Halbach Magnet Ring Assembly for MR Field Homogeneity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing permanent magnet systems for magnetic resonance applications face challenges in achieving homogeneous magnetic fields with fewer mechanical shim degrees of freedom, leading to complex and costly adjustment processes, and often require additional shielding due to stray fields and finite length of Halbach arrangements.
Innovation Solution
A magnet arrangement featuring prefabricated, firmly bonded ring-shaped Halbach magnet segments that are adjustable in position and orientation, reducing the number of mechanical degrees of freedom to a minimum, allowing for simpler homogenization and assembly, with a support structure that secures the magnets against unwanted movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If all magnet segments are adjustable to correct field inhomogeneities, then field homogeneity is improved, but the number of degrees of freedom increases enormously making the adjustment process extremely complex and time-consuming
Solution Approach 1:
The magnet system is divided into multiple independent rings, each ring consisting of several magnet segments. By adjusting the position and orientation of entire rings rather than individual segments, the patent reduces the number of degrees of freedom while maintaining field homogeneity correction capability. Each ring can be independently positioned and rotated, providing sufficient control with fewer adjustable parameters.
Solution Approach 2:
Multiple magnet segments within each ring are firmly bonded together to form rigid ring structures. This merging of segments into unified rings reduces the total number of adjustable components while preserving the ability to correct field inhomogeneities through ring-level adjustments, thereby simplifying the overall adjustment process.
2Object-generated harmful factors
If traditional yoke designs with rectangular frames are used, then magnetic flux is contained, but stray fields extend far beyond the outer contours requiring additional shielding
Solution Approach 1:
The patent employs curved or arc-shaped magnet arrangements instead of traditional rectangular yoke designs. This curvature helps contain magnetic flux within a more compact volume and reduces the extent of stray fields extending beyond the magnet assembly, thereby minimizing or eliminating the need for additional external shielding structures.
3Manufacturing precision
If correction mechanisms are added to compensate for tolerances in magnet material and positions, then field homogeneity is improved, but the mechanical structure becomes more complex
Solution Approach 1:
The patent incorporates adjustable and movable components that allow dynamic positioning of magnet rings during assembly and operation. This dynamic capability enables compensation for manufacturing tolerances in magnet material and positioning without requiring complex rigid correction mechanisms, as the system can be adapted to achieve optimal field homogeneity through controlled adjustments.
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 simplifies the homogenization process, reduces the complexity and cost of assembly, and achieves efficient use of magnetic material by minimizing stray fields and allowing for effective mechanical shimming with fewer degrees of freedom.
Implementation Method 1
the ring-shaped magnet elements each having a Halbach magnetization which generates a magnetic dipole field
Implementation Method 2
permanent magnet system for generating a homogeneous magnetic field in a direction perpendicular to a z-axis in a measurement volume
Data Source
Figure 1a~1b
Figure 2~3b
Figure 4~6
AI summary
A magnet arrangement (1) with a permanent magnet system comprising at least two cylindrically symmetrical and stacked one above the other in the z-direction and/or concentrically arranged ring-shaped magnet elements (2) made of individual magnet segments (3), which are arranged such that the magnetization direction of the individual segments in the rings runs parallel in an xy-plane perpendicular to the z-direction, wherein the magnet elements are alignable relative to each other in the z-direction and have a Halbach magnetization, is characterized in that the ring-shaped magnet elements are already prefabricated in the magnetic resonance apparatus prior to final assembly and their respective magnet segments are fixed immovably relative to each other, arranged to be displaceable relative to each other in the xy-plane and mounted to be rotatable and/or tiltable relative to each other.This makes a multi-ring MR device in a Halbach configuration significantly easier to assemble and therefore considerably less expensive to manufacture. At the same time, the magnetic field gradients resulting from the assembly can be easily minimized. Thus, a Halbach arrangement is proposed that requires significantly fewer mechanical shim degrees of freedom.