DOCSLIB.ORG

Influence of the Distribution of the Properties of Permanent

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Influence of the Distribution of the Properties of Permanent 1 Influence of the distribution of the properties of permanent magnets on the field homogeneity of magnet assemblies for mobile NMR Y.P.Klein1∗, L.Abelmann1;2, and J.G.E.Gardeniers 1∗ 1 University of Twente, Enschede, The Netherlands 2 KIST Europe, Saarbrucken,¨ Germany Abstract—We optimised the magnetic field homogeneity of two In the literature, several magnet shapes for mobile NMR canonical designs for mobile microfluidic NMR applications: two sensors have been reported. A broad overview of magnet parallel magnets with an air gap and a modified Halbach array. developments up to 2009 can be found in Demas et al. [10]. Along with the influence of the sample length, general design guidelines will be presented. For a fair comparison the sensitive U-shaped single-sided magnets [11], [12] and magnets with length of the sample has been chosen to be the same as the specially shaped iron pole magnets [13] have been used to gap size between the magnets to ensure enough space for the explore surfaces. Mobile pseudo-Halbach configurations [14] transmitting and receiving unit, as well as basic electric shimming and two cylindrical magnets [15] have been applied for solid components. Keeping the compactness of the final device in mind, and liquid NMR measurements. While the pseudo-Halbach a box with an edge length 5 times the gap size has been defined, in which the complete magnet configuration should fit. With the generates a higher field, ranging from 0:7 to 2:0 T [16]–[18] chosen boundary conditions, the simple parallel cuboid config- compared to 0:35 to 0:6 T for the other configurations [5], uration reaches the best homogeneity without active shimming [11]–[13], the reported field homogeneities without electric (0.5Bs, 41 ppm), while the Pseudo-Halbach configuration has shimming seem to be independent of the design, ranging from the highest field strength (0.9Bs, 994 ppm), assuming perfect 20 ppm to 606 ppm [1], [5], [15], [18]–[20]. Comparing the magnets. However, permanent magnet configurations suffer from imperfections, such as magnetisation, fabrication and positioning two most reported mobile liquid NMR sensors, it further stands errors, which results in worse magnetic field homogeneities than out that there is no obvious relation between the size of the expected from simulations using a fixed optimised parameter sensor and the choice of the magnet configuration. set. We present a sensitivity analysis for a magnetic cube and the To achieve more insight into possible guidelines for the results of studies of the variations in the magnetisation and angle magnet design, in this paper a modelling study will be of magnetisation of magnets purchased from different suppliers, composed of different materials and coatings, and of different presented from which the homogeneity and field strength at sizes. We performed a detailed Monte Carlo simulation on the specific locations in the gap of the magnet configuration is effect of the measured distribution of magnetic properties on derived numerically. It is widely experienced that after build- the mentioned configurations. The cuboid design shows a mean ing such a permanent magnet configuration, the homogeneity homogeneity of 430 ppm (std dev. 350 ppm), the Pseudo-Halbach reached in practice does not exhibit the same results as in has a mean homogeneity of 1086 ppm (std dev. 8 ppm). the simulation [16], [18], [21]–[23], which can be caused Keywords—mobile NMR, magnet imperfections, permanent by several factors. The magnetisation of permanent magnets magnets, Halbach, field homogeneity, proof-reading-service depends highly on the temperature, as well as on the remanent magnetisation [24]. This remanent magnetisation can change over time due to shock-induced demagnetisation [25], [26], I. INTRODUCTION external magnetic fields [27], a degrading of the magnetic Low-field and low-cost mobile microfluidic nuclear mag- material caused by oxidation [28], as well as broken or netic resonance (NMR) sensors are very suitable for appli- chipped off pieces (since magnets are very brittle) [21]. Next arXiv:2103.13691v1 [physics.app-ph] 25 Mar 2021 cations in chemical process industry and in research, for to material related differences, fabrication inaccuracies such as example chemical analysis, biomedical applications, and flow variations in the dimensions and magnetisation angles affect measurements [1]–[9]. The design of a permanent magnet for the field created by a permanent magnet. On top of that, an NMR sensor requires both a strong magnetic field and a magnet configurations can never be assembled perfectly. Errors high field homogeneity within a defined region of interest. In in placement may induce a tilt or an axial offset of the magnet. NMR, a high external magnetic field results in a high spectral We carried out