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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,189 records · Page 66
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Assessment of Alphamagnetic Spectrometer (AMS) Upper Experiment Structural Configuration Shielding Effectiveness Associated with Change from Cryo-Cooled Magnet to Permanent Magnet

In the spring of 2010, the Alpha Magnetic Spectrometer 2 (AMS-02) underwent a series of system level electromagnetic interference control measurements, followed by thermal vacuum testing. Shortly after completion of the thermal vacuum testing, the project decided to remove the cryogenically cooled superconducting magnet, and replace it with the original permanent magnet design employed in the earlier AMS- 01 assembly. Doing so necessitated several structural changes, as well as removal or modification of numerous electronic and thermal control devices and systems. At this stage, the project was rapidly approaching key milestone dates for hardware completion and delivery for launch, and had little time for additional testing or assessment of any impact to the electromagnetic signature of the AMS-02. Therefore, an analytical assessment of the radiated emissions behavioural changes associated with the system changes was requested.

Scully, Robert↗
NASA NTRS2013

Micromachined Active Magnetic Regenerator for Low-Temperature Magnetic Coolers

A design of an Active Magnetic Regenerative Refrigeration (AMRR) system has been developed for space applications. It uses an innovative 3He cryogenic circulator to provide continuous remote/distributed cooling at temperatures in the range of 2 K with a heat sink at about 15 K. A critical component technology for this cooling system is a highly efficient active magnetic regenerator, which is a regenerative heat exchanger with its matrix material made of magnetic refrigerant gadolinium gallium garnet (GGG). Creare Inc. is developing a microchannel GGG regenerator with an anisotropic structured bed for high system thermal efficiency. The regenerator core consists of a stack of thin, single-crystal GGG disks alternating with thin polymer insulating layers. The insulating layers help minimize the axial conduction heat leak, since GGG has a very high thermal conductivity in the regenerator s operating temperature range. The GGG disks contain micro channels with width near 100 micrometers, which enhance the heat transfer between the circulating flow and the refrigerant bed. The unique flow configuration of the GGG plates ensures a uniform flow distribution across the plates. The main fabrication challenges for the regenerator are the machining of high-aspect-ratio microchannels in fragile, single-crystal GGG disks and fabrication and assembly of the GGG insulation layers. Feasibility demonstrations to date include use of an ultrashort- pulse laser to machine microchannels without producing unacceptable microcracking or deposition of recast material, as shown in the figure, and attachment of a thin insulation layer to a GGG disk without obstructing the flow paths. At the time of this reporting, efforts were focused on improving the laser machining process to increase machining speed and further reduce microcracking.

Chen, Weibo↗
DOE OSTI2016

System and method for magnetic current density imaging at ultra low magnetic fields

Preferred systems can include an electrical impedance tomography apparatus electrically connectable to an object; an ultra low field magnetic resonance imaging apparatus including a plurality of field directions and disposable about the object; a controller connected to the ultra low field magnetic resonance imaging apparatus and configured to implement a sequencing of one or more ultra low magnetic fields substantially along one or more of the plurality of field directions; and a display connected to the controller, and wherein the controller is further configured to reconstruct a displayable image of an electrical current density in the object. Preferred methods, apparatuses, and computer program products are also disclosed.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Passive magnetic bearing systems stabilizer/bearing utilizing time-averaging of a periodic magnetic field

A high-stiffness stabilizer/bearings for passive magnetic bearing systems is provide where the key to its operation resides in the fact that when the frequency of variation of the repelling forces of the periodic magnet array is large compared to the reciprocal of the growth time of the unstable motion, the rotating system will feel only the time-averaged value of the force. When the time-averaged value of the force is radially repelling by the choice of the geometry of the periodic magnet array, the Earnshaw-related unstable hit motion that would occur at zero rotational speed is suppressed when the system is rotating at operating speeds.

