Bibliografías temáticas / Bremsstrahlung,plasma

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Literatura académica sobre el tema "Bremsstrahlung,plasma"

Autor: Grafiati
Publicado: 4 de junio de 2021
Última modificación: 6 de febrero de 2022

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Artículos de revistas sobre el tema "Bremsstrahlung,plasma"

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Ishihara, Osamu y Akira Hirose. "Plasma Turbulent Bremsstrahlung". Physical Review Letters 72, n.º 26 (27 de junio de 1994): 4090–92. http://dx.doi.org/10.1103/physrevlett.72.4090.

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MAHDAVI, M., B. KALEJI y T. KOOHROKHI. "BREMSSTRAHLUNG RADIATION IN DEUTERIUM/TRITIUM DEGENERATE PLASMA". Modern Physics Letters B 24, n.º 30 (10 de diciembre de 2010): 2939–45. http://dx.doi.org/10.1142/s0217984910025231.

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The Bremsstrahlung radiation power is one of the important loss processes in the inertial confinement fusion. The motion of ions is usually neglected when calculating the Bremsstrahlung radiation of the plasma. We calculate the Bremsstrahlung radiation power by taking into account the motion of ions in degenerate plasma. We found a two-temperature function for Bremsstrahlung radiation of the plasma. Finally, the Bremsstrahlung optical depth is obtained for plasma.
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3

JUNG, YOUNG-DAE y CHANG-GEUN KIM. "Classical bremsstrahlung radiation from electron–ion encounters in a nonideal plasma". Journal of Plasma Physics 67, n.º 2-3 (abril de 2002): 191–97. http://dx.doi.org/10.1017/s002237780100157x.

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The classical electron–ion Coulomb bremsstrahlung process is investigated in a nonideal plasma. An effective pseudopotential model taking into account plasma-screening and collective effects is applied to describe the electron-ion interaction potential in a nonideal plasma. The screened hyperbolic-orbit trajectory method is applied to the motion of the projectile electron in order to investigate the bremsstrahlung radiation cross-section as a function of the scaled impact parameter, eccentricity, nonideal-plasma parameter, Debye length, projectile energy, and photon energy. It is found that the collective effect reduces the bremsstrahlung radiation cross-section on both the soft- and hard-photon cases. For small impact parameters, the nonideal-plasma effect on the bremsstrahlung radiation cross-section is found to be quite small. It is also found that the maximum position of the bremsstrahlung radiation cross-section gets closer to the target ion with increasing nonideal-plasma effect.
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MAHDAVI, M. y S. F. GHAZIZADEH. "RADIATION EMISSION AND RE-ABSORPTION MECHANISMS IN DENSE MEDIUMS". Modern Physics Letters B 26, n.º 24 (21 de agosto de 2012): 1250157. http://dx.doi.org/10.1142/s0217984912501576.

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In this paper, the Bremsstrahlung emission and re-absorption mechanisms are studied mainly through Inverse Bremsstrahlung and Compton Scattering. The Radiation Specific Power is calculated numerically assuming the suitable forms of Energy Distribution Function in plasma conditions. The calculation of Spectral Emission shows that, the Bremsstrahlung emission is strongly forward and backward peak relative to electron direction in overdense and high temperature plasma. Finally, some of the conditions for dominant of the re-absorption mechanism are explained.
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Kim, Hwa-Min y Young-Dae Jung. "Collective Effects on the Transition Bremsstrahlung Spectrum due to the Polarization Interaction in Nonideal Plasmas". Zeitschrift für Naturforschung A 64, n.º 1-2 (1 de febrero de 2009): 49–53. http://dx.doi.org/10.1515/zna-2009-1-208.

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The collective effects on the transition bremsstrahlung spectrum due to the polarization interaction between the electron and Debye shielding cloud of an ion are investigated in nonideal plasmas. The impact parameter analysis with the effective pseudopotential model taking into account the nonideal collective and plasma screening effects is applied to obtain the bremsstrahlung radiation cross-section as a function of the nonideality plasma parameter, Debye length, photon energy, and projectile energy. It is shown that the collective effects enhance the bremsstrahlung radiation cross-section and decrease with increasing impact parameter. It is also shown that the collective effect is the most significant near the maximum position of the bremsstrahlung cross-section. In addition, it is shown that the collective effect decreases with an increase of the radiation photon energy
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Tsytovich, V. N., R. Bingham, U. de Angelis y A. Forlani. "Collective effects in bremsstrahlung in plasmas". Journal of Plasma Physics 56, n.º 1 (agosto de 1996): 127–47. http://dx.doi.org/10.1017/s0022377800019140.

