CRITICAL MAGNETIC SHEAR FOR THE TOKAMAK IDEAL INTERNAL KINK MODE IN THE ION KINETIC REGIME

It is shown that for the ideal internal kink mode of tokamak plasma, there exists a critical magnetic shear s_0c for its excitation when the finite ion Larmor radius effect is considered in the mode singular layer. This can be related to the sudden onset of the sawtooth and also to the stabilization of the sawtooth by the trapped hot ions observed experimentally. The alpha particle effect on this mode is revisited and some new results are reported.     

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基于Hasegawa-Wakatani湍流模型,数值模拟了托卡马克边缘等离子体中漂移波湍流和相关的反常粒子输运.从等离子体动量守恒方程出发导出了不采用常规的布辛涅斯克近似的带状流方程,论证了大振幅密度扰动和湍性粒子流对激发带状流的贡献可等效地对应于低阶负粘滞阻尼效果.数值模拟表明,大振幅密度扰动的非线性大大增强了带状流饱和振幅,从而有效抑制了湍性粒子输运.研究结果阐明了托卡马克边缘等离子体大振幅密度扰动的非线性对驱动等离子体旋转、动量输运和带状流的重要性.     

高能α粒子慢化分布的一种经验近似

本文在假设高能α粒子遵从慢化分布的基础上,对慢化分布作多级麦氏分布经验近似,从而借助已有的麦氏分布的介电张量给出了慢化分布的介电张量,并用它来研究高能α粒子对离子回旋频率范围的快波传播和吸收的影响。     

动力环形ηi模的局部和非局部描述

解析给出环形ηｉ模包括离子通行共振、磁漂移共振以及有限拉莫半径效应的局部和非局部完全动力色散关系，通过比较局非局部描述下环形ηｉ模增长率的大小，指出了局部近似适用的参数范围。     

Magneto-Hydrodynamic High-n Ballooning Mode Instability of an Analytic Axi-Symmetric Toroidal Equilibrium with Arbitrary Aspect Ratio

An exact ballooning mode eigen-equation is derived to study stability of axi-symmetric toroidal plasma with arbitrary aspect ratio, including the tokamak, the finite aspect ratio and the spherical torus plasmas. For comparison with the widely used （ s-α） model, an analytic exact equilibrium configuration with circular magnetic surfaces is analysed in detail. It is indicated that the （s - α） model needs to be improved for more realistic configurations.     

Tokamak resistive magnetohydrodynamic ballooning instability in the negative shear regime

Improved confinement of tokamak plasma with central negative shear is checked against the resistive ballooning mode. In the negative shear regime, the plasma is always unstable for purely growing resistive ballooning mode. For a simplest tokamak equilibrium model, the s-α model, characteristics of this kind of instability are fully clarified by numerically solving the high n resistive magnetohydrodynamic ballooning eigen-equation. Dependences of the growth rate on the resistivity, the absolute shear value, the pressure gradient are scanned in detail. It is found that the growth rate is a monotonically increasing function of a while it is not sensitive to the changes of the shear s, the initial phase θ0 and the resistivity parameter εR.     

托卡马克等离子体粒子输运方程的半解析研究

在输运算子为线性算子的条件下,对托卡马克等离子体粒子输运方程的求解进行了系统的分析。粒子输运由向外扩散和向内对流构成。给出了用格林函数表示的普遍解和相应的Ｓｔｕｒｍ－Ｌｉｏｕｖｉｌｌｅ本征函数及本征值,对粒子源处在边界附近（浅加料）的情形,通过解的互补性关系,可以获得品质好的广义傅里叶展开,从解的一般性质看出,在器壁再循环很小时,由第一个本征函数描述的粒子密度剖面对应于较高的峰化因子。对于瞬间内部     

等离子体湍流理论研究的最新进展

评述和分析了磁约束核聚变理论研究、数值模拟和实验研究等方面最近几年共同关心的一个重要问题——寻找托卡马克等离子体湍流中的带状剪切流（zonal flows）。简要介绍了作者最近对电阻性-重力模湍流中的带状剪切流的研究结果。 Progress of the research on the zonal flows in tokamak plasma turbulence is surveyed, especially it is reviewed that the zonal flows observed in the experiments and numerical simulations on atmosphere turbulence and ocean turbulence and the discovery of H-mode in tokamak experiments how lead the researchers in magnetic confinement fusion community to find out the existence of the zonal flow in tokamak plasma turbulence and subsequently give the experimental verification of its existence. Finally, the results of our research on zonal flow generation and evolution in resistive-g mode turbulence are presented in brief.     

Role of the zonal flow in multi-scale multi-mode turbulence with small-scale shear flow in tokamak plasmas

The structural characteristics of zonal flows and their roles in the nonlinear interaction of multi-scale multi-mode turbulence are investigated numerically via a self-consistent Landau-fluid model. The multi-mode turbulence here is composed of a shorter wavelength electromagnetic (EM) ion temperature gradient (ITG) mode and a Kelvin-Helmholtz (KH) instability with long wavelengths excited by externally imposed small-scale shear flows. For strong shear flow, a prominent periodic intermittency of fluctuation intensity except for dominant ITG component is revealed in turbulence evolution, which onset time depends on the ion temperature gradient and the shear flow amplitudes corresponding to different KH instabilities. It is identified that the intermittency phenomenon results from the zonal flow dynamics, which is mainly generated by the KH mode and back-reacts on it. It is demonstrated that the odd symmetric components of zonal flow (same symmetry as the external flow) make the radial parity of the KH mode alteration through adjusting the drift velocities at two sides of the resonant surface so that the KH mode becomes bursty first. Afterwards, the ITG intermittency follows due to nonlinear mode coupling. Parametric dependences of the features of the intermittency are elaborated. Finally, associated turbulent heat transport is evaluated.