Spatial Distribution Of Trapped Charge In Electron Beam Charged Polypropylene

Calculated and measured charge distributions in polypropylene irradiated with an electron beam through a floating front electrode are compared. The analytical results were obtained from a linear model by substituting experimental values of radiation-induced conductivity during and after irradiation. Measurements of charge distributions were performed with the split-Faraday cup and the laser-induced pressure-pulse methods. The calculated and experimental results show that the charge-centroid location and the shape of the charge distribution depend on injected charge density and on time. At a certain injected charge density, all available traps in the vicinity of the range of the electrons are filled. Additional irradiation results in a drift of the injected electrons in their own field until they encounter empty traps where they are immobilized.