Kakuyūgō kenkyū

A possibility to construct a toroidal fusion reactor without the concentration of heavy impurity ions near the center of the plasma column is discussed. The density distribution of the impurity ions should be controllable by the external magnetic field.

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A fluid model is proposed in order to simulate the waves in a two-conponent plasma. The one-dimensional transfer and Maxwell's equations are computed by the modified 2 step Lax-Wendroff method as an initial value problem. In the model, the tempral and spatial dimensions can be made smaller by properly changing the ion to electron mass-ratio, light velocity and magnetic field. Therefore, the transverse and longitudinal waves are included preserving the characteristics of the linear dispersion relation.
First, the small amplitude waves deduced from the linearized MHD-Maxwell's equations are simulated to compute the dispersion relations. The results agree with the theoretical ones for all the ranges, including ones where the phase velocity of the waves is faster than the light velocity.
Secondly, the large amplitude waves are simulated under a condition without the decay instabilities to obtain the frequency and wave-number spectra. The higher harmonics of the wave number as well as the frequency for the excited wave appear due to the nonlinearity. The high and low frequency waves, which have the same wave-number and fluctuation components as those for exciting waves, are excited strongly. Moreover, the beat waves are also excited by mode-mode coupling among the waves.

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