Helical distortion of the core part of tokamak plasma, which is called a helical core or a long-lived mode, is investigated by means of three-dimensional magnetohydrodynamic equilibrium calculations. It is found that the magnitude of the helical distortion strongly depends on the shape of the plasma boundary for weakly reversed shear plasmas. The triangularity of the boundary enhances the amplitude of helical distortion. In addition, reversed D-shape plasmas also exhibit a helical core. It is also found that the triangularity lowers the critical β for the onset of a helical core; furthermore, the critical β vanishes when the triangularity exceeds a certain value. On the other hand, the influence of the ellipticity on the amplitude of helical distortion strongly depends on β. The ellipticity enhances the amplitude at high β, while it reduces the amplitude at low β.

中文翻译：

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等离子体边界形状对托卡马克等离子体中螺旋核/长寿命模式的影响

通过三维磁流体力学平衡计算研究了托卡马克等离子体核心部分的螺旋畸变，称为螺旋核心或长寿命模式。研究发现，对于弱反向剪切等离子体，螺旋变形的大小很大程度上取决于等离子体边界的形状。边界的三角形增强了螺旋形畸变的幅度。此外，反向 D 形等离子体也表现出螺旋形核心。还发现三角形降低了螺旋核开始的临界β；此外，当三角形度超过某个值时，临界 β 消失。另一方面，椭圆度对螺旋畸变幅度的影响强烈依赖于β。椭圆度在高 β 时增强了振幅，