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

Abstract

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.

9 pages, 11 figures, EPS Berlin Plasma Physics 2014, Invited speaker, submitted to Plasma Physics and Controlled Fusion

References in corpus (1)

• Neoclassical and gyrokinetic analysis of time-dependent helium transport experiments on MAST

Cited by in corpus (9)

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• The Dependence of the Impurity Transport on the Dominant Turbulent Regime in ELM-y H-mode Discharges
• Comparison between measured and predicted turbulence frequency spectra in ITG and TEM regimes
• Flux-driven integrated modelling of main ion pressure and trace tungsten transport in ASDEX Upgrade
• Numerical Implementation of the Improved Sugama Collision Operator Using a Moment Approach
• Neoclassical transport of tungsten ion bundles in total-f neoclassical gyrokinetic simulations of a whole-volume JET-like plasma
• Self-consistent gyrokinetic modelling of turbulent and neoclassical tungsten transport in toroidally rotating plasmas
• Partial-Ionization Deconfinement Effect in Magnetized Plasma
• Experimental Inference of Neutral and Impurity Transport in Alcator C-Mod Using High-Resolution X-Ray and Ultra-Violet Spectra