On the applicability of the standard approaches for evaluating a neoclassical radial electric field in a tokamak edge region

The use of the standard approaches for evaluating a neoclassical radial electric field E{sub r}, i.e., the Ampere (or gyro-Poisson) equation, requires accurate calculation of the difference between the gyroaveraged electron and ion particle fluxes (or densities). In the core of a tokamak, the nontri...

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Bibliographic Details
Published in:Physics of plasmas 2013-08, Vol.20 (8)
Main Authors: Dorf, M. A., Cohen, R. H., Joseph, I., Simakov, A. N.
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CHARGE EXCHANGE
COLLISIONS
CORRECTIONS
ELECTRIC FIELDS
NEOCLASSICAL TRANSPORT THEORY
PLASMA
PLASMA CONFINEMENT
POISSON EQUATION
TOKAMAK DEVICES
WAVELENGTHS
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Summary:The use of the standard approaches for evaluating a neoclassical radial electric field E{sub r}, i.e., the Ampere (or gyro-Poisson) equation, requires accurate calculation of the difference between the gyroaveraged electron and ion particle fluxes (or densities). In the core of a tokamak, the nontrivial difference appears only in high-order corrections to a local Maxwellian distribution due to the intrinsic ambipolarity of particle transport. The evaluation of such high-order corrections may be inconsistent with the accuracy of the standard long wavelength gyrokinetic equation (GKE), thus imposing limitations on the applicability of the standard approaches. However, in the edge of a tokamak, charge-exchange collisions with neutrals and prompt ion orbit losses can drive non-intrinsically ambipolar particle fluxes for which a nontrivial (E{sub r}-dependent) difference between the electron and ion fluxes appears already in a low order and can be accurately predicted by the long wavelength GKE. The parameter regimes, where the radial electric field dynamics in the tokamak edge region is dominated by the non-intrinsically ambipolar processes, thus allowing for the use of the standard approaches, are discussed.
ISSN:1070-664X
1089-7674