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

抄録

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.