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Dissertations / Theses on the topic 'Plasma sources'
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1
Stevenson, Paul. "Novel plasma sources for the plasma opening switch." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/13632.
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The plasma opening switch (POS) is used in pulsed power systems where a fast opening and very high current switch is required. Plasma is injected into the switch, which carries a large conduction current before it opens in a process that lasts for a few nanoseconds and transfers the current to a parallel-connected load The conduction and opening times of the switch are dependent on the plasma parameters such as distribution, speed, temperature and species, which are all determined by the plasma source. This thesis begins with a description of the POS, with its conduction and opening mechanisms and the techniques of plasma generation all being considered, before it concentrates on the simple and inexpensive carbon gun. Plasma is normally produced by a pulsed discharge that evolves plasma from the evaporation and ionisation of a carbon based insulator. The first prototype carbon gun discussed in the thesis uses a classical coaxial arrangement that successfully produces dense, fast and hot plasma, although this is only capable of filling a small region with plasma. A number of plasma diagnostic techniques are described, before details are provided of the electrical probes that were used to characterise the plasma In a large POS a well-distributed plasma is obtained by combining a large number of guns in a complex and large system. This restncts the compactness of the POS resulting in a problem for any future commercial applications. A succession of developments to the prototype gun has led to a novel ring-shaped version that produces a much improved distribution of plasma, without the need for additional guns. In this, a pulsed discharge is initiated at a single point and the self-generated magnetic field forces the discharge to spread and to travel around the gun, whilst continuously ejecting plasma into the POS. The ideas and theories that explain how a discharge can be forced to move are described, together with details of the prototype designs. Results are given to confirm the operation of the gun, using high speed photography and electrical probes.
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Déchard, Jérémy. "Sources térahertz produites par des impulsions laser ultra-intenses." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS358/document.
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Les impulsions laser femtosecondes produisent des phénomènes non linéaires extrêmes dans la matière, conduisant à une forte émission de rayonnement secondaire qui couvre un domaine en fréquence allant du terahertz (THz) aux rayons X et gamma. De nombreuses applications utilisent la bande de fréquences terahertz (0.1-100 THz) afin de sonder la matière (spectroscopie, médecine, science des matériaux). Ce travail est dédié à l'étude théorique et numérique du rayonnement THz généré par interaction laser-plasma. Comparé aux techniques conventionnelles, ces impulsions laser permettent de créer des sources THz particulièrement énergétiques et à large bande. Notre objectif a donc été d'étudier ces régimes d'interaction relativiste, encore peu explorés, afin d'optimiser l'efficacité de conversion du laser vers les fréquences THz. L'étude de l'interaction laser-gaz en régime classique nous permet, d'abord, de valider un modèle de propagation unidirectionnelle prenant en compte la génération d'impulsion THz et de le comparer à la solution exacte des équations de Maxwell. Ensuite, en augmentant l'intensité laser au-delà du seuil relativiste, nous simulons à l'aide d'un code PIC une onde plasma non linéaire dans le sillage du laser, accélérant ainsi des électrons à plusieurs centaines de MeV. Nous montrons que le mécanisme standard des photocourrants est dominé par le rayonnement de transition cohérent induit par les électrons accélérés dans l'onde de sillage. La robustesse de ce rayonnement est ensuite observée grâce à une étude paramétrique faisant varier la densité du plasma sur plusieurs ordres de grandeur. Nous démontrons également la pertinence des grandes longueurs d'ondes laser qui sont à même de déclencher une forte pression d'ionisation, ce qui augmente la force pondéromotrice du laser. Enfin, les rayonnements THz émis à partir d'interactions laser-solide sont examinés dans le contexte de cibles ultra fine, mettant en lumière les différents processus impliquésFemtosecond laser pulses trigger extreme nonlinear events inmatter, leading to intense secondary radiations spanning the frequency rangesfrom terahertz (THz) to X and gamma-rays.This work is dedicated to the theoretical and numerical study of THz radiationgenerated by laser-driven plasmas. Despite the inherent difficulty in accessingthe THz spectral window (0.1-100 THz), many coming applications use theability of THz frequencies to probe matter (spectroscopy, medicine, materialscience). Laser-driven THz sources appear well-suited to provide simultaneouslyan energetic and broadband signal compared to other conventional devices. Ourgoal is to investigate previously little explored interaction regimes in orderto optimize the laser-to-THz conversion efficiency.Starting from classical interactions in gases, we validate a unidirectionalpropagation model accounting for THz pulse generation, which we compare to theexact solution of Maxwell's equations. We next increase the laser intensityabove the relativistic threshold in order to trigger a nonlinear plasma wave inthe laser wake, accelerating electrons to a few hundreds of MeV. We show thatthe standard photocurrent mechanisms is overtaken by coherent transitionradiation induced by wakefield-accelerated electron bunch. Next, successivestudies reveal the robustness of this latter process over a wide range of plasmaparameters. We also demonstrate the relevance of long laser wavelengths inaugmenting THz pulse generation through the ionization-induced pressure thatincreases the laser ponderomotive force. Finally, THz emission from laser-solidinteraction is examined in the context of ultra-thin targets, shedding light onthe different processes involved
3
Hansson, Björn. "Laser-Plasma Sources for Extreme-Ultraviolet Lithography." Doctoral thesis, KTH, Physics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3677.
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This thesis describes the development and characterizationof a liquidxenon- jet laser-plasma source forextreme-ultraviolet (EUV) radiation. It is shown how thissource may be suitable for production-scale EUV lithography(EUVL).
EUVL is one of the main candidates to succeeddeep-ultraviolet (DUV) lithography for large-scalemanufacturing of integrated circuits (IC). However, a majorobstacle towards the realization of EUVL is the currentunavailability of a source meeting the tough requirements onespecially power and cleanliness for operation in an EUVLstepper. The liquid-xenon-jet laser-plasma concept has keyadvantages that may make it suitable for EUVL since, e.g., itsplasma consists only of the inert noble gas xenon and since theliquidjet target technology enables plasma operation at largedistances from the source-hardware thereby reducing sputteringand to allowing for high-power operation.
At the beginning of the work described in this thesis, aspatial instability of the liquid-xenon-jet made stableoperation of a plasma at practical distances from the nozzleorifice dicult. However, an invention of a stabilization methodbased on applying localized heating to the tip of thejet-forming nozzle, resulted in stable jet operation. Thelongitudinal droplet stability of a liquid-droplet laser-plasmasource has also been investigated and improved.
Continuous improvements of especially the laser-power toEUV-radiation conversion eciency (CE) and the stability oflaser-plasma operation at large distances (several centimeter)from the nozzle are reported for the liquidxenon- jet laserplasma source. Furthermore, this source is characterizedregarding many parameters relevant for EUVL operationincluding, ion emission from the plasma and related sputteringof nearby components, source size and shape, therepetition-rate limit of the source and non-EUV emission fromthe plasma.
Although the main focus of the thesis has been thedevelopment and characterization of a liquid-xenon-jetlaser-plasma source for production-scale EUVL, the source mayalso be suitable for small field applications that benefit fromthe high potential brightness of the source. A method to scanthe plasma and thus minimize the photon losses whilemaintaining the object plane uniformity was developed.Furthermore, the first operation of a liquidtin- jet laserplasma is reported. Quantitative EUV flux measurements yieldrecord CE, but quantitative contamination measurements alsoindicate that a liquid-tin-jet laser plasma is not likely to beapplicable as a source for EUVL.
4
Mynors, Diane Julie. "Modelling of volume ion sources." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333192.
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Gallacher, Jordan G. "Relativistic electrons and radiation from intense laser-plasma sources." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=15481.
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Gerst, Jan Dennis. "Investigation of magnetized radio frequency plasma sources for electric space propulsion." Phd thesis, Université d'Orléans, 2013. http://tel.archives-ouvertes.fr/tel-00977801.
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The PEGASES thruster (Plasma Propulsion with Electronegative Gases) is a novel type of electric thruster for space propulsion. It uses negative and positive ions produced by an inductively coupled radio frequency discharge to create the thrust by electrostatically accelerating the ions through a set of grids. A magnetic filter is used to increase the amount of negative ions in the cavity of the thruster. The PEGASES thruster is not only a source to create a strongly negative ion plasma or even an ion-ion plasma but it can also be used as a classical ion thruster. This means that a plasma is created and only the positive ions are extracted and accelerated making it necessary to neutralize the plasma behind the acceleration stage like in other ion thrusters. The performances of the PEGASES thruster have been investigated mainly in xenon in order to compare the obtained results with RIT-type ion thrusters. The thruster has been investigated with the help of a variety of probes such as a Langmuir probe, a planar probe, a capacitive probe and a RPA (Retarding Potential Analyzer). In addition, an ExB probe has been developed to measure the velocity of the ions leaving the thruster and to differentiate between the ion species present in the plasma.
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Fritzler, Sven. "Particle sources with high-intensity lasers : a tool for plasma diagnostics and an innovative source for applications." Palaiseau, Ecole polytechnique, 2003. http://www.theses.fr/2003EPXX0056.
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Baële, Pierre. "Étude des sources plasma micro-onde à structure coaxiale pour la conception amont d'applicateurs à transformateur d'impédance intégré. Influence de la pression, de la géométrie et de la fréquence d'excitation." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI088/document.
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Le travail effectué dans le cadre de cette thèse porte sur l’étude des plasmas magnétisés et nonmagnétisés produits par des structures coaxiales qui font office à la fois de propagateur d’onde et de coupleur à impédance adaptée au plasma, mais aussi de sonde d’investigation et de caractérisation de la décharge. Une attention particulière est accordée à l’efficacité de couplage entre l’onde électromagnétique et la décharge et de production d’espèces, et ce pour différentes conditions opératoires : fréquence d’excitation (352 et 2450 MHz),configuration magnétique, géométrie de l’applicateur. L’analyse quantitative et comparative présentée dans ce travail s’appuie aussi bien sur une approche expérimentale que théorique. Les modèles analytiques développés etla simulation électromagnétique réalisée permettent d’extraire à partir des mesures expérimentales, d’une partl ’impédance du plasma décorrélée de celle de la structure de propagation de l’onde, et d’autre part, l’absorption globale et locale de l’onde. Du point de vue expérimental, des techniques et méthodes appropriées ont donc été développées et mises en oeuvre comme, par exemple la méthode de changement de plan d’impédance, ou encore l’auto-interférométrie. L’étude paramétrique, menée sur un domaine de pression étendu sur plusieurs décades(10-4 – 10 Torr) et pour une gamme de puissances allant de un à plusieurs centaines de watts, a permis une investigation minutieuse du type de couplage (capacitif, inductif, résistif) qui est fortement dépendant des caractéristiques de la décharge et donc des paramètres opératoires. Leur mise en corrélation, associée à l’analyse des modes de propagation dans un plasma magnétisé, a permis de localiser avec plus de précision les zones de couplage et d’identifier les principaux mécanismes d’absorption de l’onde mis en jeu. Les principaux résultats obtenus confirment une meilleure efficacité de production d’espèces chargées à une fréquence plus élevée (2450MHz), et la présence d’une population d’électrons chauds plus conséquente ainsi qu’une extension spatiale du plasma lorsque la fréquence est plus faible (352 MHz). Comme la technologie 352 MHz à état solide est plus avantageuse du point de vue du coût des composants, comparée à 2450 MHz, elle pourrait s’avérer intéressante pour des procédés visant la production d’espèces chimiquement actives. Toutefois, le couplage, peu efficace, de type capacitif induit par la diminution de la fréquence, requiert une attention accrue au niveau de la configuration du coupleur. Pour le développement en amont des coupleurs, les résultats issus de ce travail de thèse et les modèles analytiques développés devraient constituer un outil déterminant dans la conception de sources plasma micro-onde performantesThe work done within the framework of this thesis focuses on the study of magnetized and nonmagnetizedplasmas produced by coaxial structures that serve both as wave propagator and as plasma matchedimpedance coupler but also as investigation and characterization probe of the discharge. Special attention isgiven to the efficiency of coupling between the electromagnetic wave and the discharge and of speciesproduction, for different operating conditions: excitation frequency (352 and 2450 MHz), magnetic configurationand geometry of the applicator. Quantitative and comparative analysis presented in this work is based both on anexperimental and a theoretical approach. Developed analytical models and conducted electromagnetic simulationare set in connection with the experimental measurements in order to determine, on the one hand, the plasmaimpedance de-embedded of the wave propagation structure and, on the other hand, the global and localabsorption of the wave. From the experimental point of view, appropriate techniques and methods have thereforebeen developed and implemented such as, for example, the impedance plane shift method, or autointerferometry.The parametric study, conducted on a pressure range extended over several decades (10-4 - 10Torr) and power ratings from one to several hundred watts, led to a thorough investigation of the coupling type(capacitive, inductive, resistive ) which is highly dependent on the discharge characteristics and thus of theoperating parameters. Their correlation, combined with the analysis of propagation modes in a magnetizedplasma, has helped locate more accurately the areas of coupling and to identify the main power absorptionmechanisms involved. The main results obtained for the two frequencies confirm a better production efficiencyof charged species at a higher frequency (2450 MHz), the presence of a more substantial hot electron populationand a spatial expansion of the plasma when the frequency is low (352 MHz). As the solid state 352 MHztechnology is more advantageous compared to that at 2450 MHz from the viewpoint of the cost of thecomponents, it could be interesting for processes aiming to produce active chemical species. However itsinefficient coupling, of capacitive type induced by frequency reduction, requires an increased attention at thelevel of coupler configuration. For upstream development of couplers, the analytical models and theexperimental results obtained in this thesis should be a key tool in the design of high-performance microwaveplasma sources
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Möller, Cecilia. "High Power Microwave Sources : design and experiments." Licentiate thesis, KTH, Rymd- och plasmafysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-34072.
