Greifswald 2024 – scientific programme

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P: Fachverband Plasmaphysik

P 22: Plasma Wall Interaction II/HEPP VII

P 22.3: Talk

Thursday, February 29, 2024, 15:00–15:25, ELP 6: HS 4

Ion-driven deuterium permeation in tungsten-heavy-alloy-like multi-layer membranes — •Philipp Sand^1,2 and Armin Manhard¹ — ¹Max-Planck Institut für Plasmaphysik, 85748 Garching, Germany — ²Techn. Univ. München, 85748 Garching, Germany

Tungsten heavy alloy (97W-2Ni-1Fe, %wt., THA) is a possible candidate as plasma-facing material in future nuclear fusion devices. It exhibits a similar heat conductance at high temperature and sputter yield as pure W, whilst showing an improved ductility [1]. Hydrogen isotope (HI) retention behaviour [2] was also shown to be favourable, which was attributed to the microstructure of this dual phase material: Upon plasma loading, the percolating matrix phase provides fast diffusion paths to vacuum [3], while W domains remain at low HI concentrations due to a low HI solubility. To predict HI uptake of THA under reactor relevant conditions, the parameters of HI transport across respective phase boundaries must be quantified. An ion-driven permeation experiment was benchmarked using pure W samples irradiated with of 170 eV/D at 5x10¹⁹ D/m²s between 650 K and 900 K. D transport across the interface was studied at the same conditions in both directions using W substrates coated with matrix-like alloy on one side. The influence of surface oxides on permeation is investigated on both sides. It is confirmed that uptake from matrix into W is strongly suppressed while no significant barrier was observed for HI transport from W into matrix. [1] R. Neu, et al., Fusion Eng. Des. 124 (2017) 450-454, [2] H. Maier, et al., J. Nucl. Mater 18 (2019) 245-259, [3] A. Manhard, et al., Nucl. Mater 36 (2023) 101498

Keywords: Permeation; Retention; Tungsten heavy alloys; Interface transport; Surface oxides