Positron annihilation lifetime of irradiated polyimide

Hirade, Tetsuya  ; Oka, Toshitaka   ; Morishita, Norio*; Idesaki, Akira; Shimada, Akihiko

Polyimide polymers such as Kapton show a very good performance at high radiation environment such as in space or in radiation facilities. Positron annihilation lifetime measurement is a widely used method for materials science, and the lifetime of triplet positronium (electron-positron pair) can give important information of free volume of polymers. However, there is no positronium formation in Kapton and hence this method was no applied for polymer studies. Here, we indicated that free positron annihilation lifetime can give information of change of free volume by showing the temperature dependence of the lifetime. We applied this method to study irradiation effects on Kapton and we successfully indicated that the free positron lifetime can be applied for polymer studies.