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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Magnetic core/shell-type composites composed of coarse FePt particles coated with finely powdered iron nitride

Highlights: • Magnetic core/shell-type composites were prepared on α″-Fe{sub 16}N{sub 2}-like compound with FePt core. • α″-Fe{sub 16}N{sub 2}-like compound grew epitaxially on the FePt core. • Magnetic coupling increased the magnetic coercivity of α″-Fe{sub 16}N{sub 2}-like compound. - Abstract: Although α″-Fe{sub 16}N{sub 2}-like compounds exhibit enhanced magnetization compared to α-Fe, it is important to increase their magnetic coercivity to obtain new hard magnetic materials for electric vehicle application. In the present work, coarse FePt particles were coated with finely powdered Fe{sub 3}O{sub 4} produced by the hydrolysis of Fe(acac){sub 3} in benzyl alcohol. This Fe{sub 3}O{sub 4} coating layer was subsequently reduced under hydrogen and then nitrided by ammonolysis at 150 °C to obtain a dual-phase mixture of an α″-Fe{sub 16}N{sub 2}-like compound (referred to herein as “α″-Fe{sub 16}N{sub 2}”) and residual α-Fe. The (“α″-Fe{sub 16}N{sub 2}” + α-Fe){sub 1-x}/(FePt){sub x} composite particles for which x = 0.2, 0.4 or 0.6 generated smooth magnetization hysteresis curves, and the magnetic coercivity of these materials increased with increases in the proportion of FePt. Magnetic coupling was clearly evident between the core and shell regions in the composite powder for which x = 0.6, as demonstrated by a plot of the Wohlfarth interaction against the magnetic field. Transmission electron microscopy images confirmed magnetic coupling between the coarse FePt particles (several hundred nm in diameter) and the coating of fine mixed particles (several tens of nm in diameter) of “α″-Fe{sub 16}N{sub 2}” and α-Fe. The “α″-Fe{sub 16}N{sub 2}” crystals forming the particle shell were found to grow epitaxially, aligning their c-axes parallel to that of the tetragonal FePt.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Gapless core reactor

A gapless core reactor includes a saturable magnetic core having reactor legs without air gaps and multiple windings. The windings are each wound around a common leg, spaced apart from each other and connected in counter series. The windings are configured such that a magnetic flux generated from an alternating current flowing through the windings generates a plurality of substantially equal and counter magnetic fluxes flowing through two or more separate magnetic circuits.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS2003

Performance of the NASA Digitizing Core-Loss Instrumentation

The standard method of magnetic core loss measurement was implemented on a high frequency digitizing oscilloscope in order to explore the limits to accuracy when characterizing high Q cores at frequencies up to 1 MHz. This method computes core loss from the cycle mean of the product of the exciting current in a primary winding and induced voltage in a separate flux sensing winding. It is pointed out that just 20 percent accuracy for a Q of 100 core material requires a phase angle accuracy of 0.1 between the voltage and current measurements. Experiment shows that at 1 MHz, even high quality, high frequency current sensing transformers can introduce phase errors of a degree or more. Due to the fact that the Q of some quasilinear core materials can exceed 300 at frequencies below 100 kHz, phase angle errors can be a problem even at 50 kHz. Hence great care is necessary with current sensing and ground loops when measuring high Q cores. Best high frequency current sensing accuracy was obtained from a fabricated 0.1-ohm coaxial resistor, differentially sensed. Sample high frequency core loss data taken with the setup for a permeability-14 MPP core is presented.

Schwarze, Gene E.↗
DOE OSTI2018

Verification of 5D continuum gyrokinetic code COGENT: Studies of kinetic drift wave instability

COGENT (Continuum Gyrokinetic Edge New Technology) is a kinetic plasma simulation code that is being developed by the edge simulation laboratory (ESL) collaboration. The original version of the code has been developed in a 4D phase space (2D configuration space and 2D velocity space) to address kinetic plasma phenomena in a complex magnetic field geometry including the core, magnetic separatrix, and scrape-off layer regions. This paper is focused on extending the original 4D phase space to a 5D phase space (3D2V) to address full kinetic turbulences in a tokamak edge region. Here, we report on the current status of 5D COGENT, which presently operates in a shear-less, simple slab geometry. As a verification study, we use the problems of collision-less drift wave instability (universal instability) including its modification in the presence of collisional effects. The simulation model includes the gyrokinetic equations for ion and electron species coupled to the long-wavelength limit of the gyro-Poisson equation. Collisional effects are represented by the Krook collision model. Linear analytical results for the drift mode growth rate and real frequency are recovered, and the non-linear stage is modelled and analysed as well. In addition, extensive 5D runs have been performed to address the effects of the drift wave instability on blob/filamentary structures characteristic of a tokamak edge. Finally, a helical-shaped potential perturbation is observed to grow exponentially in time while spinning around the filament axis with electron drift frequency.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1992

