NMR Shim Position Compensation for Temperature-Induced Drift
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Solution Overview
Problem
Temperature fluctuations cause relative movement between superconducting magnets and shim systems in NMR apparatuses, leading to instability in magnetic field homogeneity, which is challenging to maintain, especially in variable temperature conditions.
Innovation Solution
Incorporating a regulating element along the path between the mechanical connection points of the vacuum container and the shim system, such as mechanical actuators, heating or cooling elements, and temperature-controlled fluids, to minimize strain and temperature changes, thereby stabilizing the magnetic field homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the superconducting magnet is mechanically connected to the RT shims via a long path through the cryostat, then the shim system can be positioned outside the vacuum vessel, but temperature fluctuations cause thermal expansion that leads to relative movement between the magnet and shims, deteriorating field homogeneity
Solution Approach 1:
A regulating element is introduced as an intermediary component in the mechanical connection path between the superconducting magnet and the RT shims. This regulating element actively compensates for thermal expansion effects, maintaining stable relative positioning despite temperature fluctuations, thus resolving the contradiction between accessible shim positioning and stable field homogeneity
Solution Approach 2:
The regulating element modifies the mechanical parameters (length, position) of the connection path dynamically in response to temperature changes. By adjusting these parameters, the system compensates for thermal expansion and prevents relative movement between the magnet and shims, maintaining field homogeneity while allowing external shim positioning
2Reliability
If ambient temperature fluctuations occur, then the mechanical path length changes due to thermal expansion, but continuously adjusting RT shim currents to compensate increases energy consumption and system complexity
Solution Approach 1:
The patent replaces the electrical adjustment mechanism (continuously varying RT shim currents) with a mechanical compensation mechanism (regulating element that physically adjusts path length). This mechanical substitution provides passive or semi-passive compensation for thermal expansion, reducing the need for continuous electrical adjustments and associated system complexity
Solution Approach 2:
The regulating element is designed to automatically compensate for thermal expansion effects without requiring external control systems. The element self-adjusts its properties (length, position) in response to temperature changes, providing autonomous compensation that reduces system complexity while maintaining field homogeneity
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 relative movement between the superconducting magnet and the shim system, maintaining stable field homogeneity even with changing ambient or system temperatures, reducing the need for continuous adjustments and improving the precision of NMR measurements.
Implementation Method 1
The second and third parts of the path change their length due to their thermal expansion when the temperature changes. Consequently, relative movement occurs between the superconducting magnet and the RT shims.
Implementation Method 2
heating or cooling elements, and temperature-controlled fluids, to minimize strain and temperature changes
Implementation Method 3
heating or cooling elements, and temperature-controlled fluids, to minimize strain and temperature changes
Data Source
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AI summary
An NMR apparatus with a magnet coil system for generating a homogeneous magnetic field, comprising a superconducting magnet (1) arranged in the cold region of a cryostat within a vacuum vessel (8), and comprising a shim system (7) containing shim elements (6) arranged outside the vacuum vessel, wherein the superconducting magnet has a first mechanical connection point (11) with the vacuum vessel via a magnet suspension (3), and wherein the shim system has a second mechanical connection point (10) with the vacuum vessel via a positioning element (5);12) is characterized in that a regulating element (13) for regulating thermally induced length changes on the relevant path is arranged on at least one section of a path along the vacuum vessel from the first connection point to the second connection point and/or on at least one section of a path along the positioning element from the second connection point to the shim system. This allows the magnetic field homogeneity to be kept largely stable and constant even under changing temperature conditions within and in the vicinity of the apparatus.