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High-Power Microwaves (HPM) can be used to intentionally disturb or destroy electronic equipment at a distance by inducing high voltages and currents. This thesis presents results from experiments with a narrow band HPM source, the vircator. The high voltages needed to generate HPM puts the vircator under great stress, especially the electrode materials. Several electrode materials have been tested for endurance and their influence on the characteristics of the microwave pulse. With the proper materials the shot-to-shot variations are small and the geometry can be optimized in terms of e.g. output power or frequency content. Experiments with a resonant cavity added to the vircator geometry showed that with proper tuning of the cavity, the frequency content of the microwave radiation is very narrow banded and the highest radiated fields are registred. Since HPM pulses are very short and have high field strengths, special field probes are needed. An HPM pulse may shift in frequency during the pulse so it is very important to be able to compensate for the frequency dependence of the entire measurement system. The development and use of a far-field measurement system is described.QC 20110616
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Wetzel, William C. "Overcoming interferences in plasma source mass spectrometry alternative ionization sources, novel correction methods, and new instrumentation /." [Bloomington, Ind.] : Indiana University, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3223057.
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Thesis (Ph. D.)--Indiana University, Dept. of Chemistry, 2006."Title from dissertation home page (viewed June 28, 2007)." Source: Dissertation Abstracts International, Volume: 67-06, Section: B, page: 3109. Adviser: Gary M. Hieftje.
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Debus, Alexander. "Brilliant radiation sources by laser-plasma accelerators and optical undulators." Forschungszentrum Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-91303.
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This thesis investigates the use of high-power lasers for synchrotron radiation sources with high brilliance, from the EUV to the hard X-ray spectral range. Hereby lasers accelerate electrons by laser-wakefield acceleration (LWFA), act as optical undulators, or both. Experimental evidence shows for the first time that LWFA electron bunches are shorter than the driving laser and have a length scale comparable to the plasma wavelength. Furthermore, a first proof of principle experiment demonstrates that LWFA electrons can be exploited to generate undulator radiation.
Building upon these experimental findings, as well as extensive numerical simulations of Thomson scattering, the theoretical foundations of a novel interaction geometry for laser-matter interaction are developed. This new method is very general and when tailored towards relativistically moving targets not being limited by the focusability (Rayleigh length) of the laser, while it does not require a waveguide.
In a theoretical investigation of Thomson scattering, the optical analogue of undulator radiation, the limits of Thomson sources in scaling towards higher peak brilliances are highlighted. This leads to a novel method for generating brilliant, highly tunable X-ray sources, which is highly energy efficient by circumventing the laser Rayleigh limit through a novel traveling-wave Thomson scattering (TWTS) geometry. This new method suggests increases in X-ray photon yields of 2-3 orders of magnitudes using existing lasers and a way towards efficient, optical undulators to drive a free-electron laser.
The results presented here extend far beyond the scope of this work. The possibility to use lasers as particle accelerators, as well as optical undulators, leads to very compact and energy efficient synchrotron sources. The resulting monoenergetic radiation of high brilliance in a range from extreme ultraviolet (EUV) to hard X-ray radiation is of fundamental importance for basic research, medical applications, material and life sciences and is going to significantly contribute to a new generation of radiation sources and free-electron lasers (FELs).
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Cipiccia, Silvia. "Compact gamma-ray sources based on laser-plasma wakefield accelerator." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23936.
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Laser-plasma wakefield accelerator (LWFA) is a promising novel technology that is introducing miniaturization to the accelerator world: the unprecedented gradient of acceleration shrinks the accelerator down to table-top size. Moreover, the LWFA comes with an embedded light source: electrons, while accelerating, undergo betatron oscillatory motion that results in synchrotron radiation emitted in a narrow cone along the direction of propagation. In this thesis we study theoretically and we prove experimentally a new regime of betatron oscillation that occurs when electrons experience the electromagnetic field of the laser during acceleration and oscillate resonantly at the laser frequency or its sub-harmonics. The signature of the harmonically resonant betatron (HRB) regime is a large oscillation amplitude and consequently prolific emission of high energy photons up to the MeV range. The HRB source has unique properties: very short pulse length (~10 fs), small source size (few microns), high peak brightness of the order of 1023 photons/s mm2 mrad2 0.1% B.W., which is comparable with a third generation light source. These properties make the source particularly appealing for the life sciences and medical and security applications. As a part of a future applications project, we give the scaling of the photon energy as a function of laser intensity and plasma density, which could extend toward tens of MeV. The thesis also investigates another gamma-ray source that utilises beams from the LWFA: bremsstrahlung radiation from high energy electrons interacting with metal targets. We study the electron beam and target parameters to optimize the emission process and the gamma-ray beam properties to match potential application requirements, such as radioisotope generation via photonuclear process. The results of a proof of concept experiment are presented and compared with simulations. Finally, we investigate numerically the possibility of generating a converging gamma ray beam based on the bremsstrahlung process. The results are encouraging, and the potential impact of a compact converging gamma-ray beam source is discussed with particular attention to medical applications in cancer treatment.
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Labrecque, Francis. "Development of radiation resistant plasma sources for rare isotopes production." Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/29103/29103.pdf.
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Fletcher, Julian Hooton. "Soft X-ray contact microscopy using laser generated plasma sources." Thesis, University of Oxford, 1993. http://ora.ox.ac.uk/objects/uuid:444fa0f3-d9b7-40ff-a8e0-1e4fd5ce03c5.
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The ultimate objective of this project was to develop a small, transportable X-ray microscope which would be able to view a wide range of biological specimens without the need for any type of sample preparation at a resolution greater than that obtainable by conventional light microscopy (ie. about 250nm). Of the various possible implementations of X-ray microscopy currently being investigated, contact microscopy was chosen as being the most suitable for the development of such a small-scale instrument, while at the same time minimizing the effects on image quality of radiation damage to the biological specimen. The requirement for a high brightness pulsed X-ray source of less than 50ns duration for illumination of the specimen was met by the production of laser generated plasmas. These were formed by focusing a 2.2J KrF laser beam, of wavelength 248nm and duration 20ns, onto the surface of one of a number of different target materials. In order to obtain the large intensities required for the production of a sufficiently high temperature plasma, a doubly pre-ionized, discharge-pumped amplifier KrF laser was developed. This was seeded by a smaller oscillator laser by means of a coupled unstable resonator configuration. A number of different cavity arrangements were investigated and an output beam divergence of 2.5 times the diffraction limit was achieved. The plasmas generated by focusing the laser beam to an intensity of 1014W/cm2 onto carbon, titanium, molybdenum and tungsten targets were characterized as fully as was necessary for their use in the X-ray microscope. Preliminary investigations on the use of a grazing incidence ellipsoidal mirror to focus the emitted X-rays onto the specimen of the microscope were made and such an optical component was manufactured and tested. Finally, numerous images of a number of different biological specimens were made and resolutions of better than 100nm were achieved. Images were read out using a Park Scientific Instruments atomic force microscope, which enabled the entire microscopy process to be carried out in a single working day. The system is now in routine use and can produce more than ten images per session.
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Butler, Justin John. "Quantum Well Structures for Plasma Instability-based Terahertz Radiation Sources." Thesis, Boston College, 2012. http://hdl.handle.net/2345/2886.
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Thesis advisor: Pradip BakshiThis thesis is a theoretical study of the electron transport and response properties of epitaxially grown, low-dimensional semiconductor quantum well heterostructures, under steady-state, current driven (nonequilibrium) conditions. These structures operate in the Terahertz (THz) frequency and submillimeter wavelength range, and are the leading candidates for compact, coherent sources of THz radiation. This work is divided into two parts: Part I consists of an analytical study of the individual quantum well units, and the tunneling transmission characteristics, for which reasonably accurate algebraic expressions are obtained. An underlying philosophy of this work is the desire to describe each of the key components involved, independently, through these simple analytical expressions. In Part II the numerical study of the transport and radiation response of the quantum well structures specially designed to generate THz radiation based on the plasma instability concept is presented. Several models are proposed which describe the overall electron transport and which determine the underlying nonequilibrium steady state. In particular, the key features of the experimental current-voltage (IV) curves for such structures are explained, and the corresponding response properties are determined. The modeling and simulation of these potential optoelectronic devices is a crucial tool for elucidating the precise mechanisms and interplay of the many microscopic processes which give rise to the observed behavior. Key features of the radiation response arise from the intersubband plasma instability which occurs due to the resonant interaction of an emission and an absorption mode, and these features are compared with the experimental observations
Thesis (PhD) — Boston College, 2012
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
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Bourgeois, Pierre-Louis. "Modélisation de sources X générées par interaction laser-plasma en régime relativiste." Thesis, Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAX073.
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Lors de la propagation d'une impulsion laser ultra courte, ultra intense dans un gaz de faible densité, un plasma est créé et une partie des électrons vont pouvoir être accélérés grâce à la technique de sillage laser à des énergies de plusieurs GeV en quelques centimètres.Ces électrons, lors de leur accélération, émettent un rayonnement X appelé bêtatron, qui est fortement collimaté et possède de très bonnes propriétés spatiales et temporelles, lui donnant de nombreuses applications dont l'imagerie ultra-haute résolution.Dans cette thèse, on étudie comment améliorer les outils numériques utilisés pour simuler ces phénomènes physiques : les codes Particle-In-Cell (CALDER). On s'intéresse notamment à un artefact numérique appelé rayonnement Cherenkov numérique, qui survient lorsque les particules accélérés se déplacent à des vitesses proches de la vitesse de la lumière dans le vide.On démontre que cet artefact a un effet néfaste sur le comportement du faisceau d'électrons accélérés, en particulier sur son mouvement transverse, ce qui conduit à des erreurs importantes sur le calcul du rayonnement bêtatron à partir des simulations PIC. On propose alors une nouvelle approche pour limiter l'impact de ce rayonnement Cherenkov numérique sur les simulations d'accélération par sillage laser en modifiant la méthode d'interpolation des champs habituellement utilisée dans un code PIC. Les résultats obtenus avec cette nouvelle technique mettent en évidence une nette amélioration de la modélisation du mouvement des électrons, qui se rapproche du comportement attendu théoriquement. Fort de ces premiers résultats, d'autres applications de cette technique sont ensuite explorées, pour améliorer la modélisation des sources bêtatron, de l'accélération par laser dans le vide ou de l'accélération directe par laser.La plus grande précision sur le calcul du mouvement transverse des particules qu'apporte cette nouvelle méthode permet d'améliorer les résultats mais aussi d'étudier des phénomènes physiques aux effets subtils qui sont autrement cachés par le bruit numérique des simulationsWhen an ultra-short ultra-intense laser impulsion propagates through a low density gas jet, a plasma is created and a bunch of electrons can be accelerated through laser wakefield acceleration to Gev energies in only a few centimetres. Those accelerated electrons then emit what is called Betatron radiation: a highly focused X-ray source with extremely good spatial and temporal properties, which has a lot of possible applications including ultra-high resolution imaging.In this thesis, we investigate possible improvements to one of the main numerical tools used to simulate those phenomenons: the Particle-In-Cell codes (CALDER). We have especially studied a numerical artefact called the numerical Cherenkov radiation, that occurs when relativistic particles move at speeds aproaching the speed of light in a vaccuum.We show that this artefact has a negative impact on the behaviour of the accelerated electron beam, especially on its transverse motion, which leads to important errors on the betatron radiation calculated using PIC simulations.We then introduce a new approach to mitigate the impact of this numerical Cherenkov radiation on laser wakefield acceleration simulation with a simple modification of the electromagnetic field interpolation method used in PIC codes. The results obtained with this new technique show a meaningful improvement on the electron motion wich becomes close to the theoretically expected behaviour.We then explore other possible applications for this new technique, notably improving the modelization of betatron sources, vacuum laser acceleration or direct laser acceleration.The improvement of the computation of the particles transverse motion thanks to this new method leads to more accurate results but also enables us to study physical phenomenon with subtle effects that would otherwise be hidden among the numerical noise of the simulation
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Hemberg, Oscar. "Compact Liquid-Jet X-Ray Sources." Doctoral thesis, KTH, Physics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3716.
