Ion polishing of copper: some observations.

The change in absorptivity at 10.6 microm of copper samples, at various stages of polishing including ion polishing, is reported. The ion polishing apparatus is also described; it employs a low energy Xe ion beam incident at a glancing angle to maximize the removal rate while minimizing ion penetration and damage. The sample to be polished is rotated and the beam scanned across the surface to produce uniform removal of material. Starting with single crystal copper that had been mechanically polished and by using combinations of ion polishing and vacuum annealing, the absorptivity, determined by calorimetry, was reduced from 0.92% to 0.76%. Although optical figure and scatter were not monitored, SEM pictures show that the surface features become smoother with ion polishing. A similar experiment was performed on a single crystal copper sample that had been electropolished, and the combination of ion polishing and annealing lowered the absorptivity from 0.97% to 0.89%.