Finite Element Magnetic Modeling Research Articles

A portable magnet for radiation biology and dosimetry studies in magnetic fields.

In the current and rapidly evolving era of real-time MRI-guided radiotherapy, our radiation biology and dosimetry knowledge is being tested in a novel way. This paper presents the successful design and implementation of a portable device used to generate strong localized magnetic fields. These are ideally suited for small-scale experiments that mimic the magnetic field environment inside an MRI-linac system, or more broadly MRI-guided particle therapy aswell. A portable permanent magnet-based device employing an adjustable steel yoke and magnetic field focusing cones has been designed, constructed, and tested. The apparatus utilizes two banks of Nd Fe B permanent magnets totaling around 50 kg in mass to generate a strong magnetic field throughout a small volume between two pole tips. The yoke design allows adjustment of the pole tip gap and exchanging of the focusing cones. Further to this, beam portal holes are present in the yoke and focusing cones, allowing for radiation beams of up to 5 5 cm to pass through the region of high magnetic field between the focusing cone tips. Finite element magnetic modeling was performed to design and characterize the performance of the device. Automated physical measurements of the magnetic field components at various locations were measured to confirm the performance. The adjustable pole gap and interchangeable cones allows rapid changing of the experimental set-up to allow different styles of measurements to beperformed. A mostly uniform magnetic field of 1.2 T can be achieved over a volume of at least 3 3 3 cm . This can be reduced in strength to 0.3 T but increased in volume to 10 10 10 cm via removal of the cone tips and/or adjustment of the steel yoke. Although small, these volumes are sufficient to house radiation detectors, cell culture dishes, and various phantom arrangements targeted at examining small radiation field dosimetry inside magnetic field strengths that can be changed with ease. Most important is the ability to align the magnetic field both perpendicular to, or inline with, the radiation beam. To date, the system has been successfully used to conduct published research in the areas of radiation detector performance, lung phantom dosimetry, and how small clinical electron beams behave in these strong magneticfields. A portable, relatively inexpensive, and simple to operate device has successfully been constructed and used for performing radiation oncology studies around the theme of MRI-guided radiotherapy. This can be in either inline and perpendicular magnetic fields of up to 1.2 T with x-ray and particlebeams.

High-precision magnetic field measurement and mapping of the LEReC 180° bending magnet using very low field NMR with Hall combined probe (140−350 G)

The relativistic heavy ion collider (RHIC) at BNL uses low-energy RHIC electron cooling (LEReC) to conduct experiments to search for the quantum chromodynamic critical point. The first ever electron cooling based on the RF acceleration of electron beams was experimentally demonstrated on April 5, 2019 using LEReC at BNL. The first critical step in obtaining successful 3D non-magnetized cooling of the Au ion bunches in the RHIC cooling section was matching the electron beam energy with a relative error less than 5 × 10−4 to the ion beam energy. Part of the LEReC beamline is a dipole magnet that bends the electron beam 180°. One of the most outstanding measurement challenges is that the dipole field is so low (≈200 G). Most of the existing NMR probes can only measure fields >400 G. A lower signal-to-noise ratio at low fields requires the use of larger sample volumes. Working with CAYLAR, the NMR probe has been redesigned and optimized for these low field measurements with high resolution. We report the methods, challenges and results for extensive magnetic field mappings of the 180° dipole magnet. A combination of NMR and Hall sensors was successfully implemented to measure uniform field regimes inside the magnet center area and non-uniform field regimes at the magnet ends. Detailed measurement and mapping were performed at five radii and five heights along the beam trajectory. Meanwhile, a finite element magnetic modeling simulation of the magnet using Opera software was performed. The calculated and measured data were compared, and the calculated data are a good reference for the measured data over long length mapping from the magnet edge to the center. The measured magnetic measurement data are directly useful for beam instrumentation, diagnostics and operation.

