4 research outputs found
Diagnóstico de plasma en Tokamak utilizando ondas de Alfvén
Descargue el texto completo en el repositorio institucional de la Universidade de São Paulo: https://doi.org/10.11606/T.43.2015.tde-14082015-110334El trabajo investiga la excitación de automodos de Alfvén en tokamaks, utilizando
una descripción realista de las antenas externas a la columna de plasma en los
tokamaks TCABR y JET. El modelo teórico de excitación de ondas de Alfvén en
una columna de plasma cilíndrico (modos Alfvén globales - GAWs) y el modelo
más complejo de las ondas de Alfvén en plasmas toroidales (automodos toroidales
de Alfvén - TAEs) son estudiados. La excitación de los modos TAEs en el JET se
estudian utilizando los códigos HELENA (reconstruye el equilibrio
magnetohidrodinámico) y CASTOR (calcula los campos perturbados asociados a
inestabilidades del modelo magnetohidrodinámico resistivo). Determinamos la
calidad del espectro y las funciones asociadas a los TAEs, con diferentes números
toroidales, excitados por el sistema de antenas. Se investigó el efecto de las fases
de las corrientes de alimentación de los diferentes módulos de antenas sobre la
calidad del espectro excitado, utilizando un método original, implementado en
este trabajo, para utilizar el CASTOR. Los resultados indican que aunque la
excitación de un modo dado puede ser privilegiada por una elección óptima de
fases, los modos satélite también pueden excitarse con mayor amplitud, de modo
que la pureza del espectro no se mejora sustancialmente.In this work we investigated the excitation of Alfvén eigenmodes in tokamaks using external antennas to the plasma column. The basic theory of Alfvén waves is revised, including non-ideal effects such as resistivity. Then the theoretical model for excitation Alfvén waves in a cylindrical plasma column, developed by Kurt Appert, is shown in detail, as an introduction to the more complex problem of Alfvén waves in toroidal plasmas. The cylindrical model is implemented in a numerical code, which is used to study the excitation of Global Alfvén Waves (GAWs), below to the so-called Continuum of Alfvén, in TCABR and JET tokamaks, using a realistic description of their antenna systems. In the sequel, it is given a brief description of Toroidal Alfvén eigenmodes (TAEs) that are excited in the gaps of the Continuum of Alfvén created by the periodicity condition of the toroidal configuration. The excitement of these modes in JET tokamak is studied using the codes HELENA, for reconstruction of magneto-hydrodynamic equilibrium, and CASTOR, which calculates the perturbed fields in this equilibrium, coupled with instability or modes excited within the magneto-resistive hydrodynamic model. This study was carried out in order to determine, consistently, the spectrum quality and the eigenmodes associated with TAEs, with different numbers toroidal n, excited by the new JET antenna system. In particular, it was investigated in detail the effect of the phases of the supply currents of the different modules (eight) of the antenna system in the quality of the excited spectrum, using an original method, implemented in this work, based on the CASTOR code. The results indicate that, although the excitation of a certain mode may be a privileged by an optimized choice of phases, satellite modes can also be excited with higher amplitude, so that the purity of the spectrum is not substantially improved. This is the main result obtained in this work.Brasil. Ministério da Educação. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes
Effective photon mass and exact translating quantum relativistic structures
Using a variation of the celebrated Volkov solution, the Klein-Gordon
equation for a charged particle is reduced to a set of ordinary differential
equations, exactly solvable in specific cases. The new quantum relativistic
structures can reveal a localization in the radial direction perpendicular to
the wave packet propagation, thanks to a non-vanishing scalar potential. The
external electromagnetic field, the particle current density and the charge
density are determined. The stability analysis of the solutions is performed by
means of numerical simulations. The results are useful for the description of a
charged quantum test particle in the relativistic regime, provided spin effects
are not decisive
Diagnóstico de Plasma em Tokamak Utilizando Ondas de Alfvén
In this work we investigated the excitation of Alfvén eigenmodes in tokamaks using external antennas to the plasma column. The basic theory of Alfvén waves is revised, including non-ideal effects such as resistivity. Then the theoretical model for excitation Alfvén waves in a cylindrical plasma column, developed by Kurt Appert, is shown in detail, as an introduction to the more complex problem of Alfvén waves in toroidal plasmas. The cylindrical model is implemented in a numerical code, which is used to study the excitation of Global Alfvén Waves (GAWs), below to the so-called Continuum of Alfvén, in TCABR and JET tokamaks, using a realistic description of their antenna systems. In the sequel, it is given a brief description of Toroidal Alfvén eigenmodes (TAEs) that are excited in the gaps of the Continuum of Alfvén created by the periodicity condition of the toroidal configuration. The excitement of these modes in JET tokamak is studied using the codes HELENA, for reconstruction of magneto-hydrodynamic equilibrium, and CASTOR, which calculates the perturbed fields in this equilibrium, coupled with instability or modes excited within the magneto-resistive hydrodynamic model. This study was carried out in order to determine, consistently, the spectrum quality and the eigenmodes associated with TAEs, with different numbers toroidal n, excited by the new JET antenna system. In particular, it was investigated in detail the effect of the phases of the supply currents of the different modules (eight) of the antenna system in the quality of the excited spectrum, using an original method, implemented in this work, based on the CASTOR code. The results indicate that, although the excitation of a certain mode may be a privileged by an optimized choice of phases, satellite modes can also be excited with higher amplitude, so that the purity of the spectrum is not substantially improved. This is the main result obtained in this work.Neste trabalho é investigada a excitação de modos própios de Alfvén em tokamaks, utilizando antenas externas à coluna de plasma. A teoria básica das ondas de Alfvén é revista, incluindo efeitos não ideais, como resistividade. A seguir, o modelo teórico para excitação de ondas de Alfvén numa coluna cilindrica de plasma, desenvolvido por Kurt Appert, é apresentado em detalhe, como introdução ao problema mais complexo de ondas de Alfvén em plasmas toroidais. O modelo cilindrico é implementado em um código numérico, que é utilizado para estudar a excitação de modos globais de Alfvén (GAWs - Global Alfvén Waves), abaixo do chamado Continuo de Alfvén, nos tokamaks TCABR e JET, utilizando uma descrição realista de seus sistemas de antenas. A seguir é feita uma breve descrição dos auto modos toroidais de Alfvén (TAEs - Toroidal Alfvén Eigenmodes) que são excitados nas brechas do Continuo de Alfvén criadas pela condição de periodicidade em configurações toroidais. A excitação desses modos no tokamak JET é estudada utilizando os códigos HELENA, para reconstrução do equilíbrio magneto-hidrodinâmico, e CASTOR, que calcula os campos perturbados nesse equilíbrio, associados a instabilidades ou modos excitados, dentro do modelo magneto-hidrodinâmico resistivo. Esse estudo foi feito com o objetivo de determinar, de forma consistente, a qualidade do espectro e as auto-funções associadas a TAEs, com diferentes números toroidais n, excitados pelo atual sistema de antenas do JET. Em particular, foi investigado em detalhe o efeito das fases das correntes de alimentação dos diferentes módulos (oito) do sistema de antenas na qualidade do espectro excitado, utilizando um método original, implementado neste trabalho, de utilizar o código CASTOR. Os resultados indicam que embora a excitação de um determinado modo possa ser privilegiado por uma escolha ótima das fases, modos satélites também podem ser excitados com maior amplitude, de modo que a pureza do espectro não é substancialmente melhorada. Este é o principal resultado obtido neste trabalho