Vacuum electrical breakdown characteristics and surface chemical compositions of titanium electrodes with oxidation conditions

Outgassing from an electrode is regarded as one of factors leading electrical breakdowns in vacuum. It was already reported that oxidation treatment 200°C for titanium is effective to reduce outgassing because of its thin and fine oxide layer created on the surface. Breakdown characteristics of titanium electrodes with different oxidation conditions (without oxidation. with oxidation at 200°C and 450°C) were investigated and compared, in order to clarify the dependence of the oxidation treatment on the breakdown characteristics. In addition, chemical composition on the electrode surface was analyzed by X-ray Photoelectron Spectroscopy (XPS) before and after 500 repetitive breakdowns. Experiments clarified that breakdown field at the first voltage application is highest and conditioning effect is significant for the electrodes at 200°C oxidation.