Dissertations / Theses on the topic 'Laser ablation'
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Kapitan, Daniel. "Laser ablation with copper vapour lasers." Thesis, University of Oxford, 1999. https://ora.ox.ac.uk/objects/uuid:a1dc1a3b-602a-4ebb-abe2-734e8e11f15a.
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The use of copper vapour lasers for laser ablation in laser materials processing applications is studied. To this purpose, the generation of near diffraction-limited beam quality output from a single medium-scale oscillator is demonstrated via matching the total buffer gas pressure to the specific electrical input power loading and the degree of insulation of the plasma tube. The design and characterisation of a Master-Oscillator Power-Amplifier system based on a smallbore oscillator is also described, focusing on pulse stretching techniques to provide efficient seeding required for producing 20-50 W high beam-quality output for laser materials processing purposes. Various experimental studies on the fundamental processes of laser ablation of metals are presented. The effect of the background gas properties on shock-wave formation in laser generated plasmas is studied using a ballistic pendulum. The experimental findings are found to be accurately described by a modified Sedov-Taylor-Von Neumann theory which accounts for the effect of the piston-mass. The theory is applied to characterise the fluorination process in the shock-wave, in view of oxygen isotope analysis in geochemistry. Atomic emission spectroscopy is shown to provide some measure of the electron temperature and electron density at the plasma core. The experimental results are discussed in view of existing models to describe the extreme Stark-broadening and self-absorption in dense, cool plasmas. A comparative study of the use of femtosecond and nanosecond pulsed lasers for laser ablation of metals is presented to assess the relative importance of thermal diffusion. Measurement of the recoil momentum due to ejection of molten particulates during ablation in vacuum provides insight into the effect of material properties. Diffusion-limited surface texturing of metals via direct transfer of an optical interference patterns is demonstrated.
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Chan, Kin Foong. "Pulsed infrared laser ablation and clinical applications /." Digital version:, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992765.
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Jansen, Andrew. "Laser ablation ICP spectrometry." Thesis, Sheffield Hallam University, 1998. http://shura.shu.ac.uk/19868/.
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This thesis reports investigations into laser ablation inductively coupled plasma emission spectrometry for rapid elemental analysis of a diverse range of samples: glasses, aqueous solutions, oils, coated steels and glasses, and biological samples. Bulk analysis of glasses for major, minor and trace elements is reported. Results showed that element emission responses are dependent upon laser operating conditions. With optimised operating conditions of a Q switched laser operating at 60 J for 5 s ablation time with the laser defocused by 5 mm above the sample surface. The limits of detection are in the sub ug g -1 level with precision ranging from 6.6 %RSD for a non volatile element such as boron to 23 %RSD for a volatile element silver. Although the principal aim of using aqueous multielement solutions as novel calibration standards for quantitative analysis of other liquids was not achieved, optimised laser operating parameters needed for microsampling of aqueous solutions and analytical performance data were obtained. The optimum laser operating conditions for a 20 ul sample were found to be the same as for glasses and were as follows: a Q switched laser operating at 60 J for a 5 s ablation time with the laser defocused by 5 mm above the sample surface. Transport efficiencies of approximately 30 % can be achieved, compared to < 1% by pneumatic nebulisation. Also there was no differential loss of elements by laser ablation which may occur with electrothermal vaporisation. Limits of detection were found to be in the sub ug ml -1 level. Precisions were typically between 6.6 and 12 %RSD. The main cause for lack of precision was spattering of the sample. Microsampling of oils by laser ablation proved to be an effective and accurate technique for rapid determination of element concentration without the need for sample filtration or digestion. Precision proved to be better than for aqueous solutions, typically from 3 to 7 %RSD, because of a reduction in spattering. The same optimum laser operating conditions used for aqueous solutions were identical for oils. This thesis reports the first experiments to fully utilise laser ablation as a routine method for quantitative measurement of coating depth for coated steels and glasses. It was found that the peak width at half the maximum height was proportional to the coating thickness (over a range of 1 to 10 um). With optimised laser operating conditions a depth resolution of less than 1 um was achieved. The optimum laser operating conditions were as follows: a Q switched laser ran continuously with a laser lamp energy of 60 J at 10 Hz pulse repetition rate. Finally experiments show the great potential for the use of laser ablation as a microsampling technique for microtome tissue samples. Micro depth analysis of nickel distribution in skin shows that the technique could differentiate between two skin samples with different nickel concentrations. The use of gel multielement standards as a novel calibration technique for analysis of microtome tissue samples has also been demonstrated. Optimum laser operating condition were to use a moderate laser energy of 750 V with the laser defocused 5 mm above the sample surface.
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Lippert, Thomas. "Photopolymers designed for laser ablation ablation mechanisms and applications /." Zürich : ETH, Eidgenössische Technische Hochschule Zürich, Paul Scherrer Institut, Materials Development and Characterization Group, 2002. http://e-collection.ethbib.ethz.ch/show?type=habil&nr=8.
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Pinho, George Paul. "UV laser ablation of metals." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0016/NQ38265.pdf.
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Robert, Stewart. "Laser ablation within enclosed surfaces." Thesis, University of Manchester, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.690045.
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Terragni, Jacopo. "Laser Ablation for Space Applications." Doctoral thesis, Università degli studi di Trento, 2022. https://hdl.handle.net/11572/339556.
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Musaev, Omar Wróbel Jerzy. "UV laser assisted processing of InP at different ambient conditions with variable number of pulses and fluences." Diss., UMK access, 2006.
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Thesis (Ph. D.)--Dept. of Physics and School of Computing and Engineering. University of Missouri--Kansas City, 2006."A dissertation in physics and telecommunications networking." Advisor: Jerzy Wrobel. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Nov. 1, 2007. Includes bibliographical references (leaves 185-190). Online version of the print edition.
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Crossland, J. D. "Computer modelling of laser-plasma ablation." Thesis, University of Hull, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384648.
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Smyth, Catherine. "YBCO thin films by laser ablation." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239224.
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Sun, Lu. "Laser nano-ablation for humidity detection." Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/64820.
