Angle of incidence dependence of light ion physical sputtering of carbon

Even in the presence of very strong magnetic fields, hydrogenic particles in a fusion reactor will strike reactor wall components with a variety of incidence angles. In some situations, this may result in enhanced physical sputtering of carbon components. In this paper, we present experimental results for the physical sputtering of carbon as a function of H+ and He+ incidence angle, for various forms of carbon, and ion energies ranging from 50 to 3000 eV. The increase in sputtering yield at large angles is more pronounced for higher ion energies, and the angle at which the maximum yield occurs also increases with ion energy. For highly-oriented pyrolytic graphite, the angular dependence is strongest, while for less-well-oriented pyrolytic graphite, and fine-grain graphite (EK98), the sputtering yield increase with angle is much less pronounced. (orig.)