Effects of Self-Consistent Flow on Island Generation in Interchange Mode

The time evolution of magnetic island in the nonlinear phase of the resistive interchange mode is examined in the cylindrical geometry. The effects of self-consistent uniform poloidal flow is taken into account. In this case, the reconnection of the magnetic field line occurs both at the saturation of the dominant unstable mode and at the saturation of the n = 0 mode, where n is the toroidal mode number, through the curvature change of perturbed poloidal flux surface

Tearing Mode in a Heliotron Plasma

Tearing mode is studied in a heliotron plasma by varying the net toroidal current. Ideal internal kink mode can be unstable when two resonant magnetic surfaces are generated. The tearing mode is found at the current below the marginal stability value for the ideal internal kink mode. The mode structure is localized around the inner resonant surface like the internal kink mode. The growth rate and the mode structure can be affected by the unstable internal kink mode. Tearing and resistive interchange hybrid mode is also obtained at a finite beta

ステラレータ/ヘリオトロン配位における三次元平衡および安定性の数値計算に基づく理論的研究

京都大学0048新制・課程博士工学博士甲第4544号工博第1115号新制||工||797(附属図書館)UT51-90-G111京都大学大学院工学研究科原子核工学専攻(主査)教授 若谷 誠宏, 教授 大引 得弘, 教授 木村 逸郎学位規則第5条第1項該当Kyoto UniversityDFA

Multi-scale MHD analysis of LHD plasma with background field changing

The mechanism of the partial collapse observed in the experiment with the background magnetic field changing in the Large Helical Device (LHD) is numerically investigated with a nonlinear magnetohydrodynamics (MHD) simulation. Since the different timescales of the perturbations and the background field changing have to be treated simultaneously for the analysisof this plasma, a multi-scale simulation scheme is developed. The effect of the perturbation dynamics on the equilibrium pressure and rotational transform is taken into account in this scheme. The result indicates that the collapse is caused by the destabilization of an infernal-like mode due to the magnetic hill enhanced by the change of the background field. The mechanismof the reduction of the central beta observed after the partial collapse in the experiment is also analysed in relation to the effect of the background field changing

Non-resonant global mode in LHD partial collapse with net toroidal current

A transition from an interchange mode to a non-resonant mode is found in the nonlinear magnetohydrodynamic simulation for the partial collapse in a large helical device (LHD) plasma with a net toroidal current. This transition can occur when the magnetic shear is weak and the rotational transform is close to unity in the core region. In this transition, the mode number of the dominant Fourier component is reduced. As a result of the nonlinear evolution, the (m, n) = (1, 1) component can be dominant, where m and n are the poloidal and the toroidal mode numbers, respectively. This transition is considered to be a candidate to explain the observation in the LHD experiments with the net toroidal current that show partial collapses are caused by the (1, 1) mode