Impact of seeded plasma impurities on D retention in RAFM steels

Abstract

The effect of He seeding (He+ ion fraction, cHe+, of ~5 and ~10%) to D plasma (ion flux ~ 1.5–2 × 1021 m−2s−1, sample temperature ~ 373 K, and incident ion energy ~ 100 eV) on D retention in various reduced-activation ferritic/martensitic (RAFM) steels is investigated in the PISCES-A linear plasma device. The D retention, quantified with thermal desorption spectroscopy, is found to decrease with increasing cHe+. The He seeding leads to the formation of cone structures on the surface. Inside and below the cones, high-density He bubbles are observed with transmission electron microscopy, which are thought to be, at least partly, responsible for the reduction of D retention. The D retention is also reduced with Ar seeding, while N2 seeding results in a significant increase in the D retention.

Keywords

• RAFM steel
• Deuterium retention
• Impurity seeding