Finite Beta Effects on Dynamic Ergodic Divertor

在最近的托卡马克实验中，人们注意到随机场线降低了由边缘局域模（ELM）驱动的偏滤器板的强热负荷。随机磁力线是由外部扰动场产生的，称为动态各态历经偏滤器（DED）引起的共振磁扰动（RMP）。从高β仿星器平衡的观点来看，三维效应对DED场的影响是非常重要的，因为压力引起的扰动场使周边区域的磁力线进一步具有随机性。然而，在目前的RMP场的分析中，真空螺旋扰动场叠加在二维MHD平衡，所谓的真空近似，被广泛使用。由于真空近似不包括等离子体响应，考虑等离子体响应及其影响是关键和迫切的问题，在这项研究中，作为三维MHD模拟的第一步，全三维非轴对称托卡马克的MHD平衡的数值求解和平衡响应进行了研究。在这项研究中，我们使用了三维MHD平衡程序HINT 2，它被广泛用于分析螺旋系统等离子体的三维平衡。通过对三维磁流体平衡的分析，发现了磁拓扑结构的变化，这在真空近似下是没有的。这是三维MHD模型与真空近似之间的一个重要环节。

In recent tokamak experiments, it is noted that stochastic field lines reduce strong heat load driven by the edge localize mode(ELM) to the divertor plate. Stochastic field lines are produced by the external perturbed field and it is called the Resonat Magnetic Perturbation(RMP) by Dynamic Ergodic Divertor(DED). From the viewpoint of high-βstellarator equilibrium, 3D effects on the DED field are very important because pressure-induced perturbed field makes further stochasticity of magnetic field lines in the peripheral region. However, in present analysis of RMP fields, a vacuum helical perturbed field superimposed on a 2D MHD equilibrium, a so-called vacuum approximation, is widely used. Since the vacuum approximation does not include the plasma response, considerations including the plasma response and its impact are critical and urgent issue.In this study, as a first step of 3D MHD modeling, the fully 3D MHD equilibrium of non-axisymmetric tokamak is solved numerically and equilibrium responses are studied. For this study, we use a 3D MHD equilibrium code HINT2, which is widely used to analyze the 3D equilibrium of helical system plasmas. Analyzing 3D MHD equilibrium, change of the magnetic topology was found. This does not appear in the vacuum approximation. This is an important point between the 3D MHD modeling and the vacuum approximation.