Local impurity deposition in the n/m = 1/1 magnetic island, which is expanded by the external perturbation coils, has been obtained by means of the tracer-encapsulated solid pellet in the Large Helical Device. The differences of the local deposition of the tracer between inside the magnetic island and outside that were clearly observed by both the absolute extreme ultra violet silicon photodiode arrays and the ECE radiometer.

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A three-dimensional dynamic simulation code, which calculates the local transport and redeposition of impurities on a divertor plate and the depth profile of deposited impurities in the plate, is developed. The code simulates the erosion and redeposition patterns of a graphite plate which was used in the third experimental campaign of the large herical device (LHD). The depth profile indicates a prompt, asymmetric redeposition of sputtered Fe atoms.

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Applications of neural networks to data analysis and control of fusion plasmas are reviewed. First, a brief introduction to the general features of a neural network is presented, where the neural network is considered as a continuous mapping device, a classification device, a statistical processing device, and a time series predicition device. Then, the applications of neural networks to the research field are explained where the problems to be solved are classified a sfitting function, shaping an experimentally obtained spectrum, analyzing equilibrium quantity, prediction, tomography, and control problems. Throughout the article, we restrict ourselves to description of applications of multi-layer neural networks.

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Nonlocal transport becomes important in a variety of situations in physics. We briefly review under what conditions it appears to be important in modeling energy transport by neutral gas, neutrons, charged particles, photons, and neutrinos. In the cases of these last three, the cross-sections strongly depend upon particle energies. In such cases, nonlocal transport becomes important even when each mean free path is much shorter than the length of the change of its energy density. We mainly review the research that has been done on nonlocal electron energy transport in relation to laser-produced plasmas and the way in which precise calculation of neutrino transport changes the properties of a shock wave, which is used as a driver to explode a massive star such as a supernova, by solving Boltzmann-type equations for neutrinos and anti-neutrinos.

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Nonlocal transports of energy and angular momentum in a strophysical rotating plasmas are studied by global three-dimensional magnetohydrodynamic simulations. When the plasma torus rotating around a gravitating object is threaded by large-scale vertical magnetic fields, a bipolar jet emanates from the surface of the torus. Angular momentum extraction by these jets enhances the accretion of the torus material. Magnetic turbulence generated by the magneto-rotational instability also efficiently transports angular momentum outward. Direct numerical simulations enable us to study the evolution of the cosmic plasma torus with out assuming phenomenological viscosity.

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Transport along field lines in magnetic confinement plasmas is reviewed. Collisionless and collisional-diffusive transports are discussed. As a result of rapid transport, features of plasmas along field lines are apt to behave nonlocally. A nonlocal phenomenon of scrape-off layer (SOL) and divertor plasmas in a tokamak is introduced, whose asymmetry along field lines is induced by thermoelectric instability related to the SOL current. A local phenomenon called MARFE can be brought by the strong radiation cooling. The ”snake”, a nonlocal feature along field lines but with local structure perpendicular to the field, is observed in a tokamakcoreplasma. For mirror-confined plasmas, axial particle losses from the mirror ends, especially pitch-angle-scattering losses into the loss cone and nonadiabatic losses due to the breakdown of adiabaticity of the magnetic moment, are discussed in relation to nonlocal axial transport.

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Neoclassical transport is studied including the effect of finite orbit widths for tokamak plasmas subject to regular flux surfaces. Nonlocal transport for the plasma near the magnetic axis is considered by the Lagrangian method. All types of particle orbits, that are complicated and different from those of usual banana and passing particles, are taken into account. Neoclassical radial electric fields are calculated by a δf MonteCarlo particle simulation. Only when the effect of finite orbit widths is rigorously taken into account, the determination of the radial electric field is possible. The diffusion process in perturbed electromagnetic field is revisited, in order to consider the effects of non-local particle orbits on the transport.

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Experimental evidence and underlying physical processes of nonlocal characters and structural formation in magnetically confined toroidal plasmas are reviewed. Radial profiles of the plasmas exhibit characteristic structures, depending on the various confinement regimes. Profile stiffness subjected to some global constraint and rapid plasma responses to applied plasma perturbation result from nonlocal transport. Once the plasma is free from the constraint, the plasma state can be changed to a new state exhibiting various types of prominent structural formation such as an internal transport barrier.

