Bochum 2015 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 27: Diagnostics II

P 27.2: Vortrag

Donnerstag, 5. März 2015, 14:30–14:45, HZO 30

Investigations on the Bohm criterion in two-component plasmas — •Tsanko Vaskov Tsankov and Uwe Czarnetzki — Institute for Plasma and Atomic Physics, Ruhr-University Bochum, 44780 Germany

Despite the long history of the field of plasma physics and the ubiquitous investigations and application of plasmas with multiple ion species, the fundamental problem about the Bohm criterion [1-3] in such plasmas remains unsatisfactory resolved. The generalisation of the well-known Bohm criterion for more than one species of ions gives only a general relation between the velocities of the various ion species at the sheath edge but does not specify them uniquely. Theoretical works [1,2] suggest different possibilities for fixing the velocities of the ions entering the sheath. Laser induced measurements [3], however, at somewhat untypical conditions seem to support one of the theories.

In this work we employ a different experimental approach to the problem. By combining information about the spatial distributions of the plasma parameters and the mass-resolved energy distributions of the ions reaching the walls we shed some light on the problem in a more typical plasma configuration. The results seem to disagree both with the main theories [1,2] and the previous measurements [3].

[1] R N Franklin, J. Phys. D: Appl. Phys. 33 (2000) 3186

[2] S D Baalrud, C C Hegna, Phys. Plasmas 18 (2011) 023505

[3] N Hershkowitz, C-S Yip, G D Severn, Ibid. 057102