Abstract: A method of designing and manufacturing a magnetic separation apparatus. Past separators generally had poor power efficiency, poor throughput performance, and/or were bulky. Designing the magnetic separator of the present invention involves selecting a diameter and height for a separation container and superconducting coil by optimizing at least one parameter from a group of parameters. The magnetic separation apparatus includes a superconducting electromagnet and separation container having a diameter of about 60 inches, a height of about 40 inches, an inlet port, an outlet port, and removable matrix modules. The electromagnet generates a magnetic field strength within the separation container of greater than 3 Tesla. The optimized separation container volume, the high magnetic field strength, and the matrix modules allow the magnetic separation apparatus to have greatly increased slurry processing capacity.

Abstract: A refrigeration system includes a dewar and a refrigerator/liquefier which meets the variable demands of a superconducting magnet within the dewar. The system is sized to meet average loads over a defined duty cycle, and is variably operable to meed demands. In the preferred embodiment, a first supply of fluid circulates through a "condenser" element positioned in a dewar ullage to liquefy a separate supply of fluid in the dewar, and to refrigerate a pulsed cryogenic load therein, such as a superconducting magnet. A portion of the first supply of fluid may be diverted to refrigerate a second pulsed cryogenic load, such as magnet current leads permanently connected to the magnet. The dewar includes a cold gas vapor storage chamber separate from the dewar ullage, and the chamber is preferably located within the inner core of a solenoid superconducting magnet for compact and thermally efficient design. Responsive, independent adjustment of refrigeration to pulsed cryogenic loads is made possible.

Abstract: A refrigeration system includes a dewar and a refrigerator/liquefier which meets the variable demands of a superconducting magnet within the dewar. The system is sized to meet average loads over a defined duty cycle, and is variably operable to meed demands. In the preferred embodiment, a first supply of fluid circulates through a "condenser" element positioned in a dewar ullage to liquefy a separate supply of fluid in the dewar, and to refrigerate a pulsed cryogenic load therein, such as a superconducting magnet. A portion of the first supply of fluid may be diverted to refrigerate a second pulsed cryogenic load, such as magnet current leads permanently connected to the magnet. The dewar includes a cold gas vapor storage chamber separate from the dewar ullage, and the chamber is preferably located within the inner core of a solenoid superconducting magnet for compact and thermally efficient design. Responsive, independent adjustment of refrigeration to pulsed cryogenic loads is made possible.

Abstract: A method of manufacturing a helium containment vessel for use with a pulsed superconducting magnetic separator system is described. The containment vessel includes a superconducting coil positioned within the cryogenic containment vessel for providing a magnetic field. The containment vessel includes a relatively thin metallic inner tube for holding liquid helium and the coil. The containment vessel also includes a relatively thick outer tube encompassing the inner tube with a relatively rigid insulative spacer positioned between the inner and outer tubes so that the tubes are not in contact with each other. The outer tube is predominantly metallic and has at least one joint formed of insulative material to prevent the outer tube from forming a low electrical resistance loop.

Abstract: A cryogenic containment vessel for use with a pulsed superconducting magnet system includes a superconducting coil positioned within the cryogenic containment vessel for providing a magnetic field. The containment vessel includes a relatively thin metallic inner tube for holding liquid helium and the coil. The containment vessel also includes a relatively thick outer tube encompassing the inner tube with a relatively rigid insulative spacer positioned between the inner and outer tubes so that the tubes are not in contact with each other. The outer tube is predominantly metallic and has at least one joint formed of insulative material to prevent the outer tube from forming a low electrical resistance loop. The inner tube provides a vacuum seal and the outer tube provides structural support for the inner tube so that eddy current losses resulting from ramping of the current to the coil are reduced. A method of fabricating the containment vessel is also disclosed.

Abstract: Process of manufacturing a cryogenic regenerator including a plurality of channels for conducting a working fluid, including the steps of providing a cylindrical forming member having a longitudinal axis and a plurality of peripheral slots displaced axially and oriented substantially parallel to the longitudinal axis of the cylindrical forming member, or having a continuous spiral peripheral slot of sufficiently small pitch such that the convolutions thereof are oriented substantially parallel to such longitudinal axis; providing epoxy which is relatively flexible upon hardening, loading the epoxy with thermally conductive material for enhancing the radial thermal conductivity of the cryogenic regenerator, and applying the epoxy to the periphery of the cylindrical forming member to fill the plurality of slots or the spiral peripheral slot with the epoxy and to form a radial layer of the epoxy of a generally first radial thickness allowing the epoxy to harden and thereafter reducing the radial thickness of the

