Abstract: A shielded and open magnetic resonance imaging (MRI) magnet having two spaced-apart, generally toroidal-shaped superconductive coil assemblies. Each coil assembly has a coil housing containing a generally annular-shaped superconductive main and a radially-outwardly spaced-apart shielding coil carrying electric currents in opposing directions. Preferably, supplemental shielding is provided with the addition of: a generally annular permanent magnet configuration internal to, or external of, the coil housings; a generally-non-permanently-magnetized external ferromagnetic shield having at least a portion positioned longitudinally between the coil housings, an external resistive coil; or combinations thereof.

Abstract: An open magnetic resonance imaging (MRI) magnet having longitudinally spaced-apart superconductive main coils surrounded by a dewar containing a cryogenic liquid (e.g., liquid helium) and boiled-off cryogenic gas (e.g., helium vapor). A condenser is in physical contact with the boiled-off vapor and is in thermal contact with a cold stage of a cryocooler coldhead so as to re-liquefy the vapor. This allows the coils to be surrounded by a single (not double) thermal shield which allows the coils structurally to be located closer to the magnet's open space which reduces magnet cost by reducing the amount of coil needed for the same-strength magnetic field.

Abstract: A superconductive lead assembly for a superconductive device (e.g., magnet) cooled by a cryocooler coldhead having first and second stages. A first ceramic superconductive lead has a first end flexibly, dielectrically, and thermally connected to the first stage and a second end flexibly, dielectrically, and thermally connected to the second stage. A jacket of open cell material (e.g., polystyrene foam) is in general surrounding compressive contact with the first ceramic superconductive lead, and a rigid support tube generally surrounds the jacket. This protects the first ceramic superconductive lead against shock and vibration while in the device. The rigid support tube has a first end and a second end, with the second end thermally connectable to the second stage.

Abstract: A superconductive lead assembly for a superconductive device (e.g., magnet) cooled by a cryocooler coldhead having first and second stages. A first ceramic superconductive lead has a first end flexibly, dielectrically, and thermally connected to the first stage and a second end flexibly, dielectrically, and thermally connected to the second stage. A jacket of open cell material (e.g., polystyrene foam) is in general surrounding compressive contact with the first ceramic superconductive lead, and a rigid support tube generally surrounds the jacket. This protects the first ceramic superconductive lead against shock and vibration while in the device. The rigid support tube has a first end and a second end, with the second end thermally connectable to the second stage.

Abstract: A superconductive rotor, such as an electric generator rotor, has a cylindrical-shaped solid (e.g., iron) core having a pair of diametrically-opposed and longitudinally-extending slots. A longitudinally-extending, racetrack-shaped superconductive coil surrounds the solid core and has straight portions located in the slots. A longitudinally extending, racetrack-shaped thermal shield generally encloses the superconductive coil and has generally straight portions located in the slots. The thermal shield is generally spaced apart from the superconductive coil and from the solid core. A pair of end shafts are each attached to the solid core and are spaced apart from the thermal shield. One end shaft has a cryogen transfer coupling for cooling the superconductive coil, preferably with gaseous helium.

Abstract: A magnet including spaced-apart first and second pole pieces with generally opposing first and second pole faces. The first pole face has an axis extending generally towards the second pole face and has a surface region which includes at least two frustoconical surfaces. The frustoconical surfaces are generally coaxially aligned about the axis, and radially-adjacent frustoconical surfaces abut each other. In a second embodiment, points on the surface region located an identical radial distance from the axis are also located a common axial distance along the axis, and a graph of axial distance along the axis versus radial distance from the axis for such points is a curve having a continuous slope with at least two sign reversals. Such contoured pole faces allow for a smoother magnetic field to better reduce axisymmetric magnetic field inhomogeneity.

Abstract: A superconducting device, such as a superconducting rotor for a generator or motor or a superconducting magnet for a magnetic resonance imaging machine, etc. A vacuum enclosure surrounds and is spaced apart from a superconductive coil. Apparatus supports the coil in the enclosure during operation of the device, such apparatus including a first thermally insulative honeycomb assemblage positioned between the coil and the enclosure. In a first preferred construction, the first honeycomb assemblage is positioned between and connected to the coil and a thermal shield, and a second honeycomb assemblage is positioned between and connected to the shield and the enclosure. In a second preferred construction, the second honeycomb assemblage is replaced with a first suspension strap.

