Homoclinic tangles, bifurcations and edge stochasticity in diverted tokamaks
Homoclinic tangles, bifurcations and edge stochasticity in diverted tokamaks
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DOI：
10.1002/ctpp.200410034
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发表时间：
2003-09
影响因子：
1.6
通讯作者：
T. Evans;R. Roeder;J. Carter;B. I. Rapoport
中科院分区：
文献类型：
--
作者：
T. Evans;R. Roeder;J. Carter;B. I. Rapoport
由于小的非轴对称共振扰动，极向转向托卡马克的边界和基座区域特别容易受到真空磁场随机性的影响。最近对转向托卡马克中的分线拓扑的计算表明，当受到小的磁扰动时，存在复杂的不变流形结构，称为同宿缠结。这些结构出现在相对较低的扰动阈值之上，该阈值取决于某些平衡形状参数。同宿缠结表示将未受扰动的分界线分裂为与每个 X 点（双曲点）相关的稳定和不稳定的不变流形。组成同宿缠结的流形设定了边界，规定了如何组织随机场线轨迹，即来自未受扰动分界线内部域的场线如何混合并传输到面向等离子体的表面，例如偏滤器目标板和突出的挡板结构。因此，这些缠结的拓扑结构决定了哪些面向等离子体的组件最有可能与逸出的磁场线以及它们携带的平行热量和粒子通量相互作用。 （© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA，魏因海姆）
The boundary and pedestal region of a poloidally diverted tokamak is particularly susceptible to the onset of vacuum magnetic field stochasticity due to small non‐axisymmetric resonant perturbations. Recent calculations of the separatrix topology in diverted tokamaks, when subjected to small magnetic perturbations, show the existence of complex invariant manifold structures known as homoclinic tangles. These structures appear above a relatively low perturbation threshold that depends on certain equilibrium shape parameters. Homoclinic tangles represent a splitting of the unperturbed separatrix into stable and unstable invariant manifolds associated with each X‐point (hyperbolic point). The manifolds that make up homoclinic tangles set the boundaries that prescribe how stochastic field line trajectories are organized i.e., how field lines from the inner domain of the unperturbed separatrix mix and are transported to plasma facing surfaces such as divertor target plates and protruding baffle structures. Thus, the topology of these tangles determines which plasma facing components are most likely to interact with escaping magnetic field lines and the parallel heat and particle flux they carry. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)