Abstract: A superconductive magnet for magnetic resonance imaging not requiring consumable cryogens or requiring cryogen liquid or vapor cooling of superconducting coils is provided having a resin impregnated coil of superconductor wire. Heat conductive means having a thermal conductivity greater than the resin, contact the impregnated coil along the length of at least one of the impregnated coil surfaces. A thermal radiation shield is spaced away from and surrounds the resin impregnated coil and heat conductive means. An evacuable housing is spaced away from and surrounds the shield. The housing supports the shield, heat conductive means and the impregnated coil.

Abstract: A two stage cryocooler sleeve is provided having a second stage heat exchanger system capable of achieving lower temperatures than the first stage heat exchanger. A current lead comprising a ceramic superconductor having a critical temperature greater than the operating temperature of the first stage is tapered. The broader end is thermally coupled to the first stage heat exchanger and the narrow end coupled to the second stage heat exchanger. The tapered ceramic lead reduces the heat conduction from the first heat exchanger to said second heat exchanger.

Abstract: A magnetic resonance superconductor magnet is provided comprising a cylindrical coil form having a plurality of circumferential grooves. Superconductor wire is wrapped under tension in each of the circumferential grooves. The superconductor wire in each groove forms a main magnet coil. The start and finish ends of the overwrapped wire are electrically shorted.

Abstract: An integrally shielded magnetic resonance magnet is provided comprising a cylindrical ferromagnetic shell and two ferromagnetic circular end plates each defining a central aperture extending axially therethrough. The end plates are welded vacuum leak tight at their peripheries to either end of the shell. A nonmagnetic cylindrical tube is welded vacuum leak tight between the central apertures of the end plates forming an axially extending bore through the cylindrical shell. The ferromagnetic shell and end plates are heated with rust inhibiting coatings. The end plates, shell and nonmagnetic tube form a vacuum vessel and shield. Magnet windings are situated in the vacuum vessel synthesized for operating in the presence of the ferromagnetic vessel.

Abstract: An unimpregnated winding for use in a cryostat of a superconducting magnet is provided comprising a form including a shell having the shape of two truncated cones attached to one another at their respective bases. Superconducting wire is wrapped around the form under tension so that during superconducting magnet operation, the form remains under compression.

Abstract: A resistive magnet is provided having a cylindrical radio frequency/gradient coil assembly. A first and second cylindrically shaped main coil is situated coaxially on either side of the radio frequency/gradient coil assembly with the radio frequency/gradient coil assembly and the first and second main coils having the same inside diameter defining a magnet bore. A cylindrical correction assembly coil surrounds the radio frequency/gradient coil assembly. Means for securing the first and second main coil to the cylindrical correction assembly is provided. The radio frequency/gradient assembly provides axial support for the first and second main coil assembly. For additional cylindrical main coils surround the correction coil.

Abstract: A spring loaded valve for use with a cryostat insert is provided for selectively directing liquid cryogen to the bottom or top of a supercoolable vessel. The spring loaded valve situated at the tip of the insert extends into a housing in the top of the supercoolable vessel. A slidably mounted sleeve extends inside a cryogen fill tube. The sleeve is spring loaded and when the valve is inserted in the housing the fill tube covers apertures in the sleeve allowing fluid to flow from the fill tube through the end of the housing past the valve head. When the spring loaded valve is partially retracted from the housing the holes in the sleeve are uncovered and liquid can flow from the fill tube to a passageway in the housing extending to the bottom of the supercoolable vessel. The valve closes the aperture leading to the upper portion of the vessel.

Abstract: Retractable cryogenic leads for superconducting magnets are provide for making low resistance contacts at liquid helium temperature reliably in the presence of heavy frost. A tube defining a bayonet socket on one end extends through a vertical stack cover of a cryostat insert to engage and disengage a vertical terminal rod having a transverse pin. A copper rod is slidably mounted inside the tube and is vertically displaced relative to the tube by a nut rotatably mounted on the other end of the tube and threadingly engaged with the copper rod. The end of the copper rod can be forced against the top of the vertical terminal rod at high pressure after the bayonet socket engages the pin of the vertical terminal rod.

