In situ observation of damage evolution in polycarbonate under ion irradiation with positrons

We report β+–γ coincidence positron annihilation lifetime spectroscopy of in situ observation of ion damage in polycarbonate under irradiation by MeV-energy H+ ions. Ion damage was investigated from changes in the relative intensity of the long-lived ortho-positronium pick-off annihilation lifetime component measured under irradiation and non-irradiation conditions. It was found that at fluences of less than 1015 ions·cm−2 the relative intensity of this component during irradiation was significantly reduced compared to that after irradiation. This reduction disappears at fluences higher than 1015 ions·cm−2. Results suggest that at fluences up to 1015 ions·cm−2, transient damage structures are formed under irradiation.