Argon-seeded plasma exposure and oxidation performance of tungsten-chromium-yttrium smart alloys

Abstract

Tungsten-chromium-yttrium (WCrY) smart alloys are foreseen as the first wall material for future fusion devices such as Demonstration Power Plant (DEMO). While suppressing W oxidation during accidental conditions, they should behave like pure W during plasma operation due to preferential sputtering of the lighter alloying elements Cr, Y, and W enrichment of the surface. In this paper, the erosion performance of WCrY and W samples simultaneously exposed to deuterium (D) plasma with the addition of 1% of the projectile ions being argon (Ar) ions at an ion energy of 120 eV is compared. With reference to the previous experiments at 120 eV in pure D plasma, the erosion for both WCrY and W is enhanced by a factor of ~ 7. Adding Ar to the D plasma suppresses significant W enrichment previously found for pure D plasma. To investigate the impact of the plasma exposure onto the oxidation performance, plasma-exposed and non-exposed reference samples were oxidised in a dry atmosphere. Results show, on the one hand, that the oxidation suppression of WCrY in comparison to pure W is preserved during the plasma performance. On the other hand, it becomes evident that edge effects imposed by the geometry of the samples used in plasma experiments play a significant role for the oxidation behaviour.

Advanced Self-Passivating Alloys for an Application under Extreme Conditions

“…In order to investigate the plasma performance, a series of studies were performed on SMART systems [32][33][34][35][36][37]. In all these studies performance of SMART alloys was directly compared to that of pure tungsten made by an industrial company using ITER specifications [38,39].…”

“…In all these studies performance of SMART alloys was directly compared to that of pure tungsten made by an industrial company using ITER specifications [38,39]. This was made either by placing the SMART samples along with pure W samples on the same holder and by exposing them under identical conditions as realized in linear plasma device PSI-2 in Julich [32][33][34]37], or by repeating the experiments by keeping the plasma conditions identical for pairs of SMART and pure W samples, as in the experiments in the divertor simulator Magnum-PSI located in the DIFFER institute in Eindhoven [12,36].…”

“…During all exposures, the plasma parameters were chosen and controlled as closely as possible to those expected during the regular plasma operation in DEMO. The temperature of all samples was always kept in the range of 590 • C-650 • C [32][33][34][35][36][37] as expected for the first wall in DEMO [40].…”

Fusion Materials Development at Forschungszentrum Jülich

“…Here, the study by Schmitz et al is so far the only one which is available. [95] WCrY and W samples were simultaneously exposed to pure D plasma at relevant ion energies for DEMO [95,96] in the linear plasma device PSI-2; net erosion and surface recession were measured. Modeling with SDTrimSP including Cr diffusion was compared with experimental results.…”

“…This means that the materials as available also need to be studied with respect to their plasma wall interaction (PWI) and erosion properties. Here, the study by Schmitz et al is so far the only one which is available . WCrY and W samples were simultaneously exposed to pure D plasma at relevant ion energies for DEMO in the linear plasma device PSI‐2; net erosion and surface recession were measured.…”