Observation of Charge Distribution in Electron Beam Irradiated Polymers using Pulsed Electro-acoustic Method

Charge distributions in electron beam irradiated polymers are observed using the pulsed electro-acoustic (PEA) method. In space environment, bulk charge accumulation in insulating materials of a spacecraft, which is exposed in the radiation of cosmic rays, is one of remarkable problems because the accumulation may sometimes cause of the unexpected accidents followed by the static discharge. Therefore, the interaction between the irradiation of the electron beam (e-beam) and the charge accumulation in bulk of polymers is tried to investigate. To understand the characteristic of the charge accumulation and the incident e-beam, the electrical properties such as the conductivity or the mobility of the carrier in polymers should be studied. Using the simultaneous measurements of the external current and time dependent charge distribution, such properties can be evaluated. To make the simultaneous measurement system, a PEA apparatus for the measurement of the charge distribution in polymers under e-beam irradiation in vacuum condition was carried out. In this paper, the charge profile in e-beam irradiated polytetrafluoroethylene film is presented as a typical example.