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:10.1088/1741-4326/ac5b8a

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

Abstract

We report that ion orbit loss is considered important for generating the radially inward electric field E_r 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 E_r 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 E_r 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 E_r is found to be only mild.

Authors:

^[1];

^[1]; Hager, R. ^[1]; Ku, S. ^[1]; Chang, C. S. ^[1]

Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Publication Date:: Tue Apr 05 00:00:00 EDT 2022

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

Sponsoring Org.:: USDOE Office of Science (SC); SciDAC-4

OSTI Identifier:: 1856202

Grant/Contract Number:: AC02-09CH11466; AC02-05CH11231

Resource Type:: Accepted Manuscript

Journal Name:: Nuclear Fusion

Additional Journal Information:: Journal Volume: 62; Journal Issue: 6; Journal ID: ISSN 0029-5515

Publisher:: IOP Science

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; magnetic confinement fusion; ion orbit loss; gyrokinetic simulations; radial electric field

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:10.1088/1741-4326/ac5b8a.

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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.  https://doi.org/10.1088/1741-4326/ac5b8a

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                    Zhu, Hongxuan, Stoltzfus-Dueck, T., Hager, R., Ku, S., and Chang, C. S. Tue .  
"Effects of collisional ion orbit loss on neoclassical tokamak radial electric fields".  United States.  https://doi.org/10.1088/1741-4326/ac5b8a.  https://www.osti.gov/servlets/purl/1856202.

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@article{osti_1856202,

  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 = {We report that 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          = {10.1088/1741-4326/ac5b8a},

  journal      = {Nuclear Fusion},

  number       = 6,

  volume       = 62,

  place        = {United States},

  year         = {Tue Apr 05 00:00:00 EDT 2022},

  month        = {Tue Apr 05 00:00:00 EDT 2022}

}

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Works referenced in this record:

Momentum flux parasitic to free-energy transfer
journal, July 2017

Stoltzfus-Dueck, T.; Scott, B.
Nuclear Fusion, Vol. 57, Issue 8
DOI: 10.1088/1741-4326/aa7289

X-transport: A baseline nonambipolar transport in a diverted tokamak plasma edge
journal, September 2002

Chang, C. S.; Kue, Seunghoe; Weitzner, H.
Physics of Plasmas, Vol. 9, Issue 9
DOI: 10.1063/1.1490348

Constructing a new predictive scaling formula for ITER's divertor heat-load width informed by a simulation-anchored machine learning
journal, February 2021

Chang, C. S.; Ku, S.; Hager, R.
Physics of Plasmas, Vol. 28, Issue 2
DOI: 10.1063/5.0027637

Intrinsic momentum generation by a combined neoclassical and turbulence mechanism in diverted DIII-D plasma edge
journal, September 2014

Seo, Janghoon; Chang, C. S.; Ku, S.
Physics of Plasmas, Vol. 21, Issue 9
DOI: 10.1063/1.4894242