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This thesis describes the development, characterization andoptimization of compact, high-brightness, liquid-jet-targetx-ray sources. Two different source types have been developedfor different wavelength regions and applications.
A laser-plasma source for generating soft x-ray andextreme-ultraviolet radiation has been further developed forsoft x-ray microscopy and extreme-ultraviolet lithography. Thiswork focused on improved target stability, increased conversionefficiency and decreased debris production. For x-raymicroscopy applications using carbon-containingliquid-jetdroplet targets, the droplet stability has beeninvestigated and a method for source stabilization introduced.This source has also been optimized in terms of flux per debriswith respect to target material and size. Forextreme-ultraviolet lithography applications, aliquid-xenon-jet-target laser-plasma source system has beengreatly improved, especially in terms of stability andconversion efficiency. This source has also been characterizedin terms of, e.g., source size, angular distribution, andrepetition-rate capability. For extremeultraviolet lithography,the possible use of tin as a target material has also beenstudied and conversion efficiency and debris measurementsperformed.
A new anode concept for electron-impact hard x-ray sourcesbased on high-speed liquidmetal jets has been introduced.Initial calculations show that this new target concept couldpotentially allow more than a hundred-fold increase in sourcebrightness compared to existing state-of-the-art technology. Alow-power, proof-of-principle, experiment has been performed,verifying the basic source concept. Scaling tohigh-poweroperation is discussed and appears plausible. A main obstaclefor high-power operation, the generation of a microscopichigh-speed jet in vacuum, is investigated usingdynamic-similarity experiments and shown to be feasible.Finally, initial medium-power experiments, approaching currentstate-of-the-art sources in terms of brightness, have beenperformed.
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Cantono, Giada. "Relativistic Plasmonics for Ultra-Short Radiation Sources." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS353/document.
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La plasmonique étudie le couplage entre le rayonnement électromagnétique et les oscillations collectives des électrons dans un matériel. Les plasmons de surface (SPs), notamment, ont la capacité de concentrer le champ électromagnétique sur des distances micrométriques, ce qui les rend intéressants pour le développement des dispositifs photoniques les plus novateurs. 'Etendre l'excitation de SPs au régime de champs élevés, où les électrons oscillent à des vitesses relativistes, ouvre des perspectives stimulantes pour la manipulation de la lumière laser ultra-intense et le développement de sources de rayonnement énergétiques et à courte durée. En fait, l'excitation de modes résonnants du plasma est l'une des stratégies possibles pour transférer efficacement l'énergie d'une impulsion laser ultra-puissante à une cible solide, cela étant parmi les défis actuels dans la physique de l’interaction laser-matière à haute intensité. Dans le cadre de ces deux sujets, ce travail de thèse démontre la possibilité d'exciter de façon résonnante des plasmons de surface avec des impulsions laser ultra-intenses. Elle étudie comment ces ondes peuvent à la fois accélérer de paquets d'électrons relativistes le long de la surface de la cible mais aussi augmenter la génération d'harmoniques d'ordre élevé de la fréquence laser. Ces deux processus ont été caractérisés avec de nombreuses expériences et simulations numériques. En utilisant un schéma d’interaction standard de la plasmonique classique, les SPs sont excités sur des cibles dont la surface présente une modulation périodique régulière à l'échelle micrométrique (cibles réseau). Dans ce cas, les propriétés de l'émission d'électrons tout comme celles des harmoniques permettent d’envisager leur utilisation dans des application pratiques. En réussissant à dépasser les principaux problèmes conceptuels et techniques qui jusqu'au présent avaient empêché l'application d'effets plasmoniques dans le régime de champs élevés, ces résultats apportent un intérêt nouveau à l'exploration de la Plasmonique RelativistePlasmonics studies how the electromagnetic radiation couples with the collective oscillations of the electrons within a medium. Surface plasmons (SPs), in particular, have a well-established role in the development of forefront photonic devices, as they allow for strong enhancement of the local EM field over sub-micrometric dimensions. Promoting the SP excitation to the high-field regime, where the electrons quiver at relativistic velocities, would open stimulating perspectives for the both the manipulation of ultra-intense laser light and the development of energetic, short radiation sources. Indeed, the excitation of resonant plasma modes is a possible strategy to efficiently deliver the energy of a high-power laser to a solid target, this being among the current challenges in the physics of highly-intense laser-matter interaction. Gathering these topics, this thesis demonstrates the opportunity of resonant surface plasmon excitation at ultra-high laser intensities by studying how such waves accelerate bunches of relativistic electrons along the target surface and how they enhance the generation of high-order harmonics of the laser frequency. Both these processes have been investigated with numerous experiments and extensive numerical simulations. Adopting a standard configuration from classical plasmonics, SPs are excited on solid, wavelength-scale grating targets. In their presence, both electron and harmonic emissions exhibit remarkable features that support the conception of practical applications. Putting aside some major technical and conceptual issues discouraging the applicability of plasmonic effects in the high-field regime, these results are expected to mark new promises to the exploration of Relativistic Plasmonics
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Sadouni, Sarah. "Modélisation fluide du transport et des instabilités dans des sources plasma froid magnétisé." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30014.
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Il est bien connu que les plasmas froids magnétisés dans des dispositifs tels que les propulseurs Hall et les sources d'ions montrent souvent l'émergence d'instabilités qui peuvent provoquer des phénomènes de transport anormaux et affecter fortement le fonctionnement du dispositif. Dans cette thèse, nous étudions les possibilités de simuler ces instabilités de manière auto-cohérente par la modélisation fluide. Cela n'a jamais été fait auparavant pour ces conditions de plasma froid, mais cela présente un grand intérêt potentiel pour l'ingénierie. Nous avons utilisé un code fluide quasi-neutre développé au laboratoire LAPLACE, appelé MAGNIS (MAGnetized Ion Source), qui résout un ensemble d'équations fluides pour les électrons et les ions dans un domaine 2D perpendiculaire au champ magnétique. On a constaté que dans de nombreux cas d'intérêt pratique, les simulations MAGNIS produisent des instabilités et des fluctuations du plasma. Un premier objectif de cette thèse est de comprendre l'origine de ces instabilités observées dans MAGNIS et de s'assurer qu'elles sont un résultat physique et non un artefact numérique. Pour ce faire, nous avons effectué une analyse de stabilité linéaire basée sur des relations de dispersion, dont les taux de croissance et les fréquences qui en sont issus analyse ont été comparés avec succès à ceux mesurés dans les simulations de MAGNIS pour des configurations simples et forcés à rester dans un régime linéaire. Nous avons ensuite identifié les principaux modes et mécanismes de ces instabilités (induits par les champs électrique et magnétique, le gradient de densité et l’inertie), connus de la littérature, susceptibles de se produire dans ces simulations de fluides. Par la suite, nous avons simulé l'évolution non-linéaire et la saturation des instabilités et quantifié le transport anormal généré dans différents cas relatifs aux sources d'ions en fonction de divers paramètres clés du système (champs électriques et magnétiques et température des électrons). Enfin, nous avons mis en évidence plusieurs limitations de MAGNIS, et plus généralement de modèles fluides, dues aux approximations physiques (quasi-neutralité, absence d'effets cinétiques). Nous avons montré que les modes fluides sont parfois les plus instables à des échelles infiniment petites où la théorie n'est plus valable et ne peuvent donc être résolues numériquement. Nous avons proposé différentes manières de remédier à ce problème par l’introduction de termes diffusifs inspirés de la physique à petite échelle (non-neutralité, rayon de Larmor), que nous avons ensuite testés dans MAGNISIt is well known from experiments that magnetized low-temperature plasmas in devices such as Hall thrusters and ion sources often show the emergence of instabilities that can cause anomalous transport phenomena and strongly affect the device operation. In this thesis we investigate the possibilities to simulate these instabilities self-consistently by fluid modeling. This is of great potential interest for engineering. We used a quasineutral fluid code developed at the LAPLACE laboratory, called MAGNIS (MAGnetized Ion Source), solving a set of fluid equations for electrons and ions in a 2D domain perpendicular to the magnetic field lines. It was found that in many cases of practical interest, MAGNIS simulations show plasma instabilities and fluctuations. A first goal of this thesis is to understand the origin of the instabilities observed in MAGNIS and make sure that they are a physical result and not numerical artifacts. For this purpose, we carried out a detailed linear stability analysis based on dispersion relations, from which analytical growth rates and frequencies were successfully compared with those measured in MAGNIS simulations for simple configurations forced to remain in a linear regime. We then identified these linear unstable modes and their responsible mechanisms (involving parameters such as the density gradient, electric and magnetic fields and inertia), known from the literature, that are likely to occur in these fluid simulations. Subsequently, we simulated the nonlinear evolution and saturation of the instabilities and quantified the anomalous transport generated in different cases relevant to ion sources, depending on various key parameters of the system (electric and magnetic fields and electron temperature). Finally, we highlighted several limitations of MAGNIS, and more generally of fluid models, due to the physical approximations made (quasineutrality, absence of kinetic effects). We showed that the fluid modes are sometimes most unstable at infinitely small scales for which the theory is no longer valid and which cannot be resolved numerically. We proposed, and tested in MAGNIS, ways to overcome this problem by introducing effective diffusion terms representing small scale processes (non-neutrality, Larmor radius)
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Berglund, Martin. "Miniature Plasma Sources for High-Precision Molecular Spectroscopy in Planetary Exploration." Doctoral thesis, Uppsala universitet, Ångström Space Technology Centre (ÅSTC), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-251315.
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The prospect of finding life outside Earth has fascinated mankind for ages, and new technology continuously pushes the boundary of how remote and how obscure evidence we can find. Employing smaller, or completely new, types of landers and robots, and equipping them with miniature instruments would indeed revolutionize exploration of other planets and moons. In this thesis, microsystems technology is used to create a miniature high-precision isotope-resolving molecular spectrometer utilizing the optogalvanic effect. The heart of the instrument, as well as this thesis, is a microplasma source. The plasma source is a split-ring resonator, chosen for its simplicity, pressure range and easily accessible plasma, and modified to fit the challenging application, e.g., by the adding of an additional ground plane for improved electromagnetic shielding, and the integration of microscopic plasma probes to extract the pristine optogalvanic signal. Plasma sources of this kind have been manufactured in both printed circuit board and alumina, the latter for its chemical inertness and for compatibility with other devices in a total analysis system. From previous studies, classical optogalvanic spectroscopy (OGS), although being very sensitive, is known to suffer from stability and reproducibility issues. In this thesis several studies were conducted to investigate and improve these shortcomings, and to improve the signal-to-noise ratio. Moreover, extensive work was put into understanding the underlying physics of the technique. The plasma sources developed here, are the first ever miniature devices to be used in OGS, and exhibits several benefits compared to traditional solutions. Furthermore, it has been confirmed that OGS scales well with miniaturization. For example, the signal strength does not decrease as the volume is reduced like in regular absorption spectroscopy. Moreover, the stability and reproducibility are greatly increased, in some cases as much as by two orders of magnitude, compared with recent studies made on a classical OGS setup. The signal-to-noise ratio has also been greatly improved, e.g., by enclosing the sample cell and by biasing the plasma. Another benefit of a miniature sample cell is the miniscule amount of sample it requires, which can be important in many applications where only small amounts of sample are available. To conclude: With this work, an important step toward a miniature, yet highly performing, instrument for detection of extraterrestrial life, has been taken.
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Kamtaprasad, Reuvani. "LASER PLASMA RADIATION STUDIES FOR DROPLET SOURCES IN THE EXTREME ULTRAVIOLET." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2147.
