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L. Ballauf, F. Hechenberger, R. Stadlmayr, T. Dittmar, M. Daxner, S. Zöttl, F. Aumayr, Z. Herman, P. Scheier:
"Formation of beryllium-hydrogen ions in chemical sputtering from 20 to 420 eV";
Nuclear Materials and Energy, 22 (2020), 1007221 - 1007228.

The formation of BeD+ in collisions of deuterium molecular ions with a beryllium surface at hyperthermal
energies is investigated, using a purpose-built tandem mass spectrometer setup, "SurfTOF". In the manifold of
products, hydrogen-containing molecules are of special interest in fusion devices. Our experiments show, that
they can be formed in nearly all conditions comparable to plasma and wall temperature, with two mechanisms
involved: First, BeD+ is formed directly in a reaction of the D2
+ projectiles with the Be surface, which is the
main aspect of this work. There was no evidence found, that this particular mechanism relies on D implanted in
the bulk Be. BeD2
+ was not detected. The second reaction pathway produces BeH+. It is efficiently formed when
H2O molecules are adsorbed on the surface, much less abundant for hydrocarbon adsorbates. The yield of Be+,
BeH+ and BeD+ products, is measured as a function of several parameters: Scanning the impact energy from 20
to 426 eV reveals that the molecular BeD+ is preferably produced at low energies. At 20 eV, its abundance is
three times higher than that of pure Be+. When the surface temperature is raised from 298 to 673 K, sputtering
yields increase two orders of magnitude for both, Be+ and BeD+.

Low energy sputtering Chemical sputtering BeD+ Thermonuclear fusion Adsorbate sputtering Fuel retention

http://dx.doi.org/10.1016/j.nme.2019.100722