MRI Magnet Solder Joint Structure for Brittle Superconducting Wires
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Solution Overview
Problem
Joining segments of superconducting wire, particularly those made from brittle materials like magnesium diboride, poses challenges due to the difficulty in creating low-resistance, reliable, and repeatable joints that maintain superconductivity and mechanical integrity, which is crucial for MRI systems.
Innovation Solution
A magnetic resonance imaging magnet assembly is designed with a brace embracing two superconducting wires, a sleeve slid over the brace, and a hardened soldering material applied between them, ensuring mechanical stability and low electrical resistance through a specific configuration and materials selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If superconducting wire segments are joined using conventional methods, then the coil can be constructed from available wire lengths, but the joints exhibit electrical resistance that disrupts superconductivity and generates heat
Solution Approach 1:
The patent changes the physical state of the soldering material from solid to liquid during the joining process by heating it to its melting point, then allows it to solidify in a controlled manner to create a low-resistance joint. This parameter change enables the solder to flow and penetrate the wire interfaces effectively, forming a reliable superconducting connection.
Solution Approach 2:
The soldering material undergoes phase transition from solid to liquid and back to solid. When heated to melting temperature, the solder becomes liquid and penetrates the wire interfaces. Upon cooling, it solidifies to form a strong mechanical and electrical bond that maintains superconductivity with minimal resistance.
2Temperature
If brittle superconducting materials like magnesium diboride are used to achieve high magnetic fields at higher temperatures, then the operating temperature can be increased, but the materials become prone to cracking and breaking under mechanical stress
Solution Approach 1:
The patent applies a flexible coating or protective layer to the brittle superconducting wire before joining. This protective layer cushions the wire against mechanical stress and thermal expansion differences during the soldering process, preventing cracking and breaking of the brittle material while allowing the joint to be formed.
Solution Approach 2:
The patent uses composite construction where the brittle superconducting material is combined with more ductile materials in the joint structure. The soldering material and surrounding structural elements form a composite assembly that provides mechanical support and stress distribution, protecting the brittle superconducting core while maintaining electrical superconductivity.
3Ease of manufacture
If liquid metal solvent is used to remove copper and liberate superconductive strands for soldering, then the superconductive strands can be joined, but the process becomes complex and difficult to control
Solution Approach 1:
Instead of using liquid metal solvent to remove copper and liberate superconductive strands, the patent extracts or removes the need for this complex chemical process entirely. The design allows for direct soldering of the superconducting wire segments using appropriate superconducting solder materials, eliminating the multi-step chemical treatment process and simplifying the manufacturing procedure.
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
The assembly achieves low-resistance joints that maintain superconductivity, reducing heat generation and enhancing the reliability of MRI systems, especially in persistent mode operation.
Implementation Method 1
heating it to a temperature corresponding to a melting point of the soldering material
Implementation Method 2
these coils must be made from long lengths of wire... where they exhibit superconductivity, i.e. zero electrical resistance
Data Source
Figure 1a~2c
Figure 3
Figure 4~5
AI summary
The invention discloses a method of manufacturing a magnet assembly (1), comprising: providing two wires (2) each comprising a superconducting material; embracing the two wires (2) with a brace (3); sliding a sleeve (4) over the brace (3); filling a soldering material (5) into the interior of the brace (3); heating up the soldering material (5) to its soldering temperature; and letting the soldering material (5) cool down for hardening. In this way, an easy to apply possibility for producing good solder joints in a convenient and repeatable fashion even for brittle conductors is provided.