Dissertations / Theses on the topic 'Tokamak'
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Severo, José Helder Facundo. "Estudo da rotação de plasma no tokamak TCABR." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-06092012-125249/.
Full textIn the present work we investigated theorically and experimentally the plasma residual rotation in the tokamak TCABR. Using the neoelassical theory, general expressions for the poloidal velocity and heat flux were obtained for tokamaks with arbitrary plasma cross-sections, and subsonic toroidal flows. The dependency of the poloidal velocity and the heat flow with Mach number a were analyzed. It was found that the poloidal velocity changes sign for a ccrtain valuc alpfa = alpha 0, a critical value ak of a exists corresponding to a maximum value of ion poloidal velocity, and that for alpha > alpha k the poloidal velocity is a decreasing function of alpha.
Kelly, Frederick Alan. "Tokamak density limits." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16628.
Full textAMROLLAHI, REZA. "Iran et tokamak." Paris 6, 1994. http://www.theses.fr/1994PA066779.
Full textWeening, Richard Henry. "Completely bootstrapped tokamak." W&M ScholarWorks, 1991. https://scholarworks.wm.edu/etd/1539623812.
Full textNaiim, Habib Marie. "Caractérisation d'une source de particules de carbone créée par ablation laser pour calibrer les mesures d'érosion par spectrosamakcopie dans un tok." Thesis, Aix-Marseille 2, 2011. http://www.theses.fr/2011AIX22122/document.
Full textIn a tokamak, plasma-wall interactions lead to the erosion of plasma facing components, which can be detrimental to plasma operation and to the safety of the tokamak. In order to fulfil the safety requirements imposed to the ITER project, it is necessary to monitor the amount of eroded material. Optical emission spectroscopy in the visible range is traditionally used to measure particle fluxes from the wall to the plasma. These measurements are done thanks to a collisionnal-radiative model based on atomic physics data. However, these data don’t take into account the observation geometry of the spectroscopic diagnostic, and suffer from relatively large uncertainties. Furthermore, transport, deposition and re-erosion phenomena, as well as the evolution of the transmission or the reflection of optical components can lead to an incorrect estimation of the amount of effectively eroded material. An in situ calibration technique, which consists in injecting by laser a known carbon particle source in the line of sight of the spectroscopic diagnostic during plasma operation, is proposed. The experimental study of laser ablation of carbon allowed to determine the optimal conditions for the constitution of this source, and to characterise the ablated species. These experiments are completed by a modelling of the emission spectrum of the laser induced plasma, in order to obtain information on its ionisation degree. Finally, results of the first validation experiments realised in the German TEXTOR tokamak are presented and discussed
Hoffman, Edward A. "Low activation tokamak reactors." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/16679.
Full textSharma, Atul Stefan. "Tokamak modelling & control." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270120.
Full textMavkov, Bojan. "Control of coupled transport in Tokamak plasmas." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT004/document.
Full textThe objective of this thesis is to propose new methods for analysis and control of partial differential equations that describe the coupling between the transport models of the electron pressure (density multiplied by the temperature) and the magnetic flux in the tokamak plasma. The coupled system is presented by two1D resistive diffusion equations. In this thesis two kinds of control models are obtained. The first is a first-principle driven model and the second one is the data-driven model obtained using system identification techniques. The control design is based on an infinite dimensional setting using Lyapunov analysis. Composite control is designed using singular perturbation theory to divide the fast from the slow component. All the theoretical work is implemented and benchmarked in advanced physics based on simulations using plasma simulator dor DIII-D, ITER and TCV tokamaks
Autricque, Adrien. "Dust transport in tokamaks." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0315/document.
Full textThermonuclear fusion could play an important role amongst the numerous alternative energy sources, especially though the tokamak configuration. It could be a prime candidate for the energy transition, owing to its significant advantages (fuel abundance, low amount of wastes generated, low risks of accidents). However, a certain amount of technological and physical challenges require solving before any fusion power plant can be built. Dust production is one of the major difficulties encountered in tokamaks. These small particles, made out of wall material, are created by erosion of the plasma-facing components by the plasma, where the fusion reactions occur. Dust particles can be transported in the plasma, thereby unleashing large amounts of impurities, which in turn reduces the plasma performances (by raising radiative losses and generating instabilities) and can even jeopardize plasma-facing components. Aiming to understand dust transport, injection experiments are performed on the Korean tokamak \KSTAR. Trajectories are recorded on film via fast cameras and are extracted by image processing routines. A numerical tool implementing the latest models for dust-plasma interactions is developed, and comparisons with experimental data is made, confirming the overall tendency of these models to underestimate the trajectory lengths. Leads of improvements are presented. Concerning dust sources and sinks, the focus is made on dust adhesion and resuspension of dust on the machine walls
Pierre, Ralf. "Lokale Einschlusszeiten eines Tokamak-Plasmas." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=966424131.
Full textMoradi, Sara. "Transport analysis in tokamak plasmas." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210097.
