Anomalous tungsten transport driven by ion temperature gradient turbulence

2021 ◽  
Author(s):  
Shaokang Xu ◽  
Shinya Maeyama ◽  
Tomohiko Watanabe
Keyword(s):  
Particle Transport ◽  
Large Scale ◽  
Critical Density ◽  
Small Scale ◽  
Particle Diffusion ◽  
Tungsten Particle ◽  
Ion Temperature ◽  
Nonlinear Excitation ◽  
Ion Temperature Gradient ◽  
Gyrokinetic Simulations

Abstract The present study reveals that the anomalous tungsten particle transport based on the nonlinear gyrokinetic simulations shares some similarities with that of the linear gyrokinetic study, meanwhile there exist some significant differences. In particular, nonlinear excitation of the linearly stable modes plays a non-negligible role in anomalous tungsten particle transport. The highlighted results are the downshift of the critical density gradient for zero tungsten particle transport and the mod- ification of the poloidal profile of the outward tungsten particle transport, which are both related to the small scale turbulent fluctuations. The former one is due to the outward particle convection produced by the linearly stable modes. The later one is brought by both the linearly stable modes and the large-scale eddies with finite ballooning angle, which flatten the poloidal profile of the particle diffusion and further shift the peak positions of the strongest outward particle transport to the high poloidal angle regions.

Phase space scales of free energy dissipation in gradient-driven gyrokinetic turbulence

2014 ◽  
Vol 80 (4) ◽  
pp. 531-551 ◽  
Author(s):  
D. R. Hatch ◽  
F. Jenko ◽  
V. Bratanov ◽  
A. Bañón Navarro
Keyword(s):  
Free Energy ◽  
Phase Space ◽  
Energy Dissipation ◽  
Large Scale ◽  
Hermite Polynomials ◽  
Small Scale ◽  
Ion Temperature ◽  
Astrophysical Plasmas ◽  
Ion Temperature Gradient ◽  
Eddy Simulation

A reduced four-dimensional (integrated over perpendicular velocity) gyrokinetic model of slab ion temperature gradient-driven turbulence is used to study the phase-space scales of free energy dissipation in a turbulent kinetic system over a broad range of background gradients and collision frequencies. Parallel velocity is expressed in terms of Hermite polynomials, allowing for a detailed study of the scales of free energy dynamics over the four-dimensional phase space. A fully spectral code – the DNA code – that solves this system is described. Hermite free energy spectra are significantly steeper than would be expected linearly, causing collisional dissipation to peak at large scales in velocity space even for arbitrarily small collisionality. A key cause of the steep Hermite spectra is acritical balance– an equilibration of the parallel streaming time and the nonlinear correlation time – that extends to high Hermite numbern. Although dissipation always peaks at large scales in all phase space dimensions, small-scale dissipation becomes important in an integrated sense when collisionality is low enough and/or nonlinear energy transfer is strong enough. Toroidal full-gyrokinetic simulations using theGenecode are used to verify results from the reduced model. Collision frequencies typically found in present-day experiments correspond to turbulence regimes slightly favoring large-scale dissipation, while turbulence in low-collisionality systems like ITER and space and astrophysical plasmas is expected to rely increasingly on small-scale dissipation mechanisms. This work is expected to inform gyrokinetic reduced modeling efforts like Large Eddy Simulation and gyrofluid techniques.

scholarly journals Gyrokinetic simulations of electric current generation in ion temperature gradient driven turbulence

2021 ◽  
Vol 28 (11) ◽  
pp. 112303
Author(s):  
Xiang Chen ◽  
Zhixin Lu ◽  
Huishan Cai ◽  
Lei Ye ◽  
Yang Chen ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Electric Current ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Current Generation ◽  
Gyrokinetic Simulations

Coherent drift-wave structures in toroidal plasmas

1996 ◽  
Vol 56 (3) ◽  
pp. 605-613 ◽  
Author(s):  
W. Horton ◽  
T. Tajima ◽  
J.-Y. Kim ◽  
Y. Kishimoto ◽  
M. Ottaviani
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Marginal Stability ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Toroidal Plasmas ◽  
Convective Structures ◽  
Drift Wave ◽  
Particle Simulations ◽  
Two Phases

Using the ion-temperature-gradient-driven drift waves as a paradigm for drift-wave anomalous transport, we explore the structure of the linear and nonlinear modes. Two phases of transport are shown to exist: (i) Bohm-like transport for parameters close to marginal stability; (ii) gyro-Bohm transport for turbulent convection cells in systems driven away from marginal stability. Nonlinear relaxation to large-scale coherent convective structures is observed in three-dimensional toroidal particle simulations.

Gyrokinetic simulations of E×B velocity‐shear effects on ion‐temperature‐gradient modes

1993 ◽  
Vol 5 (8) ◽  
pp. 2967-2980 ◽  
Author(s):  
Bruce I. Cohen ◽  
Timothy J. Williams ◽  
Andris M. Dimits ◽  
Jack A. Byers
Keyword(s):  
Temperature Gradient ◽  
Velocity Shear ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Shear Effects ◽  
Gyrokinetic Simulations

scholarly journals Random forcing with a constant power input for two-dimensional gyrokinetic simulations

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Ryusuke Numata
Keyword(s):  
Large Scale ◽  
Scaling Laws ◽  
Power Input ◽  
Small Scale ◽  
Two Dimensional ◽  
Constant Power ◽  
Random Forcing ◽  
Constant Rate ◽  
Set Up ◽  
Gyrokinetic Simulations

A method of random forcing with a constant power input for two-dimensional gyrokinetic turbulence simulations is developed for the study of stationary plasma turbulence. The property that the forcing term injects the energy at a constant rate enables turbulence to be set up in the desired range and energy dissipation channels to be assessed quantitatively in a statistically steady state. Using the developed method, turbulence is demonstrated in the large-scale fluid and small-scale kinetic regimes, where the theoretically predicted scaling laws are reproduced successfully.

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