Flow shear induced fluctuation suppression in finite aspect ratio shaped tokamak plasma
T.S. Hahm,Keith H. Burrell +1 more
TLDR
In this paper, the suppression of turbulence by the E×B flow shear and parallel Flow Shear in an arbitrary shape finite aspect ratio tokamak plasma using the two point nonlinear analysis was investigated.Abstract:
The suppression of turbulence by the E×B flow shear and parallel flow shear is studied in an arbitrary shape finite aspect ratio tokamak plasma using the two point nonlinear analysis previously utilized in a high aspect ratio tokamak plasma [Phys. Plasmas 1, 2940 (1994)]. The result shows that only the E×B flow shear is responsible for the suppression of flute‐like fluctuations. This suppression occurs regardless of the plasma rotation direction and is, therefore, relevant for the very high (VH) mode plasma core as well as for the high (H) mode plasma edge. Experimentally observed in–out asymmetry of fluctuation reduction behavior can be addressed in the context of flux expansion and magnetic field pitch variation on a given flux surface. The adverse effect of neutral particles on confinement improvement is also discussed in the context of the charge exchange induced parallel momentum damping.read more
Citations
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Zonal flows in plasma—a review
TL;DR: A comprehensive review of zonal flow phenomena in plasmas is presented in this article, where the focus is on zonal flows generated by drift waves and the back-interaction of ZF on the drift waves, and various feedback loops by which the system regulates and organizes itself.
Journal ArticleDOI
Effects of E×B velocity shear and magnetic shear on turbulence and transport in magnetic confinement devices
TL;DR: 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.
Journal ArticleDOI
Foundations of nonlinear gyrokinetic theory
Alain J. Brizard,T.S. Hahm +1 more
TL;DR: The nonlinear gyrokinetic equations play a fundamental role in our understanding of the long-time behavior of strongly magnetized plasmas as mentioned in this paper, and they have been used to describe the turbulent evolution of low-frequency electromagnetic fluctuations in a nonuniform magnetization with arbitrary magnetic geometry.
Journal ArticleDOI
Comparisons and physics basis of tokamak transport models and turbulence simulations
Andris Dimits,Glenn Bateman,Michael A. Beer,Bruce I. Cohen,William Dorland,Gregory W. Hammett,Charlson C. Kim,J. E. Kinsey,Mike Kotschenreuther,Arnold H. Kritz,L. L. Lao,John Mandrekas,W. M. Nevins,Scott Parker,Aaron J. Redd,D. E. Shumaker,Richard Sydora,Jan Weiland +17 more
TL;DR: In this paper, the authors compared the performance of gyrokinetic and gyrofluid simulations of ion-temperature gradient (ITG)instability and turbulence in tokamak plasmas as well as some tokak plasma thermal transportmodels.
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Turbulent transport reduction by zonal flows : Massively parallel simulations
TL;DR: Three-dimensional gyrokinetic simulations of microturbulence in magnetically confined toroidal plasmas with massively parallel computers showed that, with linear flow damping, an asymptotic residual flow develops in agreement with analytic calculations.
References
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Journal ArticleDOI
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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Neoclassical transport of impurities in tokamak plasmas
S.P. Hirshman,D.J. Sigmar +1 more
TL;DR: In this paper, a closed set of moment equations is presented for the time evolution of thermodynamic and magnetic field quantities which results from collisional transport of the plasma and two-dimensional motion of the magnetic flux surface geometry.
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Nonlinear gyrokinetic equations for low-frequency electromagnetic waves in general plasma equilibria
E. A. Frieman,Liu Chen +1 more
TL;DR: A nonlinear gyrokinetic formalism for low-frequency (less than the cyclotron frequency) microscopic electromagnetic perturbations in general magnetic field configurations is developed in this paper.
Nonlinear gyrokinetic equations for low-frequency electromagnetic waves in general plasma equilibria
E. A. Frieman,Liu Chen +1 more
TL;DR: A nonlinear gyrokinetic formalism for low-frequency (less than the cyclotron frequency) microscopic electromagnetic perturbations in general magnetic field configurations is developed in this paper.