Momentum transport in the vicinity of <i>q<sub>min</sub></i> in reverse shear tokamaks due to ion temperature gradient turbulence

Singh, Rameswar; Jhang, Hogun; Diamond, P. H.

doi:10.1063/1.4861625

Cited by 7 publications

(2 citation statements)

References 52 publications

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“…This indicates that the position of ITB is sensitive not to the momentum source profile but to the q min surface, which is qualitatively consistent with the experimental observation that ITB is triggered inside the q min surface and evolved toward the q min surface [3,23]. The effect of reversed magnetic shear configuration on parallel momentum flux is also discussed in [24,25]. The novelty of this study is that the self-consistent mean flow coupled with the parallel flow triggers ITB formation in flux-driven toroidal ITG turbulence.…”

Section: Itb Formation By Toroidal Momentum Injection In Reversed Mag...supporting

confidence: 83%

ITB formation in gyrokinetic flux-driven ITG/TEM turbulence

Imadera¹,

Kishimoto²

2022

Plasma Phys. Control. Fusion

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The formation mechanism of Internal Transport Barriers (ITBs) in flux-driven turbulence is studied by means of the full-f gyrokinetic code GKNET. In the adiabatic electron case with a weak magnetic shear configuration, toroidal momentum injection can change the radial mean electric field E_r through the radial force balance, leading to a kind of driven ITB formation in which the ion thermal diffusivity by Ion Temperature Gradient (ITG) turbulence decreases to the neoclassical transport level. Only co-current toroidal rotation in the outer region can benefit the ITB formation, which mechanism is identified to originate from a positive feedback loop between the radial E_r shear and resultant momentum flux. On the other hand, in the kinetic electron case with a reversed magnetic shear configuration, robust co-intrinsic rotation is driven near the q_min surface in ITG turbulence and sustain the E_r shear through the radial force balance, leading to the spontaneous reduction of ion turbulent thermal diffusivity, while it is not observed in the adiabatic electron case. In the presence of electron heating, counter-intrinsic rotation by Trapped Electron Mode (TEM) turbulence is selectively driven in the negative magnetic shear region, which provides steeper E_r shear formation and resultant larger reduction of ion turbulent thermal diffusivity. It indicates that the co-existence of different modes can trigger the discontinuity near q_min and then spontaneous ITB formation.

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Section: Itb Formation By Toroidal Momentum Injection In Reversed Mag...supporting

confidence: 83%

ITB formation in gyrokinetic flux-driven ITG/TEM turbulence

Imadera¹,

Kishimoto²

2022

Plasma Phys. Control. Fusion

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“…If the mode frequency (𝜔) is sufficiently large compared to the E × B shearing rate, which is used for the quantitative assessment of the fluctuation suppression, then the above equation can be expressed as [25] 𝑅(𝑦)…”

Section: 𝑒𝐵0𝜔mentioning

confidence: 99%

Effect of Sheared Magnetic Field on E × B Drift Instability in Plasma

Nasrin,

Das,

Bose

2023

Ukr. J. Phys.

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The influence of the magnetic shear on ion drift waves has been investigated for plasmas in the plane slab geometry with a density gradient. A differential equation is derived to describe the mode structure along the density gradient. The magnetic shear localizes the mode around a mode-rational surface, which is perpendicular to the magnetic field. The non-local growth rate turned out to be smaller as compared to the shearless one. The magnetic shear stabilizes long wavelength modes (kρi < 1 ), whereas it destabilizes, as the mode tends toward the short wavelength region, where the density gradient provides a destabilizing effect for the magnetic shear-driven resistive drift mode. However, the effect due to the collision frequency is significantly low in our analysis. The combined effects of E×B flows and the magnetic shear enhance the confinement over a narrow radial region with an internal transport barrier, where stability is attained.

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A quasi-linear analysis of the impurity effect on turbulent momentum transport and residual stress

Jhang

Singh

2015

Physics of Plasmas

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We study the impact of impurities on turbulence driven intrinsic rotation (via residual stress) in the context of the quasi-linear theory. A two-fluid formulation for main and impurity ions is employed to study ion temperature gradient modes in sheared slab geometry modified by the presence of impurities. An effective form of the parallel Reynolds stress is derived in the center of mass frame of a coupled main ion-impurity system. Analyses show that the contents and the radial profile of impurities have a strong influence on the residual stress. In particular, an impurity profile aligned with that of main ions is shown to cause a considerable reduction of the residual stress, which may lead to the reduction of turbulence driven intrinsic rotation.

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Momentum transport in the vicinity of q_min in reverse shear tokamaks due to ion temperature gradient turbulence

Cited by 7 publications

References 52 publications

ITB formation in gyrokinetic flux-driven ITG/TEM turbulence

ITB formation in gyrokinetic flux-driven ITG/TEM turbulence

Effect of Sheared Magnetic Field on E × B Drift Instability in Plasma

A quasi-linear analysis of the impurity effect on turbulent momentum transport and residual stress

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Momentum transport in the vicinity of qmin in reverse shear tokamaks due to ion temperature gradient turbulence

Cited by 7 publications

References 52 publications

ITB formation in gyrokinetic flux-driven ITG/TEM turbulence

ITB formation in gyrokinetic flux-driven ITG/TEM turbulence

Effect of Sheared Magnetic Field on E × B Drift Instability in Plasma

A quasi-linear analysis of the impurity effect on turbulent momentum transport and residual stress

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Momentum transport in the vicinity of q_min in reverse shear tokamaks due to ion temperature gradient turbulence