High-voltage double layers in a magnetised plasma column

Abstract

Observations of very strong double layers with potential drops up to 1 kV are reported. The experiments are made in a triple plasma device where a magnetised plasma column is maintained in the central chamber by two plasma sources. Axial potential profiles are presented as well as probe measurements showing the existence of an energetic electron beam on the high-potential side of the layer. Experimental evidence of the validity of the Langmuir condition is also given. The double layers are stable for a wide range of parameter values, but instabilities leading to large amplitude fluctuations appear for certain parameter combinations.