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The advancement of laboratory based Extreme Ultraviolet (EUV) radiation has escalated with the desire to use EUV as a source for semiconductor device printing. Laser plasmas based on a mass-limited target concept, developed within the Laser Plasma Laboratory demonstrate a much needed versatility for satisfying rigorous source requirements. This concept produces minimal debris concerns and allows for the attainment of high repetition rates as well as the accommodation of various laser and target configurations. This work demonstrates the generation of EUV radiation by creating laser plasmas from mass-limited targets with indium, tin, and antimony doped droplets. Spectral emission from the laser plasmas is quantified using a flat-field spectrometer. COWAN code oscillator strength predications for each of the dopants were convolved with narrow Gaussian functions creating synthetic spectra for the EUV region between 10 nm - 20 nm. A preliminary comparison was made between the theoretical spectra and experimental results. From this comparison, ion stage transitions for each of the hot dense plasmas generated were assessed.M.S.E.E.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering MSEE
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González, de Alaiza Martínez Pedro. "Generation of intense terahertz sources by ultrashort laser pulses." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS350/document.
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Le spectre électromagnétique possède une zone étroite, localisée entre les micro-ondes et l'infrarouge, appelée région des ondes térahertz (THz), qui est comprise entre 0.1 et 30 THz. Ces ondes, longtemps inaccessibles car situées à la frontière entre l'électronique et l'optique, connaissent aujourd'hui un intérêt grandissant et possèdent des applications prometteuses dans divers secteurs de la science comme l'imagerie médicale et l'identification des explosifs à distance. Cependant, la production de rayonnement THz intense, d'amplitude proche du GV/m, qui devrait permettre de sonder efficacement des matériaux à distance, reste encore une question en suspens. Cette thèse a précisément pour but d'étudier la génération d'un tel rayonnement THz par couplage de deux impulsions laser ultracourtes -une onde fondamentale et son harmonique deux- capables d'ioniser un gaz (par exemple, l'air ou l'argon). Le plasma ainsi créé joue le rôle de convertisseur nonlinéaire de fréquence, transformant une partie de l'énergie du champ laser dans la bande THz via une gamme riche de mécanismes physiques, notamment l'effet Kerr, la photoionization et les forces pondéromotrices induites dans le plasma. Grâce à un travail de modélisation analytique et numérique de ces principaux mécanismes, nous avons examiné de manière complète la génération d'impulsions THz pour des intensités allant de celles rencontrées en filamentation laser (10¹²-10¹⁴ W cm⁻²) jusqu'aux intensités relativistes (10¹⁵-10¹⁸ W cm⁻²), une fourchette d'intensités peu étudiée jusqu'à présent dans ce domaine. Il est déjà connu qu'à basses intensités la photoionization induite par le champ laser domine l'émission térahertz, laquelle dépend fortement de la configuration des couleurs (ou harmoniques) laser. Nous démontrons ici que, au-delà de la configuration laser ''classique'' à deux couleurs, coupler plusieurs fréquences laser suivant les harmoniques d'une forme d'onde en dents de scie est optimal pour renforcer la production de rayonnement. Les simulations prévoient une efficacité de conversion d'énergie THz de 2% avec quatre couleurs, valeur record inégalée à ce jour. De plus, en nous aidant d'une expérience faite dans l'air, nous identifions la signature de l'effet Kerr dans le spectre THz émis, qui, plus faible, se révèle complémentaire de la signature plasma. Quand l'intensité de l'impulsion laser est augmentée au-delà de 10¹⁵ W cm⁻², nous démontrons que le rayonnement térahertz émis croît de manière non-monotone, dû au fait qu'il existe une valeur d'intensité maximisant l'énergie THz produite par chaque couche électronique. Finalement, nous avons étudié en géométrie 2D l'effet combiné de la photoionization et des forces pondéromotrices plasma à des intensités proches de 10¹⁸ W cm⁻², nous permettant d'obtenir des champs THz excédant le GV/m dans l'argon. Ces dernières forces augmentent avec l'intensité laser et ouvrent des perspectives intéressantes pour la génération de champs térahertz très intenses dans le régime relativiste de l'interaction laser-matièreThe electromagnetic spectrum has a narrow frequency band, lying between microwaves and infrared, known as terahertz (THz) waves and extending from 0.1 to 30 THz. These waves, inaccessible until a recent past because they are situated at the boundary between electronics and optics, are raising interest because of their promising applications in several areas such as medical imaging and remote identification of explosives. However, producing intense THz radiation with amplitude belonging to the GV/m range should allow us to probe efficiently remote materials, which still remains an open issue. The goal of this thesis is precisely to study the generation of such intense THz radiation by coupling two ultrashort laser pulses -the fundamental and its second harmonic- able to ionize a gas target (for example, air or argon). The plasma created by photoionization then acts as a nonlinear frequency converter, transforming part of the laser energy into the THz band via a wide range of physical mechanisms including the Kerr effect, the photoionization and ponderomotive forces induced inside the plasma. By means of an analytical and numerical modeling of these key mechanisms, we have comprehensively examined the generation of THz pulses at laser intensities ranging from characteristic intensities met in laser filamentation (10¹²-10¹⁴ W cm⁻²) to sub-relativistic intensities (10¹⁵-10¹⁸ W cm⁻²), this latter intensity range having been little investigated so far in this domain. It is already known that at low intensities laser-induced photionization dominates in terahertzgeneration, which strongly depends on the configuration of the laser colours (or harmonics). We demonstrate here that, beyond the classical two-colour laser setup, coupling several laser frequencies following the harmonics of a sawtooth waveform is optimal to enhance THz production. Simulations predict a laser-to-THz energy conversion efficiency of 2% with four colours, a record value unequalled so far. Moreover, with an experiment realized in air, we identify the Kerr signature in the emitted THz spectrum, which, even weaker, looks complentary to the plasma signature. When the intensity of the laser pulse is increased beyond 10¹⁵ W cm⁻², we prove that the growth of the emitted terahertz radiation is nonmonotonic, due to the fact that that there exists an optimal intensity value that maximizes the THz energy produced by each electronic shell of the irradiated atom. Finally, we have studied in 2D geometry the combined effect of photoionization and ponderomotive forces at intensities close to 10¹⁸ W cm⁻², allowing us to obtain THz fields exceeding the GV/m threshold in argon. These latter forces increase with the laser intensity and thus open interesting perspectives for the generation of very intense terahertz fields in the relativistic regime of laser-matter interaction
El espectro electromagnético posee una zona estrecha, localizada entre las microondas y la radiación infrarroja, llamada región de las ondas Terahertz (THz), que está comprendida entre 0.1 et 30 THz. Estas ondas, durante mucho tiempo inaccesibles debido a que se encuentran situadas en la frontera entre la electrónica y la óptica, están despertando un interés creciente por la gran cantidad de aplicaciones prometedoras que poseen en diversos sectores científicos, como la imagen médica y la identificación de explosivos a distancia. No obstante, la producción de radiación THz intensa, de amplitud cercana al GV/m, la cual debería permitir sondar materiales energéticos a distancia, sigue siendo una cuestión abierta. Esta tesis tiene precisamente como objetivo el estudio de la generación de dicha radiación THz intensa acoplando dos pulsos láser —una onda fundamental y su segundo armónico— capaces de ionizar un gas (por ejemplo, aire o argón). El plasma creado de este modo desempeña el papel de convertidor no lineal de frecuencia, transformando una parte de la energía del láser en la banda THz mediante una rica gama de mecanismos físicos, entre los que destacan el efecto Kerr, la fotoionización y las fuerzas ponderomotrices inducidas dentro del plasma. Gracias a un trabajo de modelización tanto numérico como analítico de estos mecanismos clave, hemos examinado de forma integral la generación de pulsos THz a intensidades láser yendo desde las encontradas en la filamentación láser (10¹²-10¹⁴ W cm⁻²) hasta las cercanas al límite relativista (10¹⁵-10¹⁸ W cm⁻²), habiendo sido este último rango de intensidades poco estudiado en este campo hasta el presente. Ya es sabido que a bajas intensidades la fotoionización inducida por el láser domina la emisión Terahertz, la cual depende enormemente de la configuración de los colores (o armónicos) del láser. Demostramos aquí que, más allá de la “clásica” configuración del láser en dos colores, acoplar varias fréquencias láser siguiendo los armónicos de una forma de onda en diente de sierra es óptimo para incrementar la producción THz. Las simulaciones predicen una eficacia de conversión de energía THz de 2% empleando cuatro colores, un valor récord inigualado hasta hoy. Además, ayudándonos de un experimento realizado en aire, identificamos la firma del effecto Kerr en el espectro THz emitido, la cual, pese a ser más débil, resulta complementaria a la firma del plasma. Cuando se aumenta la intensidad del láser más allá de 10¹⁵ W cm⁻², demostramos que la radiación Terahertz emitida crece de manera no monotóna, debido a que existe un valor de intensidad que maximiza la energía THz producida por cada capa electrónica. Finalmente, hemos estudiado en geometría 2D el efecto conjunto de la fotoionización y de las fuerzas ponderomotrices a intensidades próximas a 10¹⁸ W cm⁻², lo que nos permite obtenter campos THz cuyas amplitudes exceden el GV/m en argon. Estas últimas fuerzas aumentan con la intensidad láser y, por tanto, ofrecen perspectivas interesantes para la generación de campos Terahertz muy intensos en un régimen de interacción láser-materia relativista
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Sakildien, Muneer. "Plasma characterisation of an electron cyclotron resonance ion source by means of x-ray spectroscopy." Thesis, University of the Western Cape, 2012. http://hdl.handle.net/11394/5212.
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>Magister Scientiae - MScThe ultimate aim of any multiply-charged ion source, like the Electron Cyclotron Resonance Ion Source, ECRIS, is the production of multiply-charged ions, in sufficiently large quantities. These multiplycharged ions, in the case of the ECRIS, are created by a step-by-step ionisation process, whereby neutral atoms are ionised by energetic electrons. The goal of this thesis was to gain an understanding of the relative importance of various ECRIS parameters on the production of these energetic electrons. This was done by measuring the bremsstrahlung continuum emitted by the mirror confined plasma of an ECR ion source. The focus of our study was to investigate the influence of neutral pressure, incident microwave power and magnetic field configuration on spectral temperature and electron density of the warm electron population of the ECRIS plasma. The thesis begins by familiarising the reader with various aspects of plasma physics as it relates to the measurements. The measurements were done with a high-purity germanium detector and processed with the DGF Pixie-4 module. Analyses of the measured spectra were done with subroutines written in Root. From the measured result, it was concluded that by increasing the incident microwave power from 50 W to 300 W, the spectral temperature increases by 14.01% for helium plasma and 7.88% for argon plasma. Evidence of saturation of spectral temperature and electron density with increasing microwave power was also noticed, as reported by other groups investigating plasma bremsstrahlung. The increase of spectral temperature with neutral pressure was found to be considerable, increasing by 20.23% as the neutral pressure in the plasma chamber of the ECRIS was decreased. This increase in spectral temperature was accompanied by a 40.33% decrease in electron density, which led us to conclude that the increase in spectral temperature was most likely due to an increase in the mean free path of the electrons. The influence of the magnetic field configuration on both spectral temperature and electron density was also investigated. During this investigation, one of the solenoid coil currents was increased, whilst keeping the other constant. This amounts to moving the plasma volume around axially in the plasma chamber of the ECRIS. This was found to significantly enhance the spectral temperature and this effect was attributed to more efficient heating of the electrons near the resonance zone. The electron density on the other hand was found to remain relatively constant, if one excludes the electron density as a result of one particularly setting of the solenoid coils. The decrease of electron density as a result of this particular setting of the solenoid coils enhanced the electron losses through the magnetic bottle. This is evidenced by the increase in photon counts as measured by our detector. The influence of neutral pressure, incident microwave power and magnetic field configuration on the extracted ion beam intensities was also investigated. This investigation led us to conclude that the mean charge state extracted increases with spectral temperature. This result was in agreement with those measured by other groups.
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Sepetys, Arvydas. "Tungsten sources in the divertor and the main chamber and contamination of the WEST tokamak plasmas." Electronic Thesis or Diss., Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0506.
