A cylindrical superconducting magnet system for use in magnetic resonance imaging has axially aligned primary superconducting coils surrounded by a thermal radiation shield within a vacuum vessel. A gradient coil assembly is axially aligned with and located radially within the primary superconducting coils. An assembly support is, radially positioned outside of the primary superconducting coils and is mechanically attached to the gradient coil assembly at a number of locations around the circumference of the gradient coil assembly, and at a number of axial locations along the gradient coil assembly, by radially-directed mechanical attachments that pass though through-holes through the vacuum vessel and the thermal radiation shield, and mechanically isolated from the vacuum vessel. At least some of the mechanical attachments each comprise an active force transducer arranged to provide impulses of force onto a surface of the gradient coil assembly to oppose vibrations of the gradient coil assembly.