Speaker
Friedrich Schluck
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.1013.pdf
On the effects of kinetic minority ions on transport in Wendelstein 7-X
F. Schluck1 , M. Rack1 , D. Reiter1 , and Y. Feng2
1 Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik,
Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich, Germany
2 Max-Planck-Institute für Plasmaphysik, 17491 Greifswald / 85748 Garching, Germany
Three-dimensional transport modeling in the plasma edge region and in divertors is chal-
lenged, amongst others, by the typical hybrid kinetic–fluid character of multi-phase flows. In
most of the current edge plasma codes all ion components are typically described in a fluid
approximation. However, particularly for minority components, the life span of some of these
ions compared to local collisional relaxation times can be too short to meet the fluid constraint.
The three-dimensional edge transport code package EMC3-EIRENE [1,2] provides a unique
hybrid fluid–kinetic solution approach within a single, largely monolithic Monte-Carlo descrip-
tion. Hence, it is particularly well suited for an integrated hybrid treatment of the various neutral
and minority ion components in a (fluid) bath of electrons and main ions.
Recent results [3] have already highlighted significant ballistic effects when treating He+
ions kinetically, in He–He+ –He2+ edge plasma conditions typical for early limiter Wendelstein
7-X helium discharges. For the investigated conditions it turned out that the primary source of
singly charged helium is ionization of He, rather than recombination of He2+ . This is distinct
from approximations made in earlier 2D edge plasma simulations in which all He ion charge
states were treated with continuum approximations and strong mutual coupling assumptions
(e.g. a common temperature for all ion components).
We extend the rudimentary kinetic ion treatment within EIRENE with important features,
e.g. drift effects and pitch-angle scattering. With this enhancement, we revisit previous investi-
gations on helium operation in Wendelstein 7-X, as well as expand the impurity species study
with hydrogenic and carbon ions. Although we presently focus on stellarator physics, the ex-
panded kinetic ion transport strongly coupled to the neutral gas component can analogously
be applied to tokamak studies. We draw conclusions on transport features, and plasma profiles
and give an outlook on how the full three-dimensional EMC3-EIRENE code package is being
further developed into a useful and predictive tool for impurity studies for ITER.
References
[1] Y. Feng, et al., Journal of Nuclear Materials 266-269, 812-818 (1999)
[2] D. Reiter, et al., Journal of Nuclear Materials 220, 987-992 (1995)
[3] M. Rack, et al., Nuclear Fusion 57, 056011 (2017)
