Speaker
Description
Plasma-wall interaction (PWI) is a key topic to be addressed for the safe operation of
nuclear fusion reactors. Non-hydrogenic species, like helium (He) produced by D-T
fusion reactions or argon (Ar) injected in tokamaks as a seeding impurity, need special
attention. Their large mass may enhance the erosion of plasma facing components
(PFCs), but they also increase radiation cooling, which instead tends to lower erosion;
moreover they may induce peculiar surface modifications on the material. On the
material side, tungsten (W) is the primary candidate to be investigated as a divertor
and first wall material due to its low sputtering yields and high melting point. Studying
full non-hydrogenic PWI may provide crucial information to understand relevant
physics phenomena and for code validation purposes. Experiments of this kind have
been conducted both in tokamaks and in linear plasma devices (LPDs), the latter being
dedicated testbeds to investigate PWI at ITER-relevant levels of particle fluxes and
fluences. In this framework, analytical and numerical models play a significant role in
supporting the experimental activities, aiding their interpretation and enhancing the
ability to extrapolate results to future experiments.
This work presents an overview of modelling activities related to non-hydrogenic PWI
experiments, both in a full W tokamak environment and in dedicated LPD W-samples
exposures, performed in ASDEX Upgrade (AUG) and in the GyM linear device [1]
respectively. The erosion and impurity transport code ERO2.0 [2] is employed to
simulate erosion, migration and deposition across the entire machine volume, thanks
to its coupling with the boundary plasma code SOLPS-ITER [3].
Based on previous modelling works [4,5], the results presented relative to the GyM
linear device focus on the recent advancements towards the validation of ERO2.0
global simulations with He and Ar plasmas. The modelling techniques adopted to
support the design of the experiments are illustrated, in terms of ideal diagnostic
location and different plasma-sample material configurations, in order to obtain better
experimental data for validation purposes. It was shown that catchers to measure
deposited layers provide higher deposition by being installed closer to the sampleholder in axial position and oriented towards it, whereas symmetric azimuthal
deposition is observed. W-samples installed in a Molybdenum (Mo) mask provided a
threefold higher deposition rate than a single larger W-sample without mask. Instead,
replacing W-samples with an easier to sputter material like chromium (Cr) provided the
highest deposition signal, around twice the W-samples and Mo-mask configuration.
The modelling is finally validated against experimental measurements.
On the AUG tokamak side, the results aim to present the erosion modelling of H-mode
He discharges, following previous work conducted on L-mode He discharges from the
same campaign*. Work is ongoing to evaluate the influence of different modelling
assumptions on outer divertor erosion and W transport. Moreover, a strategy for
erosion modelling in intra-ELM phases is being developed to evaluate differences with
the inter-ELM phase. Finally, results are compared to the L-mode modelling and to
experimental outer divertor erosion measurements.
Acknowledgements: Part of this work is funded by Eni S.p.A. This work has been
carried out within the framework of the EUROfusion Consortium (WP-PWIE), partially
funded by the European Union via the Euratom Research and Training Programme
(Grant Agreement No 101052200—EUROfusion).
[1] A. Uccello, et al. Front. Phys. 11, 1108175 (2023)
[2] J. Romazanov, et al., Phys. Scripta 2017.T170, 014018 (2017)
[3] X. Bonnin, et al, Plasma Fusion Res. 11, 1403102 (2016)
[4] F. Mombelli, et al., Nucl. Fusion 65, 026023 (2025)
[5] G. Alberti, et al., Nucl. Fusion 63.2, 026020 (2023)
*Manuscript in preparation
