Superconducting Wire Filament Twist Angle Optimization

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Solution Overview

Problem

Superconducting wires, particularly those made of Nb3Sn, exhibit a significant dependence of critical current on axial expansion at high magnetic fields due to lattice distortion, leading to inefficiencies in magnet construction and increased costs.

Innovation Solution

The superconducting filaments are twisted to an angle of approximately 58° relative to the wire axis, minimizing lattice distortion and maintaining a maximum critical current regardless of external axial strain.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If superconducting filaments are twisted to reduce coupling currents, then stability against magnetic field changes is improved, but the critical current becomes highly sensitive to axial strain

Engineering Contradiction:
Improvestability against magnetic field changesVSAvoidcritical current sensitivity to axial strain
Core Design Contradiction:
Stability of the object's compositionVSReliability

Solution Approach 1:

The patent applies parameter changes by optimizing the twist length to a specific value (15mm) that simultaneously reduces coupling currents and minimizes axial strain sensitivity. This involves changing the geometric parameter (twist length) to achieve a balance between two conflicting requirements: stability against magnetic field changes and reliability of critical current under axial strain.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If wire length is increased to accommodate strain-dependent critical current, then magnetic field performance is maintained, but manufacturing cost and device complexity increase

Engineering Contradiction:
Improvemagnetic field performanceVSAvoidwire length requirements
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses parameter changes by optimizing the twist length to maximize critical current while minimizing axial strain sensitivity. This allows the use of shorter wire lengths to achieve the same magnetic field performance, thereby reducing manufacturing costs and device complexity without compromising reliability.

Inventive Principle:
Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach reduces the dependence of the critical current on axial expansion, allowing for more efficient use of superconducting wire, reducing required lengths and costs, and enabling more compact magnet designs with reduced electromagnetic forces.

Implementation Method 1

the distortion of the crystallographic lattice of the current-carrying filaments becomes independent of an external axial strain

Methodology Applied
Scientific EffectLattice distortion:

Implementation Method 2

The critical current has a maximum value for a purely cubic Nb3Sn lattice, i.e. without distortion

Methodology Applied
Scientific EffectSuperconductivity: Superconductivity

Data Source

PatentEP2927974B8Method for making superconductors with reduced dependence of the critical current of axial mechanical expansion
Publication Date: 2017.12.20 BRUKER BIOSPIN AG

AI summary

A method for producing a superconducting wire with a plurality of filaments, at least some of which are twisted around the wire axis, is characterized in that the superconducting filaments are twisted such that the majority of the filaments are at a twist angle greater than 50° with respect to the wire axis. This makes it possible, using simple technical means, to significantly reduce the strong dependence of the critical current of a superconducting wire at high magnetic fields as a function of axial strain. Furthermore, the invention enables the dependence of the critical current of a superconducting wire at high magnetic fields as a function of axial strain to be largely eliminated with a corresponding arrangement of the superconducting filaments.