The orbital record in stratigraphy

Orbital signals are being discovered in pre-Pleistocene sediments. Due to their hierarchical nature these cycle patterns are complex, and the imprecision of geochronology generally makes the assignment of stratigraphic cycles to specific orbital cycles uncertain, but in sequences such as the limnic Newark Group under study by Olsen and pelagic Cretaceous sequence worked on by our Italo-American group the relative frequencies yield a definitive match to the Milankovitch hierarchy. Due to the multiple ways in which climate impinges on depositional systems, the orbital signals are recorded in a multiplicity of parameters, and affect different sedimentary facies in different ways. In platform carbonates, for example, the chief effect is via sea-level variations (possibly tied to fluctuating ice volume), resulting in cycles of emergence and submergence. In limnic systems it finds its most dramatic expression in alternations of lake and playa conditions. Biogenic pelagic oozes such as chalks and the limestones derived from them display variations in the carbonate supplied by planktonic organisms such as coccolithophores and foraminifera, and also record variations in the aeration of bottom waters. Whereas early studies of stratigraphic cyclicity relied mainly on bedding variations visible in the field, present studies are supplementing these with instrumental scans of geochemical, paleontological, and geophysical parameters which yield quantitative curves amenable to time-series analysis; such analysis is, however, limited by problems of distorted time-scales. My own work has been largely concentrated on pelagic systems. In these, the sensitivity of pelagic organisms to climatic-oceanic changes, combined with the sensitivity of botton life to changes in oxygen availability (commonly much more restricted in the Past than now) has left cyclic patterns related to orbital forcing. These systems are further attractive because (1) they tend to offer depositional continuity, and (2) presence of abundant microfossils yields close ties to geochronology. A tantalizing possibility that stratigraphy may yield a record of orbital signals unrelated to climate has turned up in magnetic studies of our Cretaceous core. Magnetic secular variations here carry a strong 39 ka periodicity, corresponding to the theoretical obliquity period of that time - Does the obliquity cycle perhaps have some direct influence on the magnetic field?

Fischer, Alfred G.↗
NASA NTRS1994

Materials for efficient high-flux magnetic bearing actuators

Magnetic bearings have demonstrated the capability for achieving positioning accuracies at the nanometer level in precision motion control stages. This makes possible the positioning of a wafer in six degrees of freedom with the precision necessary for photolithography. To control the position of an object at the nanometer level, a model of the magnetic bearing actuator force-current-airgap relationship must be accurately obtained. Additionally, to reduce thermal effects the design of the actuator should be optimized to achieve maximum power efficiency and flux density. Optimization of the actuator is accomplished by proper pole face sizing and utilizing a magnetic core material which can be magnetized to the highest flux density with low magnetic loss properties. This paper describes the construction of a magnetic bearing calibration fixture designed for experimental measurement of the actuator force characteristics. The results of a material study that review the force properties of nickel-steel, silicon-steel, and cobalt-vanadium-iron, as they apply to magnetic bearing applications are also presented.

Williams, M. E.↗
DOE OSTI2022

FNAL PIP-II Accumulator Ring

The FNAL accelerator complex is poised to reach MW neutrino beams on target for the exploration of the dark sector physics and rare physics program spaces. Future operations of the complex will include CW linac operations at beam intensities that have not been seen before \cite{PIP2,RCS_LOI}. The ambitious beam program relies on multi-turn H$^{-}$ injection into the FNAL Booster and then extracted into delivery rings or the Booster Neutrino Beam (BNB) 8 GeV HEP program. A new rapid-cycling synchrotron (RCS) will be required to reach the LBNF goal of 2.4 MW because of intense space-charge limitations. There are many accelerator engineering challenges that are already known and many that will be discovered. This proposal calls for an intermediate step that will both facilitate the operation of Booster in the PIP-II era and gain operational experience associated with high power injection rings. This step includes the design, construction and installation of a 0.8 GeV accumulator ring (upgradeable to 1+ GeV) to be located in the PIP-II Booster Transfer Line (BTL). The PIP-II accumulator ring (PAR) may be primarily designed around permanent magnets or use standard iron core magnet technology with an aperture selected to accommodate the desired high intensity protons at 0.8 GeV.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Feasibility and electromagnetic analysis of a REBCO superconducting undulator

