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K. Dobes, M. Köppen, M. Oberkofler, C. Lungu, C. Porosnicu, T. Höschen, G. Meisl, F. Aumayr:
"Interaction of nitrogen ions with beryllium surfaces";
Nuclear Instruments & Methods in Physics Research Section B, 340 (2014), 34 - 38.

The interaction of energetic nitrogen projectiles with a beryllium surface is studied using a highly sensitive
quartz crystal microbalance technique. The overall mass change rate of the beryllium sample under
N2 + ion impact at an ion energy of 5000 eV (i.e. 2500 eV per N) is investigated in situ and in real-time. A
strong dependency of the observed mass change rate on the nitrogen fluence (at constant flux) is found
and can be attributed to the formation of a nitrogen-containing mixed material layer within the ion penetration
depth. The presented data elucidate the dynamics of the interaction process and the surface saturation
with increasing nitrogen fluence in a unique way. Basically, distinct interaction regimes can be
discriminated, which can be linked to the evolution of the surface composition upon nitrogen impact.
Steady state surface conditions are obtained at a total cumulative nitrogen fluence of 80 1016 N
atoms per cm2. In dynamic equilibrium, the interaction is marked by continuous surface erosion. In this
case, the observed total sputtering yield becomes independent from the applied nitrogen fluence and is of
the order of 0.4 beryllium atoms per impinging nitrogen atom.

Plasma wall interaction Sputtering Erosion Beryllium