Full textOne of the least understood areas of the impurity transport and indeed any plasma particle or heat transport in general, is the turbulent transport. Extensive efforts of the fusion plasma community are focused on the subject of turbulent transport. Motivated by the fact that impurity transport is an important issue for the whole community and it is an area which needs fundamental research, we focused our attention on the development of turbulent transport models for impurities and their examination against experiments. In a collaboration effort together with colleagues (theoreticians as well as experimentalist) from different research institutes, we tried to find, through our models, physical mechanisms responsible for experimental observations. Although our main focus in this thesis has been on the impurity transport, we also tried a fresh challenge, and started looking at the problem of drift wave turbulent transport in a different framework all together. Experimental observation of the edge turbulence in the fusion devices show that in the Scrape of Layer (SOL: the layer between last closed magnetic surface and machine walls) plasma is characterized with non-Gaussian statistics and non-Maxwellian Probability Distribution Function (PDF). It has been recognized that the nature of cross-field transport trough the SOL is dominated by turbulence with a significant ballistic or non-local component and it is not simply a diffusive process. There are studies of the SOL turbulent transport using the 2-D fluid descriptions or based on probabilistic models using the Levy statistics (fractional derivatives in space). However, these models are base on the fluid assumptions which is in contradiction with the non-Maxwellian plasmas observed. Therefore, we tried to make a more fundamental study by looking at the effect of the non-Maxwellian plasma on the turbulent transport using a gyro-kinetic formalism. We considered the application of fractional kinetics to plasma physics. This approach, classical indeed, is new in its application. Our aim was to study the effects of a non-Gaussian statistics on the characteristic of the drift waves in fusion plasmas.
Ce travail de thèse porte sur le transport turbulent d'impuretés dans les plasmas de fusion
par confinement magnétique. C'est une question de la plus haute importance pour le développement
de la fusion comme source d'énergie. En effet, une accumulation d'impuretés au coeur
du plasma impliquerait des pertes d'énergie par radiation, conduisant par refroidissement à
l'extinction des réactions de fusion. Il est par contre prévu d'injecter des impuretés dans le
bord du plasma, afin d'extraire la chaleur par rayonnement sans endommager les éléments de
la première paroi. Ces contraintes contradictoires nécessitent un contrôle précis du transport
d'impuretés, afin de minimiser la concentration d'impuretés au coeur du plasma tout en la
maximisant au bord. Une très bonne connaissance de la physique sous-jacente au transport
est donc indispensable. L'effet de la turbulence, principal mécanisme de transport, sur les impuretés
est alors une question centrale. Dans cette thèse, un code numérique, AFC-FL, a été développé sur la base d'une approche ``fluide' linéaire pour la turbulence d'ondes de dérive. Il calcule les taux de croissance qui caractérisent la rapidité de l'amorçage des instabilités. L'analyse de stabilité est complétée par l'évaluation des taux de croissance en présence d'un gradient de densité, un cisaillement magnétique ou un nombre arbitraire de différentes espèces d'impureté. Les formules complètes du flux turbulent d'impuretés pour ces taux de croissance calculés des instabilités des ondes de dérive ont été dérivées. Un modèle de transport anormal qui nous permet d'étudier la dépendence du transport en fonction de la charge d'impureté a été développé. Ce modèle prend en compte les effets collisionnels entre les ions, l'impureté et les particules principales de plasma. Une telle dépendence du transport anormal en fonction de la charge de l'impureté est observée dans les expériences et il a été montré que les résultats obtenus sont en bon accord avec les observations expérimentales. Nous avons également étudié l'effet des impuretés sur le confinement de l'énergie dans les plasmas du tokamak JET. La modélisation de transport a été exécutée pour des plasmas avec injection de néon dans la périphérie du tokamak. Cette technique est utilisée afin d'extraire la chaleur par rayonnement sans endommager la paroi et pour réduire certaines instabilités (ELM). Des simulations du code RITM ont été comparées à des mesures effectuées lors d'expériences au JET. Il a été montré que l'injection de néon mène toujours à une dégradation du confinement par rapport aux décharges sans néon. Cependant, l'augmentation de la charge effective, en raison du presence du néon peut diminuer le taux de croissance d'autres instabilité (ITG) et amèliorer le confinement du coeur du plasma. Ce confinement amélioré du coeur peut alors compenser la dégradation au bord et le confinement global du plasma peut s'améliorer.
Doctorat en sciences, Spécialisation physique
info:eu-repo/semantics/nonPublished
Fernandes, Tiago. "Instabilidades MHD no Tokamak TCABR." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-03062016-155509/.
