Influence of surface temperature, ion impact energy, and bulk tungsten content on the sputtering of steels: In situ observations from plasma exposure in PSI-2

Abstract

• PSI-2 deuterium plasma exposures of 3 RAFM steels. • In-situ measurement of relative sputtering yields by optical emission spectroscopy. • In-situ measurement of the evolution of surface morphology by IR camera. • Post-mortem measurement of tungsten enrichment by RBS, SEM and EDX. • Independent measurements allow to disentangle the impact on the erosion of Fe. This study presents results from PSI-2 deuterium plasma exposures of reduced-activation ferritic martensitic steels with different tungsten content at a peak plasma flux of 9 · 10 20 D/m 2 s and 420–920 K sample temperature. Via optical emission spectroscopy the relative sputtering yield of Fe and Cr, and via an infrared camera the evolution of surface morphology is studied in-situ in 2D. After the exposure, RBS, SEM and EDX reveal tungsten enrichment and the formation of surface structures. Due to the independent measurement of surface morphology and tungsten enrichment, it is possible to disentangle the impact of both effects on the erosion of Fe. As part of this study, we investigate the effects of tungsten content, sample temperature and ion impact energy. The results show a reduction of the sputtering yield, depending on the exposure conditions, up to a factor of 2 at 130 eV ion impact energy and 720 K sample temperature.