Dresden 2014 – wissenschaftliches Programm
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TUT: Tutorials
TUT 4: Tutorial: Festkörpercharakterisierung mit Positronen (MI)
TUT 4.1: Tutorium
Sonntag, 30. März 2014, 16:00–16:45, HSZ 201
Positrons probing matter: What we learn about lattice defects and electronic structure using positron beams — •Christoph Hugenschmidt — E21 Physik-Department und FRM II, Technische Universität München, Lichtenbergstraße 1, 85747 Garching
Monoenergetic positrons beams are applied in a large variety of experiments in solid state physics and material science. Examples are spatially resolved defect maps of plastically deformed or irradiated metals, non-destructive investigation of layered systems, the annealing behaviour of defects or the free volume in polymers. At the surface, the annihilation of positrons with core electrons initiates the emission of Auger-electrons that allows the examination of the topmost atomic layer. In addition, the electronic structure such as anisotropies of the Fermi surface can be studied too.
Within this contribution the basic properties of positron annihilation studies will be explained. The benefit of positron beam experiments will be elucidated by selected experiments, such as (i) defect sensitive positron lifetime experiments, (ii) elemental selective (coincident) Doppler broadening spectroscopy of the annihilation line, (iii) angular correlation of annihilation radiation experiments, and (iv) time-dependent positron annihilation induced Auger-electron spectroscopy.
The neutron induced positron source NEPOMUC provides the world’s highest intensity of more than 109 moderated positrons per second. An overview of the NEPOMUC beam facility and the positron instrumentation is given and future developments and applications of the high-intensity positron beam will be discussed.