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The results of recent developments in the theory of fluctuations in plasmas show that the previously used theory of bremsstrahlung is incomplete and the exact expressions for bremsstrahlung should include transition bremsstrahlung. The collective effects in bremsstrahlung known previously as Debye screening are changed to a qualitatively different structure, which removes the effect of ion polarization in bremsstrahlung and introduces a new effective polarization which depends on an effective ion charge and electron velocity. The results may be relevant for applications in plasmas when the wavelength is greater than the Debye length. It is shown that for the problem of photon transport in the solar interior the correct collective corrections to the bremsstrahlung change the opacity by only about −0·35%, which is less than was calculated previously when collective effects in bremsstrahlung where estimated without taking recent results of plasma fluctuation theory into account.
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Bendib, K., A. Bendib, K. Bendib, A. Bendib, A. Sid y K. Bendib. "Weibel instability analysis in laser-produced plasmas". Laser and Particle Beams 16, n.º 3 (septiembre de 1998): 473–90. http://dx.doi.org/10.1017/s0263034600011289.

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Analytic analysis of collisionless Weibel modes in laser-created plasmas is presented. The heat flux (HF), the plasma expansion (PE), and the inverse bremsstrahlung absorption (IBA) sources have been investigated. It has been shown that for short laser wavelengths (λL < 1 µm) and high laser fluxes (I > 1014 W/cm2), the inverse bremsstrahlung absorption is the most efficient Weibel mechanism for producing strong magnetic fields in the vicinity of the critical layer. For large laser wavelengths (λL < 10 µm), the production of the magnetic fields in the vicinity of the critical layer, due to the plasma expansion mechanism, is as important as the ones due to the thermal transport and the inverse bremsstrahlung absorption mechanisms. Useful scaling laws of convective e-foldings, with respect to the laser and the plasma parameters, are also derived.
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8

Tsytovich, Vadim N. "Collective effects of plasma particles in bremsstrahlung". Uspekhi Fizicheskih Nauk 165, n.º 1 (1995): 89–111. http://dx.doi.org/10.3367/ufnr.0165.199501c.0089.

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Tsytovich, Vadim N. "Collective effects of plasma particles in bremsstrahlung". Physics-Uspekhi 38, n.º 1 (31 de enero de 1995): 87–108. http://dx.doi.org/10.1070/pu1995v038n01abeh000065.

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Silin, V. P. "On coherent harmonic bremsstrahlung in laser plasma". Journal of Experimental and Theoretical Physics 87, n.º 3 (septiembre de 1998): 468–77. http://dx.doi.org/10.1134/1.558683.

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Tesis sobre el tema "Bremsstrahlung,plasma"

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Carpino, Haydée. "Emissione di bremsstrahlung e applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17896/.

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Oggetto di questa tesi è la bremsstrahlung, principale meccanismo di emissione di plasmi astrofisici. Posto che una particella accelerata emetta con potenza data dalla formula di Larmor, in un plasma termico si può studiare il singolo evento di bremsstrahlung come l’interazione tra un elettrone libero ed uno ione. Essendo l’energia conseguentemente emessa espressa in funzione della velocità, si arriva all’emissività totale, attraverso la distribuzione di Maxwell-Boltzmann valida in un plasma termico. Viene poi preso in considerazione il caso in cui il plasma presenti autoassorbimento ed il caso relativistico. Nella seconda parte, definite alcune grandezze caratteristiche, si passa ad esaminare alcune applicazioni astrofisiche, quali l’emissione dell’ICM che permea gli ammassi di galassie -ponendo attenzione all’Ammasso della Chioma ed al missing mass problem- e su scala galattica l’emissione dell’ISM. In particolare sono state approfondite le emissioni di regioni HII, facendo riferimento a W3(A) e W3(OH), e di oggetti Herbig-Hero.
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Lesci, Giorgio. "Emissione di Bremsstrahlung e applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13935/.

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La Bremsstrahlung, o radiazione di frenamento, è un processo di emissione nel continuo su un intervallo di frequenze che va dal radio ai raggi gamma. Come per gran parte dei processi di emissione in astrofisica, essa si basa sulla perdita di energia da parte di cariche accelerate. È noto infatti dalle equazioni di Maxwell che cariche accelerate emettono radiazione. In particolare, nel singolo processo, un elettrone subisce una decelerazione entrando nel campo coulombiano di uno ione o un protone. La formula di Larmor infatti suggerisce che il contributo dell'energia emessa dagli ioni risulta trascurabile in confronto a quella irradiata dagli elettroni. Tale processo è dunque fondamentale all'interno dei plasmi, e in particolare si suddivide in Bremsstrahlung termica e Bremsstrahlung relativistica. Il primo caso ha luogo all'interno di un plasma termico, in cui gli elettroni seguono una distribuzione di Maxwell-Boltzmann delle velocità. Nel caso della Bremsstrahlung relativistica, invece, lo spettro degli elettroni segue una legge di potenza. Oltre alla trattazione fisica del processo, verranno inoltre illustrati alcuni casi astrofisici in cui esso ha una particolare rilevanza, concentrando infine l'attenzione su una ricerca condotta da G. E. Allen, M. D. Stage e J. C. Houck sull'emissione di Bremsstrahlung da parte del resto di supernova Cas A.
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Bindi, Chiara. "Emissione di Bremsstrahlung ed applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018.