an extensive numerical sensitivity analysis resolution and detection sensitivity. of a single cubic magnet using these variations. We measured However, field inhomogeneities compromise the spectral the variations in the magnetisation and magnetisation angle resolution. Our aim with this research was to determine how of magnets composed of different materials, with different the distribution of the properties of permanent magnets affect coatings, and with different sizes, obtained from different man- the magnetic field homogeneity of magnet configurations for ufacturers. The two main magnet configurations investigated mobile NMR devices. are a system of two parallel magnets and a Pseudo-Halbach 2 0.5005 0.5004 s /B 0.5003 z B d 0.5002 0.5001 Fig. 1. Magnet configurations for microfluidic NMR. The sample under -0.5 -0.25 0 0.25 0.5 investigation is inside a tubular channel running through the center of the Distance/Gap size (x/d ) configurations, and has a length s. The arrows indicate the magnetisation of each individual magnet. Left: Cuboid configuration. The height of the stack l is fixed at five times the gap between the magnets d. The width w of the Fig. 2. Field profile of the cuboid configuration as a function of the relative stack is optimised for minimum field inhomogeneity over the sample length distance from the centre between the magnets. In the optimised situation for s. Right: Pseudo-Halbach configuration. Again l is fixed to 5d, but now the a sample length equal to the gap size, the field in the centre equals the field magnet recess c is optimised. at the edges (x = ±0:5d). configuration [10], shown in Fig.1. One configuration of each been purchased. We chose different materials, coatings, sizes type has been designed and optimised for the following bound- and manufacturers, shown in TableI. ary conditions. The sensitive length of the channel (s) has been chosen to be the same as the gap size (d). For example: In B. Stray field calculation case a maximal magnet size of 50 mm × 50 mm × 50 mm is Calculations of the magnetic stray fields were performed required, the gap size turns out to be 10 mm. All dimension using CADES simulation software, described by Delinchant specifications are scalable and will be normalised by the gap et al. [32]. The magnetic interactions are modelled with length. Scaling the dimensions bigger or smaller will result the MacMMems tool, which uses the Coulombian equivalent in an increased or decreased sample length relative to the charge method to generate a semi-analytic model. dimensions of the gap, while the magnetic field properties within the region of interest will stay the same. The magnetic ZZ 0 field has been normalised to the residual magnetic flux density s(r − r ) B(r) = 0 3 ds, s = m0M · n Bs (T) of the used magnetic material. The cuboid configuration jr − r j consists of two cuboid magnets with a height of 2d and a Here, B is the magnetic field (T) and M the magnetisation of width of 4:72d. The Pseudo-Halbach configuration consists of the permanent magnet (A=m), r and r0 define the observation eight bar magnets, each with the dimensions d × d × 5d. The point and its distance to the elementary field source area ds. measured variations in the magnets have been used to perform The integral is taken over the surface of the magnets. s (T) a Monte Carlo simulation to provide insight into how the is the magnetic surface charge, and n the unit vector normal homogeneity of those configurations varies after assembling. to the surface. The results have been verified with field measurements done The CADES framework, including a component generator, with a Tesla meter. The sample channel in most published component calculator, and component optimiser, generated the microfluidic NMR sensors has a high ratio of sample length final equations, which are used to calculate and optimise the over inner diameter (s=di) (5:0 over 0:4 mm in [29], 30 over designs. 1:0 mm in [30], and 2:9 over 0:15 mm in [31]). Therefore we focus on a high field homogeneity in mainly one dimension C. Design optimisation procedure (x-axis). The stray field calculations are used to optimize particular II. METHODS magnet configurations with respect to the inhomogeneity of the magnetic field over the length of the sample. This inho- A. Determination of variation in magnet properties mogeniety is captured in a single valued metric defined as the The variations in the properties of the magnets have root mean square of the difference between the z-component been measured with a 3D Hall-probe (THM1176 Three-axis of the mean field Bmean and the z-component of field along Hall Magnetometer, Metrolab). The setup for the configu- the sample Bz, averaged of the sample length s and related to ration measurements contains a stable temperature environ- the mean field: ment (38:0(5) °C) and a Hall sensor from Projekt Elektronik GmbH (Teslameter 3002/Transverse Probe T3-1,4-5,0-70) in Z s=2 q 1 2 combination with a motorised linear stage.
