Optical measurement techniques for surface and bulk charge distribution

Surface and bulk charge distribution on and in dielectric materials is measured using optical methods. In space environment, a spacecraft is exposed by high-energy cosmic rays. The electric potential of insulating materials on the surface of the spacecraft charged up when the cosmic rays are irradiated to the spacecraft. Sometimes, the change of the electric potential causes an unexpected accident of electrostatic discharge (ESD) with serious damage to the electric devices. To understand the mechanism of the ESD, the measurement of charge distribution on surface of the dielectric materials and/or bulk charge distribution in dielectric materials should be carried out. Therefore, we have proposed to use an optical method using Pockels and Kerr effects for the measurement of surface and bulk charge distributions, respectively. Using these methods, we have already succeeded in measuring the surface charge distribution on Kapton® and measuring the bulk charge distribution in PMMA irradiated by electron beam. In this paper, a summary for the optical measurement results is introduced following the brief explanation of the measurement principles.