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L'elaborato è costituito da due capitoli principali. Il primo capitolo è incentrato prevalentemente sulla trattazione fisica del processo di emissione di Bremsstrahlung: nella prima parte si procede trattando il caso di singolo elettrone per poi passare al caso generale di emissione termica, si conclude affrontando il caso relativistico. Nel secondo capitolo vengono trattate le principali applicazioni astrofisiche del fenomeno. L'emissione per Bremsstrahlung implica una zona di gas altamente ionizzato: in tal senso viene studiata la regione HII caratterizzata dalla presenza di stelle calde e massive di tipo O/B che tramite la radiazione UV ionizzano il gas che le circonda. Nello spettro si osserva emissione Bremsstrahlung che va dall'ottico al radio. Altra applicazione riguarda le galassie ellittiche dove vi è gas altamente ionizzato situato attorno al nucleo. La fase del mezzo interstellare in questo tipo di galassie è l'HIM e vi è emissione di Bremsstrahlung. Infine si parla dell'emissione X causata dal processo di accrescimento tra un oggetto compatto ed una stella compagna.
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4

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 - MSc
The 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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Esnault, Léo. "Production de photons gamma lors de l'interaction laser-matière et création de paires électron-positron par collision de photons". Thesis, Bordeaux, 2021. http://www.theses.fr/2021BORD0077.

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La création de paires électron-positron par collision de deux photons réels (processus Breit-Wheeler linéaire) est un des processus de base de l’électrodynamique quantique, et est supposé sous-tendre un large éventail de phénomènes astrophysiques des hautes énergies, tels que l’opacité de l’Univers aux photons TeV ou la production de plasmas de paires au voisinage d’objets compacts (AGN, pulsars). Cependant, ce processus n’a jusqu’à présent jamais été directement observé en laboratoire depuis sa prédiction en 1934, et ce principalement à cause de l’absence de sources de photons d’énergie autour du MeV de suffisamment haut flux. Grâce au développement continu des systèmes laser de haute puissance et de haute intensité, la production de telles sources de photons devient toutefois désormais envisageable. Malgré la diversité des approches possibles pour la génération de photons énergétiques par laser, de précédentes estimations semblent indiquer que les sources produites : par rayonnement de freinage d’électrons dans la matière (Bremsstrahlung), ou via les processus Compton inverse linéaire ou Compton inverse multiphoton (parfois appelé synchrotron-like), soient des candidates parmi les plus crédibles pour la production de paires électron-positron par collision de deux photons réels. L’interaction de ces photons multi-MeV avec de la matière peut toutefois aussi créer d’autres paires électronpositrons, qui pourraient constituer une source de bruit pour la détection de ce processus. L’objectif de cette thèse est d’optimiser la production de photons d’énergies autour du MeV générés lors de l’interaction d’un laser avec différent types de cibles (cibles solides simples ou structurées) afin de préparer des expériences de collision de photons sur des installations laser existantes ou en cours de construction. Un modèle semi-analytique permet tout d’abord d’optimiser la production de paires électron-positron par le processus Breit- Wheeler linéaire en fonction des paramètres des sources de photons. En particulier il est montré que, pour des sources de photons produits par Bremsstrahlung, les installations laser existantes permettent d’ores et déjà d’atteindre les distributions en énergies optimales, permettant ainsi d’envisager de telles expériences à haut taux de répétition. Cette étude est complétée par des simulations numériques permettant de modéliser l’accélération d’électrons lors de l’interaction du laser avec des cibles structurées (via un code Particle-In-Cell), la génération des photons gamma lors de la propagation d’électrons dans la matière (via un code Monte Carlo) ainsi que la création de paires électron-positron lors de la collision de ces photons gamma (via le code TrILEns). Ces développements pourraient alors servir de base à la préparation de futures expériences sur des installations laser actuelles
Electron-positron pair creation by the mean of two real photon collision (linear Breit-Wheeler process) is one of the most basic quantum electrodynamics process, and is believed to underlie a large amount of high energy astrophysical phenomena, such as the Universe opacity to TeV photons or the production of pair plasmas near compact objects (AGN, pulsars). However, this process has never been directly observed in the laboratory since its prediction in 1934, mainly because of the absence of high flux MeV-range photon sources. Due to the continuous development of high-power and high-intensity laser systems, the production of such photon sources become however conceivable. Despite the diversity of methods to produce energetic photons by lasers, previous estimates seems to show that the radiation sources produced whether by the slowing-down of electrons in matter (Bremsstrahlung), by the linear inverse Compton scattering process, or by the multi-photon inverse Compton scattering process (sometimes called synchrotron-like) are among the most credible sources for the electron-positron pair production by two real photon collisions. The interaction of such multi-MeV photons with matter could however creates other electron-positron pairs, which could constitute a background noise for the detection of this process. The goal of this thesis is to optimize the production of MeV-range gamma photons by the mean of the interaction of a laser with various kind of targets (simple or structured solid targets) in order to prepare photon-photon collision experiments on existing or currently building laser systems. A semi-analytical model allow firstly to optimize linear Breit-Wheeler pair production in term of the photons sources parameters. Particularly it is shown that, concerning Bremsstrahlung photon sources, the current laser systems already permit to reach the optimum photon energy distributions, opening the possibility to design such experiments at high repetition rate. This study is completed with numerical simulations modeling the electron acceleration in the laser-target interaction (via a Particle-In-Cell code), the gamma photon generation by the electron propagation in matter (via a Monte Carlo code) and the electron-positron pair production in photon-photon collisions (via the TrILEns code). These findings could then be used as a basis to design such experiments on existing or currently building laser systems
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Pandya, Santosh. "Development and performance assessment of ITER diagnostics for runaway electrons based on predictive modelling". Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0036.

