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1
Bernath, Robert Thomas. "High-Intensity Ultra-Fast Laser Interaction Technologies". Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2173.
Testo completoAbstract (sommario):
To our knowledge this is the first comprehensive study of laser-induced effects generated at intermediate distances using self-channeled femtosecond laser pulses. Studies performed were made both experimentally and theoretically with the use of novel modeling techniques. Peak laser pulse powers above 3 GW allow beam propagation without divergence for up to several kilometers. In this regime, experiments were performed at 30 meters from the laser system in a custom propagation and target range, utilizing the Laser Plasma Laboratory's Terawatt laser system. Experiments included investigations of laser ablation; electromagnetic pulsed (EMP) radiation generation over the 1-18 GHz region; shockwave formation in air and solid media; optical coupling of channeled pulses into transparent media; and, conservation of energy in these interactions. The use of bursts of femtosecond pulses was found to increase the ablation rate significantly over single-pulse ablation in both air and vacuum. EMP generation from near-field focused and distance-propagated pulses was investigated. Field strengths upwards of 400 V/m/[Lambda] for vacuum focusing and 25 V/m/[Lambda] for self-channeled pulses were observed. The total field strengths over 1-18 GHz measured at distance surpassed 12 kV/m. Shockwaves generated in transparent media at 30 meters were observed as a function of time. It was found that the interaction conditions control the formation and propagation of the shock fronts into the medium. Due to the processes involved in self-channeling, significant fractions of the laser pulse were coupled into the target materials, resulting in internal optical and exit-surface damage. Basic estimations on the conservation of energy in the interaction are presented. The results of the experiments are supported by hydrodynamic plasma physics code and acoustic modeling.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD
2
Flacco, Alessandro. "Experimental study of proton acceleration with ultra-high intensity, high contrast laser beam". École polytechnique, 2010. http://www.theses.fr/2008EPXX0071.
Testo completoAbstract (sommario):
La production de faisceaux énergétiques d'ions/protons avec des impulsions laser à intensités relativistes (I>10^{18}W/cm^2) a reçu, au cours des dernières années, un intérêt croissant parmi les scientifiques travaillant dans les domaines de l'optique, de la physique des plasmas et des accélérateurs. Une fraction des électrons est chauffée à haute température lors de l'interaction entre une impulsion laser femtoseconde et un plasma surdense. Les ions et les protons sont extraits et accélérés par la séparation de charge qui est produite pendant l'expansion du plasma. Les résultats présentés dans ce manuscrit décrivent la réalisation d'expériences d'accélération d'ions avec un système laser à haute puissance et à haut contraste (XPW). Deux expériences préparatoires sont réalisées, afin d'étudier l'interaction entre le piédestal d'une impulsion laser et une cible. L'expansion d'un plasma créé par laser à intensité moyenne est mesurée par interférométrie; l'évolution de la longueur de son gradient de densité est déduite par les cartes de densité électronique, mesurées à différents instants. La variation de la réflectivité absolue d'une cible mince d'aluminium est mise en corrélation avec la température électronique afin de contrôler le débouché du choc produit par le laser. La corrélation entre les deux expériences est finalement utilisée pour définir le conditions optimales pour l'accélération des protons. Des expériences d'accélération de protons avec un laser à haut contraste, la construction et la validation d'un spectromètre (Galette a Micro-canaux et Parabole Thomson), ainsi que des autres détails sur le montage sont présentés. Les résultats ainsi obtenus montrent que l'amélioration du contraste permet d'utiliser des cibles plus minces et de produire des conditions d'interaction plus stables et contrôlables. Des faisceaux des protons ayant énergie cinétique supérieure à 4MeV sont produits, avec une stabilité tir à tir meilleure de 4% rms. L'accélération des protons avec deux impulsions laser confirme que l'absorption d'énergie laser est augmentée dans le cas des cibles pre-chauffées par une impulsion laser avec les bons paramètresThe production of energetic proton/ion beams with laser pulses at relativistic intensities (I>10^{18}W/cm^2) has received, in the past few years, increasing interest from the scientific community in plasma, optics and accelerator physics. A fraction of electrons is heated to high temperature during the ultrafast interaction between a femtosecond laser pulse and an overdense plasma. Ions and protons are extracted and accelerated by the charge separation set up during the expansion of the plasma. The results presented in this manuscript report on the realization of ion acceleration experiments using a high contrast (XPW) multi-terawatt laser system. Two preparatory experiments are set up, aiming to study the pedestal of a laser pulse interacting with the target. The expansion of a plasma created by a laser at moderate intensity is measured by interferometry; the evolution of the density gradient length is deduced from the electron density maps at different moments. The variation of the absolute reflectivity of a thin aluminium foil is correlated to the electron temperature and is used to monitor the arrival time of the laser produced shock. The crossing between the two experiments is finally used to define the optimum condition for proton acceleration. Proton acceleration experiments with high contrast laser are reported, including the construction and the validation of a real-time, single shot ion spectrometer (Micro-channel Plate and Thomson Parabola), and other details of the realised setup. The obtained results show that the increased contrast enables the use of thinner targets and the production of more stable and controllable interaction conditions. Proton beams with kinetic energy higher than 4 MeV are produced, with a shot-to-shot stability better than 4% rms. Proton acceleration experiment with two laser beams confirms that the laser energy absorption is enhanced when the target is pre-heated by a laser pulse with proper parameters
3
Flacco, A. "Experimental Study of Proton Acceleration with Ultra-High Intensity, High Contrast Laser Beam". Phd thesis, Ecole Polytechnique X, 2008. http://pastel.archives-ouvertes.fr/pastel-00005616.
Testo completoAbstract (sommario):
La production de faisceaux énergétiques d'ions/protons avec des impulsions laser à intensités relativistes (I>10^{18}W/cm^2) a reçu, au cours des dernières années, un intérêt croissant parmi les scientifiques travaillant dans les domaines de l'optique, de la physique des plasmas et des accélérateurs. Une fraction des électrons est chauffée à haute température lors de l'interaction entre une impulsion laser femtoseconde et un plasma surdense. Les ions et les protons sont extraits et accélérés par la séparation de charge qui est produite pendant l'expansion du plasma. Les résultats présentés dans ce manuscrit décrivent la réalisation d'expériences d'accélération d'ions avec un système laser à haute puissance et à haut contraste (XPW). Deux expériences préparatoires sont réalisées, afin d'étudier l'interaction entre le piédestal d'une impulsion laser et une cible. L'expansion d'un plasma créé par laser à intensité moyenne est mesurée par interférométrie; l'évolution de la longueur de son gradient de densité est déduite par les cartes de densité électronique, mesurées à différents instants. La variation de la réflectivité absolue d'une cible mince d'aluminium est mise en corrélation avec la température électronique afin de contrôler le débouché du choc produit par le laser. La corrélation entre les deux expériences est finalement utilisée pour définir le conditions optimales pour l'accélération des protons. Des expériences d'accélération de protons avec un laser à haut contraste, la construction et la validation d'un spectromètre (Galette a Micro-canaux et Parabole Thomson), ainsi que des autres détails sur le montage sont présentés. Les résultats ainsi obtenus montrent que l'amélioration du contraste permet d'utiliser des cibles plus minces et de produire des conditions d'interaction plus stables et contrôlables. Des faisceaux des protons ayant énergie cinétique supérieure à 4MeV sont produits, avec une stabilité tir à tir meilleure de 4% rms. L'accélération des protons avec deux impulsions laser confirme que l'absorption d'énergie laser est augmentée dans le cas des cibles pre-chauffées par une impulsion laser avec les bons paramètres.
4
Chen, Sophia Nan. "X-ray spectroscopy of buried layer foils irradiated with an ultra high intensity short pulse laser". Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3352706.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed June 16, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 117-126).
5
Debayle, Arnaud. "Theoretical study of Ultra High Intensity laser-produced high-current relativistic electron beam transport through solid targets". Thesis, Bordeaux 1, 2008. http://www.theses.fr/2008BOR13708/document.
