The Finite Beta Effects on the Toroidal Field Ripple in a Tokamak Plasma

The efficiency of energetic ion confinement is reduced in a tokamak plasma by the non-axisymmetric field, namely the ripple field. The ripple field is produced by a finite number of toroidal field coils. It is affected by the non-axisymmetric finite beta effect. The three-dimensional MHD equilibrium calculation code VMEC is used to analyze the non-axisymmetric finite beta effect in a ripple tokamak. In the VMEC code, the flux coordinates are used, so the calculation region is limited to the area of plasma. To calculate the orbit outside the plasma, we develop a field calculation code, which is based on the Biot-Savart law. The details of the method and results are described in this paper.

J-TEXT装置上的三维磁场分析研究

为了解决二维磁场位形的局限性,对三维磁场位形的研究势在必行。基于J-TEXT平衡参数,利用VMEC程序求解得到J-TEXT装置的三维磁场位形。此外,分析了等离子体电流、压强对磁场位形的影响,论证了VMEC程序应用在J-TEXT上的可行性。结果表明,VMEC程序能够初步满足J-TEXT装置的三维磁场位形研究要求,为后续装置三维磁场位形优化提供理论和工程借鉴意义。通过比较不同的等离子体电流,压强剖面对三维磁场的计算结果,表明了等离子体电流能够改变极向磁场强度,增大压强剖面使等离子体环状膨胀,磁轴外移。