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Dans les tokamaks, Sous l'application champ de électrique, les électrons sont accélérés et en même temps, ils subissent une force de friction due aux collisions avec les autres particules du plasma. Cependant, une fraction de la population totale d'électrons peuvent surmonter la force de friction et atteindre une vitesse proche de la vitesse lumière. Ces électrons relativistes sont découplés du plasma et sont appelés électrons runaway (ER). Ils peuvent apparaître lors des différentes phases d'une décharge de plasma. Par exemple, dans la phase de démarrage ou alors pendant les disruptions, au cours desquelles une fraction importante du courant plasma peut être convertie en ER ayant une énergie pouvant atteindre quelques dizaines de MeV. Les ER créés pendant la phase de perturbation peuvent causer des dommages aux premiers composants murs si un dépôt localisé de forte puissance se produit. ITER étant un tokamak de grande taille et un projet coûteux, la génération d'ER n'est pas souhaitable. La viabilité de la machine nécessite que les ER soient détectés en temps réel. La thèse fournit une étude détaillée dans cette direction pour le développement des deux principaux diagnostics sur ITER impliqués dans les mesures de paramètres pour les ER, à savoir, le moniteur de rayons X durs qui détecte le rayonnement de bremsstrahlung et les caméras visibles et infrarouges qui détectent le rayonnement synchrotron. Une solution de conception unique a été proposée pour le moniteur HXRM et est développée ici et optimisée. Pour les caméras, une modélisation des signaux est effectuée pour la première fois. Pour ce faire, un code de calcul a été développé et validé sur différents tokamaks
In tokamaks, under the application of the electric field, a small fraction of the total electrons population can overcome collisional drag force and attain high velocity close to the speed of light. These relativistic electrons are called Runaway-Electrons (REs). The REs can occur during different phases of a plasma discharge. REs created during the disruptions phase can form a high energetic RE-beam that poses a risk to damage the first wall components if localized high power deposition takes place. ITER being a large size tokamak and an expensive project, generation of REs is not desirable during any phases of a plasma discharge. Detection of these REs and measurements of its parameters are important for the tokamak operation. Hence, RE diagnostics have to be in place to aid the commissioning of the disruption mitigation system and also for the post-event analysis to improve the reliability of RE avoidance. The present thesis gives a detailed study in this direction for the development of the two principal ITER Diagnostics involved in RE parameter measurements, namely the Hard X-Ray Monitor (HXRM) that detects bremsstrahlung radiation and the Visible and Infrared Cameras that detect synchrotron radiation. A unique design solution has been given for the HXRM and is developed, R&D tests were performed and optimized in line with this understanding. For the cameras, it is predicted for the first time which images and signal intensity can be expected. To achieve this, a simple but comprehensive code has been developed and validated on tokamaks that can predict RE parameters and corresponding diagnostic signals which may have further uses also in the context of RE avoidance
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Gaudart, Georges. "Etude de la population électronique énergétique d'une source d'ions à résonance cyclotron des électrons". Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10197.