Testo completoAbstract (sommario):
Cette thèse porte sur l’étude théorique du transport d’un faisceau intense d’électrons relativistes dans une cible solide. Dans la première partie nous présentons les interprétations théoriques d’une partie des résultats d’une campagne d’expérience portant sur la production et le transport d’électrons relativistes dans une cible d’aluminium. Nous y démontrons la prédominance des e?ets collectifs sur les e?ets collisionels dans la première dizaine de microns de propagation grâce à des modèles de transports déjà existant au début de cette thèse. Ces modèles deviennent insu?sants dans le cas du transport de faisceau dans un isolant. Aussi, dans la deuxième partie, nous présentons un modèle de propagation du faisceau d’électrons relativistes dans un diélectrique incluant l’e?et de l’ionisation de la cible par le faisceau. Nous y quanti?ons les pertes d’énergies des électrons en fonction des paramètres du faisceau et du milieu environnant, et nous démontrons l’existence d’un régime de propagation pour lequel les électrons du plasma ne sont pas à l’équilibre thermodynamique local avec les ions. Ces résultats ont été comparés et con?rmés avec un code cinétique qui prend en compte l’ionisation par champ électrique et par collisions entre les électrons du plasma et les ions. Nous avons examiné la stabilité du faisceau et montré que ce dernier pouvait exciter deux types d’instabilités transverses sur des longueurs de propagation de l’ordre de 30 à 300 µm en fonction de la taille de la perturbationThis PhD thesis is a theoretical study of high-current relativistic electron beam transport through solid targets. In the ?rst part, we present an interpretation of a part of experimental results of laser– produced electron beam transport in aluminium foil targets. We have estimated the fast electron beam characteristics and we demonstrated that the collective e?ects dominate the transport in the ?rst tens of µm of propagation. These quantitative estimates were done with the transport models already existing at the beginning of this thesis. These models are no longer su?cient in the case a fast electron beam propagation in insulator targets. Thus, in the second part, we have developed a propagation model of the beam that includes the e?ects of electric ?eld ionization and the collisional ionization by the plasma electrons. We present estimates of the electron energy loss induced by the target ionization, and we discuss its dependence on the beam and target parameters. In the case of a relatively low fast electron density, we demonstrated that the beam creates a plasma where the electons are not in a local thermodynamic equilibrium with ions. We have examined the beam stability and we demonstrated that transverse instabilities can be excited by the relativistic electron beam over the propagation distances of 30 - 300 µm depending on the perturbation wavelength
6
Moulanier, Ioaquin. "Modélisation réaliste de l'accélération laser-plasma". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP173.
Testo completoAbstract (sommario):
L'interaction d'un laser intense et court avec un plasma peu dense permet de créer de forts gradients de champ électrique se propageant dans le sillage du laser et de piéger des électrons du plasma qui atteignent des énergies ultra-relativistes. L'interaction d'un faisceau laser d'intensité supérieure à 10 puissance 18 Watt par centimètre carré est non-linéaire, et les caractéristiques spatio-temporelles du laser évoluent au cours de sa propagation dans le plasma.La numérisation de la distribution transverse du laser mesurée expérimentalement, et la prise en compte de la phase spectrale permettent de décrire les imperfections laser pour mieux rendre compte de la physique de l'interaction et reproduire les propriétés des faisceaux d'électrons mesurés.Le développement d'outils numériques de reconstruction de la distribution laser, leur intégration dans des simulations particulaires, ont permis d'atteindre un meilleur accord entre les diagnostics numériques de fin de simulation et les diagnostics expérimentaux du spectre des électrons.L'algorithme de reconstruction de la distribution laser transverse est présenté, ainsi que son intégration à un code particulaire en géométrie 3D quasi-cylindrique. Des exemples montrent l'impact de l'asymétrie transverse de la distribution laser en régime d'interaction non-linéaire dans le cadre de simulations caractérisant des expériences d'accélération laser-plasma menées en salle longue focale de l'installation laser APOLLON, ainsi qu'au Lund Laser CentreThe interaction of a short laser pulse with an underdense plasma generates strong electric field gradients in the laser beam wake, trapping electrons of the plasma and accelerating them to ultra-relativistic energies. For laser peak intensities above 10 to the power 18 Watt per squared centimeter, the process is non-linear, and the spatiotemporal laser characteristics evolve during its propagation in the plasma.The modeling of the laser transverse distribution measured in experiment, together with its spectral phase,is used to describe the imperfections of the laser and improve the accuracy of the description of the mechanisms during interaction and the resulting electron bunch properties. Numerical tools were developped for the reconstruction of the laser distribution and its integration in particle-in-cell simulations, allowing us to achieve a better agreement between numerical diagnostics and experimental measurements of the electron spectra.The reconstruction algorithm of the laser distribution is introduced, as well as its integration in a quasi-3D particle-in-cell code. Specific examples show the impact of the laser distribution transverse asymmetry in the non-linear interaction regime through simulations that reproduce accurately laser-plasma acceleration experiments performed in the long-focal area of the APOLLON laser facility and at the Lund Laser Centre
7
Carrié, Michaël. "Accélération de protons par laser à ultra-haute intensité : étude et application au chauffage isochore". Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00608050.
Testo completoAbstract (sommario):
L'interaction d'impulsions lasers brèves et intenses avec un plasma est une source intéressante d'ions énergétiques. Les travaux effectués au cours de cette thèse s'articulent autour de deux grandes thématiques : la production de protons par laser, et leur utilisation pour le chauffage isochore, avec, pour principal outil d'étude, la simulation à l'aide de codes numériques (cinétique particulaire et hydrodynamique). Dans un premier temps, nous avons étudié le comportement de l'énergie cinétique maximale des protons qu'il est possible d'accélérer avec le mécanisme du Target Normal Sheath Acceleration (TNSA), en régime sub-ps, en fonction de différents paramètres, notamment de la durée d'impulsion laser. Nous avons montré que l'allongement de la durée d'impulsion, à énergie laser constante, est responsable du préchauffage et de la détente du plasma avant l'arrivé du pic d'intensité. Les gradients de densité ainsi produits (face avant et face arrière) peuvent favoriser, ou au contraire pénaliser, le gain en énergie cinétique des protons. Les résultats obtenus ont servi à l'interprétation d'une étude expérimentale réalisée au Laboratoire d'Optique Appliquée. Nos efforts se sont ensuite concentrés sur l'élaboration d'un modèle semi-analytique rendant compte de l'énergie cinétique maximale des protons accélérés par le biais du TNSA. Ce modèle permet de retrouver l'ordre de grandeur des intensités nécessaires, de l'ordre de 6x1021 W/cm², pour atteindre des énergies de proton supérieures à 150 MeV avec des impulsions laser de quelques joules et plusieurs dizaines de fs. Dans la dernière partie de cette thèse, nous nous sommes intéressés à l'utilisation de ces faisceaux de protons pour le chauffage isochore. Nous avons caractérisé, dans un premier temps, les fonctions de distribution produites par des cibles composées d'un substrat lourd (A >> 1) sur la face arrière duquel est déposé un plot d'hydrogène (schéma d'Esirkepov). Ensuite, à partir de simulations hydrodynamiques, nous avons étudié le temps caractéristique de détente de la cible chauffée en modifiant des paramètres tels que la distance à la source de protons, l'intensité et la tache focale du laser, et la densité surfacique du plot. Nous avons enfin étendu cette étude aux cibles cylindriques et nous avons montré qu'il est possible de réduire les effets liés à la divergence naturelle du faisceau de protons et ainsi d'obtenir des températures plus élevées.
8
Kallala, Haithem. "Massively parallel algorithms for realistic PIC simulations of ultra high intensity laser-plasma interaction, application to attosecond pulses separation of Doppler harmonics". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS052.
