Role of shearedE × Bflow in self-organized, improved confinement states in magnetized plasmas
Role of shearedE × Bflow in self-organized, improved confinement states in magnetized plasmas
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DOI：
10.1063/1.5142734
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发表时间：
2020-06
影响因子：
2.2
通讯作者：
K. Burrell
中科院分区：
文献类型：
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作者：
K. Burrell
在过去几十年中，磁聚变研究的一个重要成就是对剪切E × B流湍流解相关和稳定化过程的理论发展和实验验证，这表明E × B剪切效应在磁化等离子体中是普遍存在的。这种湍流去相关和稳定的概念具有解释限制器和偏滤器托卡马克、仿星器和镜像机中H模边缘输运势垒、VH模等离子体中更宽的边缘输运势垒以及托卡马克中形成的核心输运势垒所需的普遍性。在线性器械中也观察到类似的效果。这些限制改善的例子是相当大的物理利益，它是不经常的系统自组织，以减少运输时，一个额外的自由能的来源是适用于它。与E × B速度剪切相关的运输减少也是非常实际的好处，聚变研究，因为它有助于大大增加聚变产率在所有DT磁聚变实验进行到目前为止。输运减少涉及的基本物理是E × B剪切对等离子体中湍流涡旋的增长、径向范围和相位相关性的影响。相同的基本输运减少过程可以在等离子体的各个部分中操作，因为存在多种方式来改变径向电场Er。在这一领域的一个重要的次要主题是E × B速度剪切和磁剪切的协同效应。虽然E × B速度剪切似乎对更广泛的微观湍流类别有影响，但磁剪切可以减轻E × B速度剪切的某些潜在有害影响，并促进湍流稳定。我们目前在这一领域的理解是几十年的结果，在理论，建模和诊断的发展结合持续的实验研究交织在一起的努力。这些实验已经清楚地表明，增加E × B剪切导致湍流和传输的减少。实验结果与基本理论模型基本一致，尽管在我们得到一个包含E × B剪切效应的磁化等离子体输运的完全预测理论之前还有大量的工作要做。
A major scientific success story of magnetic fusion research in the past several decades has been the theoretical development and experimental testing of the process of turbulence decorrelation and stabilization by sheared E × B flow, which shows that E × B shear effects are ubiquitous in magnetized plasmas. This concept of turbulence decorrelation and stabilization has the universality needed to explain the H-mode edge transport barriers seen in limiter and divertor tokamaks, stellarators, and mirror machines; the broader edge transport barrier seen in VH-mode plasmas; and the core transport barriers formed in tokamaks. Similar effects are seen in linear devices. These examples of confinement improvement are of considerable physical interest; it is not often that a system self-organizes to reduce transport when an additional source of free energy is applied to it. The transport decrease associated with E × B velocity shear is also of great practical benefit to fusion research, since it contributed to substantially increased fusion yield in all DT magnetic fusion experiments conducted to date. The fundamental physics involved in transport reduction is the effect of E × B shear on the growth, radial extent, and phase correlation of turbulent eddies in the plasma. The same basic transport reduction process can be operational in various portions of the plasma because there are a number of ways to change the radial electric field Er. An important secondary theme in this area is the synergistic effect of E × B velocity shear and magnetic shear. Although the E × B velocity shear appears to have an effect on broader classes of microturbulence, magnetic shear can mitigate some potentially harmful effects of E × B velocity shear and facilitate turbulence stabilization. Our present understanding in this area is the result of a multi-decade, intertwined effort in theory, modeling, and diagnostic development combined with continuing experimental investigations. These experiments have clearly demonstrated that increased E × B shear causes reductions in turbulence and transport. The experimental results are generally consistent with the basic theoretical models although considerable work remains to be done before we have a fully predictive theory of transport in magnetized plasmas including E × B shear effects.