Load more

Recommended publications
  • Arxiv:1811.03898V1 [Physics.Ins-Det] 9 Nov 2018
    Variable single-axis magnetic-field generator using permanent magnets Oleg Tretiak,1 Peter Bl¨umler,1 and Lykourgos Bougas1, a) Institut f¨urPhysik, Johannes Gutenberg Universit¨at-Mainz,55128 Mainz, Germany (Dated: 12 November 2018) We present a design for producing precisely adjustable and alternating single-axis magnetic fields based on nested Halbach dipole pairs consisting of permanent magnets only. Our design allows for three dimensional optical and mechanical access to a region with strong adjustable dipolar fields, is compatible with systems operating under vacuum, and does not effectively dissipate heat under normal operational conditions. We present a theoretical analysis of the properties and capabilities of our design, and construct a proof-of-concept prototype. Using our prototype, we demonstrate fields of up to several kilogauss with field homogeneities of better than 5%, which are harmonically modulated at frequencies of ∼1 Hz with a power consumption of approximately 1 W. Moreover, we discuss how our design can be modified to generate adjustable quadrupolar magnetic fields with gradients as large as 9.5 T/m in a region of optical and mechanical access. Our design is scalable and can be constructed to be suitable for table-top experiments, as in the case of polarimetric and magnetometric setups that require strong alternating magnetic fields, but also for large scale applications such as generators. Special arrangements of magnetic structures that in- crease the magnetic flux on one side of the arrangement while reducing, or even cancelling, it on the opposite side, were first theoretically proposed by Mallinson 1, but later realized by K.
    [Show full text]
  • Three-Dimensional Field Solutions for Multi-Pole Cylindrical Halbach Arrays in an Axial Orientation
    NASA/TM—2006-214359 Three-Dimensional Field Solutions for Multi-Pole Cylindrical Halbach Arrays in an Axial Orientation William K. Thompson Glenn Research Center, Cleveland, Ohio September 2006 NASA STI Program . in Profile Since its founding, NASA has been dedicated to the • CONFERENCE PUBLICATION. Collected advancement of aeronautics and space science. The papers from scientific and technical NASA Scientific and Technical Information (STI) conferences, symposia, seminars, or other program plays a key part in helping NASA maintain meetings sponsored or cosponsored by NASA. this important role. • SPECIAL PUBLICATION. Scientific, The NASA STI Program operates under the auspices technical, or historical information from of the Agency Chief Information Officer. It collects, NASA programs, projects, and missions, often organizes, provides for archiving, and disseminates concerned with subjects having substantial NASA’s STI. The NASA STI program provides access public interest. to the NASA Aeronautics and Space Database and its public interface, the NASA Technical Reports Server, • TECHNICAL TRANSLATION. English- thus providing one of the largest collections of language translations of foreign scientific and aeronautical and space science STI in the world. technical material pertinent to NASA’s mission. Results are published in both non-NASA channels and by NASA in the NASA STI Report Series, which Specialized services also include creating custom includes the following report types: thesauri, building customized databases, organizing and publishing research results. • TECHNICAL PUBLICATION. Reports of completed research or a major significant phase For more information about the NASA STI of research that present the results of NASA program, see the following: programs and include extensive data or theoretical analysis.