Testo completoAbstract (sommario):
La complexité des mécanismes physiques mis en jeu lors de l'interaction laser-plasma à ultra-haute intensité nécessite de recourir à des simulations PIC particulièrement lourdes. Au cœur de ces codes de calcul, les solveurs de Maxwell pseudo-spectraux d'ordre élevé présentent de nombreux avantages en termes de précision numérique. Néanmoins, ces solveurs ont un coût élevé en termes de ressources nécessaires. En effet, les techniques de parallélisation existantes pour ces solveurs sont peu performantes au-delà de quelques milliers de coeurs, ou induisent un important usage mémoire, ce qui limite leur scalabilité à large échelle. Dans cette thèse, nous avons développé une toute nouvelle approche de parallélisation qui combine les avantages des méthodes existantes. Cette méthode a été testée à très large échelle et montre un scaling significativement meilleur que les précédentes techniques, tout en garantissant un usage mémoire réduit.En capitalisant sur ce travail numérique, nous avons réalisé une étude numérique/théorique approfondie dans le cadre de la génération d'harmoniques d'ordres élevés sur cible solide. Lorsqu'une impulsion laser ultra-intense (I>10¹⁶W.cm⁻² ) et ultra-courte (de quelques dizaines de femtosecondes) est focalisée sur une cible solide, elle génère un plasma sur-dense, appelé miroir plasma, qui réfléchit non-linéairement le laser incident. La réflexion de l'impulsion laser est accompagnée par l'émission cohérente d'harmoniques d'ordres élevées, sous forme d'impulsions X-UV attosecondes (1 attosecond = 10⁻¹⁸s). Pour des intensités laser relativistes (I>10¹⁹ W.cm⁻²), la surface du plasma est incurvée sous l'effet de la pression de radiation du laser. De ce fait, les harmoniques rayonnées par la surface du plasma sont focalisées. Dans cette thèse, j'ai étudié la possibilité de produire des impulsions attosecondes isolées en régime relativiste sur miroir plasma, grâce au mécanisme de phare attoseconde. Celui-ci consiste à introduire une rotation des fronts d'onde du laser incident de façon à séparer angulairement les différentes impulsions attosecondes produites à chaque cycle optique. En régime relativiste, la courbure du miroir plasma augmente considérablement la divergence du faisceau harmonique, ce qui rend le mécanisme phare attoseconde inefficace. Pour y remédier, j'ai développé deux techniques de réduction de divergence harmonique afin de mitiger l'effet de focalisation induit par la courbure du miroir plasma et permettre de générer des impulsions attosecondes isolées à partir d’harmoniques Doppler. Ces deux techniques sont basées sur la mise en forme en amplitude et en phase du faisceau laser. Par ailleurs, j'ai développé un modèle théorique pour déterminer les régimes optimaux d'interaction afin de maximiser la séparation angulaire des impulsions attosecondes. Ce modèle a été validé par des simulations numériques PIC en géométries 2D et 3D et sur une large gamme de paramètres laser et plasma. Finalement, on montre qu'en ajustant des paramètres laser et plasma réalistes, il est possible de séparer efficacement les impulsions attosecondes en régime relativisteThe complexity of the physical mechanisms involved in ultra-high intensity laser-plasma interaction requires the use of particularly heavy PIC simulations. At the heart of these computational codes, high-order pseudo-spectral Maxwell solvers have many advantages in terms of numerical accuracy. This numerical approach comes however with an expensive computational cost. Indeed, existing parallelization methods for pseudo-spectral solvers are only scalable to few tens of thousands of cores, or induce an important memory footprint, which also hinders the scaling of the method at large scales. In this thesis, we developed a novel, arbitrarily scalable, parallelization strategy for pseudo-spectral Maxwell's equations solvers which combines the advantages of existing parallelization techniques. This method proved to be more scalable than previously proposed approaches, while ensuring a significant drop in the total memory use.By capitalizing on this computational work, we conducted an extensive numerical and theoretical study in the field of high order harmonics generation on solid targets. In this context, when an ultra-intense (I>10¹⁶W.cm⁻²) ultra-short (few tens of femtoseconds) laser pulse irradiates a solid target, a reflective overdense plasma mirror is formed at the target-vacuum interface. The subsequent laser pulse non linear reflection is accompanied with the emission of coherent high order laser harmonics, in the form of attosecond X-UV light pulses (1 attosecond = 10⁻¹⁸s). For relativistic laser intensities (I>10¹⁹ W.cm⁻²), the plasma surface is curved under the laser radiation pressure. And the plasma mirror acts as a focusing optics for the radiated harmonic beam. In this thesis, we investigated feasible ways for producing isolated attosecond light pulses from relativistic plasma-mirror harmonics, with the so called attosecond lighthouse effect. This effect relies introducing a wavefront rotation on the driving laser pulse in order to send attosecond pulses emitted during different laser optical cycles along different directions. In the case of high order harmonics generated in the relativistic regime, the plasma mirror curvature significantly increases the attosecond pulses divergence and prevents their separation with the attosecond lighthouse scheme. For this matter, we developed two harmonic divergence reduction techniques, based on tailoring the laser pulse phase or amplitude profiles in order to significantly inhibit the plasma mirror focusing effect and allow for a clear separation of attosecond light pulses by reducing the harmonic beam divergence. Furthermore, we developed an analytical model to predict optimal interaction conditions favoring attosecond pulses separation. This model was fully validated with 2D and 3D PIC simulations over a broad range of laser and plasma parameters. In the end, we show that under realistic laser and plasma conditions, it is possible to produce isolated attosecond pulses from Doppler harmonics
9
Ramirez, Lourdes Patricia. "Few-cycle OPCPA laser chain". Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00806245.
Testo completoAbstract (sommario):
The Apollon-10 PW laser chain is a large-scale project aimed at delivering 10 PW pulses to reach intensities of 10^22 W/cm^2. State of the art, high intensity lasers based solely on chirped pulse amplification (CPA) and titanium sapphire (Ti:Sa) crystals are limited to peak powers reaching 1.3 PW with 30-fs pulses as a result of gain narrowing in the amplifiers. To access the multipetawatt regime, gain narrowing can be suppressed with an alternative amplification technique called optical parametric chirped pulse amplification (OPCPA), offering a broader gain bandwidth and pulse durations as short as 10 fs. The Apollon-10 PW laser will exploit a hybrid OPCPA-Ti:Sa-CPA strategy to attain 10-PW pulses with 150 J and 15 fs. It will have two high-gain, low-energy amplification stages (10 fs ,100 mJ range) based on OPCPA in the picosecond and nanosecond timescale and afterwards, and will use Ti:Sa for power amplification to the 100-Joule level.Work in this thesis involves the progression of the development on the Apollon-10 PW front end and is focused on the development of a high contrast, ultrashort seed source supporting 10-fs pulses, stretching these pulses prior to OPCPA and the implementation of the picosecond OPCPA stage with a target of achieving 10-mJ pulses and maintaining its bandwidth. To achieve the final goal of 15-fs, 150-J pulses, the seed source must have a bandwidth supporting 10-fs and a temporal contrast of at least 10^10. Thus from an initial commercial Ti:Sa source delivering 25-fs pulses with a contrast of 10^8, spectral broadening via self-phase modulation and contrast enhancement with cross polarized (XPW) generation was performed. Subsequently, the seed pulses were stretched to a few picoseconds to match the pump for picosecond OPCPA. Strecher designs using an acousto-optic programmable dispersive filter (dazzler) for phase control in this purpose are studied. A compact and straightforward compressor using BK7 glass is used and an associated compressor for pulse monitoring was also studied. Lastly, the picosecond OPCPA stage was implemented in single and dual stage configurations.
10
Sutherland, Julia Robin Miller. "Phase-Matching Optimization of Laser High-Order Harmonics Generated in a Gas Cell". Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd880.pdf.
Testo completo
11
Leblanc, Adrien. "Miroirs et réseaux plasmas en champs lasers ultra-intenses : génération d’harmoniques d’ordre élevé et de faisceaux d’électrons relativistes". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS384/document.
Testo completoAbstract (sommario):
Lors de la focalisation d’un laser femtoseconde ultra-intense [I>10¹⁶W/cm²] sur une cible solide, dès le début de l’impulsion le champ laser est suffisant pour totalement ioniser la surface de la cible. Le reste de l’impulsion est ensuite réfléchi dans la direction spéculaire par le plasma dense ainsi créé : c’est un miroir plasma. Le champ laser ultra-intense peut accélérer les électrons au sein du plasma à des vitesses relativistes. Certains sont éjectés vers le vide et ces miroirs plasmas sont ainsi des sources de faisceaux d’électrons énergétiques. De plus, ils rayonnent dans l’extrême ultra-violet (XUV) à chaque période laser, ce qui se traduit par de la génération d’harmoniques d’ordre élevé de la pulsation laser. L’objectif de cette thèse est de mieux comprendre l’interaction laser-plasma sur miroirs plasmas à l’aide de la caractérisation de ces deux observables physiques qui en sont issues : les faisceaux d’électrons relativistes et les faisceaux d’harmoniques d’ordre élevé. Une première partie traite de la mesure des faisceaux harmoniques. Du fait des conditions physiques extrêmes d’interaction, la détection ne peut se faire qu’à une distance macroscopique de la cible. Ainsi la caractérisation des propriétés angulaires de ces faisceaux (réalisée en fonction des conditions d’interaction au cours de travaux précédents) ne fournit que des informations partielles sur l’interaction en elle-même. La ptychographie, une technique de mesure par diffraction cohérente où une sonde est diffractée par un objet, est ici transposée à la génération d’harmoniques sur miroirs plasmas grâce à la micro-structuration optique du plasma à la surface de la cible. Les champs sources harmoniques sont ainsi reconstruits en amplitude et en phase spatiales directement dans le plan cible. Grâce à ces mesures dans différentes conditions d’interaction, des modèles théoriques analytiques d’interaction en régime non relativiste [I<10¹⁸W/cm²] et relativiste [I>10¹⁸W/cm²] développés précédemment sont validés expérimentalement. Une seconde partie de cette thèse est consacrée à l’étude expérimentale des propriétés angulaires et en énergie des faisceaux d’électrons relativistes issus des miroirs plasmas. Une étude théorique et numérique, permet de prouver que ces mesures sont la première observation claire de l’accélération d’électrons relativistes par laser dans le vide (VLA). Enfin, l’étude simultanée des efficacités de génération des faisceaux d’électrons et d’harmoniques montre une corrélation nette entre les deux processus en régime relativisteWhen focusing an ultra-intense femtosecond laser pulse [I>10¹⁶W/cm²] onto a solid target, this target is ionized at the very beginning of the laser pulse. The resulting dense plasma then reflects the laser in the specular direction: it is a plasma mirror. The ultra-intense laser field can accelerate electrons within the plasma at relativistic speeds. Some are ejected towards the vacuum and these plasma mirrors are therefore sources of relativistic electron beams. Moreover, at each optical cycle they radiate in the form of extreme ultraviolet light, resulting in the generation of high-order harmonics of the laser frequency (HHG). The objective of this PhD is to understand laser-plasma interaction though the characterization of high-order harmonics and relativistic electron beams generated from plasma mirrors. The first part deals with harmonic beam measurement. Due to the extreme physical conditions during the interaction, detection can only be performed at macroscopic distance from target. Thus, the characterization of the harmonic beams’ angular properties (carried out as a function of interaction conditions in previous works) only provides partial information on the interaction itself. A technique of coherent diffraction imaging, named ptychography, which consists of diffracting a probe onto an object, is transposed to HHG on plasma mirrors by optically micro-structuring the plasma on a target surface. Harmonic fields are then reconstructed spatially in amplitude and phase directly in the target plane. Thanks to this measurement in different interaction conditions, previously developed theoretical analytical models in non-relativistic regime [I<10¹⁸W/cm²] and relativistic regime [I>10¹⁸W/cm²] are experimentally validated. The second part of the PhD is dedicated to the experimental characterization of angular and spectral properties of relativistic electron beams. A theoretical and numerical study shows that this constitutes the first clear observation of vacuum laser acceleration (VLA). Finally, a simultaneous study of harmonic and electron signals highlights a strong correlation between both processes in the relativistic regime
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Chopineau, Ludovic. "Physique attoseconde relativiste sur miroirs plasmas". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS132/document.
