Method for producing a superconductive element
The invention relates to a method for producing a superconductive element to be used as a wire-in-channel superconductor in magnetic resonance imaging (MRI) and in nuclear magnetic resonance (NMR) applications, which superconductive element contains a superconductive wire and a copper component having a longitudinal groove and the superconductive wire being positioned in the groove. In order to produce the wire-in-channel superconductive element by a mechanical contact between the superconductive wire and a wall of the groove in the copper component, at least one contact surface is coated with a lead free solder material before having the mechanical contact. In order to enhance the thermal and electrical conduction and to create a bond between the said components the soldering material is fused in annealing process step.
1. Method for producing a superconductive element to be used as a wire-in-channel superconductor in magnetic resonance imaging (MRI) and in nuclear magnetic resonance (NMR) applications, comprising the steps of:
providing a superconductive wire and a copper component having a longitudinal groove;
positioning the superconductive wire in the groove;
creating mechanical contact with at least one contact surface between the superconductive wire and a wall of the groove in the copper component;
deforming to produce an intimate contact between the at least one contact surface;
annealing the deformed superconductive wire and copper component at a temperature higher than the solidus temperature of a lead free solder material to achieve a metallic or intermetallic interface between the wire and the wall or the walls of the groove;
wherein the at least one contact surface is coated with the lead free solder material before having the mechanical contact;
wherein the lead free solder material is in contact with the superconductive wire;
wherein the lead free solder material is a tin based alloy;
wherein the tin based alloy is a binary alloy of tin-bismuth in which the bismuth content is 20 to 60% by weight; and
wherein the binary alloy of tin-bismuth is alloyed with one or two components from the group of copper, silver, zinc, antimony and indium so that the content of each alloyed component is 0.1 to 20% by weight and the rest being tin or tin and impurities.
2. Method according to the claim 1 , wherein the superconductive wire is coated with the lead free solder material.
3. Method according to the claim 1 , wherein the wall of the groove in the copper component is coated with the lead free solder material.
4. Method according to the claim 1 , wherein the superconductive wire and the wall of the groove in the copper component are coated with the lead free solder material.
5. Method according to claim 1 , wherein the contact surface is coated using electroplating techniques.
6. Method according to claim 1 , wherein the at least one contact surface is coated using hot tinning techniques.
7. Method according to claim 1 , wherein the at least one contact surface is coated using chemical vapour deposition techniques.
8. Method according to claim 1 , wherein the at least one contact surface is coated using physical vapour deposition techniques.
9. Method according to the claim 1 , wherein the annealing is carried out by batch annealing.
10. Method according to the claim 1 , wherein the annealing is carried out by forced flow convection tube annealing.
11. Method according to the claim 1 , wherein the annealing is carried out by strand annealing.
12. Method according to the claim 1 , wherein the annealing is carried out by inductive annealing.
13. Method according to the claim 1 , wherein the annealing is carried out by resistive annealing.
14. Method according to the claim 1 , wherein the content of each alloyed component is 0.1 to 5% by weight.
15. A superconductive element to be used as a wire-in-channel superconductor in magnetic resonance imaging (MRI) and in nuclear magnetic resonance (NMR) applications produced using the method according to claim 1 .
16. The superconductive element of claim 15 , wherein the content of each alloyed component is 0.1 to 5% by weight.