Vacuums have been attractive media for researchers and industry to obtain useful plasma, energized particles and current switching effects. These applications require sophisticated control of high voltages or high electric fields, plasma parameters such as density and temperature of charged particles, potential distribution, etc. This article reports current topics on the electrical insulation and plasma application in vacuum. キーワード:真空中の絶縁,プラズマ応用,二次電子放出,高電圧真空遮断器,中性子源,陽子源,パルスX線源 Keywords:Insulation, plasma application, SEY, high voltage vacuum interrupter, neutron and proton sources, pulse X-ray source