JET装置运行条件下的阿尔芬波特性研究

Case Studies of Alfvén Eigenmodes in JET

JET装置运行在先进托卡马克区域,在先进托卡马克区域内存在着负磁剪切,s<0(s=rdq/dr),在正剪切和负磁剪切下理论上都发现了约束在α(α=-q2Rdβ/dr)引发气球模驱动的势β里的离散阿尔芬本征模(αTAE)。q是安全因子,β是等离子体压力与磁压力之比,R和r分别代表托卡马克的大半径和小半径。这些模式的耗散率都很小,很容易被高能量粒子激发成不稳定性模式。在现行的大型托卡马克(如:DⅢ-D,JET,JT-60U)中实验上已经观察到了许多阿尔芬现象,这种离散阿尔芬本征模式是一种去理解这些实验现象的潜在物理机制。

[ Abstract] JET operates in advanced regimes with negative magnetic shear, s 〈 0（s = rdq/dr）. Discrete Alfven eigenmodes trapped in the α-induced （α= -q2Rβ/dr） potential well due to the pressure gradient and bollooning curvature effects are found theoretically in the parameter regime of JET experiments with normal magnetic shear and negative magnetic shear. Here, q is the safty factor, β is the ratio of plasma to magnetic pressures, and R and r are, respectively, the major and minor radii. These eigenmodes experience negligible continuum damping due to wave energy tunneling that they could be readily destabilized by energetic particles. Alfven waves have been seen JET,DⅢ-D and JT-60U experiments. The discrete Alfven eigenmodes are shown to be a possible mechanism to understand the experimentally observed Alfven modes.