Method for producing (Nb, Ti)
View Patent ↗An improvement is disclosed in the method for producing a multifilament (Nb, Ti) 3 Sn superconducting wire by the steps of preparing a plurality of Nb or Nb alloy rods where Nb or Nb alloy monofilaments are encased in copper or copper alloy sheaths; packing the Nb or Nb alloy rods within a copper containing matrix to form a packed subelement for the superconducting wire; providing sources of Sn, and sources of Ti within said subelement; assembling the subelements within a further copper containing matrix; and diffusing the Sn and Ti into the Nb or Nb alloy rods to form (Nb, Ti) 3 Sn. The method is improved by diffusing the Ti into the Nb from a minor number of Ti dopant source rods which are distributed among the Nb or Nb alloy rods.
1. A method for producing a multifilament (Nb, Ti) 3 Sn superconducting wire comprising the steps of:
a) packing a plurality of Nb or Nb alloy rods within a copper containing matrix to form a packed subelement for said superconducting wire;
b) packing Ti dopant source rods amongst the Nb or Nb alloy rods in the copper containing matrix;
c) providing sources of Sn accessible for diffusion into the Nb or Nb alloy rods;
d) assembling said subelements within a further copper containing matrix,
e) reducing said assemblage from step d) to wire form; and
f) diffusing the said Sn and said Ti into the Nb or Nb alloy rods to form (Nb, Ti) 3 Sn.
2. A method in accordance with claim 1 wherein in step a) said Nb or Nb alloy rods are ensheathed in a copper or copper alloy.
3. A method in accordance with claim 1 , wherein said Ti dopant source rods comprise Ti or Ti alloy rods in copper or copper alloy sheaths.
4. A method in accordance with claim 3 , wherein a Nb diffusion barrier is provided between the Ti or Ti alloy rod and the copper sheath.
5. A method in accordance with claim 3 wherein the number of said Ti dopant source rods is small compared to the number of said Nb or Nb alloy rods.
6. A method in accordance with claim 5 wherein said Ti dopant source rods are symmetrically distributed among the said Nb or Nb alloy rods.
7. A method in accordance with claim 1 , wherein the Sn is diffused into said Nb or Nb alloy rods by an internal Sn process.
8. A method in accordance with claim 7 , wherein said Sn sources are within said subelements.
9. A method in accordance with claim 7 , wherein said Sn sources are adjacent to said subelements.
10. A method in accordance with claim 7 , wherein the extruded subelement from step (d) are gundrilled and the resulting holes filled with said Sn or Sn alloy.
11. A method in accordance with claim 10 , wherein the totality of the subelements are surrounded by a single diffusion barrier.
12. A method in accordance with claim 1 , wherein the Sn is diffused into said Nb or Nb alloy rods by the bronze process.
13. A method in accordance with claim 10 , where each subelement has a diffusion barrier.
14. A method in accordance with claim 10 wherein the extruded subelements from step ( 1 d ) are gundrilled, filled with salt, restacked, extruded again, and the salt replaced with Sn or Sn alloy.
15. A method in accordance with claim 2 , wherein the encased Nb or Nb alloy rods are formed into hexed cross sectioned rods for use in packing the subelement.
16. A method in accordance with claim 3 , wherein the Ti dopant source rods are formed into a hexagonal cross section to enable their packing among the hexed Nb or Nb alloy rods.
17. A method in accordance with claim 1 , wherein in step (d) the subelements are hexed in cross-section.
18. A method in accordance with claim 1 , wherein in step (a) the Nb or Nb alloy rods are emplaced at holes drilled in said matrix.
19. A method in accordance with 18 wherein said matrix comprises Cu—Sn alloy.
20. A method in accordance with 18 wherein said matrix comprises Cu.
21. A method in accordance with claim 18 , wherein said Ti dopant source rods are inserted at further holes drilled in said matrix.
22. A method in accordance with claim 5 , wherein said Ti dopant source rods are placed strategically in the subelement to separate superconducting regions to reduce the effective filament diameter and AC losses.