Observation of Toroidal Flow on LHD

Yoshinuma, M.; Ida, K.; Yokoyama, M.; Nagaoka, K.; Osakabe, M.

doi:10.1585/pfr.3.s1014

Cited by 12 publications

(13 citation statements)

References 14 publications

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“…These observations indicate a strong correlation between ion diffusivity and parallel viscosity. It is noted that large toroidal flows associated with high T i are also observed in tokamak devices [19]; thus, the comparison of large flow production in high-T i plasmas between helical and tokamak devices is an interesting subject [12]. The poloidal rotation in the core region cannot be observed when the T i becomes high, because the carbon impurity has a strongly hollow profile associated with the T i rise.…”

Section: Resultsmentioning

confidence: 99%

“…The other is a poloidal system having poloidal lines of sight, which can measure the profiles of T i and poloidal rotation of the plasma. Half of the P-NB (BL4-A or BL4-B) is modulated (ON for 100 msec and OFF for 100 msec) for CXS measurement to acquire the background signal [12].…”

Section: Experimental Conditionsmentioning

confidence: 99%

“…P-NB can be utilized for profile measurement of T i by charge exchange spectroscopy (CXS); thus, ion heat transport can be estimated experimentally [12]. Moreover, P-NB has a high particle fueling rate due to a large beam current of 150 A, and it is also utilized for particle fueling and controlling the density profile.…”

Section: Introductionmentioning

confidence: 99%

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Ion Heating Experiments Using Perpendicular Neutral Beam Injection in the Large Helical Device

Nagaoka

Yokoyama

Takeiri

et al. 2008

Plasma and Fusion Research

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A perpendicular neutral beam (P-NB) injector was installed in the Large Helical Device (LHD) and utilized for high-power ion heating and measurement of the ion temperature (T i ) profile by charge exchange spectroscopy. Significant progress was achieved in ion heating experiments using P-NB, and a high T i of 5.2 keV was achieved at the plasma center. A T i peak profile with a steep gradient in the core region was observed, indicating an improved mode of ion transport. The enhancement of toroidal flow in the core region was observed with the T i rise. Transport analysis shows improvement in anomalous transport in the core region, and the neoclassical transport remains unchanged when the high T i is realized.

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Section: Resultsmentioning

confidence: 99%

Section: Experimental Conditionsmentioning

confidence: 99%

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Ion Heating Experiments Using Perpendicular Neutral Beam Injection in the Large Helical Device

Nagaoka

Yokoyama

Takeiri

et al. 2008

Plasma and Fusion Research

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“…The mechanism for driving the spontaneous toroidal flow is of great interest in the area of momentum transport physics and has been investigated experimentally and theoretically. [22][23][24][25][26][27] Besides the toroidal flow driven by the external momentum input of the tangential NBI, there is the spontaneous toroidal flow driven by the coupling of the E ϫ B force and the viscosity tensor. The stress tensor redirects some fraction of the diamagnetic and E ϫ B flows into parallel flows.…”

Section: Spontaneous Rotationmentioning

confidence: 99%

Extension of the high-ion-temperature regime in the Large Helical Device

Yokoyama¹,

Nagaoka²,

Yoshinuma³

et al. 2008

Physics of Plasmas

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High-ion-temperature ͑exceeding 5 keV͒ hydrogen plasmas have been successfully produced in the Large Helical Device ͓Iiyoshi et al., Nucl. Fusion 39, 1245 ͑1999͒; Motojima et al., Nucl. Fusion 47, S668 ͑2007͔͒ with the ion heat confinement improvement in the core region. The experimental ion heat diffusivity at the core region is found to be almost independent of the ion temperature, T i ͑even decreasing as T i increases͒. The neoclassical ͑NC͒ ripple transport is suppressed by the ambipolar radial electric field, E r ͑Ͻ0͒ predicted by NC transport fluxes. The temperature ratio, T i / T e , is one of the key parameters to reduce the NC ambipolar particle and heat fluxes. Thus, it is suggested that the selective ion heating ͑making T i / T e larger͒ is a plausible approach to further increase T i . Spontaneous rotation is evaluated in these high-T i plasmas, in which a co-directed component is recognized at the radial location with a large T i gradient, in addition to the tokamak-like counter-directed component expected for E r Ͻ 0.

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“…For efficient ion heating in hydrogen plasmas, the positive-NBI has been recently constructed with an injection energy of 40 keV, which dominantly heats plasma ions, and 6 MW of injection power was achieved [10]. The positive-NBI is also utilized for a T i -profile measurement by charge-exchange spectroscopy (CXS) along a toroidal line of sight [13,14], which is better for the measurement in the central region than that along a poloidal line of sight. With this arrangement, toroidal rotation is also measured.…”

Section: Nbi and Ecrh Systemsmentioning

confidence: 99%

Improvement of Ion Confinement in Core Electron-Root Confinement (CERC) Plasmas in Large Helical Device

Takeiri

Yokoyama

Nagaoka

et al. 2008

Plasma and Fusion Research

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An increase in ion temperature has been observed with superposition of centrally focused electron cyclotron resonance heating (ECRH) to plasmas heated by high-energy neutral beam injection (NBI) in Large Helical Device. The ion-temperature (T i ) rise is accompanied by the formation of electron internal transport barrier (ITB). A transport analysis shows that ion transport as well as electron transport is improved with the reduction of anomalous transport. A neoclassical ambipolar flux calculation shows a positive radial-electric field (E r ) in the region of the T i rise, and E r should suppress the enhancement of ripple transport due to the T i -rise. These analyses indicate the ion transport improvement in the core electron-root confinement plasmas. Toroidal rotation is driven in the co-direction by applying ECRH, and the toroidal rotation velocity is increased with the T i rise. A correlation between the T i rise and toroidal rotation is suggested.

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Observation of Toroidal Flow on LHD

Cited by 12 publications

References 14 publications

Ion Heating Experiments Using Perpendicular Neutral Beam Injection in the Large Helical Device

Ion Heating Experiments Using Perpendicular Neutral Beam Injection in the Large Helical Device

Extension of the high-ion-temperature regime in the Large Helical Device

Improvement of Ion Confinement in Core Electron-Root Confinement (CERC) Plasmas in Large Helical Device

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