Testo completoAbstract (sommario):
Lors de la réflexion d’un laser femtoseconde ultra-intense [Iʟ > 10¹⁶ W/cm²] sur une cible solide, celle-ci est ionisée dès les premiers cycles de l’impulsion. Un plasma se détend alors vers le vide avec un profil exponentiel de longueur caractéristique Lg. Pour de faibles longueurs de gradient Lg < λʟ, le gradient plasma est considéré comme raide, il réfléchit spéculairement l’impulsion incidente : c’est un miroir plasma. De tels plasmas, réfléchissant pour la lumière, sont aujourd’hui exploités dans différentes applications scientifiques, comme l’accélération de particules par laser ou encore la génération d’harmoniques d’ordre élevé, associées dans le domaine temporel à un train d’impulsions attosecondes. Néanmoins, pour favoriser ces émissions de lumière ou de particules, le transfert d’énergie entre l’impulsion laser incidente et le plasma est essentiel. L’objectif de cette thèse est de mieux comprendre ces interactions à l’aide de la caractérisation de ces deux observables physiques qui en sont issues : les émissions d’électrons relativistes et d’harmoniques d’ordre élevé. Tout d’abord, nous reportons dans ce manuscrit la première étude expérimentale et numérique détaillée des mécanismes de couplage laser-plasma dense impliqués en régime relativiste [Iʟ > 10¹⁸ W/cm²] en fonction notamment de la longueur caractéristique de gradient Lg. Cette étude a notamment permis d’identifier deux régimes distincts en fonction des conditions d’interaction, éclaircissant ainsi la physique régissant ces systèmes. Par ailleurs, au delà de cet aspect fondamental, le contrôle de ces sources est également essentiel pour de futures expériences. Pour cela, différentes approches permettant de mettre en forme spatialement et temporellement ces impulsions de lumière ultra-brèves ont été étudiées au cours de ce doctorat, ouvrant ainsi de nouvelles perspectives pour l’utilisation de ces sources. En particulier, nous démontrons qu’il est possible d’introduire un moment angulaire orbital aux impulsions XUV attosecondes via la mise en forme spatiale du faisceau IR femtoseconde incident ou bien de plasma dense créé à la surface de la cible mais également de contrôler la dynamique des électrons de surface du plasma à l’échelle attoseconde à l’aide d’un champ incident à deux couleurs. Finalement, une méthode novatrice basée sur des mesures de ptychographie dynamique a été développée afin de caractériser spatio-temporellement ces impulsions de lumière ultra-brèves, constituant un enjeu majeur pour la communautéWhen an ultra-intense femtosecond laser beam [Iʟ > 10¹⁶ W/cm²] is focused on a solid target, the surface becomes completely ionized during the first optical cycles of the laser pulse. Due to their solid-like density and to their limited expansion into the vacuum such plasmas specularly reflect these pulses, just like ordinary mirrors do for low intensity. These plasmas are now used in many scientific applications like particle acceleration by laser light as well as high-order harmonic generation, associated to a train of attosecond pulses in the time domain. Nevertheless, to favor these emissions of light or particle, the energy transfert between the incident field and the dense plasma is crucial. The aim of this thesis is to better understand these interactions through the characterization of high-order harmonics and relativistic electron beams generated on plasma mirrors. We reported in this manuscript the first detailed experimental and numerical study of the coupling mechanisms involved between an ultra-intense laser light [Iʟ > 10¹⁸ W/cm²] and a dense plasma, and more specifically as a function of the gradient scale length Lg. These results enabled to identify two different regimes, clarifying some physical issues. Furthermore, beyond these fondamental aspects, the control of these sources is essential, particularly for futures pump-probe experiments or new spectroscopies. For that, several approaches have been studied to temporally and spatially shape these ultra-short light pulses, thus opening up new perspectives for these sources. We demonstrate in particular the generation of intense XUV vortex beam either by spatially shaping the incident IR field or the dense plasma created at the target surface as well as controlling the electron dynamics on the attosecond time scale with relativistic two-color waveforms. Finally, an innovative method based on in-situ ptychographic measurements has been developed to simultaneously characterize in time and space these ultrashort XUV light pulses, constituting one of the major challenges of the community
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Comley, Andrew James. "High intensity laser interactions with liquid microdroplets". Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252017.
Testo completo
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Kingham, Robert Joseph. "High intensity short-pulse laser-plasma interactions". Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267882.
Testo completo
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Faldon, Mary Eileen. "A high intensity, short pulse neodymium laser". Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322326.
Testo completo
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Harvey, Christopher. "Electron dynamics in high-intensity laser fields". Thesis, University of Plymouth, 2010. http://hdl.handle.net/10026.1/301.
Testo completoAbstract (sommario):
We consider electron dynamics in strong electromagnetic fields, such as those expected from the next generation of high-intensity laser facilities. Beginning with a review of constant classical fields, we demonstrate that the electron motion (as given by the Lorentz force equation) can be divided into one of four Lorentz invariant cases. Parameterising the field tensor in terms of a null tetrad, we calculate the radiative energy spectrum for an electron in crossed fields. Progressing to an infinite plane wave, we demonstrate how the electron orbit in the average rest frame changes from figure-of-eight to circular as the polarisation changes from linear to circular. To move beyond a plane wave one must resort to numerics. We therefore present a novel numerical formulation for solving the Lorentz equation. Our scheme is manifestly covariant and valid for arbitrary electromagnetic field configurations. Finally, we reconsider the case of an infinite plane wave from a strong field QED perspective. At high intensities we predict a substantial redshift of the usual kinematic Compton edge of the photon emission spectrum, caused by the large, intensity dependent effective mass of the electrons inside the laser beam. In addition, we find that the notion of a centre-of-mass frame for a given harmonic becomes intensity dependent.
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Spence, David James. "Plasma waveguides for high-intensity laser pulses". Thesis, University of Oxford, 2001. http://ora.ox.ac.uk/objects/uuid:40234134-8f2c-4ddb-809a-c60870987f90.
Testo completoAbstract (sommario):
This thesis documents the development of plasma waveguides for high-intensity laser pulses. Initial work concentrated on the development of the discharge-ablated capillary waveguide, based on the work of A. Zigler (Zigler, A., Y. Ehrlich, C. Cohen, J. Krall and P. Sprangle, J. Opt. Soc. Am. B 13, 68). The waveguide was shown to be capable of guiding picosecond laser pulses with an intensity of 1016 W cm-2 over a length of 10 mm. The pulse energy transmission of the capillary was increased from 48% to 70% when the discharge was fired. An interferometry-based measurement technique was developed, allowing measurement of the electron density profile formed in the capillary waveguide. These measurements were used as input to a numerical simulation that predicted the propagation of intense laser pulses through partially-ionised plasma waveguides. Numerical simulations accurately reproduced the picosecond pulse guiding results, and gave important insights into the properties and severe drawbacks of partially-ionised waveguides. Previous work on partially-ionised plasma waveguides has not fully explored the implications of the propagation of intense pulses through the partially-ionised plasma. For polypropylene waveguides, it was shown that for pulses with an intensity of 1016 W cm-2, the waveguide is not capable of high-quality guiding. However, for pulses with an intensity of greater than 1017 W cm-2, high-quality guiding is predicted through the partially-ionised waveguide in a new regime called "quasi-matched guiding". A novel gas-filled capillary discharge waveguide was designed and built. The device was shown to form a guiding channel inside a capillary pre-filled with gas. Interferometry measurements of the electron density profile formed in a hydrogen-filled capillary discharge waveguide showed that an approximately parabolic plasma waveguide could be formed in an essentially fully-ionised hydrogen plasma. The device was used to guide femtosecond laser pulses, with an intensity of 1017 W cm-2, over distances of 20 and 40 mm, with a pulse energy transmission of 92% and 82% respectively. For the 20 mm-long waveguide, the peak intensity in the output plane of the waveguide was 70% of that at the waveguide input. These results indicate the lowest coupling and insertion losses of any waveguide published to date. The gas-filled capillary discharge waveguide is shown to be capable and versatile, and is suited for use as a tool in other applications. The use of the waveguide in the fields of XUV lasers and laser wakefield acceleration is discussed.
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Randerson, Patrick J. "Fundamental dynamics in high intensity laser ionization". Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1110219813.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xv, 145 p.; also includes graphics (some col.) Includes bibliographical references (p. 138-145). Available online via OhioLINK's ETD Center
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REDAELLI, RENATO. "Ultrashort - high intensity laser matter interaction studies". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2010. http://hdl.handle.net/10281/7734.
