[en] Experiments have been carried out on the linear EXTRAP apparatus. In this device, the plasma is basically a straight Z-pinch, but the axial plasma current channel is along the axial null field line of an octupole vacuum magnetic field. The vacuum magnetic field is generated by currents in four rods. The rod current, J/sub v/, is antiparallel to the plasma current, J/sub p/. All magnetic fields are transverse (poloidal) relative to the longitudinal axis of the discharge and the device becomes a field-reversed configuration if the plasma current is of sufficient magnitude and sufficiently localized