Radially global<i>δ</i><i>f</i>computation of neoclassical phenomena in a tokamak pedestal

Landreman, Matt; Parra, Félix I.; Catto, Peter J.; Ernst, D. R.; Pusztai, István

doi:10.1088/0741-3335/56/4/045005

Cited by 14 publications

(40 citation statements)

References 60 publications

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“…SFINCS is also closely related to the radially global Fokker-Planck code for tokamaks described in Ref. [34]. Briefly, the kinetic equation is discretized using finite differences with a 5-point stencil in θ and ζ, using a truncated Legendre modal expansion in ξ, and using a spectral collocation method in x a .…”

Section: Numerical Implementationmentioning

confidence: 99%

Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas

et al. 2014

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In this work, we examine the validity of several common simplifying assumptions used in numerical neoclassical calculations for nonaxisymmetric plasmas, both by using a new continuum drift-kinetic code and by considering analytic properties of the kinetic equation. First, neoclassical phenomena are computed for the LHD and W7-X stellarators using several versions of the drift-kinetic equation, including the commonly used incompressible-E × B-drift approximation and two other variants, corresponding to different effective particle trajectories. It is found that for electric fields below roughly one third of the resonant value, the different formulations give nearly identical results, demonstrating the incompressible E ×B-drift approximation is quite accurate in this regime. However, near the electric field resonance, the models yield substantially different results. We also compare results for various collision operators, including the full linearized Fokker-Planck operator. At low collisionality, the radial transport driven by radial gradients is nearly identical for the different operators, while in other cases it is found to be important that collisions conserve momentum.

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Section: Numerical Implementationmentioning

confidence: 99%

Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas

et al. 2014

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“…In particular, the difference contains the term en i, pol V i,‖ , where the ion polarization charge density en i, pol corresponds to the LHS of Equation (4), V i, ‖ = b ⋅V i , and V i is the ion flow velocity. The contribution from this term, if retained in Equation (5), would include the term (V i,‖ ⋅ ‖ )en i, pol , which corresponds to the parallel-convection piece of the ion polarization current, J p = (c 2…”

Section: Simulation Modelmentioning

confidence: 99%

“…17 in the weakly collisional regime and k = −1.7 in the strongly collisional regime. Estimating the anomalous contribution to the flux-surface averaged perpendicular current as 2 , it follows that such a contribution should be retained provided…”

Section: Simulation Modelmentioning

confidence: 99%

Continuum kinetic modelling of cross‐separatrix plasma transport in a tokamak edge including self‐consistent electric fields

Dorf

Dorr

2018

Contributions to Plasma Physics

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Eulerian kinetic calculations are presented for the axisymmetric cross‐separatrix plasma transport at the edge of a tokamak. The simulations are performed with a high‐order finite volume code COGENT, which solves the long‐wavelength limit of the full‐f ion gyrokinetic equation including the non‐linear Fokker–Plank collision model. Self‐consistent 2D electrostatic potential variations are obtained from the quasi‐neutrality (∇·j = 0) equation coupled to an isothermal fluid electron response. Illustrative solutions presented for parameters characteristic of the DIII‐D tokamak show qualitative agreement with experimental data.

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“…In previous studies 27,33,40 , the global drift kinetic equation (1) has usually been solved together with the constraints d 3 vg = d 3 v v 2 g = 0, to obtain the radial dependence of two components of S, corresponding to particle and energy sources. However, S did not contribute to the angular momentum balance.…”

Section: Particle and Momentum Fluxesmentioning

confidence: 99%

Isotope and density profile effects on pedestal neoclassical transport

Buller¹,

Pusztai²

2017

Plasma Phys. Control. Fusion

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Cross-field neoclassical transport of heat, particles and momentum is studied in sharp density pedestals, with a focus on isotope and profile effects, using a radially global approach. Global effects -which tend to reduce the peak ion heat flux, and shift it outward -increase with isotope mass for fixed profiles. The heat flux reduction exhibits a saturation with a favorable isotopic trend. A significant part of the heat flux can be convective even in pure plasmas, unlike in the plasma core, and it is sensitive to how momentum sources are distributed between the various species. In particular, if only ion momentum sources are allowed, in global simulations of pure plasmas the ion particle flux remains close to its local value, while this may not be the case for simulations with isotope mixtures or electron momentum sources. The radial angular momentum transport that is a finite orbit width effect, is found to be strongly correlated with heat sources.

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Radially globalδfcomputation of neoclassical phenomena in a tokamak pedestal

Cited by 14 publications

References 60 publications

Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas

Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas

Continuum kinetic modelling of cross‐separatrix plasma transport in a tokamak edge including self‐consistent electric fields

Isotope and density profile effects on pedestal neoclassical transport

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