Coupled NMR Probe Resonators for Lossy Sample SNR
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Solution Overview
Problem
Existing NMR measuring heads face challenges in achieving a high signal-to-noise ratio (SNR) for lossy samples, particularly due to inhomogeneous static magnetic fields and dielectric losses, which limit the exploitation of high fill factors and lead to reduced sensitivity in measurements.
Innovation Solution
The NMR measuring head distributes the measurement substance across multiple smaller samples, each positioned optimally within a resonator system to achieve a coupled resonator mode, utilizing a common receiver circuit and positive mutual inductance between resonator systems to enhance the signal-to-noise ratio by optimizing the number and arrangement of basic elements and resonator systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single large sample is measured in one resonator system, then the total amount of measurement substance is maximized, but the signal-to-noise ratio deteriorates due to dielectric losses and inhomogeneous magnetic fields
Solution Approach 1:
The invention divides a single large measurement sample into multiple smaller sub-samples, each placed in a separate resonator system. This segmentation allows each sub-sample to be optimally positioned in the homogeneous magnetic field region, reducing dielectric losses while maintaining adequate total measurement substance volume across all resonators.
Solution Approach 2:
Multiple resonator systems are coupled together to form a composite resonator structure, where individual resonators are nested or arranged in specific geometries (e.g., birdcage design) to create a unified magnetic field environment that enhances signal-to-noise ratio while accommodating multiple samples.
2Measurement precision
If the fill factor is increased by using torus resonators, then the sensitivity is improved, but the static magnetic field homogeneity deteriorates and cannot be compensated by shimming
Solution Approach 1:
Instead of using a single torus resonator with high fill factor but poor field homogeneity, the invention segments the measurement into multiple smaller resonators where each can maintain optimal field homogeneity. The segmented approach allows independent optimization of field homogeneity in each resonator while achieving high overall sensitivity through the combined signal from multiple resonators.
3Productivity
If multiple measurement samples are introduced into separate resonator systems, then the measurement time is reduced, but the device complexity increases due to multiple independent receiver circuits
Solution Approach 1:
Multiple resonator systems are electromagnetically coupled to operate as a unified resonant structure, allowing all resonators to be excited and detected through a single receiver circuit. This merging approach enables simultaneous measurement of multiple samples while avoiding the complexity of multiple independent receiver circuits, as the coupled resonators share a common detection pathway.
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 significantly improves the signal-to-noise ratio by distributing noise evenly across multiple samples, allowing for better positioning and homogenization of the magnetic field, thereby achieving superior sensitivity compared to single-sample measurements, especially for lossy substances like water and salty solutions.
Implementation Method 1
the N resonator systems of the N basic elements being interconnected by electromagnetic coupling to set up the coupled mode
Implementation Method 2
nuclear magnetic resonance (=NMR) measuring head, comprising N basic elements, with N ≥ 2, each basic element having a cylindrical measurement sample and a resonator system
Data Source
Figure 1a~2b
Figure 3a~3c
Figure 3d~3e
AI summary
A nuclear magnetic resonance (NMR) measuring head comprising N basic elements (10a, 10b, 10c), with N ≥ 2, wherein each basic element (10a, 10b, 10c) has a cylindrical measuring sample (11) and a resonator system (12a, 12b, 12c), and wherein the N resonator systems (12a, 12b, 12c) of the N basic elements (10a, 10b, 10c) are coupled to each other, is characterized in that a coupling network is provided for the N resonator systems (12a, 12b, 12c), with which the entirety of the N resonator systems (12a, 12b, 12c) can be operated in an identical, coupled mode during transmission and reception, wherein the coupling network for the entirety of the N resonator systems (12a, 12b, 12c) comprises a common receiver circuit. With the NMR measuring head according to the invention, a better signal-to-noise ratio can be achieved with lossy samples than with measuring heads according to the prior art.