Electric field effect on positron annihilation lifetime in Kapton

Sakai, Hiroaki; Minei, Shuntaro; Hirade, Tetsuya  ; Oshima, Nagayasu*; Kobayashi, Yoshinori*; Kinomura, Atsushi*; Suzuki, Ryoichi*

It was reported that psoitronium (Ps) formation probability in polymers under high electric fields were enhanced. The spur reaction model explaining Ps formation in insulating materials cannot be applied for the enhancement under high electric fields. Then we studied the Ps formation mechanism under high electric fields by observing positron annihilation lifetime in Kapton (polyimide) that does not have any Ps formation. Then Ps was not formed even under high electric fields and the elongation of the lifetime of the positrons free from Ps formation. The elongation of the lifetime of the positron and Ps formation enhancement could not be judged by the methods applied in the previously reports.