Structural Model Analysis of Bistable Magnetized Plasma and Study on Dynamic Control

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In this study, we aimed at establishing a new model after clarifying the mechanism of transition phenomena, which have not been explored, in magnetized plasmas, and tried to control the transition behavior based on this understanding.We controlled the density distribution and the sheared flow, and the investigated the self-excited, bistable density transition phenomena, by biasing voltage statically and actively to the ten concentric rings immersed into a rf produced, magnetized plasma with a large diameter of 45 cm. Detailed spatio-temporal structures were measured by developed 24-channel probes and logger system (40 ch. with 50 ns and 10 μs sampling times and 12-16 bits). Potential transition phenomena were observed globally at the same time of global density transition Changing time of the bias current (down to 1-2 μs) was shorter than that of the density (<1 ms), and that of the potential was slow (>1 ms). Differences of this time between observed regions were also observed. There were a few steps of transitions, and the first one was on the order of 1-10 μs. From these results, it was found that the change near the electrode region was important to trigger the transition. Simulation results also support these phenomena (importance of the ion bunching motion).Furthermore, there were hystereses of the staying time probability and average staying time as to the biased voltage (not dc hestereses but stochastic sense of ones), and these were also observed from distributions of density and floating potential. From these results, it was also suggested that the importances of fine spatial structures and the role of the region near the electrode, which are very interesting features.