Regensburg 2007 – wissenschaftliches Programm
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VA: Fachverband Vakuumphysik und Vakuumtechnik
VA 1: Large instruments for science
VA 1.3: Vortrag
Montag, 26. März 2007, 10:30–10:45, H9
Novel remoderation device for brightness enhancement of the reactor based positron beam at the FRM-II — •Christian Piochacz1,2,3, Gottfried Kögel3, Christoph Hugenschmidt1,2, Klaus Schreckenbach1,2, and Günther Dollinger3 — 1TU München, Physik-Department E21, James-Franck-Strasse, 85748 D-Garching — 2ZWE FRM2, Lichtenbergstr. 1, 85747 D-Garching — 3UniBw München, Institut für Angewandte Physik und Messtechnik LRT2, Werner-Heisenberg-Weg 39, D-85577 Neubiberg
In order to enhance the brightness of the positron beam produced by the Nepomuc source, a positron remoderator was developed. This remoderation device has been installed at the first accessible point of the beam facility and first measurements have been done in order to obtain the efficiency of the setup and the quality of the remoderated beam. The remoderator is built up in reflection geometry: positrons from the source are focused onto a W(100) single crystal where they are thermalized and diffuse back to the surface. Due to the negative workfunction of tungsten the positrons can leave the solid with a sharp energy of 3±0.03 eV and with a small angular divergence of ± 0.1 eV. In contrast to existing remoderators used in table top experiments the presented setup is designed to accept a beam with a greater phase space volume, which is typical for positron sources at large scale facilities. An overview of the assembly will be given and first measurements will be presented.