    [Show full text]
  • Development and Testing of an Axial Halbach Magnetic Bearing
    NASA/TM—2006-214357 Development and Testing of an Axial Halbach Magnetic Bearing Dennis J. Eichenberg, Christopher A. Gallo, and William K. Thompson Glenn Research Center, Cleveland, Ohio July 2006 NASA STI Program . in Profile Since its founding, NASA has been dedicated to the • CONFERENCE PUBLICATION. Collected advancement of aeronautics and space science. The papers from scientific and technical NASA Scientific and Technical Information (STI) conferences, symposia, seminars, or other program plays a key part in helping NASA maintain meetings sponsored or cosponsored by NASA. this important role. • SPECIAL PUBLICATION. Scientific, The NASA STI Program operates under the auspices technical, or historical information from of the Agency Chief Information Officer. It collects, NASA programs, projects, and missions, often organizes, provides for archiving, and disseminates concerned with subjects having substantial NASA’s STI. The NASA STI program provides access public interest. to the NASA Aeronautics and Space Database and its public interface, the NASA Technical Reports Server, • TECHNICAL TRANSLATION. English- thus providing one of the largest collections of language translations of foreign scientific and aeronautical and space science STI in the world. technical material pertinent to NASA’s mission. Results are published in both non-NASA channels and by NASA in the NASA STI Report Series, which Specialized services also include creating custom includes the following report types: thesauri, building customized databases, organizing and publishing research results. • TECHNICAL PUBLICATION. Reports of completed research or a major significant phase For more information about the NASA STI of research that present the results of NASA program, see the following: programs and include extensive data or theoretical analysis.
    [Show full text]
  • An Adjustable Linear Halbach Array J.E
    Author’s Accepted Manuscript An adjustable linear Halbach array J.E. Hilton, S.M. McMurry PII: S0304-8853(12)00100-X DOI: doi:10.1016/j.jmmm.2012.02.014 Reference: MAGMA57359 To appear in: Journal of Magnetism and Magnetic Materials www.elsevier.com/locate/jmmm Received date: 16 November 2011 Revised date: 25 January 2012 Cite this article as: J.E. Hilton and S.M. McMurry, An adjustable linear Halbach array, Journal of Magnetism and Magnetic Materials, doi:10.1016/j.jmmm.2012.02.014 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. An adjustable linear Halbach array J. E. Hiltona,∗, S. M. McMurryb aCSIRO Mathematics, Informatics and Statistics, Clayton South, VIC 3169, Australia bSchool of Physics, Trinity College Dublin, Ireland Abstract The linear Halbach array is a well known planar magnetic structure ca- pable, in the idealized case, of generating a one-sided magnetic field. We show that such a field can be created from an array of uniformly magnetized rods, and rotating these rods in an alternating fashion can smoothly transfer the resultant magnetic field through the plane of the device. We examine an idealized model composed of infinite line dipoles and carry out computa- tional simulations on a realizable device using a magnetic boundary element method.
    [Show full text]
  • Table-Top NMR System for High-Pressure Studies with In-Situ Laser Heating
    Table-top NMR system for high-pressure studies with in-situ laser heating Thomas Meier,1, ∗ Anand Prashant Dwivedi,1, 2 Saiana Khandarkhaeva,1 Timofey Fedotenko,3 Natalia Dubrovinskaia,3 and Leonid Dubrovinsky1 1Bavarian Geoinstitute, University of Bayreuth, D-95447 Bayreuth, Germany 2University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA 3Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography, University of Bayreuth, D-95447 Bayreuth, Germany (Dated: September 23, 2019) High pressure Nuclear Magnetic Resonance (NMR) is known to uncover behavior of matter at extreme conditions. However, significant maintenance demands, space requirements and high costs of superconducting magnets render its application unfeasible for regular modern high pressure lab- oratories. Here, we present a table-top NMR system based on permanent Halbach magnet arrays with dimensions of 25 cm diameter and 4 cm height. At the highest field of 1013 mT, 1H-NMR spectra of Ice VII have been recorded at 25 GPa and ambient temperature. The table-top NMR system can be used together with double sided laser heating set-ups. Feasibility of high-pressure 1 high-temperature NMR was demonstrated by collecting H-NMR spectra of H2O at 25 GPa and 1063(50) K. We found that the change in signal intensity in laser-heated NMR diamond anvil cell yields a convenient way for temperature measurements. I. INTRODUCTION Whereas the first point restricts an application of NMR at high temperatures in DACs to mostly hydrogen nuclei, Recent developments of Diamond Anvil Cell (DAC) the latter is merely rooted in technical considerations. based NMR using two-dimensional magnetic flux tailor- Over the course of the last years, novel magnet designs ing Lenz lens resonator structures [1] pushed the field led to the development of table-top NMR set-ups[8{11].
