Research of Disruptive Instability based on Anomalous Transport

本研究项目的目的是研究等离子体形变的突然增长(触发现象)以及等离子体轮廓的快速演化的物理机制，在这个研究过程中，从理论上预测了存在湍流-湍流转变。结果表明，由于湍流的转折，微扰的突然开始是可能的。崩塌开始时增长率的突变是崩塌事件的直接原因。扰动的增长率不是等离子体参数的光滑函数，等离子体参数是不稳定性的驱动力。相比之下，当全球驱动力达到一定阈值时，增长率就会出现分叉。扰动的演变变成了爆炸性的。导致破裂的等离子体变形不是线性不稳定性的结果，而是表现为亚临界湍流。从理论上预测了扰动的驱动力和增长率之间的滞后关系，并通过实验观察对这一理论观点进行了检验。通过对崩塌事件的观测发现，几乎所有的破坏现象都普遍观察到增长率的突变。新的物理图景将成为未来颠覆现象物理学进展的基础。

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.