D retention in e-beam powder-bed fused (3-D printed) tungsten exposed to high-flux deuterium plasma in Pisces-RF

Abstract

Tungsten targets produced by the additive manufacturing (AM) method of electron-beam powder-bed fusion, or 3-D metal printing, are exposed to high flux D plasma in the Pisces-RF linear plasma device with the plasma-exposed surface normal to the AM build direction. D retention was measured by thermal desorption mass spectrometry following exposure to D plasma with an associated ∼50eV D+ ion flux. D+ fluence, and operational temperature, in the ranges 5×1024–5×1026 m−2 and 400–1000 K, are explored. D retention values for the AM W are compared to identically plasma exposed ’conventional’ sintered W and it is found that total D retention is similar. However, the D thermal release is notably different. Desorption from the AM W shows reduced D retention in traps typical of sintered W, and moderately increased trapping in defect types of higher trap release energy. The dependence of D retention on fluence is also different for the AM W, revealing an uptake slower than expected from Fickian diffusion, while that for sintered W is consistent and in agreement with previous poly-crystalline W results from Pisces-B. Hydrogen transport modeling of the fluence dependence suggests that interconnected pathways for D release back to the surface during plasma-exposure can account for the slower D uptake in the AM W.