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Nano-scale fabrication of technical materials is one of the biggest challenges in future industrial applications. There is a growing need for components with feature sizes below one micron. The well-established techniques, including e-beam lithography and focused ion beam milling, suffer several limitations, such as expensive apparatus, low fabrication speed and small scale production. Laser nano-ablation, as an efficient implementation method, has offered promising merits in large scale nano-fabrication. First applied to polymers, it offered a one-step fabrication ability with sub-micron structuring resolution. Later, following the pioneering work of Stuke and co-workers, surface treatment of non-polymeric materials, such as crystals, metals and semiconductors was achieved using picosecond and femtosecond laser systems. In this thesis, laser nano-ablation was used to fabricate large scale nano-hole arrays on polyimide films to improve the performance of humidity sensors. A 193 nm ArF pulsed laser system was established, simulated and optically aligned. Hole arrays with 920 nm diameter at the top, 339 nm diameter at the bottom and 451 nm depth were produced using mask projection ablation on polyimide films. Interdigitated polyimide humidity sensors were fabricated, packaged and tested. Based on conformal mapping and partial capacitance, capacitance modelling of interdigitated electrode arrays was built to analyse the capacitance variations with electrode dimensions. A reliable home-made humidity chamber was established for sensor tests. Static and dynamic tests were carried out to characterize the sensor performance. Static tests showed the nano-patterned films can enhance the sensitivity by 7.1% at humidity levels below 68% RH and by 100% at humidity levels higher than 68% RH. In addition, dynamic test showed that the nano-patterned polyimide films are able to improve the response speed by about 20%. Overall, this thesis demonstrates that large-area nano-hole arrays formed by laser ablation can improve the sensitivity and response time of polyimide-based capacitive humidity sensors.
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Prevosti, Stefano. "Ablation of Si with femtosecond laser." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-196217.
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Femtosecond laser ablation of different materials is becoming more and more important in micro- and nanomachining fields. The cutting precision and cost-effectiveness related to this method are turning it into a valid alternative to traditional methods. Coupling it with PDMS-assisted microtransfer printing could establish a completely new process of fabrication. In this work, ablation parameters were optimized to cut square shapes (sometimes referred to as “inks”) on the silicon device layer of a thin-film SOI (silicon-on-insulator) wafer. Specifically, the effect of repetition rate, power, number of passes, feed rate and cutting direction was investigated. A scanning electron microscope was used to determine the quality of the cuts. Qualitatively, the ablated lines were in accordance with results reported in the available literature but with smaller cut width due to the smaller spot size. After etching of the buried oxide, PDMS retrieval of the inks was attempted. While not entirely successful, the results were promising for further investigation.Karvning i olika material med en femtosekundlaser blir en alltmer betydelsefull tillvägagångs sätt inom fabrikations processer i mikro och nanostorlek. Skärprecisionen och kostnadseffektiviteten som följer med denna metod gör detta till ett bra alternativ gentemot traditionella metoder. Kombinera denna metod med förflyttning av strukturer med hjälp av PDMS så kan en helt ny fabrikationsprocess etableras inom tillverkning av mikro och nanostrukturer. I detta projekt så optimeras fabrikations parametrar för att skära kvadratiska former (så kallade ”inks”) i kisel lagret på SOI (kisel-på-isolator) skivor. Mer specifikt så analyserades effekten av repetitionshastigheten, kraften, antal passager, matningshastighet och skärriktningen. Ett elektronmikroskop användes för att döma kvaliteten av snitten som utfördes med denna metod. Kvalitativt sätt så var de utskurna linjerna i enlighet med tidigare resultat som har rapporterats inom den tillgängliga litteraturen men med mindre snittbredd på grund av den mindre punktstorleken. Efter att man etsat bort det underliggande oxidlagret så gjordes det försök med att plocka upp ”inks” med hjälp av PDMS-material. Fast än dessa försök inte blev full så framgångsrika så gav de ändå lovande resultat för framtida forskning.
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Claeyssens, Frederik. "Fundamental studies of pulsed laser ablation." Thesis, University of Bristol, 2001. http://hdl.handle.net/1983/fa30b147-9096-4025-97c3-9426c0f033d7.
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MUTISYA, STEPHEN. "SYNTHESIS OF NANOCOMPOSITES BY LASER ABLATION." VCU Scholars Compass, 2011. http://scholarscompass.vcu.edu/etd/231.
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Immunoglobulin E (IgE)-conjugated gold nanoparticles were produced via in situ conjugation of gold nanoparticles with immunoglobulin E by laser ablation of Au in a liquid solution. The colloidal stability and the size distribution of the resulting bio-nanoconjugates were examined with UV-Visible spectroscopy (UV-Vis), dynamic light scattering (DLS), and transmission electron microscopy (TEM). These techniques showed that the Au nanoparticles in aqueous solutions were highly monodispersed spherical particles with a very narrow size distribution. The particles net diameter using TEM, was found to be D5 =3.8±0.9nm and D10 =4.7±1.3nm while the hydrodynamic diameter obtained with DLS was found to be h5 D =171±12nm , h10 D =164±18nm for 5min and 10min laser ablation time respectively. Enzyme-Linked immunosorbent Assay (ELISA) and flow cytometry measurements of the conjugates confirmed that the gold-bound protein remained biologically active, thus paving the way for the application of these nanoparticles in immuno-diagnostics, particularly in tumor-targeted drug delivery.
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Hobbs, Lauren. "Extreme ultraviolet probing of laser ablation." Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/1605/.
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This thesis details the use of extreme ultraviolet (EUV) sources in probing laser ablation and material opacity. The radiation hydrodynamic codes POLLUX and h2d are used to study the Rayleigh-Taylor instability in a regime relevant to inertial fusion energy and, in support of experimental effort, to test the feasibility of methods for measurement of iron opacity. Simulations of EUV radiography using the POLLUX code show how the presence of warm, dense material leads to strong absorption of the probe beam. Methods using both broad and narrowband EUV wavelength probes for benchmarking theoretical models of opacity are presented. An iron opacity experiment conducted at the Bhabha Atomic Research Centre is modelled, where K_alpha emission from an aluminium layer is used to probe an iron layer beneath. H2d simulations of laser heated iron, conducted to determine the suitability of experimental results obtained at the Rutherford Appleton Laboratory for iron opacity, show the difficulty in preventing large temperature and density gradients from forming. Interferometry has been used to measure both transmission and phase information for a 21.2 nm zinc EUV laser beam probing longitudinally through laser ablated CH plastic at the Prague Asterix Laser System. By conducting interferometric probing with EUV laser light, the region of warm dense matter between the critical surface and ablation surface in a laser ablated plasma is diagnosed. Analysis of phase shifts reveals refractive indices below solid and plasma values arising in CH plastic, due to bound-free absorption in C+, a model for which is presented. The transmission of the EUV probe beam provides a measure of the rate of ablation, matching previous experimental scaling laws.
