Effects of collisional ion orbit loss on neoclassical tokamak radial electric fields

Zhu, Hongxuan; Stoltzfus-Dueck, T; Hager, R; Ku, S; Chang, C S

doi:10.11578/1888260

Title: Effects of collisional ion orbit loss on neoclassical tokamak radial electric fields

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Abstract

Ion orbit loss is considered important for generating the radially inward electric field Er in a tokamak edge plasma. In particular, this effect is emphasized in diverted tokamaks with a magnetic X point. In neoclassical equilibria, Coulomb collisions can scatter ions onto loss orbits and generate a radially outward current, which in steady state is balanced by the radially inward current from viscosity. To quantitatively measure this loss-orbit current in an edge pedestal, an ion-orbit-flux diagnostic has been implemented in the axisymmetric version of the gyrokinetic particle-in-cell code XGC. As the first application of this diagnostic, a neoclassical DIII-D H-mode plasma is studied using gyrokinetic ions and adiabatic electrons. The validity of the diagnostic is demonstrated by studying the collisional relaxation of Er in the core. After this demonstration, the loss-orbit current is numerically measured in the edge pedestal in quasisteady state. In this plasma, it is found that the radial electric force on ions from Er approximately balances the ion radial pressure gradient in the edge pedestal, with the radial force from the plasma flow term being a minor component. The effect of orbit loss on Er is found to be only mild.

Authors:

Zhu, Hongxuan; Stoltzfus-Dueck, T; Hager, R; Ku, S; Chang, C S

Princeton Plasma Physics Laboratory

Publication Date:: Fri Mar 11 04:00:00 UTC 2022

DOE Contract Number:: AC02-05CH11231; AC02-09CH11466

Research Org.:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Org.:: USDOE Office of Science (SC)

Subject:: gyrokinetic simulations; ion orbit loss; radial electric field; tokamak edge plasmas

OSTI Identifier:: 1888260

DOI:: https://doi.org/10.11578/1888260

Citation Formats


                    Zhu, Hongxuan, Stoltzfus-Dueck, T, Hager, R, Ku, S, and Chang, C S. Effects of collisional ion orbit loss on neoclassical tokamak radial electric fields.  United States: N. p., 2022. 
        Web.  doi:10.11578/1888260.

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                    Zhu, Hongxuan, Stoltzfus-Dueck, T, Hager, R, Ku, S, & Chang, C S. Effects of collisional ion orbit loss on neoclassical tokamak radial electric fields.  United States.  doi:https://doi.org/10.11578/1888260

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                    Zhu, Hongxuan, Stoltzfus-Dueck, T, Hager, R, Ku, S, and Chang, C S. 2022.  
"Effects of collisional ion orbit loss on neoclassical tokamak radial electric fields".  United States.  doi:https://doi.org/10.11578/1888260.  https://www.osti.gov/servlets/purl/1888260. Pub date:Fri Mar 11 04:00:00 UTC 2022

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@article{osti_1888260,

  title        = {Effects of collisional ion orbit loss on neoclassical tokamak radial electric fields},

  author       = {Zhu, Hongxuan and Stoltzfus-Dueck, T and Hager, R and Ku, S and Chang, C S},

  abstractNote = {Ion orbit loss is considered important for generating the radially inward electric field Er in a tokamak edge plasma. In particular, this effect is emphasized in diverted tokamaks with a magnetic X point. In neoclassical equilibria, Coulomb collisions can scatter ions onto loss orbits and generate a radially outward current, which in steady state is balanced by the radially inward current from viscosity. To quantitatively measure this loss-orbit current in an edge pedestal, an ion-orbit-flux diagnostic has been implemented in the axisymmetric version of the gyrokinetic particle-in-cell code XGC. As the first application of this diagnostic, a neoclassical DIII-D H-mode plasma is studied using gyrokinetic ions and adiabatic electrons. The validity of the diagnostic is demonstrated by studying the collisional relaxation of Er in the core. After this demonstration, the loss-orbit current is numerically measured in the edge pedestal in quasisteady state. In this plasma, it is found that the radial electric force on ions from Er approximately balances the ion radial pressure gradient in the edge pedestal, with the radial force from the plasma flow term being a minor component. The effect of orbit loss on Er is found to be only mild.},

  doi          = {10.11578/1888260},

  journal      = {},

  number       = ,

  volume       = ,

  place        = {United States},

  year         = {Fri Mar 11 04:00:00 UTC 2022},

  month        = {Fri Mar 11 04:00:00 UTC 2022}

}

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DOI: https://doi.org/10.11578/1888260

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