Tungsten erosion and scrape-off layer transport modelling in L-mode helium plasma discharges in ASDEX Upgrade

G. Alberti; E. Tonello; C. Tuccari; F. Mombelli; S. Brezinsek; T. Dittmar; A. Hakola; A. Kirschner; K. Krieger; M. Rasinski; J. Romazanov; A. Uccello; A. Widdowson; M. Passoni; the ASDEX Upgrade Team; the EUROfusion Tokamak Exploitation Team

arXiv · 2506.03883

Tungsten erosion and scrape-off layer transport modelling in L-mode helium plasma discharges in ASDEX Upgrade

G. Alberti·E. Tonello·C. Tuccari·F. Mombelli·S. Brezinsek·T. Dittmar·A. Hakola·A. Kirschner·K. Krieger·M. Rasinski·J. Romazanov·A. Uccello·A. Widdowson·M. Passoni·the ASDEX Upgrade Team·the EUROfusion Tokamak Exploitation Team

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Abstract

Due to its unavoidable presence in thermonuclear DT plasmas and to its peculiar effects on materials, investigating the role of helium (He) in plasma-wall interaction (PWI) in current tokamaks is fundamental. In this work, PWI in L-mode He plasma discharges in ASDEX Upgrade (AUG) is modelled by exploiting simplified analytical approaches and two state-of-the-art codes. SOLPS-ITER is employed both to provide a suitable background plasma for erosion simulations and to interpret diagnostics measurements in terms of He+/2+ fraction. In particular, a 50-50% concentration of the two He ions is found in the proximity of the strike-points, while He2+ represents the dominant population farther in the scrape-off layer (SOL). The role of He ion fraction on AUG tungsten divertor erosion is first estimated by means of a simple analytical model and, afterwards, by exploiting ERO2.0, showing the major impact of He2+ in common AUG plasma temperatures. ERO2.0 findings are also compared with experimental erosion data in the strike-point region, showing the possible impact of extrinsic impurities on divertor erosion. Finally, the multi-fluid and kinetic approaches employed in this work to simulate W erosion and migration are compared, including W also in SOLPS-ITER modelling. The impact of target boundary conditions on the W source in SOLPS-ITER is investigated, in order to find a good agreement with ERO2.0 estimation. Then, W migration in the two codes is compared, showing a stronger W transport towards the X-point in ERO2.0 compared to present SOLPS-ITER simulations with no drifts. Similar W influx in core could be achieved by reducing anomalous diffusivity in ERO2.0.

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G. Alberti, E. Tonello, C. Tuccari, F. Mombelli, S. Brezinsek, T. Dittmar, A. Hakola, A. Kirschner, K. Krieger, M. Rasinski, J. Romazanov, A. Uccello, A. Widdowson, M. Passoni, the ASDEX Upgrade Team, the EUROfusion Tokamak Exploitation Team. 2025-06-04. Tungsten erosion and scrape-off layer transport modelling in L-mode helium plasma discharges in ASDEX Upgrade. https://arxiv.org/abs/2506.03883

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