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Investigates the formation of a magnetic field found in the Magnetic Reconnection Experiment (MRX) by a magnetohydrodynamic relaxation theory and a numerical simulation. Growing process of the island into a spheromak-type configuration; Types of injection mode of a toroidal field in the MRX.

Discusses the role of singular currents in three-dimensional toroidal equilibria and their resolution by magnetic island formation. Importance of current sheets recognized in analytical theories; Comparison of the predictions of the theory with the numerical results from the HINT code.

Examines the behavior of magnetic islands and their effect on plasma confinement. Simulations of three-dimensional equilibria in the H-1 Heliac; Evolution of a rotational transform to exclude the rational surface concerned; Evidence of near-resonant flux surface deformations.

Analyzes the behavior of finite-pressure-induced magnetic islands for three-dimensional magnetohydrostatic equilibria of the Helias configuration. Use of a three-dimensional equilibrium code; Remarkable property of magnetic islands induced by the finite pressure effect; Numerical scheme of HINT.

Microfission chambers, which are pencil sized ionization chamber containing fissile material inside, will be installed in the vacuum vessel as neutron monitors for International Thermonuclear Experimental Reactor (ITER). We have performed first measurements of the detector installed between the vacuum vessel and toroidal coils on JT-60U. The technical validity as a neutron monitor, such as magnetic field effect and electromagnetic noises from the plasma and heating devices, has been investigated. The detector had an excellent linearity with a 235U fission chamber as a neutron monitor on JT-60U with the standard deviation of 3% except for some noise signals. The electromagnetic noises were caused by neutral beam injection (NBI) breakdowns, probably due to long wiring between the detector and the preamplifier. In case of plasma disruption, improper signals have not been observed. The magnetic field effect also has not been observed up to 2 T. In JT-60U, we confirmed availability of the micro fission chamber as a neutron monitor over three decades of neutron source strength up to 1.3×1016 neutrons/s with 1 ms temporal resolution. The biggest weakness in the detector was its noise sensitivity to NBI breakdowns. Therefore, by suppressing the electromagnetic noise, microfission chambers can be available as neutron monitors for ITER. [ABSTRACT FROM AUTHOR]

Nonlinear simulations based on the magnetohydrodynamic model have been executed to reveal the dynamics of the ballooning mode in the spherical tokamak plasma. The simulation results have reproduced the characteristic features of the edge-localized mode crash phase, where the filamentary structures are formed along the magnetic field in the edge region, and separated from the core plasma. Moreover, the finite Larmor radius effect is addressed. [ABSTRACT FROM AUTHOR]

A central theme of ``Complexity?? is the question of the creation of ordered structure in nature (self-organization). The assertion is made that self-organization is governed by three key processes, i.e., energy pumping, entropy expulsion and nonlinearity. Extensive efforts have been done to confirm this assertion through computer simulations of plasmas. A system exhibits markedly different features in self-organization, depending on whether the energy pumping is instantaneous or continuous, or whether the produced entropy is expulsed or reserved. The nonlinearity acts to bring a nonequilibrium state into a bifurcation, thus resulting in a new structure along with an anomalous entropy production. As a practical application of our grand view of self-organization a preferential generation of a dipole magnetic field is successfully demonstrated. [ABSTRACT FROM AUTHOR]