Effects of E×B velocity shear and magnetic shear on turbulence and transport in magnetic confinement devices
TLDR
The ExB shear stabilization model was originally developed to explain the transport barrier formed at the plasma edge in tokamaks after the L (low) to H (high) transition as mentioned in this paper.Abstract:
One of the scientific success stories of fusion research over the past decade is the development of the ExB shear stabilization model to explain the formation of transport barriers in magnetic confinement devices. This model was originally developed to explain the transport barrier formed at the plasma edge in tokamaks after the L (low) to H (high) transition. This concept has the universality needed to explain the edge transport barriers seen in limiter and divertor tokamaks, stellarators, and mirror machines. More recently, this model has been applied to explain the further confinement improvement from H (high)-mode to VH (very high)-mode seen in some tokamaks, where the edge transport barrier becomes wider. Most recently, this paradigm has been applied to the core transport barriers formed in plasmas with negative or low magnetic shear in the plasma core. These examples of confinement improvement are of considerable physical interest; it is not often that a system self-organizes to a higher energy state with reduced turbulence and transport when an additional source of free energy is applied to it. The transport decrease that is associated with ExB velocity shear effects also has significant practical consequences for fusion research. The fundamental physics involved in transport reduction is the effect of ExB shear on the growth, radial extent and phase correlation of turbulent eddies in the plasma. The same fundamental transport reduction process can be operational in various portions of the plasma because there are a number ways to change the radial electric field Er. An important theme in this area is the synergistic effect of ExB velocity shear and magnetic shear. Although the ExB velocity shear appears to have an effect on broader classes of microturbulence, magnetic shear can mitigate some potentially harmful effects of ExB velocity shear and facilitate turbulence stabilization.read more
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References
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Journal Article
Plasma Physics and Controlled Nuclear Fusion Research
TL;DR: In this paper, the first experiments in JET have been described, which show that this large tokamak behaves in a similar manner to smaller tokak, but with correspondingly improved plasma parameters.
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Regime of Improved Confinement and High Beta in Neutral-Beam-Heated Divertor Discharges of the ASDEX Tokamak
TL;DR: In this article, a new operational regime has been observed in neutral-injection-heated ASDEX divertor discharges, characterized by high aspect ratio values comparable to the aspect ratio of Ohmic discharges.
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Influence of sheared poloidal rotation on edge turbulence
TL;DR: In this paper, the impact of radially sheared poloidal flows on ambient edge turbulence in tokamaks is investigated analytically, and a hybrid time scale weighted toward the former and the latter is found to govern the decorrelation process.
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Multiple Flow Equilibria in the Atmosphere and Blocking
J. G. Charney,John G. DeVore +1 more
TL;DR: In this paper, a barotropic channel model is used to study the planetary-scale motions of an atmosphere whose zonal flow is externally driven, and the existence of two stable equilibrium states of very different character may be produced by the same forcing: one is a high-index flow with a weak wave component and a relatively stronger zonal component which is much farther from linear resonance.