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

Journal Article · Tue Aug 27 00:00:00 EDT 2013 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4818777· OSTI ID:1248311

Dorf, M. A. ^[1]; Cohen, R. H. ^[1]; Simakov, A. N. ^[2]; Joseph, I. ^[1]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

The use of the standard approaches for evaluating a neoclassical radial electric field E_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_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. As a result, 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.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1248311
• Report Number(s): LLNL-JRNL-609355; PHPAEN
• Journal Information: Physics of Plasmas, Vol. 20, Issue 8; ISSN 1070-664X
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION
tokamaks
electric fields
charge exchange reactions
Maxwell equations
orbital dynamics