Superconducting RF Coil Assembly for NMR Spectrometer
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Solution Overview
Problem
High-sensitivity nuclear magnetic resonance (NMR) spectrometers face challenges in achieving high filling factors and magnetic field homogeneity due to the strong magnetic shielding effects of superconducting detection coils, which reduce sensitivity and resolution.
Innovation Solution
A method involving a type II superconducting detection coil with pinning centers, where the external magnetic field is initially strengthened, then cooled below its critical temperature, and gradually reduced to minimize magnetization, allowing for zero total magnetization and enhanced sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a superconducting detection coil is used to enhance sensitivity, then thermal noise is reduced and Q value is enhanced, but magnetic field homogeneity deteriorates due to strong magnetic shielding effects
Solution Approach 1:
The patent applies preliminary action by performing field cooling (cooling the superconducting coil in the presence of the external magnetic field) before NMR measurement. This preliminary cooling process establishes flux pinning centers that lock the magnetic field lines, preventing distortion during subsequent measurements and maintaining magnetic field homogeneity while preserving the superconducting state's noise-reduction benefits.
Solution Approach 2:
The patent changes the temperature parameter by cooling the detection coil below its critical temperature to achieve superconductivity. This parameter change reduces thermal noise and enhances Q value while the combination of field cooling and flux pinning maintains magnetic field homogeneity, thus resolving the contradiction between sensitivity enhancement and field homogeneity preservation.
2Measurement precision
If a superconducting detection coil is used to reduce thermal noise, then the filling factor increases, but magnetic field distortion increases due to coil magnetization
Solution Approach 1:
The patent applies preliminary action by performing field cooling before measurement. This preliminary cooling in the presence of the external magnetic field establishes flux pinning that prevents magnetization-induced field distortion during measurement, while maintaining the superconducting state for noise reduction and high filling factor.
Solution Approach 2:
The patent converts the potentially harmful magnetization effect into a beneficial flux pinning mechanism. By cooling the superconducting coil in the external magnetic field, the magnetic flux lines become pinned in the type II superconductor, transforming what would be harmful magnetization-induced distortion into a stabilizing effect that maintains field homogeneity.
3Temperature
If the detection coil is cooled below critical temperature to achieve superconductivity, then thermal noise is reduced, but magnetic field homogeneity is compromised by magnetization effects
Solution Approach 1:
The patent applies preliminary action by performing field cooling before measurement. This preliminary cooling in the presence of the external magnetic field establishes flux pinning that prevents magnetization-induced field distortion during measurement, while maintaining the superconducting state's noise-reduction benefits.
Solution Approach 2:
The patent uses type II superconducting materials with flux pinning centers, which are composite structures that combine superconducting regions with pinning centers. This composite material structure allows the coil to maintain superconductivity for noise reduction while the pinning centers prevent magnetic field distortion, resolving the contradiction between temperature reduction and 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
This approach achieves high sensitivity and resolution by minimizing magnetization and maintaining the superconducting state, thereby increasing the filling factor and reducing thermal noise.
Implementation Method 1
A method involving a type II superconducting detection coil with pinning centers, where the external magnetic field is initially strengthened, then cooled below its critical temperature, and gradually reduced to minimize magnetization, allowing for zero total magnetization
Implementation Method 2
a cryogenic cooling system for cryogenically cooling the detection coil, enhancing the Q value of the coil, and reducing thermal noise
Implementation Method 3
reducing thermal noise
Implementation Method 4
a detection coil made of a superconducting material, incorporated in the NMR probe, and detecting an NMR signal emanating from the magnetically excited nuclei under investigation
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
An NMR spectrometer is offered which can have a high filling factor if an NMR detection coil using a superconducting material is employed. Also, a method of setting up this spectrometer is offered. For these purposes, the following three steps are performed. (1) An external magnetic field is set to H0 + ΔH (where ΔH > 0). When the detection coil made of the superconducting material is still in a normal state, a magnetic field stronger than the ultimate target static magnetic field strength H0 by ΔH is applied to the detection coil. (2) The detection coil made of the superconducting material is cooled down to To lower than its critical temperature Tc to bring the coil into a superconducting state while the external magnetic field H0 + ΔH is applied to the detection coil. (3) The external magnetic field is lowered from H0 + ΔH to H0 such that the applied external magnetic field is decreased by ΔH while the detection coil is kept in the superconducting state.