Measurements and modeling of the angular-resolved sputtering yield of D-soaked Be by 100, 300, 500 and 700 eV D+

The angular-resolved sputtering yield of Be by D+ was predicted and then measured. An ion beam at 100, 300, 500 and 700 eV from a Colutron ion source was focused onto S-65 C grade Be samples. The sample was exposed in situ to a 350 V de D plasma to remove oxide, load the surface with D and more-nearly simulate the surface which would be found during steady-state fusion device operating conditions. The angular distribution of the sputtered atoms was measured by collection on a highly ordered pyrolytic graphite witness plate. The areal density of Be (and BeO, after exposure to air) was then measured using a scanning Auger spectrometer. Total deposition was measured by deposition onto a quartz crystal oscillator placed alongside the witness plate. A three-dimensional version of vectorized fractal TRIM (VFTRIM3D). a Monte-Carlo computer code which includes surface roughness characterized by fractal geometry, was used to predict the angular distribution of the sputtered particles and a global sputtering coefficient, One-quarter million trajectories were simulated to determine the azimuthal and polar angle distributions of the sputtered atoms. A fractal dimension of 2.05, and a surface binding energy of 3.38 eV, both standard values for Be, were used. Results show reasonable agreement between the code and experimental values for total yield with the experimental yields somewhat lower. The measured angular distribution is broader (less forward peaked) than predicted by the computer simulation.