Testo completoAbstract (sommario):
Synopsis
My thesis work concerns the study of plasmas produced by high intensity lasers (IL 1014 W/cm2). More precisely, it addresses the study of the properties of strongly compressed materials (equations of state - EOS - in regimes of pressures of tens of Mbar). I have tried to address the physics of laser-plasma interactions in a comprehensive way, emphasizing the correlation between various phenomena. The theoretical part is based on a monodimensional analytical description of the plasma created by direct laser irradiation of the target. Such description takes into account the absorption of laser light, the transport of energy and the plasma hydrodynamics. The various regions of the produced laser plasmas are dealt in details: the plasma corona characterized by a very low density of the expanding plasma, the conduction region between the plasma corona and the shocked material, the region compressed by the shock. In this way, I could also estimate the shock pressure (identified with the ablation pressure). The experimental part is mainly devoted to the study of EOS of low density plastic materials (foams). The measurements, which are presented, are of interest because this kind of material may have important applications in experiments with shock waves (ICF, EOS) and for improving the hydrodynamic behaviour of the plasma. These were the first measurements performed at pressures higher than 3 Mbar for such low densities (~ 100 mg/cm3). I also present other experiments in my thesis, one of which is the "Polarimetric detection of laser induced ultra-short magnetic pulses in overdense plasma". This part was performed during a 6 months visit at Tata Institute of Fundamental Research in Mumbai, India. The interaction of intense (~1016 Wcm-2), sub picosecond pulses with solid targets can generate highly directional jets of hot electrons. These electrons can propagate in the solid along with the counter propagating return shielding currents. The spontaneous magnetic field that is generated by these currents, captures in its time evolution, important information about the dynamics of the complex transport processes. By using a two pulse pump-probe polarimetric technique the temporal evolution of multi megagauss magnetic fields is measured for optically polished BK7 glass targets, each coated with a thin layer of either copper or silver. A simple model is then used for explaining the observations and for deducing quantitative information about the transport of hot electrons.
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Schreiber, Jörg. "Ion acceleration driven by high-intensity laser pulses". [S.l.] : [s.n.], 2006. http://edoc.ub.uni-muenchen.de/archive/00005842.
Testo completo
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Schreiber, Jörg. "Ion Acceleration driven by High-Intensity Laser Pulses". Diss., lmu, 2006. http://nbn-resolving.de/urn:nbn:de:bvb:19-58421.
Testo completo
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Mountford, Lorna Catherine. "High intensity laser interactions with sub-micron droplets". Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369219.
Testo completo
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Henig, Andreas. "Advanced Approaches to High Intensity Laser-Driven Ion Acceleration". Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-114831.
Testo completo
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Adams, Frederick P. "X-ray processes in high-intensity laser-matter interactions". Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/25742.
Testo completoAbstract (sommario):
In laser-matter-interaction studies there is a continued interest in the emission and transport of x-rays in laser-irradiated solids. We have irradiated metal foil targets with 0.532 μm laser light with pulse lengths of 2.4 to 2.6 us at absorbed irradiances of 10¹² to 10¹³ W/cm . Calorimetric measurements of the energy of x-ray emission by the laser-produced plasma on the target frontside indicate that copper is a better emitter than aluminum or molybdenum in an x-ray band ≥ 800 eV.
Measurements comparing x-ray transmission through irradiated foil targets with that through identical, unperturbed filters indicate enhanced transmission of x-ray energy through the targets. Temporally-resolved measurements on aluminum targets show that x-ray transmission through the target is strongly time-dependent, with x-ray power transmission through the targets, with the greatest contribution being that resulting from 2D rarefaction of the target after shock breakout. This corroborates earlier observations of delayed x-ray heating of the target rear surface.
Enhanced transmission of x-rays through the targets at the moment of shock breakout was also observed, consistent with a shift of the K-shell x-ray absorption edge in the shocked aluminum plasma allowing increased transmission of the aluminum He[sub α] and IC x-ray lines. Other models which may yield similar enhanced x-ray transmission are investigated and rejected on the basis of experimental measurements on layered targets composed of an aluminum substrate and a copper layer as an x-ray source. Similar enhanced x-ray transmission has also been observed in laser-irradiated magnesium targets. The results provide the first experimental evidence of substantial increase in x-ray transport due to a shift of the K-shell photoabsorption edge induced by shock-compression of a dense plasma.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Kiefer, Daniel. "Relativistic electron mirrors from high intensity laser nanofoil interactions". Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-153796.
Testo completo
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Köhler, Christian. "Ultrashort Light Sources from High Intensity Laser-Matter Interaction". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-88076.
Testo completoAbstract (sommario):
The thesis deals with the development and characterization of new light sources, which are mandatory for applications in atomic and molecular spectroscopy, medical and biological imaging or industrial production. For that purpose, the employment of interactions of high intensity ultra-short laser pulses with gaseous media offers a rich variety of physical effects which can be exploited. The effects are characterized by a nonlinear dependency on the present light fields. Therefore, accurate modeling of the nonlinearities of the gas is crucial. In general, the nonlinearities are due to the electronic response of the gas atoms to the light field and one distinguishes between the response of bound and ionized electrons.
The first part investigates laser pulse self compression, where the consideration of a purely bound electron response is sufficient. We apply an exotic setup with an negative Kerr nonlinearity in order to avoid spatial collapse of the beam on the cost of dealing with an highly dispersive nonlinearity. Analytical analysis and numerical simulations prove the possibility of laser pulse compression in such setups and reveals a new compression scheme, where the usually disturbing dispersion of the nonlinaerity is responsible for compression.
Dealing with tera-Hertz generation by focusing an ionizing two-color laser pulse into gas, the second part exploits a medium nonlinearity caused by ionized electrons. We reveal in a mixed analytical and numerical analysis the underlying physical mechanism for THz generation: ionized electrons build up a current, which radiates. Thereby, the the two-color nature of the input laser is crucial for the emitted radiation to be in the tera-Hertz range. Combining this physical model with a pulse propagation equation allows us to achieve remarkable agreement with experimental measurements.
Finally, the third part deals with nonlinearities from bound as well from ionized electrons on a fundamental level. We advance beyond phenomenological models for responses of bound and ionized electrons and quantum mechanically model the interaction of an ultra-short laser pulse with a gas. Already the simplest case of one dimensional hydrogen reveals basic features. For low intensities, the Kerr nonlinearity excellently describes the response of bound electrons. For increasing intensity, ionization becomes important and the response from ionized electrons is the governing one for high intensities. This quantum mechanical correct modeling allows us to explain saturation and change of sing of the nonlinear refractive index and to deduce suited approximate models for optical nonlinearities.
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Price, Christopher. "High-intensity laser interactions with optically levitated liquid microdroplets". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/25282.
Testo completoAbstract (sommario):
The interaction of sub-picosecond pulses of high intensity laser light with micron, and sub-micron scale objects is currently highly topical. These targets are in a size regime that is intermediate between atomic cluster targets ( ~100 Angstrom) and macro- scopic solids which, unlike microtargets, have been the subject of many studies over recent years. Mass-limited objects can couple very strongly to an intense laser field due to transient plasma resonances or Mie scattering processes and absorb substan- tial amounts of laser energy. These targets off er a unique geometry and size that can potentially produce significantly higher x-ray photon energies than compared to interactions with bulk materials of the same atomic number, and under the same irradiation conditions. This thesis describes, for the first time, the design, construction and character- isation of a new class of in-vacuo optical levitation trap optimised for use in high- intensity, high-energy laser interaction experiments. The optical trapping of 10 micron oil droplets in vacuum was demonstrated, over time-scales of >1 hour at extended distances of 40 mm from the final focusing optic. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with 5 micron spatial resolution. The stability of the levitated droplet was such that it would stay in alignment with a 7 micron irradiating beam focal spot for up to 5 minutes without the need for re-adjustment. The performance of the trap was assessed in a series of trial high-intensity laser experiments using a hybrid optical parametric neodymiun:glass Chirped Pulse Am- plifi cation (CPA) laser system, with focused peak intensities in excess of 10^17 Wcm-2. X-ray knife-edge measurements, using image plate, and single-hit CCD photon energy spectroscopy demonstrated the creation of a spatially symmetric, micron scale x-ray source (< 22 microns), with a measured two electron temperature distribution of between 0.4 and 2.3 keV. These relatively low values were thought to arise from low laser- plasma coupling efficiencies with the droplet, due to the high contrast of the laser system. Initial tests also demonstrated very low integrated RF signals produced from laser-droplet interactions, x9 smaller than wire targets of comparable atomic com- position, highlighting the potential of this technique when extended to kJ, petawatt class lasers for use in probing of material science and high energy density plasma experiments.
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Raible, Daniel Edward. "HIGH INTENSITY LASER POWER BEAMING FOR WIRELESS POWER TRANSMISSION". Cleveland State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=csu1210720146.
Testo completo
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Rehman, Ayesha. "Optical probing of high intensity laser propagation through plasma". Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9326.
