Impact of Geodesic Curvature on Zonal Flow Generation in Magnetically Conned Plasmas

Nakata, M.; Matsuoka, Seikichi

doi:10.1585/pfr.17.1203077

Cited by 3 publications

(4 citation statements)

References 14 publications

(10 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The zonal-flow effect significantly decreases with the geodesic curvature, whereas the scatter is large in the region of Z 1/2 /T < C 2 = 1.1 × 10 −2 . The dependence of the zonal-flow effect on the geodesic curvature is qualitatively consistent with the prediction of a numerical study, which investigated the geodesic curvature impact on the turbulent transport in the LHD configuration as well [13]. The zonal flow contribution with inwardly shifted configuration (R ax = 3.60 m) was also pointed out by a nonlinear gyrokinetic simulation [4].…”

Section: Evaluation Of Zonal Flow Effectsupporting

confidence: 84%

“…Therefore, turbulent transport level with the zonal flow can be calculated by only linear calculations. The zonal flow dependence on the geodesic curvature has been investigated with linear and nonlinear gyrokinetic simulations, in which the geodesic curvature was selectively modulated in the numerical simulations, and was verified for three different configurations such as the large helical device (LHD) NCSX-like, and axisymmetric configurations [13]. In tokamak geometry, the geodesic curvature tends to decrease with increasing elongation and increase with increasing triangularity [14].…”

Section: Introductionmentioning

confidence: 95%

“…However, it is difficult to include the zonal-flow effect on the turbulent transport because nonlinear calculation is necessary to evaluate the zonal-flow level, which is unsuitable for the configuration optimization study due to too high calculation costs. Recently, a nonlinear proxy model, in which the zonal flow is taken into account was proposed [13]. The zonal flow was modeled as a function of geodesic curvature of the magnetic field line κ g = κ • (∇ψ/|∇ψ|) × b, where κ was curvature of magnetic field defined as κ = b • ∇b, b was a unit vector along the magnetic field, and ψ was poloidal flux.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Experimental study of the effect of geodesic curvature on turbulent transport in magnetically confined plasma

Nishimoto,

Nagaoka,

Nakata

et al. 2024

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

An experimental study has demonstrated the impact of the geodesic curvature of the magnetic field line on turbulent ion-heat transport in magnetically confined plasma using the Large Helical Device (LHD). Statistical analyses with corrected Akaike Information Criterion (AICc) and multiple regression have revealed that the geodesic curvature indicates a dominant contribution to the ion-heat transport. Geodesic curvature dependence of the zonal-flow effect is evaluated by using a gyrokinetic-simulation-based reduced model. Then, the analysis implies a significant enhancement of the zonal-flow effect with a small geodesic curvature. These two independent analyses indicated the possibility of external zonal-flow control with the geodesic curvature of the magnetic field.

show abstract

Section: Evaluation Of Zonal Flow Effectsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experimental study of the effect of geodesic curvature on turbulent transport in magnetically confined plasma

Nishimoto,

Nagaoka,

Nakata

et al. 2024

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…[4][5][6] Plasma turbulence has been studied using gyrokinetics in both tokamak and stellarator geometry, where it has been found that the magnetic geometry can have a substantial influence on both the underlying microinstabilities 1,[7][8][9][10][11][12][13][14] and the transport levels in the saturated state. 8,12,13,[15][16][17] This is particularly true for the onset of TEMs, as the details of the magnetic geometry determine the locations of the magnetic minima and thus where trapped particles reside.…”

Section: Introductionmentioning

confidence: 99%

Influence of collisions on trapped-electron modes in tokamaks and low-shear stellarators

Morren,

Proll,

van Dijk

et al. 2024

Physics of Plasmas

View full text Add to dashboard Cite

The influence of collisions on the growth rate of trapped-electron modes (TEMs) in core plasmas is assessed through both analytical linear gyrokinetics and linear gyrokinetic simulations. Both methods are applied to the magnetic geometry of the DIII-D tokamak, as well as the Helically Symmetric eXperiment (HSX) and Wendelstein 7-X (W7-X) stellarators, in the absence of temperature gradients. Here we analytically investigate the influence of collisions on the TEM eigenmode frequency by a perturbative approach in the response of trapped particles to the mode, using an energy-dependent Krook operator to model collisions. Although the resulting growth rates exceed perturbative thresholds, they reveal important qualitative dependencies: a geometry-dependent stabilization rate occurs for all wavenumbers at high collisionality, while at low collisionality, a geometry-sensitive mixture of collisionless, resonantly driven, and collisionally destabilized modes is found. Additionally, linear gyrokinetic simulations have been performed with a rigorous pitch-angle scattering operator for the same geometries. In the case of DIII-D and large wavenumber modes in HSX, the trends predicted by analytical theory are reproduced. Dissimilarities are, however, obtained in W7-X geometry and for low wavenumber modes in HSX, which are shown to be due to a collision-induced transition to the Universal Instability as the dominant instability at marginal collisionality.

show abstract

A simplified model to estimate nonlinear turbulent transport by linear dynamics in plasma turbulence

Nakayama

Nakata

Honda

et al. 2023

Sci Rep

View full text Add to dashboard Cite

A simplified model to estimate nonlinear turbulent transport only by linear calculations is proposed, where the turbulent heat diffusivity in tokamak ion temperature gradient(ITG) driven turbulence is reproduced for a wide parameter range including near- and far-marginal ITG stability. The optimal nonlinear functional relation(NFR) between the turbulent diffusivity, the turbulence intensity $$\mathcal{T}$$ T , and the zonal-flow intensity $$\mathcal{Z}$$ Z is determined by means of mathematical optimization methods. Then, an extended modeling for $$\mathcal{T}$$ T and $$\mathcal{Z}$$ Z to incorporate the turbulence suppression effects and the temperature gradient dependence is carried out. The simplified transport model is expressed as a modified nonlinear function composed of the linear growth rate and the linear zonal-flow decay time. Good accuracy and wide applicability of the model are demonstrated, where the regression error of $$\sigma _{\textrm{model}} = 0.157$$ σ model = 0.157 indicates improvement by a factor of about 1/4 in comparison to that in the previous works.

show abstract

Impact of Geodesic Curvature on Zonal Flow Generation in Magnetically Conned Plasmas

Cited by 3 publications

References 14 publications

Experimental study of the effect of geodesic curvature on turbulent transport in magnetically confined plasma

Experimental study of the effect of geodesic curvature on turbulent transport in magnetically confined plasma

Influence of collisions on trapped-electron modes in tokamaks and low-shear stellarators

A simplified model to estimate nonlinear turbulent transport by linear dynamics in plasma turbulence

Contact Info

Product

Resources

About