Potential formation theory and mode transfer in tandem mirror

The confinement of ions in axial direction along magnetic force lines in a tandem mirror is done by the potential barriers formed at both ends of the device. At this time, also electrons are confined by both polarity potentials. When potential confinement is utilized, it has been theoretically and experimentally shown that the time of confinement in axial direction can be drastically improved. In this paper, the analysis of taking the effect of radial diffusion into the equation of particle balance in axial direction taking part in potential formation is reported. Moreover, it is shown that when the abnormal transport by unstable drift wave motion is considered as this radial diffusion, and the stabilizing effect to the fluctuation arising from polarity potential is taken into the diffusion coefficient, the mode transfer regarding confining potential may occur. The potential formation model taking radial diffusion in consideration and the analysis model that causes the L/H mode transfer of confinement potential are described. Though the model which was simplified very much was used, the obtained results look reasonable. Hereafter, it is intended to refine the model. (K.I.)