3-D effects on viscosity and generation of toroidal and poloidal flows in LHD

Nagaoka, K.; Ida, K.; Yoshinuma, M.; Suzuki, Yasuhiro; Kamiya, K.; Satake, S.; Tanaka, K.; Yokoyama, M.; Murakami, S.; Osakabe, M.; Takahashi, H.; Seki, R.; Suzuki, C.; Narushima, Y.; Nakano, H.; Kisaki, M.; Ikeda, K.; Tsumori, K.; Takeiri, Y.; Kaneko, O.; Yamada, Hiroyuki

doi:10.1063/1.4807126

Cited by 10 publications

(12 citation statements)

References 30 publications

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“…On LHD, plasma flows have been also studied in previous works which focus on the spontaneous flows driven by the radial electric field and ion temperature gradient [26][27][28]. The measured radial electric fields are found to be in qualitative agreement with those evaluated by NC theory [28][29][30]. However, toroidal flows show some deviations from NC predictions in the discharges without net external input torque [27,30].…”

Section: Introductionmentioning

confidence: 76%

Asymmetry of parallel flow on the Large Helical Device

Chen¹,

Ida²,

Yoshinuma³

et al. 2019

Nucl. Fusion

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An asymmetric parallel return flow, which modifies the parallel component of the flow, is expected to meet the zero divergence of the flow on a flux surface based on the common neoclassical theory for torus plasma. Full flow structure is measured by charge exchange spectroscopy on LHD. Inboard/outboard asymmetry of parallel flow is observed according to the full flow profile measurement. Flow asymmetry is considered to be induced by the Pfirsch-Schlüter flow closely associated with the radial electric field. A linear relationship between the integrated flow asymmetry and the electric potential difference is obtained in different magnetic fields and configurations. A model based upon the incompressibility of the flow is applied to acquire a geometric factor hB, which only connects to magnetic configuration from experiment. Asymmetric component of parallel flow measured is compared with the asymmetric component of parallel flow calculated in the incompressibility condition of flow on the magnetic flux surface. The measured asymmetric flow is consistent with the calculation in the plasma with small toroidal torque input in the inward shifted configuration. However, the measured asymmetric flow is significantly smaller than that calculated for the plasma with large toroidal torque or in the outward shifted configuration. One possible candidate could be the radial transport due to anomalous perpendicular viscosity plus strongly poloidally asymmetric radial flow.

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Section: Introductionmentioning

confidence: 76%

Asymmetry of parallel flow on the Large Helical Device

Chen¹,

Ida²,

Yoshinuma³

et al. 2019

Nucl. Fusion

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“…The N-NB is injected in order to measure the magnetic shear (= (ρ/ι -)(∂ι -/∂ρ)) by motional Stark effect (MSE) spectroscopy [14]. The two N-NBs are injected in the co-and ctr-direction, then the external tangential torque can be canceled out with them, amounting to a few percent of the driving force from each tangential NB [15]. In addition, the ECRH does not contribute to the torque input.…”

Section: Experimental Condition and Resultsmentioning

confidence: 99%

Effects of core stochastization on particle and momentum transport

et al. 2021

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The effects of the stochastic magnetic field in a plasma center produced by electron cyclotron current drive (ECCD) on transport have been revealed. Because the electron temperature profile is flat in the core region, in the case of counter-directed ECCD (ctr-ECCD) against the toroidal magnetic field, the magnetic field is stochastic in the core region with rotational transform ᵼ ∼ 1/3. The particle diffusion coefficient of the ctr-ECCD plasma is approximately 20 times as large as that of the plasma without the stochastic magnetic field produced by co-directed ECCD (co-ECCD) at the maximum. Furthermore, in the stochastic magnetic field with ctr-ECCD, counter-directed intrinsic rotation is observed in the plasma with balanced NBI discharge.

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“…In helical plasma, non-local phenomena have been observed in the low density regime below 1 � 10 19 m À 3 in LHD [124,125]. Flow reversals from the co-rotation to counter-rotation is also observed when the electron density exceeds 1 � 10 19 m À 3 in the discharge with no external torque input [126]. The experiment in C-mod shows that the critical density for the appearance of non-local phenomena is the same as the critical density for flow reversal [118,127].…”

Section: Momentum Transport (Toroidal Flow Reversal)mentioning

confidence: 99%

Bifurcation phenomena in magnetically confined toroidal plasmas

Ida

2020

Advances in Physics: X

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Bifurcation phenomena observed in turbulence and transport, in topology of magnetic field and MHD, and the interplay between turbulence and MHD bifurcation in magnetically confined toroidal plasmas are reviewed. Two types of bifurcation phenomena in turbulent transport are discussed. One is significant change in the magnitude of the diffusion term and the other is a sign flip of non-diffusive term of transport. The bifurcation of diffusion term magnitude causes the transition to a so-called improved mode such as ion-electron root transition, L-mode to H-mode transition, and ITB formation. In contrast, the bifurcation of non-diffusion term sign causes the intrinsic flow reversal, convection reversal of bulk ion, and impurity ions. Two types of bifurcation phenomena in MHD are discussed. One is the bifurcation of static magnetic topology and the other is the bifurcation of MHD instability. The bifurcation of static magnetic topology is observed in between three magnetic topology (nested magnetic flux surface, magnetic island and stochastic magnetic field) in toroidal plasma. The bifurcation of MHD instability is observed as a parity change of MHD oscillation. The bifurcation of the magnetic island states caused by the interplay between turbulence and MHD is also discussed.

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3-D effects on viscosity and generation of toroidal and poloidal flows in LHD

Cited by 10 publications

References 30 publications

Asymmetry of parallel flow on the Large Helical Device

Asymmetry of parallel flow on the Large Helical Device

Effects of core stochastization on particle and momentum transport

Bifurcation phenomena in magnetically confined toroidal plasmas

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