mono-cristallins, épitaxiés et anisotropes magnétiquement. L’anisotropie totale du système peut être contrôlée par la fraction de cobalt dans l’alliage. Finalement, des perspectives ouvertes par ces travaux sont ébauchéesThis thesis reports on the study of self-assembled ferromagnetic nanowires of Co, Ni and CoNi alloys embedded in a CeO2/SrTiO3(001) matrix. These systems are grown by pulsed laser deposition. The nanowires have diameters in a 1. 5 -7 nm range, depending on the growth conditions, and densities above 1 Tb/inch2. For each type of nanowires (NWs) assembly (Co, Ni, CoNi alloys), the composition, morphology, crystalline structure and magnetic properties were studied using a combination of techniques (X-ray absorption spectroscopy, transmission electron microscopy, X-ray diffraction, magnetometry). Co-NWs are textured and anisotropic, with an easy axis along the wire axis. The correlation between the magnetic response and the structure is evidenced and corroborated by means of a model for the mechanism of magnetization reversal. Ni-NWs are monocrystalline and epitaxied with the surrounding matrix. Contrary to Co-NWs, the Ni-NWs are not anisotropic. Structural studies reveal an axial deformation of the Ni lattice. This introduces a magnetoelastic anisotropy term competing with the wires shape anisotropy. The compensation of the different anisotropies in the Ni-NWs is further supported by of micromagnetic simulations. Based on these results, some alternatives to tune the magnetic anisotropy in Ni-NWs are presented. CoxNi1-x alloy NWs, obtained from a combinatorial growth method, are monocrystalline, epitaxied and anisotropic. It is shown that the total magnetic anisotropy of the system can be tuned by controlling the Co content in alloy NWs. Finally, perspectives issued from this work are sketched
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Prisbrey, Shon Thomas. "Structural and magnetic fluence dependence in Co₀.₀₃₈Ti₀.₉₆₂O₂₋[delta] and Co₀.₀₄₉Ti₀.₉₅₁O₂₋[delta] thin films synthesized in pulse laser deposition /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--University of California, Davis, 2005.Degree granted in Physics. On title page "[delta]" appears as lower-case, subscript Greek letter. Also available via the World Wide Web. (Restricted to UC campuses)
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Pal, Avishekh. "Laser Remote Sensing of Trace Chemical Species Using 10.6 μm CO2 Laser Enhanced Breakdown Spectroscopy and Differential Absorption Lidar". Scholar Commons, 2008. https://scholarcommons.usf.edu/etd/441.
Повний текст джерелаАнотація:
Several different laser remote sensing techniques related to the detection of trace chemical species were studied. In particular, a Differential-Absorption lidar (DIAL), a Laser-Induced-Breakdown Spectroscopy (LIBS) lidar, and a Raman lidar were studied. Several of the laser spectroscopic techniques that were used were common throughout these different studies. More precisely, 10.6 μm CO2 laser related spectroscopy was common for the DIAL and LIBS studies, and 266 nm Nd:YAG laser related spectroscopy was used for the LIBS and Raman studies.
In the first system studied a tunable CO2 DIAL system was developed for the first time to our knowledge for the potential detection of the explosive Triacetone Triperoxide (TATP) gas clouds. The system has been used to measure gas samples of SF6, and has shown initial absorption measurements of samples of TATP contained within an enclosed optical absorption cell. DIAL/Lidar returns from a remote retroreflector target array were used for the DIAL measurements after passage through a laboratory cell containing the TATP gas. DIAL measured concentrations agreed well with those obtained using a calibrated Ion Mobility Spectrometer. DIAL detection sensitivity of the TATP gas concentration in the cell was about 0.5 ng/μl for a 0.3 m path-length. However, the concentration of TATP was found to be unstable over long periods of time possibly due to re-absorption and crystallization of the TATP vapors on the absorption cell windows. A heated cell partially mitigated these effects.
In the second set of studies, a Deep UV LIBS system was developed and studied for the remote detection of solid targets, and potentially chemical, biological, and explosive substances. A 4th harmonic Q-Switched Nd:YAG laser operating at 266 nm was used for excitation of the LIBS plasma at standoff ranges up to 50 m . The LIBS plasma emission covering the range of 240 – 800 nm was enhanced by use of a nearly simultaneous 10.6 μm CO2 laser that increased the LIBS plasma emission by several orders of magnitude. The emission spectrum was used to detect and identify the species of interest. Plasma temperatures on various solid substrates were measured. An increase in the plasma temperature of about 5000 K was measured and analyzed, for the first to our knowledge, due to the addition of the CO2 laser pulse to the LIBS plasma generated by the Nd:YAG laser. An optimum temporal overlap of the two laser pulses was found to be important for the enhancement.
Finally, in a third related lidar system, initial 266 nm Raman lidar studies were conducted at detection ranges of 15 m. However, significant spectroscopic background interferences were observed at these wavelengths and additional optical filtering is required.
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Hartmann, Jean-Michel. "Etude de l'absorption infra-rouge par des mélanges gazeux H2O-CO2-CO-Air à température élevee : modélisation, pour l'ingenieur, des propriétés radiatives : approches théorique et expérimentale de l'élargissement par collisions de raies de H2O et CO." Châtenay-Malabry, Ecole centrale de Paris, 1986. http://www.theses.fr/1986ECAP0013.
Повний текст джерелаАнотація:
Etude de l'absorption IR pour H2O, CO2 et CO gazeux à haute température. Analyse de la validité de modèles simplifiés pour la modélisation des propriétés radiatives de H2O et CO2 à basse résolution. Étude expérimentale de l'élargissement collisionnel de raies IR à haute résolution par diode laser : intensités et coefficients d'élargissement des raies de H2O et CO entre 300 et 900 k. Proposition d'un modèle pour l'élargissement des raies de H2O