Current drive by EC waves in the presence of magnetic islands and transport

Rosa, Paulo Ricardo da Silva; Ziebell, L. F.

doi:10.1088/0741-3335/50/9/095002

Cited by 9 publications

(19 citation statements)

References 18 publications

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“…For example, under some conditions, the cross-field heat conductivity has been found to be strongly reduced inside the island [30,31]. Theoretical and numerical works have shown that the different magnetic topologies due to the presence of a magnetic island can have important consequences for the flux-surface averaged quasilinear diffusion and the consequent power density deposition profile as well as drive current density profile [32][33][34]. These points will be the subject of future work.…”

Section: Discussionmentioning

confidence: 91%

Consequences of finite transport on the effectiveness of ECCD for neoclassical tearing mode stabilization in ITER

Bertelli

Westerhof

2009

Nucl. Fusion

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One of the main aims of the ITER electron cyclotron resonance heating (ECRH) system, in particular of the Upper Port Launcher, is the control of magnetohydrodynamics instabilities. This control typically requires non-inductively driven currents with a high degree of localization, i.e. with a very narrow profile. A numerical analysis of the effect of the radial diffusion of the EC driven current carrying electrons has been performed in order to estimate the effectiveness of electron cyclotron current drive (ECCD) for neoclassical tearing mode (NTM) stabilization. In particular, Fokker–Planck calculations including radial diffusion for the case of the ITER ECRH Upper Port Launcher are presented. These show a significant decrease in the local current density when radial diffusion at a rate of only 1 m2 s−1 is included and consequently a broadening of the profile with a drop in the predicted efficiency for NTM control. Furthermore, it is shown that a simple formula combining the effect of the radial diffusion and the width of the EC power deposition profile reproduces quite accurately the maximum EC driven current density, which is the more relevant number in determining the NTM suppression figure of merit, for typical ITER parameters.

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Section: Discussionmentioning

confidence: 91%

Consequences of finite transport on the effectiveness of ECCD for neoclassical tearing mode stabilization in ITER

Bertelli

Westerhof

2009

Nucl. Fusion

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“…The main effect of the presence of islands is the reduction in the area of the magnetic surface where the wave power is deposed and a consequent increase in the EC power density over the resonant surface as compared with the case without islands. At a steady state, the value of the current density is proportional to the ratio between the area of the resonant surface in the case without the perturbation and the area of the surface near the islands' centre [7].…”

Section: Introductionmentioning

confidence: 99%

The role of the RF induced electric field in the current drive by EC waves in the presence of magnetic islands

Rosa¹,

Ziebell²

2010

Nucl. Fusion

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In this paper we discuss the role played by a radiofrequency induced electric field on the current drive efficiency of electron cyclotron (EC) waves when there are locked or rotating magnetic islands in the plasma. The problem is addressed by numerical solution of the Fokker–Planck equation within the framework of the quasilinear theory incorporating realistic features of the geometry of the magnetic islands. The modes 2/1 and 3/2 are analysed. Our main result is the reduction, although not the complete suppression, of the level of the current driven by the waves in the short time scale needed for the induced field to diffuse away from the islands region. Another finding is the suppression of quasilinear effects on the EC current drive efficiency in the case of locked islands for both 2/1 and 3/2 modes.

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“…The explicit form of the different coefficients appearing in the equation ( 6) may be found in the literature (for example, [16]).…”

Section: The Fokker-planck Equation and Numerical Schemementioning

confidence: 99%

Radio-frequency current drive efficiency in the presence of ITBs and a dc electric field

2009

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This paper discusses the current drive efficiency by the combined action of EC and LH waves in the presence of a dc electric field and transport, with an internal transport barrier. The transport is assumed to be produced by magnetic fluctuations. The study explores the different barrier parameters and their influence on the current drive efficiency. We study the subject by numerically solving the Fokker–Planck equation. Our main result is that the barrier depth and barrier width are important to determine the correct shape of the current density profile but not to determine the current drive efficiency, which is very little influenced by these parameters. We also found similar results for the influence of the level of magnetic fluctuations on the current density profile and on the current drive efficiency.

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Current drive by EC waves in the presence of magnetic islands and transport

Cited by 9 publications

References 18 publications

Consequences of finite transport on the effectiveness of ECCD for neoclassical tearing mode stabilization in ITER

Consequences of finite transport on the effectiveness of ECCD for neoclassical tearing mode stabilization in ITER

The role of the RF induced electric field in the current drive by EC waves in the presence of magnetic islands

Radio-frequency current drive efficiency in the presence of ITBs and a dc electric field

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