Theoretical description of heavy impurity transport and its application to the modelling of tungsten in JET and ASDEX Upgrade

• Main Authors: Casson, F. J, Angioni, C, Belli, E. A, Bilato, R, Mantica, P, Odstrcil, T, Puetterich, T, Valisa, M, Garzotti, L, Giroud, C, Hobirk, J, Maggi, C. F, Mlynar, J, Reinke, M. L, contributors, JET EFDA, team, ASDEX-Upgrade
• Format: Journal Article
• Language: English
• Published: 04-07-2014
• Subjects: Physics - Plasma Physics
• DOI: 10.48550/arxiv.1407.1191

Plasma Phys. Control. Fusion 57 (2015) 014031 Recent developments in theory-based modelling of core heavy impurity
transport are presented, and shown to be necessary for quantitative description
of present experiments in JET and ASDEX Upgrade. The treatment of heavy
impurities is complicated by their large mass and charge, which result in a
strong response to plasma rotation or any small background electrostatic field
in the plasma, such as that generated by anisotropic external heating. These
forces lead to strong poloidal asymmetries of impurity density, which have
recently been added to numerical tools describing both neoclassical and
turbulent transport. Modelling predictions of the steady-state two-dimensional
tungsten impurity distribution are compared with experimental densities
interpreted from soft X-ray diagnostics. The modelling identifies neoclassical
transport enhanced by poloidal asymmetries as the dominant mechanism
responsible for tungsten accumulation in the central core of the plasma.
Depending on the bulk plasma profiles, neoclassical temperature screening can
prevent accumulation, and can be enhanced by externally heated species,
demonstrated here in ICRH plasmas.