A preliminary feasibility study of potential market applications for non-commercial technology magnets
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29 ENERGY PLANNING, POLICY, AND ECONOMY↗
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Implementation of Maxwell's equations in the reconstruction of the magnetic field in the g -2 storage ring
We present a method for implementing the constraints that are implied by Maxwell's equations in fits to measurements of the magnetic field in the muon storage ring of the $g - 2$ experiment. The method that we use makes use of toroidal-harmonic solutions of Laplace's equation. We point out that the fitting problem can be approximated well as a linear-algebra problem. We have devised an efficient algorithm for the linear-algebra problem that makes it possible to find a solution for 10 5 data points and 10 4 harmonics in less than an hour on a present-day desktop computer. We illustrate our method by applying it to some preliminary measurements of the magnetic field in the $g - 2$ storage ring.
43 PARTICLE ACCELERATORS↗
Comprehensive Report on Design and Development of a 100-kW DSSRM
Switched reluctance machines (SRMs) are low cost and fault tolerant alternatives for traction applications. Due to their relatively low torque density and high torque ripple, these machines have not been used in commercialized electrified power trains yet. The double-stator magnetic configuration, where a segmental rotor shared between two stators, is proven to have superior torque density, lower acoustic noise, and torque pulsation. The double-stator SRM (DSSRM) has a high potential of being the next generation of traction motors since it combines the advantages of permanent magnet-free machines, such as low cost and independence from supply chain issues associated with rare metals, while providing high torque and power densities. In this paper, we introduce the complete design process of a 100-kW DSSRM including electromagnetic, structural, thermal, and system level design. The performance of the developed DSSRM is verified with the experimental data. This paper presents overall study of DSSRM and describes merits of DSSRM drive system.
42 ENGINEERING↗
Absolute energy calibration for relativistic electron beams with pointing instability from a laser-plasma accelerator
The pointing instability of energetic electron beams generated from a laser-driven accelerator can cause a serious error in measuring the electron spectrum with a magnetic spectrometer. In order to determine a correct electron spectrum, the pointing angle of an electron beam incident on the spectrometer should be exactly defined. Here, we present a method for absolutely calibrating the electron spectrum by monitoring the pointing angle using a scintillating screen installed in front of a permanent dipole magnet. The ambiguous electron energy due to the pointing instability is corrected by the numerical and analytical calculations based on the relativistic equation of electron motion. It is also possible to estimate the energy spread of the electron beam and determine the energy resolution of the spectrometer using the beam divergence angle that is simultaneously measured on the screen. The calibration method with direct measurement of the spatial profile of an incident electron beam has a simple experimental layout and presents the full range of spatial and spectral information of the electron beams with energies of multi-hundred MeV level, despite the limited energy resolution of the simple electron spectrometer.
43 PARTICLE ACCELERATORS↗
Magnetic hardening of Ce1+xFe11-yCoyTi with ThMn12 structure by melt spinning
A recent study on the intrinsic magnetic properties of CeFe11-yCoyTi has revealed that substituting one Co for Fe retains the favorable magnetocrystalline anisotropy H-a found in the ternary Fe end member, while enhancing the Curie temperature T-c and saturation magnetization 4 pi M-s. These findings warrant further optimization around Co substitution y = 1 to try to exploit the hard magnetic properties of these Ce-based magnets. Both Ce and Co concentrations in Ce1+xFe11-yCoyTi have been optimized in the range of x = 0 0.2 and y = 0 1.5. It was found that Co substitution effectively enhances all hard magnetic properties, although the values are still lower than those predicted from the intrinsic magnetic properties. Specifically, Tc increases from 210 degrees C to 285-350 degrees C; 4 pi M-19 (magnetization at 19 kOe) from 8.9 kG to 10.5-11.5 kG, remanence B-r from 3.1 kG to 4.1-4.5 kG, and most importantly, H-ci from 1.1 kOe to 1.5 kOe. As a result, the room temperature energy product (BH)(max) has been increased by over 100% from 0.7 MGOe in Ce1.1Fe11Ti to 1.5 MGOe in Ce1.05Fe9.75Co1.25Ti. Microscopy analysis indicates that the addition of Co refines the grain size and promotes chemical homogeneity at the microscopic scale. The beneficial effect of Co on the microstructure contributes to the improved hard magnetic properties. (C) 2015 AIP Publishing LLC.
