Abstract: The magnetized structure that induces in a central area of interest a homogeneous magnetic field oriented along a longitudinal axis (z) of the structure comprises first and second magnetized rings (111, 121) disposed symmetrically relative to a plane (P) that is perpendicular to said longitudinal axis (z) and that contains said central area of interest, and one median annular magnetized structure (330) disposed between the first and second magnetized rings (111, 121) and also disposed symmetrically relative to the plane (P) of symmetry. The first magnetized ring (111) is magnetized radially relative to the longitudinal axis (z) with divergent magnetization, the second magnetized ring (121) is magnetized radially relative to the longitudinal axis (z) with convergent magnetization, and the median annular magnetized structure (330) is magnetized along the longitudinal axis (z).

Abstract: The nuclear magnetic resonance machine comprises a device (101) for creating an intense main magnetic field B0 in a useable interior space (109) in the form of a tunnel with axis Z, a device for radio-frequency excitation and processing of radio-frequency signals emitted in response by a body (150) placed in the useable interior space (109), and a set (110) of solenoidal gradient coils for superimposing on the intense magnetic field B0 components of an additional magnetic field, the gradient coils (111-122) being incorporated into tubes that are disposed in a annular cylindrical space (130).

Abstract: The device for creating a uniform magnetic field in a zone of interest, in particular for nuclear magnetic resonance and magnetic resonance imaging, comprises an arrangement of superconductor coils disposed around a longitudinal axis (z) of the zone of interest. This arrangement of coils comprises at least one stack of a set of modular elements (8) distributed along the longitudinal axis (z), each modular element (8) comprising a rectangular-section conductor of superconductor material that is wound in continuous manner to form of a double pancake coil. The double pancake coil comprises a first single plane pancake coil (10) in the form of a spiral, a second single plane pancake coil (20) in the form of a spiral juxtaposed with and parallel to the first single pancake coil (10), and a transition segment (30) without any internal junction between the first and second single pancake coils (10, 20).

Abstract: The magnetic resonance imaging system includes an exterior cryogenic enclosure containing a device for creating an intense main magnetic field in a usable interior space in the form of a tunnel, a radio-frequency excitation device, a set of solenoid gradient windings placed in a cylindrical annular space around the interior space and electronic control circuits. The toroidal cryogenic enclosure includes concentrically a vacuum enclosure defining an interior cylindrical space at room temperature in which the set of solenoid gradient windings is placed, at least one thermal screen maintained at a temperature in the range 20 K to 80 K, a cold box at a temperature less than 5 K, and a former for supporting the device for creating an intense main magnetic field.

Abstract: The nuclear magnetic resonance machine comprises a device (101) for creating an intense main magnetic field B0 in a usable interior space (109) in the form of a tunnel with axis Z, a radio-frequency excitation device that also processes radio-frequency signals emitted in response by a body (150) placed in the usable interior space (109), and a set (110) of solenoidal gradient coils for superimposing on the intense magnetic field B0 components of a additional magnetic field, the gradient coils (111-122) being incorporated into tubes disposed in an annular cylindrical space (130).

Abstract: The nuclear magnetic resonance machine comprises a device (101) for creating an intense main magnetic field B0 in a useable interior space (109) in the form of a tunnel with axis Z, a device for radio-frequency excitation and processing of radio-frequency signals emitted in response by a body (150) placed in the useable interior space (109), and a set (110) of solenoidal gradient coils for superimposing on the intense magnetic field B0 components of an additional magnetic field, the gradient coils (111-122) being incorporated into tubes that are disposed in a annular cylindrical space (130).

Abstract: The nuclear magnetic resonance machine comprises a device (101) for creating an intense main magnetic field B0 in a usable interior space (109) in the form of a tunnel with axis Z, a radio-frequency excitation device that also processes radio-frequency signals emitted in response by a body (150) placed in the usable interior space (109), and a set (110) of solenoidal gradient coils for superimposing on the intense magnetic field B0 components of a additional magnetic field, the gradient coils (111-122) being incorporated into tubes disposed in an annular cylindrical space (130).

Abstract: The device for creating a uniform magnetic field in a zone of interest, in particular for nuclear magnetic resonance and magnetic resonance imaging, comprises an arrangement of superconductor coils disposed around a longitudinal axis (z) of the zone of interest. This arrangement of coils comprises at least one stack of a set of modular elements (8) distributed along the longitudinal axis (z), each modular element (8) comprising a rectangular-section conductor of superconductor material that is wound in continuous manner to form of a double pancake coil. The double pancake coil comprises a first single plane pancake coil (10) in the form of a spiral, a second single plane pancake coil (20) in the form of a spiral juxtaposed with and parallel to the first single pancake coil (10), and a transition segment (30) without any internal junction between the first and second single pancake coils (10, 20).

Abstract: In order to produce field strength gradients (x,y) for a NMR machine, the curve-shaped gradients are substituted by coils arraigned in tubes. Said tubes are distributed on the annular circumference (6) of the examination space of the tunnel NMR machine. Said invention makes it possible to produce at request field strength gradients in all necessary directions by providing each tube with the same set of coil elements and supplying them with selected currents.