Dynamic Behavior of Superconductor-Permanent Magnet Levitation With Halbach Arrays for Flywheel Design and Control

Our research goal is to construct a general predictive model for the design and control of a flywheel energy storage system (FESS) that utilizes a superconductor-permanent magnetic levitation bearing. The FESS machine design is a hubless field-regulated reluctance machine for which the rotor of the machine is also the rotating mass for the flywheel. Reported are the results of several experiments that show the oscillatory reactions of the levitated systems. For these experiments, the levitation height and the amount of flux penetrating the superconductor is controlled by adding mass to the levitated Halbach array and by the initial cooling conditions. A small impulsive force is delivered to the levitated array, which is then allowed to freely oscillate until it has completely decayed. From this we can find an effective spring constant and damping coefficient for the levitated system as a function of the magnetic field densities and levitation height. The goal of the experiments reported is to understand the dynamic behaviors of a levitation system and incorporate those properties into the control model for the flywheel. Initial experiments have demonstrated near critically damped harmonic behavior when a magnet array levitated by a superconductor is delivered an impulsive force. Using the data from our experiments we aim to gain knowledge of the underlying physics of the forces of interaction and to create a predictive macroscopic model based on magnetic array and YBCO properties. We compare our measured results to those obtained by using the advanced image mirror method and finite element magnetic modeling.

P-003 development of an endovascular magnetic filter device to enable high dose intra-arterial chemotherapy: finite element modeling

Purpose A temporary endovascular magnetic filter was developed to remove iron oxide particles conjugated to chemotherapeutics from the blood, preventing chemotherapeutics from circulating where it is not needed to reduce systemic toxicity and enable higher dose therapy. Magnetically targeted drug delivery through filtration could play an important role in expanding intra-arterial therapy to head and neck cancer. Previous proof-of-concept established rapid high-capacity binding of iron oxide particles in swine serum in vitro , and preliminary demonstration of qualitative efficacy in vivo in a porcine model. In this study, we aim to optimize the filtration efficacy of the prototype through finite element magnetic modeling. Method Magnetic modeling was performed in 2D using Finite Element Method Magnetics (FEMM) software (Brighton, MA). Prototype designs consisting of individual neodymium N52 magnets were simulated to optimize the following parameters: i) magnetization across length vs diameter, ii) magnet orientations aligned or reversed, iii) magnet spacing, and iv) magnet length. The average magnetic flux gradient (∇By) was computed across a unit length consisting of one magnet and adjoining gap space as shown in [Figure 1A][1]. ∇By is directly correlated to the magnetic force on an iron particle, and was plotted as against D, distance from the surface of the magnet. Designs with greater ∇By at high D were considered more effective. Results Designs with magnetization across the length and reversed (like polarities facing and repelling each other), had slightly higher ∇By than designs with magnetization across the diameter and aligned (opposite polarities facing and attracting each other). Magnetization across the length and aligned, and magnetization across the diameter and reversed both had low ∇By at high D. For designs with magnetization across the length and reversed orientations as shown in [Figure 1B][1], reduced spacing between magnets increased ∇By. Reduced magnet length increased ∇By at low D, at the expense of ∇By at high D. Conclusions The current endovascular magnetic filter prototype could be improved by using longer magnets magnetized across the length in the reversed orientation with like polarities repelling each other and minimal spacing between magnets. ![Abstract P-003 Figure 1][2] Abstract P-003 Figure 1 Disclosures C. Sze: 1; C; NIH NCI. 5; C; ChemoFilter. M. Mabray: None. P. Lillaney: None. S. Kondapavulur: None. D. Liu: None. M. Wilson: 1; C; NIH NCI. 6; C; Penumbra. S. Hetts: 1; C; NIH NCI. 6; C; Penumbra. [1]: #F1 [2]: pending:yes

Performance Prediction of Inertial Auto-Reinforce Magnetic Flywheel Energy Storage Device Using Finite Element Magnetic Modeling