    [Show full text]
  • Halbach Arrays at the Nanoscale from Chiral Spin Textures
    Halbach arrays at the nanoscale from chiral spin textures Miguel A. Marioni,∗ Marcos Penedo, Mirko Ba´cani,Johannes Schwenk,y and Hans J. Hugz Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 D¨ubendorf, Switzerland. (Dated: August 22, 2017) Abstract Mallinson's idea[1] that some spin textures in planar magnetic structures could produce an en- hancement of the magnetic flux on one side of the plane at the expense of the other gave rise to permanent magnet configurations known as Halbach[2] magnet arrays. Applications range from wiggler magnets in particle accelerators and free electron lasers[3], to motors[4], to magnetic levi- tation trains[5], but exploiting Halbach arrays in micro- or nanoscale spintronics devices requires solving the problem of fabrication and field metrology below 100 µm size[6]. In this work we show that a Halbach configuration of moments can be obtained over areas as small as 1 × 1 µm2 in sput- tered thin films with N´eel-type domain walls of unique domain wall chirality, and we measure their stray field at a controlled probe-sample distance of 12:0 ± 0:5 nm. Because here chirality is deter- mined by the interfacial Dyzaloshinkii-Moriya interaction[7] the field attenuation and amplification is an intrinsic property of this film, allowing for flexibility of design based on an appropriate defi- nition of magnetic domains. 100 nm-wide skyrmions illustrate the smallest kind of such structures, for which our measurement of stray magnetic fields and mapping of the spin structure shows they funnel the field toward one specific side of the film given by the sign of the Dyzaloshinkii-Moriya interaction parameter D.
    [Show full text]
  • Low Field MRI Using Halbach Ferromagnet Arrays
    Low Field MRI using Halbach Ferromagnet Arrays THESIS submitted in partial fulfillment of the requirements for the degree of BACHELOR OF SCIENCE in PHYSICS Author : K. van Deelen Student ID : s1282220 Supervisor : A.G. Webb 2nd corrector : T.H. Oosterkamp Leiden, The Netherlands, July 20, 2017 Low Field MRI using Halbach Ferromagnet Arrays K. van Deelen Huygens-Kamerlingh Onnes Laboratory, Leiden University P.O. Box 9500, 2300 RA Leiden, The Netherlands July 20, 2017 Abstract Since its discovery MRI quickly became an essential medical tool to help doctors make prognoses, as it allows one to look inside the body without using invasive techniques like CAT-scans or surgery. However, MRI’s are very expensive: around one million US dollars per Tesla of magnetic field, and require advanced facilities in order to operate (e.g. liquid helium), and thus are not accessible all over the world. This research explores developing a simpler and less expensive MRI, using ferromagnets in a Halbach array, producing a low magnetic field, with high enough homogeneity to still be able to make sharp enough images in order to make a prognoses on patients, e.g. Hydrocephalus in a child’s head. Several models are proposed and evaluated on field strength, homogeneity, weight, size and cost. Chapter 1 Introduction Ever since its discovery in 1971 by Paul C. Lauterbur [1], Magnetic Reso- nance Imaging (MRI) quickly became an essential tool in modern hospitals in the western world. With it, doctors can make prognoses without using invasive techniques, like CAT-scans or surgery, while still being able to make sharp images due to the high contrast in soft and hard tissue.
