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-i rradiated PE samples, at a low temperature below the glass-transition tempe rature, the intensity of the long-lived component of positronium, I-3, incr eases 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 tha t the trapped electrons were affected by the intensity of the positron sour ces used for a PALS experiment. (C) 2000 Elsevier Science Ltd. All rights r eserved.