Observations of electric double layers in a magnetised plasma column

Strong electric double layers are produced in a low-density plasma column confined by an axial magnetic field and maintained by single-ended inflow of plasma along the magnetic field. The double layer evolves from an anode sheath, and ionisation within the sheath is shown to be a significant process in this conversion. Once the double layer has been formed, its axial position can be controlled by the external electric circuit. The layer exhibits an axial motion back and forth with amplitudes somewhat larger than the layer thickness.