Patent ID: 7898258

Claim:
A superconducting magnet configuration with active shielding for generating a homogeneous magnetic field B 0 in an examination volume, the magnet configuration comprising: a radially inner superconducting main field coil which is disposed rotationally symmetrically about a z-axis and having an axial length L haupt , said main field coil comprising an unstructured solenoid coil or several radially nested unstructured solenoid coils, which are driven in a same direction; a superconducting shielding coil disposed coaxially and radially exterior to said main field coil, said shielding coil generating a magnetic field in the examination volume which is directed substantially opposite to a magnetic field generated by said main field magnet in the examination volume, said shielding coil having an axial length L abs which is smaller than said axial length L haupt of said main field coil, wherein a combined axial magnetic field profile generated by said main field coil and said shielding coil has a field strength minimum along said z-axis in a center of the examination volume and a field strength maximum on each side of said center; and a ferromagnetic field formation device disposed radially within said main field coil, wherein an axial magnetic field profile generated by said ferromagnetic field formation device has a field strength maximum along said z-axis in said center of the examination volume and a field strength minimum on both sides of said center.