Observation of inward and outward particle convection in the core of electron cyclotron heated and current driven plasmas in the Tokamak à Configuration Variable

Furno, I.; Weisen, H.

doi:10.1063/1.1576389

Cited by 11 publications

(14 citation statements)

References 26 publications

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“…A sink for hydrogen ions in the plasma is provided by radiative recombination (e). Reaction rate coefficients as a function of temperature for the reactions listed in (3) are shown in figure 1 [7]. It is seen from the comparison of figures 1(a) and (b) that radiative recombination of hydrogen atoms can play a role only in high density plasmas, since the rate coefficient of this process is significantly lower than the ionization and charge exchange rate coefficients.…”

Section: Penetration Of Neutralsmentioning

confidence: 98%

Section: Penetration Of Neutralsmentioning

confidence: 99%

“…It is seen from the comparison of [7]. The labelling corresponds to the reactions listed in (3) Fig . 1A and B that radiative recombination of hydrogen atoms can play a role only in high density plasmas, since the rate coefficient of this process is significantly lower than the ionization and charge exchange rate coefficients.…”

Section: Penetration Of Neutralsmentioning

confidence: 99%

“…The nature of the peaked electron density profiles in tokamaks has been the subject of controversy for a long time [1]. Recent experiments in fully current driven plasmas with negligible particle source in Tore Supra [2] and TCV [3] have shown that substantial peaking is obtained in the absence of the neoclassical Ware pinch [4] (V W are ∝ E tor /B pol ), providing an unambiguous demonstration of the existence of anomalous inward pinches. At the same time, a study of JET H-mode discharges suggested [5] that the effect of edge fuelling may not be negligible, as usually assumed and may contribute to density peaking to the same extent as NBI fuelling.…”

Section: Introductionmentioning

confidence: 99%

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Influence of particle sources on electron density peaking in TCV and JET

Zabolotsky

Weisen²,

Karpushov³

2006

Nucl. Fusion

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Calculations of the particle flux caused by neutrals originating from the edge are performed for TCV and JET, using the one dimensional kinetic transport code Kn1D. The analysis, confirmed by experimental evidence, shows that for TCV and for JET, edge fuelling as well as neutral beam fuelling cannot be responsible for density gradient in the plasma bulk, confirming the presence of inward particle convection. The results corroborate the expectation of a peaked density profile in ITER, despite the lack of bulk particle fuelling.

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Section: Penetration Of Neutralsmentioning

confidence: 98%

Section: Penetration Of Neutralsmentioning

confidence: 99%

Section: Penetration Of Neutralsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Influence of particle sources on electron density peaking in TCV and JET

Zabolotsky

Weisen²,

Karpushov³

2006

Nucl. Fusion

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show abstract

“…In some cases (like, for example, ASDEX-U) the analysis of the experimental results seems to indicate that the Ware pinch alone could be responsible for the observed peaking of the density profile [1]. On the other hand other experiments performed on Tore-Supra and TCV, featuring completely non-inductive plasma current and zero toroidal electric field and where, therefore, there is no Ware pinch, show a significant peaking of the density profile, which suggests that an anomalous pinch should be at work [2][3][4]. Electron density profiles peaked inside the depth of the ionization source have been observed also in DIII-D and TEXTOR [5,6].…”

Section: Introductionmentioning

confidence: 99%

Particle transport and density profile analysis of different JET plasmas

Garzotti

Garbet

Mantica³

et al. 2003

Nucl. Fusion

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Over the last two years, several experiments relevant for the study of particle transport and density profile evolution, have been performed at JET. They can be classified as stationary discharges with and without central particle source due to the beams, quasi-stationary discharges with deuterium gas puffing, deep pellet fuelled discharges and discharges perturbed by cold pulses obtained by shallow pellet injection. All these experimental scenarios have been simulated by means of the JETTO transport code, employing different transport models: purely empirical models and the semi-empirical mixed Bohm/gyro-Bohm transport model, both with the addition of different theory-based expressions for the anomalous particle pinch and the first principle Weiland transport model. The coefficients used to scale the pinch velocity in the purely empirical and in the mixed Bohm/gyro-Bohm model have been varied from shot to shot. In this paper, the results of the simulations are presented. The main conclusions are that, for the cases studied in this paper, the sawtooth activity is the main particle transport mechanism in the plasma centre (r/a ⩽ 0.5). Nevertheless, to reproduce the density profile in the gradient zone (0.5 ⩽ r/a ⩽ 0.9), an anomalous pinch seems to be necessary, at least for L-mode plasmas. This anomalous convective flux is well reproduced by the off-diagonal elements of the transport matrix given by the Weiland model.

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Heating and current drive by electron cyclotron waves

2004

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The physics model of electron cyclotron heating (ECH) and current drive (ECCD) is becoming well validated through systematic comparisons of theory and experiment. This work has shown that ECH and ECCD can be highly localized and robustly controlled in toroidal plasma confinement systems, leading to applications including stabilization of magnetohydrodynamic instabilities like neoclassical tearing modes, control and sustainment of desired profiles of current density and plasma pressure, and studies of localized transport in laboratory plasmas. The experimental work was supported by a broad base of theory based on first principles which is now well encapsulated in linear ray tracing codes describing wave propagation, absorption, and current drive and in fully relativistic quasilinear Fokker–Planck codes describing in detail the response of the electrons to the energy transferred from the wave. The subtle balance between wave-induced diffusion and Coulomb relaxation in velocity space provides an understanding of the effects of trapping of current-carrying electrons in the magnetic well. Strong quasilinear effects and radial transport of electrons, which may broaden the driven current profile, have also been observed under some conditions and appear to be consistent with theory, but in large devices these are usually insignificant. The agreement of theory and experiment, the wide range of established applications, and the technical advantages of ECH support the application of ECH in next-step tokamaks and stellarators.

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Observation of inward and outward particle convection in the core of electron cyclotron heated and current driven plasmas in the Tokamak à Configuration Variable

Cited by 11 publications

References 26 publications

Influence of particle sources on electron density peaking in TCV and JET

Influence of particle sources on electron density peaking in TCV and JET

Particle transport and density profile analysis of different JET plasmas

Heating and current drive by electron cyclotron waves

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