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Bouland, Antonin. "Recherche et optimisation des paramètres laser pour la décoration des matériaux polymères dans le secteur automobile." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS148.
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Dans un contexte très concurrentiel et de demande généralisée de personnalisation, le secteur automobile doit mettre sur le marché des produits de plus en plus attractifs et sans compromis sur la qualité et la fiabilité. Parmi les méthodes de décoration en cours de développement, le traitement de surface ou dans la masse par gravure laser offre des opportunités que Renault souhaite étudier sur les matériaux polymères et les peintures. Cependant, les procédés actuels sont développés sans avoir la compréhension des phénomènes physicochimiques liés à la transformation de la surface. Le plus souvent les matériaux d’intérêt industriel ne sont pas les matériaux modèles utilisés dans les études scientifiques et les résultats de ces études ne sont pas quantitativement transférables à l’application visée. De plus, une multitude de machines lasers apparemment proches sont disponibles sur le marché pour répondre à un même type de cahier des charges en termes de gravure laser, sans toutefois que les paramètres d’usinage soient transférables d’une machine à l’autre. Nous proposons dans cette thèse d’étudier la gravure laser de polymères pour maitriser la transférabilité du procédé. Nous avons instrumenté une machine industrielle afin de la caractériser exhaustivement. Nous avons également réalisé des inter-comparaisons entre machines présentant des caractéristiques proches. Grâce à ces deux approches nous avons pu assurer des conditions optimales de reproduction d’une gravure laser d’une machine à une autre. Nous avons par ailleurs qualifié les gravures lasers vis-à-vis du cahier des charges RENAULT. Ceci nous a permis de déterminer les points forts et les points faibles de la technologie pour un objectif de décoration industriel et de mettre en évidence des leviers d’optimisation du procédé de gravure laser. Enfin nous avons évalué qualitativement et quantitativement les aérosols produits par la gravure laser afin d’assurer une protection optimale des personnes et de l’environnementFacing increasing competition and an ever-growing demand for customization, automotive manufacturers must deliver attractive products while not giving up on quality or reliability. Amongst several automotive interior decor techniques, surface treatment or laser engraving offer opportunities for Renault to study on polymers and paints. Current processes are developed without a correct understanding of physicochemical phenomenon linked to the surface’s transformation. Most frequently industrial materials are not same used as reference model in scientific research and the subsequent results cannot be quantitatively transferable to the intended industrial application. Moreover, a multitude of resembling engraving laser machines are available on the market for similar specifications for laser engraving, however engraving parameters are not necessarily transferable between different machines. We propose in this dissertation to study the laser engraving of polymer for understanding transferability of this process. We have equipped with sensor instruments an industrial engraving laser machine to characterize it exhaustively. We have also compared different machines with similar features. Through these two approaches, we are able to insure optimal conditions of reproductivity for laser engraving between two machines. In addition, we have characterized laser engraving according to RENAULT’s technical specifications. That has allowed us to determine the strong points and weaknesses of the technology for industrial decoration and to highlight optimization levers for laser engraving. Finally, we have evaluated qualitatively and quantitatively engraving lasers aerosol to assure an optimal protection for the personnel and the environment
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Ho, Wing Fat. "Pulsed laser ablation of liquids for spectrochemical analysis : effects of laser wavelength." HKBU Institutional Repository, 1997. http://repository.hkbu.edu.hk/etd_ra/127.
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Miyasaka, Yasuhiro. "Laser nano ablation induced by the interaction of femtosecond laser with metal surfaces." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/192139.
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Henneke, Dale Edwin. "Nanoparticles produced via laser ablation of microparticles." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3037496.
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Brendel, Tobias. "Untersuchungen zur IR-Laser-Ablation in Wasser." Doctoral thesis, [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972735801.
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Setia, Ronald. "Modeling and Diagnosis of Excimer Laser Ablation." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7634.
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Recent advances in the miniaturization, functionality, and integration of integrated circuits and packages, such as the system-on-package (SOP) methodology, require increasing use of microvias that generates vertical signal paths in a high-density multilayer substrate. A scanning projection excimer laser system has been utilized to fabricate the microvias. In this thesis, a novel technique implementing statistical experimental design and neural networks (NNs) is used to characterize and model the excimer laser ablation process for microvia formation. Vias with diameters from 10 50 micrometer have been ablated in DuPont Kapton(r) E polyimide using an Anvik HexScan(tm) 2150 SXE pulsed excimer laser operating at 308 nm. Accurate NN models, developed from experimental data, are obtained for microvia responses, including ablated thickness, via diameter, wall angle, and resistance. Subsequent to modeling, NNs and genetic algorithms (GAs) are utilized to generate optimal process recipes for the laser tool. Such recipes can be used to produce desired microvia responses, including open vias, specific diameter, steep wall angle, and low resistance. With continuing advancement in the use of excimer laser systems in microsystems packaging has come an increasing need to offset capital equipment investment and lower equipment downtime. In this thesis, an automated in-line failure diagnosis system using NNs and Dempster-Shafer (D-S) theory is implemented. For the sake of comparison, an adaptive neuro-fuzzy approach is applied to achieve the same objective. Both the D-S theory and neuro-fuzzy logic are used to develop an automated inference system to specifically identify failures. Successful results in failure detection and diagnosis are obtained from the two approaches. The result of this investigation will benefit both engineering and management. Engineers will benefit from high yield, reliable production, and low equipment down-time. Business people, on the other hand, will benefit from cost-savings resulting from more production-worthy (i.e., lower maintenance) laser ablation equipment.
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Sage, Rebecca S. "Mass spectrometric analysis of laser ablation plumes." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.495656.
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An experiment has been built to analyse the products of laser ablation. The species produced during the laser ablation event were sampled from the plume and analysed using a mass spectrometer. The mass spectrometer allowed the mass to charge ratio of the plume species to be determined. It also acted as a mass filter so that the time of flight distributions of individual plume species could be determined. The time-of-flight distributions were converted into velocity distributions, from this the mean kinetic energy and the ion intensities could be determined. The laser pulse energy (E), laser wavelength and the ablation target material were varied.
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Tobin, Jill M. "Laser induced plasma ablation of biological tissue." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15155.
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Chang, I.-Ta. "Excimer Laser Ablation of Polymer-Clay Nanocomposites." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1333995807.
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El, Aboudi Ilham. "Ablation laser UV à l'interface eau-polymère." Bordeaux 1, 2008. http://www.theses.fr/2008BOR13596.
