Direct observation of space charge evolution in e-irradiated Kapton films

The pressure wave propagation method was applied to analyze in a vacuum the evolution of the space charge in electron-irradiated Kapton H films. The 125 μm thick films were irradiated in a vacuum chamber with a monoenergetic electron beam in the 10 to 50 keV energy range. The method allows direct observation of the depth of penetration of electrons and first results on Kapton are presented. The space charge generated in the irradiated and nonirradiated regions was observed during and after the irradiation process. The space charge is influenced by electric field-assisted detrapping of incident electrons and their interaction with the lattice as they drift. Interfacial effects are indicated by the buildup of a negative charge layer at the metal-polymer interface