Abstract: The insert has a horizontal vacuum jacketed, vapor cooled tube that fits in the cryostat penetration tube. The insert is equipped with a vertical service stack to access cryogenic leads of the cryostat magnet as well as a slanted transfer line to supply liquid helium or couple the insert to a liquifier. Internal radiation shields of the insert are heat stationed to thermal stations of the horizontal vapor cooled tube and the internal shields are also heat stationed to a vapor cooled tube in the vertical stack. A burst disk is provided near the top of the vertical stack as a pressure relief device.

Abstract: A split ring clamp having a hard, serrated interior surface is urged against an electrically conductive lead by means of a pivoting cam lever. The conductive lead includes a metal coating which is relatively soft at cryogenic temperatures. This arrangement avoids the problem of frost buildup and undesirable resistive heating effects in the powering of superconducting electromagnets disposed within a cryostat, particularly a cryostat containing liquid helium as a cooling fluid.

Abstract: Electrical switches used in conjunction with high energy superconductive windings must be able to quickly absorb large amounts of electrical energy since switching of the superconducting current is accomplished by means of transition to the resistive state in the switch portion of the superconducting current loop. Furthermore, to minimize the heat generated during the transition to the resistive state, the switch itself should exhibit a relatively high resistance while at the same time exhibiting a low external magnetic field. The switch should also exhibit minimal stray magnetic fields, especially in those applications requiring field uniformity. These objectives are achieved in a persistent current switch which includes a length of superconductive material disposed in a compact, thermally insulated volume which also includes a mechanism for heating at least a portion of the superconductive conductor in the switch in order to return it to its resistive state.

Abstract: The resistor assembly includes a plurality of resistor sections each in the form of resistive plates in which slots have been cut to provide a continuous resistive element of low inductance. The resistor sections are stacked together with thin insulating sheets separating adjacent resistor sections. The resistor sections are serially interconnected. Taps are provided on selected resistor sections to form a plurality of serially connected resistors in which each resistor is electrically isolated from an adjacent resistor but closely thermally coupled thereto. The resistive plates are bound together by discrete bands of an insulating material such as glass cloth tape. Epoxy impregnation allows the resistor assembly when connected in shunt with series connected superconductive coils to be immersed in the liquid helium of a magnet cryostat without causing excessive pressure rise during a quench event.

Abstract: A plug for a horizontal cryostat penetration comprises a plurality of nested housings with thermal insulation disposed between the housings. Each housing has a tubular extension which is heat stationable to portions of the cryostat penetration, the more inner the housing, the colder being the portion to which it is stationed. The innermost and outermost housings each possess pressure relief means for relieving internal pressure buildup which occurs as a result of magnet quench or vacuum loss. In operation the plug is disposed within the cryostat penetration and in particular, typically within a tubular conduit associated therewith. The tubular extension of the outermost housing also has preferably disposed around its exterior, one or more string-shaped helically disposed lengths of sealing material. Accordingly, when the plug is placed within the penetration, a helical coolant vapor path is formed for plug cooling and exterior ventilation.

Abstract: Penetration tubes extending between inner and outer walls of a cryostat necessarily comprise thin walled structures to minimize thermal conduction. However, in cryostat structures in which the inner vessel is capable of undergoing the relative motion with respect to the outer vessel, particularly during transport and thermal contraction, a means of accommodating this motion must be found which does not impose significant stresses on the thin walled penetration tube. Accordingly, the present invention provides a bearing and bellows arrangement which accommodates axial motion, thermal expansion and contraction and rocking motions of the inner cryostat, while at the same time ensuring the maintenance of vacuum conditions between the cryostat walls.

