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Role of sheared E × B flow in self-organized, improved confinement states in magnetized plasmas
Physics of Plasmas ( IF 2.2 ) Pub Date : 2020-06-01 , DOI: 10.1063/1.5142734
K. H. Burrell 1
Affiliation  

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.

中文翻译:

剪切 E × B 流在磁化等离子体中自组织、改进的限制状态中的作用

过去几十年磁聚变研究的一个主要科学成功案例是对剪切 E × B 流的湍流去相关和稳定过程的理论发展和实验测试,这表明 E × B 剪切效应在磁化等离子体中无处不在. 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、仿星器和镜机中看到的 H 模式边缘传输障碍所需的普遍性;在 VH 模式等离子体中看到的更宽的边缘传输势垒;以及在托卡马克形成的核心运输障碍。在线性器件中可以看到类似的效果。这些改善坐月子的例子具有相当大的物理意义;当一个额外的自由能源被施加到系统上时,系统通常不会自组织以减少运输。与 E × B 速度剪切相关的输运减少对聚变研究也有很大的实际好处,因为它有助于在迄今为止进行的所有 DT 磁聚变实验中显着增加聚变产率。传输减少涉及的基本物理学是 E × B 剪切对等离子体中湍流涡旋的生长、径向范围和相位相关性的影响。相同的基本传输还原过程可以在等离子体的各个部分运行,因为有多种方法可以改变径向电场 Er。该领域的一个重要次要主题是 E×B 速度剪切和磁剪切的协同效应。尽管 E × B 速度剪切似乎对更广泛的微湍流有影响,但磁剪切可以减轻 E × B 速度剪切的一些潜在有害影响并促进湍流稳定。我们目前在该领域的理解是在理论、建模和诊断发展方面进行了数十年、相互交织的努力以及持续的实验研究的结果。这些实验清楚地表明,增加的 E × B 剪切会导致湍流和输运减少。实验结果通常与基本理论模型一致,尽管在我们拥有包括 E×B 剪切效应在内的磁化等离子体中传输的完全预测理论之前,还有大量工作要做。磁剪切可以减轻 E × B 速度剪切的一些潜在有害影响并促进湍流稳定。我们目前在该领域的理解是在理论、建模和诊断发展方面进行了数十年、相互交织的努力以及持续的实验研究的结果。这些实验清楚地表明,增加的 E × B 剪切会导致湍流和输运减少。实验结果通常与基本理论模型一致,尽管在我们拥有包括 E×B 剪切效应在内的磁化等离子体中传输的完全预测理论之前,还有大量工作要做。磁剪切可以减轻 E × B 速度剪切的一些潜在有害影响并促进湍流稳定。我们目前在该领域的理解是在理论、建模和诊断发展方面进行了数十年、相互交织的努力以及持续的实验研究的结果。这些实验清楚地表明,增加的 E × B 剪切会导致湍流和输运减少。实验结果通常与基本理论模型一致,尽管在我们拥有包括 E×B 剪切效应在内的磁化等离子体中传输的完全预测理论之前,还有大量工作要做。理论、建模和诊断开发方面的努力与持续的实验研究相结合。这些实验清楚地表明,增加的 E × B 剪切会导致湍流和输运减少。实验结果通常与基本理论模型一致,尽管在我们拥有包括 E×B 剪切效应在内的磁化等离子体中传输的完全预测理论之前,还有大量工作要做。理论、建模和诊断开发方面的努力与持续的实验研究相结合。这些实验清楚地表明,增加的 E × B 剪切会导致湍流和输运减少。实验结果通常与基本理论模型一致,尽管在我们拥有包括 E×B 剪切效应在内的磁化等离子体中传输的完全预测理论之前,还有大量工作要做。
更新日期:2020-06-01
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