Surface and Internal Charge Measurement in Fluorinated Polymer Irradiated by Electron Using Non-contact Type PEA Method Measurement Apparatus

Spacecrafts are exposed by the radioactive rays, such as high energy electrons and protons, plasma. The surface insulating materials of spacecraft are charged because of exposing by such high energy charged particles. This charging phenomenon is the origin of the electrostatic discharge and may lead to the fatal error of those operations. For the improving the reliability of spacecraft operation, we should understand charge accumulation phenomena based on the real surface condition. Therefore, our grope and other researchers have tried to develop systems to measure the surface and bulk charges of materials. As the results, we developed new space charge measurement equipment using the pulsed electroacoustic (PEA) method. That system can apply the pulsed electric filed to the sample through the vacuum gap using a grid electrode located 125 μm above the sample. Electrons through the grid electrode to the sample. Therefore, this apparatus can measure the surface and internal charge accumulation in the bulk of materials. Although we had measured only internal charge accumulation by the conventional PEA method, we obtained a seamless charge profile from the surface to internal of the sample by such newly developed system. In this report, we measured space charge distribution in the fluorinated materials by above developed system under electron irradiation. We found the following results. The negative charge accumulation distributed from the irradiation surface to penetration depth in the bulk. The amount of irradiated electrons accumulation was more than 30 times as much as the results obtained by a conventional measurement system. From those results, the space charge distribution has been able to measure under conditions consistent with close to actual use.