Zhou, C↗
High-Performance MnBi Alloy Prepared Using Profiled Heat Treatment
The profiled heat treatment (PHT) method has been used to synthesize MnBi alloys with high-purity low-temperature phase (LTP). In the PHT method, the arc-melted MnBi alloy was remelted then slowly cooled by a pseudo-equilibrium solidification process to promote the formation of LTP phase. The PHT-treated MnBi alloys had an LTP phase up to 94 wt.% and a magnetization of 73 emu/g under a field of 9 T. Scanning electron microscopy showed that there exist some micrometer-sized Mn-rich inclusions in the LTP matrix of the PHT MnBi alloy. The PHT MnBi alloys were crushed into powders with an average size of ~3 μm by low-energy ball milling. These MnBi powders were aligned in an 18 kOe field and warm compacted into a bulk magnet at 300 °C for 30 min. The magnet had a density of 8.2 g/cm3 and magnetic properties of Ms = 6.7 kG, Mr = 5.3 kGs, i Hc = 5 kOe, and (BH)max = 6.1 MGOe
MnBi↗
Development of DRAGON electron cyclotron resonance ion source at Institute of Modern Physics
A new room temperature electron cyclotron resonance (ECR) ion source, DRAGON, is under construction at IMP. DRAGON is designed to operate at microwaves of frequencies of 14.5-18 GHz. Its axial solenoid coils are cooled with evaporative medium to provide an axial magnetic mirror field of 2.5 T at the injection and 1.4 T at the extraction, respectively. In comparison to other conventional room temperature ECR ion sources, DRAGON has so far the largest bore plasma chamber of inner diameter of 126 mm with maximum radial fields of 1.4-1.5 T produced by a non-Halbach permanent sextupole magnet.
43 PARTICLE ACCELERATORS↗
High-force NdFeB-based magnetic tweezers device optimized for microrheology experiments
We present the design, calibration, and testing of a magnetic tweezers device that employs two pairs of permanent neodymium iron boron magnets surrounded by low-carbon steel focusing tips to apply large forces to soft materials for microrheology experiments. Our design enables the application of forces in the range of 1-1800 pN to {approx}4.5 {mu}m paramagnetic beads using magnet-bead separations in the range of 0.3-20 mm. This allows the use of standard coverslips and sample geometries. A high speed camera, custom LED-based illumination scheme, and mechanically stabilized measurement platform are employed to enable the measurement of materials with viscoelastic moduli as high as {approx}1 kPa.
36 MATERIALS SCIENCE↗
Effects of High Magnetic Fields on Phase Transformations in Amorphous Nd2Fe14B
We briefly summarize the results from a set of experiments designed to demonstrate the effects of high magnetic fields applied during thermal annealing of amorphous Nd2Fe14B produced through melt-spinning. A custom-built differential scanning calorimeter was used to determine the crystallization temperatures in zero-field and in applied fields of 20 kOe and 90 kOe, which guided subsequent heat treatments to evaluate phase evolution. X-ray diffraction was used for phase identification and transmission electron microscopy was employed for observation of the crystallite size and morphology. Magnetization measurements were also used to evaluate the resulting magnetic phases after thermomagnetic processing. While the applied magnetic fields do not appear to affect the crystallization temperature, significant effects on the kinetics of phase evolution are observed and correlated strongly to the magnetic behavior.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Heavy ion beam physics at Facility for Rare Isotope Beams
The Facility for Rare Isotope Beams (FRIB) will be the world's premier rare-isotope beam facility. Experiments with the majority (~80%) of the isotope predicted to exist will become available. The FRIB facility is based on a superconducting (SC) heavy ion linac with output energy above 200 MeV/u for any ions at beam power of 400 kW. FRIB includes a target facility for in-flight production of rare isotopes. A three-stage fragment separator will be used to prepare fast rare isotope beams with high-purity for nuclear physics experiments. The installation work of the accelerator and experimental systems is approaching completion and multi-stage beam commissioning activities started in summer 2017 with expected project completion in early 2022. In conclusion, the commencement of operation for users' experiments is planned immediately following the project completion.
43 PARTICLE ACCELERATORS↗
Hard magnetic properties observed in bulk Mn 1–x Ga x
Here, Mn-Ga binary alloys have shown promising magnetic properties, even though these alloys contain no rare-earth metals. Both theoretical predictions and experimental work showed that nanoscaled Mn-Ga samples, such as thin films could have remarkable magnetic properties. Although the prediction provides a useful guideline and thin films supply us with materials in some application, bulk materials are required for majority of the applications that require a strong magnetic field. We have made bulk Mn 1-x Ga x alloys by mechanically milling and heat treatments. In this paper, we report annealed Mn 1-x Ga x bulk composites that exhibit coercivity up to 18.8 kOe.
36 MATERIALS SCIENCE↗
Enhancement of hard magnetism and chemical order of synthetic L 1 0 -FeNi
An ordered tetragonal L 1 0 -FeNi, also known as meteoritic mineral tetrataenite – a promising rare-earth-free hard-magnetic compound – has been synthesized starting from a mechanochemically-activated disordered cubic A1-FeNi via formation of a chemically-ordered FeNiN intermediate and its subsequent denitrogenation and further purification of the product. The nature of a process control agent employed during the mechanochemical activation of A1-FeNi and ammonia flow velocity during the synthesis of the intermediate are two of the main factors controlling the nitrogenation. Denitrogenation with hydrogen at elevated pressures and at temperatures substantially below the order-disorder L 1 0 -FeNi → A1-FeNi transition preserves the chemical order established in the intermediate nitride. Further, post-synthesis refinement of the L 1 0 -FeNi product includes the removal of residual nitrides with a dilute acid to further improve hard-magnetic properties of the material. The L 1 0 -FeNi powders synthesized using this method exhibit a coercivity as high as 2.3 kOe and a maximum energy product reaching 6 MGOe – the highest values ever reported for a synthetic tetrataenite.