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Le but de cette these est d'etudier la population electronique energetique d'une source d'ions a resonance cyclotron des electrons. Le diagnostic choisi pour l'etude de ces electrons energetiques est la detection du rayonnement de freinage. L'experience a tout d'abord ete realisee et montee sur la source quadrumafios qui a ete concue pour des etudes de physique et qui permet l'implantation de nombreux diagnostics. Les distributions trouvees pour ces electrons energetiques sont non maxwelliennes et l'energie moyenne des particules peut atteindre plusieurs centaines de kev. Par ailleurs la mesure du rayonnement de freinage en plusieurs points du plasma a permis de montrer que la fonction de distribution etait essentiellement dependante de la dynamique perpendiculaire des electrons par rapport au champ magnetique. Il est vrai que l'onde haute frequence (10 ghz et 18 ghz dans le cadre de cette etude) communique aux electrons une energie essentiellement perpendiculaire par rapport au champ magnetique. En parallele a ce travail experimental, un code de calcul de la fonction de distribution electronique a ete developpe. Dans un cadre unidimensionnel (vitesse perpendiculaire uniquement), non relativiste, ce code integre un certain nombre d'ingredients physiques pour modeliser la fonction de distribution electronique (chauffage des electrons par l'onde hf, pertes des electrons dans le cone de pertes, source d'electrons par ionisation, terme de relaxation entre electrons)
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Lobet, Mathieu. "Effets radiatifs et d'électrodynamique quantique dans l'interaction laser-matière ultra-relativiste". Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0361/document.

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Cette thèse a pour objet l'étude de l'interaction laser-matière dans un régime d'éclairement extrême que visent à atteindre plusieurs installations multi-pétawatt en cours de développement (CILEX-Apollon, ELI, IZEST, etc.). Pour un éclairement supérieur à 1022 Wcm-2, la dynamique relativiste des électrons accélérés dans l'onde laser est modiée par un important rayonnement Compton inverse non-linéaire. Au-delà de 1023 Wcm2, les photons ainsi produits peuvent, en interagissant à leur tour avec le champ laser, se désintégrer en paires électron-positron via le mécanisme de Breit-Wheeler non-linéaire. Ces mécanismes d'électrodynamique quantique, dont l'étude expérimentale était jusqu'ici l'apanage des grands accélérateurs de particles, peuvent grandement affecter les mécanismes usuels d'interaction laser-plasma, notamment ceux régissant l'accélération de particules chargées et, par conséquent, le bilan global de l'interaction. Afin de modéliser ce régime inédit d'interaction, qui combine processus collectifs, relativistes et d'électrodynamique quantique, nous avons enrichi des mécanismes précédents le code de simulation particle-in-cell calder développé de longue date au CEA/DIF. L'influence de ces mécanismes est d'abord explorée dans le cas d'une impulsion laser interagissant avec une cible dense de taille micrométrique. Un rendement de conversion de l'énergie laser en photons supérieur à 10% est observée au-dessus de 1023 Wcm-2, tandis que la production d'anti-matière s'emballe, via un mécanisme de cascade, à partir de 1024 Wcm2. Dans un second temps, nous étudions la génération de positrons lors de la collision frontale entre un faisceau d'électrons ultra-relativistes issu d'un accélérateur plasma et une impulsion laser ultra-intense. Dans une dernière partie, nous considérons un scénario prospectif d'intérêt astrophysique, à savoir la collision de plasmas de paires issus de cibles solides irradiées à 1024 Wcm-2 montrant la croissance rapide d'une instabilité de lamentation magnétique combinée à d'intenses effets radiatifs
This PhD thesis is concerned with the regime of extreme-intensity laser-matter interaction that should be accessed on upcoming multi-petawatt facilities (e.g. CILEX-Apollon, ELI, IZEST). At intensities IL > 1022 Wcm-2, the relativistic dynamics of the laser-driven electrons becomes significantly modified by high-energy radiation emission through nonlinear inverse Compton scattering. For IL > 1023 Wcm-2, the emitted-ray photons can, in turn, interact with the laser field and decay into electron-positron pairs via the nonlinear Breit-Wheeler process. These quantum electrodynamic processes, which until recently could only be explored on large-scale particle accelerators, can greatly alter the "standard" mechanisms of laser-plasma interaction, and therefore its overall energy budget. In order to model their intricate interplay with the laser-induced plasma processes, they have been implemented within the particle-in-cell code calder developed at CEA. In a first part, we study these QED processes in the interaction of an ultra-intense laser with a micrometric overdense target. It is found that the laser-to--ray energy conversion efficiency can by far exceed 10% for intensities IL > 1023 Wcm-2, while copious pair production (through pair cascading) kicks in for IL > 1024 Wcm-2. In a second part, we consider positron generation in the collision between a GeV electron bunch issued from a laser-wake eld accelerator and a counterpropagating laser pulse. In a third part, we analyze a prospective scheme of astrophysical interest, consisting in the collision between two dense pair plasmas produced from solid targets irradiated at 1024 Wcm-2 showing a fast-growing magnetic lamentation instability amplified by intense synchrotron emission
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9

