[en] Strong electric double layers (eV/kTsub(e) approximately 10) are produced in a 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. Once it 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 which is about 30 plasma Debye lengths