The main characteristics of toroidal Alfvén eigenmodes (TAEs) have been successfully investigated in JET (Joint European Torus) using the scheme of sweeping-frequency external excitation with tracking of the synchronously-detected resonances. However, due to technical limitations, only modes with low values of the toroidal mode number n ⩽ 7 could be effectively excited and unambiguously identified by the Alfvén Eigenmode Active Diagnostic (AEAD) system. This represents a serious restriction because theoretical models indicate that medium-n Alfvén eigenmodes (AEs) are the most prone to be destabilized by energetic particles in ignited plasmas and, therefore, reliable measurement of their damping rates remains a relevant issue to properly access their effect in ignited plasmas. For this reason, a major upgrade of the AEAD system has been carried out aiming at providing a state-of-the-art excitation and real-time detection system for the planned DT campaign in JET. This required the development of a new type of radio frequency amplifier and filter, not commercially available, and also a control system. In this paper, details of the concepts that are relevant to understand the operation of the new system in the next experimental campaigns are presented, as are the results of numerical simulations to model its performance.

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. V C 2016 AIP Publishing LLC. [http://dx

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 v vi 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. AbstractIn 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 eects 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 conguration. 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 elds 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 dierent toroidal numbers n, excited by the new JET antenna system.In particular, it was investigated in detail the eect of the phases of the supply currents of the dierent 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 privivii viii leged 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.

We perform special-relativistic one-dimensional hydrodynamic simulations to study the combustion of hadronic matter into quark matter in neutron star conditions. For the equation of state, we use a relativistic mean-field Walecka model for hadronic matter and the MIT bag model for quark matter. We study the growth of a small core of quark matter surrounded by hadronic matter at constant density, where both regions are initially at rest. We show that a strong detonation front propagates into hadronic matter converting it into quark matter. We find that the timescale for the conversion of a compact star is around tens of microseconds.

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