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  • 1 High Energy Accelerator Research Organization Tsukuba, Ibaraki 305-0801 Japan
  • 2 Institute for Environmental Sciences Obuchi, Rokkasho-Mura, Aomori 039-3212 Japan
  • 3 Tokyo Institute of Technology Research Laboratory for Nuclear Reactors Ookayama, Meguro-ku, Tokyo 152-8550 Japan
  • 4 High Energy Accelerator Research Organization Oho1-1 Tsukuba, Ibaraki 305-0801 Japan
  • 5 RCNT, University of Tokyo, JAERI Tokai-Mura, Ibaraki 319-1106 Japan
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Abstract  

A new pulsed mono-energetic slow positron beam as well as the conventional positron annihilation lifetime spectroscopy (PALS) have been applied to study the sub-surface and the bulk of epoxy polymer. Significant changes of o-Ps parameters were found at a short distance from the surface. The lifetime of o-Ps was observed to decrease with increasing the positron implantation depth, while its intensity increased. The temperature effect on o-Ps parameters at sub-surface was also investigated. The glass transition temperature for the sub-surface was lower than that for the bulk. Furthermore, the thermal expansion coefficient of the sub-surface was found smaller than that of the bulk.