Full textThis work describes the study of magneto-hydro-dynamic instabilities (MHD) commonly observed in plasma discharges in tokamak TCABR (at Instituto de Física da USP). Two main diagnostics were employed to observe these instabilities: a poloidal set of 24 magnetic coils (Mirnov coils) placed near the plasma border and a detector of emissions in the Ultra Violet and soft X-ray range with 20 channels (SXR system) which improvement of the signal conditioning circuit was done as part of this work. These diagnostics were chosen because they provide complementary information, since the SXR system measures the central part of the plasma column, while the Mirnov coils detect the MHD instabilities in the outer part of the column. The information collected by these diagnoses was submitted to spectral analysis with temporal and spatial resolution, making it possible to determine the evolution of the spectral and spatial characteristics of the observed MHD instabilities. These analyzes revealed that during the initial stage of the plasma formation (when the plasma current is still increasing) magnetic islands with decreasing wave numbers, identified as edge kink modes, are detected in the Mirnov coils. After the plasma formation, when the equilibrium parameters are relatively flat (plateau), oscillations are detected in both Mirnov coils and SXR system, indicating the presence of MHD instability in the whole plasma column. In general, the fluctuations measured by the Mirnov coils have low amplitude corresponding to small magnetic islands, which were identified as tearing modes. On the other hand, the instabilities at the central region were identified as sawteeth oscillations that correspond to periodic relaxations in the internal region of the magnetic surface with safety factor q = 1 and that are accompanied by precursor oscillations which amplitude depends on the phase of the relaxation cycles. Due to this amplitude modulation, frequency satellite peaks appear in the spectrograms of the SXR signals. Furthermore, due to the fact that relaxation cycles are not sinusoidal, harmonics of the relaxation frequency also appear in the spectrograms. However, in many TCABR discharges, the intensity of the oscillations measured by the Mirnov coils increase significantly during the plateau, with affects the frequency of all MHD instabilities, even over the sawteeth in the central region of the column. In all cases, it was observed that during the plateau the frequency of the magnetic islands coincides with the frequency of the sawtooth precursors, although they are two different instabilities located in separated radial positions. This coincidence of frequencies allowed describing the frequency evolution of all measured oscillations by considering only two basic frequencies: the cycles of sawtooth relaxation and the magnetic islands.
Oliveira, Alexandre Machado de. "Emissivity Profiles at TCABR Tokamak." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-05092017-154738/.
Full textA determinação dos perfis de equilíbrio do plasma é necessária para avaliar as propriedades do confinamento e para investigar os efeitos de perturbações. Diagnósticos ópticos podem ser usados para determinar alguns desses perfis. No entanto, esses diagnósticos medem toda a radiação luminosa emitida em um ângulo sólido que ilumina cada canal do detector através de uma fenda. Assim, a verdadeira grandeza física medida é a emissividade integrada ao longo da linha de visada. Com isso, algum procedimento de deconvolução, como a inversão de Abel, se faz necessário para obter o perfil de emissividade. No tokamak TCABR do Instituto de Física da USP, um bolômetro de 24 canais e um detector de raios-X moles de 20 canais são utilizados para medir a emissividade do plasma no intervalo de comprimento de onda de 1 a 1.000 nm, dependendo dos filtros utilizados. Neste trabalho, uma simulação numérica é usada para calcular o sinal medido pelos diagnósticos para um dado perfil de emissividade, possibilitando a comparação direta com os dados experimentais, evitando a realização da inversão de Abel e os problemas numéricos associados aos procedimentos de deconvolução. Pela consideração da geometria do tokamak TCABR, as coordenadas espaciais podem ser relacionadas com as coordenadas lineares normalizadas do plasma por meio da imposição de um modelo de emissividade para o plasma que dependa de alguns parâmetros livres, permitindo que a emissividade resultante em cada ponto possa ser calculada. Assim, a luminosidade de cada canal é calculada pela integral da emissividade modelada em cada linha de visada (Transformada de Radon). Os parâmetros livres dos perfis de emissividade são determinados ajustando-se as luminosidades calculadas em termos das luminosidades medidas. Nós consideramos três modelos de perfis de emissividade: um modelo parabólico em lei de potência, um modelo gaussiano e um modelo baseado em funções de Bessel. Observamos que o perfil parabólico ajusta-se bem aos dados do bolômetro, ao passo que o perfil gaussiano é adequado para descrever os dados obtidos com o detector de raios-X moles.
Abiteboul, Jérémie. "Transport turbulent et néoclassique de quantité de mouvement toroïdale dans les plasmas de tokamak." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4062/document.
Full textThe goal of magnetic confinement devices such as tokamaks is to produce energy from nuclear fusion reactions in plasmas at low densities and high temperatures. Experimentally, toroidal flows have been found to significantly improve the energy confinement, and therefore the performance of the machine. As extrinsic momentum sources will be limited in future fusion devices such as ITER, an understanding of the physics of toroidal momentum transport and the generation of intrinsic toroidal rotation in tokamaks would be an important step in order to predict the rotation profile in experiments. Among the mechanisms expected to contribute to the generation of toroidal rotation is the transport of momentum by electrostatic turbulence, which governs heat transport in tokamaks. Due to the low collisionality of the plasma, kinetic modeling is mandatory for the study of tokamak turbulence. In principle, this implies the modeling of a six-dimensional distribution function representing the density of particles in position and velocity phase-space, which can be reduced to five dimensions when considering only frequencies below the particle cyclotron frequency. This approximation, relevant for the study of turbulence in tokamaks, leads to the so-called gyrokinetic model and brings the computational cost of the model within the presently available numerical resources. In this work, we study the transport of toroidal momentum in tokamaks in the framework of the gyrokinetic model
Vayakis, George. "Anomalous transport in the tokamak edge." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291539.
Full textCasson, Francis James. "Turbulent transport in rotating tokamak plasmas." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/36765/.