Bazinette, Rémy. "Effet de la forme d'excitation électrique sur une décharge contrôlée par barrière diélectrique (dbd) à la pression atmosphérique et application au dépôt de couche mince". Thesis, Pau, 2016. http://www.theses.fr/2016PAUU3009/document.

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Les décharges contrôlées par barrière diélectrique (DBD) homogènes à pression atmosphérique sont une alternative pour réaliser des couches minces sur de grandes surfaces, en continu, sans système de pompage. La physique de ces décharges tout comme les propriétés des couches minces obtenues sont bien établies en excitation sinusoïdale basse fréquence (< 200 kHz) et radiofréquence (13,56 MHz). L’objet de cette thèse est d’étendre le domaine de fonctionnement de ces décharges dans un mélange Penning Ar/NH3. Pour ce faire, un dispositif original a été mis au point permettant de faire varier la fréquence d'excitation en tension sinusoïdale entre 50 kHz à 18 MHz. La DBD nanopulsée répétitive a également été étudiée. L’objectif est d’identifier de nouveaux modes de fonctionnement de la DBD homogène et d’en maximiser la puissance pour augmenter la vitesse de dépôt de couche mince tout en maintenant une qualité compatible avec les applications. Dans un mélange Ar-NH3, le régime de fonctionnement de la décharge transit de luminescent (GDBD) à Townsend (TDBD) vers 250 kHz puis à RF-DBD à partir de 3 MHz. Les mesures électriques et optiques qui ont été réalisées montrent que la puissance moyenne des décharges homogènes augmente d'un facteur 30 entre les régimes GDBD et RF-DBD (jusqu'à 35 W/cm3) tandis que la tension d'amorçage est réduite d'un facteur 6. Ces observations couplées aux spectres d’émission des décharges indiquent que la densité d’électrons augmente de plusieurs ordres de grandeur alors que leur énergie décroit. Ces résultats s’expliquent par un changement de mécanisme d'ionisation avec un rôle dominant de l'émission d'électron secondaire à la cathode en basse fréquence (GDBD et TDBD) tandis que l'ionisation en volume domine en RF-DBD. Les deux transitions entre les régimes GDBD-TDBD et TDBD-RF-DBD sont étudiées. La première est liée au temps de transit des ions de l'anode vers la cathode qui devient plus long que la demi-période. En conséquence, la chute cathodique ne se forme pas. La deuxième transition est liée au piégeage des ions puis des électrons qui dépend de la tension appliquée, de la valeur de l'espace interélectrode et de la fréquence. Ces régimes de décharges sont comparés au régime nanopulsé répétitif (NPR-DBD). Les conditions conduisant à une décharge homogène ont été trouvées. La puissance maximale en régime homogène est de 17 W/cm3 ce qui est 17 fois plus élevé que pour un régime sinusoïdal à même fréquence. Elle est obtenue pour une fréquence de répétition de 30 kHz avec un pulse de tension de 10 ns. Les dépôts de nitrure de silicium et d’oxyde de silicium obtenus à partir de SiH4 avec des GDBD, RF-DBD et NPR-DBD ont été étudiés. Dans tous les cas, la vitesse de dépôt est définie par la puissance de la décharge. L'augmentation de la puissance de la décharge avec la fréquence permet d'augmenter la vitesse de dépôt de 30 à 90 nm/min. Néanmoins avec l'utilisation de silane à température ambiante, des nanoparticules se forment en RF lorsque la puissance de la décharge est forte. La modulation d'amplitude empêche la formation des poudres. Pour ce faire l'énergie injectée pendant le Ton doit être inférieure à 100 µJ. Comme les précurseurs ne sont plus consommés par la formation de poudres, ils sont disponibles pour la croissance de la couche ce qui double la vitesse de dépôt par rapport au continu pour la même puissance moyenne. L'augmentation de la vitesse de dépôt sans poudre avec la puissance moyenne nécessite une augmentation de la fréquence de modulation (> 1 kHz) ce qui implique un Ton de plus en plus court pour limiter l'énergie injectée.Ce travail a mis en évidence un nouveau régime de décharge, la TDBD, en Ar-NH3. Il a permis de comparer les GDBD, TDBD, RF-DBD et NRP-DBD dans la même configuration de décharge. Pour la première fois des dépôts de couches minces ont été faits par RF-DBD et il a été montré que la modulation du plasma peut augmenter significativement la vitesse de dépôt
