Impurities in a non-axisymmetric plasma. Transport and effect on bootstrap current

Mollén, A.; Landreman, M.; Smith, H. M.; Braun, S.; Helander, P.

doi:10.1063/1.4935901

Title: Impurities in a non-axisymmetric plasma. Transport and effect on bootstrap current

Journal Article · Fri Nov 20 00:00:00 EST 2015 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4935901· OSTI ID:1227103

^[1];

^[2]; Smith, H. M. ^[3]; Braun, S. ^[4]; Helander, P. ^[3]

Chalmers Univ. of Technology, Goteborg (Sweden); Max-Planck-Institut fur Plasmaphysik, Greifswald (Germany)
Univ. of Maryland, College Park, MD (United States)
Max-Planck-Institut fur Plasmaphysik, Greifswald (Germany)
Max-Planck-Institut fur Plasmaphysik, Greifswald (Germany); Institute of Engineering Thermodynamics, Stuttgart (Germany)

Impurities cause radiation losses and plasma dilution, and in stellarator plasmas the neoclassical ambipolar radial electric field is often unfavorable for avoiding strong impurity peaking. In this work we use a new continuum drift-kinetic solver, the SFINCS code (the Stellarator Fokker-Planck Iterative Neoclassical Conservative Solver) [M. Landreman et al., Phys. Plasmas 21 (2014) 042503] which employs the full linearized Fokker-Planck-Landau operator, to calculate neoclassical impurity transport coefficients for a Wendelstein 7-X (W7-X) magnetic configuration. We compare SFINCS calculations with theoretical asymptotes in the high collisionality limit. We observe and explain a 1/nu-scaling of the inter-species radial transport coefficient at low collisionality, arising due to the field term in the inter-species collision operator, and which is not found with simplified collision models even when momentum correction is applied. However, this type of scaling disappears if a radial electric field is present. We use SFINCS to analyze how the impurity content affects the neoclassical impurity dynamics and the bootstrap current. We show that a change in plasma effective charge Z_eff of order unity can affect the bootstrap current enough to cause a deviation in the divertor strike point locations.

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Research Organization:: Univ. of Maryland, College Park, MD (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: FG02-93ER54197; AC02-05CH11231; DEFC0208ER54964; DEFG0293ER54197

OSTI ID:: 1227103

Alternate ID(s):: OSTI ID: 1226677

Journal Information:: Physics of Plasmas, Vol. 22, Issue 11; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 10 works

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Flux-surface variations of the electrostatic potential in stellarators: impact on the radial electric field and neoclassical impurity transport Mollén, A.; Landreman, M.; Smith, H. M. Plasma Physics and Controlled Fusion, Vol. 60, Issue 8 https://doi.org/10.1088/1361-6587/aac700	journal	June 2018
Impact of main ion pressure anisotropy on stellarator impurity transport Calvo, Iván; Parra, Félix I.; Velasco, José Luis Nuclear Fusion, Vol. 60, Issue 1 https://doi.org/10.1088/1741-4326/ab581f	journal	December 2019
The importance of the classical channel in the impurity transport of optimized stellarators Buller, S.; Mollén, A.; Newton, S. L. arXiv https://doi.org/10.48550/arxiv.1903.12511	text	January 2019
Impact of main ion pressure anisotropy on stellarator impurity transport Calvo, Ivan; Parra, Felix I.; Velasco, J. L. arXiv https://doi.org/10.48550/arxiv.1907.08482	text	January 2019

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