Interaction of a tin-based capillary porous structure with ITER/DEMO relevant plasma conditions

Abstract

a b s t r a c tSn filled capillary porous structures were exposed to high flux low temperature plasma conditions at the Pilot-PSI linear device. Enhanced erosion above that expected classically was investigated via spectroscopic observation of Sn 0 emission from the plasma in front of the target surface while the surface temperature was monitored by both thermography and pyrometry. An anomalous erosion flux was observed as temperature increases, with onset for this occurrence varying strongly between different ion species. The results appear incompatible with existing 'adatom' models for the anomalous erosion flux. Further targets were exposed in turn to increasing heat fluxes and the heat removed determined from cooling water calorimetry, which was then compared to a solid Mo reference target. At high powers the total energy of the cooling water is reduced, indicating a shielding of the surface from the plasma heat flux by the vapour cloud in front.

Self-Regulated Plasma Heat Flux Mitigation Due to Liquid Sn Vapor Shielding

“…The removed power for these particles is redeposited onto the surface and is, thus, not a power-loss channel. Redeposition rates of Sn in Pilot-PSI at similar conditions have been previously reported, revealing fractions Y ≥ 0.92 [19]. In addition, a depletion of Sn in the top layer of mesh in the target was observed after 100 s of plasma exposure, resulting in a loss of 0.45 g Sn.…”

Liquid metals as a divertor plasma-facing material explored using the Pilot-PSI and Magnum-PSI linear devices

“…Similar ratios are seen for D sputtering on Be (E eff =2 eV compared to E SBE =3.41 eV) and molten Li (E eff =1.1 eV compared to E SBE =1.67 eV) [61], which indicates a similar process occurs in all cases. A different behaviour is observed however for H interaction with Sn, where an increasing signal is observed with much lower temperatures than in other cases [65]. Here, the effective energy is only E eff =0.27 eV, which indicates a different type of thermally activated process is likely responsible (figure 1).…”

“…Here, the effective energy is only E eff =0.27 eV, which indicates a different type of thermally activated process is likely responsible (figure 1). We proposed that stannane (SnH 4 ) formation may account for such an effect [65]. It is known [68] that gaseous tin hydrides can form in the presence of hydrogen radicals, which would support this.…”

“…Temperature dependence of the anomalous sputtering flux of Sn under Ar, He or H loading in Pilot-PSI (based on data from[65]). The Arrhenius-like behaviour is similar for Ar and He despite quite different erosion fluxes, but is very different for H, implying a different process is responsible for the erosion flux.…”

Structural and dynamic properties of liquid tin from a new modified embedded-atom method force field

“…Relevant liquid metal properties include viscosities, diffusivities, hydrogen solubilities, and wetting properties. Recently, experimental studies have been performed focusing on the understanding of properties of liquid lithium 9,10 and liquid tin 11,12 in the context of plasma-facing materials.…”