The homogeneous discharge controlled by dielectric barrier at atmospheric pressure and their applications are a promising field of activity because of their advantages in contrast with the low pressure processes, especially for the on line treatment of large surface without pumping system. The physics of these discharges as the thin film properties obtained are well established with low frequency sinusoidal (<200 kHz) and radiofrequency excitation (13.56MHz). This is what is explored in this thesis aimed to find and explore new modes of homogeneous DBD and maximizing the power to optimize the deposition rate while maintaining quality thin layers. To achieve this goal, an original device has been developed varying the excitation frequency from 100 kHz to 18 MHz. The frequency increase on this range have many consequences. In an Ar-NH3 mixture, the discharge regime becomes successively a glow (GDBD) then Townsend (TDBD) around 250 kHz then RF-DBD from 3 MHz. The electrical and optical measurements that have been done show that the average power of the homogeneous discharges increases by a factor of 30 between GDBD regime and RF-DBD regime (up to 35 W/cm3) while the breakdown voltage is reduced by a factor 6. These observations coupled to the discharge emission spectra indicate that the electron density increases by several orders of magnitude while their energy decreases. These results are due to a change of the ionization mechanism with a dominant role of the secondary electron emission at the cathode in low frequency regime (GDBD and TDBD) while the volume ionization is dominate in RF-DBD. Both transitions between GDBD-TDBD regimes and TDBD-RF-DBD are studied. The first is related to the ion transit from the anode to the cathode which becomes longer than the half-period. In consequence, the cathode fall is not formed. The second transition is related to ions and electrons trapping which depends on the applied voltage, the value of the inter-electrode space and frequency.These discharges regime are compared to Nanopulsed repetitively discharge (NPR-DBD). The conditions leading to a homogeneous discharge are found. In homogeneous regime the maximum of the discharge power is 17 W/cm3 which is 17 times higher than for a low sinusoidal voltage for the same frequency. It is obtained for a repetition frequency of 30 kHz with a 10 ns voltage pulse. Hydrogenated silica and silicon nitride thin film obtained from SiH4 with GDBD, RF-DBD and NPR-DBD were studied. In all cases, the deposition rate is defined by the discharge power. The increase of the discharge power with the frequency increases the deposition rate from 30 nm/min to 90 nm/min. However with the use of silane at room temperature, nanoparticles are formed in RF regime when the discharge power is high. The amplitude modulation allows to prevent the formation of powders. AS far as the energy injected during Ton is less than 100 μJ. As the precursors are not consumed by the formation of powders, they are available for the growth of the layer thereby doubling the deposition rate compared to the continuous process for the same average power. Increasing the growth rate without powders with the average power requires an increase in the modulation frequency (> 1 kHz) i.e. a short Ton to limit the injected energy. Thus this work has highlighted a new discharge regime, the TDBD in Ar-NH3 and compared the GDBD, TDBD, RF-DBD and NRP-DBD discharge in the same configuration. For the first time, RF-DBD coating have been made and it has been shown that modulation of plasma, although it decreases the discharge power, can significantly increase the deposition rate
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Libros sobre el tema "Bremsstrahlung,plasma"

