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Shiraishi, Junya; Tokuda, Shinji; Aiba, Nobuyuki
no journal, ,
no abstracts in English
Hirota, Makoto; Tokuda, Shinji
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Adiabatic invariance of wave action is investigated for generaleigenmodes and continuum modes by exploiting the variational principlefor linearized dynamical systems. Given a sufficiently slow evolution of the background fields, thewave action (or the action variable) attributed to each mode isconserved as long as the corresponding discrete or continuous spectrumis isolated from other spectra and zero frequency. The resonantcoupling allows exchange of wave action among these modes.
Aiba, Nobuyuki; Furukawa, Masaru*; Hirota, Makoto; Tokuda, Shinji
no journal, ,
In this paper, we investigate numerically the destabilizing effect of a toroidal rotation on the edge localized MHD mode, which induces the large amplitude edge localized mode (ELM). As the results of this analysis, we reveal that the toroidal rotation with shear can destabilize this MHD mode, and the destabilization is caused by the difference between the plasma rotation frequency and the frequency of the unstable mode, which mainly affects the pressure-driven component of the unstable mode. This destabilizing effect becomes more effective as the wave length of the mode becomes shorter, but such a MHD mode with short wave length is also stabilized by the sheared toroidal rotation due to the Doppler-shift at each flux surfaces. We clarify that the stability of the edge localized MHD mode, whose wave length is typically intermediate, is determined by the balance between these stabilizing and destabilizing effects.
Matsunaga, Go; Takechi, Manabu; Sakurai, Shinji; Ide, Shunsuke; Matsukawa, Makoto; Oyama, Naoyuki; Aiba, Nobuyuki; Kurita, Genichi; Ferro, A.*; Gaio, E.*; et al.
no journal, ,
Yoshida, Maiko; Kamada, Yutaka; Takenaga, Hidenobu; Sakamoto, Yoshiteru; Oyama, Naoyuki; Urano, Hajime
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Parameter dependences of these ratios are essential to understand the mechanisms determining the rotation profile and the level of momentum transport. In this paper, dimensional and non-dimensional parameter dependences of the momentum transport coefficients and these ratios are investigated. It is found that the ratio of the toroidal momentum diffusivity to the thermal diffusivity increases with increasing the normalized poloidal Larmor radius. The ratio of the inward convection velocity to the toroidal momentum diffusivity decreases with increasing the normalized collisionality and decreasing the normalized poloidal Larmor radius. Relations between core and edge rotations are found and the physics mechanisms are discussed form the viewpoints of pinch effect and intrinsic rotation.
Suzuki, Takahiro; Oyama, Naoyuki; Asakura, Nobuyuki
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Propagation of plasma ejected by type-I ELM has been measured in scrape-off layer (SOL), using optical system of motional Stark effect (MSE) diagnostics in JT-60U as beam emission spectroscopy (BES) diagnostics. This MSE/BES system measures Dalpha emission from heating neutral beam excited by collisions with the ejected plasma, as well as background light (e.g. bremsstrahlung). In order to separate the beam emission and the background light, a two-wavelength detector is introduced into the MSE/BES system. The detector observes simultaneously at the same spatial point in two distinct wavelengths using two photomultiplier tubes through two interference filters. One of the filters is adjusted to the central wavelength of the beam emission and the other is outside the beam emission spectrum. Subtracting the background light, temporal change in the net beam emission in SOL has been evaluated. Comparing conditionally-averaged beam emission with respect to 594 ELMs at 5 spatial channels (0.02-0.3 m outside the main plasma near equatorial plane), radial velocity of the ELM pulse propagation in SOL is about 0.8-1.8 km/s.
Hayashi, Nobuhiko; JT-60 Team
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Kikuchi, Mitsuru
no journal, ,
This talk summarizes the achievement of steady state research during 23 years of JT-60 tokamak experiment. Before the modification to JT-60U, up to 0.8 of plasma current was driven by the bootstrap current and the steady state tokamak reactor concept SSTR was proposed in 1990. For this assessment, theory of generalized Ohm's law in tokamak was developed. Negative shear configuration was first proposed in 1992 and becomes popular in advanced tokamak research up to now. Formation of internal transport barrier (ITB) in PS (1994) and NS (1997) leads to enhanced bootstrap current fraction in the core region. Non-inductive current drive physics of NBCD and ECCD was well developed using N-NBI and ECCD systems in JT-60U. A current hole (CH) was observed as unique structure formation in tokamak (2001). Stabilization of RWM in DIII-D and JT-60U with small toroidal rotation is important for reactor application to sustain high plasma pressure above no-wall limit (2007).
McMillan, B. F.*; Jolliet, S.; Tran, T. M.*; Bottino, A.*; Lapillonne, X.*; Villard, L.*
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