Experimental investigation of the plasma wall transition [Elektronische Ressource] / von Tilmann Alexander Lunt

Experimental Investigation of the Plasma-WallTransitionDISSERTATIONzur Erlangung des akademischen Gradesdoctor rerum naturalium(Dr. rer. nat.)im Fach Physikeingereicht an derMathematisch-Naturwissenschaftlichen Fakultät IHumboldt-Universität zu BerlinvonHerr Dipl.-Phys. Tilmann Alexander Luntgeboren am 27.09.1976 in HamburgPräsident der Humboldt-Universität zu Berlin:Prof. Dr. Dr. h.c. Christoph MarkschiesDekan der Mathematisch-Naturwissenschaftlichen Fakultät I:Prof. Dr. Christian LimbergGutachter:1. Prof. Dr. Gerd Fußmann2. Prof. Dr. Uwe Schumacher3. Dr. habil. Hans-Stephan Boscheingereicht am: 14.2.2008Tag der mündlichen Prüfung: 17.7.2008AbstractIn the present work the streaming behavior of a magnetized argon plasmaimpinging on a neutralizing surface was investigated. For that purpose theion velocity distribution was measured non-invasively as a function of thedistance to the surface by means of Laser Induced Fluorescence. The spatialresolution was typically Δz = 0.5 mm.Two situations are investigated, (a): when practically the whole plasmastreams onto a large target (? = 100 mm), and (b): when the size of thetarget (? = 15 mm) is significantly smaller than the diameter of the plasmacolumn. Inbothcasesthestreamingvelocityu wasatleastashighastheioniacoustic sound speed, as already predicted by Bohm in 1949. Under fusionrelevant conditions this is the first direct observation of the Bohm criterion.