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L'intérêt de ce travai original est de comprendre les différents processus physicochimiques impliqués dans l'interaction entre un laser excimère KrF et différents polymères (PET, PC, PI, PMMA et PS) en milieu aqueux. Dans ce but, nous avons investigué d'abord, les produits d'ablation retenus dans l'eau. Cette analyse a permis d'une part, la mise en évidence de la formation des nanoparticules organiques (carbone graphié ou polymériques) et d'autre part, d'étudier l'effet des paramètres du laser (fluence, nombre d'impulsions) sur leurs caractéristiques. Ensuite, l'expansion en temps réel de la plume d'ablation a été étudié grâce à la technique de la spectroscopie d'ablation induite par laser et à la théorie appliquée dans le diagnostic du plasma. Enfin, l'analyse de la cinétique d'ablation des polymères, et la modification chimique et topographique de leurs surfaces a permis de déceler l'effet du milieu environnant (air, eau) sur le processus d'ablation de ces matériaux. Les résultats sont discutés à l'aide des modèles théoriques qui ont été développés dans ce travail.
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Amer, Eynas. "Pulsed laser ablation studied using digital holography." Doctoral thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18194.
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Pulsed digital holographic interferometry has been used to study the plume and the shock wave generated in the laser ablation process on different targets under atmospheric air pressure. A pulsed Nd-YAG laser system (pulse duration 12 ns) has been used both for ablating the material (wavelength 1064 nm) and for measurement (wavelength 532 nm). Digital holograms were recorded for different time delays using collimated laser light passed through the volume along the target. Numerical data of the integrated refractive index field were calculated and presented as phase maps. The Radon inversion has been used to estimate the 3D refractive index fields measured from the projections assuming rotational symmetry. Intensity maps have been calculated from the recorded digital holograms and used to calculate the attenuation of the probing laser beam by the ablated plume. Qualitative and quantitative information have been extracted from both the phase map and the intensity map to help describing the laser ablation process. Also 3D information about the induced plume has been obtained by numerical reconstruction of the digital holograms at different planes along the plume. The amount of released energy due to laser impact on a PCBM target has been estimated using the point explosion model. The released energy is normalized by the incident laser pulse energy and the energy conversion efficiency between the laser pulse and the target has been calculated and it seems to be constant around 80 %. The 3D refractive index fields have been used to calculate the shock wave front density and the electron number density distribution within the induced plasma. The electron number densities are found to be in the order of 1018 cm-3 and decay at a rate of 3x1015 electrons/cm3ns. The effect of the laser spot diameter on the shock wave generated in the ablation process of a Zn target has been studied. The induced shock wave has an ellipsoidal shape that approaches a sphere for decreasing spot diameter. A model was developed that approaches the density distribution that facilitates the derivation of the particle velocity field. The method provides quantitative results that are discussed; in particular a comparison with the point explosion theory. The effect of the physical properties of the target on the laser ablation process has been studied. The comparison of the laser ablation of Zn and Ti shows that different laser ablation mechanisms are observed for the same laser settings and surrounding gas. At a laser fluence of 5 J/cm2, phase explosion appears to be the ablation mechanism in case of Zn, while for Ti normal vaporisation seems to be the dominant mechanism. The results show that pulsed digital holographic interferometry is a promising technique to give a physical picture and increase the understanding of the laser ablation process in a time resolved manner.Godkänd; 2009; 20091018 (eyname); DISPUTATION Ämnesområde: Experimentell mekanik/Experimental Mechanics Opponent: Reader in Laser Engineering Bill O’Neill, University of Cambridge, UK Ordförande: Professor Mikael Sjödahl, Luleå tekniska universitet Tid: Fredag den 20 november 2009, kl 10.00 Plats: E 231, Luleå tekniska universitet
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Amer, Mohamed Eynas. "Pulsed laser ablation studied using digital holography /." Luleå : Department of Applied Physics and Mechanical Engineering, Luleå University of Technology, 2009. http://pure.ltu.se/ws/fbspretrieve/3315450.
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Tarabein, Karim A. "Towards the automatic control of laser ablation for surgical applications." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-theses/1325.
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The goal of this thesis is to propose and investigate a method of predicting depth of a laser dissection pulse in soft tissue without acquiring material properties of the tissue target or measuring the laser output. The method proposed is similar to what is used by laser surgical operators today, but uses regression learning to perform on-the fly predictions in place of a skilled laser surgeon. Power of the laser and the ablation depth were recorded for 57 samples and fed into the regression algorithm. Data exclusion was performed using Temperature before laser action as criteria. A linear and logarithmic model was explored using random points from the data post-exclusion, validation RMSE ranged from 135-200 micrometer. A linear and logarithmic model was explored using data points below a moving power threshold and validated with data points above said threshold, validation RMSE ranged from 108-170 micrometer. The t.test performed showed there was not a significant difference between the linear and the logarithmic models' goodness of fit metrics, but it did show there was a significant difference between the model building methods (randomly selected data points, moving power threshold). The method of building a model using lower power levels to predict larger power levels had better goodness of fit metrics than the method of selecting data points at random. In the future, this method could be used to help approximate the laser settings for surgery on a procedural basis, and allow for surgeons to perform at a higher skill level with less training.
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Le, Quang tri. "Ablation laser de la dentine et ses applications medicales." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0559/document.
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Le développement récent, dans le domaine de la santé, de lasers femtoseconde pompés par diode, délivrant des impulsions de forte énergie et utilisés en chirurgie (en particulier en ophtalmologie), nous amene à chercher de nouveaux domaines d’application dans le secteur de la santé. En effet, la durée très brève de l’interaction laser avec la matière (de l’ordre de 10-15s) et les fortes intensités de radiation délivrées, permettent d’envisager une ablation tissulaire rapide avec des effets thermiques négligeables.Ce travail va un triple objectif:- Etudier la capacité d’ablation de l’émail dentaire et de la dentine avec un laser femto seconde,- Mesurer l’accroissement de température généré par l’interaction laser/tissus avec et sans spray d’air + eau, sachant qu’un accroissement de température au delà de 5.5°C engendre des dommages irréversibles (nécrose) du tissu pulpaire.- Mener une étude comparative de l’adhésion des matériaux de restauration composite sur les surfaces préparées par laser versus l’adhésion sur des surfaces dentinaires préparées de façon conventionnelle avec une fraise et une turbineRecent development has led to the commercialization of high power femtosecond lasers, opening a new perspective into the field of laser surgery. Due to the short laser – material interaction time and the very high radiation intensity achieved with this type of laser, the ablation of a wide range of materials can be achieved with negligible thermal effects.The present work aims at- Studying the ablation of dental enamel and dentin by femtosecond laser- Measuring the increase of pulpal temperature generated during the laser treatment without external cooling and with external cooling using an air jet and a combination of the air jet and water irrigation.- Comparing the adhesion of restorative materials to dentin surface treated by the laser and by the conventional drilling method with a burr
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Gil, Villalba Abel. "Single shot ablation of monolayer graphene by spatially shaped femtosecond laser pulses." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD028/document.
