NMR Shim Positioning Control for Temperature-Induced Drift
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Solution Overview
Problem
Temperature-induced fluctuations cause relative movement between the superconducting magnet and the room temperature (RT) shim elements, leading to instability in magnetic field homogeneity in NMR systems, which is not effectively addressed by existing technologies.
Innovation Solution
Implementing regulating elements, such as mechanical actuators, heating or cooling elements, and temperature-controlled fluids along the path between the vacuum vessel and the shim system to stabilize temperature and minimize strain changes, thereby maintaining field homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the RT shims are mechanically connected to the superconducting magnet via a long path extending through temperature fluctuation zones, then the shim system can be positioned outside the vacuum vessel for easier access, but temperature-induced thermal expansion causes relative movement between the magnet and shims, deteriorating field homogeneity
Solution Approach 1:
A temperature-regulating element is introduced as an intermediary component in the mechanical connection path between the superconducting magnet and the RT shims. This intermediary actively compensates for thermal expansion by regulating temperature or strain, thereby preventing relative movement while maintaining the extended mechanical path that allows external shim positioning
Solution Approach 2:
The patent applies parameter changes by actively regulating temperature or strain in the mechanical connection path. By controlling the temperature parameter (or alternatively the strain parameter) in the region between the magnet and shims, the system compensates for thermal expansion effects and maintains stable relative positioning, thus preserving field homogeneity while allowing external shim access
2Manufacturing precision
If temperature regulation is applied to the mechanical connection path, then field homogeneity is maintained, but device complexity increases due to additional regulating elements
Solution Approach 1:
Temperature regulation is applied locally only to the specific mechanical connection path between the superconducting magnet and the RT shims, rather than regulating the entire system. This localized approach maintains field homogeneity where needed while minimizing the overall complexity of the system by limiting the scope of active temperature control to only the critical region
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
Stabilizes the magnetic field homogeneity by minimizing relative movement between the superconducting magnet and the shim system, even in varying temperature conditions, using cost-effective and simple technical means.
Implementation Method 1
The second and third parts of the path change their length due to their thermal expansion when the temperature changes.
Implementation Method 2
a superconducting magnet arranged within a vacuum vessel in the cold region of a cryostat
Data Source
AI summary
An NMR apparatus having a magnet coil system for generating a homogeneous magnetic field comprises a superconducting magnet arranged within a vacuum vessel in the cold region of a cryostat, and a shim system containing shim elements arranged outside the vacuum vessel. The superconducting magnet has a first mechanical connection point to the vacuum vessel via a magnet suspension, and the shim system has a second mechanical connection point to the vacuum vessel via a positioning element. On at least one portion of a path along the vacuum vessel from the first connection point to the second connection point and/or on at least one portion of a path along the positioning element from the second connection point to the shim system, a regulating element for regulating thermally caused changes in length is arranged on the relevant path. Magnetic field homogeneity can thus be kept largely stable.