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Afin d'assurer un fonctionnement contrôlé des tokamaks, il est nécessaire de comprendre les mécanismes responsables de la contamination des plasmas de fusion magnétique par des impuretés. La préparation de l'exploitation d'ITER équipé d'un divertor en tungstène, exige de surveiller les sources de tungstène et de caractériser comment les atomes de tungstène érodés sont transportés à travers les zones périphériques. L'une des questions est d'identifier la localisation des sources qui dominent la contaminationDans ce travail, nous nous appuyons sur des mesures spectroscopiques dans les gammes spectrales visible et VUV pour caractériser les impuretés, et en particulier le tungstène, dans les plasmas de WEST. Nous avons étudié la cohérence des de ces mesures avec des données expérimentales provenant d'autres diagnostics (sondes, thermocouples). Nous utilisons l'intensité des raies, mais nous présentons également une étude détailée de la modélisation des profils de raies de tungstène neutreAfin de mieux comprendre les voies de contamination, des plasmas de WEST ont été modélisés à l'aide du code ERO2.0. Au début, le code Soledge2D-EIRENE(S2DE) modélise le plasma de fond, y compris une impureté légère générique, le transport radial étant ajusté sur les mesures disponibles. Après, ERO2.0 utilise le plasma de fond généré par S2DE comme entrée pour modéliser la distribution du W érodé et étudier comment les différents éléments de paroi influencent la distribution poloïdale de densité de tungstène. La probabilité de contamination des sources dues aux différents éléments de paroi a aussi été évaluée. Le rôle du divertor et des protections d'antenne est plus particulièrement discutéUnderstanding the mechanisms responsible for the contamination of magnetically confined plasmas by impurities is necessary to achieve sustainable and controlled operation of tokamaks. To prepare ITER operation with its tungsten divertor, it is necessary to monitor tungsten sources in present tokamaks and to characterize how eroded tungsten atoms get transported across the scrape off layer into the confined plasma. One of the questions is to identify the location of the sources driving the contamination.In this work, spectroscopic measurements in the visible and VUV spectral ranges were performed to characterize impurities, and particularly tungsten, in WEST plasmas. Their consistency with other available experimental data from various diagnostics (probes, thermocouples) was studied. We make use of spectral line intensities, but also present a modelling study of the line shape change of neutral tungsten lines at different plasma conditions.In order to better understand the W contamination pathways, WEST plasmas were modelled using the ERO2.0 code. First, as an input to ERO2.0, the Soledge2D-EIRENE code generated background plasmas including a generic light impurity, where radial transport is adjusted so that the plasma background is consistent with available diagnostics. In a second step, ERO2.0 uses the Soledge2D-EIRENE results as an input to generate the poloidal ion distributions of eroded tungsten and investigate how different source areas influence the poloidal tungsten density field. The contamination probability of the sources due to various wall elements was also evaluated. The role of the divertor and the antenna protection limiters are discussed in more detail
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Takenoshita, Kazutoshi. "DEBRIS CHARACTERIZATION AND MITIGATION OF DROPLET LASER PLASMA SOURCES FOR EUV LITHOGRAPHY." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2786.
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Extreme ultraviolet lithography (EUVL) is a next generation lithographic techniques under development for fabricating semiconductor devices with feature sizes smaller than 32 nm. The optics to be used in the EUVL steppers is reflective optics with multilayer mirror coatings on each surface. The wavelength of choice is 13.5 nm determined by the optimum reflectivity of the mirror coatings. The light source required for this wavelength is derived from a hot-dense plasma produced by either a gas discharge or a laser. This study concentrate only on the laser produced plasma source because of its advantages of scalability to higher repetition rates. The design of a the laser plasma EUVL light source consists of a plasma produced from a high-intensity focused laser beam from a solid/liquid target, from which radiation is generated and collected by a large solid angle mirror or array of mirrors. The collector mirrors have the same reflectivity characteristics as the stepper mirrors. The EUVL light source is considered as the combination of both the hot-dense plasma and the collector mirrors. The EUVL light sources required by the stepper manufacturers must have sufficient EUV output power and long operational lifetimes to meet market-determined chip production rates. The most influential factor in achieving the required EUV output power is the conversion efficiency (CE) of laser input energy relative to the EUV radiation collected. A high CE is demonstrated in a separate research program by colleagues in the Laser Plasma laboratory at CREOL. Another important factor for the light source is the reflectivity lifetime of the collection optics as mirror reflectivity can be degraded by deposition and ablation from the plasma debris. Realization of a high CE but low debris plasma source is possible by reducing the mass of the target, which is accomplished by using tin-doped droplet targets. These have sufficient numbers of tin atoms for high CE, but the debris generation is minimal. The first part of this study investigates debris emissions from tin-doped droplet targets, in terms of aerosols and ions. Numerous tin aerosols can be created during a single laser-target interaction. The effects these interactions are observed and the depositions are investigated using SEM, AFM, AES, XPS, and RBS techniques. The generation of aerosols is found to be the result of incomplete ionization of the target material, corresponding to non-optimal laser coupling to the target for maximum CE. In order to determine the threats of the ion emission to the collector mirror coatings from an optimal, fully ionized target, the ion flux is measured at the mirror distance using various techniques. The ion kinetic energy distributions obtained for individual ion species are quantitatively analyzed. Incorporating these distributions with Monte-Carlo simulations provide lifetime estimation of the collector mirror under the effect of ion sputtering. The current estimated lifetime the tin-doped droplet plasma source is only a factor of 500 less than the stepper manufacturer requirements, without the use of any mitigation schemes to stop these ions interacting with the mirror. The second part of this investigation explores debris mitigation schemes. Two mitigation schemes are applied to tin-doped droplet laser plasmas; electrostatic field mitigation, and a combination of a foil trap with a magnetic field. Both mitigation schemes demonstrate their effectiveness in suppressing aerosols and ion flux. A very small number of high-energy ions still pass through the combination of the two mitigation schemes but the sputtering caused by these ions is too small to offer a threat to mirror lifetime. It is estimated that the lifetime of the collector mirror, and hence the source lifetime, will be sufficient when tin-doped targets are used in combination with these mitigation schemes.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
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Ellis, Wade C. "Fundamental Studies and Applications of Ambient Plasma Ionization Sources for Mass Spectrometry." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6484.
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The field of ambient desorption/ionization mass spectrometry (ADI-MS) has existed for over a decade. ADI-MS is a technique that offers benefits including fast analysis time, simple ionization sources that are easily constructed, and little to no required sample preparation. The research presented here describes efforts to better understand plasma-based ADI-MS sources and to explore the use of hydrogen-doped plasma gases with these sources. The use of hydrogen-doped argon (H2/Ar) and hydrogen-doped helium (H2/He) as plasma gases for a dielectric barrier discharge (DBD) and an AC glow discharge is presented first. When using the DBD, the intensity of the signal obtained when analyzing organic molecules in positive ion mode was increased by factors up to 37 times. In negative ion mode, only H2/Ar was shown to enhance the signal of an organic analyte. The limits of detection for caffeine when using hydrogen-doped plasma gases were found to decrease by factors of 78 and 1.9 for H2/Ar and H2/He respectively. The same phenomenon was observed when using H2/Ar with the AC discharge, but no signal enhancement was observed when using hydrogen-doped helium with the AC discharge. Similarly, if the DBD was allowed to ground through a wire rather than through the air, no signal enhancement was observed for H2/He. Using H2/Ar with metal samples is presented second. By using the metal sample as the grounded electrode for the AC glow discharge, many different metals could be detected directly with a time-of-flight mass spectrometer (TOF-MS) in the form of atomic ions both on their own and in combination with water and ammonia from the discharge. Any refractory metals tested did not yield signal. In addition to direct analysis with a TOF-MS, the AC discharge was used as a sampling method for an inductively coupled plasma mass spectrometer (ICP-MS). When coupled with an ICP-MS, the AC glow discharge was found capable of sampling even refractory elements, though the power of the ICP was required for ionization and detection. Scanning electron microscope (SEM) images of a copper surface exposed to the plasma discharge showed signs of melting when using the H2/Ar. Finally, a computer simulation of the chemistry and flow dynamics of a DC glow discharge generated in helium is presented. The simulation explores many of the fundamental processes at work and how they depend on the composition of the plasma gas. The generation of important species in the plasma was found to depend more on the amount of N2 and H2O impurities in the plasma gas rather than on the humidity or air pressure.
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Fletcher, C. M. "Development of atmospheric pressure plasma based desorption-ionisation sources for mass spectrometry." Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3022827/.
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Sol, Hélène. "Jets et sources radio extragalactiques." Paris 7, 1987. http://www.theses.fr/1987PA077163.
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Travaux sur les proprietes radiatives et dynamiques des jets associes a des galaxies ou a des quasars. L'etude du jet optique de la galaxie active pks 0521-36 est abordee en detail. On decrit ensuite le passage d'un jet vlbi de quelques pc a un jet observe a grande echelle sur plusieurs dizaines de kpc. On traite, sur ce sujet, des mecanismes physiques qui entrent en jeu pour interpreter ce phenomene. En derniere partie on pose le probleme de la determination de la constante de hubble en termes de mirages gravitationnels et celui des jets d'echelle stellaire
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Corde, Sébastien. "Des accélérateurs laser-plasma aux sources de rayonnement X femtoseconde : étude, développement et applications." Phd thesis, Ecole Polytechnique X, 2012. http://pastel.archives-ouvertes.fr/pastel-00680257.
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Lors de l'interaction relativiste entre une impulsion laser brève et intense et un plasma sous-dense, des électrons peuvent être injectés et accélérés jusqu'à plusieurs centaines de MeV dans une structure accélératrice se formant dans le sillage de l'impulsion laser : c'est l'accélérateur laser-plasma. Une des applications majeures de ces accélérateurs réside dans le développement de sources compactes de faisceaux de rayonnement X femtoseconde. Au cours de cette thèse, deux sources de rayonnement X ont été étudiées et développées. Le rayonnement bétatron, intrinsèque à l'accélérateur laser-plasma, provient des oscillations transverses des électrons au cours de leur accélération. Sa caractérisation par comptage de photons a montré que le faisceau X contenait un total de 10^9 photons, avec des énergies pouvant être supérieures à 10 keV. Nous avons également développé une source Compton tout optique produisant des photons de quelques centaines de keV, basée sur la collision entre un faisceau de photons et un faisceau d'électrons. Le potentiel de ces sources de rayonnement a été mis en évidence en réalisant l'imagerie par contraste de phase mono-coup d'un échantillon biologique. Nous avons ensuite montré que l'émission X bétatron est un outil expérimental très puissant pour étudier la physique sous-jacente à l'accélération laser-plasma. On peut tout d'abord réaliser la cartographie de la région d'émission, ce qui donne des informations inédites, permettant par exemple de localiser l'endroit où sont injectés les électrons. Les propriétés angulaires et spectrales du rayonnement X permettent également d'avoir des informations sur la dynamique transverse des électrons au cours de leur accélération.
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Dubois, Loic. "Etudes expérimentales du concept de propulseur de Hall double étage." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30320/document.
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Dans un propulseur à courant de Hall, la création des ions et leur accélération sont régis par le même phénomène physique. L'idée du propulseur de Hall double étage (DSHT) est de découpler l'ionisation du gaz (poussée) et l'accélération des ions (ISP), de sorte à rendre le système davantage versatile. Les travaux menés durant cette thèse visent à démontrer, grâce à des essais expérimentaux, la pertinence et la faisabilité d'un tel concept. Dans un premier temps, un prototype de DSHT, baptisé ID-HALL, a été conçu et assemblé. Il est constitué d'une source inductive magnétisée insérée dans un tube en céramique et d'un étage d'accélération identique à une barrière magnétique de propulseur simple étage. La source inductive a été optimisée de sorte à réduire le couplage capacitif et à maximiser l'efficacité du transfert de puissance par ajout de pièces en ferrite et diminution de la fréquence RF d'excitation. Dans un deuxième temps, la source inductive du propulseur a été caractérisée indépendamment du propulseur en argon et xénon pour différentes pressions. Le dispositif expérimental a permis notamment de tracer une cartographie 2D de la densité et de la température. Enfin, le propulseur a été monté dans son caisson et des mesures préliminaires (caractéristiques courant-tension, mesures par sonde RPA) ont été menées. En parallèle, des simulations utilisant un modèle hybride 2D ont été effectuées en mode simple et double étage. Elles mettent en évidence un fonctionnement versatile du moteur pour des tensions inférieures à 150 V. A terme, on visera à démontrer que la densité de courant et l'énergie des ions peuvent être, dans certaines conditions, significativement découpléesIn Hall thrusters, the same physical phenomenon is used both to generate the plasma and to accelerate ions. Furthermore, only a single operating point is experimentally observed. The double stage Hall thruster (DSHT) design could allow a separate control of ionization (thrust) and ions acceleration (ISP) to make the system more versatile. The work carried out during this PhD aims to experimentally demonstrate the relevance and the feasibility of this concept. Firstly, a new design of DSHT, called ID-HALL, was proposed and a new prototype was built. It combines the concentric cylinder configuration of a single stage Hall thruster with a magnetized inductively coupled RF plasma source (ICP) whose coil is placed inside the inner cylinder. The ICP source was improved in terms of power coupling efficiency by adding ferrite parts and by decreasing the heating RF frequency. The ICP source used in the ID-HALL thruster was then characterized independently of the thruster using argon and xenon and varying pressure. The experimental setup has allowed to measure the spatial variations of the electron density and temperature. Finally, the thruster was mounted in its vacuum chamber and preliminary measures (voltage-current characteristics, RPA measurements) were led. At the same time, simulations using a two-dimensional hybrid model were performed in single and double stage. A versatile operation for voltages lower than 150 V was highlighted. An emphasis will be given to demonstrate that the current density (given by the ion flux probe) and the ions energy (given by the RPA) might be significantly decoupled
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Jiang, Yuchao. "Quelques problèmes de physique et simulation particulaire de plasmas froids partiellement magnétisés et de sources d'ions." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30057.
