Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F6/00—Superconducting magnets; Superconducting coils
  • H01F6/06—Coils, e.g. winding, insulating, terminating or casing arrangements therefor
  • H01F6/065—Feed-through bushings, terminals and joints
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
  • H01R4/00—Electrically-conductive connections between two or more conductive members in direct contact, i.e. touching one another; Means for effecting or maintaining such contact; Electrically-conductive connections having two or more spaced connecting locations for conductors and using contact members penetrating insulation
  • H01R4/58—Electrically-conductive connections between two or more conductive members in direct contact, i.e. touching one another; Means for effecting or maintaining such contact; Electrically-conductive connections having two or more spaced connecting locations for conductors and using contact members penetrating insulation characterised by the form or material of the contacting members
  • H01R4/68—Connections to or between superconductive connectors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F6/00—Superconducting magnets; Superconducting coils
  • H01F6/02—Quenching; Protection arrangements during quenching

Definitions

• This invention relates to superconducting joints for conductors used in winding coils for superconducting magnets of the type used for magnetic resonance imaging (hereinafter "MRI").
• MRI magnetic resonance imaging
• the superconducting joint has to be of low electrical resistance to avoid heating and power losses at the joint.
• a superconducting magnet coil joint in which pigtails are twisted to form a joint, and a hollow superconducting sleeve is positioned around the joint.
• the superconducting sleeve extends on either side of the joint a distance of one-half inside diameters of the sleeve.
• the sleeve is a stabilized superconducting material, such as niobium titanium to exclude the main magnetic field of the coil and minimize superconducting current capacity degradation.
• FIG. 1 is a cut-away perspective view of a superconducting magnet joint illustrating the present invention.
• FIG. 2 is an enlarged view of a portion of FIG. 1.
• a plurality of adjacent turns 12, 14 and 16 of niobium-titanium (NbTi) 60 x 90 mill ribbon or tape are wound from a spool (not shown) to form superconducting magnet coil 10.
• Turns 12, 14 and 16 are wound side by side and supported on coil form 8 to form layers such as 18 of magnet coil 10.
• Coil form 8 is fabricated of filament- wound glass epoxy.
• End 30 of superconductive layer or superconducting conductor 20 which overlies conductor 12 of layer 18 is joined to end 22 of conductor 12 to form joint 50 as described in detail below. The joinder of conductors is required in order to continue winding superconducting magnet coil 10 when the end of conductor 20 from the spool used in winding the coil is reached.
• the ends 22, 30 of conductors 12, 20, respectively, are dipped in molten tin to dissolve off the copper matrix commonly associated with the NbTi conductors providing a plurality of tin coated "pigtails" or NbTi strands 32 and 40 which make up the conductors. Strands 32 and 40 are then twisted together to electrically connect ends 22 and 30 of conductors 12 and 20, respectively, and together to form joint 50 as best shown in FIG. 2.
• Hollow tube or canister shield 34 of a high or low temperature superconducting material is then placed around superconducting joint 50.
• shield 34 was Niobium titanium (NbTi) with an inside radius of 0.08 inches, an outside radius of 0.1875 and a length of 1.625 inches. That is, the axial length of shield 34 is approximately the length of joint 50 plus twice the inside diameter of shield 34.
• the shield extends beyond the joint at each end a distance at least equal to the inside diameter of the shield.
• the ratio of the extension of shield 34 beyond joint 50 to the internal diameter of shield 34 preferably varies from 0.5 to 1.5 ore more.
• a lead bismuth (PbBi) alloy 35 may be flowed into the interior of hollow cylinder 34 around conductors 12 and 20 filling the open spaces.
• shield cylinder 34 is superconducting when magnet coil 10, including coil turns 12, 14, 16 and 20, is superconducting.
• tubular shield 30 excludes the external magnetic field in bore 36 from superconducting joint 50 by maintaining initial magnetic flux linkages of the shield cylinder.
• the direction of current flow in the spliced or joined conductors 12 and 20 which overlie one another may be in opposite directions as indicated by arrows 26 and 28 in FIG. 1.
• the reversing magnetic field effect resulting from the reversed current flow tends to cancel and minimize the effect of joint 50 on the main magnetic imaging field in bore 36.
• This enables superconducting joint 50 to operate at nearly zero field even though it may be within an ambient external field of up to 5 Tesla, or even more. As a result, the current carrying capability of the PbBi is increased.
• superconducting joint 50 holds the interior magnetic field within cylinder shield 34 at 2 Tesla in the presence of an exterior magnetic field 36 within bore 36 of superconducting magnet 10 at 4 Tesla, and with an acceptable inhomogeneity of 4.7 parts per million (ppm) in the imaging volume of bore 36. A normal limit of 10 ppm inhomogeneity is acceptable.
• Space 35 within superconducting tubular shield 30 may be filled with molten lead bismuth which would dissolve the tin off the copper portion of strands 32 and 40.
• tubular shield 30 may have a closed end positioned beyond the ends of strands 32 and 40 with strands 32 and 40 positioned inside. Joint 50 can then be cast directly into the shield cylinder using lead bismuth.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Magnetic Resonance Imaging Apparatus (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=23876536

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (3)

Citations (4)

Family Cites Families (9)

• 1999
  • 1999-12-27 US US09/472,687 patent/US6358888B1/en not_active Expired - Fee Related
• 2000
  • 2000-12-15 DE DE60044123T patent/DE60044123D1/de not_active Expired - Lifetime
  • 2000-12-15 WO PCT/US2000/034018 patent/WO2001048767A1/en not_active Ceased
  • 2000-12-15 JP JP2001548400A patent/JP4767468B2/ja not_active Expired - Fee Related
  • 2000-12-15 EP EP00993661A patent/EP1159749B1/en not_active Expired - Lifetime

Patent Citations (4)

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