Abstract: A pulsed superconducting magnet system includes a vacuum vessel and a cryogenic containment vessel assembly disposed within the vacuum vessel. A superconducting coil is positioned within the cryogenic containment vessel assembly for providing a magnetic field. The vessel assembly includes a helium vessel including a relatively thin metallic inner tube for holding liquid helium and the coil. The helium vessel also includes a relatively thick outer tube encompassing the inner tube with a relatively rigid insulative spacer positioned between the inner and outer tubes so that the tubes are not in contact with each other. The outer tube is predominantly metallic and has at least one joint formed of insulative material to prevent the outer tube from forming a low electrical resistance loop. The inner tube provides a vacuum seal and the outer tube provides structural support for the inner tube so that eddy current losses resulting from ramping of the current to the coil are reduced.

Abstract: A magnetic resonance imaging magnet has a solenoidal superconducting winding producing a magnetic field and defining an examination region within a bore thereof. The examination region receives a body to be examined. The solenoidal superconducting winding generates a quasi-static magnetic field for aligning atomic nuclei in the body being examined. A two-fold or minimally symmetric ferromagnetic shield has a pair of magnetic flux return paths positioned on opposite sides of the solenoidal superconducting winding for reducing the magnetic field intensity in a region proximate to and outside of the solenoidal superconducting winding. A magnetic field inhomogeneity compensating system reduces magnetic field inhomogeneities introduced into the magnetic field within the examination region by the minimally symmetric ferromagnetic shield to provide a highly uniform quasi-static magnetic field within the examination region.

Abstract: Improved Stirling cycle machine including at least a pair of eccentric disks fixed to a pair of rotatable shafts in phase with each other and which eccentric disks upon rotation of the shafts (in opposite directions in the preferred embodiment) also rotate (in opposite directions in the preferred embodiment) and impart upward movement to a bellows defining a variable-volume compression or expansion chamber with a reduced tendency to also impart side thrust, rocking motion, or lateral movement to the bellows whereby bellows wear is reduced and the life of the bellows and the Stirling cycle machine is increased.

Abstract: Cryogenic regenerator formed by a spirally rolled, flexible composite material including a base layer having a top and a bottom provided with a plurality of spaced, substantially parallel corrugations extending outwardly therefrom and wherein the flexible base layer is rolled into a generally cylindrical spiral with the corrugations extending radially inwardly and engaging the top of the base layer to cause the base layer and the corrugations to cooperatively form a plurality of channels for conducting the working fluid through the regenerator. The relatively flexible composite material may be a relatively flexible, hardened epoxy; the composite material may be loaded with thermally conductive material and may be an epoxy loaded with thermally conductive material.

Abstract: A magnet system, having permanently installed power leads, for providing a magnetic field. The system includes a vacuum vessel and a cryogenic containment vessel supported within the vacuum vessel. The containment vessel holds a main coil formed of superconductive wire, along with a quantity of liquid helium to maintain the wire below its critical temperature. The power leads, which supply energy to the coil from a power supply outside the vacuum vessel, also take energy from the coil to a load resistor outside the vacuum vessel when the coil is discharged, each include an elongate metallic tube. The magnet system also includes a solenoid controlled valve which is responsive to the passage of electric current through the tubes of the power leads to cause helium gas resulting from the boiling of liquid helium in the containment vessel to be vented to atmosphere through the tube thereby cooling them.

Abstract: A magnet system for use in magnetic resonance imaging. The system includes a vacuum vessel having a first wall assembly defining a bore for receiving the subject of the imaging and a pair of spaced metallic end plates welded to the ends of the first wall assembly. The system further includes a cryogenic containment vessel supported within the vacuum vessel and a coil disposed within the containment vessel for providing the magnetic field. The first wall assembly includes a weldable metallic cylindrical shell positioned intermediate the end plates and having a thickness insufficient without reinforcement to provide structural integrity during operation of the vacuum vessel.

Abstract: A magnet system for providing a localized, substantially homogeneous field for use in medical magnetic resonance imaging and its incorporation into a method of siting. The magnet system includes a vacuum vessel defining a bore for receiving the subject of the imaging and having a first end and a second end. A cryogenic containment vessel is supported within the vacuum vessel and a single coil is disposed within the containment vessel for providing the magnetic field. The magnetic system also includes a shield assembly of ferromagnetic material positioned closely adjacent the outside of the vacuum vessel and including first and second end assemblies and a plurality of axially extending beam-like members interconnecting the end assemblies. The coil comprises a winding made up of thousands of turns of small superconductive wire and which is configured to compensate for the effect of the presence of the shield to provide the substantially homogeneous field at a predetermined location in the bore.