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Depuis sa découverte expérimentale en 2004, le graphène a émergé comme un matériau potentiel pour les technologies de nouvelle génération. Le graphène était le premier matériau 2D produit et l’intérêt et qu’il suscite provient de ses remarquables propriétés: il possède d’importants coefficients de mobilité électronique et de conductivité thermique, il est également le matériau le plus solide et léger connu. Pour permettre le développement d’applications à l’ échelle industrielle, des technologies de structuration à l’ échelle submicronique sont nécessaires.Cette thèse se concentre sur l’exploration de l’ablation par laser femtoseconde en tant que technique de structuration rapide et peu coûteuse de structuré graphène obtenu par technique CVD (Chemical Vapor Deposition). L’utilisation d’impulsions laser ultra brèves est a priori intéressante en raison de la capacité des impulsions laser ultra brèves à déposer au sein des matériaux une quantité élevée d’ énergie dans un volume extrêmement confiné.Nous avons réalisé un ensemble d’expériences à partir de faisceaux non-diffractants pour caractériser les paramètres requis pour contrôler l’ablation à l’ échelle sub-micronique. Nous avons déterminé les caractéristiques de l’ablation en régime mono-coup pour le graphène CVD, tels que le seuil d’ablation et la probabilité d’ablation. Pour cela, nous avons développé une nouvelle technique de mesure indépendante du seuil indépendante de la taille de la zone ablatée. Nous avons ainsi pu mettre en évidence un écart par rapport au modèle classique d’ablation, l’effet des différents substrats diélectriques, ainsi que le rôle des joints de grain.Nos résultats montrent que l’ablation mono-coup par impulsion femtoseconde est une technique efficace pour des structures au-delà d’une taille caractéristique de 1 _m, mais en dessous de cette dimension, de nouvelles stratégies d’illuminations se révèlent encore nécessairesSince its isolation in 2004, graphene has emerged has a potential material for next generation technologies.Graphene was the first truly 2D material produced. The interest in this material is due to its outstandingproperties: graphene is the lightest and strongest material known. It has a large electronic mobility andthermal conductivity. To enable the development of technological applications at industrial scale, fast patterningtechniques, operable at sub-micron scale are needed.This thesis focuses on the requirement of a fast, easily reconfigurable, low cost method to pattern graphene.The aim of our research is to determine the possibilities and constraints of ultrafast laser ablation of CVDgraphene at sub-micron scale. Using ultrafast laser to pattern graphene layers is interesting due to the abilityof femtosecond laser pulses to accurately depositing a high energy density in confined regions.We performed a set of experiments using non-diffractive shaped-beams to characterize the parametersrequired to control laser material processing at such small scale. We determined laser patterningcharacteristics on CVD monolayer graphene such as the ablation threshold and the ablation probability. To thisaim, we have developed a novel technique to measure ablation threshold that is independent of the ablated sizeand reported unexpected deviation from the threshold model, we also investigated the influence of differentdielectric substrates and the effect of the presence of graphene grain boundaries. From our experimentalresults we conclude that direct single shot laser patterning is a very effective method to pattern features above 1 µm, but below this dimension, novel illumination strategies are needed
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Torres, Mendieta Rafael Omar. "Synthesis of colloidal nanomaterials through femtosecond laser ablation." Doctoral thesis, Universitat Jaume I, 2016. http://hdl.handle.net/10803/387325.
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La investigación de esta tesis se centra en la producción de nanoestructuras metálicas dentro de aceites orgánicos y nano-ensambles por ablación láser en líquidos para resolver los mayores problemas en su producción por métodos convencionales: poca estabilidad, producción de residuos químicos y reacciones químicas sin control debido a problemas de pureza. En particular, las mayores contribuciones son, la síntesis de nanofluidos basados en nanopartículas de oro que pueden ser utilizados como absorbentes volumétricos de luz e intercambiadores de calor. La fabricación de un nanofluido con una mejora de conductividad térmica de 4,06% sobre un fluido de transferencia de calor comercial, una mezcla eutéctica de óxido de bifenilo y difenilo, y la mejor estabilidad coloidal reportada en la literatura usando estos materiales. Y, por último, la demostración de la reducción parcial de láminas de óxido de grafeno y su decoración con nanopartículas de oro con ligandos libres, en un solo paso.The research conducted during this thesis work is focused on producing metal nanostructures inside organic oils and nano-essambles by Pulsed Laser Ablation in Liquids (PLAL) to solve the biggest issues on their production by conventional approaches: Poor stability, production of chemical waste and uncontrolled chemical reactions due to purity problems. In particular, the biggest contributions achieved on the present work, lies on the experimental demonstration of the synthesis of gold nanoparticles-based aqueous nanofluids that can be used as both volumetric light absorbers and heat exchangers. The fabrication of a nanofluid with a thermal conductivity enhancement of 4.06% over a commercial heat transfer fluid, an eutectic mixture of biphenyl and diphenyl oxide, and the best colloidal stability reported in the literature using these materials. And finally, demonstration of partial reduction of graphene-oxide sheets and its decoration with ligand-free gold nanoparticles, in a single reaction stage avoiding the production of chemical waste.
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Hutchison, Christopher. "High-order harmonic generation in laser ablation plumes." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/40289.
