Kinetic effects on a tokamak pedestal ion flow, ion heat transport and bootstrap current

Catto, Peter J.; Parra, Félix I.; Kagan, Grigory; Parker, Jeffrey B.; Pusztai, István; Landreman, Matt

doi:10.1088/0741-3335/55/4/045009

Cited by 12 publications

(55 citation statements)

References 19 publications

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“…Already important simulation and theoretical work are forthcoming, focused on including the non-local transport effects caused by large gradients in the density and temperature 17,23,[44][45][46] .…”

Section: Discussionmentioning

confidence: 99%

Poloidal asymmetries in edge transport barriers

et al. 2015

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Measurements of impurities in Alcator C-Mod indicate that in the pedestal region, significant poloidal asymmetries can exist in the impurity density, ion temperature, and main ion density. In light of the observation that ion temperature and electrostatic potential are not constant on a flux surface [Theiler et al., Nucl. Fusion 54, 083017 (2014)], a technique based on total pressure conservation to align profiles measured at separate poloidal locations is presented and applied. Gyrokinetic neoclassical simulations with XGCa support the observed large poloidal variations in ion temperature and density, and that the total pressure is approximately constant on a flux surface. With the updated alignment technique, the observed in-out asymmetry in impurity density is reduced from previous publishing [Churchill et al., Nucl. Fusion 53, 122002 (2013)], but remains substantial (nz,H/nz,L∼6). Candidate asymmetry drivers are explored, showing that neither non-uniform impurity sources nor localized fluctuation-driven transport are able to explain satisfactorily the impurity density asymmetry. Since impurity density asymmetries are only present in plasmas with strong electron density gradients, and radial transport timescales become comparable to parallel transport timescales in the pedestal region, it is suggested that global transport effects relating to the strong electron density gradients in the pedestal are the main driver for the pedestal in-out impurity density asymmetry.

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Section: Discussionmentioning

confidence: 99%

Poloidal asymmetries in edge transport barriers

et al. 2015

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“…Several authors have investigated the global δf model analytically [19,[33][34][35][36][37][38]. However, little work has been done to compare the departures from conventional neoclassical results predicted by the aforementioned first-principles theories to direct numerical solution of the kinetic equation.…”

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confidence: 99%

Radially globalδfcomputation of neoclassical phenomena in a tokamak pedestal

Landreman

Parra

Catto

et al. 2014

Plasma Phys. Control. Fusion

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Conventional radially-local neoclassical calculations become inadequate if the radial gradient scale lengths of the H-mode pedestal become as small as the poloidal ion gyroradius. Here, we describe a radially global δf continuum code that generalizes neoclassical calculations to allow stronger gradients. As with conventional neoclassical calculations, the formulation is time-independent and requires only the solution of a single sparse linear system. We demonstrate precise agreement with an asymptotic analytic solution of the radially global kinetic equation in the appropriate limits of aspect ratio and collisionality. This agreement depends crucially on accurate treatment of finite orbit width effects.

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“…Physicists should give a definite answer. The discrepancy between Catto 6 and Shaing 5 comes from the trapped particle dynamics which is emphasized in this paper. Accurate banana width, bounce frequency, and the turning point position in the presence of the shear flow are presented.…”

Section: Introductionmentioning

confidence: 76%

“…The diffusivity scaling on the shear flow presented by Catto 6 and Shaing 5 are different. There are intense arguments 6 on this topic. It is important because it is related to the role of the shear flow in the thermal barrier.…”

Section: Introductionmentioning

confidence: 87%

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Diffusivity Scaling on Shear Flow

Wang¹,

He²,

Dong³

et al. 2014

AJMP

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Diffusivity scaling on shear flow is investigated. Radial electrical field is the drive of the flow. The turning points of the trapped particle are not on the drift surface, but modified by the radial electrical field. For the first time, an analytical expression of the banana width in presence of shear flow is accurately derived. The particle diffusivity given by Rosenbluth is reproduced but with the shear flow modification.

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Kinetic effects on a tokamak pedestal ion flow, ion heat transport and bootstrap current

Cited by 12 publications

References 19 publications

Poloidal asymmetries in edge transport barriers

Poloidal asymmetries in edge transport barriers

Radially globalδfcomputation of neoclassical phenomena in a tokamak pedestal

Diffusivity Scaling on Shear Flow

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