Abstract: A high gradient magnet is disclosed having a coil of superconducting material immersed in liquid helium in a toroidal shaped liquid helium vessel, supported in axial spaced concentric relation to a toroidal shaped liquid nitrogen vessel which forms one end of a toroidal heat shield made of high heat conductive material in which the liquid helium chamber is supported by a first coil support ring and a second coil support ring. The heat shield and liquid helium chamber are in turn supported in a toroidal shaped vacuum chamber which is in turn supported in a heavy iron cylindrical enclosure closed at the ends and having an opening through the center of its ends. A slurry containing iron particles may pass through the opening in the center whereby the iron particles from the slurry are retained by a matrix. The first coil support ring has two ends supported on the vacuum vessel and an intermediate part.

Abstract: A magnet system for providing a localized, substantially homogeneous magnetic field for use in nuclear magnetic resonance imaging. The magnet system includes a vacuum vessel defining a bore for receiving the subject of the imaging. It further includes a cryogenic containment vessel supported within the vacuum vessel. A single coil or "simple" solenoid is positioned within the containment vessel for providing the magnetic field. This coil includes a winding made up of thousands of turns of small superconductive wire, with the winding having a modular geometry including a plurality of axially spaced wire modules. The coil further includes an insulative substance, having a greater coefficient of thermal contraction than that of the wire, distributed in the winding. As the temperature of the coil is reduced from room temperature to its cryogenic operating temperature, the development of localized stress concentrations of sufficient magnitude to rupture the wire, are avoided.

Abstract: According to the present invention, improved cryogenic magnet systems for use in MRI devices are provided. These systems comprise an electromagnet immersed in a first tank containing a first liquefied gas. The first tank is located in an evacuated container that is evacuated to a high vacuum. A refrigerating system external to said evacuated container includes a second gas and a means for liquefying said second gas. A heat radiation shield means surrounding said first tank is cooled by the liquified second gas. Features of the invention include a thermal siphon for cooling the heat radiation shield and neon as the second gas.

Abstract: A magnet system for providing a substantially homogeneous magnetic field in a region. The magnet system includes a main coil and a pair of correcting coils with the main coil generating a magnetic field in a zone including the region. The correcting coils are at first and second locations in the zone and are connected to one another so that a magnetic field generated by the main coil will induce currents in the correcting coils which oppose one another. The correcting coils are constructed so that there will be no resultant current in them when there is generated substantially the same field strength of both of the first and second locations. Thus, the generation of differing magnetic field strengths at the respective locations effects generation of a resultant current in the correcting coil causing strengthening of the magnetic field at the location having the lesser magnetic field strength and weakening of the magnetic field at the other location, making the net field relatively homogeneous.

Abstract: To thermally stabilize superconductors that are potted in a polymeric material, such as is common in superconducting coils, materials having extremely high heat capacities at the superconducting temperatures are incorporated into the potting material. The heat-absorbing material may have an extremely high heat capacity at superconducting temperatures due to magnetic orderings it undergoes at superconducting temperatures or may be a heavy fermion material having electrons with effective masses greatly exceeding the bare electron mass.

Abstract: An apparatus 10 including a valveless rotatable, continuously vented vessel 11 for containing a liquid is described. The vessel can be confined in a vacuum chamber 15 to reduce heat losses from the liquid in the vessel. The apparatus is particularly adapted for containing superconducting coils in a cyclotron 100.

Abstract: A refrigeration system includes a dewar and a refrigerator/liquefier which meets the variable demands of a superconducting magnet within the dewar. The system is sized to meet average loads over a defined duty cycle, and is variably operable to meed demands. In the preferred embodiment, a first supply of fluid circulates through a "condenser" element positioned in a dewar ullage to liquefy a separate supply of fluid in the dewar, and to refrigerate a pulsed cryogenic load therein, such as a superconducting magnet. A portion of the first supply of fluid may be diverted to refrigerate a second pulsed cryogenic load, such as magnet current leads permanently connected to the magnet. The dewar includes a cold gas vapor storage chamber separate from the dewar ullage, and the chamber is preferably located within the inner core of a solenoid superconducting magnet for compact and thermally efficient design. Responsive, independent adjustment of refrigeration to pulsed cryogenic loads is made possible.