[en] Radial structures of plasma rotation and radial electric field are experimentally studied in tokamak, heliotron/torsatron and stellarator devices. The perpendicular and parallel viscosities are measured. The parallel viscosity, which is dominant in determining the toroidal velocity in heliotron/torsatron and stellarator devices, is found to be neoclassical. On the other hand, the perpendicular viscosity, which is dominant in dictating the toroidal rotation in tokamaks, is anomalous. Even without external momentum input, both a plasma rotation and a radial electric field exist in tokamaks and heliotrons/torsatrons. The observed profiles of the radial electric field do not agree with the theoretical prediction based on neoclassical transport. This is mainly due to the existence of anomalous perpendicular viscosity. The shear of the radial electric field improves particle and heat transport both in bulk and edge plasma regimes of tokamaks. (author) 95 refs

[en] This paper describes a method for determining the shape of the plasma cross section shot-by-shot with a mini-computer. The magnetic surface is calculated from the magnetic field and flux, which are measured with 12 pairs of magnetic probes and 9 one-turn loops located in the shadow of the limiter. This method is so simple that the execution time is very short and even a mini-computer (LSI-11) can be used to perform the calculation in less than one minute. The control of plasma shape shot-by-shot is thus made possible by this m ethod. (author)

[en] Production mechanism of spontaneous plasma flow and flow velocity shear in the toroidal plasma is described. The plasma flow parallel to the magnetic field is produced by the radial electric field through the viscosities in the plasma. The observation of plasma flow driven by the thermodynamic force such as pressure gradient are presented. The effect of flow velocity shear on the transport, which determines the pressure profiles, is also discussed. (author)

[en] Experiments on the transport barrier in Helical plasmas are reviewed. There are two mechanisms of transport improvement, that results in the formation of the transport barrier. One is the improvement of neoclassical transport by reducing the ripple loss with radial electric field, which exist only in helical plasma. The other is the improvement of anomalous transport due to the suppression of fluctuations associated with a radial electric field shear both in tokamak and helical plasma. The formation of the transport barrier can be triggered by the radial electric field shear associated with the transition of the radial electric field (L/H transition or ion-electron root transition) or the peaked density or the optimization of magnetic field shear. The mechanisms of transport barrier formation are also discussed. (author). 60 refs

[en] The physical mechanisms determining the diffusive and non-diffusive terms of particle, momentum and heat transports are described. The non-diffusive term in particle transport, which causes inward pinch or outward flux, is driven by the temperature gradient and the magnetic field curvature. The non-diffusive term in the momentum transport, which drives spontaneous toroidal rotation, is found to depend on the electric field and ion temperature gradient in the plasma. In heat transport, no clear non-diffusive term is observed. The temperature and temperature gradient dependences of the diffusive terms are discussed. (author)

[en] Recently the measurements of poloidal magnetic field become important in plasma physics and nuclear fusion research, since an improved confinement mode associating with a negative magnetic shear has been found. The polarization plasma spectroscopy is recognized to be a useful tool to measure poloidal magnetic field and pitch angle of magnetic field. (author)

[en] The structure of the radial electric field and toroidal/poloidal flow is discussed for the high temperature plasma in toroidal systems, tokamak and Heliotron type magnetic configurations. The spontaneous toroidal and poloidal flows are observed in the plasma with improved confinement. The radial electric field is mainly determined by the poloidal flow, because the contribution of toroidal flow to the radial electric field is small. The jump of radial electric field and poloidal flow are commonly observed near the plasma edge in the so-called high confinement mode (H-mode) plasmas in tokamaks and electron root plasma in stellarators including Heliotrons. In general the toroidal flow is driven by the momentum input from neutral beam injected toroidally. There is toroidal flow not driven by neutral beam in the plasma and it will be more significant in the plasma with large electric field. The direction of these spontaneous toroidal flows depends on the symmetry of magnetic field. The spontaneous toroidal flow driven by the ion temperature gradient is in the direction to increase the negative radial electric field in tokamak. The direction of spontaneous toroidal flow in Heliotron plasmas is opposite to that in tokamak plasma because of the helicity of symmetry of the magnetic field configuration. (author)

[en] The Large Helical Device (LHD) at the National Institute for Fusion Science (NIFS) is the world’s largest superconducting helical fusion device, providing a scientific research center to elucidate important physics research such as plasma transport, turbulence dynamics, and other topics. Furthermore, many types of advanced diagnostic devices are used to measure the confinement plasma characteristics, and these valuable physical data are registered over the 131,000 discharges in the LHD database. However, it is difficult to investigate the experimental data even though much physical data has been registered. In order to improve the efficiency for investigating plasma physics in LHD, we have developed a new data visualization software, MyView2, which consists of Python-based modules that can be easily set up and updated. MyView2 provides immediate access to experimental results, cross-shot analysis, and a collaboration point for scientific research. In particular, the MyView2 software is a portable structure for making viewable LHD experimental data in on- and off-site web servers, which is a capability not previously available in any general use tool. We will also discuss the benefits of using the MyView2 software for in-depth analysis of LHD experimental data.

[en] Control of the radial electric field is considered to be important in helical plasmas, because the radial electric field and its shear are expected to reduce neoclassical and anomalous transport, respectively. Particle and heat transport, that determines the radial structure of density and electron profiles, sensitive to the structure of radial electric field. On the other hand, the radial electric field itself is determined by the plasma parameters. In general, the sign of the radial electric field is determined by the plasma collisionality, while the magnitude of the radial electric field is determined by the temperature and/or density gradients. Therefore the structure of radial electric field and temperature and density are strongly coupled through the particle and heat transport and formation mechanism of radial electric field. Interactions between radial electric field, transport and structure in helical plasmas is discussed based on the experiments on Large Helical Device

[en] The effect of the spectral fine structure of H-like ions on the plasma rotation measurements was investigated using the 'bi-directional' viewing of the charge exchange excited CVI lines. The wavelength given by a single Gaussian fitting shows the apparent wavelength shifts of Δλ ∼0.01A depending the ion temperatures in the range of ∼100 eV. (author)