Testo completoAbstract (sommario):
This thesis studies the propagation of high intensity lasers through underdense plasmas and the subsequent channel formation. This comprises experimental studies of hole boring mechanism in laser plasma interactions, as well as simulations relevant to these experiments. The experiments described were conducted at the Rutherford Appleton Laboratory (January- April 2009) utilising the Vulcan laser facility. A chapter is dedicated to the characterisation of gas jets used for the channelling experiments. This chapter gives a study of gas flows using different supersonic nozzles and theoretical background that is applicable to laser plasma experiments described later. The major experimental chapter presents, the production of relativistic electron with the interaction of high intensity lasers (1 ps) with under dense plasmas. The experimental results and simulations show that the ponderomotive force of the laser pulse produces an ion channel due to the expulsion of electrons. The interaction of the laser field with the focusing force of the channel leads to significant electron acceleration with energies up to 200 MeV. The final experimental chapter investigates channel creation in deuterium gas jets at varying plasma densities ( 1018 cm−3 - 1020 cm−3), using laser pulses with parameters for the hole-boring phase of the Fast Ignitor scheme of inertial confinment fusion ( τ ~ 30 ps,I = 1018 Wcm−2). The ponderomotive force and relativistic effects cause the laser pulse to self-focus. These effects can guide the laser pulse through the plasma over many Rayleigh lengths. The generation of energetic electrons (~ MeV) was also observed, but with relatively little dependence on density. The experimental data has been also illustrated by simulations, which exhibit good agreement with experimental results for the channel formation.
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Tresca, Olivier. "Optimisation and control of high intensity laser accelerated ion beams". Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16842.
Testo completoAbstract (sommario):
The interaction of a laser pulse of relativistic intensity (≥1×1018 Wcm−2) with a solid target results in the creation of a quasi-electrostatic field at the rear surface of the target. This field is strong enough (TVm−1) to ionise and accelerate ions from the target surface via the Target Normal Sheath Acceleration (TNSA) mechanism. The resulting beam has many desirable properties for a large range of potential applications. The work presented in this thesis aims at optimising and controlling the ion beam properties. Firstly, an investigation of laser driven ion acceleration using ultrahigh contrast (1010), ultrashort (50 fs) laser pulses focused to intensities up to 1021 Wcm−2 on thin foil targets is presented. It is found that irradiation at normal (0◦) incidence produces higher energy ions than oblique incidence (35◦), contrasting sharply with previous work at lower intensities. These findings are confirmed by 1D boosted PIC simulations and can be explained by the acceleration of fast electrons being dominated by a new absorption process. The effects of target composition and thickness on the acceleration of carbon ions are also discussed and compared to calculations using analytical models of ion acceleration. Next, an investigation of the transverse refluxing of fast electrons in targets of limited lateral size is reported. The targets were irradiated by high intensity (∼1×1019 Wcm−2), picosecond laser pulses. The maximum energy of the resulting TNSA proton beams is found to increase with decreasing target surface area. This is explained by the presence of a laterally spreading electron population that reflects off the target edges and enhances the TNSA accelerating field. In addition it is demonstrated that this laterally refluxing electron population can be used to control the spatial intensity distribution of the TNSA proton beam, by changing the geometry of the target. This technique offers encouraging prospects for many applications of laser accelerated ions. Finally, a characterisation study of debris emission generated by the interaction of high power laser pulses with solid targets is presented. Targets of thickness ranging from 1 mm to 5 nm were irradiated by high intensity (∼1×1020 Wcm−2), picosecond laser pulses. The resulting debris emission is found to be directed along the target normal axis at both the rear and front of the target. The front emission profile is found to be similar to a plasma expansion profile. Hollow debris depositions of radius increasing with target thickness are measured from the target rear surface. This emission profile is explained by the propagation and breakout of a laser driven shock at the rear of the target.
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Raible, Daniel Edward. "Free Space Optical Communications with High Intensity Laser Power Beaming". Cleveland State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=csu1313065631.
Testo completo
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Green, James Simon. "Fast electron energy transport in high intensity laser-plasma interactions". Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/7688.
Testo completoAbstract (sommario):
This thesis presents experimental measurements of fast electron energy transport made using optical probing, x-ray and XUV imaging techniques. Hydrodynamic and hybrid particlein- cell (PIC) simulations were used to interpret the results. Measurements of fast electron heating patterns were made using the Vulcan 100 Terawatt (TW) and Petawatt (PW) lasers. For the first (100 TW) experiment the laser power was increased from 10 TW to 70 TW and a transition was observed between collimated electron flow and an annular transport pattern. Hybrid modelling showed that a form of beam hollowing accounted for this. Using the PW laser, a comparison was made of different diagnostic techniques for measuring the fast electron beam divergence. Cu K-alpha and optical probing measurements were found to be consistent, with both measuring a divergence angle significantly larger than that measured before at lower intensities. Several different target geometries were used to investigate how energy coupling from the laser into the fast electron beam is affected by the presence of a laser guide cone. Using the Vulcan PW laser, a significant decrease in energy coupling was observed when using metallic cone-slab targets. The addition of a cone assembly to plastic I AI sandwich targets acted to reduce the fast electron heating pattern. Novel cone-wire target geometries revealed that heating of a cone-guided wire plasma is maximised close to the wire surface. Computational modelling revealed that this is due to enhanced Ohmic heating. Finally, measurements were made of the dependence of laser intensity on the fast electron beam divergence. Data taken at intensities relevant to fast ignition was combined with previous published measurements. It was found that the divergence angle increased with laser intensity and had little dependence on pulse duration. PIC modelling was performed to analyse the data and possible explanations for the intensity dependence are discussed.
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Bellei, Claudio. "Measurements of optical radiation from high-intensity laser-plasma interactions". Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/5372.
Testo completoAbstract (sommario):
This thesis presents experimental and theoretical results on the interaction of high-intensity lasers with solid and gaseous targets. All the measurements that are described belong to the optical region of the spectrum. The interaction with solid targets has been investigated for two different intensity regimes. Intensities of up to 10[21] Wcm-2 have been accessed on the VULCAN laser system at the Rutherford Appleton Laboratory whereas the JETI laser system at the Institut für Optik und Quantenelektronik in Jena allowed to reach intensities of up to 4x10[19] Wcm-2 . For both regimes, the transport of relativistic electrons generated in the interactions has been investigated through measurements of the optical radiation emitted from the rear surface of the solid targets. Polarimetry and angular distribution measurements indicate that the radiation presents a high degree of polarisation and is non-isotropically emitted. It is, therefore, mainly attributed to transition radiation. A theoretical model has been developed in order to interpret and validate the experimental observations. As a result, for the high intensity regime variation of the signal strength of the transition radiation with respect to the direction of observation is attributed to the presence of mm-scale filaments. The interaction with gaseous targets has been investigated at the Astra Gemini facility at the Rutherford Appleton Laboratory, for peak intensities of up to 3x10[19] Wcm-2 in a spot size of 20 [Mu]m FWHM. In this experiment the properties of the laser pulse were studied after interaction with the targets. For this purpose, a second harmonic generation FROG device was used. This allowed to determine both the pulse duration and the temporal phase of the pulse, giving an insight on the dependence of the pulse properties with respect to interaction length and electron number density. The experimental results show that the nonlinear evolution of the pulse can lead to compression from 45 fs before the interaction to a single pulse of below 20 fs duration, after propagating in the gaseous medium.
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Moore, Alastair Stewart. "High intensity laser interactions with extended cluster media : towards laboratory astrophysics". Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413740.
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Symes, Daniel Robert. "High intensity laser interactions with extended atomic cluster and microdroplet media". Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407232.
Testo completo
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Willingale, Louise. "Ion acceleration from high intensity laser plasma interactions : measurements and applications". Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504795.
Testo completoAbstract (sommario):
This thesis presents measurements of high energy ion beams accelerated from high intensity laser interactions, with underdense through to near critical density plasmas, and also presents an application of laser generated ion beams. The first experimental measurements of longitudinally accelerated ion beams from high intensity (-1020 Wcm-2 ) laser interactions with an underdense (0.04 ne) helium plasma are presented. The ion beam was found to have a maximum energy for He2+ of 40+3 _8 MeV, with the highest energy ions being collimated to a cone of less than 10ø. Two dimensional particle-in-cell simulations show that additional effects, due to the time varying magnetic field associated with the fast electron current, enhance the accelerating electric field and provides a focusing mechanism on the ions. Very low density foam targets were used to investigate proton acceleration from near to critical density plasmas. Experimental results show a decrease in acceleration efficiency just above the critical density. Simulations of the interactions show the proton acceleration is very sensitive to the ability of the laser to propagate through the plasma. The lowest density foams allow the best laser propagation, thus enabling proton beams to be accelerated to energy and numbers comparable to those from a solid target. The suitability of a laser generated proton beam for the measurement of self-generated magnetic fields in laser generated plasma has been investigated. The technique was then used to study a novel magnetic reconnection geometry lIsing two laser beams. Proton probing provides evidence for the formation of the reconnection layer and the corresponding instabilities.
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Pratt, Brittni Tasha. "Polarization of Nonlinear Thomson Scattering from a High Intensity Laser Focus". BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8689.
