Gyrokinetic particle simulation of a field reversed configuration

Fulton, Daniel; Lau, Calvin; Holod, I.; Zhang, Lin; Dettrick, Sean

doi:10.1063/1.4930289

Cited by 14 publications

(16 citation statements)

References 68 publications

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“…FRC plasma equilibria produced with the LamyRidge code24 are first transformed from cylindrical coordinates to magnetic flux coordinates and further to Boozer coordinates. The modified GTC code has been extensively tested for convergence, as described in detail elsewhere20. Linear growth rate calculations based on local (flux tube) simulations ( k r << k θ ) are reported here.…”

Section: Resultsmentioning

confidence: 99%

“…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: 76%

“…( 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%

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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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Section: Resultsmentioning

confidence: 99%

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confidence: 76%

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

et al. 2016

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“…The observed strong SOL turbulence is ascribed to drift-or drift-interchange modes driven unstable by the radial density and/or temperature gradients, possibly in combination with unfavorable curvature in the open field line, mirror-confined SOL plasma region. Further experimental and modeling/simulation work is under way to identify unambiguously the underlying instability drive [36]. …”

Section: Discussionmentioning

confidence: 99%

Control of ion gyroscale fluctuations via electrostatic biasing and sheared E×B flow in the C-2 field reversed configuration

Schmitz¹,

Ruskov²,

Deng³

et al. 2016

AIP Conference Proceedings

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Abstract. Control of radial particle and thermal transport is instrumental for achieving and sustaining well-confined high-β plasma in a Field-Reversed Configuration (FRC). Radial profiles of low frequency ion gyro-scale density fluctuations (0.5 ≤ kρ s ≤ 40), consistent with drift-or drift-interchange modes, have been measured in the scrape-off layer (SOL) and core of the C-2 Field-Reversed Configuration (FRC), together with the toroidal ExB velocity. It is shown here that axial electrostatic SOL biasing controls and reduces gyro-scale density fluctuations, resulting in very low FRC core fluctuation levels. When the radial ExB flow shearing rate decreases below the turbulence decorrelation rate, fluctuation levels increase substantially, concomitantly with onset of the n=2 instability and rapid loss of diamagnetism. Low turbulence levels, improved energy/particle confinement and substantially increased FRC life times are achieved when ExB shear near the separatrix is maintained via axial SOL biasing using an annular washer gun.

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“…The value of b 0 averaged over the plasma volume is about 0.5-0.9, 7 where b 0 ¼ 2l 0 p=B 2 e is the ratio of plasma pressure to the external magnetic field pressure. The understanding of FRC transport has advanced considerably in the past 30 years; particle, 8,9 magnetic flux, and energy confinement 10 are well identified as anomalous; in other words, certain instabilities induce the turbulence which causes the anomalous transport in FRCs. In the beginning, the lower hybrid drift (LHD) instability, 11 which is electrostatic (dB ¼ 0) and flute like (k k ¼ 0) with wave numbers k $ 1=q e , was considered as the most linearly instable and studied in a lot of works.…”

Section: Introductionmentioning

confidence: 99%

Effect of collisions on drift instabilities in a field reversed configuration under conditions of magneto-inertial fusion

Wang

Yang

et al. 2017

Physics of Plasmas

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Drift instabilities in a field reversed configuration are studied under conditions of magneto-inertial fusion (MIF). Specifically, the collisional effect is taken into account because of high-density plasmas in MIF where the drift wave frequency is smaller than the electron-ion collision frequency. Dispersion relations are based on the two fluid equations including the collisional terms; meanwhile, the electromagnetic effect is also considered due to high b values (b is the ratio of plasma pressure to magnetic pressure). It is found that in the limit of low b, the behavior of instabilities described by the dispersion relations in the present paper would become like drift instabilities in tokamaks, where b $ 0.1. Therefore, in the MIF case, electromagnetic drift instabilities could be driven by electron-ion collisions due to the charge separation effect. The collisions also bring the phase difference between the perturbed density and the potential perturbation, which is significant for the particle transport. Published by AIP Publishing. [http://dx.

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Gyrokinetic particle simulation of a field reversed configuration

Cited by 14 publications

References 68 publications

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

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

Control of ion gyroscale fluctuations via electrostatic biasing and sheared E×B flow in the C-2 field reversed configuration

Effect of collisions on drift instabilities in a field reversed configuration under conditions of magneto-inertial fusion

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