Measurement of 2-Dimensional Surface Charge Distributions under Vacuum Flashover Events on Insulators with Sub-milli-second temporal resolution

Most studies on a flashover event in vacuum has revealed that the surface charging on insulator has a great influence on the flashover. However, regarding most studies related to the surface charging, their measurements were carried out after high voltage excitation. In this research, the measurement of 2D surface charge distributions in real time has been carried out in vacuum by Pockels effect. With this measuring method, the charge distributions on a dielectric sample can be measured from the high voltage application to the surface flashover event. This paper describes the changes of the surface charge distributions on a PET film under non-uniform ac voltage application in vacuum. Moreover, using this method, the charge distribution just before and after a surface discharge event on the PET film has been measured. Especially we focus on the distribution near the triple junction just before and after the surface discharge event