Recent advances in second-generation (2G) high temperature superconducting (HTS) coated conductors (CCs) have made them very attractive for new applications such as undulators. In this study, we have, for the first time, experimentally evaluated a design to validate applicability of 2G-HTS tapes for next generation undulator magnetic structures. A two-period undulator magnetic core was fabricated and 2G-HTS CCs were successfully wound onto the undulator core. The performance of the undulator magnetic structure was investigated and the highest engineering current density, J e , in such configuration reported yet was obtained. A new U-slit tape configuration was used to reduce the number of resistive joints and it was shown that with this new technique affordable levels of resistance values can be achieved for short length undulators. The ferromagnetic core was designed such as to accommodate winding the U-slit tapes. Finally, test results indicated that the winding and the soldering procedures are successful and do not deteriorate the performance of the 2G-HTS tapes.

2G-HTS↗
DOE OSTI2018

r-Process nucleosynthesis from three-dimensional jet-driven core-collapse supernovae with magnetic misalignments

We investigate r-process nucleosynthesis in three-dimensional general relativistic magnetohydrodynamic simulations of jet-driven supernovae resulting from rapidly rotating, strongly magnetized core-collapse. We explore the effect of misaligning the pre-collapse magnetic field with respect to the rotation axis by performing four simulations: one aligned model and models with 15°, 30°, and 45° misalignments. The simulations we present employ a microphysical finite-temperature equation of state and a leakage scheme that captures the overall energetics and lepton number exchange due to post-bounce neutrino emission and absorption. We track the thermodynamic properties of the ejected material with Lagrangian tracer particles and analyse its composition with the nuclear reaction network SKYNET. By using different neutrino luminosities in post-processing the tracer data with SKYNET, we constrain the impact of uncertainties in neutrino luminosities. We find that, for the aligned model considered here, the use of an approximate leakage scheme results in neutrino luminosity uncertainties corresponding to a factor of 100–1000 uncertainty in the abundance of third peak r-process elements. Our results show that for misalignments of 30° or less, r-process elements are robustly produced as long as neutrino luminosities are reasonably low (≲ 5 × 10 52 erg s -1 ). For a more extreme misalignment of 45°, we find the production of r-process elements beyond the second peak significantly reduced. We conclude that robust r-process nucleosynthesis in magnetorotational supernovae requires a progenitor stellar core with a large poloidal magnetic field component that is at least moderately (within ~30°) aligned with the rotation axis.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Automated setup for magnetic hysteresis characterization based on a voltage controlled current source with 500 kHz full power bandwidth and 10 A peak-to-peak current

This paper describes the design of a system for the characterization of magnetic hysteresis behavior in soft ferrite magnetic cores. The proposed setup can test magnetic materials exciting them with controlled arbitrary magnetic field waveforms, including the capability of providing a DC bias, in a frequency bandwidth up to 500 kHz, with voltages up to 32 V peak-to-peak, and currents up to 10 A peak-to-peak. In order to have an accurate control of the magnetic field waveform, the system is based on a voltage controlled current source. The electronic design is described focusing on closed loop feedback stabilization and passive components choice. The system has real-time hysteretic loop acquisition and visualization. The comparisons between measured hysteresis loops of sample magnetic materials and datasheet available ones are shown. Results showing frequency and thermal behavior of the hysteresis of a test sample prove the system capabilities. Moreover, the B-H loops obtained with a multiple waveforms excitation signal, including DC bias, are reported. The proposal is a low-cost and replicable solution for hysteresis characterization of magnetic materials used in power electronics.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Self-Powering High Frequency Modulated SiC Power MOSFET Isolated Gate Driver

