Three Dimensional MHD Equilibrium and Plasma Current Effects in Rippled Tokamak/Helical System Plasma

本项目的目的是发展一种数值方法，自洽地分析波纹托卡马克或螺旋系统装置中非轴对称环面等离子体的三维MHD平衡，并研究等离子体电流对MHD平衡的影响。主要研究结果如下：(1)编制了一系列数值程序来分析托卡马克等离子体中的磁流体平衡、粒子轨道和新经典输运，考虑了环形波纹等轴对称的破缺。作为第一步，我们对具有负剪切的高β、低长宽比托卡马克进行了分析。此外，还研究了高能粒子在圆形截面高Q波纹托卡马克中的运动轨迹。(2)用星子展开法和真空场计算程序进行场线跟踪分析，初步考察了等离子体净电流对L=2氦加速器等离子体磁岛形成的影响。虽然星体膨胀技术不适用于螺旋轴构型，但研究磁岛的形成是非常重要的，特别是在弱磁切变的情况下。作为这种组态的一个例子，我们研究了不考虑磁岛的L=1螺旋轴氦-加速器等离子体的磁流体平衡和粒子轨道。为了进行自洽分析，一个不假定嵌套通量面存在的三维MHD平衡程序是必要的。为此引入了PIES程序，并对LHD等离子体进行了测试计算。还打算对PIES代码进行额外的改进。

Purposes of this project are to develop a numerical method to analyze three dimensional MHD equilibria of non-axisymmetric torus plasmas in a rippled tokamak or helical system device self-consistently and to investigate the effect of plasma current on the MHD equilibrium. Followings are the results ;(1) A series of numerical programs was prepared to analyze MHD equilibrium, particle orbit and neoclassical transport in tokamak plasmas, taking into account of breaking of axisymmetry like toroidal ripple. Analysis of high beta low aspect ratio tokamaks with negative shear has been performed as the first step. Additionally, orbits of high energy particles in a high q rippled tokamak with circular cross section are investigated.(2) The effect of plasma net current on the magnetic island formation in an L=2 heliotron plasma is examined preliminarily by the field line tracing analysis with the stellarator expansion method and the vacuum field calculation code. Though the stellarator expansion technique is not available in a helical axis configuration, it is very important to investigate the magnetic island formation especially in the case of weak magnetic shear. As an example of such configurations, MHD equilibrium and particle orbits are studied for an L=1 helical axis heliotron plasma without considering magnetic islands. A three dimensional MHD equilibrium code which does not assume the existence of nested flux surfaces is necessary for its self - consistent analysis. PIES code has been introduced for this purpose and test calculations were performed for an LHD plasma. Additional improvements of PIES code is intended to be done.