Patent ID: 8154368

Claim:
An actively shielded superconducting magnet configuration for generating a homogeneous magnetic field B 0 in a volume under investigation, the configuration comprising: a radially inner superconducting main field coil, said main field coil being disposed in a rotationally symmetric manner about a z-axis, said main field coil consisting essentially of an unstructured solenoid coil or of several radially nested unstructured solenoid coils which are operated in a same direction; a superconducting shielding coil, said superconducting shielding coil disposed coaxial to and radially outside of said main field coil, said shielding coil centered axially within ends of said main field coil and generating a magnetic filed which is directed opposite to a magnetic field generated by said main field coil, said shielding coil having a length L abs in an axial direction which is smaller than a length L haupt of said main field coil in said axial direction; a ferromagnetic field-shaping device, said ferromagnetic field-shaping device disposed radially inside said main field coil, wherein ⅆ 2 ⅆ z 2 ⁢ B H + A ⁡ ( z ) ⁢ | z = 0 ⁢ ≤ 0 applies for an axial magnetic field profile B H+A (z) generated by said main field coil and said shielding coil ( 2 ) during operation along said z-axis in a center at z=0, and ⅆ 2 ⅆ z 2 ⁢ B F ⁡ ( z ) ⁢ | z = 0 ⁢ ≥ 0 applies for an axial magnetic field profile B F (z) generated by said ferromagnetic field-shaping device during operation along said z-axis in said center at z=0, wherein said z-axis is oriented in a positive direction of said B 0 -field.