Resumo O conhecimento dos parâmetros macroscópicos do plasma, tais como a densidade e temperatura, bem como sua evolução e dependência espacial são fundamentais para a compreensão e controle do plasma. Esses parâmetros são essenciais para descrição dos eventos associados a fenômenos de transporte, atividade MHD, estudos de regime de confinamento melhorado (modo H), entre outros. O perfil de temperatura e densidade de íons e elétrons caracteriza um parâmetro extremamente importante em plasmas termonucleares que é o perfil de pressão. Para obter esses perfis foram utilizados os principais diagnósticos disponíveis no tokamak TCABR: espalhamento Thomson, interferometria, reflectometria, ECE e diagnósticos espectroscópicos. O espalhamento Thomson é capaz de determinar o perfil de temperatura e densidade eletrônica durante o disparo; já o diagnóstico ECE é capaz de medir a temperatura eletrônica sob certas condições de descargas. Já os diagnósticos de interferometria e reflectometria medem a densidade eletrônica integrada e a densidade eletrônica local, respectivamente. Por fim, o perfil de temperatura iônica pode ser estimado através do alargamento Doppler das linhas de emissão de impurezas. Tais dados são usados para reconstrução do perfil de pressão, em diferentes tipos de descargas no tokamak, bem como possibilitar a reconstrução do equilíbrio. Não obstante, esses diagnósticos podem fornecer informações como estimativa do Z efetivo do plasma, da velocidade de rotação, e das condições que promovem disrupção no TCABR / The knowledge of the plasma macroscopic parameters such as density and temperature as well as their temporal and spatial evolution are fundamental to the understanding and control of the plasma. These parameters are essential for description of events associated with transport phenomena, magnetohydrodynamics (MHD) activity, improved confinement studies (H mode), among others. The temperature and density profiles of electrons and ions define an extremely important parameter in thermonuclear plasmas that is the pressure profile. To measure these profiles we used all the main diagnostics available in the TCABR tokamak: Thomson scattering, interferometry, reflectometry, ECE and spectroscopic diagnostics. The Thomson scattering is able to determine the local electron temperature and density in the plasma discharge; ECE diagnostic is also able to measure the local electron temperature under certain plasma discharge conditions. And the interferometric and reflectometric diagnostics measure the line-integrated electronic density and the local electronic density, respectively. Finally, the ion temperature profile can be estimated by the Doppler broadening of the impurity line emissions. These data are used to reconstruct the pressure profile in different types of discharges in tokamak, and to enable the MHD equilibrium reconstruction. Nevertheless, these analyzes can provide information to estimate the plasma Z effective, plasma rotation velocity, and the conditions that promote the disruption in the TCABR.

Resumo O conhecimento dos parâmetros macroscópicos do plasma, tais como a densidade e temperatura, bem como sua evolução e dependência espacial são fundamentais para a compreensão e controle do plasma. Esses parâmetros são essenciais para descrição dos eventos associados a fenômenos de transporte, atividade MHD, estudos de regime de confinamento melhorado (modo H), entre outros. O perfil de temperatura e densidade de íons e elétrons caracteriza um parâmetro extremamente importante em plasmas termonucleares que é o perfil de pressão. Para obter esses perfis foram utilizados os principais diagnósticos disponíveis no tokamak TCABR: espalhamento Thomson, interferometria, reflectometria, ECE e diagnósticos espectroscópicos. O espalhamento Thomson é capaz de determinar o perfil de temperatura e densidade eletrônica durante o disparo; já o diagnóstico ECE é capaz de medir a temperatura eletrônica sob certas condições de descargas. Já os diagnósticos de interferometria e reflectometria medem a densidade eletrônica integrada e a densidade eletrônica local, respectivamente. Por fim, o perfil de temperatura iônica pode ser estimado através do alargamento Doppler das linhas de emissão de impurezas. Tais dados são usados para reconstrução do perfil de pressão, em diferentes tipos de descargas no tokamak, bem como possibilitar a reconstrução do equilíbrio. Não obstante, esses diagnósticos podem fornecer informações como estimativa do Z efetivo do plasma, da velocidade de rotação, e das condições que promovem disrupção no TCABR / The knowledge of the plasma macroscopic parameters such as density and temperature as well as