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High harmonic generation (HHG) is a powerful and well established technique to study ultra fast processes in atoms and molecules. Originally HHG was restricted to the study of atomic or small molecular gases. In the last few years the use of laser ablation to create plumes that are suitable media for HHG has gained interest due to is ability to allow almost any solid material to be potentially studied using HHG. Most of this thesis focuses on our advancements in this eld of ablation plume HHG spectroscopy with a small section devoted to our continuation of work focused on controlling electron trajectories in HHG through the use of an orthogonally polarised second harmonic eld. We show how through the use of a rotating target system we have been able to stabilise the ablation process to work at 1 kHz repetition rate. The ablation plumes of some transition metals have previously be shown to exhibit enhancement of particular harmonic orders linked to resonances in the parent ion. We performed investigations into tin and manganese plumes and were able to nd good agreement between the experimental data and a theoretical model. This showed that autoionising states in the ions of these materials were the most likely source of the enhancements. We present our attempts to extend the ablation plume HHG technique to work with soft materials. It was found that graphite plumes were able to produce a very strong harmonic response that is comparable with generation from an argon gas jet. It was discovered that nano particles were present in the plumes and these were mostly likely to cause of the stronger e ciency. Finally we present the rst use of laser ablation plume HHG to study molecules of biological interest. We performed HHG studies on uracil and thymine, a signal was obtained from former but not the latter. Were able to determine that during ablation there was a higher degree of molecular fragmentation from thymine molecules compared to uracil.
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Atherton, David Patrick. "Time and spatially resolved laser induced ablation plumes." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1447620.
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El-Astal, Ali Hamed Hussein. "Spectroscopic studies of YBCO laser ablation plasma plumes." Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282146.
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Lade, Robert James. "Pulsed ultraviolet laser ablation of carbon containing targets." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302156.
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Rebegea, Simina Aurelia. "Nanosecond laser ablation of thin film material libraries." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8555/.
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This work offers a novel approach to the investigation of material response in nanosecond laser ablation, by irradiating a thin film material library (having small variations in the chemical composition) with a beam of constant parameters. The method could be used as a way to assess the machining capability of a wide range of materials. Single-pulse craters were obtained with nanosecond infrared lasers (Nd:YAG, 1064 nm, 30-55 ns). The influence of reflectivity, thermal properties, surface and sub-surface morphology of the target material are correlated with the variations in crater geometry, morphology and the amount of removed material. Pure Cu, Al and Ni films and their binaries were studied to establish typical craters and to illustrate how a change in the parent material affects the workpiece after irradiation respectively. The study of the ternary compositional gradients irradiated with constant laser parameters extends upon these findings, and represents, to this point, the first work of its type. A second film (Cu-Al-Zr) was analysed to confirm that the variations in crater geometry and morphology were not material-specific. It is also shown that nanosecond laser ablation of thin films (with minimal thermal damage to the substrate) can be achieved with a typical Gaussian beam.
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Déziel, Jean-Luc. "Ablation laser et croissance de réseaux de surface." Master's thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26377.
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Tableau d'honneur de la Faculté des études supérieures et postdorales, 2015-2016La formation des réseaux de surface, ou laser-induced periodic surface structures (LIPSSs), à l’aide d’une source laser pulsée est étudiée avec la théorie de Sipe-Drude, d’abord analytiquement, puis avec la méthode numérique finite-difference time-domain (FDTD). Les LIPSSs sont des structures nanométriques sinusoïdales pouvant être catégorisées selon leur orientation par rapport à la direction de polarisation du laser incident et en fonction de leur période Λ par rapport à la longueur d’onde du laser λ. Avec la méthode FDTD, nous trouvons, dans une région de l’espace paramétrique jamais explorée, qu’une impulsion laser polarisée linéairement peut interagir avec une surface rugueuse de façon à faire croître des structures bidimensionnelles ayant une période de Λ ∼ λ dans les orientations parallèle et orthogonale à la direction de polarisation. Par contre, ce modèle ne peut expliquer la forte organisation et régularité des structures dans le domaine spatial, tel qu’observé dans les expériences. Permettre l’auto-organisation des structures avec un mécanisme de rétroaction inter-impulsion est une solution possible afin de simuler la croissance de LIPSSs fortement organisés d’une impulsion laser à la suivante. Récemment proposée, cette méthode utilise un processus d’ablation non physique afin de tenir compte qualitativement de l’éjection de matériau entre deux impulsions laser. Ce nouveau modèle peut reproduire une grande variété de LIPSSs avec une forte régularité spatiale, mais échoue toujours à simuler la croissance de l’amplitude de certains types de structures. Nous suggérons que ces structures restantes peuvent croître en considérant un mécanisme inverse, l’expansion. En combinant ablation et expansion, nous avons simulé avec succès un plus grand nombre de types de LIPSSs.
The formation of laser-induced periodic surface structures (LIPSSs) using pulsed laser source is studied on the basis of the Sipe-Drude theory solved, first analytically, then with a finitedifference time-domain (FDTD) scheme. LIPSSs consist of wavy nanometric structures and can be categorized depending on their orientation with respect to the incident laser polarization and their periodicity Λ with respect to the incident laser wavelength λ. With our FDTD solver, we find, in as yet unexplored regions of parameter space, that a linearly polarized laser pulse can interact with a rough surface such that bidimensional structures could grow with both parallel and perpendicular periodicity of Λ ∼ λ. However, this theory cannot predict the strong organization and regularity in the space domain, as observed in the experiments. Allowing self-organization in the model with an interpulse feedback mechanism is a possible solution to simulate the growth of strongly organized LIPSSs from one laser pulse to the next. This recently proposed method uses a non-physical ablation process to qualitatively account for material removal between two laser pulses. This new model can reproduce a large variety of LIPSSs with a strong spatial regularity, but still fails to simulate amplitude growth of some of the structures. We suggest that those remaining structures can grow by considering an inverse mechanism, an expansion process. By combining ablation and expansion mechanisms, we have successfully simulated the growth of a large class of LIPSSs.
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Ahwal, Fadi Odeh. "Robotic assisted laser bone ablation for orthopaedic surgery." Thesis, University of Hull, 2006. http://hydra.hull.ac.uk/resources/hull:15104.
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The needs for better quality patient care and improved surgical procedures drive the development of new surgical tools and techniques that can augment the human surgeon capabilities. Over the past decade or so there have been significant advances in the design and development of computer assisted image guided surgery systems that can potentially perform complex tasks with high dexterity, speed and flexibility. The aim of this research work is to investigate various aspects in the design of a new computer assisted surgical tool capable of sawing, drilling and sculpturing of bone in support of image guided surgery that aims to reduce invasiveness, minimise blood loss and improve surgical outcome. The research of this thesis focuses on the design of an active positioning system (robotic end-effector) that uses a laser to cut bone to replace some of the currently available tools. This thesis starts by reviewing medical lasers and laser delivery systems, and discussing the effects of different lasers and lasers' parameters on tissue ablation time, rate and depth. It then defines criterion for the selection of the most appropriate laser and laser delivery system for bone cutting, drilling and sculpturing applications. Secondly, the thesis presents a unique design of a robotic laser end-effector. This end-effector is designed to provide accurate laser guidance for precise surgical performance (tissue ablation). This design is supported by an in-depth forward and inverse kinematic analysis to determine the end-effector workspace, resolution, positioning accuracy and manipulation flexibility. Thirdly and perhaps most importantly, the thesis presents two innovative laser feedback techniques, developed by the author, to determine the laser ablation depth and rate in real time during laser tissue interaction. These techniques are presented with complete analysis and supported by real time feedback examples. The techniques showed high measurement accuracy and reliability. Finally the thesis reviews the overall system performance supported by an error analysis model to determine the effects of different errors on the manipulation and positioning performance of the laser end-effector. It also presents some possible end-effector design modifications, alternative feedback techniques and suggestions for future work.
