Surface charge characteristics on insulators in vacuum under DC voltage

Accumulation of insulator surface charge with DC loaded in vacuum is studied with electrostatic capacitive probe by measuring the surface charge of insulators of various roughnesses at different applied voltages and loading time. The measurement results indicate that the average surface charge density is affected by the structure of electrode and grows with the increment of the magnitude and duration of the applied voltage. It is concluded that the increment of insulator surface roughness would enhance the collection of surface charge, but it may bring the higher energy level trap center to suppress the accumulation of surface charge. The accumulation and decay of surface charge is affected with the pressure and surface charge on insulator is positive with negative DC voltage in vacuum.