Impurities in a non-axisymmetric plasma. Transport and effect on bootstrap current
Abstract
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 Zeff of order unity can affect the bootstrap current enough to cause a deviation in the divertor strike point locations.
- Authors:
-
[1];
[2];
- 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)
- Publication Date:
- Research Org.:
- Univ. of Maryland, College Park, MD (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- OSTI Identifier:
- 1227103
- Alternate Identifier(s):
- OSTI ID: 1226677
- Grant/Contract Number:
- FG02-93ER54197; AC02-05CH11231; DEFC0208ER54964; DEFG0293ER54197
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Physics of Plasmas
- Additional Journal Information:
- Journal Volume: 22; Journal Issue: 11; Journal ID: ISSN 1070-664X
- Publisher:
- American Institute of Physics (AIP)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Stellarators; impurities; neoclassical transport; electric fields; plasma impurities; Fokker Planck equation; plasma transport properties
Citation Formats
Mollén, A., Landreman, M., Smith, H. M., Braun, S., and Helander, P. Impurities in a non-axisymmetric plasma. Transport and effect on bootstrap current. United States: N. p., 2015.
Web. doi:10.1063/1.4935901.
Mollén, A., Landreman, M., Smith, H. M., Braun, S., & Helander, P. Impurities in a non-axisymmetric plasma. Transport and effect on bootstrap current. United States. https://doi.org/10.1063/1.4935901
Mollén, A., Landreman, M., Smith, H. M., Braun, S., and Helander, P. Fri .
"Impurities in a non-axisymmetric plasma. Transport and effect on bootstrap current". United States. https://doi.org/10.1063/1.4935901. https://www.osti.gov/servlets/purl/1227103.
@article{osti_1227103,
title = {Impurities in a non-axisymmetric plasma. Transport and effect on bootstrap current},
author = {Mollén, A. and Landreman, M. and Smith, H. M. and Braun, S. and Helander, P.},
abstractNote = {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 Zeff of order unity can affect the bootstrap current enough to cause a deviation in the divertor strike point locations.},
doi = {10.1063/1.4935901},
journal = {Physics of Plasmas},
number = 11,
volume = 22,
place = {United States},
year = {Fri Nov 20 00:00:00 EST 2015},
month = {Fri Nov 20 00:00:00 EST 2015}
}
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