A novel implementation of an isolated gate driver for power switches is proposed in this study. The driver is bespoke designed for SiC power mosfet s. The proposal achieves the main driver characteristics—isolation capability, gate switching command, and power transfer to the secondary side by using a unique magnetic transformer. The resulting simple circuitry enables the integration of the driver into the power cell, achieving theoretical higher power density values of the final system. The principle of operation of the driver is described in detail. The original pulsewidth modulation signal is modulated with a pure ac square waveform under a two-level modulation scheme, that guarantees no saturation of the magnetic core. Here, the signal is then magnetically coupled to the secondary side, where it is rectified and reconstructed to effectively drive the target device. In addition, the steps needed to provide a suitable design taking into account the parameters of the target power switch are also detailed. The resulting driver is characterized and a prototype of the driver is built and tested. The main results of the driver performance on a SiC mosfet -based prototype are presented. Based on the analysis of these results, this study experimentally demonstrates the feasibility of the proposal.

25 ENERGY STORAGE↗
DOE OSTI2025

MLSPICE: Machine Learning based SPICE Modeling Platform for Power Magnetics

Electrical power converters are critical to a wide range of applications ranging from renewable integration to transportation electrification, and can be a key factor determining the size, weight, and efficiency of energy conversion systems. Magnetic components are typically the largest and least efficient components in power electronics. While there have been major strides in the modeling and analysis of power semiconductor devices and circuit simulations, the necessary advances in the design of power magnetics have lagged. In this project, we have transformed the modeling and design of power magnetics with machine learning enabled methods and catalyze simultaneous disruptive improvements for ML-based power electronics design tools. A fully automated open-source machine learning based magnetics modeling platform – the MagNet project - with innovations in full stack have been developed to greatly accelerate the design process and provide new insights to magnetic material and geometry design. The ARPA-E funded MagNet platform contains three major building blocks: 1) a ML-Integrated Data Acquisition System (MIDAS): a highly automated data acquisition testbed which is capable of measuring a large number of magnetic cores with a wide range of electrical circuit excitations; 2) a ML-integrated Core Loss Model (MICLM): a machine-learning trained modeling method for modeling the core loss and saturation effects of magnetic materials for arbitrary excitation waveforms; 3) ML-guided Magnetics SPICE Simulation Tool (PMSPICE): a fully integrated CAD tool which can simulate the magnetics in SPICE. It can help the designers to quickly model the linear and non-linear characteristics of magnetic components and evaluate their behavior in SPICE simulations. The developed MagNet system has fully demonstrated the proposed performance target and has been open sourced to the entire power electronics community to advance the modeling and design of power magnetics from many different angles.

36 MATERIALS SCIENCE↗
NASA NTRS1988

A review of Magnetic Suspension and Balance Systems

This paper traces the development of Magnetic Suspension and Balance Systems (MSBSs) for use in wind tunnels. The expression MSBS implies a system that can both suspend a model and also measure the forces and moments acting on the model. This avoids the need for any mechanical support of the model. An MSBS uses electromagnets located outside the test section walls to create magnetic fields inside the test section. Measurement of the electrical current flowing in each of the electromagnets can be used to determine the forces and moments acting on the suspended model. An MSBS is capable of supporting a model with an internal magnetized core subject to gravity, aerodynamic, and inertial loads. The model must have a core made of either a permanent magnet, magnetized soft iron, or a solenoid. The position of the suspended body is inherently unstable. A closed-loop control system which includes a position sensing system has to control the position of the body by controlling the applied magnetic fields. This paper includes a discussion of all the known MSBSs and the outlook for larger systems.

Boyden, Richmond P.↗
NASA NTRS1986

Further investigation into calibration techniques for a magnetic suspension and balance system

Calibrations performed on three different magnetic cores for wind tunnel models suspended in the Southampton University Magnetic Suspension and Balance System (SUMSBS) are detailed. The first core investigated was the Southampton University pilot Superconducting Solenoid model, first flown in July 1983. Static calibrations of lift force, drag force and pitching moment, together with lift force and pitching moment calibrations determined by the dynamic method are detailed in this report. Other types of core investigated in a similar manner were conventional permanent magnets, Alnico and samarium-cobalt. All static calibrations gave a linear dependence of force on electromagnet current as expected. Dynamic calibrations are faster to perform but are proving to be not as easily analyzed as static calibrations. There are still some effects to be explained but dynamic lift calibration results were obtained agreeing to within 2 percent of the static calibration value.

Eskins, J.↗