Interaction between seeding gas ions and nitrogen saturated tungsten surfaces

Abstract

In a fusion reactor, where nitrogen is used as a seeding gas to mitigate the heat load to the plasma facing components, it is expected that mixed tungsten-nitride surfaces will build-up during operation. For fusion research it is of major concern to investigate the influence of such mixed material layers on physical properties of the plasma facing components such as e.g. their sputtering yield, their electrical conductivity or their melting point. Sputtering of pure tungsten W, and nitrogen saturated tungsten W-N surfaces under the impact of argon Arq+ (q=1–9) and neon ions Neq+ (q=1, 4) was therefore investigated under controlled laboratory conditions using a quartz crystal microbalance technique. Total sputtering yields were determined in an impact energy range of 100–5000eV. Particular emphasis was put on testing any charge state dependency of the sputtering yield (i.e. potential sputtering), which was not found for neither of the investigated surfaces.