Reduction of Metal Oxides by Electron Cyclotron Resonance (ECR) Plasma of Hydrogen–A Model Study on Discharge Cleaning

A reduction experiment on oxides of Cu, Ni, Fe, Mo and Ti was carried out, using a low electron temperature ECR plasma of hydrogen. Reduction rates of these oxides were estimated by observing the disappearance of interference rings of oxide layers. The reduction efficiency η of H + flux was evaluated; η=0.4 for copper oxide and 10 -3 <η<10 -2 for other oxides. Roughly, the reduction rate decreased with an increase in the metal-oxygen binding energy. It was shown that oxide layers with a thickness in the order of magnitude 10 -1 µm were reduced without difficulty. It is of interest from the viewpoint of discharge cleaning of fusion-oriented machines.