Varian Associates, Inc.

Magnetic Diagnostics, Inc.

Magnetic Diagnostic, Inc.

Marvin H Anderson

George D Kneip, Jr

Boban K John

Thomas W Schleich

James N Shoolery

John H Broshear

George Chmyz

Robert E Gang

Reuy-Lin Lee

Carl D Daus

A magnet assembly for a small scale NMR spectroscopy apparatus suitable for laboratory or home use, generally comprising two permanent magnets facing one another so that the facing surfaces have opposite polarities, a pole cap on each of the two facing surfaces of the permanent magnets, and a plurality of radially polarized canceling magnets disposed about the permanent magnets and pole caps. The design and position of the radially polarized canceling magnets about the tapered pole caps reduces leakage of the magnetic field, to maintain the magnetic field strength and homogeneity within the test region, without a disadvantageous increase in the size, weight and cost of the NMR apparatus. A curved edge ring shim may be used to increase magnetic field homogeneity in the test region. Also provided is a method for measurement of glucose concentration in a fluid using NMR spectroscopy. In one aspect of the invention the fluid is a patient's body fluid and the invention provides for in vivo measurement of the glucose concentration. The method comprises spectral editing in which a RF pulse sequence is used to isolate desired resonances of glucose and thereby facilitate resolution of the glucose signal.

Small scale NMR spectroscopic apparatus and method

A liquid nitrogen Dewar includes a spun can for the liquid nitrogen, which spun can is surrounded by an exterior shell. Between the exterior shell and the can is an evacuated space containing a second shell that functions as a radiation shield. The can and both shells are formed of an aluminum alloy having a very high percentage of aluminum. The exterior can surface, interior surface of the exterior shell, and both surfaces of the second shell have clean, non-pitted, smooth, matted, smut free and etched appearances free from discoloration and stains so that these surfaces have low radiation emissivity properties and there is a minimum amount of radiant energy transmitted from the exterior shell to the can and reduced heating of the liquid nitrogen in the can. Each of the surfaces is initially polished, either mechanically, electrochemically or chemically, and then chemically treated with an etchant of nitric acid and hydrofluoric acid for a sufficient duration to achieve the desired appearance.

Method of manufacturing a low emissivity liquid nitrogen dewar

Vapor from a boiling cryogenic liquid contained in a cryostat is warmed prior to discharge by passing said vapor through a heat exchanger for transferring heat at ambient temperature to the escaping vapor whereby condensation of atmospheric moisture on the cryostat is minimized.

Reduction of water condensation on neck tubes of cryogenic containers

Component coils for providing a desired magnetic field distribution, which coils are subject to interaction via mutual inductance thereof, are connected each to respective current regulated power supplies whereby the interaction is compensated. Circuits are provided to control selected pluralities of interacting coils via persistence switches with minimum number of control leads in order to reduce the thermal communication to the interior of a cryostat housing the magnet and persistence switches.

Method for superconducting magnet shimming

The thermal loss incurred through a fill and vent conduit of a cryostat is minimized by inclusion therein of a central coaxial member. Thermal energy transfer is desirably promoted by radiation between the interior surface of the fill and vent tube and the central coaxial member by enhancement of the emissivity of the respective facing surfaces. For a tubular central member dual paths to respective pressure relief valves are obtained.

Cryostat structure

An improved cryostat for the superconducting magnet of an NMR spectrometer comprises a nested structure of isothermal shells surrounding a thermally conductive central reservoir of substantially spherical shape containing liquid helium in which the superconducting solenoid remains operational when only partially immersed. A radiation shield surrounding the central reservoir is cooled by the boil-off of escaping helium vapor. The radiation shield is enclosed within a isothermal shell maintained at the temperature of liquid nitrogen by thermal contact with a liquid nitrogen reservoir disposed above the region of the central reservoir and shielded therefrom by a wall of the isothermal shell. An outer radiation shield surrounds the liquid nitrogen reservoir and associated isothermal shell and the outer radiation shield is maintained at a temperatures of the order of 180.degree. K. by an external refrigeration facility. A hermitically sealed containment vessel forms the outer wall of the cryostat and provides a port for evacuating to a very low common pressure all the interior spaces between adjacent nested structures. The spacing between adjacent nested surfaces is maintained by a novel internal mechanical bracing system of low thermal conductivity comprising polyester cords disposed under tension between adjacent shells.

Cryostat with external refrigerator for super-conducting NMR spectrometer

Apparatus and method for reduction of noise in NMR signals during high power heteronuclear decoupling experiments. A material is introduced into the evacuated area of the variable temperature probe to decrease collisional probability of ions generated in the interwall space of the evacuated envelop.

Method and apparatus for preventing ionization induced noise in

A persistence switch comprises a diode and superconductive wire in thermal contact with the diode. The heat evolved by current through the forward biased diode raises the temperature of the superconductor above the transition temperature. The diode characteristic of the switch permits a plurality of such switches to be arranged in a network for selection by a relatively few signal conductors.

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Mountain View, CA, United States of America

Marvin H Anderson