Abstract: A correction coil current adjustment circuit for a superconducting magnet to selectively switch various coils in circuit with a power source to provide the desired superconducting current flow and magnetic field homogeneity for magnetic resonance imaging eliminating the need for some of the mechanical leads which extend from the exterior of the magnet to the interior of the cryogen vessel minimizing thermal leak paths and including simplified switching of the various main and correction magnet coils to provide the desired current flow. Inductive coupling from outside the magnet to induce correction coil current flow eliminates additional mechanical leads.

Abstract: A suspension system for a superconducting magnet for supporting and spacing the thermal radiation shield and vacuum vessel about the cryogen vessel utilizing a carbon fiber reinforced composite assembly with a first frustro-conical member positioned between the cryogen vessel and radiation shield and a second frustro-conical member extending from the vacuum vessel to overlap the radiation shield with a radially extending connecting member between the interior ends of the members to provide a tortuous generally Z-shaped lengthened thermal path and thermal resistance plus mechanical support in both the axial and radial directions.

Abstract: A passive shimming system for a superconducting magnet to improve bore magnetic homogeneity includes a plurality of axially extending non-magnetic drawers each including a plurality of pockets along the drawer with a securable cover for each pocket to enclose the selected ferromagnetic shim disks and compressible spring material to enable individual access and shimming of selected pockets.

Abstract: In the installation of a superconducting magnet for magnetic resonance imaging at a preselected position in a mobile van, preselected curvilinear magnetic segments are applied to preselected locations on the exterior of the magnet to counteract magnet inhomogeneities in the imaging bore which would otherwise occur because of magnetic material in the van structure.

Abstract: An apparatus and method for precooling a mass to be cooled to a final low temperature by immersion in a cryogenic liquid, e.g. liquefied helium. The gaseous phase of the cryogenic liquid is cooled by heat exchange with a cryogenic liquid having a higher boiling point than the cryogenic liquid within which the mass is to be immersed. The cooled gaseous phase is circulated through a vessel containing the mass, recovered, recooled and recirculated until the mass and its containment vessel are at the desired precooling temperature. Thereafter cryogenic liquid can be introduced into the vessel to immerse the mass.

Abstract: A new design for an aluminum stabilized superconductor which embeds the superconducting cable within a high purity aluminum stabilizer. This stabilizer is, in turn, partially surrounded by an aluminum alloy sheath. The aluminum alloy sheath is constructed and arranged so that at least one exterior surface of the stabilizer is open for exposure to a coolant. Preferably, this open exterior surface of the stabilizer will be knurled for greater cooling efficiency.

Abstract: A multi-phase DC chopper circuit having a different number of phases on each side of the current source. The ciruit utilizes fewer chopper phases and produces more discrete DC voltage steps.

Abstract: A compressive strut for cryogenic applications includes a tube with a cylindrical bore wall defining an internal cavity, a rod of filling material within the cavity which has low thermal conductivity, and structure in engagement with the rod, such as end plugs partially inserted into the ends of the tube and in contact with the rod. The tube may be formed of a composite material such as fiberglass within a matrix of epoxy, wherein the fiberglass fibers are wound circumferentially. The plug at one end of the strut is attached to the warm support structure and the plug at the other end is attached to the cold structure, such as a superconducting magnet which is maintained at cryogenic temperatures. Compressive pressure applied by the magnet to the strut causes the plugs to press inwardly on the filling material rod, expanding the rod radially.

Abstract: A new design for an aluminum stabilized superconductor which embeds the superconducting cable within a high purity aluminum stabilizer. This stabilizer is, in turn, partially surrounded by an aluminum alloy sheath. The aluminum alloy sheath is constructed and arranged so that at least one exterior surface of the stabilizer is open for exposure to a coolant. Preferably, this open exterior surface of the stabilizer will be knurled for greater cooling efficiency.

Abstract: An electromagnetic system for a magnetic levitation vehicle comprises a "W" shaped magnet core having a center pole wound by a superconducting coil and side poles on opposite sides of the center pole, each wound by an ambient temperature coil. Quasi-dc power is supplied to the central superconducting coil for levitation of the vehicle with respect to a rail along which the vehicle is meant to move. The ambient temperature coils are connected in series to each and other and powered with ac power for trimming and controlling the gap between the magnet and the rail.

Abstract: A thermal plug which provides an electrical connection between first and second regions at different temperatures includes a plurality of interleaved heat transfer resistive laminae and heat conductive laminae. The laminae are stacked together to form a laminate and a plurality of superconducting strands are attached to the stack such that they are in thermal contact with the laminate. The superconducting strands are also in electrical contact with a conductor (e.g., a low temperature superconductor), in the first region and a conductor in the second region to allow the supply and withdrawal of electrical energy to and from the conductor in the first region.

Abstract: A superconducting energy storage magnet is constructed for mounting in relatively shallow trenches or tunnels to provide superconductive energy storage for applications such as power system load leveling. The magnet includes composite superconductors arranged in substantially planar coil layers around a central axis. A first and second coil layer have an inner support structure between them to which the conductors of the layers are engaged. The inner support structure carries the magnetically induced forces on the conductors of the coils. The net radial magnetically induced force is opposed by the rigid structural material of the inner support structure and by support struts which extend from the periphery of the inner support structure to a surrounding support wall such as the wall of a trench. The conductors in each layer, and the inner support structure between them, have matching vertically (axially) undulating ripples over the circumference of the magnet.

Abstract: A superconducting magnet is formed having composite conductors arrayed in coils having turns which lie on a surface defining substantially a frustum of a cone. The conical angle with respect to the central axis is preferably selected such that the magnetic pressure on the coil at the widest portion of the cone is substantially zero. The magnet structure is adapted for use as an energy storage magnet mounted in an earthen trench or tunnel where the strength the surrounding soil is lower at the top of the trench or tunnel than at the bottom. The composite conductor may be formed having a ripple shape to minimize stresses during charge up and discharge and has a shape for each ripple selected such that the conductor undergoes a minimum amount of bending during the charge and discharge cycle.

Abstract: A DC to DC converter has a transformer with a highly coupled primary and secondary, a first switch connected in series between a current source and the primary, a second switch connected across the current source in parallel with the first switch and the primary, a rectifier connected to rectify the output of the secondary, an energy storage device such as a capacitor connected to receive the output from the rectifier, and a load connected to receive output voltage across the capacitor. The current source which provides the substantially constant current can be a superconducting storage magnet. The first and second switches are controlled to alternately open and close to provide current through the primary of the transformer to recharge the energy storage device. When voltage across the energy storage capacitor reaches a minimum level, the one of the first and second switches which was closed is opened and the other is closed.