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A. Kirschner, D. Tskhakaya, S. Brezinsek, D. Borodin, J. Romazanov, R. Ding, A. Eksaeva, C. Linsmeier:
"Modelling of plasma-wall interaction and impurity transport in fusion devices and prompt deposition of tungsten as application";
Plasma Physics and Controlled Fusion, 60 (2017), 01404101; 01404112.

Main processes of plasma-wall interaction and impurity transport in fusion devices and their
impact on the availability of the devices are presented and modelling tools, in particular the
three-dimensional Monte-Carlo code ERO, are introduced. The capability of ERO is
demonstrated on the example of tungsten erosion and deposition modelling. The dependence of
tungsten deposition on plasma temperature and density is studied by simulations with a
simplified geometry assuming (almost) constant plasma parameters. The amount of deposition
increases with increasing electron temperature and density. Up to 100% of eroded tungsten can
be promptly deposited near to the location of erosion at very high densities (∼1 × 1014 cm−3
expected e.g. in the divertor of ITER). The effect of the sheath characteristics on tungsten prompt
deposition is investigated by using particle-in-cell (PIC) simulations to spatially resolve the
plasma parameters inside the sheath. Applying PIC data instead of non-resolved sheath leads in
general to smaller tungsten deposition, which is mainly due to a density and temperature
decrease towards the surface within the sheath. Two-dimensional tungsten erosion/deposition
simulations, assuming symmetry in toroidal direction but poloidally spatially varying plasma
parameter profiles, have been carried out for the JET divertor. The simulations reveal, similar to
experimental findings, that tungsten gross erosion is dominated in H-mode plasmas by the intra-
ELM phases. However, due to deposition, the net tungsten erosion can be similar within intraand
inter-ELM phases if the inter-ELM electron temperature is high enough. Also, the simulated
deposition fraction of about 84% in between ELMs is in line with spectroscopic observations
from which a lower limit of 50% has been estimated.

plasma-wall interaction, erosion, prompt deposition, tungsten, ERO, JET