Testo completoAbstract (sommario):
Thomson scattering from free electrons in a high-intensity laser focus has been widely studied analytically, but not many measurements of this scattering have been made. We measure polarization-resolved nonlinear Thomson scattering from electrons in a high-intensity laser focus using a parabolic mirror. The weak scattering signal is distinguished from background noise using single-photon detectors and nanosecond time-resolution to distinguish a prompt scattering signal from noise photons. The azimuthal and longitudinal components of the fundamental, second, and third harmonics were measured. Our measurements reasonably match theoretical results, but also show some asymmetry in the emission patterns.
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Lyachev, Andrey. "High gain ultra-short laser pulse raman amplification in plasma". Thesis, University of Strathclyde, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486537.
Testo completoAbstract (sommario):
This thesis presents an experimental study of broad-band Raman chirped pulse amplification in plasma. Amplification. of a short seed pulse occurs through stimulated Raman backscattering in the presence ofa counter-propagating chirped pump pulse in a preformed plasma waveguide channel. 300 and 200 Jlm diameter, 40 rom long, hydrogen-filled capillary discharge waveguides have been investigated. The plasma channel has the dual purpose of guiding the laser pulses over distances of many Rayleigh lengths and acting· as the nonlinear medium for the Raman instability. Laser energy transmission through the plasma channel, in single mode propagation, is observed ~o be better than 80 % for the pulses with intensities up to 5.8 X 1014 W cm-2. The dependence of the gain on pump intensity and plasma density is experimentally studied and confirms theoretical predictions. It is shown that higher pump intensities inside the capillary can be realised using unmatched guiding due to periodic oscillations ofthe laser beam waist along the plasma channel. Amplification of the seed pulse in the linear regime is obtained when the frequency detuning between the seed and the pump matches th~ plasma frequency. Thus the frequency difference between the pump and gain peaks enables to estimate the plasma density, measured around 1018 cm-3. The high gain regime has been investigated showing that peak gains of over 1200 % can be routinely realised. A peak gain of almost 3000 % has 'been observed under optimal conditions with the highest densities and pump energies. Several diagnostic systems have been developed for simultaneous detection of the spectral and energy gain together with the duration of the seed. Ultrashort pulse high gl;lin amplification of 80 fs, 5 mJ pulse has been demonstrated, giving a peak value of 800% and energy gain of 40 % together with 40 % increase in pulse duration. Amplification ofthe whole seed pulse spectra has been demonstrated using an optical cut-off filter to provide a sufficient detul1ed seed pulse. Future increase of the efficiency will occur in the nonlinear regime of the stimulated Raman backscattering resulting in compression ofthe seed pulse.
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Von, Klitzing Wolf Dietrich Carl. "Ultra-high resolution CO₂ laser spectroscopy and transient line narrowing". Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627129.
Testo completo
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Yoshii, Kazumichi. "High-Order Harmonic Generation from Coherently Rotating Molecules with High-Intensity Ultrashort Laser Pulses". Kyoto University, 2010. http://hdl.handle.net/2433/120416.
Testo completo
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Guler, Emine. "Two wavelength high intensity irradiation for effective crosslinking of DNA to protein". Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0409104-121146.
Testo completo
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Coury, Mireille. "Generation and transport of high-current relativistic electron beams in high intensity laser-solid interactions". Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=20410.
Testo completoAbstract (sommario):
In this thesis, the generation and transport of ultra-high intensity laser-driven relativistic electron beams in overdense plasma is investigated experimentally and numerically. The fast electron beam is experimentally diagnosed by means of a 2D Cu Ka imager and the TNSA-generated proton beam. Analytical models together with a 3D hybrid-PIC code are employed to simulate the beam properties in solids. The effects of the self-generated fields on the fast electron beam transport, the effect of the preplasma density scale length on the laser energy coupling to fast electrons and the influence of the laser spot size on the fast electron beam generation and transport, and on the subsequent proton beam, are reported. Fast electron injection and transport in metal foils irradiated at laser intensity up to 4 x 10²⁰ W/cm², is investigated . The beam transport is simulated over a wide range of beam source conditions and with or without inclusion of selfgenerated magnetic fields . The resulting hot electron beam properties are used in rear-surface plasma expansion calculations to compare with measurements of the beam of accelerated protons. An injection half-angle of ~ 50° - 70° is inferred, which is larger than that derived from previous experiments under similar conditions. The influence of laser spot size on laser energy coupling to electrons, and subsequently to the TNSA-generated protons, in foil targets is reported. Proton acceleration is characterized for laser intensities ranging from 2 x 10¹⁸ - 6 x 10²⁰ W/cm², by variation of the laser energy for a fixed spot size, and by variation of the spot size for a fixed energy. At a given laser pulse intensity, the maximum proton energy is higher under defocus illumination compared to tight focus. The results are explained in terms of higher laser pulse energy and geometrical changes to the hot electron injection. The laser-to-electron energy conversion efficiency is investigated in metal foil s over a wide range of preplasma density scale lengths. A hybrid-PIC code is employed to model the fast electron beam transport in the solid, for a given hot electron source. The resulting fast electron density is used to infer the maximum proton energy for comparison with experimental results. It is shown, in agreement with previous published work, that some preplasma density scale length leads to an enhancement of the energy coupling efficiency of laser light to fast electrons.
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Hakami, Ashwaq. "Measurement of the Nonlinear Refractive Index in the High Laser Intensity Limit". Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37618.
Testo completoAbstract (sommario):
When an intense laser beam interacts with matter, the Kerr nonlinearity results in self-focusing. Above the critical intensity, self-focusing dominates pulse spreading through diffraction leading to continuous pulse narrowing and thus an increase of the laser peak intensity. Collapse is prevented through the fact that peak intensities ultimately reach a level where ionization occurs. The profile of ionized electrons represents a negative lens which balances Kerr nonlinear self-focusing and causes the formation of stable filaments. From filaments radiation is emitted in a cone around the filament which has been termed conical emission. Filament formation happens at non-perturbative intensities where the formalism of perturbative nonlinear optics loses its validity. This opens the question of how the Kerr nonlinearity behaves in the non-perturbative limit and how large the Kerr nonlinear coefficient is.
The expression for the Kerr nonlinearity is derived by perturbation theory; the validity of this expression in the non-perturbative limit is questionable. Further, experimentally the Kerr nonlinear index is extracted from measurements of the self-focusing distance as a function of beam intensity which is called the Z-scan method. This method fails at non-perturbative intensities due to the presence of the negative lens coming from the ionized electrons. The effects of the positive focusing and negative self-defocusing lens cannot be separated by the Z-scan method. As a result, not much is known about the Kerr nonlinearity in the regime of non-perturbative nonlinear optics.
The purpose of this thesis is twofold. First, recently it has been discovered that conical emission can be utilized as a broadband and very efficient amplification mechanism in the far infrared. The process has been dubbed Kerr instability amplification. The difference between conical emission and Kerr instability amplification is that they take place in two different regimes of the nonlinear interaction. Whereas conical emission grows out of noise and therewith only takes place once the pump pulse has been substantially restructured due to filamentation, Kerr instability amplification is seeded with a second pulse and therewith occurs long before filamentation happens. The theory developed for Kerr instability amplification has been developed based on a stability analysis of the scalar wave equation. This analysis has shown that with pump lasers in the 1-2 μm range amplification of infrared radiation up to the 10’s of μm can be achieved.
For amplification over such a wide range it is not adhoc clear to which exent vectorial wave effects can be neglected. The first part of the thesis closes this gap by developing the vectorial theory of vector instability amplification.
The second part uses the results derived for Kerr instability amplification to answer the question of how to measure the Kerr nonlinear index in the nonperturbative laser intensity limit. The idea rests on the fact that Kerr instability amplification is maximum for a specific angle between pump and seed beam which varies as a function of laser pump intensity. A relation is derived that connects this angle with the Kerr nonlinear refractive index. As a result, from the maximum angle measured as a function of pump intensity, both magnitude and functional form of the Kerr nonlinear index as a function of laser intensity can be determined.
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Chen, Junewen. "Development and applications of a high intensity ultrashort pulse UV laser system". Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46710.
Testo completo
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Moore, Nicholas. "An investigation of laser oscillators and amplifiers using high intensity diode-pumping". Thesis, University of Southampton, 1998. https://eprints.soton.ac.uk/394398/.
