Effects of energetic-ion-driven MHD instabilities in a reversed magnetic shear plasma on energetic ion transport

在大螺旋装置（LHD）中产生了一种不同于托卡马克RS等离子体的反向磁剪切等离子体，其剪切在等离子体中心区域为正，在边缘区域为负。在这种等离子体中，反向磁剪切Alfven本征模式（RSAE）和测地声模式（GAM）被高能离子同时激发。比较了在托卡马克中观察到的RSAE和GAM的特性、这些不稳定性的非线性耦合以及它们对高能离子约束和背景体等离子体的影响。比较研究对于系统、全面地认识这些不稳定性具有重要意义。

A reversed magnetic shear(RS)-plasma where the shear is positive in plasma central region and negative in the edge region, different from the tokamak RS-plasma was produced in the Large Helical Device(LHD). In such plasma, reversed magnetic shear Alfven eigenmode(RSAE) and geodesic acoustic mode(GAM) were concurrently excited by energetic ions. Characteristics of observed RSAE and GAM, nonlinear coupling of these instabilities, and their impacts on confinement of energetic ions and background bulk plasma were compared with those in tokamaks. The comparison study is important for systematic and comprehensive understanding of these instabilities.