Measurement of sputtered beryllium yield and angular distribution during nanostructure growth in a helium plasma

The angular distribution and sputtering yield of beryllium exposed to helium plasma are estimated from analysis of line-integrated 2D imaging of Be-I line emission in a steady-state linear plasma device. As the surface nanostructure forms during plasma exposure on a ∼100 s timescale (corresponding to a fluence of order 1020/cm2) from nearly mono-energetic ion bombardment, a narrowing of the beryllium sputtering angle and a significant (∼5×) drop in sputtering yield are observed. These trends are found to be qualitatively consistent with modeling taking into account the effect of the surface morphology on sputtering yield and angular distribution.