Non-local generation of plasma in a magnetic nozzle.

Many linear devices use converging magnetic fields to axially contain plasmas via adiabatic reflection. However, when a plasma source is located on the axis but somewhat distant from a magnetic nozzle, in certain cases, the plasma density has been shown to increase up the magnetic field gradient. This observation has led to some debate on the forces in play and whether simple fluid concepts like the Boltzmann equation can be usefully employed in trying to understand the system. As most of the experiments were not designed to expressly study this behaviour, the present study reports plasma measurements in a newly purpose built reactor which features a 1.5 m long glass tube where a solenoidal magnetic field and a RF generated plasma source can be progressively separated. Therefore, this study focuses on the behaviour of a low pressure radio-frequency plasma incident on a remote, converging-diverging magnetic nozzle.