Superconducting Magnet Coil Coupling for Field Homogeneity
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Solution Overview
Problem
Superconducting magnet systems face issues with magnetic field homogeneity and induced currents/voltages due to unsymmetric coil pairs, which affect imaging quality and coil insulation integrity, especially under gradient pulses.
Innovation Solution
The integrated coil winding concept involves serially connecting coil segments in an alternating pattern to form electrically symmetric pairs, reducing induced currents and voltages, and adding insulation layers to ensure coil integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coils are physically asymmetric about the mid-plane axis, then field homogeneity deteriorates, but if coils are made asymmetric to reduce induced currents, then field homogeneity suffers
Solution Approach 1:
The patent applies asymmetry by making the coil pairs electrically asymmetric through unsymmetric serial coupling about the mid-plane axis. This intentional asymmetry in the electrical connection pattern creates equal and opposite electromotive forces that cancel each other out, eliminating net induced currents while maintaining field homogeneity through proper magnetic coupling design.
Solution Approach 2:
The patent changes the electrical connection parameters by switching from symmetric to unsymmetric serial coupling configurations. By altering how the coils are electrically connected (changing the circuit topology parameters), the system achieves cancellation of induced currents while preserving the magnetic field homogeneity through controlled electromagnetic parameters.
2Productivity
If gradient pulses are applied to generate electromotive forces, then imaging capability is improved, but induced voltages accumulate damaging the coil insulation
Solution Approach 1:
The patent converts the harmful effect of gradient-induced electromotive forces into a beneficial cancellation mechanism. By designing the coil pairs with unsymmetric serial coupling, the electromotive forces generated during gradient pulses create equal and opposite induced currents that cancel each other, transforming what would be damaging voltage accumulation into a self-neutralizing effect that protects the insulation.
Solution Approach 2:
The patent implements preliminary anti-action by pre-configuring the coil pairs with unsymmetric electrical coupling before gradient pulses are applied. This pre-established asymmetric connection pattern creates a built-in cancellation mechanism that actively counteracts the harmful voltage accumulation from gradient pulses before damage can occur to the insulation.
3Reliability
If symmetric coil pairs are used, then field homogeneity is maintained, but induced currents accumulate affecting B0 field stability
Solution Approach 1:
The patent resolves this contradiction by introducing controlled asymmetry in the electrical coupling configuration. The unsymmetric serial coupling pattern about the mid-plane axis breaks the symmetry that would otherwise allow induced current accumulation, while the magnetic field geometry maintains homogeneity. This asymmetric electrical connection creates opposing electromotive forces that cancel, preserving both field homogeneity and B0 stability.
4Stability of the object's composition
If unsymmetric coil coupling is used to reduce induced currents, then B0 field stability is improved, but coil insulation is exposed to partial discharges
Solution Approach 1:
The patent converts the potential harm of voltage stress during gradient pulses into a protective mechanism. The unsymmetric serial coupling configuration causes voltage peaks to occur at different times in each coil, and the resulting opposing electromotive forces cancel the harmful voltage accumulation, preventing partial discharges and insulation aging while maintaining B0 stability.
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 maintains magnetic field homogeneity, reduces induced currents and voltages, and enhances coil insulation, improving imaging quality and stability.
Implementation Method 1
A z-gradient pulse can generate electromotive forces in each turn of the magnet coils (e=−dΦ/dt). The electromotive forces can accumulate in the magnet coils, which can result in induced currents or induced voltages in the coils
Implementation Method 2
The magnet is cooled down to liquid helium temperature (4.2 K) so that the conductors are operated at their superconducting state
Implementation Method 3
The heat loads of the magnet, such as that produced by the radiation and conduction from the environment, are removed by either the boil-off of liquid helium in an 'open system' or by a 4 K cryocooler in a 'closed system'
Implementation Method 4
The heat loads of the magnet, such as that produced by the radiation and conduction from the environment
Data Source
AI summary
A system and method for connecting superconducting magnet coils made up of coil segments to allow an integrated winding concept. The integrated winding concept can include serially connecting coil segments of coil pairs in an alternating pattern, which causes coil pairs to be electrically symmetric. Symmetric coil pairs can eliminate or significantly reduce the currents in magnet coils induced by gradient or other pulses, produce a homogenous field, and reduce the accumulated voltages in the coils due to gradient pulsing.