Effects of equilibrium radial electric field on ion temperature gradient instability in the scrape-off layer of a field-reversed configuration

Wang, Wenhao; Bao, Jian; Wei, Xiyang; Zhang, Lin; Choi, Gyungjin; Dettrick, Sean; Kuley, Animesh; Lau, Calvin; Liu, Pengfei; Tajima, T.

doi:10.1088/1361-6587/abf403

Cited by 8 publications

(12 citation statements)

References 43 publications

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“…Subsequent global nonlinear simulations using the ANC code [12] find that linear ITG instability first grows in the SOL, and then the turbulence spreads from the SOL to the core, resulting in a steady state spectrum characterized by lower amplitude core fluctuations and larger SOL fluctuations consistent with experimental measurements [13]. Finally, nonlinear simulations using the GTC-X code [14] find that equilibrium E × B flow shear can reduce the ITG instability growth rate, saturation amplitude, and ion heat transport in the SOL by reducing both the turbulence intensity and eddy size [15]. The simulation results suggest that maximizing the radial shear of the Doppler-shifted local mode frequency can effectively suppress the ITG instability and associated transport in the FRC SOL.…”

Section: Introductionsupporting

confidence: 64%

Effects of zonal flows on ion temperature gradient instability in the scrape-off layer of a field-reversed configuration

Wei¹,

Wang²,

Zhang³

et al. 2021

Nucl. Fusion

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Gyrokinetic simulations of long wavelength ion temperature gradient (ITG) turbulence in the scrape-off layer (SOL) of a field-reversed configuration (FRC) find that zonal flows are nonlinearly generated and are the dominant mechanism for the nonlinear saturation of the ITG instability. After the ITG saturation, zonal flows remain undamped and gradually suppress the turbulent transport to a very low level. In the simulations with collisions, collisional damping gradually reduces zonal flow amplitude to a lower level, which allows finite ITG turbulence intensity and ion heat transport in the SOL. The steady state turbulence intensity and ion heat transport are found to be proportional to the collision frequency. This favorable scaling suggests that minimizing collisions (e.g. increasing temperature, reducing impurity content, etc) and preserving toroidal symmetry could improve plasma confinement in the FRC.

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Section: Introductionsupporting

confidence: 64%

Effects of zonal flows on ion temperature gradient instability in the scrape-off layer of a field-reversed configuration

Wei¹,

Wang²,

Zhang³

et al. 2021

Nucl. Fusion

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“…The case of a nonlinear radial electric field is a topic of great interest in the investigation of turbulence and transport in rotating magnetized plasmas [1-3, 8, 9] and was recently explored by Wang et al [11] in performing gyrokinetic studies of ion-temperature-gradient (ITG) turbulence and transport in the scrape-off layer (SOL) region of a field-reversed magnetized plasma.…”

Section: Discussionmentioning

confidence: 99%

“…which follows from Eqs. (11) and (21). We note that, since the equations ( 19)-(20) are linear in x and y, they can be arbitrarily normalized.…”

Section: A Normal-mode Analysismentioning

confidence: 96%

“…The importance of radial electric fields in rotating magnetized plasmas has been a topic of great interest for a few decades [1][2][3][4] because of the role of sheared E × B flows in the stabilization of turbulent magnetized plasmas. The guiding-center analysis for particle dynamics in the presence of background (equilibrium) radial electric fields [5,6], and its extension to the gyrokinetic analysis of turbulent magnetized plasmas [7][8][9][10][11], has also been a topic of great interest. The case of rotating magnetized plasmas due to the presence of radial electric fields continues to attract attention [12,13].…”

Section: Introductionmentioning

confidence: 99%

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Particle and guiding-center orbits in crossed electric and magnetic fields

Brizard¹

2023

Preprint

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The problem of the charged-particle motion in crossed electric and magnetic fields is investigated, and the validity of the guiding-center representation is assessed in comparison with the exact particle dynamics. While the magnetic field is considered to be straight and uniform, the (perpendicular) radial electric field is nonuniform. The Hamiltonian guiding-center theory of charged-particle motion is presented for arbitrary radial electric fields, and explicit examples are provided for the case of a linear radial electric field.

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“…χ e ∼ λ 2 corr τ eddy . In the SOL, GTC-X simulations find that equilibrium E × B flow shear significantly decreases ion temperature gradient (ITG) saturation amplitude and ion thermal transport by reducing both turbulence intensity and eddy size [25]. Further simulations find that the ion thermal transport decreases with lower collisional damping of the self-generated zonal flows, which have no collisionless damping in the ideal FRC [26].…”

Section: Perpendicular Transportmentioning

confidence: 93%

Simulation of equilibrium and transport in advanced FRCS

Dettrick¹,

Barnes²,

Ceccherini³

et al. 2021

Nucl. Fusion

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The advanced beam-driven FRC is a field reversed configuration (FRC) with the addition of neutral beam (NB) injection, electrode biasing, and magnetic expander divertors. The resulting configuration has novel features that make it necessary to revisit many key results in FRC theory. Three of these features include (i) a large energetic ion population, (ii) in-principle capability to adjust the electric field and rotation profiles, and (iii) a combination of magnetic and electrostatic confinement of electrons in the SOL. In some fueling scenarios the electron density profile may exhibit a significant peak outside of the separatrix. To explore these features a hybrid fluid/kinetic equilibrium model has been used to reconstruct typical experimental profiles of the C-2W experiment. Results indicate that the energetic ions provide at least 50% of the total plasma pressure. These equilibrium profiles have been used as initial conditions for global, cross-separatrix, turbulent transport simulations using the 3D electrostatic particle-in-cell code ANC. Electrostatic fluctuations were found to nonlinearly saturate at an amplitude which is an order magnitude lower than that observed previously. The tokamak turbulence code GTC code has also been extended to handle FRC physics in the new GTC-X version, which has been used to perform simulations of turbulent transport in the SOL relevant to electrode biasing. It is found that equilibrium E × B flow shear significantly decreases ion temperature gradient saturation amplitude and ion heat transport. Also in the SOL, a 1D2V continuum code has been developed and applied to parallel electron heat transport. Results show the formation of pre-sheath potential and reduction of parallel electron heat loss close to the ideal ambipolar limit, a result which has been validated by experimental diagnostics. These transport modifications caused by the three novel configuration features help to explain the remarkable plasma performance of the C-2W experiment.

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Effects of equilibrium radial electric field on ion temperature gradient instability in the scrape-off layer of a field-reversed configuration

Cited by 8 publications

References 43 publications

Effects of zonal flows on ion temperature gradient instability in the scrape-off layer of a field-reversed configuration

Effects of zonal flows on ion temperature gradient instability in the scrape-off layer of a field-reversed configuration

Particle and guiding-center orbits in crossed electric and magnetic fields

Simulation of equilibrium and transport in advanced FRCS

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