An actively shielded superconducting magnet having a dipole shim coil for
adjusting and fine-tuning an external or far fringe magnetic field
produced by a main coil of the magnet. An active shield coil is coupled
to the main coil in reverse polarity and produces a magnetic field when
energized that opposes the far fringe field to substantially reduce the
far fringe field. The dipole shim coil is electrically isolated from the
active shield and main coils of superconducting magnet, and produces a
magnetic field when energized that provides for the fine adjustment of
any residual far fringe field.