Full textHernández, Manuel S. (Manuel Segundo). "Meta-analysis of Tokamak reactor designs." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/106768.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (pages 55-60).
The long-term interest in nuclear fusion using tokamaks has yielded many published reactor designs. This study performs the first meta-analysis of tokamak reactor designs in an attempt to unveil new understanding not available in the traditional bottom-up method of looking at each design individually. Forty tokamak designs intended to produce significant fusion power at gains above one were identified in the published literature. Thirty-three important parameters describing a tokamak design were compiled by examining the set. The parameters from each design were extracted and placed into a database and plotted against each other to identify trends and outliers. Major outliers include two low aspect ratio designs and two He-3 reactor designs. Two classes are apparent in the database indicating two design philosophies: large major radius (~7 m), high power (~1.8 GW), and low density (~1 * 1020 m-3) designs utilizing superconducting magnets; and small major radius (~2.5 m), low power (~0.2 GW), and high density (~4* 1020 m-3 designs utilizing copper magnets. The former class has longer confinement times, higher plasma current, and lower magnetic field while the latter class tends to have lower gain, higher power per surface area, higher power per volume, and much smaller stored magnetic energies. Between the two sets, the non-dimensional plasma physics parameters are similar. These two basic design strategies have been in practice for the last 40 years. Since tokamak designs were first published, there has been little appreciable change in the mean and design envelope of the major parameters such as major radius, fusion power, magnetic field, and plasma current and of the plasma physics parameters such as beta, safety factor, temperature, density, and confinement time. The lack of significant change suggests that no major technological or physics breakthrough that could radically affect design philosophy has been discovered, and neither design philosophy has dominated. Trade-offs in triple product are apparent as all designs are at similar plasma temperature except He-3 reactors, while confinement time and density vary inversely among designs. The major dependencies on plasma current and size in the experimental confinement time scaling are also apparent. The conservatism inherent in reactor designs can be inferred from plasma physics parameters such as the confinement enhancement factor, normalized beta, and safety factor. The database indicates designers push all plasma physics limits simultaneously instead of individually.
by Manuel S. Hernandez.
S.B.
Abel, Ian G. "Multiscale gyrokinetics for rotating tokamak plasmas." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:254aa8c8-a68f-401a-8a32-432d26717b25.
Full textKloe, Joost de. "Pellet-plasma interaction in a tokamak /." [S.l. : s.n], 2000. http://catalogue.bnf.fr/ark:/12148/cb37725261x.
Full textSong, Shaodong. "Etude du transport de la chaleur et des particules dans les tokamaks Tore Supra et HL-2A." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10142/document.
Full textHeat and particle transport is one of the fundamental subjects of research in the physics of hot plasmas confined by magnetic fields, a class of physical systems that are studied in the framework of research on controlled thermonuclear fusion. These transport phenomena are mainly related to electromagnetic turbulence and are therefore extremely difficult to model at a first-principle level. Specific experiments in this area, on plasma devices such as tokamaks or stellarators, are widely used to improve understanding of these phenomena. This thesis reports on experimental studies performed on two large tokamaks : Tore Supra (based at CEA/Cadarache, France) and HL-2A (based at the South-Western Institute of Physics, Chengdu, China). The technique used consists in modulated injection of wave power to perturb the electron temperature and/or of Supersonic Molecular Beams to perturb the plasma density. Temperature is then measured by Electron Cyclotron Emission and density by Reflectometry, and Fourier analysis is used to determine the transport properties. Evidence has been found of inward heat convection (a phenomenon whose existence is still controversial) as well as of peculiar effects due to the non-diagonal terms of the transport matrix. Comparison with transport models has been carried out
Hamed, Myriam. "Electron heat transport in tokamak H-mode pedestals." Electronic Thesis or Diss., Aix-Marseille, 2019. http://theses.univ-amu.fr.lama.univ-amu.fr/191128_HAMED_534gjvrc761ijwn176jbu525de_TH.pdf.
Full textIn H-mode plasmas, the modeling of the pedestal dynamics is an important issue to predict temperature and density profiles in the tokamak edge and therefore in the core. The EPED model, based on the stability of large scales MagnetoHydroDynamic (MHD) modes, is most commonly used to characterize the pedestal region. The EPED model has been successful until now. However, EPED model does not take into account small scales instabilities linked the the sharp pressure gradient and the pedestal characteristics prediction in terms of width and height is still open. Moreover, some recent analysis of JET plasmas suggest that another class of instabilities, called microtearing modes, may be responsible for electron heat transport in the pedestal, and thereby play some role in determining the pedestal characteristics. Microtearing modes belong to a class of instabilities where a modification of the magnetic field line topology is induced at the ion Larmor radius scale. This leads to the formation of magnetic islands, which can enhance the electron heat transport. The stability of MTMs has been theoretically studied in the past showing that a slab current sheet is stable in the absence of collisions. In contrast, recent gyrokinetic simulations in toroidal geometry found unstable MTMs, even at low collisionality. The purpose of our work is to improve the MTM stability understanding by comparing new analytical theory to linear gyrokinetic simulations. More precisely, physical mechanisms (magnetic drift, electric potential) are progressively included in the analytical description to recover the numerical simulations results and to "reconcile" numerical MTM investigations with theory
Savčenko, Fedir. "Mitigation of disruptions in a tokamak by means of large gas injection." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=971442193.
