Patent ID: 7183769

Claim:
An actively shielded superconducting magnet system for high-resolution magnetic resonance spectral analysis of a sample, the system comprising: a substantially cylindrical cryostat having an axial, room temperature bore for receiving the sample; a radio frequency transmitting and detecting system; a magnet coil which is superconductingly short-circuited during operation, said magnet coil having a main coil and a shielding coil which radially surrounds said main coil, said magnet coil being disposed at a low temperature within said cryostat to surround the sample and to generate a homogeneous, temporally stable magnetic field at the sample location, said magnet coil having a stray magnetic filed which is considerable reduced relative to that of a non-actively shielded magnet system; a drift compensation coil rigidly mechanically and thermally connected to said shielding coil, said drift compensation coil being substantially magnetically decoupled from said magnet coil; an external current supply; and means for connecting said external current supply, at least in time intervals, to said drift compensation coil to control and regulate a current fed into said drift compensation coil in accordance with a predetermined program such that the field at the sample location only differs from a desired value within a predetermined range.