Commissariat &#xc0; L'&#xc9;nergie Atomique Et Aux &#xc9;nergies Alternatives

Commissariat a L'energie Atomique

Guy Aubert

Dimitrios Sakellariou

Cédric Hugon

Cedric Hugon

Dimitri Sakellariou

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 two 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 center O is placed on the axis Oz at the center of the zone of interest ZI and which encompasses the magnetic device assembly. The azimuthal current densities j, jof the helical coils are of opposite sign. The lengths of the helical coils are of decreasing length.

Superconducting magnet device

Disclosed is a device for generating a homogeneous magnetic field component Bz along an axis Oz in a spherical zone of interest of center 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.

Permanent magnet device for generating an offset uniform magnetic field

The cylindrical permanent magnet device includes at least one basic structure () having a longitudinal axis (z) and a set () of coaxial magnetized structures () 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 (), defining an exterior surface perpendicular to the longitudinal axis (z) to produce a magnetic field (B) outside the magnet device in an exterior area of interest () situated at a predetermined distance from the exterior surface along the longitudinal axis (z). At least one of the coaxial magnetized structures () in the form of rings is divided into components in the form of non-contiguous identical sectors. The basic structure () and the set () of coaxial magnetized structures () in the form of rings are magnetized in the same direction (M) to create in the exterior area of interest () an induced magnetic field (B) that is homogeneous or that has a constant gradient and that is oriented at a predetermined angle (&#x3b8;) relative to the longitudinal axis (z).

Cylindrical permanent magnet device generating a controlled magnetic field at a distance from the surface thereof

Device for generating an orientable and locally uniform magnetic field, including N&#x2267;3 identical assemblies of cylindrical coils, each assemblies having a first and a second coil, the coils being coaxial with an axis oriented along a direction z and arranged symmetrically on either side of the plane, with a gap in the axial direction, the assemblies arranged such that their outlines in a plane xy perpendicular to the z-axis are regularly spaced along a circle of center O and of radius a&#x3e;0, so to leave a central free space. A supply system supplies the coils with a current set to obtain, at the center of the device, a magnetic field having the desired orientation. The device may include two pairs of cylindrical coils having a common axis oriented in said z-direction and passing through the center of the circle, these coils being arranged symmetrically on either side of said xy-plane.

Device for generating an orientable and locally uniform magnetic field

A magnetized structure that induces in a central area of interest a homogeneous magnetic field of predetermined orientation relative to a longitudinal axis (z) of the structure comprises at least two magnetized rings () disposed symmetrically relative to a plane (P) that is perpendicular to the longitudinal axis (z) and that contains the central area of interest, and at least one median annular magnetized structure disposed at least partly between the two magnetized rings () and also disposed symmetrically relative to the plane (P) of symmetry, one of the two magnetized rings () being magnetized radially relative to the longitudinal axis (z) with divergent magnetization and the other of the two magnetized rings () being magnetized radially relative to the longitudinal axis (z) with convergent magnetization, and the median annular magnetized structure being magnetized with an orientation different from that of the magnetization of the two magnetized rings (). The median annular magnetized structure comprises at least one magnetized ring () having a magnetization distribution of orientation that varies as in Halbach dipoles and the first two magnetized rings () and the median annular magnetized structure are each divided into individual components in the form of regularly distributed identical sectors.

Magnetised structure inducing a homogeneous field, in the centre thereof, with a pre-determined orientation

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 () 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 () disposed between the first and second magnetized rings () and also disposed symmetrically relative to the plane (P) of symmetry. The first magnetized ring () is magnetized radially relative to the longitudinal axis (z) with divergent magnetization, the second magnetized ring () is magnetized radially relative to the longitudinal axis (z) with convergent magnetization, and the median annular magnetized structure () is magnetized along the longitudinal axis (z). The median annular magnetized structure () is divided into at least two slices (A,B,A,B) along the longitudinal axis (z) and the first and second magnetized rings () and the various slices (A,B,A,B) of the median magnetized structure () are each divided into identical components in the form of regularly distributed sectors.

Assembly of magnetised coaxial structures inducing a longitudinal homogeneous field in the centre thereof

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 j, j, jof the helical coils are alternately of opposite sign. The lengths of the helical coils are of decreasing length.

Compact superconducting magnet device

A magnetic resonance imaging system having an exterior cryogenic enclosure containing a device for creating an intense main magnetic field in a usable interior tunnel space an RF exciter, a set of solenoid gradient windings in a cylindrical space around the interior tunnel space and electronic control circuits. The cryogenic enclosure includes an interior cylindrical space vacuum at room temperature having the set of windings therein, at least one thermal screen in a temperature range of 20&#xb0; K to 80&#xb0; K, a cold box below 5&#xb0; K, and a former supporting the exciter for creating an intense main magnetic field. To reduce acoustic noise and cryogenic losses, an additional envelope is between the set of windings and the vacuum enclosure, the additional envelope being of a conductive material having electrical resistivity at least 7&#xd7;10&#x3a9;&#xb7;m and having a characteristic frequency no more than the characteristic frequencies of each of the other components of the exterior cryogenic enclosure.

NMR imaging system with reduced cryogenic losses and reduced acoustic noise

The nuclear magnetic resonance machine comprises a device () for creating an intense main magnetic field Bin a useable interior space () 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 () placed in the useable interior space (), and a set () of solenoidal gradient coils for superimposing on the intense magnetic field Bcomponents of an additional magnetic field, the gradient coils (-) being incorporated into tubes that are disposed in a annular cylindrical space (). Between an exterior cryogenic enclosure () and the annular cylindrical space () a cylindrical screen () 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 () while the eddy currents induced in the cylindrical screen () contribute to reinforcing the gradients produced by the solenoidal gradient coils (-).

NMR machine comprising solenoid gradient coils

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 () distributed along the longitudinal axis (z), each modular element () 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 () in the form of a spiral, a second single plane pancake coil () in the form of a spiral juxtaposed with and parallel to the first single pancake coil (), and a transition segment () without any internal junction between the first and second single pancake coils (). Each single pancake coil () has a connection end () situated at the outer peripheral portion of the pancake coil, and the transition segment () enables an offset to be provided along the longitudinal axis (z) that is not less than the transverse dimension of the conductor along said axis.

Method and device for generating a homogeneous magnetic field in an area of interest, especially for NMR imaging

The nuclear magnetic resonance machine comprises a device () for creating an intense main magnetic field Bin a usable interior space () 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 () placed in the usable interior space (), and a set () of solenoidal gradient coils for superimposing on the intense magnetic field Bcomponents of a additional magnetic field, the gradient coils (-) being incorporated into tubes disposed in an annular cylindrical space (). Between an exterior cryogenic enclosure () and the annular cylindrical space () a cylindrical screen () 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 () while the eddy currents induced in the cylindrical screen () contribute to reinforcing the gradients produced by the solenoidal gradient coils (-).

NMR machine comprising solenoid gradient coils which are incorporated into tubes

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 () 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.

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Poitiers, France

Guy Aubert