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Farjad, Shervin. "Analysis of metal vapour generation by laser ablation." Access electronically, 2007. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20080325.110711/index.html.
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Amer, Eynas. "Pulsed laser ablation studied using digital holographic interferometry." Licentiate thesis, Luleå : Luleå University of Technology, 2008. http://epubl.ltu.se/1402-1757/2008/55/.
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Talisa, Noah Brodzik. "Laser-Induced Damage and Ablation of Dielectrics with Few-Cycle Laser Pulses." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1609243476481238.
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Hao, Liu. "Pulsed laser ablation and laser-induced plasma diagnosis by optical emission spectroscopy." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.702119.
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Fundamental aspects of the laser ablation of solid targets using nanosecond pulses with irradiances in the range ≈ 1-30 OW /cm2 have been investigated theoretically, modelled using a simulation code, and explored experimentally by time-gated, spatially and spectrally resolved imaging of the optical emission that accompanies the ablation plume. During the earliest stages of the laser-target interaction, the target surface temperature rises rapidly and electrons are ejected by both thermionic and photo-emission. These electrons absorb energy from the · laser pulse by strong electron-photon coupling, leading to formation of an embryonic plasma which continues to gain energy via photoionization and, particularly, inverse bremsstrahlung (IB) absorption. The target is further heated by the hot plasma and may reach temperatures of several thousand Kelvin, approaching its critical point, and undergo an explosive phase transition to the supercritical fluid. Such a super-hot target surface emits an abundance of electrons, neutrals and ions. The present work shows that the electron yield following 532 nm PLA of a Si target is significantly higher than that produced using 1064 nm pulses of same irradiance. The fastest electrons emerge at the leading edge of the plasma plume, creating an electric field gradient with respect to the net positively charged body of the plume. This has the effect of accelerating ions in the plume, to extents that ·depend on their charge state. Emissions from any given charge state show identical spatial distributions in the time-gated images. The most highly charged ions (e.g. SiIV ions in the case of PLA of Si in vacuum) exhibit velocities of ~ 1 00 km/s. Experiment and simulation show that plasma produced by 1064 nm excitation is hotter and expands faster than that formed by 532 nm PLA - a result that can be attributed to the stronger IB absorption of the longer wavelength radiation. A new and improved method for determining local electron densities (Ne) and temperatures (Te) in laser induced plasmas is introduced. The model relies on fitting Stark broadened line shapes but, in contrast to most rival approaches, makes no preassumption regarding local thermodynamic equilibrium. The method is used to determine temporally and spatially evolving Ne and Te distributions in plumes arising from PLA of Si and SiC targets, as functions of irradiance, excitation wavelength and ambient pressure. We also demonstrate how Ne and Te values determined by fitting lines associated with one spectral carrier allow derivation of (hitherto unknown) Stark parameters for transitions involving other carriers. A clear shock front is observed following PLA of Si in background Ar pressures ~0.2 Torr, even as early as 40 ns. Strong collisions between highly charged ions in the plume and the surround gas are seen to introduce another level of complexity (e.g. ionization, recombination, charge transfer, etc.) within and beyond the shock front in the plume.
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Lo, Ka Ming. "Laser ablation of aqueous samples at 193-nm : mechanism and applications." HKBU Institutional Repository, 2000. http://repository.hkbu.edu.hk/etd_ra/224.
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Carvalho, Luisa. "Etude de l’interaction laser surface pour le développement de procédé de décontamination de surfaces métalliques avec fissures micrométriques par ablation laser." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS462/document.
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En réponse aux opérations futures d’assainissement des installations nucléaires, la décontamination par ablation laser de surfaces métalliques apparait comme une technique adaptée aux enjeux sanitaires et économiques actuels. L’objectif est d’ablater par un faisceau laser de façon préférentielle la surface oxydée contenant des radioéléments et de récupérer les éléments vaporisés pour pouvoir isoler la contamination radioactive en vue de son stockage. A la différence des techniques existantes comme le ponçage ou le traitement chimique par gel ou mousse, le traitement laser permet de ne pas produire de déchets secondaires et de pouvoir être effectué à distance en diminuant considérablement la dose reçue par les opérateurs. Le retour d’expérience a montré la nécessité d’optimiser le procédé en vue de limiter la contamination résiduelle. Les phénomènes responsables de cette limitation et identifiés dans la littérature sont la pénétration des contaminants dans le substrat métallique par effet thermiques induits par laser et le piégeage des radionucléides dans des défauts de surface micrométriques. Les travaux de thèse auront donc comme objectifs d’étudier et d’optimiser la décontamination de surfaces métalliques avec des couches d’oxydes contaminées de façon volumique avec un simulant de radionucléide (Eu) par ablation laser, en vue dans un second temps d’améliorer de l’efficacité de la technique au niveau des défauts surfaciques. Enfin, au-delà de la démarche expérimentale, cette thèse vise à contribuer à la compréhension de l’interaction laser/matière dans le cadre de notre étude via la simulation du chauffage de surface métallique par modélisation multi physiqueThe preparation of future decommissioning of nuclear installations is currently facing economical and sanitary challenges. The metallic-surface decontamination by laser ablation is here studied as an appropriate and efficient technique, which involves ejection of surface contamination by subjecting the surface to high-energy laser pulses followed by subsequent trapping to avoid environmental dispersion. This process has many advantages such as the minimization of secondary waste, no production of effluents and the reduction of the exposition of workers by the automation of the process. Previous studies highlighted the need to optimize the process in order to limit the residual contamination. The identified reasons for this limitation are the contamination penetration into the metal bulk induced by the laser treatment and the entrapment of the radionuclides in surface defects like micro cracks. The aim of this work is the study and the cleaning optimization of metallic surfaces with an oxide layer implemented with a non-radioactive contamination (Eu). Secondly, the cleaning efficiency has been improved in case of damaged surfaces with defects such as cracks. Beyond an experimental study, The ablation of a metallic substrate with a submicrometric oxide layer is currently modeled using a numerical and multiphysics approach in order to determine the mechanism involved during the process
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Rajendran, Saravanakanthan, Michael Keidar, Iain D. Boyd, Charles H. Jones, and Brian Mork. "MODELING OF THE PLASMA FORMATION DUE TO LASER IRRADIENCE DURING DIRECTED-ENERGY TESTING." International Foundation for Telemetering, 2007. http://hdl.handle.net/10150/604489.
