Surface modification and deuterium retention in reduced activation ferritic martensitic steels exposed to low-energy, high flux D plasma and D₂ gas

Samples prepared from steels F82H and EUROFER97 were irradiated with 20 MeV W ions at 300 K to 0.54 displacements per atom at the damage peak. Damaged and undamaged samples were exposed at elevated temperatures both to deuterium plasma at ion energies of 60 and 200 eV to a fluence of ≈10²⁶ D m ^-2 and to D₂ gas at a pressure of 100 kPa. The surface modification after plasma exposure was examined by scanning electron microscopy and Rutherford backscattering spectroscopy. Deuterium depth profiles were determined by the D(³He, p)⁴He nuclear reaction. In damaged steels loaded with deuterium, deuterium decorates the damage profile and the D concentration decreases with increasing temperature. After exposure of the F82H steel to the D plasma W-enriched near-surface layers are formed. The effective concentration of W in the near-surface steel layer depends on plasma exposure conditions.