    [Show full text]
  • High Homogeneity Permanent Magnet for Diamond Magnetometry
    High homogeneity permanent magnet for diamond magnetometry Arne Wickenbrock,1, 2 Huijie Zheng,1, 2 Georgios Chatzidrosos,1, 2 Joseph Shaji Rebeirro,1, 2 Tim Schneemann,1, 2 and Peter Blmler2 1Helmholtz-Institut, GSI Helmholtzzentrum f¨ur Schwerionenforschung, 55128 Mainz, Germany 2Johannes Gutenberg-Universit¨atMainz, 55128 Mainz, Germany (Dated: August 18, 2020) Halbach magnets are a source of homogeneous magnetic field in an enclosed volume while keeping stray fields at a minimum. Here, we present the design, construction, and characterization for a 10 cm inner diameter double Halbach ring providing a homogeneous (< 100 ppm over 1:0 × 1:0 × 0:5 cm3) magnetic field of around 105 mT, which will be used for a diamond based microwave-free widefield imaging setup. The final characterization is performed with a novel fiberized diamond-based sensor on a 3D translation stage documenting the high homogeneity of the constructed Halbach array and its suitability for the proposed use. Keywords: Halbach, dipole, Mandhala, magnetic resonance, NMR, MRI, NV-center, GSLAC, wide-field, microwave-free I. INTRODUCTION the proposed experiment can be seen in Figure 1. A large area diamond containing NV centers is placed in a back- ground field of 102.4 mT. A camera can then be used to Cylindrical Halbach magnets [1] have become a stan- directly read-off magnetic field variation originating from dard design for nuclear magnetic resonance (NMR) at samples placed on the top of the diamond surface. De- field strength typically below 2 tesla [2]. Depending on ploying the protocols developed in [6] would allow full 3D the ratio of inner and outer diameter, they can gener- vector magnetic field images.
    [Show full text]
  • Simulation of a Synchronous Planar Magnetically Levitated Motion System Based on a Real-Time Analytical Force Model
    energies Article Simulation of a Synchronous Planar Magnetically Levitated Motion System Based on a Real-Time Analytical Force Model Ruotong Peng, Tong Zheng , Xing Lu, Xianze Xu * and Fengqiu Xu * Electronic Information School, Wuhan University, Wuhan 430072, China; [email protected] (R.P.); [email protected] (T.Z.); [email protected] (X.L.) * Correspondence: [email protected] (X.X.); [email protected] (F.X.) Received: 21 October 2020; Accepted: 25 November 2020; Published: 2 December 2020 Abstract: The existing simulation method for the control of linear or planar magnetically levitated actuators always ignores the characteristics of the real physical object, which deteriorates the accuracy of the simulation. In this work, the proposed emulator for the magnetically levitated actuator is developed to consider both the force characteristics and the control algorithm. To model the real controlled object, the mathematical model for 1D (one-dimensional) and 2D (two-dimensional) magnetic arrays is derived where the yaw angle is taken into consideration using the coordinate transformation. The solution of the mathematical model is compared with the commercial BEM (boundary element method) software and the measurements from a force and torque testing setup to highlight the accuracy of the proposed mathematical model. Compared with the traditional simulation method of the motion control systems founded on the simplified system transfer function, the proposed simulation method has higher consistency and is closer to reality. The accuracy and efficiency of the proposed magnetic force model are further verified by the emulator based on the numerical force model and the testing data of the real setup.
    [Show full text]
  • Inverted Linear Halbach Array for Separation of Magnetic Nanoparticles Yumi Ijiri Oberlin College, [email protected]
    Oberlin Digital Commons at Oberlin Faculty & Staff choS larship 7-1-2013 Inverted Linear Halbach Array for Separation of Magnetic Nanoparticles Yumi Ijiri Oberlin College, [email protected] Chetan Poudel P. Stephen Williams Lee R. Moore Toru Orita See next page for additional authors Follow this and additional works at: https://digitalcommons.oberlin.edu/faculty_schol Repository Citation Yumi Ijiri, Chetan Poudel, P. Stephen Williams, Lee R. Moore, Toru Orita, and Maciej Zborowski. 2013. "Inverted Linear Halbach Array for Separation of Magnetic Nanoparticles." IEEE Transactions on Magnetics 49(7): 3449-3452. This Article is brought to you for free and open access by Digital Commons at Oberlin. It has been accepted for inclusion in Faculty & Staff choS larship by an authorized administrator of Digital Commons at Oberlin. For more information, please contact [email protected]. Authors Yumi Ijiri, Chetan Poudel, P. Stephen Williams, Lee R. Moore, Toru Orita, and Maciej Zborowski This article is available at Digital Commons at Oberlin: https://digitalcommons.oberlin.edu/faculty_schol/2612 IEEE TRANSACTIONS ON MAGNETICS, VOL. 49, NO. 7, JULY 2013 3449 Inverted Linear Halbach Array for Separation of Magnetic Nanoparticles Yumi Ijiri , Chetan Poudel , P. Stephen Williams ,LeeR.Moore, Toru Orita , and Maciej Zborowski Department of Physics and Astronomy, Oberlin College, Oberlin, OH 44074 USA Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195 USA Cambrian Technologies, Inc., Cleveland, OH 44109 USA A linear array of Nd-Fe-B magnets has been designed and constructed in an inverted Halbach configuration for use in separating magnetic nanoparticles. The array provides a large region of relatively low magnetic field, yet high magnetic field gradient in agree- ment with finite element modeling calculations.