A new feature for flywheel energy storage device is proposed considering the deficiencies in former technology. This feature is introduced as auto-reinforce performance which means giving-back the kinetic energy for flywheel after speed-down occurred (as result of sudden loading). Auto-reinforce performance is an ability to recover the kinetic rotational energy which significantly keeps longer the stored energy of a flywheel device. This novel concept of flywheel is engineered by installing a number of Permanent Magnets (PM) in certain mounting. Hence, the magnetism configuration such magnetic strength, magnetic energy density, pole direction, geometry, and dimension are influential parameters to the mechanical performance. By practicing Finite Element Magnetic Modeling (FEMM), it is possible to predict some designed mechanical parameters such magnetic force and magnetic torque. Finally by evaluating these mechanical parameters, the key performance of this device such as percentage of energy reinforcement and percentage of discharge elongation can be predicted. The main ideas of this paper are: 1) presenting the development stages especially in design prediction using Finite Element Analysis (FEA) software; and 2) discovering the correlation of designed magnetic properties and mechanical parameters for prototyping references.

Auto-reinforce Magnetic Flywheel as Recent Advancement of Automobile Flywheel

A new feature for flywheel energy storage device is proposed, considering the deficiencies on existing technology. This feature is introduced as auto-reinforce performance which means an ability to recover the kinetic energy after speed-down occurred as impact of sudden loading or sudden braking. The performance will significantly keep longer the stored energy of a flywheel device. This novel concept of flywheel is engineered by installing a number of Permanent Magnets (PM). The magnetism configuration such magnetic strength, magnetic energy density, pole direction, geometry, and dimension are influential parameters to its performance. By executing Finite Element Magnetic Modeling, it is possible to predict the design parameters such magnetic force and magnetic torque. Finally by evaluating these mechanical parameters, the key performance of this device such as percentage of energy reinforcement and percentage of discharge elongation can be predicted for prototyping references.

Design, tests and commissioning of the EMMA injection septum

The paper describes the main steps taken during the design and commissioning stages of the EMMA injection and extraction septum magnets. A preliminary analysis of the problem is presented first followed by a discussion of the results obtained through finite element magnetic modeling and design optimization. The measures taken to suppress the stray field generated by the magnet are discussed in detail. Two sets of tests are performed on the magnet: magnetic field measurement resulting in a three-dimensional magnetic field map and measurement of the electron beam bending angle as a function of the magnet current. The values of the effective magnetic length resulting from the two sets of measurement are found to be in excellent agreement.

A comprehensive finite-element model of a turbine-generator infinite-busbar system

This paper shows the development of a two-dimensional finite-element magnetic model of a turbine generator coupled to an infinite busbar through a transmission line and a delta-star connected transformer. The finite-element equations of the machine are strongly coupled to the circuit equations of the transmission line and transformer. The circuit equations developed for the delta-star connection enable the simulation of several short circuit conditions at the transformer terminals with the aid of fault matrices. The calculation of electromagnetic torque is performed by surface integration of the Lorentz force, which leads to a unique result for the finite-element model used in this work. The coupling with the external controls of the machine (automatic voltage regulator and governor) is performed in a weak form. Nevertheless, any control model can be easily connected to the finite-element model. Since the use of this finite element model is meant for transient simulations, it is desirable to obtain some simplifications to speed up calculations. Hence, a three-phase current sheet is proposed in this work to avoid the explicit modelling of the stator coreback. This approach also leads to a simple approach to model motion, where remeshing is not necessary.

Two-dimensional finite element magnetic modeling for scalar hysteresis effects

A general transient simulation method accurately models the magnetic state of a device containing a ferromagnetic core by incorporating a scalar hysteresis model into the standard finite element framework. The method numerically implements the Jiles-Atherton hysteresis model to simulate hysteresis without introducing additional parameters to simulate minor loops. Additionally, it extends the finite element geometry to two-dimensional space by predefining directional vectors or element coordinate systems that specify the local field directions for which the scalar material model applies. The method is verified by applying it to a rotationally symmetric ferromagnetic core with a time harmonic current excitation. Finally, the verified technique is applied to model a square-shaped inductor core having a more general two-dimensional magnetic field distribution.