Abstract: A method and system for providing a ridethrough reserve for a pulse tube refrigerator (PTR) (12) includes a pressurized tank (42) containing a fluid used to provide fluid pressure and auxiliary power to a PTR (12) during an electrical power supply failure. A pressure regulation valve (pressure valve) (44) releases the fluid from the pressurized tank (42) into the PTR (12). A power regulation valve (power valve) releases from the pressurized tank (12) a driving gas volume for driving a pneumatic motor (46). The pneumatic motor (46) in turn drives a rotary valve (22) of the PTR (12). A release valve (50) releases fluid from the PTR (12) so as to lower the fluid pressure to a predetermined pressure range and enable fluid oscillation in the PTR (12).

Abstract: A magnetic shield for a superconducting joint in a superconducting magnet coil includes a superconducting tubular shield of superconducting materials surrounding the joint. The shield extends on either side of the joint a distance equal to the inside diameter of the shield. The coil is wound with niobium titanium conductors. The superconducting shield produces a field anomaly that influences the homogeneity of the imaging volume and an acceptable disturbance in the imaging volume while at the same time providing an ambient field condition that allows the superconducting joint to have a sufficiently low resistance to minimize superconducting current capacity degradation.

Abstract: A multi purpose interconnect assembly between upper and lower helium vessels in a recondensing superconducting magnet to provide isothermal connections to extend the ride-through period, and to provide for helium liquid and gas passage, electrical interconnections, and to accommodate differential thermal contraction and expansion.

Abstract: A vibration cancellation system for a magnetic resonance imager superconducting C-shaped magnet includes a vibration sensor at a remote end of the separated pole pieces to provide a vibration signal which is phase inverted and converted to an opposing force by a magnetoresistive actuator connected across the support member between the opposite ends of the pole pieces to cancel vibrations which would otherwise adversely affect the homogeneity of the magnetic field in the imaging region of the magnet.

Abstract: A quench protection circuit for the series connected but spatially separated magnet coils of a superconducting magnet utilizes a parallel circuit of multiple heaters and reverse connected diodes shunting portions of the series connected magnets coils with the heaters physically positioned in thermal contact with other coils in the series circuit to thermally transfer a heat quenching action in any coil to all coils, along with a shunting current through the diodes to shunt peak currents upon coil quenching to avoid undesired spot temperature rise and enable controlled quenching of the entire magnet upon quenching of any coil.

Abstract: A thermally insulating joint for multilayer insulating blankets for a superconducting magnet with layers of low thermal emissivity material separated by low conductivity spacers staked together with adjacent joints and vents offset from each other and with low emissivity adhesive strips overlying the remote ends of adjacent layers of the joined blankets.

Abstract: A cryogen recondensing magnetic resonance imager superconducting magnet utilizing a rare earth displacement material cryocooler with a superconducting sleeve surrounding a portion of the circumference of the cold end of the cryocooler to provide superconducting current flow of currents induced by movement of the rare earth displacer to generate opposing magnetic fields which shield the imaging region of the superconducting magnet from magnetic interference generated by movement of the cryocooler rare earth displacer.

Abstract: An open architecture magnetic resonance imaging permanent magnet assembly with moveable magnets and adjustable field inclination with automatic magnetic field homogeneity shimming to enhance imaging and positioning of the magnetic field about the portion of the patient to be imaged while enabling interventional physician access.

Abstract: A pressure control system for the cryogen pressure vessel of a helium cooled superconducting magnet assembly including a helium gas recondenser to return liquid helium to the helium supply including a temperature sensor proximate to the recondenser to provide a control signal for maintaining a preselected temperature of said recondenser in order to maintain a preselected pressure within said helium vessel above the pressure outside the vessel and further including an indication of the thermal conductance across the interface between the recondenser and the cryocooler which cools the recondenser.

Abstract: A cryogen recondensing system magnetic resonance imager superconducting magnet and a cryogen recondensing system with a rare earth displacement material cryocooler and superconductive lead bismuth magnetic sleeve provides superconducting current flow of currents induced by movement of the rare earth displacer which generate opposing magnetic fields to shield the superconducting magnet from the magnetic interference of the cryocooler rare earth displacer. Strips of high conductivity wave-shaped aluminum or sapphire rods may be embedded in the surface of the sleeve to lower the thermal resistance of the superconducting shield to enable it to quickly reach superconducting temperature.

Abstract: An indium gasket having a configuration which allows the indium to reach its yield point at a relatively low contact pressure. The indium gasket is provided with a multiplicity of openings which are filled by the deforming indium during compression between the cryocooler and the cryocooler interface sleeve of a superconducting magnet system. The creation of openings in the gasket has the effect of decreasing the mechanical interface pressure at which the indium yields. The indium flows at a mechanical interface pressure that does not exceed the structural strength requirements of the cryocooler. The indium flows into the empty spaces formed by the openings, thereby providing the necessary thermal conductance between the cryocooler and the interface sleeve. The result is a relatively small temperature difference between the interface sleeve and the cryocooler during cooling of the superconducting magnets.

Abstract: A mixed phase pump for rapidly rotating cryogenic machinery is disclosed, preferably for installation to a superconducting generator rotor. The superconducting generator rotor includes an inner and outer rotor structure joined in a thermally insulated configuration not unlike that of a Dewar flask. The inner rotor contains a support cylinder for a refrigerant, typically helium, which when refrigerated to 3.5.degree. Kelvin at one half a standard atmosphere under the normal rapid rotation of the axially aligned support cylinder, classifies itself into a two-phase liquid gas system. The phases include an outer cylindrical helium pool and an axially inward gaseous core separated by a cylindrical gas-liquid interface. During normal operation of the rapidly revolving rotor, a pump removes the gas for recooling to a liquid state by receiving the gas in the vicinity of the axis of the rotor at an inlet.