1

Ishihara, Osamu. Plasma turbulent bremsstrahlung. Saskatoon, Sask: Plasma Physics Laboratory, University of Saskatchewan, 1994.

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Astapenko, Valeriy. Polarization Bremsstrahlung on Atoms, Plasmas, Nanostructures and Solids. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013.

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Lang, Kenneth R. VLA observations of the coronal plasma. [Washington, D.C: National Aeronautics and Space Administration, 1989.

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Polarization Bremsstrahlung on Atoms Plasmas Nanostructures and Solids Springer Series on Atomic Optical and Plasma Physics. Springer-Verlag Berlin and Heidelberg GmbH &, 2013.

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Capítulos de libros sobre el tema "Bremsstrahlung,plasma"

1

Tsytovich, Vadim N. "Collective Effects in Bremsstrahlung of Plasma Particles". En Lectures on Non-linear Plasma Kinetics, 321–45. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-78902-1_13.

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Luo, Bin y S. Nan Zhang. "Thermal Bremsstrahlung in a Two-Temperature Plasma". En Astrophysics and Space Science Library, 249–52. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-017-0403-8_36.

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Astapenko, Valeriy. "Bremsstrahlung in Plasma with Account for the Polarization Channel". En Polarization Bremsstrahlung on Atoms, Plasmas, Nanostructures and Solids, 107–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-34082-6_4.

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Korol, Andrey V. y Andrey V. Solov’yov. "Polarizational Bremsstrahlung in Collisions with Hydrogen Atom". En Springer Series on Atomic, Optical, and Plasma Physics, 39–60. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-45224-6_3.

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Korol, Andrey V. y Andrey V. Solov’yov. "Bremsstrahlung in Collisions of Structureless Charged Particles with Atoms and Ions". En Springer Series on Atomic, Optical, and Plasma Physics, 17–37. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-45224-6_2.

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Piana, M. "Inversion of bremsstrahlung spectra emitted by solar plasma". En SVD and Signal Processing III, 475–84. Elsevier, 1995. http://dx.doi.org/10.1016/b978-044482107-2/50051-0.

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Actas de conferencias sobre el tema "Bremsstrahlung,plasma"

1

Vladimirov, S. V., Dimitris Vassiliadis, Shing F. Fung, Xi Shao, Ioannis A. Daglis y Joseph D. Huba. "The turbulent bremsstrahlung (plasma-maser) effect". En MODERN CHALLENGES IN NONLINEAR PLASMA PHYSICS: A Festschrift Honoring the Career of Dennis Papadopoulos. AIP, 2011. http://dx.doi.org/10.1063/1.3544317.

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Sessler, Andrew M. y David H. Whittum. "Suppression of bremsstrahlung by means of a plasma". En Advanced accelerator concepts. AIP, 1992. http://dx.doi.org/10.1063/1.44056.

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Brandt, Howard E. "Nonlinear bremsstrahlung in nonequilibrium relativistic beam-plasma systems". En Optics, Electro-Optics, and Laser Applications in Science and Engineering, editado por Howard E. Brandt. SPIE, 1991. http://dx.doi.org/10.1117/12.43511.

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Silin, Victor P. y Pavel V. Silin. "Nonlinear inverse bremsstrahlung and the harmonic generation in a plasma". En ECLIM 2002: 27th European conference on Laser Interaction with Matter, editado por Oleg N. Krokhin, Sergey Y. Gus'kov y Yury A. Merkul'ev. SPIE, 2003. http://dx.doi.org/10.1117/12.537452.

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Avetissian, H. K., A. K. Avetissian, A. G. Ghazaryan y G. F. Mkrtchian. "Absorption of intense x-ray radiation in plasma by multiphoton inverse-bremsstrahlung". En 2012 IEEE 39th International Conference on Plasma Sciences (ICOPS). IEEE, 2012. http://dx.doi.org/10.1109/plasma.2012.6383366.

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Kim, S. H. y K. W. Chen. "Relativistic electron acceleration by net inverse bremsstrahlung in a laser-irradiated plasma". En AIP Conference Proceedings Volume 130. AIP, 1985. http://dx.doi.org/10.1063/1.35299.

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Taiurskii, A. A. y M. B. Gavrikov. "Spatial nonlinear absorption of Alfven waves by dissipative plasma taking account bremsstrahlung". En APPLICATION OF MATHEMATICS IN TECHNICAL AND NATURAL SCIENCES: 8th International Conference for Promoting the Application of Mathematics in Technical and Natural Sciences - AMiTaNS’16. Author(s), 2016. http://dx.doi.org/10.1063/1.4964994.

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Thomas, Robert. "An Investigation of Bremsstrahlung Reflection in a Dense Plasma Focus (DPF) Propulsion Device". En SPACE TECH.& APPLIC.INT.FORUM-STAIF 2006: 10th Conf Thermophys Applic Microgravity; 23rd Symp Space Nucl Pwr & Propulsion; 4th Conf Human/Robotic Tech & Nat'l Vision for Space Explor.; 4th Symp Space Coloniz.; 3rd Symp on New Frontiers & Future Concepts. AIP, 2006. http://dx.doi.org/10.1063/1.2169261.

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Ay, Yasar, Mohamed A. Abd Al-Halim y Mohamed Bourham. "Investigation of a spherical plasma focus concept as a neutron and bremsstrahlung radiation source". En 2015 42nd IEEE International Conference on Plasma Science (ICOPS). IEEE, 2015. http://dx.doi.org/10.1109/plasma.2015.7180012.

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Kim, Shang H. "Electron acceleration by the net inverse bremsstrahlung of ultrahigh-intensity laser in plasma waves". En OE/LASE '92, editado por Gregory J. Quarles. SPIE, 1992. http://dx.doi.org/10.1117/12.60173.

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