Full textMarchuk, Oleksandr. "Modeling of He-like spectra measured at the tokamaks TEXTOR and TORE SUPRA." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971969884.
Full textTardini, Giovanni. "Validation of theory based transport models in tokamak plasmas." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969342926.
Full textThomsen, Henning. "A Dynamics investigation into edge plasma turbulence." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=96493230X.
Full textSavtchkov, Alexei. "Mitigation of disruptions in a tokamak by means of large gas injection." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=971442193.
Full textMerkl, Doris. "Current holes and other structures in motional Stark effect measurements." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971921830.
Full textLauber, Philipp. "Linear gyrokinetic description of fast particle effects on the MHD stability in tokamaks." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969890222.
Full textNa, Yong-Su. "Modelling of current profile control in tokamak plasmas." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=970018460.
Full textDaviot, Ronan. "Etude des champs de flux thermique sur les composants faisant face au plasma dans un tokamak à partir de mesures de température par thermographie infrarouge." Phd thesis, Ecole Centrale Paris, 2010. http://tel.archives-ouvertes.fr/tel-00534809.
Full textBae, Cheonho. "Extension of neoclassical rotation theory for tokamaks to account for geometric expansion/compression of magnetic flux surfaces." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45839.
Full textAsp, Elina. "Drift-Type Waves in Rotating Tokamak Plasma." Doctoral thesis, Uppsala University, Department of Astronomy and Space Physics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3400.
Full textThe concept of energy production through the fusion of two light nuclei has been studied since the 1950’s. One of the major problems that fusion scientists have encountered is the confinement of the hot ionised gas, i.e. the plasma, in which the fusion process takes place. The most common way to contain the plasma is by using at magnetic field configuration, in which the plasma takes a doughnut-like shape. Experimental devices of this kind are referred to as tokamaks. For the fusion process to proceed at an adequate rate, the temperature of the plasma must exceed 100,000,000C. Such a high temperature forces the plasma out of thermodynamical equilibrium which plasma tries to regain by exciting a number of turbulent processes. After successfully quenching the lager scale magnetohydrodynamic turbulence that may instantly disrupt the plasma, a smaller scale turbulence revealed itself. As this smaller scale turbulence behaved contrary to the common theory at the time, it was referred to as anomalous. This kind of turbulence does not directly threaten existents of the plasma, but it allows for a leakage of heat and particles which inhibits the fusion reactions. It is thus essential to understand the origin of anomalous turbulence, the transport it generates and most importantly, how to reduce it. Today it is believed that anomalous transport is due to drift-type waves driven by temperature and density inhomogeneities and the theoretical treatment of these waves is the topic of this thesis.
The first part of the thesis contains a rigorous analytical two-fluid treatment of drift waves driven solely by density inhomogeneities. Effects of the toroidal magnetic field configuration, the Landau resonance, a peaked diamagnetic frequency and a sheared rotation of the plasma have been taken into account. These effects either stabilise or destabilise the drift waves and to determine the net result on the drift waves requires careful analysis. To this end, dispersion relations have been obtained in various limits to determine when to expect the different effects to be dominant. The main result of this part is that with a large enough rotational shear, the drift waves will be quenched.
In the second part we focus on temperature effects and thus treat reactive drift waves, specifically ion temperature gradient and trapped electron modes. In fusion plasmas the α-particles, created as a by-product of the fusion process, transfer the better part of their energy to the electrons and hence the electron temperature is expected to exceed the ion temperature. In most experiments until today, the ion temperature is greater than the electron temperature and this have been proven to improve the plasma confinement. To predict the performance of future fusion plasmas, where the fusion process is ongoing, a comprehensive study of hot-electron plasmas and external heating effects have been carried out. Especially the stiffness (heat flux vs. inverse temperature length scale) of the plasma has been examined. This work was performed by simulations done with the JETTO code utilising the Weiland model. The outcome of these simulations shows that the plasma response to strong heating is very stiff and that the plasma energy confinement time seems to vary little in the hot-electron mode.
Seto, Haruki. "Two-Dimensional Transport Modeling of Tokamak Plasmas." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188588.
Full textYou, Setthivoine. "Computational and experimental studies of tokamak refuelling." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396290.
Full textFord, Oliver P. "Tokamak Plasma Analysis through Bayesian Diagnostic Modelling." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526369.
Full textPodpaly, Yuri Anatoly. "Rotation generation and transport in tokamak plasmas." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77061.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (p. 187-201).