Abstract: In order to produce field strength gradients (x,y) for a NMR machine, the curve-shaped gradients are substituted by coils arraigned in tubes. Said tubes are distributed on the annular circumference (6) of the examination space of the tunnel NMR machine. Said invention makes it possible to produce at request field strength gradients in all necessary directions by providing each tube with the same set of coil elements and supplying them with selected currents.

Abstract: A permanent magnet for nuclear magnetic resonance imaging that provides an intense and highly homogeneous magnetic magnetic field is disclosed. The magnet is made up of a set of rings having two sub-sets of rings of permanently magnetized polygonal blocks, wherein the rings of a sub-set of rings are substantially concentric. In addition, the rings of the two sub-sets are complementary in terms of magnetization. Each ring of a sub-set is separated from its complementary ring by a space that is substantially the same for all pairs of complementary rings. The rings have a regular polygonal structure and are made up of blocks that also have regular polygonal shapes.

Abstract: Inhomogeneities in a magnetic field are corrected by means of openings of square or polygonal cross-section in the periphery of the magnet. Permanent magnets required for obtaining the desired correction are lodged in the openings. Thus, the orientation of the permanent magnets can only assume a limited number of values, which simplifies the calculation to determine the positions of the magnets used to correct the inhomogeneity of the magnetic field. It is mainly applicable to the correction of inhomogeneity of the magnetic field of a magnet used in nuclear magnetic resonance imaging.

Abstract: To make a gradient coil, it is decided to cut the conductors of this coil out of a plate. Thus flat conductors can be used. This helps reduce the self-inductance of the coil to be made. The coil is, moreover, optimized. A calculation is made of the coefficients of the breakdown into spherical harmonics of the field created by the coil. The coil's structure is modified so as to cancel those coefficients of this breakdown which generate a divergence in this field. It is shown that, in this way, the solution is an optimum one.

Abstract: In a system of compensated gradient coils, gradient coils mounted on two mandrels coaxial with an examining region of an NMR machine have useful conductors distributed in such a way that when a nomimal current flows through them they induce a zero magnetic vector potential in preferred regions of the space in which the production of undesirable eddy currents is to be prevented.

Abstract: A substantially spherical magnet comprising two facing hemispherical, magnetized and hollow structures is proposed to produce a uniform induction field going from one structure to the other. By spacing sufficiently apart both structures, an equatorial opening is created to provide for the introduction of bodies to be subjected to said induction. It was shown that homogeneity may be reached at a given order if each structure is comprised of rings, shaped like a portion of a spherical crown, obtained by juxtaposition of magnetic blocks, and if the number of blocks in each ring is higher than or equal to four times the number of rings in each structure.

Abstract: In a nuclear magnetic resonance imaging installation, monitors of the cathode tube type are shielded from the effect of an intense magnetic field. For this purpose, the installation according to the invention has a flat coil which creates a second magnetic field, the direction of which is opposite to that of the intense magnetic field.

Abstract: A cylindrical permanent magnet with a longitudinal induced field may be achieved by creating on either side of a zone of interest two annular structures magnetized on the one hand radially with respect to the cylinder axis and on the other hand antisymetrically with respect to the zone of interest. The annular structures may be achieved by arrangements of blocks on polygonal contours. In order to optimize fabrication, the number of blocks in each ring must be higher or equal to four times the number of rings in each structure. The magnet applies particularly to the field of imaging by nuclear magnetic resonance wherein the control logistics had originally been designed for longitudinal induction fields.

Abstract: Industrial problems concerning the production of a field of uniform and traverse induction are solved by providing a cylindrical magnet with magnetic blocks of which the internal magnetization is either radial or tangential to the cylinder. Such an arrangement facilitates the fabrication and the magnetization of the blocks. A radial or tangential magnetization distribution produces a transverses field only if the magnetization modulus varies respectively with the cosine or the sine of the localization angle of the block with respect to the direction of induction to be produced. By combining both structures, it is even possible to obtain a magnet having a zero bipolar moment. The variation of the magnetization modulus is obtained by providing composite magnetic bricks. They comprise plates of magnetic materials which are coupled to non-magnetic plates in a proportion dependeing on the reduction of magnetization to be achieved. Such a magnet applies to imaging by nuclear magnetic resonance in the medical field.

Abstract: Demagnetization effects in any magnetic block are avoided by using a mixed magnetic material comprising a predetermined proportion of permanently magnetizable magnetic material and of non-magnetic material. The proportion is adjusted as a function of the ratio between the demagnetizing excitation and a so-called cut-off excitation of the material, for which the magnetization of the material drops considerably. Application to imaging by nuclear magnetic resonance.

Abstract: A method of measuring the strength of a DC current and a device for implementing this method are provided, forming an NMR shunt for measuring high currents. A magnetic coil is placed in series in the circuit in which the current to be measured flows, the temperature of the magnet is stabilized and the magnetic field is measured in the center of the magnet using an NMR probe.