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Study of up–down poloidal density asymmetry of high-$Z$ impurities with the new impurity version of XGCa

Part of: Focus on Fusion

Published online by Cambridge University Press:  17 October 2019

J. Dominski Open the ORCID record for J. Dominski [Opens in a new window] ,
C. S. Chang Open the ORCID record for C. S. Chang [Opens in a new window] ,
R. Hager Open the ORCID record for R. Hager [Opens in a new window] ,
P. Helander Open the ORCID record for P. Helander [Opens in a new window] ,
S. Ku Open the ORCID record for S. Ku [Opens in a new window]  and
E. S. Yoon
J. Dominski*
Affiliation:
Princeton Plasma Physics Laboratory, 100 Stellarator rd, Princeton, NJ 08540, USA
C. S. Chang
Affiliation:
Princeton Plasma Physics Laboratory, 100 Stellarator rd, Princeton, NJ 08540, USA
R. Hager
Affiliation:
Princeton Plasma Physics Laboratory, 100 Stellarator rd, Princeton, NJ 08540, USA
P. Helander
Affiliation:
Max-Planck-Institut für Plasmaphysik, Greifswald, Germany
S. Ku
Affiliation:
Princeton Plasma Physics Laboratory, 100 Stellarator rd, Princeton, NJ 08540, USA
E. S. Yoon
Affiliation:
Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
*
†Email address for correspondence: jdominsk@pppl.gov
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Abstract

Addition of multispecies impurity ions to the total-f gyrokinetic particle-in-cell code XGCa is reported, including a cross-verification of neoclassical physics against the NEO code. This new version of the neoclassical gyrokinetic code XGCa is used to benchmark and confirm the previous reduced-equation-based prediction that high-$Z$ impurity particles in the Pfirsch–Schlüter regime can exhibit a significant level of up–down poloidal asymmetry, through the large parallel friction force, and thus influence the radial plasma transport significantly. The study is performed in a plasma with weak toroidal rotation. In comparison, when the impurity particles are in the plateau regime, the up–down poloidal asymmetry becomes weak, with the parallel friction force becoming weaker than the parallel viscous force. It is also found that the linearization of the perturbed distribution function, based on the small poloidal asymmetry assumption, can become invalid. Using the numerical data from XGCa, each term in the parallel fluid force-balance equation have been analysed to find that both the main ions and the electrons respond to the poloidal potential variation adiabatically when the high-$Z$ tungsten possesses large poloidal variation.

Keywords

fusion plasmaplasma simulation
Type
Research Article
Information
Journal of Plasma Physics , Volume 85 , Issue 5 , October 2019 , 905850510
Copyright
© Cambridge University Press 2019 

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