Plasma toroidal rotation is a factor important for plasma stability and transport, but it is still a fairly poorly understood area of physics. This thesis focuses on three aspects of rotation: momentum transport, Ohmic rotation reversals, and LHCD induced rotation. Momentum transport is approached in a semi-empirical method through the development of the "Toy Model." The "Toy Model" assumes that the toroidal momentum is transported via diffusive and convective profiles, and, using assumptions about the diffusive and convective terms, it can generate the profiles of the residual stress or source as a function of space and time. Several resultant source profile calculations are shown for SSEP sweeps, rotation reversals, H-modes, and I-modes. Generally, it is observed that the convective profiles do not greatly improve the fits to the data, and that source profiles have peaks around the steep core rotation gradient region of the plasma. Rotation reversals, spontaneous reversals of the rotation direction during the Ohmic phase, are also described in this work. It is seen that they are related to the Linear Ohmic Confinement (LOC) to Saturated Ohmic Confinement (SOC) regime changeover. This relation is supported through linear gyrokinetic simulations that show that the co- to counter- reversal coincides with a change from marginally electron to ion diamagnetic direction most unstable modes which is believed to play a role in the LOC to SOC explanation as well. Lower Hybrid Current Drive (LHCD) induced rotation is also described, including the first experimental observations of bi-directional rotation on a single tokamak. These observations help to explain differences in rotation seen among the various devices running lower hybrid. The LHCD rotation reverses direction as a function of plasma current, and this occurs in a similar parameter space as the Ohmic rotation reversal; it also has turbulence changes that are reminiscent of the Ohmic reversal as well. This suggests that LHCD is, in fact, causing the plasma to transition from the ITG dominated regime to the TEM dominated regime, which explains the rotation differences. These experiments and models provide new tools to understand rotation transport and generation in tokamaks.
by Yuri Anatoly Podpaly.
Ph.D.
Monteiro, Marcelo de Jesus Rangel. "Espalhamento Thomson multipassagem no Tokamak Nova-UNICAMP." [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278476.
Full textTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Foram executados no tokamak NOVA-UNICAMP os trabalhos da tese que consistiram em duas partes distintas: a primeira ligada à implementação de programas e operação da máquina, e a segunda compreendeu a realização do diagnóstico de espalhamento Thomson utilizado para a medida direta da temperatura eletrônica, e indireta, via espalhamento Rayleigh, da densidade eletrônica do plasma. Com relação à primeira parte, foram desenvolvidos os programas para a aquisição e tratamento dos principais dados provenientes do tokamak e estudado (e determinado) durante os trabalhos as melhores condições de operação da máquina. Já com relação à segunda parte, foi implantado o sistema de multipassagem para o feixe do laser de rubi, que permitiu o aumento da potência incidente em torno de seis vezes, e foi utilizado um novo detector multicanal, o XP 1752 da Philips, que é uma matriz de 8 x 8, totalizando 64 fotomultiplicadoras independentes, e que ainda não havia sido testado na realização do espalhamento Thomson multipassagem e multiespacial. Devido ao número limitado de canais para a aquisição dos dados, via conversores analógico / digital (ADC) , foi possível trabalhar com um total de 20 dos 64 canais do detector multicanal, permitindo se fazer pela primeira vez desde que o tokamak chegou ao laboratório, medidas simultâneas de temperatura e densidade eletrônicas em quatro posições espaciais distintas ao longo do raio do plasma e do tempo de descarga do tokamak
Abstract: In this thesis we present two distinct works implemented on the NOVA-UNICAMP tokamak. The first one involved the determination of the best machine operation conditions with the development of software¿s for machine control, data acquisition and analysis which were not available up to the moment. The second part is the development, set up and use of the Thomson scattering diagnostic with multi-pass, multi-channel, and multi-space capability. This diagnostic permitted us to carry out direct measurements of electron temperature and indirect measurements of electron density using Rayleigh scattering, along a full tokamak discharge time in four different radial position inside the plasma. For the multipass set up, the initial ruby laser power has been increased by a factor of six, which permitted good precision electron temperature and density measurements. The multichannel detection capability has been possible due to the newly available 8 x 8 matrix multi-channel detector XP 1752 from Philips, which, up to our knowledge was used for the first time. Due to the limited numbers of ADC modules available at the time of the measurements, in our Lab., we could use only 20 of the 64 channels which permitted us to perform four spatial temperature measurements during one tokamak discharge. Nevertheless the capability of full spatial electron temperature and density measurements along the tokamak discharges, with good precision, has been demonstrated.
Doutorado
Física
Doutor em Ciências
Sa, Wanderley Pires de. "Reconstrução do equilíbrio no tokamak TCA/BR." Universidade de São Paulo, 1996. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-12122013-162240/.
Full textThe accurate and rapid determination of the Magnetohydrodynamic (MHD) equilibrium configuration in tokamaks is a fundamental subject for the magnetic confinement of the plasma. With the knowledge of characteristic plasma MHD equilibrium parameters it is possible to control the plasma position during its formation using feed-back techniques. It is also necessary an on-line analysis between successive discharges to program external parameters for the subsequent discharges. In this work it is investigated the MHD equilibrium configuration reconstruction of the TCA/BR tokamak from external magnetic measurements, using a method that is able to determine fastly the main parameters of discharge. The thesis has two parts. Firstly it is presented the development of an equilibrium co de that solves de Grad-Shafranov equation for the TCA/BR tokamak geometry. Secondly it is presented the MHD equilibrium reconstruction process from external magnetic field and flux measurements using the Function Parametrization FP method. This method is based on the statistical analysis of a database of simulated equilibrium configurations, with the goal of obtaining a simple relationship between the parameters that characterize the equilibrium and the measurements. The results from FP are compared with conventional methods.
