Development of Bulk Charge Measurement System in Dielectric Materials for Spacecrafts

利用光学和声学方法开发了用于测量电介质材料上和电介质材料中的表面和体电荷分布的测量系统。在空间环境中，航天器受到高能宇宙射线的照射。当宇宙射线照射到航天器上时，航天器表面绝缘材料的电势充电。有时，电势的变化会导致静电放电（ESD）的意外事故，对电气和/或电子设备造成严重损坏。为了了解静电放电的机理，需要测量电介质材料表面的电荷分布和/或电介质材料中的体电荷分布。因此，我们提出了使用一些独特的测量方法，使用光学和声学技术来观察电子束辐照下材料内部和表面的分布。在光学方法中，所谓的Pockel和Kerr效应被用作基本原理。另一方面，使用PEA（脉冲电声）和压力波传播方法。利用这些方法，我们已经成功地测量了电子束辐照下电介质材料的表面和体电荷分布。此外，还利用声学方法研究了累积体电荷对介质击穿的影响。

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.