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Dans cette thèse, nous illustrons certains des enjeux de la physique et de la modélisation des plasmas partiellement magnétisés avec trois exemples spécifiques qui correspondent aux études en cours au sein du groupe GREPHE du laboratoire LAPLACE: 1) Extraction d'électrons dans les sources d'ions négatifs pour l'injection de faisceaux neutres en fusion 2) Instabilités dans les décharges magnétron et propulseurs à courant de Hall 3) Confinement de plasma par festons magnétiques ("magnetic cusps") - Dans l'étude des sources d'ions négatifs pour la fusion, le groupe GREPHE a pour objectif de mieux comprendre la physique de la source d'ions négatifs, et plus spécifiquement, les questions du transport du plasma à travers le filtre magnétique et de l'extraction des ions négatifs du plasma. L'un des problèmes importants de ces sources d'ions négatifs est de minimiser le courant d'électrons qui sont co-extraits avec les ions négatifs. Dans cette thèse, nous nous concentrons sur cet aspect et nous essayons de comprendre et de quantifier comment les électrons peuvent être extraits à travers une ouverture de grille quand un "cusp" magnétique est placé devant l'ouverture. Nous discutons, à l'aide de simulations 3D PIC MCC (Particle-In-Cell Monte Carlo Collisions), les contributions des différentes dérives électroniques (dérive ExB, dérive Grad B et dérive de courbure) et des instabilités à l'extraction d'électrons à travers une ouverture de la grille. - Les propulseurs à courant de Hall et les décharges magnétron sont des dispositifs cylindriques à champs croisés (ExB, champ magnétique B radial et champ électrique E axial). On sait depuis longtemps que des instabilités sont présentes dans ces décharges, conduisant à un transport d'électrons anormal important. Dans cette thèse, nous nous concentrons sur un type particulier d'instabilité (non-uniformité en rotation, ou "rotating spoke"), qui est présent dans les propulseurs à courant de Hall et les décharges de magnétron et qui apparaît dans les expériences comme une non-uniformité lumineuse se déplaçant dans la direction azimutale. Dans ce travail, nous utilisons une simulation 2D PIC MCC pour effectuer une étude paramétrique de cette instabilité. Nous montrons que, dans certaines conditions où ces non-uniformités ont été observées dans les expériences, la dérive des électrons Grad B joue un rôle majeur dans le chauffage des électrons et dans la formation et l'entretien de ces "rotating spokes". [...]In this thesis we will illustrate some of the issues in the physics and modeling of partially magnetized plasmas with three specific examples that correspond to ongoing studies in the GREPHE group of the LAPLACE laboratory: 1) Electron extraction in negative ion sources for neutral beam injection in fusion 2) Instabilities in magnetron discharges and Hall thrusters 3) Plasma confinement by magnetic cusps - In the study of negative ion sources for fusion, the aim of the GREPHE group is to better understand the physics of the negative ion source, and more specifically, the questions of plasma transport across the magnetic filter and of negative ion extraction from the plasma. One of the important issues in these negative ion sources is to minimize the current of electrons that are co-extracted with the negative ions. In this thesis we focus on this aspect and we try to understand and quantify how electrons can be extracted through a grid aperture when a magnetic cusp is placed in front of the aperture. We discuss, with the help of 3D PIC MCC (Particle-In-Cell Monte Carlo Collisions) simulations, the contributions of different electron drifts (ExB drift, Grad B drift and curvature drift) and instabilities to electron extraction through a grid aperture.- Hall thrusters and magnetron discharges are ExB cylindrical devices with radial magnetic field and axial electric field. It has been known for a long time that instabilities are present in these discharges, leading to important anomalous electron transport. In this thesis we focus on one particular type of instability, called "rotating Spoke", which is known to be present in Hall thrusters and magnetron discharges and is apparent in the experiments as a luminous non-uniformity rotating in the azimuthal direction. In this work we use a 2D PIC MCC simulation to perform a parametric study of this instability. We show that, in some conditions where rotating spokes have been observed in the experiments, Grad B electron drift plays a major role in electron heating and in the formation and maintenance of the rotating spokes.- Magnetic cusps have been used for more than 60 years to confine the plasma in a large variety of conditions. An important parameter characterizing plasma confinement by cusps is the effective loss area in the presence of magnetic cusps. Some semi-empirical theories have been proposed to quantify the effective loss area and their predictions have been compared with numerous experimental results. In spite of these efforts there is no fully reliable expression of the effective wall loss as a function of different parameters such as magnetic field, electron temperature, ion mass, gas pressure, etc... We describe in this thesis an attempt at obtaining scaling laws for the effective loss width of magnetic cusps, based on 2D PIC MCC simulations
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Amponsah-Manager, Kwabena. "Microchip lasers as sources of laser-induced breakdown spectroscopy plasma characteristics and analytical performance /." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011595.
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Rotundo, Fabio <1983>. "Design and optimization of components and processes for plasma sources in advanced material treatments." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4625/.
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The research activities described in the present thesis have been oriented to the design and development of components and technological processes aimed at optimizing the performance of plasma sources in advanced in material treatments.
Consumables components for high definition plasma arc cutting (PAC) torches were studied and developed. Experimental activities have in particular focussed on the modifications of the emissive insert with respect to the standard electrode configuration, which comprises a press fit hafnium insert in a copper body holder, to improve its durability. Based on a deep analysis of both the scientific and patent literature, different solutions were proposed and tested. First, the behaviour of Hf cathodes when operating at high current levels (250A) in oxidizing atmosphere has been experimentally investigated optimizing, with respect to expected service life, the initial shape of the electrode emissive surface. Moreover, the microstructural modifications of the Hf insert in PAC electrodes were experimentally investigated during first cycles, in order to understand those phenomena occurring on and under the Hf emissive surface and involved in the electrode erosion process. Thereafter, the research activity focussed on producing, characterizing and testing prototypes of composite inserts, combining powders of a high thermal conductibility (Cu, Ag) and high thermionic emissivity (Hf, Zr) materials
The complexity of the thermal plasma torch environment required and integrated approach also involving physical modelling. Accordingly, a detailed line-by-line method was developed to compute the net emission coefficient of Ar plasmas at temperatures ranging from 3000 K to 25000 K and pressure ranging from 50 kPa to 200 kPa, for optically thin and partially autoabsorbed plasmas.
Finally, prototypal electrodes were studied and realized for a newly developed plasma source, based on the plasma needle concept and devoted to the generation of atmospheric pressure non-thermal plasmas for biomedical applications.L’attività di ricerca svoltasi durante il Dottorato è stata orientata alla progettazione e allo sviluppo di componenti e processi tecnologici innovativi atti ad ottimizzare le prestazioni di sorgenti plasma nel trattamento avanzato di materiali. Sono stati in particolare studiati e sviluppati consumabili di torce al plasma termico per il taglio di materiali metallici (PAC, plasma arc cutting), nell’ambito della cosiddetta alta definizione. L’attività di tipo sperimentale in ambito PAC si è concentrata sulla valutazione e realizzazione di modifiche dell’inserto emettitore, rispetto alla configurazione attuale di elettrodi standard, che prevede un inserto piatto in afnio (Hf) inserito per interferenza in un corpo elettrodo in rame (Cu). Le soluzioni proposte per l’attività di ricerca sono state basate su un’approfondita analisi bibliografica e brevettuale. Il comportamento di inserti in Hf operanti ad alte correnti (250A) in torce PAC è stato sperimentalmente analizzato, ottimizzando la forma iniziale della superficie emittente per incrementarne la vita utile. Sono inoltre state studiate le modificazioni microstrutturali dell’inserto emettitore al fine di comprendere i fenomeni coinvolti nel processo di erosione. Infine, l’attività di ricerca su elettrodi PAC si è concentrata sulla produzione, caratterizzazione e test di inserti compositi prototipali, realizzati unendo polveri ad alta conduttività termica (Cu, Ag) e polvere ad alta emissività termoionica (Hf, Zr). La complessità del sistema torcia ha inoltre richiesto un approccio integrato, che affiancasse attività di simulazione modellistico-computazionale con le valutazioni sperimentali, di natura chimico-fisica e microstrutturale. È stato in questo senso implementato un modello per il calcolo del coefficiente di emissione netto (NEC) del plasma di Argon in funzione di temperatura (1000-25000 K) e pressione (50-200 kPa), per plasmi otticamente sottili o parzialmente auto-assorbiti. Sono infine stati inoltre studiati e realizzati elettrodi prototipali per sorgenti di plasma non termico, finalizzate in particolare ad applicazioni biomedicali, nella configurazione detta plasma needle.
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Corde, Sébastien. "Des accélérateurs laser-plasma aux sources de rayonnement X femtoseconde : étude, développement et applications." Palaiseau, Ecole polytechnique, 2012. http://pastel.archives-ouvertes.fr/docs/00/68/02/57/PDF/These_SCorde_version_electronique.pdf.
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Lors de l'interaction relativiste entre une impulsion laser brève et intense et un plasma sous-dense, des électrons peuvent être injectés et accélérés jusqu'à plusieurs centaines de MeV dans une structure accélératrice se formant dans le sillage de l'impulsion laser : c'est l'accélérateur laser-plasma. Une des applications majeures de ces accélérateurs réside dans le développement de sources compactes de faisceaux de rayonnement X femtoseconde. Au cours de cette thèse, deux sources de rayonnement X ont été étudiées et développées. Le rayonnement bétatron, intrinsèque à l'accélérateur laser-plasma, provient des oscillations transverses des électrons au cours de leur accélération. Sa caractérisation par comptage de photons a montré que le faisceau X contenait un total de 10^9 photons, avec des énergies pouvant être supérieures à 10 keV. Nous avons également développé une source Compton tout optique produisant des photons de quelques centaines de keV, basée sur la collision entre un faisceau de photons et un faisceau d'électrons. Le potentiel de ces sources de rayonnement a été mis en évidence en réalisant l'imagerie par contraste de phase mono-coup d'un échantillon biologique. Nous avons ensuite montré que l'émission X bétatron est un outil expérimental très puissant pour étudier la physique sous-jacente à l'accélération laser-plasma. On peut tout d'abord réaliser la cartographie de la région d'émission, ce qui donne des informations inédites, permettant par exemple de localiser l'endroit où sont injectés les électrons. Les propriétés angulaires et spectrales du rayonnement X permettent également d'avoir des informations sur la dynamique transverse des électrons au cours de leur accélérationDuring the relativistic interaction between a short and intense laser pulse and an underdense plasma, electrons can be injected and accelerated up to hundreds of MeV in an accelerating structure formed in the wake of the pulse: this is the so-called laser-plasma accelerator. One of the major perspectives for laser-plasma accelerators resides in the realization of compact sources of femtosecond x-ray beams. In this thesis, two x-ray sources was studied and developed. The betatron radiation, intrinsic to laser-plasma accelerators, comes from the transverse oscillations of electrons during their acceleration. Its characterization by photon counting revealed an x-ray beam containing 10^9 photons, with energies extending above 10 keV. We also developed an all-optical Compton source producing photons with energies up to hundreds of keV, based on the collision between a photon beam and an electron beam. The potential of these x-ray sources was highlighted by the realization of single shot phase contrast imaging of a biological sample. Then, we showed that the betatron x-ray radiation can be a powerful tool to study the physics of laser-plasma acceleration. We demonstrated the possibility to map the x-ray emission region, which gives a unique insight into the interaction, permitting us for example to locate the region where electrons are injected. The x-ray angular and spectral properties allow us to gain information on the transverse dynamics of electrons during their acceleration
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Averkin, Sergey Nikolaevich. "A Global Enhanced Vibrational Kinetic Model for Radio-Frequency Hydrogen Discharges and Application to the Simulation of a High Current Negative Hydrogen Ion Source." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-dissertations/89.
