Real-time and high-speed measurements of charging processes on dielectric surface in vacuum

For efficient electrical insulation in vacuum equipment, it is needed to clarify the mechanism of electrostatic charging and resulting discharge processes on a dielectric surface. We investigated charging characteristics on solid dielectrics in vacuum by real-time and high-speed measurement systems. By applying negative DC ramped voltage to the electrode with a cathode triple-junction (TJ), we measured the time transition of surface charge accumulation and current waveforms expressing the electron emission from TJ, by electrostatic probes. From the measurement results, we clarified a steplike charging process and proposed the electron emission model by taking the electric field and its relaxation by charging into account.