Development of Bulk Charge Measurement System in Dielectric Materials for Spacecrafts

Measurement systems for surface and bulk charge distributions on and in dielectric materials are developed using optical and acoustic 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 and/or electronics 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 some unique measurement methods using optics and acoustic techniques to observe the distribution in and on the materials under electron beam irradiation. In the optical method, so called Pockel's and Kerr effects are used as the basic principle. On the other hand, the PEA (Pulsed electro-acoustic) and Pressure Wave Propagation methods are used. Using these methods, we have succeeded in measuring the surface and the bulk charge distributions on and in dielectric materials under electron beam irradiation. Furthermore, an effect of the accumulated bulk charge on dielectric breakdown was also investigated using acoustic method.