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The pulsed low-energy positron beam system PLEPS for defect structure investigations: Principles and applications in materials sciences.
Positrons are very sensitive probes to analyse atomistic open volume defects in solids, $e.g.$ vacancies, vacancy-clusters, dislocations and small voids. Modern positron beam technology has developed into a powerful tool which allows to investigate defect structures in the sub-micrometer range in a wide variety of materials. The pulsed low-energy positron beam system PLEPS is a unique user facility at the intense positron source NEPOMUC at the MLZ in Garching, Germany, for defect depth-profiling with positron lifetime measurements using a pulsed positron beam of variable implantation energy. Typical applications of PLEPS comprise defect identification in thin layers and layered structures of semiconductors and insulators, irradiation induced defects in materials for fusion and fission reactors, as well as the characterization of free volumes in polymer- and membrane-layers and in glasses. Here we describe the present setup of PLEPS and its performance, show some exemplary applications and give an outlook of new developments.