New system for a pulsed slow-positron beam using a radioisotope

To analyze the surface of polymers using positron-annihilation lifetime spe ctroscopy (PALS), a pulsed slow-positron beam system having both a high pul sing efficiency and a good time resolution is now under development. The ti me resolution, which is defined by the full width at half maximum (FWHM), a nd the pulsing efficiency of this system were achieved to be 0.54 ns and 50 %, respectively. The lifetime of ortho-positronium (o-Ps) in low-density po lyethylene (LDPE), obtained by PALS using our new pulsing system, agreed wi th that obtained by a conventional PALS. (C) 2000 Elsevier Science Ltd. All rights reserved.