Baquero, Wilson Andres Hernandez. "Flutuações turbulentas de temperatura no Tokamak TCABR." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-30012018-100934/.
Full textThe contribution of the extreme events related to propagating structures in the turbulence, the so-called bursts, seems to be part of the explanation to anomalous transport in confined plasma. But, up to now, there is not an adequate model in the frame of neoclassical transport theory to properly account the contribution of these extreme events. Therefore, the characterization of the particle and energy transport due to the extreme events and the burst internal structure are an important issue in fusion plasma research. However, local electron temperature measurements are necessary to investigate those topics, because particles and energy transport have temperature corrections. Due to their good spatial resolution and relatively easy construction, electrostatic probes are often used to measure temperature in the plasma edge of tokamak. The triple probe configuration and voltage sweep technique are among the most common techniques used with electrostatic probes to measure local temperature in the plasma edge. We present a comparison between the temperature measurement using these two techniques in the tokamak TCABR. For this purpose, it was used stationary standard plasma discharges (it is, discharges with almost stable plasma current and density and with low MHD activity). For temperature measurement, the two methods have good correlation in the Scrape-Off-Layer region but there are discrepancies between their values inside the plasma column. We found that this discrepancy is due to the sheath expansion effect. Therefore, the triple probe equations were modified to properly consider this effect. The modification leads to compatible average temperature measurements between the two methods. We also studied coherent structures propagating in the edge turbulence (detected as bursts in the saturation current) by using the conditional analysis technique. The results seem to be compatibles with structures tilted in the radial-poloidal plane. This tilt implies that the common method to measure the propagation velocity using the delay time of detection between two probes, could produce wrong values. The results for the average temporal behavior of temperature during the bursts are inconsistent between the two methods. Indeed, the triple probe results seems to be physically wrong, once it indicates a strong temperature gradient inside the bursts. We found that this problem is due to the strong potential gradients inside the burst, breaking the assumption that the pins used in the triple probe configuration are in a homogeneous plasma.
Kroetz, Tiago. "Linhas de campo magnético caóticas em tokamak." Instituto Tecnológico de Aeronáutica, 2006. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=339.
Full textMorris, Robert Christian. "Neoclassical poloidal flow damping in a tokamak." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/59970.
Full textBREMOND, SYLVAIN. "Modelisation et commande des plasmas de tokamak." Paris 11, 1995. http://www.theses.fr/1995PA112320.
Full textNicolas, Timothée. "Sawtooth driven particle transport in tokamak plasmas." Palaiseau, Ecole polytechnique, 2013. http://pastel.archives-ouvertes.fr/docs/00/92/64/28/PDF/SawtoothDrivenParticleTransportInTokamakPlasmas_09_01_2014.pdf.
Full textThe radial transport of particles in tokamaks is one of the most stringent issues faced by the magnetic confinement fusion community, because the fusion power is proportional to the square of the pressure, and also because accumulation of heavy impurities in the core leads to important power losses which can lead to a "radiative collapse". Sawteeth and the associated periodic redistribution of the core quantities can significantly impact the radial transport of electrons and impurities. In this thesis, we perform numerical simulations of sawteeth using a nonlinear tridimensional magnetohydrodynamic code called XTOR-2F to study the particle transport induced by sawtooth crashes. We show that the code recovers, after the crash, the fine structures of electron density that are observed with fast-sweeping reflectometry on the JET and TS tokamaks. The presence of these structure may indicate a low efficiency of the sawtooth in expelling the impurities from the core. However, applying the same code to impurity profiles, we show that the redistribution is quantitatively similar to that predicted by Kadomtsev's model, which could not be predicted a priori. Hence finally the sawtooth flushing is efficient in expelling impurities from the core
Grandgirard, Virginie. "Modelisation de l'equilibre d'un plasma de tokamak." Besançon, 1999. http://www.theses.fr/1999BESA2039.
Full textBourdelle, Clarisse. "Analyse de stabilité de plasmas de Tokamak." Université Joseph Fourier (Grenoble), 2000. http://www.theses.fr/2000GRE10101.
Full textBodi, Vasudeva Raghavendra Kowsik. "Anomalous radial transport in tokamak edge plasma." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p3390465.
Full textTitle from first page of PDF file (viewed February 18, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 67-72).
Najera, Omar Cipriano Usuriaga. "Tomografia de emissão H-alfa no tokamak TCABR." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-27022008-133846/.
