Cylindrical Gradient Coil Passive RF Shield Segmentation
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Solution Overview
Problem
Existing actively shielded gradient coil systems in NMR spectrometers face challenges in maximizing the RF region volume without compromising the performance of the gradient coil system, often resulting in reduced efficiency and sensitivity due to the need for RF shielding, which can impair the Q-factor and magnetic field amplitude.
Innovation Solution
The implementation of a passive RF shield with specific radii and dimensions allows for a central conductor-free region, enabling a larger RF volume while maintaining gradient coil performance by using a cylindrical section with a maximum outer radius larger than the minimum inner radius of the main gradient coil and incorporating a passive RF shield with interconnected partial sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a passive RF shield is added to the gradient coil system, then electromagnetic coupling and background signals are minimized, but the RF region volume is reduced and the Q-factor is impaired
Solution Approach 1:
The passive RF shield is divided into multiple electrically interconnected partial sections arranged at different radii. This segmentation allows the RF shield to cover a larger volume while maintaining shielding effectiveness, as each partial section contributes to the overall shielding without requiring a complete solid barrier that would excessively reduce the RF region volume.
Solution Approach 2:
The RF shield is designed with varying radial positions for different partial sections, creating local variations in shielding density. This allows optimal shielding in regions where electromagnetic coupling is most problematic while preserving RF region volume in areas where shielding is less critical, thus balancing shielding effectiveness with volume preservation.
2Object-affected harmful factors
If the RF shield is positioned closer to the gradient coils to maximize shielding, then electromagnetic interference is reduced, but the available volume for transmit and receive coils is reduced
Solution Approach 1:
Instead of positioning the RF shield at a single radial distance, the invention uses multiple partial sections at different radii, effectively adding a radial dimension to the shielding arrangement. This allows the shield to provide effective electromagnetic interference reduction while leaving sufficient radial space for the transmit and receive coils to operate with adequate volume.
3Productivity
If the gradient coil system uses larger radii to improve gradient efficiency, then gradient performance is enhanced, but the space available for RF shielding is reduced
Solution Approach 1:
The RF shield is segmented into partial sections that can be positioned at different radii, allowing the shielding structure to adapt to larger gradient coil radii while still providing adequate shielding volume. The segmented design enables the shield to extend outward from the gradient coils without requiring a solid barrier that would excessively encroach on the RF region.
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 design enhances the performance of the transmit and/or receive coil system by allowing higher pulse angles with low pulse powers, reducing thermal effects, and improving the signal-to-noise ratio, while minimizing electromagnetic coupling and background signals.
Implementation Method 1
a passive RF shield is provided that is constructed from at least three electrically interconnected partial sections
Implementation Method 2
when current flows in one of the measurement volumes through which the z-axis passes, the gradient coil system generates a Z-gradient field
Implementation Method 3
an electromagnet for generating a strong, static magnetic field
Implementation Method 4
a measurement sample, and a gradient coil system for generating pulsed field gradients. Moreover, the NMR spectrometer comprises the necessary apparatus for generating and detecting electrical signals, which are generated and/or detected in the aforementioned components
Data Source
AI summary
A gradient coil system has a cylindrical section in a central region, which contains no conductor elements and has a maximum outer radius that is larger than a minimum inner radius of conductor elements of a main gradient coil. An outer radius of this cylindrical section is only insubstantially smaller or equal in size to a minimum inner radius of a shielding coil in this axial range. The free space in the center of the gradient coil system is used to insert a passive RF shield, whose radius in a central region becomes larger over a certain length than its radius in outer regions. The RF shield is constructed from at least three partial sections, which are electrically interconnected. The actively shielded gradient coil system maximizes the volume of the RF region without loss of gradient coil system performance.