Method of producing a superconducting joint with niobium-tin

• US 5,398,398 A
• Filed: 01/10/1994
• Issued: 03/21/1995
• Est. Priority Date: 07/24/1992
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Zhukovsky, Alexander, Williams, John E. C., De Rocher, Ronald
• Primary Examiner(s): Arbes, Carl J.
• Application Number:
  US08/179,401
• Time in Patent Office: 435 Days
• Field of Search: 29/599, 505/925, 505/926, 505/927
• US Class Current: 29/599
• CPC Class Codes: H01R 4/68 Connections to or between superconductive connectors
• CPC Class Codes: Y10S 428/93 Electric superconducting
• CPC Class Codes: Y10S 505/925 Making superconductive joint
• CPC Class Codes: Y10S 505/926 Mechanically joining superconductive members
• CPC Class Codes: Y10S 505/927 Metallurgically bonding superconductive members
• CPC Class Codes: Y10T 29/49014 Superconductor
• CPC Class Codes: Y10T 428/12819 Group VB metal-base component

Abstract

A superconducting joint includes a niobium-tin superconducting composite member, a niobium-tin superconducting wire diffusion bonded to the superconducting composite, a spacer diffusion bonded to the superconducting wire, a support diffusion bonded to the spacer and a superconducting member in electrical contact with the superconducting composite. According to the method of the invention, a wire comprising unreacted niobium and tin is machined to form a tapered end having a first tapered surface exposing the wire interior and an opposing surface. A complementary spacer having the taper substantially similar to that of the wire is assembled with the wire so that the tapered wire and the tapered spacer in surface contact with one another such that the spacer occupies the area of the wire removed by machining and the exposed tapered surface remains still exposed. The wire/spacer assembly are positioned between a support plate and a composite member comprising unreacted niobium and tin such that the spacer is in surface contact with the support plate and the wire is in surface contact with the composite member thereby forming an assembled joint. Transverse pressure is applied to the assembled joint and the assembled joint is heated to form a superconducting phase and to diffusion bond the component elements of the assembled joint to one another. Lastly, a superconducting member is brought into electrical contact with an exposed face of the superconducting composite member.

Claims

1. A method for preparing a superconducting joint for joining a pair of superconducting wires, comprising the steps of:

(a) machining a wire comprising unreacted niobium and tin;

(b) providing a spacer;

(c) providing a composite member comprising unreacted niobium and tin;

(d) assembling in any order the wire, spacer, and composite member such that the wire is in surface contact with the composite member and the spacer is in surface contact with the wire;

(e) applying transverse pressure to the assembled elements of step (d);

(f) heating the assembled elements under transverse pressure to produce a superconducting niobium-tin phase in the composite member and the wire, and to diffusion bond the assembled elements to one another where the elements are in surface contact;

(g) electrically contacting a superconducting member to the composite member.

3. The method of claims 1 or 2, further comprising a step of providing a support plate, and wherein the step (d) of assembling comprises assembling in any order the wire, spacer, composite element, and support such that the first tapered surface of the wire is in surface contact with the flat surface of the composite member, the second tapered surface of the spacer is in surface contact with the first opposing surface of the wire, and the second opposing surface of the spacer is in surface contact with the support plate.

4. The method of claims 1 or 2, wherein the composite member is a powder composite.

5. The method of claims 1 or 2, wherein the wire comprises free filaments of niobium in a tin-containing matrix.

6. The method of claims 1 or 2, wherein the superconducting member comprises niobium-titanium.

7. The method of claims 1 or 2, wherein the elements of step (d) are assembled and the transverse pressure of step (e) is applied using a clamp, the clamp having a clamp body for receiving the assembled joint and a backing plate for supporting the assembled joint in the clamp, the clamp body and backing plate secured together by fastening means.

8. The method of claim 7, wherein the fastening means comprises fasteners passing through aligned apertures in the clamp body and backing plate.

9. The method of claim 8, wherein the fasteners comprise a material selected from the group consisting of Hastalloy, molybdenum, and tungsten.

10. The method of claim 7, wherein the clamp body and backing plate comprise stainless steel.

11. The method of claim 7, wherein the clamp body and backing plate are lined with insulation to prevent bonding of the assembled elements to the clamp.

12. The method of claim 7, wherein the assembled elements are removed from the clamp by inserting jacking screws in threaded apertures in the clamp body and backing support.

13. The method of claims 1 or 2, wherein the step (g) of electrically contacting the superconducting member to the composite member comprises spot welding.

14. The method of claim 13, wherein approximately 40 to 60 spot welds are made over a length of approximately 3.8 cm.

15. The method of claims 1 or 2, wherein the superconducting member has a thickness within the range of approximately 0.005 to 0.02 inch (0.13 to 0.51 mm).

16. The method of claims 1 or 2, wherein a plurality of superconducting members are electrically contacted with the composite member.

17. The method of claims 1 or 2, further comprising a step of applying an epoxy resin to the assembled joint after heat treatment.

21. The method of claim 3, wherein the wire and spacer are positioned in a channel of the support plate for additional support.

22. The method of claim 21 wherein the wire and spacer assembled in the channel extend beyond a support plate surface.

2. A method for preparing a superconducting joint for joining a pair of superconducting wires comprising:

(a) machining a wire comprising unreacted niobium and tin, such that the wire has a tapered end having a first tapered surface exposing the wire interior and a first opposing surface;

(b) providing a complementary spacer having a second tapered surface and a second opposing surface and having a taper substantially similar to that of the wire;

(c) providing a composite member comprising unreacted niobium and tin and having at least one flat surface;

(d) assembling in any order the wire, spacer, and composite element such that the first tapered surface of the wire is in surface contact with the flat surface of the composite member and the second tapered surface of the spacer is in surface contact with the first opposing surface of the wire;

(e) applying transverse pressure to the assembled elements of step (d) ;

(f) heating the assembled elements under transverse pressure to produce a superconducting niobium-tin phase in the composite member and the wire and to diffusion bond the assembled elements to one another where the elements are in surface contact; and

(g) electrically contacting a superconducting member to the composite member.

18. The method of claim 2, further comprising a step of aligning the exposed tapered surface of the wire prior to the assembling step (d) so that the exposed tapered surface of the wire is flush with the extended length of the wire.

19. The method of claim 2, wherein the wire and spacer are positioned in the assembly step (d) such that the exposed tapered surface of the wire and the second opposing surface of the spacer are substantially parallel.

20. The method of claim 2, further comprising a step of etching the exposed tapered surface of the wire after the machining of step (a) to expose niobium above a tin-containing surface.