Low-aspect-ratio reversed field pinch plasma equilibria with finite surface toroidal current density
Low-aspect-ratio reversed field pinch plasma equilibria with finite surface toroidal current density
复制标题
具有有限表面环形电流密度的低纵横比反向场箍缩等离子体平衡
DOI：
10.1088/0741-3335/47/8/010
复制
发表时间：
2005
影响因子：
2.2
通讯作者：
Y. Yagi
中科院分区：
文献类型：
--
作者：
H. Sugimoto;H. Ashida;K. Hayase;Y. Hirano;T. Kurasawa;Y. Yagi
低纵横比反向场箍缩（RFP）等离子体预计将产生平衡，其中撕裂模式的谐振表面分离良好的高纵横比RFP等离子体相比。安全系数q的分布决定了谐振表面的模式分离。研究了不同长径比A时等离子体的q分布、等离子体压强与磁能之比β和平行于磁力线的电流密度μ。通过在等离子体边缘引入有限的表面环向电流密度，提出了一种新的Mercier稳定RFP等离子体。本文研究了低纵横比（低A）的有限表面环向电流对等离子体压强q、μ、β和极向磁能比βp的影响。调查是使用一个平衡模型与有限的压力，其中指定的Grad-Shafranov（GS）方程中的未知函数。指定的功能是由一些数字参数，允许系统的变化的平衡。在环坐标系下求解了GS方程，确定了Mercier稳定平衡点的β极限。首先，我们证实了中心的q，q 0，随着A的减小而增加。结果表明，q、β和βp的分布对A有很强的依赖性。所获得的β和βp随A的减小而减小。特别是，β的减小不同于托卡马克的情况。尽管A很低，但通过将环形电流设置为在等离子体边缘有限作为边界条件，β的减小被恢复。
Low-aspect-ratio reversed field pinch (RFP) plasmas are expected to produce equilibria in which the resonant surfaces for tearing modes are well separated compared with high-aspect-ratio RFP plasmas. The profile of the safety factor, q, determines the mode separation of the resonant surfaces. The q profiles, the ratio of plasma pressure to magnetic energy, β, and the parallel current density to the magnetic field lines, μ, are studied with the varying aspect ratio, A. A new Mercier stable RFP plasma is proposed by introducing a finite surface toroidal current density at the plasma edge. The aim of this study is to investigate the effect of a finite surface toroidal current with a low-aspect-ratio (low A) on the profiles of q, μ, β and the ratio of plasma pressure to poloidal magnetic energy, βp. The investigation is performed using an equilibrium model with a finite pressure, in which unknown functions in the Grad–Shafranov (GS) equation are specified. Specified functions are composed of some numerical parameters that allow systematic variation of equilibria. The GS equation is solved in the toroidal coordinate for various A values, where the β limit of Mercier stable equilibria is determined. First we confirmed that q at the centre, q0, increases as A decreases. The result shows that the profiles of q, β and βp, strongly depend on A. The β and βp obtained decrease with decreasing A. In particular, the decrease in β differs from the case of a tokamak. The decrease in β is recovered, in spite of a low A, by setting the toroidal current to be finite at the plasma edge as a boundary condition.