Abstract: An open magnetic resonance imaging (MRI) magnet having first and second spaced-apart superconductive coil assemblies each including a toroidal-shaped coil housing containing a superconductive main coil. A generally annular-shaped resistive coil is associated with each coil assembly, being generally coaxially aligned with the associated coil assembly and being spaced radially inward and radially apart from the associated coil assembly's superconductive main coil. The resistive coils overcome the gross magnetic field distortions in the imaging volume of the superconductive main coils (created by the open space between the magnet's superconductive coil assemblies) to produce a magnetic field of high uniformity within the imaging volume.

Abstract: A superconductive magnet with magnetic shielding has an annularly-cylindrical-shaped housing whose first end wall and outer cylindrical wall are magnetizable (e.g., iron) walls and whose inner cylindrical wall is a non-magnetizable wall. At least one main superconductive coil is positioned within the housing and carries an electric current in a first (e.g., clockwise) direction. An annular first permanent magnet is positioned outside the housing longitudinally proximate the first end wall. The first permanent magnet has a number of equivalent ampere turns and has a magnetic field direction oriented parallel to the axis pointing towards the second end wall so that its magnetic field longitudinally pulls the stray magnetic field of the superconductive coil(s), which leaves the magnet's bore, inward to be captured by the iron first end wall.

Abstract: A superconductive magnet with magnetic shielding has an annularly-cylindrical-shaped housing whose first end wall and outer cylindrical wall are magnetizable (e.g., iron) walls and whose inner cylindrical wall is a non-magnetizable wall. At least one main superconductive coil is positioned within the housing and carries an electric current in a first (e.g., clockwise) direction. A first resistive (e.g., copper) deflection coil is positioned outside the housing radially proximate the outer cylindrical wall and longitudinally closer to the first end wall than to a midpoint located between the two end walls. The first deflection coil carries an electric current in an opposite direction to the first direction so that its magnetic field longitudinally pushes the stray magnetic field of the superconductive coil(s), which leaves the magnet's bore, inward to be captured by the iron first end wall.

Abstract: A superconductive switch has a first layer of a superconductive coil wire wound around a shaft clockwise from the first end to the middle and counterclockwise from the middle to the second end. A second layer of the wire is wound around the first layer in identical fashion. A third layer of the wire is wound around the second layer counterclockwise from the first end to the middle and clockwise from the middle to the second end. An electrical heater is located between the first and second layers, and a stratum of electrical insulation, discrete from that of the coil wire, is located between the second and third layers.

Abstract: An open magnetic resonance imaging (MRI) magnet having two generally toroidal-shaped superconductive coil assemblies spaced apart by generally spaced-apart and generally parallel inter-coil-assembly posts. Each coil assembly has associated with it a generally annular-shaped superconductive shielding assembly and at least two spaced-apart assembly posts each having one end attached to the coil assembly and another end attached to the shielding assembly The shielding coil within the shielding assembly has an inner diameter greater than the outer diameter of the main coil within the coil assembly. A cryocooler coldhead cools the entire magnet. Magnetic shielding is achieved while maintaining the openness of the open magnet.

Abstract: A superconductive magnet having a superconductive coil located within a thermal shield located within a vacuum enclosure. A cryocooler coldhead's first stage is in solid-conductive thermal contact with the thermal shield, and its second stage is in solid-conductive thermal contact with the superconductive coil. A magnet re-entrant support assembly includes an outer support cylinder located between the vacuum enclosure and the thermal shield and includes an inner support cylinder located between the thermal shield and the superconductive coil. The outer support cylinder's first end is rigidly connected to the vacuum enclosure, and its second end is rigidly connected to the thermal shield. The inner support cylinder's first terminus is rigidly connected to the thermal shield near the outer support cylinder's second end, and its second terminus is located longitudinally between the outer support cylinder's first and second ends and is rigidly connected to the superconductive coil.

