Perturbative studies of turbulent transport in fusion plasmas

Mantica, P.; Ryter, F.

doi:10.1016/j.crhy.2006.06.004

Cited by 52 publications

(81 citation statements)

References 56 publications

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“…In experiments, short time perturbations to the plasma are triggered by cooling the edge of the plasma using a burst of influx of heavy impurities triggered by laser ablation. 2 The resulting cold pulse is observed to traverse the plasma with speeds much higher than predicted from transport modeling. Often a reversal in the cold pulse polarity is observed, i.e., a temperature increase at certain plasma radius follows the cold pulse trigger instead of a cooling.…”

Section: Introductionmentioning

confidence: 94%

Cold pulse and rotation reversals with turbulence spreading and residual stress

et al. 2016

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Articles you may be interested inTurbulence induced radial transport of toroidal momentum in boundary plasma of EAST tokamak Phys. Plasmas 23, 062309 (2016) Transport modeling based on inclusion of turbulence spreading and residual stresses shows internal rotation reversals and polarity reversal of cold pulses, with a clear indication of nonlocal transport effects due to fast spreading in the turbulence intensity field. The effects of turbulence spreading and residual stress are calculated from the gradient of the turbulence intensity. In the model presented in this paper, the flux is carried by the turbulence intensity field, which in itself is subject to radial transport effects. The pulse polarity inversion and the rotation profile reversal positions are close to the radial location of the stable/unstable transition. Both effects have no direct explanation within the framework of classical transport modeling, where the fluxes are related directly to the linear growth rates, the turbulence intensity profile is not considered and the corresponding residual stress is absent. Our simulations are in qualitative agreement with measurements from ohmically heated plasmas. Rotation reversal at a finite radius is found in situations not displaying saturated confinement, which we identify as situations where the plasma is nearly everywhere unstable. As an additional and new effect, the model predicts a perturbation of the velocity profile following a cold pulse from the edge. This allows direct experimental confirmation of both the existence of residual stress caused by turbulence intensity profiles and fundamental ideas of transport modeling presented here. Published by AIP Publishing.

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Section: Introductionmentioning

confidence: 94%

Cold pulse and rotation reversals with turbulence spreading and residual stress

et al. 2016

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“…exploiting the additional information contained in the dynamic response of the plasma rotation to a time variation of the torque source. Modulation at a suitable frequency has the advantage of optimizing the S/N ratio by averaging over several cycles and has been used successfully to study electron and more recently ion heat transport, and also particle and impurity transport (see [18] for a recent review). Its application to momentum transport studies using Neutral Beam Injection (NBI) modulation is a recent development, with a couple of studies reported in JT-60U [19,20], one experiment reported in JET [21,22,23] and one in DIII-D [24].…”

Section: Introductionmentioning

confidence: 99%

Perturbative studies of toroidal momentum transport using neutral beam injection modulation in the Joint European Torus: Experimental results, analysis methodology, and first principles modeling

Mantica

Tala²,

Ferreira³

et al. 2010

Physics of Plasmas

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ABSTRACT.Perturbative experiments have been carried out in the JET tokamak in order to identify the diffusive and convective components of toroidal momentum transport. The torque source was modulated either by modulating tangential neutral beam power or by modulating in anti-phase tangential and normal beams to produce a torque perturbation in the absence of a power perturbation. The resulting periodic perturbation in the toroidal rotation velocity was modelled using time dependent transport simulations in order to extract empirical profiles of momentum diffusivity and pinch. Details of the experimental technique, data analysis and modelling are provided. The momentum diffusivity in the core region (0.2<ρ<0.8) was found to be close to the ion heat diffusivity ( χ φ / χ i~0 .7-1.7) and a significant inward momentum convection term, up to 20m/s, was found, leading to an effective momentum diffusivity significantly lower than the ion heat diffusivity (

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“…These and other non-linear transport properties have been analyzed using perturbations (often via the heat pulse diffusivity χ HP ) at different operating points and comparing them to each other and to steadystate results (power balance diffusivity χ P B ) [34,2]. Alternatively, model codes based on the physics are used to fit parameters of the non-linear models, e.g., [20,35]. The problem with such an approach is that they generally prove the existence of a non-linearity, but their interpretations depend on the used transport model.…”

Section: Introductionmentioning

confidence: 99%

“…This list is far from exhaustive and for a more complete overview of such experiments and its history the reader is referred to [2,3,20].…”

Section: Introductionmentioning

confidence: 99%

New evidence and impact of electron transport non-linearities based on new perturbative inter-modulation analysis

et al. 2017

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Abstract.A new methodology to analyze non-linear components in perturbative transport experiments is introduced. The methodology has been experimentally validated in the Large Helical Device (LHD) for the electron heat transport channel. Electron cyclotron resonance heating (ECRH) with different modulation frequencies by two gyrotrons have been used to directly quantify the amplitude the non-linear component at the inter-modulation frequencies. The measurements show significant quadratic non-linear contributions, but also the absence of cubic and higher order components. The non-linear component is analyzed using Volterra series, which is the non-linear generalization of transfer functions. This allows to study the radial distribution of the non-linearity of the plasma and to reconstruct linear profiles in the case the measurements were not distorted by non-linearities. The reconstructed linear profiles are significantly different from the measured profiles showing the significant impact the non-linearity can have.

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Perturbative studies of turbulent transport in fusion plasmas

Cited by 52 publications

References 56 publications

Cold pulse and rotation reversals with turbulence spreading and residual stress

Cold pulse and rotation reversals with turbulence spreading and residual stress

Perturbative studies of toroidal momentum transport using neutral beam injection modulation in the Joint European Torus: Experimental results, analysis methodology, and first principles modeling

New evidence and impact of electron transport non-linearities based on new perturbative inter-modulation analysis

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