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

Albert Mollén (Institutionen för teknisk fysik, Nukleär teknik) ; Matt Landreman ; Håkan Smith ; Stefanie Braun ; Per Helander
Physics of Plasmas (1070-664X). Vol. 22 (2015), 11, p. 112508.
[Artikel, refereegranskad vetenskaplig]

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 also 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.

Nyckelord: stellarators, plasma impurities, transport, bootstrap current


http://arxiv.org/abs/1504.04810



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Denna post skapades 2015-11-30. Senast ändrad 2016-01-15.
CPL Pubid: 226634

 

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Institutioner (Chalmers)

Institutionen för teknisk fysik, Nukleär teknik (2006-2015)

Ämnesområden

Energi
Hållbar utveckling
Fusion
Plasmafysik med fusion

Chalmers infrastruktur