Gyrokinetic particle-in-cell simulation of Alfvénic ion-temperature-gradient modes in tokamak plasma

2002 ◽  
Vol 9 (3) ◽  
pp. 861-868 ◽  
Author(s):  
Gang Zhao ◽  
Liu Chen
Keyword(s):  
Temperature Gradient ◽  
Tokamak Plasma ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Particle In Cell ◽  
Cell Simulation

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.

Low-frequency fluctuations in scrape-off layer of tokamak plasma with limiter biasing

2011 ◽  
Vol 77 (6) ◽  
pp. 733-748
Author(s):  
N. BISAI ◽  
RAMESWAR SINGH ◽  
R. SINGH
Keyword(s):  
Growth Rate ◽  
Temperature Gradient ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Tokamak Plasma ◽  
Equilibrium Density ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Electron Temperature Gradient ◽  
Field Mobility

AbstractThe effects of limiter biasing on the equilibrium density and potential profiles of the scrape-off layer (SOL) in tokamak plasma are investigated by including ionization and cross-field mobility. It is shown that a broadening of SOL can take place by the inclusion of ionization for low negative biasing. Various microinstabilities relevant for SOL plasmas have been studied. Generalized low-frequency dispersion relation is derived. It is shown that limiter biasing significantly modifies the SOL fluctuations. It is also shown that growth rate of conductive wall instability is smaller for negative biasing than positive biasing case. New mode, the modified Simon–Hoh, and ion temperature gradient instabilities are found to contribute significantly to the growth of curvature- and electron temperature-gradient-driven conductive wall instabilities.

Search for the ion temperature gradient mode in a tokamak plasma and comparison with theoretical predictions

2001 ◽  
Vol 8 (5) ◽  
pp. 2232-2237 ◽  
Author(s):  
C. L. Rettig ◽  
T. L. Rhodes ◽  
J. N. Leboeuf ◽  
W. A. Peebles ◽  
E. J. Doyle ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Tokamak Plasma ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Theoretical Predictions ◽  
Gradient Mode

scholarly journals Synergy between ion temperature gradient turbulence and neoclassical processes in global gyrokinetic particle-in-cell simulations

2012 ◽  
Vol 19 (4) ◽  
pp. 042301 ◽  
Author(s):  
T. Vernay ◽  
S. Brunner ◽  
L. Villard ◽  
B. F. McMillan ◽  
S. Jolliet ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Particle In Cell

Energy conservation in a nonlinear gyrokinetic particle-in-cell code for ion-temperature-gradient-driven modes in θ-pinch geometry

2002 ◽  
Vol 9 (3) ◽  
pp. 898-912 ◽  
Author(s):  
Roman Hatzky ◽  
Trach Minh Tran ◽  
Axel Könies ◽  
Ralf Kleiber ◽  
Simon J. Allfrey
Keyword(s):  
Temperature Gradient ◽  
Energy Conservation ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Particle In Cell
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