Superconducting Magnet Coil Local Shielding for AC Loss Reduction
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Solution Overview
Problem
Superconducting magnet systems in MRI systems face increased heat loads and AC losses due to gradient AC field penetration, which raises operating costs and compromises gradient system performance.
Innovation Solution
A superconducting wire is positioned along portions of the superconducting magnet coil to form a closed conductive path that magnetically couples with gradient magnetic fields, creating a local shielding effect to reduce AC losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If large volume shield gradients are used to reduce gradient AC field penetration into the superconducting magnet, then AC losses are reduced, but gradient system performance is significantly compromised
Solution Approach 1:
The patent divides the shielding function into multiple discrete gradient shielding loops positioned at specific locations around the superconducting magnet coils, rather than using a single large volume shield. Each loop is segmented to target specific gradient field directions (Gx, Gy, Gz), allowing localized shielding without compromising overall gradient performance in the imaging volume.
Solution Approach 2:
The patent applies shielding selectively at specific locations where gradient AC field penetration is most problematic, rather than uniformly throughout the entire magnet volume. The gradient shielding loops are positioned proximate to the superconducting magnet coils where AC losses occur, providing local shielding quality where needed while maintaining gradient system performance in the imaging volume.
2Temperature
If gradient AC field penetration into the superconducting magnet is minimized, then heat load is reduced, but shielding effects may impact the performance of the gradient system
Solution Approach 1:
The patent introduces gradient shielding loops as intermediary elements between the gradient coils and the superconducting magnet coils. These loops act as mediators that intercept and redirect gradient AC fields before they penetrate into the superconducting magnet, reducing heat load while allowing the gradient system to maintain its performance characteristics in the imaging volume.
Solution Approach 2:
The gradient shielding loops are designed to replicate the functional characteristics of the main gradient coils on a smaller scale, creating localized copies of the gradient field structure. This allows the shielding loops to effectively couple with and counteract gradient AC fields without introducing significant disturbances to the overall gradient system performance.
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 solution effectively minimizes AC field penetration into the superconducting magnet, reducing heat loads and maintaining gradient system performance without significant impact on the imaging volume.
Implementation Method 1
the plurality of arcs configured to magnetically couple with a gradient magnetic field generated by a magnetic field gradient of a first direction to locally shield the first superconducting magnet coil
Implementation Method 2
when superconducting coils are exposed to an AC field, hysteresis loss and eddy currents are induced therein that contribute to AC losses
Implementation Method 3
A superconducting wire is positioned along portions of the superconducting magnet coil to form a closed conductive path that magnetically couples with gradient magnetic fields, creating a local shielding effect
Data Source
AI summary
A method and apparatus for local grading shielding includes a gradient shield loop having a plurality of arcs positioned adjacent to a superconducting magnet coil. The plurality of arcs magnetically couple with a gradient magnetic field generated by a magnetic field gradient to locally shield the superconducting magnet coil.