Computer animations resulted from two-dimensional magnetohydrodynamic simulations of plasma merging have reproduced dynamic behaviors found in laboratory experiments. Specifically, the following features have been clearly shown, that is, 1) formation process of pressure profile by an induced plasma flow during counter-helicity merging of spheromaks, 2) topology change of field lines and their toroidal motion, and 3) magnetic island formation in a diffusion region during co-helicity injection.

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In recent years, a compact torus (CT) injection method has been considered as one of advanced fueling methods for a fusion device and has been discussed in several experimental and theoretical studies. However, the dynamics of a injected CT has not been well understood. Our main objective is to understand the CT dynamics as well as the fueling process by using three-dimensional magnetohydrodynamic (MHD) numerical simulations where the CT is injected into a model fusion device. From the simulation result, it is revealed that the high density plasma which is initially confined in the CT magnetic field is supplied into the device region, as a result of magnetic reconnection between the CT magnetic field and the device magnetic field.

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Disruption and vertical instability are simulated by use of the multi-layers method. The tokamak system is not closed in the energy since it has an energy source to contorol the coil current. Then plasma equilibrium is found by minimizing the energy functional, which is free energy including the energy flow from the power supply. Time evolution of the system is presumed the continuous equilibrium. Because this model, which includes no cold plasma surrounding the main plasma, can take longer computational time step than MHD model, it enables us to design a PF coil system incorporating the transient phenomenon of plasma such as disruption, and to study the efficient operation and the reliable control methods of next-generation tokamak-type reactors.

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Since plasma ellipticity and triangularity seem to partially determine the energy confinement performance of a plasma, the importance of plasma shape have been recognized in recent years. On the other hand, reproduction of the plasma full shape in real-time has been considered impossible due to the limitation of present computational capability. To solve this problem, computation of special functions and matrix inversion, that are obstacles for speed improvement in the calculation, should be removed from the real-time procedures. A method using particular coefficient vectors in tabular form has been developed and the table is stored in a large scale memory of the fast computer, where the vectors are corresponding to the in-vessel flux calculation points on the poloidal cross-section. This improvement in software was taken together with the new installation of advanced electronics devices. As a result, we succeeded to reduce the computaion time extremely, and the full JT-60 plasma shape is reproduced every 60 ms in real-time. This system visualizes the time evolution of plasma shapes clearly and in detail, from the beginning to the end of a discharge pulse. This report describes the development of the system in both hardware and software, and also gives the prospect of this system in application to plasma real-time feedback control.

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Nonlinear evolution of single spike structure and vortex in the Richtmyer-Meshkov instability is investigated for two dimensional case, and axial symmetric and non axial symmetric cases with the use of a three-dimensional hydrodynamic code. It is shown that singularity appears in the vorticity left by transmitted and reflected shocks at a corrugated interface. This singularity results in opposite sign of vorticity along the interface that causes double spiral structure of the spike. Difference of nonlinear growth rate and double spiral structure among three cases is also discussed by visualization of simulation data. In a case that there is no slip-off of initial spike axis, vorticity ring is relatively stable, but phase rotation occurs.

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Turbulent structure of Rayleigh-Taylor unstable interface is investigated with the use of two dimensional hydrodynamic code. It is shown that mode coupling and vortex generation results in a fractal structure of the interface. Transition to fractal interface is discussed with visualization of simulation results.

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Anomalous propagation of a linearly-polarized ultra intense laser in an overdense plasma is studied with the use of three-dimensional PIC code. It is shown that a linearly-polarized laser light breaks into anisotropic filaments with a size of collisionless relativistic skin depth perpendicular to the polarization direction. Strong modulational instability is also shown. The dependence of the filamentation and modulational instabilities on laser intensity and plasma density is discussed.

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In order to analyze structure and dynamic behavior of dust particles trapped in plasma-dc sheath boundary, we have developed object oriented 3-dimensional simulation code linked to movie system powered by JAVA. This report provides an overview of the developed simulation code, which will be opened as a public domain code. By using code, we have reproduced a Coulomb dust cloud observed experimentally with a funnel shape composed of multiple layers and simulate longitudinal waves' propagation to get their dispersion relation.

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