Investigations on Confinement Improvement by Supressing Microscopic Instabilities in Toroidal Plasmas

本研究的目的是发展减少反常输运的方法。基于交叉场输运是由微观不稳定性驱动的工作假设，我们研究了通过抑制微观不稳定性来降低输运系数的方法，获得了Torsatron/Heliotron组态中反常输运的新的理论结果。该理论包括电流扩散率的作用。这个新的模型公式虽然只适用于磁丘系统，但解释了这类器件中的大部分约束实验观察。如果通过实验进一步验证，该方法将为预测一种能减少反常输运的构型提供指导原则。在托卡马克装置中，环性是引起反常输运的关键因素。理论模型可以扩展到系统的磁阱，通过采用气球形式主义。通过对电流扩散性的研究，我们得到了一个新的物理图景。提出了全球不稳定性加速增长的机制。由整体不稳定性引起的磁编织引起电流扩散系数的增强，从而提高了模的增长率。总而言之，这一研究项目在原来的方案中以及在研究的意想不到的领域中都显示出相当大的进展。

The objective of this research is to develop the method to reduce the anomalous transport. Based on the working hypothesis that the cross field transport is driven by microscopic instabilities, we study the way to reduce the transport coefficient by suppressing the microinstabilities.By this research project, we have obtained a new theoretical result on the anomalous transport in Torsatron/Heliotron configurations. The theory includes the roles of the current diffusivity. This new model formula, though appricable only to the systems with the magnetic hill, explains the majority of the experimental observations on confinement in such devices. If further verification will be gained through future examination with experiments, this method will give a guiding principle to predict a cofiguration, in which anomalous transport is reduced. In tokamaks, it has been shown that the toroidicity is a critical element to cause the anomalous transport. The theoretical model can be extended to systems with the magnetic well, by employing the ballooning formalism. The extension and generalization are left for the future study.By studying the current diffusicity, we have obtained a new phsics picture of the disruptive phenomena. The mechanism of the accelerated growth of the global instabilities is presented. The magnetic braiding by the global instabilities gives rise to the enhanced current diffusivity, which then increases the growth rate of the mode.In summary, this research project has shown a considerable progress in the original programme as well as in the unexpected area of the research.