Full textA study of the tomography profile of the emission of the line of Hydrogen, atomic H-alpha line (?=656.28 nm), was carried out in TCABR, a medium-size tokamak in operation at the Laboratory of Plasma Physics of the Institute of Physics of the University of São Paulo. Our work focuses on the study of the effects of due to the introduction of a biased electrode in the plasma edge of the TCABR tokamak. The electrode could be introduced up to 1.5 cm inside the plasma, without plasma disruptions for positive voltages from 0 to +350V, and was located on the equatorial plane of the plasma column. Tomography profiles of H-alpha with and without bias were measured. Comparison of the profiles shows an increase of the central line-averaged density, while the emissivity of the line H-alpha decreases. The analysis of the tomography profiles of H-alpha, time of confinement of particles and also the study of recycling of the neutral particles, indicate that the confined plasma enters the H-mode regime. Calculations of turbulence and transport at the Scrape-Off-Layer, using measured floating potentials and ion saturation currents, show a strong decrease in the power spectra and transport. The H-alpha tomography was also employed to study the new regime of runaway discharges that has been discovered in the TCABR tokamak. The distinctive features of this regime are weakly ionized low-temperature plasma detached from the limiter due to the recombination process, and a relaxation instability with strong spikes of H-alpha emission correlated with sawtooth relaxation of the line density. In the present thesis we report experimental data on conditions for generation of these discharges. The runaway electron production is analyzed; show that generation of runaway electrons can only be explained by the runaway avalanche mechanism. The confirmation of low plasma temperature is a obtained from an analysis of the tomography profile of H-alpha emission. This emission cannot be explained by excitation by plasma electrons. Recombination, on the other hand, gives a rather plausible explanation for the time dependency of the emission, in particular at high neutral densities.
Breton, Sarah. "Tungsten transport in a tokamak : a first-principle based integrated modeling approach." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0007.
Full textMagnetic confinement fusion is currently the most advanced way to produce energy thanks to Deuterium/Tritium reaction. One of the challenges is the limitation of the reaction contamination because of Tungsten (W), a material capable of resisting high heat fluxes. W large atomic number causes W to radiate inside tokamak plasmas. If W accumulates in the central part, it cools down the plasma. It is therefore crucial to understand the mechanisms of W transport and identify the actuators of the accumulation process. W transport is involved in complex interplays with the plasma parameters (density, temperature, rotation). Therefore the use of integrated modeling is mandatory in order to evolve self-consistently all those parameters for several confinement times. For the first time, an integrated modeling tool is coupled to first-principle transport codes to self-consistently simulate the time evolution of the W behavior, as well as the evolution of density, temperature, rotation profiles, radiation and external heating. For numerical reasons, several phenomena are not modeled, and the physics of the interaction with the inner wall is simplified. At each time step, this simulation successfully reproduces experimental profiles and the W central accumulation. Moreover, actuators of the central W accumulation (rotation and central particle fueling) were identified. Finally, integrated modeling simulation allowed bringing out a very interesting non-linear mechanism: the stabilizing effect of W on turbulence. This work demonstrates that first-principles integrated modeling now allows to design and optimize in advance plasma scenarios with limited W central accumulation
Sridhar, Sundaresan. "Study of tokamak plasma disruptions and runaway electrons in a metallic environment." Electronic Thesis or Diss., Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0313.
Full textTokamaks are the devices currently closest to achieve nuclear fusion power and disruptions are unfavorable events in which the plasma energy is lost in a very short timescale causing damage to tokamak structures. RE beams are one of the consequence of disruptions and they carry the risk of in-vessel component damage. Thus, the prevention and control of the RE are of prime importance. The current strategy for runaway electrons is to avoid their generation by a massive material injection (MMI). If their generation cannot be avoided, a 2nd MMI will be used to mitigate the generated RE beam. After the 1st MMI to prevent RE generation, a background plasma of 1st MMI impurities is formed which make the second MMI inefficient to mitigate RE beams inefficient, as observed in the JET tokamak. In this thesis, the physics of the interaction between the RE beam and the mitigation MMI in the presence of a cold background plasma is studied
Liang, Anshu. "Understanding the low to high confinement transition in tokamak plasmas." Electronic Thesis or Diss., Aix-Marseille, 2023. http://theses.univ-amu.fr.lama.univ-amu.fr/230112_LIANG_826zuy182lisgpn946fzpk544n_TH.pdf.
Full textThe works presented in this thesis are devoted to understand the physical mechanism of the L-H transition. The driving mechanism of the velocity shear in the plasma edge has been studied using lower hybrid current drive (LHCD) power injection on the HL-2A tokamak in China. It has been shown that the increase of the velocity shear is mainly driven by the ion diamagnetic term of the radial electric field Er. During the L-H transition, it is observed that the ion diamagnetic term of the radial electric field Er plays a dominant role in the increase of velocity shear, while the contributions of the poloidal and toroidal velocity terms are negligible. The velocity shear must reach a critical value to allow the L-H transition to occur. This means that the critical value plays a role as a velocity shear threshold for the L-H transition. In addition, the stimulated effect of supersonic molecular beam injection (SMBI) on the L-H transition has also been investigated on HL-2A. The results suggest that SMBI could be a reliable method for reducing the L-H transition power threshold and controlling the L-H transition in future fusion reactors. Finally, efforts have been made on the optimization of LHCD coupling on the WEST tokamak in France and an analysis of the LH wave coupling in WEST plasmas has been carried out. The analysis shows that the toroidal reshaping of the fully-active-multijunction launcher carried out before its installation in WEST was successful. The experiments have also shown that the reshaping of the passive-active-multijunction launcher is necessary in order to avoid overheating on the launcher front in long pulses