Acoustic measurement techniques for bulk charge distribution in dielectrics irradiated by electron beam

Bulk charge accumulation in dielectric materials under electron beam irradiation was observed using acoustic measurement techniques. Recently, some accidents in spacecraft due to the charging up of electric potential have been reported. Some of them are caused by surface discharge normally happens in plasma environment. Some others seem to be caused by discharge due to an accumulation of charge in bulk of materials in relatively higher altitude environment. Surface charge is usually measured using surface potential meter. However, there had been no useful method to measure the bulk charge in the materials. Therefore, we have been developing the bulk charge measurement system. The developed system is applicable to measure the charge distribution in dielectrics in vacuum environment under electron beam irradiation. Using the systems, we carried out the measurements of bulk charge distributions in Kapton® film and glass materials under electron beam irradiation. In this paper, summary of some typical measurement results is introduced following the brief explanation of measurement principles.