Nitrogen and neon retention in plasma-facing materials

Tungsten plate was exposed in the TEXTOR tokamak during nitrogen-assisted discharges. In order to determine material mixing on tungsten, the plate was examined ex situ with ion beam analysis techniques including time-of-flight heavy ion elastic recoil detection analysis and also with X-ray photoelectron spectroscopy. Nitrogen content in the range from 1.3 × 1015 to 3.4 × 1015 cm−2 is measured in the outermost surface layer (20 nm) of the W plate. Photoelectron spectroscopy detects nitrogen both in the elemental and compound form, i.e. tungsten nitride (WN/W2N). Nitrogen is measured even in hot areas free from deuterium. Also neon co-implantation into the plasma-facing components has been identified following Ne-cooled pulses.