Radiation effect on positronium formation in low-temperature polyethylene

The irradiation effect of gamma-rays on polyethylene (PE) has been studied by positron annihilation lifetime spectroscopy (PALS). In the case of non-irradiated PE samples, at a low temperature below the glass-transition temperature, the intensity of the long-lived component of positronium, I-3, increases due to an increase in the concentration of trapped electrons. However, the increase in I-3 obtained in a few MGy gamma-irradiated samples became very small due to the effect of induced radicals. It has been observed that the trapped electrons were affected by the intensity of the positron sources used for a PALS experiment. (C) 2000 Elsevier Science Ltd. All rights reserved.