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

本课题的目的是建立一种自一致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平衡的数值方法，并研究等离子体电流对MHD平衡的影响。结果如下：(1)编制了考虑环面波纹等轴对称破缺的托卡马克等离子体MHD平衡、粒子轨道和新古典输运的一系列数值计算程序。对具有负剪切的高β低长径比托卡马克进行了分析。此外，还研究了圆形截面高q波纹托卡马克中高能粒子的轨道。(2)利用仿星器展开法和真空场计算程序，通过场线示踪分析，初步研究了等离子体净电流对L=2氦离子等离子体磁岛形成的影响。虽然仿星器在螺旋轴结构下无法展开，但研究磁岛的形成，特别是在弱磁剪切的情况下，是非常重要的。作为这类构型的例子，研究了L=1螺旋轴的氦离子等离子体在不考虑磁岛的情况下的MHD平衡和粒子轨道。不假设有嵌套通量面存在的三维MHD平衡程序是其自洽分析所必需的。为此引入了pie代码，并对LHD等离子体进行了测试计算。还打算对PIES代码进行进一步改进。

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.