Flow-shear stabilization of ion-temperature-gradient-driven instability in a linear machine

1994 ◽  
Vol 72 (1) ◽  
pp. 92-95 ◽  
Author(s):  
B. Song ◽  
A. K. Sen
Keyword(s):  
Temperature Gradient ◽  
Ion Temperature ◽  
Flow Shear ◽  
Ion Temperature Gradient ◽  
Linear Machine

scholarly journals Transition to subcritical turbulence in a tokamak plasma

2016 ◽  
Vol 82 (6) ◽  
Author(s):  
F. van Wyk ◽  
E. G. Highcock ◽  
A. A. Schekochihin ◽  
C. M. Roach ◽  
A. R. Field ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Initial Perturbation ◽  
Outer Core ◽  
Transition To Turbulence ◽  
Tokamak Plasma ◽  
Ion Temperature ◽  
Flow Shear ◽  
Ion Temperature Gradient ◽  
Stability Threshold ◽  
Accretion Flows

Tokamak turbulence, driven by the ion-temperature gradient and occurring in the presence of flow shear, is investigated by means of local, ion-scale, electrostatic gyrokinetic simulations (with both kinetic ions and electrons) of the conditions in the outer core of the Mega-Ampere Spherical Tokamak (MAST). A parameter scan in the local values of the ion-temperature gradient and flow shear is performed. It is demonstrated that the experimentally observed state is near the stability threshold and that this stability threshold is nonlinear: sheared turbulence is subcritical, i.e. the system is formally stable to small perturbations, but, given a large enough initial perturbation, it transitions to a turbulent state. A scenario for such a transition is proposed and supported by numerical results: close to threshold, the nonlinear saturated state and the associated anomalous heat transport are dominated by long-lived coherent structures, which drift across the domain, have finite amplitudes, but are not volume filling; as the system is taken away from the threshold into the more unstable regime, the number of these structures increases until they overlap and a more conventional chaotic state emerges. Whereas this appears to represent a new scenario for transition to turbulence in tokamak plasmas, it is reminiscent of the behaviour of other subcritically turbulent systems, e.g. pipe flows and Keplerian magnetorotational accretion flows.

Effects of flow shear on the ion temperature gradient modes in a high β plasma slab

2003 ◽  
Vol 10 (3) ◽  
pp. 774-781 ◽  
Author(s):  
Zhe Gao ◽  
J. Q. Dong ◽  
G. J. Liu ◽  
C. T. Ying
Keyword(s):  
Temperature Gradient ◽  
Ion Temperature ◽  
Flow Shear ◽  
Ion Temperature Gradient ◽  
Plasma Slab
Sign in / Sign up

Export Citation Format

Share Document