Saddle Coil Assembly for Magic Angle Adjustment in Solid-State NMR
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Solution Overview
Problem
Conventional NMR apparatuses face challenges in achieving high-resolution spectra of solid samples due to anisotropic effects of internal nuclear spin interactions, which are not adequately addressed by mechanical adjustments of the magic angle, leading to broad resonance lines and overlapping chemical species, and existing electrical adjustments using Helmholtz saddle coils result in undesirable frequency shifts.
Innovation Solution
The use of a Helmholtz saddle coil assembly with optimized dimensions and shape, where the ratio of coil length to diameter is within a specific range (1.91≤2L/2a≤2.15 or 1.99≤2L/2a≤2.02, to produce a uniform magnetic field, allowing for accurate electrical adjustment of the magic angle without increasing linewidths and minimizing frequency shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical adjustment of the magic angle is used, then the sample can be positioned at the required angle, but the adjustment precision is insufficient leading to broad resonance lines
Solution Approach 1:
The patent replaces the mechanical adjustment system with an electrical field-based system. A pair of saddle coils generates a magnetic field that tilts the effective magnetic field direction, allowing precise electronic control of the magic angle without mechanical moving parts. This substitution eliminates mechanical errors and achieves superior angular precision.
Solution Approach 2:
The patent changes the control parameter from mechanical position to electrical current. By adjusting the current through the saddle coils, the magnetic field strength and direction are precisely controlled, enabling fine-tuning of the magic angle. This parameter transformation allows continuous and precise adjustment beyond mechanical limitations.
2Ease of operation
If conventional Helmholtz saddle coils are used for electrical adjustment, then the magic angle can be adjusted electrically, but frequency shifts occur in the NMR spectrum
Solution Approach 1:
The patent optimizes the local geometric properties of the saddle coils. By carefully designing the coil dimensions (radius R and height H with specific ratios) and winding configurations, the magnetic field is concentrated and optimized in the sample region. This local optimization ensures uniform field distribution that minimizes frequency shifts while maintaining electrical adjustability.
Solution Approach 2:
The patent preemptively compensates for potential frequency shift issues by designing the coil geometry to produce a highly uniform magnetic field from the outset. The specific dimensional ratios and symmetric winding patterns are predetermined to cancel out field inhomogeneities before they can cause frequency shifts, preventing the problem rather than correcting it.
3Ease of manufacture
If the coil dimensions are not optimized, then the coil assembly is easier to manufacture, but the magnetic field uniformity is poor leading to increased linewidths
Solution Approach 1:
The patent establishes specific parameter ranges for the coil dimensions (radius R, height H, winding density) that optimize magnetic field uniformity. By defining these parameters within specific ratios and ranges, the design achieves superior field homogeneity while remaining manufacturable. The optimized parameters create a balance between fabrication feasibility and field quality.
Solution Approach 2:
The patent introduces adjustability in the coil construction process. The winding density and layer configuration can be dynamically adjusted during manufacturing to achieve the optimal dimensional ratios. This dynamic approach allows manufacturers to tune the coil properties to achieve the specified field uniformity while accommodating manufacturing variations.
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 precise adjustment of the magic angle, reducing linewidths and maintaining high resolution of NMR resonance lines, thereby improving the separation of chemical species in NMR spectra.
Implementation Method 1
a pair of Helmholtz saddle coils which are arranged symmetrically with respect to a z axis of an xyz coordinate system on a cylindrical plane having a radius of a and centered at the z axis to produce a uniform magnetic field in the direction of an x axis when the axis of spinning of the sample is tilted relative to the z axis
Data Source
AI summary
A specially shaped coil assembly for accurate adjustment of the magic angle is provided to permit accurate adjustment of an angle made between the direction of a static magnetic field and the axis of sample spinning without impairing the resolution of NMR signals. The sample is placed within the external static magnetic field B0. The coil assembly is for use in a solid-state NMR apparatus that performs NMR detection while spinning the sample about an axis tilted at the magic angle relative to the external static magnetic field B0. The coil assembly comprises a pair of arcuate conductor lines and a pair of straight conductor lines. Each of the arcuate lines has a diameter of 2a. Each of the straight lines has a length of 2L. The diameter 2a and the length 2L are so selected as to satisfy the relationship: 1.91≤2L/2a≤2.15.