Improved Configuration of Halbach Magnets with a Homogeneous Magnetic Field for Portable NMR Device

2021 ◽  
Vol 36 (5) ◽  
pp. 548-558
Author(s):  
Yi-Yuan Cheng ◽  
Ming-Yang Su ◽  
Tao Hai ◽  
Ming Hui ◽  
Bao-lei Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Fem Analysis ◽  
Pso Algorithm ◽  
Homogeneous Magnetic Field ◽  
Swarm Optimization ◽  
Halbach Array ◽  
Field Uniformity ◽  
Portable Nmr ◽  
3D Finite Element Method ◽  
The Magnetic Field

Halbach array magnets are widely used in portable nuclear magnetic resonance (NMR) devices that the homogeneity of the magnetic field generated by the array affects the imaging quality. In this paper, we propose some improvements to the construction of the Halbach magnets to enhance magnetic field uniformity. Using a Halbach array model comprising 16 magnets, all the calculations are based on 3D finite element method (FEM) analysis and optimized using the particle swarm optimization (PSO) algorithm. Comparisons of the results are shown to support the observations that the optimized and improved constructions can generate a more homogeneous magnetic field.

scholarly journals A Novel Optimization Method for Halbach Magnet

2021 ◽  
Author(s):  
Wenjuan Jiang ◽  
Junzhou Li ◽  
Didi Sheng
Keyword(s):  
Cross Section ◽  
Permanent Magnets ◽  
Optimization Method ◽  
Magnetic Flux Density ◽  
End Effect ◽  
Halbach Array ◽  
Field Uniformity ◽  
Portable Nmr ◽  
Quality Factor Q ◽  
The Magnetic Field

Abstract Portable nuclear magnetic resonance (NMR) instruments are widely used in many fields. However, the large volume, low uniformity and end effect limits the application of portable NMR instruments. In order to improve the uniformity and compensate the end effect, a Halbach structure with 9-layer permanent magnet is proposed, which is optimized by axially adjusting the magnet height based on the Halbach array principle and Quality factor (Q) is introduced to represent the magnetic field uniformity at both ends of the central cylinder region. Each layer consists of 16 permanent magnets with trapezoidal cross section and the total volume is Φ240 × 141.8 mm. Through simulation, it is found that the final magnetic flux density is 1.09 T and the uniformity is 418 ppm in the central region (Φ20 × 20 mm) of the optimized structure. The proposed structure has the advantages of small size, compactness in structure and homogeneity, which is very suitable for portable NMR systems.

scholarly journals A Novel Optimization Method for Halbach Magnet

2021 ◽  
Author(s):  
Wenjuan Jiang ◽  
Junzhou Li ◽  
Didi Sheng
Keyword(s):  
Cross Section ◽  
Permanent Magnets ◽  
Optimization Method ◽  
Magnetic Flux Density ◽  
End Effect ◽  
Halbach Array ◽  
Field Uniformity ◽  
Portable Nmr ◽  
Quality Factor Q ◽  
The Magnetic Field

Abstract Portable nuclear magnetic resonance (NMR) instruments are widely used in many fields. However, the large volume, low uniformity and end effect limits the application of portable NMR instruments. In order to improve the uniformity and compensate the end effect, a Halbach structure with 9-layer permanent magnet is proposed, which is optimized by axially adjusting the magnet height based on the Halbach array principle and Quality factor (Q) is introduced to represent the magnetic field uniformity at both ends of the central cylinder region. Each layer consists of 16 permanent magnets with trapezoidal cross section and the total volume is Φ240 × 141.8 mm. Through simulation, it is found that the final magnetic flux density is 1.09 T and the uniformity is 418 ppm in the central region (Φ20 × 20 mm) of the optimized structure. The proposed structure has the advantages of small size, compactness in structure and homogeneity, which is very suitable for portable NMR systems.

Simulation and Optimization of a Permanent Magnet for Small-Sized MRI by Genetic Algorithm

2013 ◽  
Vol 341-342 ◽  
pp. 577-580
Author(s):  
Yi Yuan Cheng ◽  
Ling Xia ◽  
Wei He
Keyword(s):  
Magnetic Field ◽  
Permanent Magnet ◽  
Homogeneous Magnetic Field ◽  
Main Magnetic Field ◽  
Resonance Imaging ◽  
Simulation And Optimization ◽  
Field Uniformity ◽  
Main Magnet ◽  
Magnetic Resonance Imaging Mri ◽  
The Magnetic Field

The main magnet produces the main magnetic field in the imaging area as one of the important parts of the magnetic resonance imaging (MRI) system. In a permanent MRI magnet, the widespread end effect causes a non-uniform magnetic field distribution and affects the imaging quality. In this paper, an H-type permanent magnet for small-sized MRI applications was designed; in particular, we added an optimized shimming ring outside the pole piece to improve the magnetic field uniformity. Genetic algorithms are used to solve the complex and nonlinear calculation of the magnetic field. The simulation results show that the magnet optimized by the proposed method generates a homogeneous magnetic field that can be easily implemented in practice.

scholarly journals Finite Element Analysis of Magnetic Field Exciter for Direct Testing of Magnetocaloric Materials’ Properties

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2792
Author(s):  
Wieslaw Lyskawinski ◽  
Wojciech Szelag ◽  
Cezary Jedryczka ◽  
Tomasz Tolinski
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Magnetic Circuit ◽  
Homogeneous Magnetic Field ◽  
Element Analysis ◽  
Mcm Testing ◽  
Testing Region ◽  
Magnetocaloric Materials ◽  
Field Excitation ◽  
The Magnetic Field

