Speaker
Albert Viktor Mollén
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1094.pdf
Calculations of impurity transport in Wendelstein 7-X plasmas
A. Mollén1,†, M. Landreman2 , H. M. Smith1 , J. A. Alcusón1 , P. Xanthopoulos1 ,
J. M. García-Regaña3 , A. Iantchenko4 , S. Buller4 , A. Langenberg1 , P. Helander1
1 Max-Planck-Institut für Plasmaphysik, Greifswald, Germany
2 Institute for Research in Electronics and Applied Physics, University of Maryland, USA
3 Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain
4 Department of Physics, Chalmers University of Technology, Göteborg, Sweden
Collisional transport theory has traditionally predicted impurity accumulation in stellarators
driven by the inward pointing radial electric field, and impurities are a major concern for the
capability of stellarators as a fusion energy source. However, recent advances in analytical [1, 2]
and numerical [3, 4, 5] studies suggest that the standard neoclassical theory lack several effects
that can be crucial when analyzing the impurity transport, and perhaps the situation is less
severe than previously thought. Moreover, initial calculations of impurity transport in the first
experimental campaign of the Wendelstein 7-X stellarator indicate that neoclassical theory alone
is not capable of explaining the experimentally inferred results and particularly towards the
plasma edge turbulent transport can play an important role.
In the present work we perform a kinetic transport analysis of impurities in experimental
Wendelstein 7-X plasmas. To calculate the neoclassical transport we employ the SFINCS (Stel-
larator Fokker-Planck Iterative Neoclassical Conservative Solver) code [4, 6], which solves the
time-independent radially local linearized 4D drift-kinetic equation for the perturbed distri-
bution function and calculates fluxes. The code can account for flux-surface variations of the
electrostatic potential, the full linearized Fokker-Planck-Landau collision operator, tangential
magnetic drifts, an arbitrary number of kinetic species (including non-trace impurities), and it
can be run iteratively to find the ambipolar radial electric field. Neoclassical calculations are
supplemented by predictions of the turbulent impurity transport using the GENE code [7].
References
[1] P. Helander, et al., Phys. Rev. Lett. 118 (2017) 155002.
[2] I. Calvo, et al., Plasma Phys. Control. Fusion 59 (2017) 055014.
[3] J. M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004.
[4] A. Mollén, et al., submitted to Plasma Phys. Control. Fusion (2017).
[5] J. L. Velasco, et al., arXiv:1712.03872 (2017).
[6] M. Landreman, et al., Phys. Plasmas 21 (2014) 042503.
[7] F. Jenko, et al., Phys. Plasmas 7 (2000) 1904.
†
albert.mollen@ipp.mpg.de