36 MATERIALS SCIENCE↗
Crystal structure and magnetic properties of CeFe 11 M (M = Mo, W)
Tetragonal CeFe 11 Mo (struct. type ThMn 12 , a = 8.529(1) Å, c = 4.766(1) Å, V = 346.68(1) Å 3 ) and novel isostructural CeFe 11 W (a = 8.539(1) Å, c = 4.754(1) Å, V = 346.62(1) Å 3 ) are obtained in bulk, as homogenized single-phase arc-melted alloys. Here, their crystal structures are evaluated by full profile Rietveld analysis of the powder X-ray diffraction patterns which confirm that Ce occupies the 2a atomic site in both cases, whereas atomic disorder is present in the Fe-sublattice, i.e., predominantly on the dumbbell 8i site and minorly on two other sites 8j and 8f. In CeFe 11 Mo the third element, M, is mixed with Fe on the 8i dumbbell site and 8f atomic position, whereas in CeFe 11 W, M is mixed on the 8i and 8j Fe sites. In these bulk CeFe 12-x M x alloys the tetragonal structure persists at lower M content, x < 1 here, in comparison to known similar alloys, with x > 1. Because of the low M content, comparably higher values of mass magnetization and Curie temperature are achieved i.e., CeFe 11 Mo: ϭ s = 104 emu/g (14.7 µ B /f.u.), T c = 420 K and CeFe 11 W: ϭ s = 99 emu/g (16.5 µ B /f.u.), T c = 450 K. Magnetocrystalline anisotropy is uniaxial with anisotropy fields H a ∼ 14.5 and 16.5 kOe, respectively. Based on Curie temperature and magnetic anisotropy enhancements, using tungsten as the stabilizing dopant is more beneficial than molybdenum.
36 MATERIALS SCIENCE↗
Sustainable Urban Mining of Critical Elements from Magnet and Electronic Wastes
Here, we created a straightforward and environment-friendly process for acid-free leaching of rare-earth elements and cobalt, which are vital materials, from waste magnet materials. The process also allows for selective leaching of rare-earth elements from magnet-containing electronic wastes, such as end-of-life hard disk drives and electric motors. The use of copper salts eliminates the use of volatile toxic acids in the dissolution and separation processes, which provides for a more eco-friendly approach to recovering critical elements and a safer work environment. Recovered critical materials were shown to be suitable for reinsertion into the materials supply chain.
36 MATERIALS SCIENCE↗
Bulk magnetic hardening in Sm(Fe,V) 12 alloys
Cast Sm-Fe-V magnets with the tetragonal crystal structure of the ThMn 12 type were prepared with high coercivity through a two-step annealing at 775°C and then at 825°C. The annealing processing used allowed us for the first time to successfully produce a large amount of non-magnetic Sm-rich grain-boundary phase in Sm-Fe-V cast ingots. As a result, the sample with composition Sm 11.1 Fe 75.8 V 13.1 showed the record-high coercivity (6.66 kOe) after annealing at 775°C for 72 h and then 825°C for 2 h. Furthermore, this coercivity, achieved without the use of powder metallurgy, has nearly doubled compared to the previously reported highest value of 3.70 kOe in a cast SmFe 10 V 2 .
36 MATERIALS SCIENCE↗
Design Considerations of a Transverse Flux Machine for Direct-Drive Wind Turbine Applications
This paper presents the design considerations of a double-sided transverse flux machine (TFM) for direct-drive wind turbine applications. The proposed TFM has a modular structure with quasi-U stator cores and toroidal ring windings. The rotor is constructed with ferrite magnets in a flux-concentrating setup to achieve high air gap flux density. Pole number selection is critical in the design process of a TFM as it affects both the torque density and power factor under fixed magnetic and changing electrical loading. Several key design ratios are introduced to facilitate the initial design procedure. The effect of pole shaping on back-EMF and inductance is also analyzed. These investigations provide guidance toward the required design of a TFM for direct-drive applications. The analyses are carried out using analytical and three-dimensional finite element analysis (FEA). A proof-of-concept prototype was developed to experimentally validate the FEA results.
17 WIND ENERGY↗
New alnico magnets fabricated from pre-alloyed gas-atomized powder through diverse consolidation techniques
Fine Alnico 8 spherical powder produced by gas atomization was consolidated through hot pressing (HP), hot isostatic pressing (HIP), and compression molding and subsequent sintering (CMS) techniques. The effects of different fabrication techniques and processing parameters on microstructure and magnetic properties were analyzed and compared. The HP, HIP, and CMS magnets exhibited different features in microstructures and magnetic properties. Magnetically annealed at 840°C for 10 min and subsequently tempered at 650°C for 5h and 580°C for 15h, the HIP sample achieved the best coercivity (H cj =1845 Oe) due to spinodally decomposed (SD) phases with uniform and well-faceted mosaic morphology. As a result, the CMS sample had a lower Hcj than HIP and HP samples, but a higher remanence and thus the best energy product (6.5 MGOe) due to preferential grain alignment induced by abnormal grain growth.
36 MATERIALS SCIENCE↗