NMR spectrometer with superconducting coil having rectangular cross-section wire

Abstract

An NMR spectrometer includes a superconducting, solenoid coil formed of superconducting wire having a rectangular cross-section. The wire is formed of a non superconducting metal surrounding superconducting material having a small enough cross sectional area that a magnetic field resulting from current flowing in the superconductor material has a relatively constant position relative to the cross section of the wire. In one embodiment, the wire has a monofilament configuration including a core of the superconducting material surrounded by a sheath of the metal. In a second embodiment, the wire includes a copper block of the metal through which a multiplicity of superconductive strands extend.

What is claimed is: 
     
       1. An NMR spectrometer for testing a sample comprising a transmitting coil for applying an rf field to the sample,   a receiver coil coupled to the sample for deriving a signal indicative of the NMR properties of the sample,   a solenoid coil having a longitudinal axis about which the coil is wound and a central core in which said transmitting and receiver coils and said sample are positioned, said coil applying a homogeneous DC magnetic field to the sample,   said coil being formed of superconducting wire having a rectangular cross-section, said wire being formed of a non-superconducting metal having a relatively low room temperature .Iadd.electrical conductivity, said .Iaddend.material surrounding .Iadd.said .Iaddend.superconductor material having a small enough cross-sectional area that a magnetic field resulting from current flowing in the superconductor material has a relatively constant location relative to the cross-section of the wire, said wire being wound as a plurality of helices each of which is concentric with the coil longitudinal aixs, immediately adjacent helices having oppositely directed pitches and faces that abut substantially against each other, adjacent turns of the same helix having faces that abut against each other.   
     
     
       2. The spectrometer of claim 1 wherein the superconductor material has a maximum cross section dimension of approximately 0.016 inches. 
     
     
       3. The spectrometer of claim 1 wherein adjacent faces of the wire differ in length so that the longer and shorter faces respectively extend transversely and parallel to the longitudinal axis of the coil. 
     
     
       4. The spectrometer of claim 3 wherein the wire has a monofilament configuration including a core of the superconducting material surrounded by a sheath of the non-superconducting metal. 
     
     
       5. The spectrometer of claim 4 wherein the longer and shorter faces respectively have dimensions of approximately 0.016" and 0.013". 
     
     
       6. The spectrometer of claim 5 wherein the core has a diameter of approximately 0.01 inches. 
     
     
       7. The spectrometer of claim 3 wherein the wire includes a block of the non-superconducting metal having .[.relatively high room temperature.]. .Iadd.a higher electrical .Iaddend.conductivity .Iadd.than the superconductor in the normal phase thereof .Iaddend., a multiplicity of strands of the superconducting material extending through the block.   
     
     
       8. The spectrometer of claim 7 wherein the longer and shorter faces respectively have dimensions of approximately 1 mil and 0.36 mils, each of said strands having a cross-sectional thickness of approximately 5 microns. 
     
     
       9. The spectrometer of claim 1 further including a layer of dielectric material between adjacent faces of adjacent ones of said helices. 
     
     
       10. The spectrometer of claim 1 wherein the wire has a monofilament configuration including a core of the superconducting material surrounded by a sheath of the non-superconducting metal. 
     
     
       11. The spectrometer of claim 1 wherein the wire includes a block of the non-superconducting metal having a relatively high .[.room temperature.]. .Iadd.electrical .Iaddend.conductivity .Iadd.compared to the superconductor in the non-superconducting phase thereof.Iaddend., a multiplicity of strands of the superconductor material extending through the block.   
     
     
       12. In combination with an NMR spectrometer for testing a sample, a solenoid coil having a longitudinal axis,   said coil applying a homogeneous DC magnetic field to the sample,   said coil being formed of superconducting wire having a rectangular cross-section,   said wire being formed of a non-superconducting metal having a relatively low .[.room temperature.]. .Iadd.electrical conductivity compared to said superconductor in the superconducting phase thereof, said .Iaddend.material surrounding .Iadd.said .Iaddend.superconductor material having a small enough cross sectional area that a magnetic field resulting from the current flowing in the superconductor material has a relatively constant position relative to the cross section of the wire, and   means for maintaining said coil at cryogenic, liquid helium temperatures.   
     
     
       13. The combination of claim 12 wherein adjacent faces of the wire differ in length so that the longer and shorter faces respectively extend transversely and parallel to the longitudinal axis of the coil. 
     
     
       14. The combination of claim 13 wherein the wire has a monofilament configuration including a core of the superconducting material surrounded by a sheath of the non-superconducting metal. 
     
     
       15. The combination of claim 13 wherein the wire includes a block of the non-superconducting metal, and a multiplicity of strands of the superconductor material extending through the block.