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Impurities cause radiation losses and plasma dilution, and in stellaratorplasmas the neoclassical ambipolar radial electric field is often unfavorablefor avoiding strong impurity peaking. In this work we use a new continuumdrift-kinetic solver, the SFINCS code (the Stellarator Fokker-Planck IterativeNeoclassical Conservative Solver) [M. Landreman et al., Phys. Plasmas 21 (2014)042503] which employs the full linearized Fokker-Planck-Landau operator, tocalculate neoclassical impurity transport coefficients for a Wendelstein 7-X(W7-X) magnetic configuration. We compare SFINCS calculations with theoreticalasymptotes in the high collisionality limit. We observe and explain a1/nu-scaling of the inter-species radial transport coefficient at lowcollisionality, arising due to the field term in the inter-species collisionoperator, and which is not found with simplified collision models even whenmomentum correction is applied. However, this type of scaling disappears if aradial electric field is present. We also use SFINCS to analyze how theimpurity content affects the neoclassical impurity dynamics and the bootstrapcurrent. We show that a change in plasma effective charge Zeff of order unitycan affect the bootstrap current enough to cause a deviation in the divertorstrike point locations.

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