Research of Disruptive Instability based on Anomalous Transport

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The object of this research project is to study the physics mechanisms for the abrupt growth of the plasma deformation (trigger phenomena), which plays the central role in the disruption events, and the rapid evolution of plasma profiles.In this course of research, it is theoretically predicted that there is a turbulence-turbulence transition. It is shown that the abrupt start of growth of the perturbation is possible to occur owing to the transition of turbulence. The sudden change of the growth rate at the onset of the collapse is the direct cause of the collapse events.The details of theoretical finding is as follows. The growth rate of the perturbation is not a smooth function of the plasma parameters, which are driving force of the instabilities. In contrast, the growth rate is subject to a bifurcation when the global driving force reaches a certain threshold value. The evolution of the perturbation turns to be explosive. Plasma deformation that leads to disruption is not a consequence of the linear instabilities, but behaves as a subcritical turbulence. The hysteresis relation between the driving force and the growth rate of perturbations is theoretically predicted.These theoretical view is examined by reviewing experimental observations. By surveying the observations on collapse events, it is found that the abrupt jump of the growth rate is commonly observed for almost all the disruptive phenomena. The new physics picture will be a basis of the future progress of the physics of disruptive phenomena.