摘要:
A method is provided for manufacturing a Bitter coil by indium welding and a solenoid magnet obtained by using this method. The Bitter disks or parts of such disks are welded with an indium filler, deposited preferably electrolytically on the portions to be assembled together.
摘要:
The cylindrical permanent magnet device includes at least one basic structure (10) having a longitudinal axis (z) and a set (20) of coaxial magnetized structures (21, 22, 23, 24) that are in the form of non-contiguous rings of axis that is the longitudinal axis (z) and that are disposed on the same side of the basic structure (10), defining an exterior surface perpendicular to the longitudinal axis (z) to produce a magnetic field (B0) outside the magnet device in an exterior area of interest (3) situated at a predetermined distance from the exterior surface along the longitudinal axis (z). At least one of the coaxial magnetized structures (21, 22, 23, 24) in the form of rings is divided into components in the form of non-contiguous identical sectors. The basic structure (10) and the set (20) of coaxial magnetized structures (21, 22, 23, 24) in the form of rings are magnetized in the same direction (M) to create in the exterior area of interest (3) an induced magnetic field (B0) that is homogeneous or that has a constant gradient and that is oriented at a predetermined angle (θ2) relative to the longitudinal axis (z).
摘要:
Disclosed is a compact superconducting magnet device for generating an intense and homogeneous magnetic field component Bz along an axis Oz in a zone of interest ZI successively includes, starting from the axis Oz, at least three coaxial superconducting helical coils formed around circular cylinder sections of axis Oz delimited by end circles. The lateral ends of the helical coils are arranged, to within the thickness of the coils, in the vicinity of one same sphere of radius c whose centre O is placed on the axis Oz at the centre of the zone of interest ZI and which encompasses the magnetic device assembly. The azimuthal current densities j1, j2, j3 of the helical coils are alternately of opposite sign. The lengths of the helical coils are of decreasing length.
摘要:
Disclosed is a device for generating a homogeneous magnetic field component Bz along an axis Oz in a spherical zone of interest of centre O and radius r includes at least one first ring of axis Oz in magnetic material with radial magnetization oriented in a first direction and extending around an opening giving access to the zone of interest ZI, a second ring of axis Oz in magnetic material with radial magnetization oriented in the first direction and offset along axis Oz from the first ring and the zone of interest ZI, the inner radius and the outer radius of the second ring respectively being smaller than the inner radius and outer radius of the first ring.
摘要:
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). Between an exterior cryogenic enclosure (102) and the annular cylindrical space (130) a cylindrical screen (104) is disposed along the axis Z comprising a conductive material of low resistance and low magnetoresistance such that negligible induced currents are generated in the exterior cryogenic enclosure (102) while the eddy currents induced in the cylindrical screen (104) contribute to reinforcing the gradients produced by the solenoidal gradient coils (111-122).
摘要:
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.
摘要:
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.
摘要:
A system is provided for regulating the field of a high homogeneity magnet. The fluid used for cooling the main magnet is placed in thermal contact with a high homogeneity auxiliary magnet in which is placed an NMR probe which controls the current supply to the two magnets connected in series.
摘要:
A block of magnetized material for adjusting and correcting a magnetic field produced by a magnet provides adjustable correction by modifying the orientation of the magnetic moment of the block with respect to the field. A device which includes an intermediate member rotatably mounted in an orientable support and a fixing member rotatably mounted in the intermediate member makes it possible to orient a preferred direction of the block in a predetermined direction. This results in modification of magnetic disturbances produced by the block in the zone of interest of the magnet. Quantization of pointing of the orientable support is obtained by means of graduated index marks on the support, on the intermeidate member and on the fixing member.
摘要:
A coreless solenoidal magnet is provided formed by a Bitter coil with improved field homogeneity. According to the invention the tie rods of the stack of disks are used for bringing the current back towards one of the axial ends of the magnet without creating a parasite field.