Research on vacuum insulation properties — In situ measurements and surface analysis

Ion beam sputter cleaning, electrode surface heating by an infrared-ray, and an X-ray Photoelectron Spectroscopy (XPS) system were equipped in conjunction with a vacuum breakdown measurement apparatus (in situ experiment system). This system enables to carry out surface treatments, surface analysis and breakdown characteristics measurements without exposure of sample electrodes to air. It was confirmed that in situ surface cleaning was effective and necessary to achieve higher conditioned breakdown field. However, also confirmed was that the breakdown field after the in situ cleaning did not always improve breakdown field at the first voltage application. Conditioning was carried out by repetitive breakdowns by applying impulse voltage application. Surface analysis revealed that electrode surface before the conditioning was covered with oxidized layer and hydro-carbon contaminated layer and those layers were completely removed after the conditioning. Electrode heating was able to get clean surface and achieve higher conditioned field. Many experimental results obtained from in situ system represent that precautions of electrode surface were necessary but was not sufficient, and strongly suggest there may be factors to be found out.