42 ENGINEERING↗
DOE OSTI2018

Iron nitride permanent magnet and technique for forming iron nitride permanent magnet

A permanent magnet may include a Fe 16 N 2 phase constitution. In some examples, the permanent magnet may be formed by a technique that includes straining an iron wire or sheet comprising at least one iron crystal in a direction substantially parallel to a <001> crystal axis of the iron crystal; nitridizing the iron wire or sheet to form a nitridized iron wire or sheet; annealing the nitridized iron wire or sheet to form a Fe 16 N 2 phase constitution in at least a portion of the nitridized iron wire or sheet; and pressing the nitridized iron wires and sheets to form bulk permanent magnet.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Small bore magnetic measurement system, method for measuring small bore magnets

The invention provides a system for measuring magnets, the system comprising a guide tube removably received by a beam chamber tunnel, wherein said guide tube has a first end terminating at a first end of the tunnel and a second end terminating at a second end of the tunnel; a flexible substrate removably and slidably received by the tube, wherein the flexible substrate has a first end and a second end; a first rotary stage removably attached to the first end of said flexible substrate and a second rotary stage removably attached to the second end of said flexible substrate wherein the first rotary stage and the second rotary stage effects movement of the substrate through the tube; and a Hall probe supported by the flexible substrate. Also provided is a method for measuring magnetic fields, the method comprising extending a measuring probe into a magnetic core while maintaining the probe at ambient temperature and pressure.

Kasa, Matthew T.↗
DOE OSTI2022

Methods and systems for low to ultra-low magnetic field nuclear magnetic resonance for detecting chemical nerve agents

A nuclear magnetic resonance (NMR) system is configured to detect chemical threat material. The system comprises a magnet configured to generate a magnetic field of about 300 millitesla or less; and a probe configured to detect nuclear relaxation of at least two nuclei selected from the group consisting of 1H, 19F, 31P and 14N, and detect the spin density of nuclei selected from the group consisting of 1H, 19F, 31P and 14N, following excitation.

Williams, Robert F.↗
DOE OSTI2023

Iron nitride permanent magnet and technique for forming iron nitride permanent magnet

A permanent magnet may include a Fe 16 N 2 phase constitution. In some examples, the permanent magnet may be formed by a technique that includes straining an iron wire or sheet comprising at least one iron crystal in a direction substantially parallel to a <001> crystal axis of the iron crystal; nitridizing the iron wire or sheet to form a nitridized iron wire or sheet; annealing the nitridized iron wire or sheet to form a Fe 16 N 2 phase constitution in at least a portion of the nitridized iron wire or sheet; and pressing the nitridized iron wires and sheets to form bulk permanent magnet.

Wang, Jian-Ping↗
DOE OSTI2024

Magnetic Field Sensing via Optically Detected Magnetic Resonance and Spin Relaxometry Using Nitrogen Vacancies in Nanodiamonds

Quantum sensing is broadly defined as the use of quantum materials, quantum coherence, and/or quantum entanglement to measure physical quantities and/or to enhance the sensitivity of classical analytical measurements. Certain materials exhibit interesting quantum properties that have the potential to be utilized in quantum sensing applications. One such quantum property is electronic spin, which is utilized in this work. Here, we built a custom apparatus capable of conducting both optically detected magnetic resonance (ODMR) and spin relaxometry. The quantum material investigated was an ensemble of nitrogen vacancies (NV) in nanodiamonds. We have characterized the system and measured ODMR spectra for different strengths of the applied DC magnetic field and clearly observed the expected splitting of the resonances due to Zeeman splitting. We also have measured the spin relaxation times for two different powers of the applied AC magnetic field. The lower power dataset exhibited expected exponential temporal dependence of the relaxation of a modified spin state, whereas the higher power dataset exhibited stretched exponential dependence of the modified spin state, indicating the presence of high-power phenomena that emerge that retard the relaxation of the spin state.

