Identification of the Alfvén wave resonances in the TCABR tokamak by the microwave reflectometry

Ruchko, L.; Galvão, R. M. O.; Lerche, E.; Elfimov, A. G.; Bellintani, V.; Elizondo, Juan Iraburu; Fagundes, Aluisio Neves; Fonseca, A.; Kuznetsov, Yu.K.; Nascimento, I. C.; Sá, W.P. de; Sanada, Edson Kenzo; Silva, R. P. da; Valencia, R.

doi:10.1590/s0103-97332004000800037

Cited by 2 publications

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References 16 publications

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“…The registration of the density oscillations, which are excited by LAW in the TCABR tokamak, by the reflectometer at fixed frequency, was presented in Ref. 3. In this paper, we present experimental results showing that the frequency scanning reflectometry is effective for the registration of the LAW induced density oscillations, and that it offers some advantages for their identification.…”

Section: Introductionmentioning

confidence: 78%

Registration of Alfvén resonances in TCABR tokamak by the scanning reflectometer at sideband frequencies

Ruchko

Elfimov

Teixeira

et al. 2011

Review of Scientific Instruments

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A frequency scanning O-mode reflectometer was used for studies of plasma density oscillations during local Alfvén wave (LAW) excitation in the Tokamak Chauffage Alfvén Brésilien (TCABR) at the frequency fA = 5 MHz. It was found that the spectrum of the reflectometer output signal, which consists mainly of the “beat” frequency fB, is modified by the LAW excitation, and two additional frequency peaks appear, which are symmetrical in relation to the LAW excitation frequency f = fA ± fB. This result opens the possibility to improve the efficiency of studying the LAW induced density oscillations. The symmetry of these frequency peaks yields the possibility of finding the microwave frequency at which the reflectometer cutoff layer coincides with radial position of the LAW resonance zone in the TCABR tokamak.

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Section: Introductionmentioning

confidence: 78%

Registration of Alfvén resonances in TCABR tokamak by the scanning reflectometer at sideband frequencies

Ruchko

Elfimov

Teixeira

et al. 2011

Review of Scientific Instruments

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“…Since we consider small-amplitude perturbations with frequencies ω ω ci ω ce in a cold current-carrying plasma, where 3.1. Theory of waves in a cold magnetized cylindrical plasma column 31 ω ci and ω ce are the cyclotron frequency for ions and electrons, respectively, we can assume that the mass of the electrons is negligible m i m e −→ 0 (innite mobility along the magnetic eld). Taking into account these approximations and considerations, we obtain from the equation of motion:…”

Section: Cylindrical Model Of Alfvén Wavesmentioning

confidence: 99%

Plasma Diasnostic in Tokamaks Using Alfvén Waves

Manrique¹

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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.

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Identification of the Alfvén wave resonances in the TCABR tokamak by the microwave reflectometry

Cited by 2 publications

References 16 publications

Registration of Alfvén resonances in TCABR tokamak by the scanning reflectometer at sideband frequencies

Registration of Alfvén resonances in TCABR tokamak by the scanning reflectometer at sideband frequencies

Plasma Diasnostic in Tokamaks Using Alfvén Waves

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