Related Experiment Video
Updated: Sep 26, 2025
11:42
A Paired Bead and Magnet Array for Molding Microwells with Variable Concave Geometries
Published on: January 28, 2018
8.8K
A passive shimming method for Halbach magnet based on magnetic sheet arrays
Ya Wang1, Yajie Xu2, Feng Wang3
1School of Biomedical Engineering (Suzhou), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230026, China; Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163, Jiangsu, China.
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|April 21, 2022
Summary
We developed a new passive shimming (PS) method using magnetic sheet arrays (MSAs) to improve the field homogeneity of Halbach magnets for nuclear magnetic resonance (NMR) devices. This technique significantly enhances magnetic field uniformity, crucial for precise NMR measurements.
Area of Science:
- Physics
- Materials Science
- Magnetic Resonance Imaging
Background:
- Halbach magnets offer high potential for nuclear magnetic resonance (NMR) devices.
- Achieving high field homogeneity is critical for NMR applications, demanding efficient passive shimming (PS) techniques.
- Conventional PS methods are often iterative and time-consuming, involving complex optimization of magnetic component placement.
Purpose of the Study:
- To introduce a novel passive shimming (PS) method utilizing magnetic sheet arrays (MSAs).
- To achieve precise field compensation for Halbach magnets up to the 3rd order spherical harmonic basis.
- To provide a flexible and convenient shimming solution for compact Halbach magnet systems.
Main Methods:
- Implementation of a passive shimming (PS) method based on magnetic sheet arrays (MSAs).
- Targeting spherical harmonic basis up to the 3rd order, including specific cross terms for structural field compensation.
- Utilizing arrays of magnetic sheets for shimming Halbach magnets.
Main Results:
- Improved field homogeneity in a 0.5 T Halbach magnet from 811 ppm to 4.7 ppm (L15 mm × R2.5 mm sample).
- Demonstrated rough shimming in a 0.93 T Halbach magnet, enhancing homogeneity from 1103 ppm to 125 ppm (R2.5 mm sphere).
- The MSA-based PS method proved effective in significantly increasing magnetic field uniformity.
Conclusions:
- The proposed magnetic sheet array (MSA) based passive shimming (PS) method offers a flexible and convenient approach for Halbach magnets.
- This technique effectively compensates for field inhomogeneity, meeting the demanding requirements of NMR devices.
- The method is applicable to compact Halbach magnets used in NMR spectrometers and other high-homogeneity applications.
Related Concept Videos
01:17Magnetic Damping
586
Eddy currents can produce significant drag on motion, called magnetic damping. For instance, when a metallic pendulum bob swings between the poles of a strong magnet, significant drag acts on the bob as it enters and leaves the field, quickly damping the motion.
If, however, the bob is a slotted metal plate, the magnet produces a much smaller effect. When a slotted metal plate enters the field, an emf is induced by the change in flux; however, it is less effective because the slots limit the...
If, however, the bob is a slotted metal plate, the magnet produces a much smaller effect. When a slotted metal plate enters the field, an emf is induced by the change in flux; however, it is less effective because the slots limit the...
586
01:24Potential Due to a Magnetized Object
365
Magnetic dipoles in magnetic materials are aligned when placed under an external magnetic field. For paramagnets and ferromagnets, dipole alignment occurs in the direction of the magnetic field. However, the dipoles align opposite to the field in the case of diamagnets. This state of magnetic polarization due to the external field is called magnetization. Magnetization is defined as the dipole moment per unit volume. It plays a similar role to polarization in electrostatics.
The vector...
The vector...
365
01:18Magnetic Field Due to Two Straight Wires
3.0K
Consider two parallel straight wires carrying a current of 10 A and 20 A in the same direction and separated by a distance of 20 cm. Calculate the magnetic field at a point "P2", midway between the wires. Also, evaluate the magnetic field when the direction of the current is reversed in the second wire.
3.0K
01:30The Hall Effect
2.8K
Edwin H. Hall, in the year 1879, devised an experiment that could be used to identify the polarity of the predominant charge carriers in a conducting material. From a historical perspective, this experiment was the first to demonstrate that the charge carriers in most metals are negative.
2.8K
01:26Diamagnetism
2.5K
Materials consisting of paired electrons have zero net magnetic moments. However, when these materials are placed under an external magnetic field, the moments opposite to the field are induced. Such materials are called diamagnets. Diamagnetism is the response of the diamagnets when placed in an external magnetic field.
Diamagnetism was discovered by Anton Brugmans in 1778 when he observed that bismuth gets repelled by magnetic fields, thus theorizing that diamagnets get repelled by magnets....
Diamagnetism was discovered by Anton Brugmans in 1778 when he observed that bismuth gets repelled by magnetic fields, thus theorizing that diamagnets get repelled by magnets....
2.5K
01:15Lenz's Law
4.4K
The direction in which the induced emf drives the current around a wire loop can be found through the negative sign. However, it is usually easier to determine this direction with Lenz's law, named in honor of its discoverer, Heinrich Lenz (1804–1865). Lenz's law states that the direction of the induced emf drives the current around a wire loop always to oppose the change in magnetic flux that causes the emf.
If a bar magnet is moved toward a coil such that the magnetic flux...
If a bar magnet is moved toward a coil such that the magnetic flux...
4.4K