Lander, Gary↗
DOE OSTI2018

Effects of Fe and Co Co-doping on Structural, Magnetic, and Optical Properties of Ti{sub 0.9}Fe{sub 0.1−x}Co{sub x}O{sub 2} Magnetic Semiconductors

A series of six samples with a general formula Ti{sub 0.9}Fe{sub 0.1−x}Co{sub x}O{sub 2} (x = 0.0, 0.02, 0.04, 0.06, 0.08, and 0.1) has been synthesized by solid-state reaction method at annealing temperature of 1150 {sup ∘}C for 2 hours. The synthesized samples have been characterized by X-ray diffractometer, Raman spectroscopy, scanning electron microscopy, EDX, vibrating sample magnetometer, and ultraviolet-visible spectroscopy to investigate structural, defective, morphological, elemental, magnetic, and optical properties. Structural analysis revealed dominant structure of rutile with a minor peak of hematite and anatase. An intensity loss and peak broadening of TiO{sub 2} (rutile) vibration lines has been observed from Raman analysis. Magnetic characterization showed ferromagnetic behavior at room temperature. Optical characterization revealed blue shift in band gap energy with increasing amount of Co concentration.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Wave-Vector Filtering Effect in a Novel Magnetic Nanostructure with Zero Average Magnetic Field

We report a theoretical investigation on wave-vector filtering (WVF) effect in a magnetic nanostructure, which can be experimentally realized by depositing ferromagnetic (FM) stripes on the surface of GaAs/Al{sub x}Ga{sub 1-x}As heterostructure. An appreciable WVF effect appears in this nanosystem. The WVF efficiency is associated with structural parameters of magnetic nanostructure. Therefore, such a device can be employed as a momentum filter for nanoelectronics device applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Synthesis and Characterization of Hydrophobic Fe{sub 3}O{sub 4} Magnetic Nanoparticles with High Saturation Magnetization

A simple one-step solvothermal method is proposed to prepare hydrophobic Fe{sub 3}O{sub 4} nanoparticles (MNPs) using iron acetylacetonate (Fe(acac){sub 3}), oleylamine (OAm), and ethylene glycol (EG). X-ray powder diffraction, scanning electron microscope, infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectrometry, and vibrating sample magnetometer are used to characterize the structure, morphology, and properties of products. The testing results indicate that the as-synthesized products are spherical-like hydrophobic MNPs, superparamagnetic at room temperature, with a saturation magnetization up to 76.8 emu/g. The good hydrophobic property of MNPs is attributed to the coverage of oleylamine, without causing a remarkable loss of magnetic property. In addition, the influences of material ratio, aging time, oleic acid, and stearic acid used as additives are studied in our research.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2014

Partial homogeneity based high-resolution nuclear magnetic resonance spectra under inhomogeneous magnetic fields

In nuclear magnetic resonance (NMR) technique, it is of great necessity and importance to obtain high-resolution spectra, especially under inhomogeneous magnetic fields. In this study, a method based on partial homogeneity is proposed for retrieving high-resolution one-dimensional NMR spectra under inhomogeneous fields. Signals from series of small voxels, which characterize high resolution due to small sizes, are recorded simultaneously. Then, an inhomogeneity correction algorithm is developed based on pattern recognition to correct the influence brought by field inhomogeneity automatically, thus yielding high-resolution information. Experiments on chemical solutions and fish spawn were carried out to demonstrate the performance of the proposed method. The proposed method serves as a single radiofrequency pulse high-resolution NMR spectroscopy under inhomogeneous fields and may provide an alternative of obtaining high-resolution spectra of in vivo living systems or chemical-reaction systems, where performances of conventional techniques are usually degenerated by field inhomogeneity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

A comparison of numerical simulations and analytical theory of the dynamics of interacting magnetic vortices

Magnetostatic interactions between vortices in closely spaced planar structures are important for applications including vortex-based magnonic crystals and spin torque oscillator networks. Analytical theories that include magnetostatic interaction effects have been proposed but have not yet been rigorously tested. Here, we compare micromagnetic simulations of the dynamics of magnetic vortices confined in three disks in an equilateral triangle configuration to analytical theories that include coupling. Micromagnetic simulations show that the magnetostatic coupling between the disks leads to splitting of the gyrotropic resonance into three modes and that the frequency splitting increases with decreasing separation. The temporal profiles of the magnetization depend on the vortex polarities and chiralities; however, the frequencies depend only on the polarity combinations and will fall into one of two categories: all polarities equal or one polarity opposite to the others, where the latter leads to a larger frequency splitting. Although the magnitude of the splitting observed in the simulations is larger than what is expected based on purely dipolar interactions, a simple analytical model that assumes dipole-dipole coupling captures the functional form of the frequency splitting and the motion patterns just as well as more complex models.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