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

Wei, Xiyang; Wang, W.H.; Zhang, Lin; Choi, Gyungjin; Dettrick, Sean; Lau, Calvin; Liu, P.F.; Tajima, T.

doi:10.1088/1741-4326/ac3023

Cited by 3 publications

(2 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the future work, we will extend our current study towards a more realistic FRC profile and investigate the heat load problem in FRC SOL. For example, we need to incorporate the self-generated zonal flows [8], which could have similar suppression effects as equilibrium E × B sheared flows on the ITG instability in the FRC SOL [46]. We also need to include multiple toroidal modes, which could induce nonlinear mode coupling leading to inverse spectral cascade [13].…”

Section: Discussionmentioning

confidence: 99%

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

Wang

Bao

Wei

et al. 2021

Plasma Phys. Control. Fusion

Self Cite

View full text Add to dashboard Cite

Linear and nonlinear effects of the equilibrium radial electric field on the ion temperature gradient (ITG) instability in the scrape-off layer (SOL) of a field-reversed configuration have been studied using gyrokinetic particle simulations for a single toroidal mode. Linear simulations with adiabatic electrons find that the E × B flow shear reduces the growth rate and causes a radial tilting of the mode structure on the toroidal plane. Nonlinear simulations find that the E × B flow shear significantly decreases ITG saturation amplitude and ion heat transport in the SOL by reducing both turbulence intensity and eddy size. The turbulence intensity is determined by fluid eddy rotation, which is the dominant saturation mechanism for the SOL ITG instability with a single toroidal mode number. On the other hand, parallel wave-particle decorrelation is the dominant mechanism for the SOL ITG turbulent transport. A random walk model using the guiding center radial excursion as the characteristic length scale and the eddy turnover time as the characteristic time scale fits very well to the scaling of ion heat conductivity with the E × B flow shear.

show abstract

Section: Discussionmentioning

confidence: 99%

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

Wang

Bao

Wei

et al. 2021

Plasma Phys. Control. Fusion

Self Cite

View full text Add to dashboard Cite

show abstract

“…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]. See [27] in these proceedings for more details.…”

Section: Perpendicular Transportmentioning

confidence: 99%

Simulation of equilibrium and transport in advanced FRCS

Dettrick¹,

Barnes²,

Ceccherini³

et al. 2021

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

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.

show abstract

A gyrokinetic simulation model for 2D equilibrium potential in the scrape-off layer of a field-reversed configuration

Wang,

Wei,

Lin

et al. 2024

Physics of Plasmas

View full text Add to dashboard Cite

The equilibrium potential structure in the scrape-off layer (SOL) of the field-reversed configuration (FRC) can be affected by the penetration of edge biasing applied at the divertor ends. The primary focus of the paper is to establish a formulation that accurately captures both parallel and radial variations of the two-dimensional (2D) potential in SOL. The formulation mainly describes a quasi-neutral plasma with a logical sheath boundary. A full-f gyrokinetic ion model and a massless electron model are implemented in the GTC-X code to solve for the self-consistent equilibrium potential, given fixed radial potential profiles at the boundaries. The first essential point of this 2D model lies in its ability to couple radial and parallel dynamics stemming from resistive currents and drag force on ions. The model successfully recovers the fluid force balance and continuity equations. These collisional effects on 2D potential mainly appear through the density profile changes, modifying the potential through electron pressure gradient. This means an accurate prescription of electron density and temperature profiles is important in predicting the potential structure in the FRC SOL. The Debye sheath potential and the potential profiles applied at the boundaries can be additional factors contributing to the 2D variations in SOL. This comprehensive full-f scheme holds promise for future investigations into turbulent transport in the presence of the self-consistent 2D potential together with the non-Maxwellian distributions and open boundary conditions in the FRC SOL.

show abstract

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

Cited by 3 publications

References 39 publications

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

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

Simulation of equilibrium and transport in advanced FRCS

A gyrokinetic simulation model for 2D equilibrium potential in the scrape-off layer of a field-reversed configuration

Contact Info

Product

Resources

About