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A Global Enhanced Vibrational Kinetic (GEVKM) model is presented and applied to the simulation of a new High Current Negative Hydrogen Ion Source (HCNHIS) developed by Busek Co. Inc. and Worcester Polytechnic Institute. The HCNHIS consists of a high-pressure radio-frequency discharge (RFD) chamber in which the main production of high-lying vibrational states of the hydrogen molecules occurs, a bypass system, and a low-pressure negative hydrogen ion production (NIP) region where negative ions are generated by the dissociative attachment of low energy electrons to rovibrationally excited hydrogen molecules. The GEVKM is developed from moment equations for multi-temperature chemically reacting plasmas and for a cylindrical geometry of an inductively coupled discharge chamber. The species included into the model are ground state hydrogen atoms H and molecules H2, 14 vibrationally excited hydrogen molecules H2(v), v=1-14, electronically excited hydrogen atoms H(2), H(3), ground state positive ions H+, H2+, H3+, ground state negative ions H-, and electrons e. The space-averaged steady-state continuity equations coupled with the electron energy equation, the total energy equation and heat transfer to the chamber walls, are solved simultaneously in order to obtain the space-averaged number densities of the plasma components, the electron and heavy particle temperatures as well as the wall temperature. The GEVKM is supplemented by a comprehensive set of surface and volumetric chemical processes governing vibrational and ionization kinetics of hydrogen plasmas. The GEVKM is verified and validated in the low pressure, in the intermediate to high-pressure (1-100 Torr) and high absorbed power density (8.26-22 W/cm3) regimes by comparisons with the numerical simulations and experimental measurements. The GEVKM is applied to the simulation of the RFD chamber of the HCNHIS. The GEVKM predictions of negative hydrogen ions number densities and electron temperatures in the RFD chamber of the HCNHIS are used to estimate the negative hydrogen ion current using the Bohm flux approximation. The estimated negative current compare well with the Faraday Cup measurements and provide additional validation of the model. The GEVKM is used in a parametric investigation of the RFD chamber of HCNHIS-2 with hydrogen inlet flow rates 5-1000 sccm and absorbed powers 200-1000 W.
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Regnard, Guillaume. "Développement d'une nouvelle génération de plasmas micro-onde à conditions opératoires étendues." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENY060/document.
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Ce travail de thèse a été réalisé au Laboratoire de Physique Subatomique et de Cosmologie (IN2P3) deGrenoble en collaboration avec le groupe Thalès avec pour objectif le développement d’une nouvellegénération de plasmas micro-onde fonctionnant sur une gamme de pression étendue allant de 0,5 mtorrà 10 torr en argon. La travail présenté porte donc en : i) la conception des applicateurs basés sur destronçons de longueur λ/4 faisant office de transformateurs d’impédance entre le générateur et leplasma d’impédance supposée donnée (adaptation d’impédance approchée); ii) la déterminationexpérimentale de l’impédance réelle du plasma (partie réelle et partie imaginaire) par mesure dumodule et de la phase du coefficient de réflexion dans des conditions opératoires définies; iii) leredimensionnement des différents tronçons de l’applicateur par simulation numérique en tenantcompte de l’impédance réelle du plasma; iv) la validation expérimentale de l’adaptation d’impédanceentre générateur et plasma. Les résultats obtenus démontrent clairement qu’il est possible, à fréquencedonnée (2.45 GHz dans le cas présent), de concevoir et de dimensionner une source plasma avec uneefficacité énergétique supérieure à 80% pour des fenêtres en pression (d’au moins une décade)équivalentes à des fenêtres opératoires en termes de paramètres plasma. Ces sources individuelles àabsorption localisée de micro-ondes peuvent être utilisées en nombre pour la réalisation des plasmasuniformes de grandes dimensions par leur distribution selon des réseaux à deux dimensions (sourcesplanes) ou à trois dimensions (volumes de plasma), et donc pour des applications industrielles auxtraitements de surfaceThis work was done in the « Laboratoire de Physique Subatomique et de Cosmologie (IN2P3,Grenoble) » during a collaboration with Thales. The aim of the project was the development of a newgeneration of microwave plasma with extended operating conditions in the pressure range 0.5 mtorr to10 torr in argon. The presented work consists of: i) designing applicators based on sections of λ/4length serving as impedance transformers between the generator and the plasma with impedance ofgiven assumed value (approximate impedance adaptation); ii) experimentally determine the realplasma impedance (the real part and the imaginary part) for given operating conditions from themeasurement of modulus and phase of the reflection coefficient S11; iii) resize the different sections ofthe applicator by digital simulation taking the real plasma impedance into account; iv) finally, verifyexperimentally that the impedance adaptation between the generator and the plasma is correct. Theobtained results clearly demonstrate that it is possible, at a given frequency (here 2.45 GHz), to designand size a plasma source with an efficiency greater than 80 % for a window in pressure (at least onedecade) equivalent to an operating window in terms of plasma parameters. These individual sourceswith localized absorption of microwaves can be used in numbers to achieve uniform plasmas via theirdistribution over two-dimensional (planar sources) or tri-dimensional (volume plasma) networks, andthus for industrial surface treatments
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Fritzler, Sven. "Sources de particules avec des lasers de haute intensité: un outil pour les diagnostics plasma et une source innovante pour les applications." Phd thesis, Ecole Polytechnique X, 2003. http://pastel.archives-ouvertes.fr/pastel-00000745.
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Cette thèse de doctorat s'intègre dans le cadre des études tant expérimentales que théoriques sur la production et l'accélération de faisceaux de particules par interaction laser plasma en régime relativiste. Dans la première partie de ce mémoire, les différents mécanismes physiques à l'origine de la production de neutrons, d'électrons et de protons sont passés en revue et discutés. La deuxième partie s'intéresse à la production de neutrons par la réaction D(d,n)3He utilisée comme diagnostic de la température ionique d'un plasma sous dense. Lors de la production de faisceaux d'électrons à partir d'un faisceau laser ultra-court focalisé sur un jet de gaz, un nouveau régime d'accélération, le "sillage forcé", a été mis en évidence. Cette étude fait l'objet de la troisième partie. Il a été montré expérimentalement et théoriquement que l'utilisation d'un laser compact peut produire un faisceau d'électrons très énergétiques et de bonne qualité. La dernière partie est consacrée à la génération de faisceaux de protons avec une cible solide et mince à partir de la même chaîne laser. Pour chaque type de sources de particules, plusieurs applications sont discutées dans les domaines de la physique des accélérateurs, pour la physique médicale et pour la génération de rayonnement X par des processus secondaires.
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Peng, Sheng. "Ultraviolet sources for advanced applications in the vacuum UV and near UV." W&M ScholarWorks, 2004. https://scholarworks.wm.edu/etd/1539623467.
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This dissertation documents a systematic study consisting of experimental investigations and theoretical analyses of intense ultraviolet sources in VUV and near-UV. Some engineering issues regarding two prototypes of electrodeless lamps using rf and microwave are discussed.;Various excimers that produce intense UV light are investigated, including: (1) A benchmark Xe2 excimer which has been proven to be very efficient in our novel rf capacitively coupled discharge lamp; (2) A rarely studied excimer, KrI, which suffers from predissociation and was reported to be very weak or invisible by most of other studies; (3) XeI excimer whose emission dominates around 253 nm and is promising as a mercury-free lamp for antibacterial applications. In the above studies, discharge temperatures are estimated from the emission band width. An elaborate kinetic model is developed for KrI to account for the KrI* and I2* intensities as a function of pressure. It was found that Kr2* plays the rule for energy transfer instead of Kr* in the pressure of interest. The electromagnetic wave interaction with charge particles is studied in our 2D and 3D EM-PIC simulations for both the rf and microwave lamps. Important plasma parameters, such as the electron density and temperature are obtained for various pressures. The electron energy distribution function that is important to account for excimer excitation is obtained.;We also performed a high-level ab initio calculation in Gaussian to produce the ground state potential curve for KrI, which agrees with previous scattering experiments and is necessary for predicting spectral emissions. as a systematic study to account for the KrI emission spectra at high pressure, we use a semiclassical model to account for emissions between a bound excited state and an unbound ground state. An explicit expression is obtained to represent the observed spectral intensity. Important molecular constants are obtained for KrI and compared with previous results.
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Rauner, David [Verfasser], and Ursel [Akademischer Betreuer] Fantz. "Efficiency of RF plasma generation for fusion relevant ion sources / David Rauner ; Betreuer: Ursel Fantz." Augsburg : Universität Augsburg, 2019. http://d-nb.info/1181693330/34.
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Gauter, Sven [Verfasser]. "Calorimetric investigation on plasma and ion beam sources used for thin film deposition / Sven Gauter." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1168229146/34.
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Stancampiano, Augusto <1987>. "Design and Diagnostics of Non-Equilibrium Atmospheric Plasma Sources for Cell Treatment and Bacterial Decontamination." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7593/.
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The dissertation focuses on several aspects of non-equilibrium atmospheric plasma technology, also known as cold atmospheric plasma (CAP) technology, including the design, the diagnostic and the optimization of CAP sources for biomedical applications.
The first part of the dissertation concerns the characterization of a single electrode atmospheric pressure plasma jet (APPJ) through various diagnostic techniques, including ICCD and Schlieren high speed imaging. First, the results for the APPJ freely expanding in atmosphere are presented along with the detailed description of the methodology developed for the ICCD analysis of plasma discharges driven by sub-microsecond voltage pulses. Second, results on the investigation on the APPJ source while impinging on a liquid substrate are shown to highlight the influence of the presence of the liquid substrate on the characteristics of the plasma discharge.
In the second part of the dissertation focuses on the application of CAP technology in various branches of the medical field. The applications reported in this dissertation include: plasma treatment of soft reline palatal obturators prostheses for bacterial decontamination and reduction of bacteria adhesion; plasma direct and indirect treatment of L5178Y lymphoma cells to investigate the fundamental mechanisms promoting cell death and cell-cycle arrest; plasma treatment of tooth root canal dentin in standard dental procedures for the enhancement of the adhesion of resin composites for dental restorations. Overall, all findings support the feasibility of these plasma applications and help in the understanding of some of their governing mechanisms.
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Manclossi, Mauro. "Interaction laser plasma dans le régime relativiste : Application à la production de sources ultrabrèves de particules énergétiques." Phd thesis, Ecole Polytechnique X, 2006. http://pastel.archives-ouvertes.fr/pastel-00002571.
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Cette thèse est liée à la recherche sur la fusion inertielle, et elle concerne en particulier l'approche de l'allumage rapide, qui est basée sur l'utilisation des impulsions laser ultra-intenses pour allumer le combustible thermonucléaire. Jusqu'ici, la praticabilité de ce schéma n'a pas été prouvée et dépend de beaucoup d'aspects fondamentaux de la physique impliquée, qui ne sont pas encore entièrement compris et qui sont aussi très loin d'être contrôles. Le but principal de ce travail de thèse est l'étude expérimentale des processus du transport dans la matière sur-dense (solide) et sous-dense (jet de gaz) d'un faisceau d'électrons rapides produit par des impulsions laser à une intensité de quelques 1019 Wcm−2.
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Delair, Laurent. "Caractérisation de sources plasmas dédiées à la simulation de rentrées atmosphériques et au traitement de polluants : arc soufflé basse pression et décharge de polluants." Rouen, 2004. http://www.theses.fr/2004ROUES052.
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Ce travail de thèse est consacré à l’étude expérimentale de deux sources de plasmes : une torche de configuration originale (deux pieds d’arc anodiques) produisant un plasma d’azote à basse pression, et un arc glissant atmosphérique. Les caractéristiques thermodynamiques du plasma d’azote – densités et températures – sont déduites de l’analyse de son rayonnement par spectroscopie d’émission, depuis sa zone de création jusqu’à sa détente dans la veine d’essai. Des mesures du nombre de Mach sont également réalisées en sortie de torche. L’étude du comportement dynamique de cette source met en évidence l’existence d’une résonance acoustique de la chambre d’arc aux fluctuations de la densité électronique du plasma. L’analyse de l’arc glissant par les mêmes procédés révèle le fort déséquilibre du plasma dans sa zone de création et l’existence de phénomènes d’élargissement anormaux, signature d’une turbulence plasma. L’acquisition simultanée et à haute vitesse de ses caractéristiques électriques et radiatives confirme le scénario habituellement proposé pour sa dynamique : claquage, étirement, extinction. Elle met également en évidence le comportement impulsionnel de cet arc au cours de sa progression entre les électrodesThis work deals with the experimental study of two plasma sources : an original plasma torch (two anodic arc roots) which generates a low pressure nitrogen arcjet, and an atmospheric pressure gliding arc. The thermodynamic characteristics of the nitrogen plasma – densities and temperatures – are deduced from emission spectroscopy analysis, from its creation zone to its expansion zone. Mach number measurements are carried out at the torch exit. The study of the arc(s dynamic behaviour highlights an acoustic resonance frequency inside the arc chamber. The analysis of the gliding arc with emission spectroscopy reveals its non-equilibrium state and some abnormal ionic line broadenings in its creation zone due to plasma turbulence phenomena. Simultaneous high speed acquisitions of electrical signals and light intensity confirm its classical dynamical behaviour : ignition, lengthening, extinction. They also show the impulse behaviour of the arc column as it moves between the electrodes
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Delmas, Olivier. "Étude de la mise en forme temporelle d’impulsions laser de haute puissance pour l’excitation des sources laser X-UV sur la plateforme LASERIX." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS277/document.
