发表机构
Center for Energy Research, University of California San Diego; University of California Merced（加州大学圣地亚哥分校能源研究中心; 加州大学默塞德分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过场线追踪、庞加莱分析和蒙特卡洛模拟，揭示嵌套共振岛链的缠结结构控制DIII-D托卡马克磁场线逃逸，提出基于主交点的输运屏障提取方法，并验证转轮叶瓣输运模型。
AI 中文摘要
磁约束等离子体中的磁场线输运通常被建模为通过共振扰动产生的随机磁层的扩散。然而，实验相关的磁组态经常表现出比完全随机模型预测的慢得多的输运速率，表明存在未解决的动力障碍。在本工作中，我们研究了嵌套共振岛链及其相关不变流形在调节DIII-D托卡马克放电#171491边缘磁拓扑输运中的作用，该放电受到强n=3共振磁扰动的影响。利用场线追踪、庞加莱分析和流形计算，我们识别了与周期一和周期十双曲点相关的同宿和异宿缠结的层级结构。基于主交点开发了一种系统构造方法，从完整流形几何中提取部分输运屏障，并将混沌区域划分为动态不同的域。蒙特卡洛模拟表明，当仅考虑最外层周期一边界时，场线逃逸表现出双指数特征，反映了与周期十岛链相关的长寿命“粘性”区域的存在。当内层周期十边界被明确纳入蒙特卡洛模拟时，逃逸过程近似变为单指数，并由转轮叶瓣输运准确描述。测得的逃逸率与从转轮叶瓣面积和场线映射的辛结构获得的预测一致。这些结果表明，嵌套缠结提供了控制磁场线逃逸的定量输运骨架，并为分析现实聚变等离子体磁组态中的输运屏障、坎托里和叶瓣动力学建立了框架。
英文摘要
Magnetic field-line transport in magnetically confined plasmas is commonly modeled as diffusion through stochastic magnetic layers generated by resonant perturbations. However, experimentally relevant magnetic configurations frequently exhibit transport rates that are substantially slower than predicted by fully stochastic models, indicating the presence of unresolved dynamical barriers. In this work, we investigate the role of nested resonant island chains and their associated invariant manifolds in regulating transport within the edge magnetic topology of DIII-D tokamak discharge #171491 subjected to strong n=3 resonant magnetic perturbations. Using field-line tracing, Poincare analysis, and manifold calculations, we identify a hierarchy of homoclinic and heteroclinic tangles associated with both period-one and period-ten hyperbolic points. A systematic construction based on primary intersection points is developed to extract partial transport barriers from the full manifold geometry and divide the chaotic region into dynamically distinct domains. Monte Carlo simulations reveal that field-line escape exhibits a bi-exponential character when only the outermost period-one boundary is considered, reflecting the presence of a long-lived "sticky" region associated with the period-ten island chain. When the inner period-ten boundary is explicitly incorporated into the Monte Carlo, the escape process becomes approximately single exponential and is accurately described by turnstile lobe transport. The measured escape rate agrees with predictions obtained from the turnstile lobe area and the symplectic structure of the field-line map. These results demonstrate that nested tangles provide a quantitative transport skeleton governing magnetic-field-line escape and establish a framework for analyzing transport barriers, cantori, and lobe dynamics in realistic fusion-plasma magnetic configurations.