Testo completoAbstract (sommario):
The work presented in this thesis is split into two related areas. The first area of research was the construction of high gain, high power, all-solid-state laser amplifiers for use in master oscillator, power amplifier (MOPA) systems. The second area was the operation of solid-state lasers on low gain transitions. The two areas are related by the fact that the primary aim in each was to maximise the available gain on a given laser transition. Two diode-pumped travelling wave amplifiers are described, both using Nd:YLF as the active medium, and both employed to amplify the output from a modelocked 1047nm Nd:YLF laser. The first amplifier was pumped by a 4W diode, and produced a small signal gain of 34. To suppress gain saturation in the amplifier, the input signal to the amplifier was formed into pulse trains of duration 10µs. The average gain achieved during these pulses was 20, giving rise to an average output power of 5W during the pulse. The amplifier output was subsequently frequency-doubled by a single pass through an LBO crystal. An average conversion efficiency of 57% was obtained, giving an average green power of 2.9W. The green output was subsequently used to pump both an OPO based on LBO, and a Ti:Sapphire laser. The second amplifier had a pump power of 28W. This produced a small-signal gain of 40 at 1047µm, and yielded 6W of amplified modelocked output on a cw basis rather than pulsed as in the first amplifier. The output from this amplifier was used to pump an OPO based on PPLN, and this was able to oscillate at a maximum wavelength of 6.2µm. The work on low gain lasers was addressed at the 1123nm transition in Nd:YAG. This has a cross-section ~15 times lower than at 1064nm. The pump source was a 7W diode-bar, and using this 1.7W of TEM00 output at 1123nm was obtained in a beam with an M2 of 1.1. This output was subsequently used as the pump for a Tm:ZBLAN fibre laser, which produced a maximum of 230mW of 480nm blue light. A second application envisaged for the 1123nm output was to sense atmospheric water vapour by using a differential absorption LIDAR. For this, narrow linewidth operation of the laser was required. To this end, a single-frequency ring laser was constructed, and this produced a maximum power of 180mW, again in a TEM00 mode with M2 = 1.05. The output power was restricted by limitations on available components.
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Bigongiari, Alessandra. "High Intensity Laser-Plasma Grating Interaction : surface wave excitation and particle acceleration". Palaiseau, Ecole polytechnique, 2012. http://pastel.archives-ouvertes.fr/docs/00/75/83/55/PDF/alebigo_TESI_rapporteurs.pdf.
Testo completoAbstract (sommario):
Les ondes de surface ont été observées pour la première fois par Wood en 1902 qui note des anomalies dans le spectre de diffraction d'une lumière continue sur un réseau métallique. Pour certaines longueurs d'onde, le spectre diffracté présente des lignes noires que Fano interprète quelques années plus tard (1941) comme dues à l'excitation d'ondes de surface. De façon analogue, on peut exciter par laser de façon résonante une onde plasma de surface à la surface d'un plasma sur-dense créé par interaction laser-solide, si les conditions d'excitation de l'onde sont satisfaites. L'onde de surface se propage le long de l'interface plasma-vide et se caractérise par un champ électrique résonant haute-fréquence localisé. Dans ce travail, la dynamique du plasma et les champs associés à l'excitation par laser de l'onde de surface sont décrits numériquement avec des simulations bidimensionnelles Particule-In-Cell dans lesquelles la surface du plasma est initialement pré-structurée de sorte à satisfaire les conditions d'excitation de l'onde de surface. L'intensité laser a été variée entre Iλ2 =10^15 et 10^20 μm^2/Wcm^2 afin d'étudier la transition entre un régime d'excitation non-relativiste et relativiste. Les simulations dans lesquelles l'onde de surface est excitée sont comparées à celles où elle ne l'est pas et le couplage du laser avec la cible est analysé. Pour différents paramètres du laser et de la cible, nous avons considéré les quatre aspects suivants de l'interaction laser plasma : i) l'absorption laser et le champ électrique à la surface du plasma, ii) le champ magnétique quasi-statique généré, iii) le chauffage électronique et iiii) l'accélération des ions. Nous avons démontré la possibilité d'exciter une onde plasma de surface pour une large gamme d'intensité laser. Lorsque l'onde de surface est excitée, la composante perpendiculaire à la surface du plasma du champ électrique est amplifiée par rapport au champ laser sur la surface plasma-vide d'un facteur allant de 3. 2 à 7. 2 selon les cas. L'absorption augmente également fortement de 27% lorsque l'onde de surface n'est pas excitée à 73% lorsqu'elle l'est pour Iλ2=10^19 μm^2/Wcm^2 par exemple. Cette étude nous a permis de définir les conditions optimales pour lesquelles le couplage entre le laser et l'onde de surface est le plus efficace. Elles correspondent au régime d'intensité laser relativiste dans lequel le mécanisme d'absorption principale est le " vacuum heating " : les particules gagnent de l'énergie en oscillant dans le champ électrique perpendiculaire à la cible. En présence de l'onde de surface, cette oscillation est fortement augmentée par la présence du champ localisé de l'onde de surface plus intense que le celui du laser. La possibilité de créer des champs magnétiques quasi-statiques auto-générés en présence d'une onde de surface a de plus été étudiée analytiquement et les résultats ont été comparés à ceux des simulations. Les structures de champ obtenues suggèrent que l'intensité du champ magnétique généré induit un confinement partiel des particules sur la surface de la cible lorsque l'onde de surface est excitée. Enfin, nous avons observé un effet induit par l'excitation de l'onde de surface encore plus fort dans des cibles minces dans lesquelles les électrons peuvent circuler d'un bord à l'autre de la cible et interagir plusieurs fois avec le champ de l'onde. Le champ de charge d'espace ainsi créé au cours de l'interaction induit une augmentation importante de l'énergie des ions émis sur les deux faces de la cible mince. L'ensemble de ce travail nous a permis de montrer que l'excitation d'une onde de surface par interaction laser-plasma structuré est un mécanisme physique prometteur pour augmenter l'énergie des particules émises. C'est un point particulièrement intéressant pour les applications liées à la production de protons énergétiques telles que la thérapie hadronique ou à celle d'électrons de hautes énergies indispensables dans le processus de fusion inertiel dans lequel le schéma de l'allumeur rapide est utiliséeSurface waves in solids were first observed by Wood in 1902 as an anomaly in the diffraction of a continuous light source from a metal grating: the diffracted spectrum presented dark lines corresponding to certain wavelengths, which were later explained (Fano, 1941) in terms of the excitation of a surface wave sustained by the grating. Similarly to the metal grating case, a surface plasma wave (SPW) can be resonantly excited by a laser pulse at the surface of a laser-produced over-dense plasma, if the correct matching conditions are provided. SPWs propagate along the plasma-vacuum interface and are characterized by a localized, high frequency, resonant electric field. In the present work we describe numerically the dynamics of the plasma and the field distribution associated to SPW excitation, using two-dimensional particle-in-cell (PIC) simulations, where the plasma surface is initially pre-formed so that the SPW excitation conditions are fulfilled. We examine the surface wave excitation for a large range of laser intensities (Iλ2 =10^15-10^20 μm^2/Wcm^2) in order to study the transition from the non-relativistic to the relativistic regime. The simulations in which the wave is resonantly excited are compared to cases in which the resonant conditions are not provided and the coupling of the laser with the target is analyzed. We have considered the following aspects of the laser-plasma interaction, for different laser and target parameters: i) the laser absorption and the electric field at the surface ii) the generation of a quasi-static magnetic field iii) the electron heating and iiii) the ion acceleration. The possibility to excite a surface plasma wave on a structured target for a large range of laser energies has been demonstrated. In the cases where the surface wave is excited the electric field component normal to the target is amplified at the surface by a factor ranging from 3. 2 to 7. 2 with respect to the laser field. The absorption is also increased,for example it raises from 27% when the SPW is not excited up to 73% for Iλ^2=10^9 μm^2/Wcm^2. We have defined the optimal conditions for efficient coupling which increase laser absorption, that correspond to the relativistic laser intensities (Iλ^2>10^19 μm^2/Wcm^2). In this regime the main absorption mechanism is vacuum heating, associated to particles oscillating in the field perpendicular to the target, which is enhanced by the stronger, localized field of the SPW. The generation of a quasi-static magnetic field has been studied analytically and compared to the result of PIC simulations. The different field structure in presence of a SPW and for a flat target suggests that the enhanced field strength has caused partial confinement of particles at the target surface when SPW is present. The effects of the surface wave are more pronounced in thin laminar targets where electrons recirculate into the target interacting several times with the wave. Efficient electron heating increases the energy of the ions which are accelerated at both the irradiated and not irradiated target surface by the hot electrons space charge field. For the thinnest target (3. 5 μm) the ion cut-off energy is about 14 Mev, approximately twice the value obtained when the SPW is not excited
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Gamble, Bryan Matthew. "HIGH-INTENSITY, ORGANIC PHOTOCHEMISTRY: INVESTIGATIONS USING ARGON-ION AND EXCIMER LASER-JETS". University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin992448029.
Testo completo
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Gamble, Bryan M. "High-intensity, organic photochemistry investigations using argon-ion and excimer laser-jets /". Cincinnati, Ohio : University of Cincinnati, 2001. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin992448029.
Testo completo
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Sharifi, Kalahroudi Seyed Mehdi. "SOME ADVANCEMENT IN IONIZATION OF ATOMS AND MOLECULES IN INTERMEDIATE INTENSITY REGIME USING ULTRA-FAST LASER PULSES". Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27640/27640.pdf.
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Galli, Lorenzo [Verfasser], e Henry [Akademischer Betreuer] Chapman. "Phasing using high intensity free-electron laser radiation / Lorenzo Galli. Betreuer: Henry Chapman". Hamburg : Staats- und Universitätsbibliothek Hamburg, 2015. http://d-nb.info/1066898332/34.
Testo completo