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ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, NevadaReal-time transmission of airborne images to a ground station is highly desirable in many telemetering applications. Such transmission is often through an error prone, time varying wireless channel, possibly under jamming conditions. Hence, a fast, efficient, scalable, and error resilient image compression scheme is vital to realize the full potential of airborne reconnaisance. JPEG2000, the current international standard for image compression, offers most of these features. However, the computational complexity of JPEG2000 limits its use in some applications. Thus, we present a scalable low complexity coder (SLCC) that possesses many desirable features of JPEG2000, yet having high throughput. Continuous radio-wave telemetry is required during planned tests of directed-energy weapons systems in order to characterize in situ the effects of laser irradiation on different target materials. Unfortunately, the incident radiation can cause disruption of the radio signal during the directed-energy testing. Several phenomena associated with directed-energy impact can lead to communication path losses, such as ablation, charged particle emission, charring, and chemical changes in the target materials. Directed-energy impact on the target material leads to target heating and consequent ablation. In this paper, a numerical model has been developed to describe the laser induced ablation of metal surfaces. The model describes the absorption of the laser energy by the metal and the resulting temperature rise in the surface. This temperature rise then induces ablation of the target material. Results for an aluminum target irradiated with a KrF laser were obtained. Temperature profiles in the target material and surface temperature changes are presented along with the ablation rate as a function of time as the aluminum target is irradiated. This report presents results for cases when laser energy absorption by the plasma plume created above the surface is not significant.
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Sasaki, K., S. Matsui, H. Ito, and K. Kadota. "Dynamics of laser-ablation Ti plasmas studied by laser-induced fluorescence imaging spectroscopy." American Institute of Physics, 2002. http://hdl.handle.net/2237/7045.
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Capewell, Dale L. Goodwin David G. Goodwin David G. "Planar laser induced fluorescence imaging and Monte Carlo simulations of pulsed laser ablation /." Diss., Pasadena, Calif. : California Institute of Technology, 1997. http://resolver.caltech.edu/CaltechETD:etd-01102008-095243.
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Asogan, Dhinesh. "A non-contact laser ablation cell for mass spectrometry." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/11014.
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A common analytical problem in applying LA sampling concerns dealing with large planar samples, e.g. gel plates, Si wafers, tissue sections or geological samples. As the current state of the art stands, there are two solutions to this problem: either sub-sample the substrate or build a custom cell. Both have their inherent drawbacks. With sub-sampling, the main issue is to ensure that a representative is sample taken to correctly determine the analytes of interest. Constructing custom cells can be time consuming, even for research groups that are experienced or skilled, as they have to be validated before data can be published. There are various published designs and ideas that attempt to deal with the issue of large samples, all of which ultimately enclose the sample in a box. The work presented in this thesis shows a viable alternative to enclosed sampling chambers. The non-contact cell is an open cell that uses novel gas dynamics to remove the necessity for an enclosed box and, therefore, enables samples of any arbitrary size to be sampled. The upper size limit of a sample is set by the travel of the XY stages on the laser ablation system, not the dimensions of the ablation cell.
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Borowiec, Andrzej Haugen Harold Kristen. "Ablation and micromachining of INP with femtosecond laser pulses /." *McMaster only, 2004.
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Garrelie, Florence. "Ablation laser femtoseconde pour le dépôt de couches minces." Habilitation à diriger des recherches, Université Jean Monnet - Saint-Etienne, 2008. http://tel.archives-ouvertes.fr/tel-00356315.
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Ce mémoire concerne l'élaboration de couches minces par ablation laser femtoseconde (Pulsed Laser Deposition, PLD) et la caractérisation du panache plasma. Les résultats obtenus pour le dépôt de couches minces de Diamond-Like Carbon (DLC) sont présentés avec l'objectif de déposer des couches à grande dureté et faible coefficient de frottement, avec de bonnes propriétés d'adhérence sur divers substrats d'intérêt biomédical. Des couches minces ont pu être déposées avec succès sur une tête fémorale de prothèse de hanche. Les propriétés des DLC élaborés par PLD femtoseconde et nanoseconde PLD ont été comparées au travers des propriétés optiques des films et d'une caractérisation du plasma.Des nanoparticules ont été déposées par PLD femtoseconde, et incluses dans une matrice DLC. Des films de DLC dopés au nickel ou tantale (en raison de leur différente affinité chimique avec le carbone) ont été synthétisés. Deux différentes phases cristallines sont obtenues dans le cas du DLC dope Ta, avec la présence surprenante d'une phase métastable β-Ta, qui est corrélée aux propriétés du plasma. La présence de carbure de tantale est également mise en évidence sur les bords des clusters de tantale.
Les films de DLC pur et de DLC dopé aux métaux sont caractérisés pour l'application aux électrodes pour biocapteurs, avec une sensibilité élevée et une faible limite de détection. L'optimisation avec l'incorporation d'un autre dopant, tel que le bore est discutée.
La possibilité d'utiliser ces couches de DLC dopé au bore pour des capteurs thermiques et nanocalorimétriques est étudiée dans le cadre d'un projet ANR. Les thermomètres à base de DLC avec un fort TCR (Coefficient de Température de Resistance) sont intégrés dans des structures suspendues, et montrent de bonnes propriétés.
Dans la dernière partie de ce mémoire, les perspectives envisagées pour ce travail sont présentées, avec l'introduction d'une mise en forme temporelle de l'impulsion laser femtoseconde et d'une boucle adaptative d'optimisation. Ces premiers travaux mettent bien en évidence les potentialités de cette technique, pour le dépôt couches minces et la synthèse de nanoparticules, permettant un contrôle de la nature et de l'énergie cinétique des particules du plasma. La suite de ce travail envisage donc de mieux comprendre les effets d'une mise en forme temporelle de l'impulsion laser femtoseconde sur les propriétés des produits d'ablation et donc des couches minces élaborées.