Gyrokinetic simulation of driftwave instability in field-reversed configuration

Fulton, Daniel; Lau, Calvin; Schmitz, L.; Holod, I.; Zhang, Lin; Tajima, T.; Binderbauer, Michl; Team, Tae

doi:10.1063/1.4948285

Cited by 14 publications

(14 citation statements)

References 28 publications

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“…Local linear simulations [11,12,13] using the gyrokinetic toroidal code (GTC) [14] have found qualitatively similar results. The SOL is linearly unstable for a wide range of length scales and varying pressure gradients.…”

Section: Introductionmentioning

confidence: 78%

Cross-separatrix simulations of turbulent transport in the field-reversed configuration

et al. 2019

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Recent local simulations of the field-reversed configuration (FRC) have reported drift-wave stability in the core and instability in the scrape-off layer (SOL). However, experimental measurements indicate the existence of fluctuations in both FRC core and SOL, with much lower amplitude fluctuations measured in the core. With the updated cross-separatrix capabilities of the simulation code used in this paper, nonlinear turbulence simulations find that linear instabilities grow in the SOL, generating fluctuations which spread from SOL to core. After saturation of the linear instabilities, a balance of the inward spread and local damping in the core is achieved. The steady state toroidal wavenumber spectrum shows lower amplitude core fluctuations and larger SOL fluctuations with amplitude decreasing towards shorter wavelengths, which are consistent with experimental measurements.

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Section: Introductionmentioning

confidence: 78%

Cross-separatrix simulations of turbulent transport in the field-reversed configuration

et al. 2019

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“…This observation is consistent with essentially classical ion thermal confinement, with the radial ion thermal diffusivity evaluated from 1-D and 2-D transport analysis19, where is the classical collisional ion thermal diffusivity. Finite ion Larmor radius (FLR) effects9101112 are found to contribute crucially to the observed stability of long wavelength modes, as confirmed by gyrokinetic stability calculations2021. The scrape-off layer (SOL) plasma is found to be unstable to multiscale drift-interchange modes (0.5< k θ ρ s ≤40, where ρ s is the ion sound Larmor radius , and ω ci is the ion cyclotron frequency, due to large radial density/temperature gradients in conjunction with the (moderate) field line curvature22.…”

mentioning

confidence: 84%

“…( a ) Normalized linear instability growth rate from an electrostatic flux tube calculation using the Gyrokinetic Toroidal Code (GTC)202135 of scrape-off layer (SOL) modes versus normalized toroidal wavenumber k θ ρ s . The simulation flux tube radius (at the axial midplane) is r / R s ∼1.3.…”

Section: Figurementioning

confidence: 99%

Suppressed ion-scale turbulence in a hot high-β plasma

et al. 2016

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An economic magnetic fusion reactor favours a high ratio of plasma kinetic pressure to magnetic pressure in a well-confined, hot plasma with low thermal losses across the confining magnetic field. Field-reversed configuration (FRC) plasmas are potentially attractive as a reactor concept, achieving high plasma pressure in a simple axisymmetric geometry. Here, we show that FRC plasmas have unique, beneficial microstability properties that differ from typical regimes in toroidal confinement devices. Ion-scale fluctuations are found to be absent or strongly suppressed in the plasma core, mainly due to the large FRC ion orbits, resulting in near-classical thermal ion confinement. In the surrounding boundary layer plasma, ion- and electron-scale turbulence is observed once a critical pressure gradient is exceeded. The critical gradient increases in the presence of sheared plasma flow induced via electrostatic biasing, opening the prospect of active boundary and transport control in view of reactor requirements.

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“…To fill this void in theoretical understanding, and, in support of ongoing experiments at TAE, we extend a mature, wellbenchmarked turbulence simulation code, the Gyrokinetic Toroidal Code (GTC), 38,39 to a system with C-2-like geometry and parameters. 35,40,41 The focus of this study is to find and characterize the linear properties of drift-waves in the FRC core and SOL separately using gyro-kinetic simulation.…”

Section: Introductionmentioning

confidence: 99%

Drift-wave stability in the field-reversed configuration

et al. 2017

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Gyrokinetic simulations of C-2-like field-reversed configuration (FRC) find that electrostatic driftwaves are locally stable in the core. The stabilization mechanisms include finite Larmor radius effects, magnetic well (negative grad-B), and fast electron short circuit effects. In the scrape-off layer (SOL), collisionless electrostatic drift-waves in the ion-to-electron-scale are destabilized by electron temperature gradients due to the resonance with locally barely trapped electrons. Collisions can suppress this instability, but a collisional drift-wave instability still exists at realistic pressure gradients. Simulation results are in qualitative agreement with C-2 FRC experiments. In particular, the lack of ion-scale instability in the core is not inconsistent with experimental measurements of a fluctuation spectrum showing a depression at ion-scales. The pressure gradient thresholds for the SOL instability from simulations are also consistent with the critical gradient behavior observed in experiments.

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Gyrokinetic simulation of driftwave instability in field-reversed configuration

Cited by 14 publications

References 28 publications

Cross-separatrix simulations of turbulent transport in the field-reversed configuration

Cross-separatrix simulations of turbulent transport in the field-reversed configuration

Suppressed ion-scale turbulence in a hot high-β plasma

Drift-wave stability in the field-reversed configuration

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