Double layer formation in a magnetised laboratory plasma

Three-dimensional time dependent double layers with a potential difference higher than the ionisation potential have been created in magnetised, current-carrying argon, helium and zenon plasmas, starting from an unstable anode sheath. Accelerated particles of both kinds, except for axially accelerated ions, and high frequency emission have been detected. Time independent models based on Maxwell's equation in one dimension including ionisation are shown to give a partial understanding of the phenomena. (U.K.)