Light ion sputtering of fusion reactor materials in dependence of angle of incidence

It is well known that the sputtering yield at glancing incidence can exceed the yield at normal incidence by a factor of 10. On the other hand, the angular distribution of sputtered material is highly asymmetric and peaked in the forward direction relative to the incident beam. Therefore the increase of the impurity flux perpendicular to the surface of the first wall is not only dependent on the total yield, but also on the angular distribution of the incident plasma particles. In this paper, total-yield data and angular distributions of sputtered particles, as functions of the incidence angle, are reported for Ni and NbB2 bombarded by H+ and D+ ions in the keV energy range. Conclusions for the impurity flux perpendicular to the surface are drawn, based on these experimental data and on different assumptions for the incidence conditions of the plasma particles. (orig.)