Abstract: An insert for a horizontal cryostat penetration comprises a plurality of foam plugs between which are disposed patches of copper or aluminum foil. The plugs and foil are disposed in a tubular conduit comprising thin wall, low thermal conductivity material. This plug provides thermal insulation and significantly reduces the formation of convection currents in the penetration which would otherwise significantly increase the rate of coolant evaporation. The insert assembly described is designed to be ejected from the penetration upon the build up of excessive internal pressure. The insert is also preferably disposed within another tubular conduit around the exterior of which there is disposed one or more string-shaped helically disposed lengths of sealing material. Accordingly, when this assembly is inserted within a third conduit, a helical coolant vapor path is formed for exterior venting.

Abstract: A cryostat for use in magnets for NMR medical diagnostic imaging includes inner and outer vessels suspended by sets of at least three low thermal conductivity ties. The positioning of the tie anchoring points, particularly on the interior vessel, are selected in accordance with the present invention to preclude increased stresses in the supporting ties that occur as a result of thermal contraction. This configuration is particularly advantageous in that it permits the utilization of ties having smaller cross-sectional areas than would otherwise be required. The reduced cross-sectional area requirement is also therefore seen to increase the thermal isolation of the interior cryostat vessel. Cryostat vessels may be nested within one another.

Abstract: An insert for a horizontal cryostat penetration includes a plurality of foam particles or spheres between which are disposed disks of high thermal conductivity. The spheres or particles are disposed in an annular volume defined by two concentric, thin-wall, low thermal conductivity conduits. This foam filled insert provides thermal insulation and significantly reduces the formation of coolant vapor convection currents in the penetration which would otherwise significantly increase the rate of coolant evaporation from the cryostat. The insert is constructed so that the foam particles are ejected from the penetration upon the buildup of excessive internal pressure. The insert has also preferably one or more string-like lengths of sealing material disposed in a helical pattern about the outer one of the concentric conduits. Accordingly, when this insert is placed within a third conduit, a helical coolant vapor path is formed for insert cooling and exterior ventilation.

Abstract: A cryostat which is particularly useful for containing superconducting windings for a magnet to provide high strength magnetic fields for NMR imaging comprises a set of nested annular vessels in a suspension system which permits transport of the cryostat and magnet assembly with vacuum conditions intact. In particular, sets of transverse ties linking certain vessels to the next adjacent outer vessel are employed to prevent transverse motion of the cryostat assembly. Furthermore, during transport, a system of pins is employed to prevent axial motion, while at the same time minimizing thermal conductivity. During transport, the inner annular assemblies are locked in a fixed axial position which permits transport of the cryostat in a vertical position.

Abstract: A superconducting magnet includes a coil support structure comprising a body formed of a generally-cylindrical wall. The body includes at least a pair of surfaces facing inwardly of said body, each being of generally-cylindrical shape and each being adapted to abut the radially-outer surface of a respective one of a pair of ring-shaped, superconductive coils. The support structure comprises a material such as aluminum which is adapted to shrink around the coils as the body and coils are cooled to a cryogenic temperature, so as to provide interference fits between the body and the coils. To prevent movement of the coils towards each other due to magnetic attraction forces therebetween, the body includes a pair of shoulders extending inwardly from respective adjacent edges of the pair of inwardly-facing surfaces. The shoulders are adapted to abut confronting surfaces of the pair of coils to prevent the coils from moving towards each other.

Abstract: A method and structure for restricting relative sliding motion at the interfaces between a superconducting winding and a supporting structure for the winding. An interface lining material having a low shear modulus of elasticity so as to accommodate large shear displacements with low shear stresses is used as opposed to the use of sliding frictional contact between the contacting surfaces of the electrical winding and the supporting structure. The invention is completed by subjecting the lined interfaced surfaces to large compressional pressure forces so that frictional forces between the interface material and the opposing superconducting winding and supporting structure surfaces, even at low coefficients of friction, are considerably higher than the internal shear forces of the interfacing lining material.