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Nonlocal properties of fluctuations in confined plasmas are briefly surveyed. Contributions to understanding the bifurcation phenomena, improved confinement, and transient transport problem are explained. The theoretical progress in this aspect is addressed: Namely, the fluctuations are not excited by linear instabilities but are dressed with other turbulent fluctuations or fluctuations of meso-scale. Nonlinear interactions of fluctuations with different scale lengths are essential indictating the dynamics of turbulence and turbulent transport. There are activators and suppressers in global inhomogeneities for evolution of turbulence. Turbulent fluctuations, on the other hand, induce or destroy these global inhomogeneities. Finally, statistical nature of turbulence is addressed.

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An introductory review is given on recent developments in the methods for stability analysis of a toroidally confined plasma. Emphasis is put on the perturbation analysis of a magnetohydrodynamic system that has the marginally stable state as a terminal point of continuous spectra. We address ourselves to the asymptotic matching method pertinent to such a problem. The Newcomb equation and inner layer equations are essential ingredients in the methods and the numerical methods for solving them are discussed.

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The resistive boundary layer theory based on a non-constant-φ asymptotic matching method is reviewed. This theory describes resistive-kink modes, double-tearing modes and forced reconnection. An intrinsic difficulty in this theory is presented. The difficulty is the appearance of an unstable solution for the equilibrium which is stable against tearing modes, i.e.Δ’<0. The origin of the difficulty is clarified. It is an open problem to formulate a boundary layer theory which intrinsically excludes this unstable solution.

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A complete spectral analysis of a non-Hermitian generator has been shown for a surface-wave model describing the Kelvin-Helmholtz instability. The canonical form of the generator contains a Jordan block in the con- tinuous spectrum, which represents resonant interaction of a surface wave and ambient shear flow due to the overlapping of their frequencies. Secular amplification (or a long-term modulation) of oscillations is induced by the resonant (or near resonant) interactions.

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In the medium size tokamak JFT-2M, ferritic steel plates (FPs) were inserted in order to reduce the toroidal field ripple, which caused fast ion losses. A 2D infrared TV (IRTV) system with time and spatial resolutions appropriate for measuring the first wall temperature increment caused by the ripple ion losses was developed. An IR thermal-imaging camera was used in the present study; this device provided a field rate of 60 fields/sec and a detectable temperature range of 0-500ºC with a resolution of 0.2ºC. The PtSi detector, sensitive to 3˜5 µm IR radiation, was arrayed in 256 × 256 pixels. The optical system consisted of an IR-lens, a turning mirror, and a sapphire vacuum window with a distance from the camera position to the target wall of 3.5 m, resulting in spatial resolution of ˜3 mm. The target wall consisted of ˜9 cm × ˜15 cm carbon tiles. By using this system, local hot spots due to the ripple-trapped and banana drift losses were observed when fast ions were produced by tangential NBI (36 kV, ˜0.5 MW). The peak temperature increment reached ˜75ºC and ˜150ºC on the ripple-trapped and banana drift loss regions, respectively. In the optimized condition with FP insertion, the temperature increment was reduced to an almost negligible level for the ripple-trapped loss regions. The corresponding increment for the banana drift loss regions was also minimized. These IRTV data clearly demonstrate the efficacy of FPs for the reduction of fast ion losses.

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The formation properties of an internal transport barrier (ITB) were investigated in a weak positive magnetic shear plasma by changing the neutral beam heating power. The ion thermal diffusivity in the core region shows L-mode state, weak ITB, and strong ITB, depending upon the heating power. Two features of ITB formation were experimentally confirmed. Weak ITB was formed in spite of the absence of an apparent transition in an ion temperature profile. On the other hand, strong ITB appeared after an apparent transition from the weak ITB. In addition, the ion thermal diffusivity at the ITB is correlated to the radial electric field shear. In the case of the weak ITB, ion thermal diffusivity decreased gradually with increases in the radial electric field shear. There exists a threshold in the radial electric field shear, which allows for a change in state from that of weak to strong ITBs.

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With the main aim of providing physics basis for ITER and the steady-state tokamak reactor, JT-60U has been optimizing the operational concepts and extending discharge regimes toward the sustainment of high integrated performance. In the two advanced operation regimes, the reversed magnetic shear (RS) and the weak magnetic shear (high-β_p) ELMy H modes characterized by both internal (ITB) and edge (ETB) transport barriers, JT-60U has clarified responses of the transport barrier structure to magnetic shear, heating power, momentum, density, etc. Based on these observations, possible parameter linkages and feedback loops in the core and pedestal regimes have been proposed. With the optimization of profile and shape control, both confinement and high β stability have been enhanced and favorable integrated performance has been achieved. Such operational regimes have been extended to the reactor-relevant regime.

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