Experimental determination of non-diffusive toroidal momentum flux in JT-60U

Nagashima, Keisuke; Koide, Y.; Shirai, Hiroshi

doi:10.1088/0029-5515/34/3/i12

Cited by 76 publications

(81 citation statements)

References 8 publications

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“…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]. The use of magnetic perturbations to brake the plasma was reported in DIII-D [25] and NSTX [24,26,27] as another means to induce a transient from which it is possible to infer diffusivity and convection separately.…”

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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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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“…Therefore, spontaneous toroidal flow becomes important in the next fusion devices such as ITER, where the toroidal flow velocity driven by external momentum is expected to be insufficient to stabilize the MHD mode. The mechanism of driving the spontaneous toroidal flow is interesting from the viewpoint of momentum transport physics and has been investigated in tokamaks, both experimentally and theoretically [2][3][4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Observation of Toroidal Flow on LHD

Yoshinuma

Ida

Yokoyama

et al. 2008

Plasma and Fusion Research

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In order to investigate the formation of toroidal flow in helical systems, both NBI driven flow and spontaneous toroidal flow were observed in Large Helical Device (LHD). The toroidal flow driven by NBI is dominant in plasma core while its contribution is small near plasma edge. The spontaneous toroidal flow changes its direction from co to counter when the radial electric field is changed from negative to positive at plasma edge. The direction of the spontaneous toroidal flow due to the radial electric field near plasma edge is observed to be opposite to that in plasma core where the helical ripple is small.

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“…The toroidal flow has been considered to be determined by the radial transport of momentum driven by neutral beam injection (NBI) with anomalous shear viscosity [8,9]. Although the E 3 B velocity shear due to the toroidal flow can be important in the plasma core [10], there have been few experiments that demonstrate a spontaneous toroidal flow not driven by NBI in tokamaks [11][12][13][14]. It is generally the case in tokamaks that the plasma rotates parallel (antiparallel) to the plasma current for the coinjected (counterinjected) NBI, which corresponds to a positive (negative) radial electric field ͑E r ͒ in L-mode plasmas [15].…”

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Observation of Toroidal Flow Antiparallel to the〈Er×Bθ〉Drift Direction in the Hot Electron Mode Plasmas in the Compact

et al. 2001

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A toroidal flow antiparallel to the ͗E r 3 B u ͘ drift direction is observed in the hot electron mode plasmas when a large positive electric field and a sharp electron temperature gradient are sustained inside the internal transport barrier in the Compact Helical System. This toroidal flow reaches up to 5 3 10 4 m͞s at the plasma center, and it is large enough to reverse the toroidal flow driven by a tangentially injected neutral beam. These observations clearly show the plasma favors flow in the minimum =B direction at the transport barrier. DOI: 10.1103/PhysRevLett.86.3040 PACS numbers: 52.55.HcA spontaneous poloidal flow has been recognized to be important in the confinement of toroidal plasmas, since poloidal flow velocity and radial electric field shear were found to contribute an improvement of plasma confinement in H-mode plasmas [1,2]. The turbulence in the plasma is predicted to be suppressed by a E 3 B velocity shear through the mechanism of a nonlinear decorrelation [3,4]. It has been confirmed experimentally that the E 3 B shearing rate exceeds the growth rate of the turbulence at the transport barrier [5][6][7]. The toroidal flow has been considered to be determined by the radial transport of momentum driven by neutral beam injection (NBI) with anomalous shear viscosity [8,9]. Although the E 3 B velocity shear due to the toroidal flow can be important in the plasma core [10], there have been few experiments that demonstrate a spontaneous toroidal flow not driven by NBI in tokamaks [11][12][13][14]. It is generally the case in tokamaks that the plasma rotates parallel (antiparallel) to the plasma current for the coinjected (counterinjected) NBI, which corresponds to a positive (negative) radial electric field ͑E r ͒ in L-mode plasmas [15]. However, when a negative E r is produced at the transport barrier, both localized toroidal flow in the counterdirection and localized poloidal flow in the electron diamagnetic direction are observed even for plasmas with coinjected NBI [5,16,17]. These results show the need for detailed measurements of both toroidal and poloidal flow at the transport barrier, where the toroidal flow profile is not determined by the transport of momentum driven by NBI alone. Yet, despite the importance of the coupling between toroidal and poloidal flow, no studies until now have discussed the toroidal flow at the internal transport, where there is a large radial electric field.In a Heliotron/Torsatron device, there is no toroidal symmetry, and the minimum =B trace has a helical structure and helical flow along the minimum =B can be expected. The significant difference between tokamaks and Heliotron devices is the relationship between the poloidal field direction and the direction of dominant symmetry.The pitch angle of dominant symmetry is even larger than that of the averaged poloidal field in a Heliotron device, while it is zero due to the toroidal symmetry in tokamaks. This helical flow should change sign depending on the sign of E r or on the direction of the magnetic field. H...

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Experimental determination of non-diffusive toroidal momentum flux in JT-60U

Cited by 76 publications

References 8 publications

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

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

Observation of Toroidal Flow on LHD

Observation of Toroidal Flow Antiparallel to the〈Er×Bθ〉Drift Direction in the Hot Electron Mode Plasmas in the Compact

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