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La présente thèse s’inscrit dans le cadre du développement des lasers X-UV générés en régime collisionnel transitoire et a pour objet principal d’étudier l’influence de la mise en forme temporelle des impulsions laser de haute puissance sur l’efficacité de génération de ces sources. Mon travail essentiellement expérimental a consisté à étudier de nouveaux schémas de pompage mettant en oeuvre différents dispositifs permettant de produire des préimpulsions et/ou un piédestal d’ASE au sein de la chaîne laser pilote. Dans ce manuscrit, je présente ces dispositifs et montre l’influence des différents paramètres laser sur l’efficacité de production du laser X-UV. L’étude expérimentale met tout d’abord en évidence une augmentation significative de l’énergie et de la durée de vie dela source laser X-UV en présence d’une préimpulsion.Dans ce contexte, un dispositif a été expérimenté permettant de générer au sein d’un unique faisceau laser, les deux principales impulsions précédées de la pré-impulsion, tout en gardant un contrôle sur leurs caractéristiques spectro-temporelles.Une approche alternative a été expérimentée dans laquelle un laser annexe « Q-switch » à bas coût est utilisé pour générer un plasma peu dense avecde faibles gradients de densité. Ce dernier dispositif a montré d’excellentes performances sur une large plage de longueur d’onde, et a été utilisé pour réaliser une expérience d’injection d’harmoniques d’ordre élevé, générées sur la voies econdaire à partir d’une cellule de gaz d’Argon.Une amélioration notable des caractéristiques spatiales et de la cohérence temporelle du laserX-UV a pu être observéeThe thesis fits within the framework ofsoft x-ray lasers (SXRL) development and has formain objective to study the influence of the temporal shaping of ultra-intense laser pulses, on the efficiency of SXRL generation. My thesiswork consisted in studying, designing and calibrating new pumping schemes through various devices based on the prepulse generation and/or an amount of ASE within the laser driver.In this manuscript, I study their influence on the SXRL generation efficiency by highlighting the optimization parameters such as the delay and the energy ratio between pulses, or the duration of each of them. The experimental study highlights first of all the influence of a prepulse on the SXRL generation efficiency. In the same framework, a device was experimented, allowing to generate within a single laser beam two mainpulses preceded by a prepulse, while maintaining a control over their spectro-temporalcharacteristics.An alternative approach was experimented in which an additional low cost « Q-Switch » lase rwas used to produce a under dense plasma presenting smooth electronic density gradients.This last device has showed excellent performances on a wide wavelength range andhas been used to perfom an experiment of highorder harmonic seeding generated from an Argongas cell on the secondary LASERIX beamline. A noteworthy improvement of the spatial characteristics and the temporal coherence of theSXRL have been observed
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Tortora, Alessandra. "Study and applications of the coherence properties of supercontinuum and high-order harmonic sources." Paris 6, 2006. http://www.theses.fr/2006PA066587.
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Takman, Per. "Compact Soft X-Ray Microscopy : Sources, Optics and Instrumentation." Doctoral thesis, Stockholm : Tillämpad fysik, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4342.
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Nickees, Sébastien. "Etude et développement d’une nouvelle source ECR produisant un faisceau intense d’ions légers." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112426/document.
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Cette thèse entre dans le cadre de l’étude et la conception d’une nouvelle source ECR d’ions légers au sein du LEDA (Laboratoire d’Etudes et de Développement des Accélérateurs – CEA Saclay), nommée ALISES (Advanced Light Ions Source Extraction System). Dans un premier temps, la conception magnétique, électrique et mécanique de la nouvelle source est décrite. Ensuite, des simulations ont été effectuées afin de déterminer la réduction du grossissement d’émittance en tenant compte de la réduction de la longueur de la LBE (Ligne Basse Energie) apportée par la source ALISES. Cette source permettant aussi de réaliser une étude sur les dimensions de la chambre plasma cylindrique, des simulations ont été effectuées afin de mieux comprendre l’interaction entre l’onde radiofréquence et le plasma. Par la suite, les expériences réalisées sur la source ALISES ont permis de mettre en évidence, de comprendre et de résoudre les problèmes de décharges Penning dans le tube accélérateur. Les mesures réalisées sur le plasma ont permis de dégager l’hypothèse que les électrons sont chauffés à l’entrée de la chambre plasma puis thermalisés sur toute sa longueur afin d’atteindre une énergie correspondante au maximum de la section efficace d’ionisation du dihydrogèneThis thesis is in the context of study and design of a new ECR light ion source on LEDA (Laboratory of Research and Development of Accelerators - CEA Saclay), named ALISES (Advanced Light Ions Source Extraction System). As a first step, the magnetic, electrical and mechanical design of the new source is described. Then, simulations were performed to determine the reduction of emittance growth taking into account the reduction of the length of the LBE (Low Energy Beam Line) provided by the source ALISES. With this source, it’s also possible to realize a study on the dimensions of the cylindrical plasma chamber. Simulations were performed to better understand the interaction between radiofrequency wave and plasma. Subsequently, experiments on the source ALISES helped highlight, understand and solve problems in the Penning discharges inside the accelerator column. Measurements performed on the plasma have yielded the assumption that the electrons are heated at the entrance of the plasma chamber and thermalized along its entire length to achieve an energy corresponding to the maximum of the ionization cross section for hydrogen
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Cornet, Marion. "Développement de sources térahertz intenses et applications en optique non-linéaire." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0194/document.
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Ces travaux de thèse portent sur l’étude de différents phénomènes non-linéaires ayantlieu dans le domaine térahertz (THz) au sein de cristaux de structure zinc-blende.En premier lieu, nous avons mis en place au laboratoire deux sources de rayonnementTHz intense, aux caractéristiques temporelles et spectrales bien distinctes. La premièrerepose sur le redressement optique d’une impulsion laser de durée femtoseconde dansun cristal de niobate de lithium, et la seconde est, quant à elle, basée sur la créationd’un plasma par focalisation d’un champ optique compos´e de l’impulsion fondamentalede pompe et de son second harmonique. Ces deux sources permettent de générer desondes THz dont l’amplitude est bien adaptée à la mise en oeuvre d’expériences d’optiquenon-linéaire.Nous avons ensuite caractérisé le comportement non-linéaire de cristaux de structurezinc-blende soumis à des champs THz intenses. Nous nous sommes ainsi intéressés àl’effet Pockels lors de l’interaction d’une impulsion THz intense et d’un champ optiquede faible intensité, dit sonde, au sein du matériau. Ceci nous a conduits à démontrerexpérimentalement et numériquement la possibilité de caractériser la phase spectrale del’impulsion sonde, à l’aide d’une technique équivalente au X-FROG. Nous avons égalementidentifié l’existence d’un processus non-linéaire dit de cascade, consistant en la générationde second harmonique induite par effet Pockels. Enfin, nous avons observé expérimentalementl’apparition d’un effet Kerr THz dans le cristal, nous permettant de déduire unevaleur moyenne de la susceptibilité non-linéaire du troisième ordre de ce matériau, `a l’aidede calculs théoriques et de simulations numériquesThis thesis project aims to study different non-linear processes in zinc-blende crystals,which take place in the terahertz (THz) range.First of all, two different light sources have been built in the laboratory, allowing us togenerate intense THz radiations with different temporal and spectral characteristics. Thefirst source is based on the optical rectification of a femtosecond laser pulse in a lithiumniobate crystal using the tilted pulse front technique, while the second one is based on aplasma, created through the focalization of a two-color femtosecond laser field. These twoTHz sources reach very high amplitudes, which allows us to study non-linear phenomenain the THz range.Among these, we have measured the non-linear behavior of zinc-blende crystals underintense THz radiation. We were particularly interested in the Pockels effect happeningduring the interaction of an intense THz field and a weak optical probe beam. This droveus to the experimental and numerical demonstration of a new method to characterize thespectral phase of the optical probe field. This method is equivalent to the X-FROG technique.We also identified a new non-linear phenomenon, consisting of the cascade of twosecond-order processes, namely the Pockels effect and the Second Harmonic Generation.Finally, we experimentally observed some THz Kerr effect in a gallium phosphide crystal,which allowed us to calculate an average value of its third-order non-linear susceptibility,thanks to theoretical considerations and simulations
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KOSTIOUKOV, IGOR. "Etude de l'interaction entre un champ intense et un plasma, application aux nouvelles sources de rayonnement." Paris 11, 1999. http://www.theses.fr/1999PA112296.
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Des progres recents dans les technologies micro-ondes et les laser de puissance, utilisant la compression de pulse par derive de frequence, permettent maintenant d'explorer le regime relativiste de l'interaction rayonnement-plasma. Ces progres motivent les etudes presentees dans cette these. Differentes etudes d'interactions entre un champ intense et une cible gazeuse sont ainsi developpees. Au niveau methodologique la mecanique hamiltonienne relativiste et la theorie des perturbations constituent les outils de base pour ces differentes etudes. Un nouveau theoreme reliant les perturbations du deuxieme ordre et les perturbations du premier ordre est demontre. Dans la limite des configurations champ particule unidimensionnelles non relativistes ce theoreme se reduit a la relation d'einstein. Au niveau phenomenologique plusieurs configurations d'interet pratique sont considerees. La probleme du chauffage stochastique dans les configurations de champs renverses est resolu et les applications aux decharges basses pression considerees. L'etude de l'absorption/emission collisionelle inverse en regime relativiste est aussi considere et le calcul des coefficients presente dans la limite des grands parametres d'impact. Sur la base de ces resultats la theorie cinetique du chauffage stochastique dans les configuration renversees est developpee. Afin d'etendre les etudes de rayonnement l'etude de l'emission/absorption en regime ultra intense est etendu au cas quantique et la serie infinie resomme pour permettre l'etude du scaling de ce processus. Dans un tel regime fortement non lineaire le couplage est fonction de la polarisation et les cas circulaires et rectilignes doivent etre consideres separement. Enfin un formalisme pour l'etude de l'interaction entre des solitons de langmuir et un faisceau d'electrons est presente.
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Lawrie, Scott. "Understanding the plasma and improving extraction of the ISIS Penning H⁻ ions source." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:1648761a-57b1-4d6f-8281-9d1c36ccd46a.
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A Penning-type surface-plasma negative hydrogen (H-) ion source has been delivering beam at the ISIS pulsed spallation neutron and muon facility for over thirty years. It is one of the most powerful and well-renowned H- sources in the world. Although long-term experience has allowed the source to be operated reliably and set up in a repeatable way, it is treated as something of a 'black box': the detailed plasma physics of why it works has always been unclear. A vacuum Vessel for Extraction and Source Plasma Analyses (VESPA) has been developed to understand the ISIS ion source plasma and improve the beam extracted from it. The VESPA ion source is operated in a completely new regime whereby the analysing sector dipole magnet housed inside a refrigerated 'cold box', presently used on ISIS, is replaced by an on-axis extraction system. The new extraction system incorporates a novel einzel lens with an elliptical aperture. This is the first demonstration of an elliptical einzel being used to focus an asymmetric H- ion beam. With the dipole magnet removed, the ion source has been shown to produce 85 mA of H- beam current at normal settings; of which 80 mA is transported through the new einzel lens system, with a normalised RMS emittance of 0.2 π mm mrad. Optical emission spectroscopy measurements have shown a plasma density of 1019 mâ3, an H2 dissociation rate of 70%, an almost constant electron temperature of 3.5 eV and an atomic temperature which linearly increases above the electron temperature. In support of these principal measurements, rigorous particle tracking, electrostatic and thermal simulations were performed. In addition, a suite of new equipment was manufactured by the author. This includes a fast pressure gauge, a temperature controller, a high voltage einzel lens circuit, a fast beam chopper and a caesium detection system.