Intrinsic momentum generation by a combined neoclassical and turbulence mechanism in diverted DIII-D plasma edge

Seo, Joonho; Chang, C. S.; Ku, S.; Kwon, J.M.; Choe, Wonho; Müller, Stefan

doi:10.1063/1.4894242

Cited by 27 publications

(21 citation statements)

References 29 publications

(38 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other end, the global full-f approach includes both neoclassical and turbulent transport (these transport channels cannot be completely decoupled in a pedestal, in contrast to the local limit) and allows for strong deviations from local thermodynamic equilibrium. This approach requires nonlinear collision operators to fully live up to its promises 15 , and is currently numerically too expensive to be used for exploratory studies 16,17 . In this work, we use the global δf formalism 18 .…”

Section: Introductionmentioning

confidence: 99%

Global effects on neoclassical transport in the pedestal with impurities

Pusztai¹,

Buller²,

Landreman³

2016

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

We present a numerical study of collisional transport in a tokamak pedestal in the presence of non-trace impurities, using the radially global δf neoclassical solver Perfect [M. Plasma Phys. Control. Fusion 56 045005]. It is known that in a tokamak core with non-trace impurities present the radial impurity flux opposes the bulk ion flux to provide an ambipolar particle transport, with the electron transport being negligibly small. However, in a sharp density pedestal with sub-sonic ion flows the electron transport can be comparable to the ion and impurity flows. Furthermore, the neoclassical particle transport is not intrinsically ambipolar, and the non-ambipolarity of the fluxes extends outside the pedestal region by the radial coupling of the perturbations. The neoclassical momentum transport, which is finite in the presence of ion orbit-width scale profile variations, is significantly enhanced when impurities are present in non-trace quantities, even if the total parallel mass flow is dominated by the bulk ions.

show abstract

Section: Introductionmentioning

confidence: 99%

Global effects on neoclassical transport in the pedestal with impurities

Pusztai¹,

Buller²,

Landreman³

2016

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…This effect has been explained as due to thermal ion orbit loss [18,19] or neoclassical orbit effects coupled with orbit loss and turbulence [20]. The relation of this edge flow layer to global intrinsic rotation is still being investigated experimentally [17].…”

Section: Velocity Profile Considerationsmentioning

confidence: 99%

Dimensionless size scaling of intrinsic rotation in DIII-D

et al. 2016

View full text Add to dashboard Cite

A dimensionless empirical scaling for intrinsic toroidal rotation is given; M A~βN ρ *, where M A is the toroidal velocity divided by the Alfvén velocity, β N the usual normalized β value, and ρ* is the ion gyroradius divided by the minor radius. This scaling describes well experimental data from DIII-D, and also some published data from C-Mod and JET.The velocity used in this scaling is in an outer location in minor radius, outside of the interior core and inside of the large gradient edge region in H-mode conditions. This scaling establishes the basic magnitude of the intrinsic toroidal rotation and its relation to the rich variety of rotation profiles that can be realized for intrinsic conditions is discussed. This scaling has some similarities to existing dimensioned scalings, both the (2012)]. These relationships are described.

show abstract

“…Mach probe measurements of velocity peaking in DIII-D have spurred numerical simulations by deGrassie 27 and analytical modeling by Stacey 26 to characterize intrinsic rotation from thermal ion losses in the far edge region. Recent XGC0 simulations 30,31 have also supported the theory that ion orbit losses causing highly non-Maxwellian distribution functions greatly impact the radial electric field, which is closely linked to both diffusive and electromagnetic edge transport processes. Thus, it is desirable to develop improved ion orbit loss models which can be leveraged in existing momentum based predictive models for the radial electric field and its influence on the rest of the plasma, as exemplified in References 32 and 33. This paper extends the ion orbit loss model of References 24 and 8, to account for (1) prompt loss of fast neutral beam ions, (2) realistic flux surface geometry and magnetic fields, (3) return currents from the scrape off layer (SOL), (4) outward streaming lost particles that return to the plasma, and (5) x-transport and x-loss.…”

Section: Introductionmentioning

confidence: 74%

Improvements to an ion orbit loss calculation in the tokamak edge

Wilks

Stacey

2016

Physics of Plasmas

View full text Add to dashboard Cite

An existing model of collisionless particle, momentum, and energy ion orbit loss from the edge region of a diverted tokamak plasma has been extended. The extended ion orbit loss calculation now treats losses of both thermal ions and fast neutral beam injection ions and includes realistic flux surface and magnetic field representations, particles returning to the plasma from the scrape off layer, and treatment of x-transport and x-loss. More realistic flux surface geometry allows the intrinsic rotation calculation to predict a peaking in the profile closer to the separatrix, which is consistent with experiment; and particle tracking calculations reveal a new mechanism of "x-transport pumping," which predicts larger ion losses when coupling conventional ion orbit loss and x-loss mechanisms, though still dominated by conventional ion orbit loss. Sensitivity to these ion orbit loss model enhancements is illustrated by fluid predictions of neoclassical rotation velocities and radial electric field profiles, with and without the enhancements. Published by AIP Publishing.

show abstract

Intrinsic momentum generation by a combined neoclassical and turbulence mechanism in diverted DIII-D plasma edge

Cited by 27 publications

References 29 publications

Global effects on neoclassical transport in the pedestal with impurities

Global effects on neoclassical transport in the pedestal with impurities

Dimensionless size scaling of intrinsic rotation in DIII-D

Improvements to an ion orbit loss calculation in the tokamak edge

Contact Info

Product

Resources

About