The paper presents research on magnetic field exciters dedicated to testing magnetocaloric materials (MCMs) as well as used in the design process of magnetic refrigeration systems. An important element of the proposed test stand is the system of magnetic field excitation. It should provide a homogeneous magnetic field with a controllable value of its intensity in the MCM testing region. Several concepts of a magnetic circuit when designing the field exciters have been proposed and evaluated. In the MCM testing region of the proposed exciters, the magnetic field is controlled by changing the structure of the magnetic circuit. A precise 3D field model of electromagnetic phenomena has been developed in the professional finite element method (FEM) package and used to design and analyze the exciters. The obtained results of the calculations of the magnetic field distribution in the working area were compared with the results of the measurements carried out on the exciter prototype. The conclusions resulting from the conducted research are presented and discussed.

scholarly journals Magnetic Rayleigh–Taylor instability at a contact discontinuity with an oblique magnetic field

2020 ◽  
Vol 634 ◽  
pp. A96
Author(s):  
E. Vickers ◽  
I. Ballai ◽  
R. Erdélyi
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Dispersion Relation ◽  
Contact Discontinuity ◽  
Homogeneous Magnetic Field ◽  
Taylor Instability ◽  
Wide Range ◽  
Rayleigh Taylor Instability ◽  
The Magnetic Field ◽  
Theoretical Results

Aims. We investigate the nature of the magnetic Rayleigh–Taylor instability at a density interface that is permeated by an oblique homogeneous magnetic field in an incompressible limit. Methods. Using the system of linearised ideal incompressible magnetohydrodynamics equations, we derive the dispersion relation for perturbations of the contact discontinuity by imposing the necessary continuity conditions at the interface. The imaginary part of the frequency describes the growth rate of waves due to instability. The growth rate of waves is studied by numerically solving the dispersion relation. Results. The critical wavenumber at which waves become unstable, which is present for a parallel magnetic field, disappears because the magnetic field is inclined. Instead, waves are shown to be unstable for all wavenumbers. Theoretical results are applied to diagnose the structure of the magnetic field in prominence threads. When we apply our theoretical results to observed waves in prominence plumes, we obtain a wide range of field inclination angles, from 0.5° up to 30°. These results highlight the diagnostic possibilities that our study offers.

scholarly journals Optimization study on the magnetic field of superconducting Halbach Array magnet

2017 ◽  
Vol 538 ◽  
pp. 46-51 ◽  
Author(s):  
Boyang Shen ◽  
Jianzhao Geng ◽  
Chao Li ◽  
Xiuchang Zhang ◽  
Lin Fu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Halbach Array ◽  
Optimization Study ◽  
The Magnetic Field

Analysis of Vibration Characteristics of Magnetorheological Elastomer Sandwich Beam under Non-Homogeneous Magnetic Field

2011 ◽  
Vol 101-102 ◽  
pp. 202-206 ◽  
Author(s):  
Guo Liang Hu ◽  
Miao Guo ◽  
Wei Hua Li
Keyword(s):  
Magnetic Field ◽  
Natural Frequency ◽  
Sandwich Beam ◽  
Homogeneous Magnetic Field ◽  
Experimental Results ◽  
Magnetorheological Elastomer ◽  
Test Rig ◽  
Thin Aluminum ◽  
Set Up ◽  
The Magnetic Field

In this study, the MRE was manufactured, and the sandwich beam was also fabricated by treating with MRE between two thin aluminum layers. The experiment test rig was set up to investigate the vibration response of the MRE sandwich beam under non-homogeneous magnetic field. The experimental results show that the MRE sandwich beam had the capabilities of left shifting first natural frequency when the magnetic field was increased in the activated regions. It is also obvious that the first natural frequency of the MRE sandwich beam decreased as the magnetic field that applied on the beam was moved from the clamped end of the beam to the free end of the beam.

scholarly journals DYNAMO EFFECTS IN MAGNETIZED IDEAL PLASMA COSMOLOGIES

2008 ◽  
Vol 23 (11) ◽  
pp. 1697-1710 ◽  
Author(s):  
KOSTAS KLEIDIS ◽  
APOSTOLOS KUIROUKIDIS ◽  
DEMETRIOS PAPADOPOULOS ◽  
LOUKAS VLAHOS
Keyword(s):  
Magnetic Field ◽  
Cosmological Model ◽  
Homogeneous Magnetic Field ◽  
Mhd Equations ◽  
Cosmological Perturbations ◽  
Gravitational Instabilities ◽  
Ideal Magnetohydrodynamic ◽  
The Magnetic Field ◽  
Ideal Plasma ◽  
The Ideal

The excitation of cosmological perturbations in an anisotropic cosmological model and in the presence of a homogeneous magnetic field has been studied, using the ideal magnetohydrodynamic (MHD) equations. In this case, the system of partial differential equations which governs the evolution of the magnetized cosmological perturbations can be solved analytically. Our results verify that fast-magnetosonic modes propagating normal to the magnetic field, are excited. But, what is most important, is that, at late times, the magnetic-induction contrast(δB/B) grows, resulting in the enhancement of the ambient magnetic field. This process can be particularly favored by condensations, formed within the plasma fluid due to gravitational instabilities.

Sign in / Sign up

Export Citation Format

Share Document