their temporal and spatial evolution are fundamental to the understanding and control of the plasma. These parameters are essential for description of events associated with transport phenomena, magnetohydrodynamics (MHD) activity, improved confinement studies (H mode), among others. The temperature and density profiles of electrons and ions define an extremely important parameter in thermonuclear plasmas that is the pressure profile. To measure these profiles we used all the main diagnostics available in the TCABR tokamak: Thomson scattering, interferometry, reflectometry, ECE and spectroscopic diagnostics. The Thomson scattering is able to determine the local electron temperature and density in the plasma discharge; ECE diagnostic is also able to measure the local electron temperature under certain plasma discharge conditions. And the interferometric and reflectometric diagnostics measure the line-integrated electronic density and the local electronic density, respectively. Finally, the ion temperature profile can be estimated by the Doppler broadening of the impurity line emissions. These data are used to reconstruct the pressure profile in different types of discharges in tokamak, and to enable the MHD equilibrium reconstruction. Nevertheless, these analyzes can provide information to estimate the plasma Z effective, plasma rotation velocity, and the conditions that promote the disruption in the TCABR.

Les effets auto-consistantes sont omniprésents dans les plasmas de fusion. Ils sont dus au fait que les équations de Maxwell qui décrivent l’évolution des champs électromagnétiques contiennent la densité de charge et de courant des particules.D’autre côté à son tour les trajectoires des particules sont influencés par les champs à travers les équations de mouvement ( où l’équation de Vlasov). Le résultat decette interaction auto-consistente se résume dans un effet cumulatif qui peut causer le déconfinement de plasma à l’intérieur d’une machine de fusion. Ce travail de thèse traite les problèmes liés à l’amélioration de confinement de plasma de fusion dans le cadre des approches hamiltonienne et lagrangien par le contrôle de transport turbulent et la création des barrières de transport. Les fluctuations auto-consistantes de champs électromagnétiques et de densités des particules sont à l’origine de l’apparition des instabilités de plasma qui sont à son tour liés aux phénomènes de transport. Dans la perspective de comprendre les mécanismes de la turbulence sousjacente,on considère ici l’application des méthodes hamiltoniennes pour des plasmasnon-collisionnelles / This thesis deals with dynamicla investigation of magnetically confined fusion plasmas by using Lagrangian and Hamilton formalisms. It consists of three parts. The first part is devoted to the investigation of barrier formation for the EXB drift model by means of the Hamiltonian control method. The strong magnetic field approach is relevant for magnetically confined fusion plasmas ; this is why at the first approximation one can consider the dynamics of particles driven by constant and uniform magnetic field. In this case only the electrostatic turbulence is taken into account. During this study the expressions for the control term (quadratic in perturbation amplitude) additive to the electrostatic potential, has been obtained. The effeciency of such a control for stopping turbulent diffusion has been shown analytically abd numerically. The second and the third parts of this thesis are devoted to study of self consistent phenomena in magnetized plasmas through the Maxwell-Vlasov model. In particular, the second part of this thesis treats the problem of the monumentum transport by derivation of its conservation law. the Euler-Poincare variational principle (with constrained variations) as well as Noether's theorem is apllied here. this derivation is realized in two cases : first, in electromagnetic turbulence case for the full Maxwell-Vlasov system, and then in electrostatic turbulence case for the gyrokinetic Maxwell-Vlasov system. Then the intrinsic mechanisms reponsible for the intrinsic plama rotation, that can give an important in plasma stabilization, are identified. The last part of this thesis deals with dynamicla reduction for the Maxwell-Vlaslov model. More particularly; the intrisic formulation for the guiding center model is derived. Here the term 'intrinsis" means that no fixed frame was used during its construction. Due to that not any problem related to the gyrogauge dependence of dynamics appears. The study of orbits of trapped particles is considered as one of the possible for illustration of the first step of such a dynamical reduction.

