Abstract: A system for the generation of magnetic gradient fields which intermittently overlap the static magnetic field of a nuclear-spin tomograph, with at least one pair of gradient coils, powered from a power supply, through which current flows in series when in operation and which generate, in a predefined volume under examination, a gradient magnetic field that varies at least approximately in linear fashion with position in one direction, is characterized in that each gradient coil (A, B) has one set with at least one first winding zone (S1) and one set with at least one second winding zone (S2), which have terminals (16, 17; 18, 19) that are separate from one another, in such a way that the winding zones can be easily be connected to and separated from one another in varying ways. The user can thereby modify the properties of the gradient system.

Abstract: In an NMR magnet system for generating a highly homogeneous magnetic field of high field strength, with at least one superconducting magnet coil which is arranged in a first chamber of a cryostat in supercooled liquid helium at a temperature of less than 4.2K, with the cryostat having at least one further chamber containing liquid helium that is essentially at atmospheric pressure with a temperature of approximately 4.2K, the first chamber is connected to the further chamber in such a way that the supercooled liquid helium located in the first chamber is also essentially at atmospheric pressure. A refrigerator with which the liquid helium can be cooled to a temperature T<<4.2K, especially to T.apprxeq.1.8-2.3K, is provided in the first chamber.

Abstract: A nuclear magnetic resonance spectrometer, in particular a nuclear spin tomograph serving to investigate biological samples, comprising a magnetic coil for generating a substantially homogeneous magnetic field in a volume under examination, and a set of shim coils for eliminating any remaining inhomogeneities of the magnetic field is characterized in that at least one additional electric conductor, preferably an additional shim coil, is provided which may be arranged in the volume under examination, in the direct vicinity of the sample, that the additional conductor is designed in such a way that it will generate an inhomogeneous magnetic field when loaded with current, and that it can be loaded with currents of a type generating inhomogeneous magnetic fields which will eliminate, at least partially, and in a selected area in the sample, local field inhomogeneities resulting from susceptibility variations within the sample, for example. This enables the accuracy of the spectroscopy results to be improved.

Abstract: A magnet coil (30) comprises at least one first winding made of wire (34) which is superconductive at operating temperature and at least one second winding made of normally conductive wire (36). In addition, means are provided for supplying a current into the second winding, which is completely dead during superconductive operation of the magnet coil (30), when at least certain sections of the superconductive wire (34) assume the normally conductive state.In order to accelerate the spatial propagation of this transition in the magnet coil (30) and at the same time to provide the possibility to use low-cost wires having a relatively small proportion, related to the cross-sectional area, of normally conductive material, the first and the second winding are connected in parallel electrically.