Göttingen 2025 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 22: Plasma Wall Interaction/HEPP
P 22.1: Hauptvortrag
Donnerstag, 3. April 2025, 16:15–16:45, ZHG102
High-resolution optical emission spectroscopy of neutral W lines: comparing near-threshold sputtering of W with different crystal orientation in PSI-2 — •Marc Sackers1, Oleksandr Marchuk1, Stephan Ertmer1, Sebastijan Brezinsek1,2, Fredric Granberg3, and Arkadi Kreter1 — 1Forschungszentrum Jülich GmbH, Institute of Fusion Energy & Nuclear Waste Management - Plasma Physics — 2HHU Düsseldorf, Faculty of Mathematics and Natural Sciences — 3University of Helsinki, Department of Physics
Seeding gas ions, like Ar, having a kinetic energy of ≈ 100 eV, dominate the erosion of the plasma-wetted areas during the quiet phases of the discharges in fusion reactors. These ions create near-threshold sputtering. Thus, the collisional cascade stays within the surface layers, and the distribution function of the sputtered atoms can depend strongly on the crystallographic structure. Molecular dynamics simulations suggest precisely such a behavior for the erosion of W by low-energy Ar ions.
However, experimental studies of the near-threshold erosion of tungsten by seeding gas impurities are severely lacking. This contribution presents near-threshold erosion experiments of tungsten samples by Ar ion bombardment at the linear plasma device PSI-2. The modeling of the line shape emitted by sputtered W provides, via Doppler broadening, insights into the angular and velocity distribution functions. This contribution presents how to account for all relevant line broadening and splitting mechanisms. Notably, the line shape measured depends strongly on the crystallographic plane exposed to the plasma.
Keywords: Tungsten; Erosion; Spectral line shape; Low-density plasma; Nuclear fusion