科学研究費補助金 研究種目:基盤研究(B)(2) 課題番号:11480113 研究代表者:上杉 喜彦 研究期間:1999-2001年度

Next-generation and present fusion devices such as the Joint European Torus (JET) aim for plasma operations in H-mode, a plasma regime with high confinement and low loss of energy and fuel that results from a barrier for heat and particle transport at the plasma edge, the pedestal. Due to steep gradients of the density, temperature and pressure profiles, the pedestal experiences instabilities called Edge-localized-modes (ELMs) which lead to large fluxes of heat and particles that might damage machine components. A theoretical value for the critical threshold for the pressure gradient is determined by the Peeling-Ballooning (PB) model. Although this model has been rather reliable, experiments have shown a discrepancy between the experimental pedestal pressure gradient and the critical pressure gradient determined by the model. A number of experimental gradients were significantly lower than the predicted gradients. The mechanisms responsible for this discrepancy are not fully understood yet. The present hypothesis identifies the relative shift between the positions of the temperature and density pedestals and neutral pressure as key parameters, related to input power and gas dosing among other engineering parameters. Further impact could arise from the assumption of equal ion and electron temperature and the neglecting of the plasma rotation (velocity). In order to investigate this issue more thoroughly, JET established a comprehensive database containing pedestal characteristics. As a part of this work, a software has been implemented to visualize the data since such a tool did not exist yet. The tool enables the plotting of pedestal related parameters while specific data subsets can be selected or neglected. The tool has been used to investigate the impact of ion temperature and plasma rotation on the discrepancy between the theoretical and experimental critical gradients. Hereby, many relevant parameters needed to be constrained to observe an isolated impact of ion temperature and plasma rotation. The results of this investigation support the hypothesis that mainly the relative shift affects the discrepancy between experimental and predicted pressure gradient, but that also the use of experimental ion temperature can contribute to reduce the discrepancy. / Nästa generations och nuvarande fusionsanordningar, såsom Joint European Torus (JET), syftar till plasmaoperationer i H-läge, en plasmaregim med hög inneslutning och låg förlust av energi och bränsle som är ett resultat av en barriär för värme­ och partikeltransport vid plasmakanten, piedestalen. På grund av branta gradienter i densitets-, temperatur- och tryckprofilerna, är piedestalen instabil. Instabiliteten kallas Edge-Localised-Mode (ELM) och leder till stora flöden av värme och partiklar som kan skada maskinkomponenter. En kritisk tröskel för tryckgradienten bestäms av modellen Peeling-Ballooning (PB). Även om denna modell har varit ganska tillförlitlig, har experiment visat en diskrepans mellan den experimentella piedestaltryckgradienten och den kritiska tryckgradienten som bestäms av modellen. Ett antal experimentellt uppmätta kritiska gradienter är signifikant lägre än de förväntade enligt modellen. De mekanismer som ligger bakom denna diskrepans är ännu inte helt klarlagda. Den nuvarande hypotesen identifierar skillander i pos positionen av temperature- och täthetspiedestalen, samt trycket från neutraler som nyckelparametrar, relaterade till inmatad effekt och gasdosering bland andra ingenjörparametrar. Ytterligare påverkan kan uppstå genom antagandet att joner och elektroner har samma temperatur och försummandet av plasmarotationen. För att undersöka denna fråga mer ingående upprättade JET en omfattande databas med piedestalegenskaper. Som en del av detta arbete har en programvara implementerats för att visualisera data eftersom ett sådant verktyg inte funnits tidigare. Verktyget möjliggör plottning av piedestalrelaterade parametrar medan specifika data delmängder kan väljas eller väljas bort. Verktyget har använts för att undersöka inverkan av jontemperatur och plasmarotation på diskrepansen mellan teoretiska och experimentell kritiska tryckgradienten. För denna analys behövde många relevanta parametrar begränsas för att observera en isolerad påverkan av jontemperatur och plasmarotationen. Resultaten av denna undersökning stödjer hypotesen att det relativa skiftet främst påverkar diskrepansen mellan experimentell och förutsedd tryckgradient men att även användning av experimentell jontemperatur kan bidra till att minska diskrepansen.