NMR Sample Container Geometry for Field Homogeneity
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Solution Overview
Problem
Conventional NMR measuring configurations face challenges in minimizing magnetic field inhomogeneities caused by susceptibility jumps at the interfaces between the sample container and the sample substance, leading to residual fields that affect measurement quality, particularly in high-resolution NMR spectroscopy.
Innovation Solution
The geometry of the sample container is designed to allow larger location-dependent relative field changes that can be compensated by conventional shim coil systems, minimizing residual fields in the center and lower partial volumes, while optimizing the shape to reduce the overall sample volume and improve measurement sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sample container has conventional geometry, then the magnetic field inhomogeneities are minimized, but residual fields remain that affect measurement quality
Solution Approach 1:
The patent applies parameter changes by optimizing the geometric parameters of the sample container (radii, heights, curvature) to minimize residual fields. The container geometry is defined by specific parameters (R1, R2, h1, h2, etc.) that are optimized to reduce magnetic susceptibility effects at interfaces, thereby improving measurement precision while eliminating harmful residual fields.
Solution Approach 2:
The patent implements local quality by creating different geometric zones within the sample container. The container has varying curvature and thickness in different regions (e.g., hemispherical bottom vs. cylindrical side walls vs. flat top) to locally optimize field homogeneity in specific areas, particularly at the interfaces where susceptibility jumps occur.
2Measurement precision
If the sample container geometry is optimized to reduce residual fields, then measurement quality improves, but the design complexity increases
Solution Approach 1:
The sample container is segmented into distinct geometric zones: a hemispherical bottom portion, a cylindrical side wall portion, and a flat or curved top portion. This segmentation allows each zone to be optimized independently for its specific function while maintaining overall field homogeneity, reducing the complexity of designing a completely new monolithic shape.
Solution Approach 2:
The patent employs spheroidal geometry (hemispherical bottom) to eliminate sharp edges and corners that would create localized field inhomogeneities. The curved surfaces provide smooth transitions that reduce magnetic susceptibility effects, achieving field homogeneity through geometric curvature rather than complex multi-component structures.
3Measurement precision
If conventional sample containers are used, then manufacturing is simple, but larger sample volumes are required to achieve acceptable signal quality
Solution Approach 1:
The optimized container geometry parameters (smaller radii, reduced heights) directly reduce the total sample volume required. By changing the geometric parameters to minimize residual fields, the patent achieves acceptable signal quality with less sample material, directly addressing the quantity of substance parameter.
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 enables more effective compensation of field inhomogeneities, reducing residual fields to below 1.6 ppb in the center and 30 ppb in the lower partial volumes, thereby enhancing the quality of NMR signals and reducing the required sample volume.
Implementation Method 1
the material of the sample container has a magnetic susceptibility of χ2, an environment of a magnetic susceptibility of χ1, in which the sample container is arranged, and a sample substance which is contained in the sample container has a magnetic susceptibility of χ3
Implementation Method 2
The cylindrical inner space also contains shim coils, gradients, and radio frequency coils, which are arranged in this inner space at different radii around a sample container
Data Source
AI summary
A sample container (2) for NMR measurements defines a volume (V) of sample substance. The sample container (2) has a first interface (G1) towards an environment (1) and a second interface (G2) towards the sample substance (3). A susceptibility jump at the second interface G2 is sufficiently large that the maximum value of |B′G2/B0| within the volume (V) is at least 0.5 ppm. The geometry of the sample container (2) is selected in such a fashion that, when a homogeneous magnetic field B0 has been applied, a location-dependent relative field change F is present in the volume (V), which is larger than 20 ppb at least at one point in a center partial volume (V1) and a first residual field (R1) in the center partial volume (V1) is smaller than 1.6 ppb. A second residual field (R2a) in the lower partial volume (V2a) is smaller than 30 ppb.