Berlin 2005 – wissenschaftliches Programm

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P: Plasmaphysik

P 21: Poster: Plasma-Wand Wechselwirkung 2, Theorie 2, Dichte Plasmen 1, Schwerionen- und lasererzeugte Plasmen 2

P 21.1: Poster

Montag, 7. März 2005, 16:30–18:30, Poster HU

Shadows in magnetised plasmas — •Ole Waldmann, Bernd Koch und Gerd Fussmann — Institut für Physik der Humboldt Universität zu Berlin

Immersing a small target in a plasma streaming along a magnetic field, a distinct shadow region extending over large distances (≥ 1m) is observed by bare eye downstream of the target. In addition, for some plasma conditions, the region upstream of the target becomes brighter forming a so called “inverse shadow”. In this work we present an experimental study of this effect. The presented results were obtained at the linear plasma device PSI-2. This device produces a clear hollow-shaped profile in electron temperature and density (B≈0.1 T, n_e ≈ 10¹⁶−10¹⁹ m⁻³, T_e≈ 1−15 eV). Differently shaped objects made from tungsten and mounted floating were placed in the plasma column. Langmuir probes and passive spectroscopy were used as diagnostic methods. Measurements were performed in the up- and downstream direction of the tungsten objects. In contrast to earlier predictions there was quite a strong effect on the density not only in the shadowed region but over the whole plasma cross-section whereas the electron temperature was only marginally affected.