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: 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.

Abstract: A superconductive magnet subassembly has a single unbroken length of superconductive conductor which has a mid portion wound so as to define at least one superconductive magnetic coil and which has two end portions superconductively joined together by a superconductive joint. A superconductive switch is at least partially defined by the two end portions and by a heater for controllably heating the two end portions.

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 and a superconductive bucking coil. The bucking coil is spaced radially inward and radially apart from the main coil. The bucking coil carries an electric current equal in amperage, and opposite in direction, to the main coil. The bucking coils overcome the gross magnetic field distortions in the imaging volume of the 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: This invention relates to a field mapping fixture for mapping the magnetic fields of a superconducting magnet. Such structures of this type, generally, are capable of measuring the magnetic fields of a relatively small imaging volume.

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 second longitudinal end of the vacuum enclosure fits on a patient's shoulders with the patient's head passing through the second bore and extending into the first bore for MRI brain imaging.

Abstract: This invention relates to a pole face design for superconducting magnets of the type that are C-shaped. Such structures of this type, generally, employ pole faces which homogenize the magnet field within the imaging volume.

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: This invention relates to demountable conduction cooled current leads for refrigerated superconducting magnets. Such structures of this type generally either allow the warm section of the current lead to be thermally demounted from the magnet after the magnet is powered or both the cold and warm sections of the current leads to be thermally demounted from the magnet after the magnet is powered. In this manner, the heat load placed upon the cryocooler is signficantly reduced when the magnet is powered.

Abstract: This invention relates to a superconducting magnet of the type that has a relatively small imaging volume. Such structures of this type, generally, allow the operator to image human limbs without the use of a larger, more costly superconducting magnet.

Abstract: An atomization apparatus for atomization of melts of high melting metal is taught. The apparatus includes a melt guide tube adapted to guide a molten metal from a source to an atomization zone where the molten metal is gas atomized. The melt guide tube has an inwardly tapered lower end disposed above the atomization zone. An annular gas supply means is disposed around the melt guide tube. The annular gas supply includes a gas shield for directing gas from an annular plenum of said means toward the lowermost portion of said melt guide tube. The external surface of the gas shield and the external inwardly tapered surface of the melt guide tube are spaced from each other. A highly reflective surface layer is formed on the confronting surfaces of the gas shield and melt guide tube to restrict loss of radiant heat from metal passing through said melt guide tube.

Abstract: This invention relates to refrigerated superconducting MR magnets having integrated cryogenic gradient coils. In particular, the amount of eddy currents produced by the magnet are substantially reduced while reducing the size and weight, and, therefore, the cost of the superconducting magnet required to produce an acceptable MR image.

Abstract: This invention relates to a superconducting joint which is more commonly referred to as, a pigtail joint, for use in superconducting magnets. Such structures of this type, generally, exhibit total superconducting behavior at temperatures below the transition value of the superconducting joint and have high electrical resistance at temperatures above the transition point of the superconducting joint.

Abstract: This invention relates to refrigerated superconducting eddy current free MR magnets having integrated gradient coils. In particular, the amount of resultant eddy currents produced by the magnet are substantially reduced while reducing the size and weight, and, therefore, the cost of the superconducting magnet required to produce an acceptable MR image.

Abstract: The invention relates to refrigerated superconducting MR magnets having integrated gradient coils. In particular, the amount of eddy currents produced by the magnet are substantially reduced while reducing the size and weight, and, therefore, the cost of the superconducting magnet required to produce an MR image.

Abstract: An apparatus and method is disclosed for evaluating the superconducting quality of superconducting materials. The materials are wound on a bifilar spool and tested in a cryogenic atmosphere to determine when the material quenches. During the testing procedure, the electro-magnetic field, current and temperature imposed on the material are varied and the test results are compared with known results to determine if the material is superconductive. In this way, large samples can be tested in a non-destructive manner.

Abstract: A superconductive switch for a superconductive magnet is bifilarly wound on a bobbin with niobium-tin tape and laminated with stainless steel foil for structural rigidity is provided. The switch is vacuum pressure epoxy impregnated and cooled by copper bus bars which are heat stationed to a cryocooler which is also used to conduction cool the superconductive magnet. The bus bars are also used to introduce a voltage across the switch and the magnet windings which are connected in series with one another to ramp up the current.

Abstract: A method of passively shimming a magnet having a central bore using ferromagnetic shims is provided. The field strength in the bore of the magnet is measured at a predetermined number of points. The field inhomogeneity is determined from the measured field strengths. The fields created by a single shim of known size when positioned, at different predetermined positions in the bore of the magnet is determined. The shim locations in the bore of the magnet and shim size are determined using a linear programming solver to minimize the field inhomogeneity and the total amount of shims used. The shim sizes are determined based on the measured field in the bore of the magnet and the field created by a single shim when positioned at a predetermined number of locations. The shim size at the appropriate locations are adjusted to the determined values and the field strength of the magnet is again measured at the predetermined points.

Abstract: A method of shimming a magnet having correction coils is provided. The field strength in the bore of the magnet is measured at a predetermined number of points. The field inhomogeneity is determined from the measured field strengths. The field created by a fixed current in each shim coil operating alone, at each of the predetermined points is determined. The shim correction coil currents are determined using a linear programming solver to minimize the field inhomogeneity and the correction coil currents. The correction coil currents are determined based on the measured field in the bore of the magnet and the field created by each of the shim coils when carrying a fixed current, with the correction coil currents each constrained to a maximum value which is adjusted for the current in the correction coils when the field strength was measured. The correction coils are adjusted to the determined values and the fields strength of the magnet is gain measured at the predetermined points.