真空中で高電圧印加部の絶縁に固体絶縁物を用いる場合、その絶縁性能は、通常絶縁物の沿面放電に制約を受ける。電子・イオン等の荷電粒子の加速装置、イオン源等の実用的な装置は、高真空中で使用されることがある。したがって、これらの装置の絶縁設計には、使用圧力領域での沿面放電電圧の評価が重要となる。そのため本研究では、よく利用される圧力領域ではあるが従来データの少ない1×10 -3 ～ 1.33×10 -1 Pa の高真空中での沿面放電電圧を測定し、沿面放電発生時の電界強度が、6 ～ 15 kV/mmであることを把握した。また、沿面放電耐力向上のための試みについてその有用性を確認した。

When dielectrics are used for electrical insulation in a vacuum, their ability tosustain voltage is usually limited by flashover on the surface of the dielectrics. Foractual industrial equipment such as particle accelerators, ion sources, the pressure inthe equipment is sometimes comparatively high. Therefore, in designing such industrialequipment, it is necessary to measure the surface flashover voltages of the dielectricsunder the gas pressure mentioned above. Surface flashover voltages were measured under thepressure of 0.001 to 0.133 Pa. When the electric field strength was about 6 to 15 kV/mm,the flashover occurred. Improvements in surface flashover voltage were confirmed when adepression was made on the cathode, the flashover voltage becoming 1.6 times higher thanthat obtained for the ordinary cathode. Also, the flashover voltage became 2.6 timeshigher, when the dielectrics were employed with a slope angle of 10 degrees.