Abstract: A magnet including spaced-apart first and second pole pieces with generally opposing first and second pole faces. The first pole face has an axis extending generally towards the second pole face and has a generally circular shim tray generally coaxially aligned with the axis and attached to the first pole face. The circular shim tray has shims each with a shape of generally a trapezoid when viewed facing the first pole face. The trapezoidal shaped shims may be arranged on the circumferences of imaginary concentric circles on the circular shim trays, with trapezoids on the same circumference having generally the same trapezoidal shape and with trapezoids on different circumferences having generally different trapezoidal shapes, to provide a smoother magnetic field to better reduce 3D (three-dimensional) magnetic field inhomogeneity.

Abstract: A cooling system for a superconductive magnet. A dewar, located outside the magnet, includes a vacuum jacket hermetically connected to the magnet's vacuum enclosure and includes liquid helium located within the vacuum jacket. A thermal busbar is located within and spaced apart from the hermetically connected vacuum jacket and vacuum enclosure. The thermal busbar has a first end located within the vacuum jacket and a second end located within the vacuum enclosure and in thermal contact with the magnet's superconductive coil. A cryocooler coldhead, located outside the vacuum enclosure, has a housing located outside the vacuum jacket and has a cold stage extending from the housing to inside the vacuum jacket to re-liquefy any helium boiled-off in cooling the magnet 10.

Abstract: This invention relates to an apparatus and method for providing passive shimming for a superconducting magnet of the type that has a relatively small imaging volume. Such structures of this type, generally, provide the proper amount of passive shimming for a relatively small imaging volume.

Abstract: An open magnet having two magnet assemblies arranged in a spaced-apart, parallel relationship to define a working space therebetween is provided for magnetic resonance imaging. Each assembly has an annular superconductive coil and a ferromagnetic field enhancer encircled by the superconductive coil. The field enhancers are substantially cylindrical ferromagnetic pole pieces which are encircled by a respective one of the superconductive coils. The magnet assemblies are attached to a C-shaped support frame which is rotatively mounted to a pedestal member. The frame can thus be rotated between vertical and horizontal imaging positions. The field enhancers are shaped so as to maximize homogeneity in the imaging volume while keeping their weight and volume to a minimum. The specific shape of the field enhancers is determined with a nonlinear optimization design method.

Abstract: A superconducting magnet includes a cryocooler coldhead, a sleeve assembly, and a superconducting coil assembly. The sleeve assembly includes a flexible bellows and a sleeve tube and is attached to the superconducting coil assembly so that it may be retracted about one-eighth of an inch breaking thermal contact of the sleeve assembly with the coil assembly's magnet cartridge and thermal shield while remaining hermetically connected to the coil assembly's vacuum enclosure. The coldhead's housing is attached to the sleeve assembly so that the coldhead's first and second stage make unconnected thermal contact with the sleeve assembly. By first retracting the sleeve assembly, the coldhead may be removed therefrom without room temperature air forming an ice ball on the surfaces of the sleeve assembly and without a heat load being transferred to quench the superconducting coil assembly. This permits continuous magnet operation using dual coldheads and dual sleeve assemblies.

Abstract: A pancake magnetic resonance imaging (MRI) magnet having a superconductive coil assembly including a toroidal-shaped coil housing containing a superconductive main coil set and a radially spaced-apart superconductive supplemental coil set. The main coil set includes a first main coil located radially towards the circumferential outside surface which faces away from the bore, and the supplemental coil set includes three radially spaced-apart supplemental coils located radially towards the circumferential outside surface which faces towards the bore. The first main coil and the middle supplemental coil each carry an equal electric current in a first direction while the other two supplemental coils each carry the same electric current in the opposite direction. Such coil arrangement produces an imaging volume longitudinally wider than the longitudinal thickness of the magnet.

Abstract: A magnetic resonance imaging (MRI) magnet having an annularly cylindrical-shaped vacuum enclosure with a longitudinal axis, first and second longitudinal ends, a first larger diameter bore extending from the first towards the second longitudinal end, and a second smaller diameter bore extending from the second longitudinal end to the first bore. First and second superconductive coils are placed in the vacuum enclosure with the first coil generally circumferentially surrounding the first bore and the second coil circumferentially surrounding the second bore, wherein the radial distance of the radially innermost portion of the second coil from the axis is smaller than the radius of the first bore. The first longitudinal end of the vacuum enclosure fits over a patient's shoulders with the patient's head at least partially passing through the first bore and extending into the second bore for MRI brain imaging.