    [Show full text]
  • Semi-Analytical Modeling and Analysis of Halbach Array
    energies Article Semi-Analytical Modeling and Analysis of Halbach Array Min-Seob Sim and Jong-Suk Ro * School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06974, Korea; [email protected] * Correspondence: [email protected]; Tel.: +82-2-820-5557 Received: 5 February 2020; Accepted: 5 March 2020; Published: 8 March 2020 Abstract: Analysis of Halbach array placed in open space by using finite element method involves substantial consumption of memory, time, and cost. To address this problem, development of a mathematical modeling and analytic analysis method for Halbach array can be a solution, but research on this topic is currently insufficient. Therefore, a novel mathematical modeling and analytic analysis method for Halbach array in open space is proposed in this study, which is termed as the Ampere model and the Biot–Savart law (AB method). The proposed AB method can analyze the Halbach array rapidly and accurately with minimal consumption of memory. The usefulness of the AB method in terms of accuracy and memory and time consumption is verified by comparing the AB method with finite element method in this paper. Keywords: Halbach permanent magnet array; magnetic field analysis; mathematical model 1. Introduction Halbach array (HA) was proposed by K. Halbach to maximize the efficiency in a given volume of a permanent magnet (PM) via the combination of PMs, which are magnetized in diverse directions [1]. By combining PMs appropriately, an effective magnetic flux path can be obtained without using magnetic cores. The combination of the PMs is termed as HA. By the appropriate arrangement of PMs, which are magnetized in different directions, it is possible to divert the magnetic flux in unnecessary areas to the required area.
    [Show full text]
  • The University of Sheffield
    The University of Sheffield Novel Permanent Magnet Brushless Machines Having Segmented Halbach Array Yang Shen A thesis submitted for the degree of Doctor of Philosophy Department of Electronic and Electrical Engineering The University of Sheffield Mappin Street, Sheffield, S1 3JD, UK 15 November 2012 1 ABSTRACT Permanent magnet brushless machines having Halbach array exhibit a number of attractive features. Therefore, they have been increasingly applied to different market sectors, including aerospace, industrial, domestic, renewable, and healthcare, etc. The need of fast global optimization, cost-effective design, and physical understanding of the relationship between parameters and performance requires a powerful analytical model. This thesis develops a general analytical model which is capable of predicting the electromagnetic performance of slotted/slotless permanent magnet brushless machines with both even- and odd-segment Halbach array, having different magnet remanence, magnetization angle and arc for each single magnet segment. The validity of proposed analytical model is examined by finite- element analyses. The price of Neodymium Iron Baron magnet has been raised rapidly over the last few years, which has increased the awareness of cost-effective design and leads the magnet usage efficiency, viz. the ratio of average output torque over permanent magnet volume, to be an important design concern for industry applications. Meanwhile, the needs of high electromagnetic performance including lower torque ripple and sinusoidal air-gap flux density are also critically required. In order to meet such demands, the magnet poles having unequal-magnet height, modular high cost and low cost magnets, together with Halbach magnetization are proposed in this thesis. Based on the developed analytical models, extensive investigation has been performed.
    [Show full text]