Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “MAGNETIC COMPRESSION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Solar Wind Turbulence from 1 to 45 au. III. Anisotropy of Magnetic Fluctuations in the Inertial Range Using Voyager and ACE Observations

We examine both Voyager and Advanced Composition Explorer magnetic field measurements at frequencies that characterize the inertial range and evaluate the anisotropy of the fluctuations as they relate to both the compressive component and underlying wavevector anisotropy of the turbulence. The magnetic fluctuation anisotropy as it relates to the compressive component is directly dependent upon both the plasma beta of the thermal proton component and the ratio of magnetic fluctuation magnitude to the strength of the mean magnetic field. This has been seen before at 1 au. The magnetic fluctuation anisotropy in the plane perpendicular to the mean magnetic field, which is a measure of the anisotropy of the underlying wavevector distribution, should depend on the angle between the mean magnetic field and the radial direction and should be confined to values between one and the index of the power spectrum, which is typically 5/3. Our results show that the average of this anisotropy exceeds the value of the spectral index and is out of bounds with the theory. Although the results are suggestive of past analyses, we find that spherical expansion of the turbulence may offer at least a partial explanation of the apparent amplification of this measured anisotropy.

heliosphere↗
DOE OSTI2021

A Platform-Independent X-ray Diffraction Diagnostic for Phase Transition Kinetics in Traditional and Synthetic Microstructure Materials (LDRD Project 213088 Final Report)

Pulsed-power generators using the magnetic loading technique are able to produce well-controlled continuous ramp compression of condensed matter for high-pressure equation-of-state studies. X-ray diffraction (XRD) data from dynamically compressed samples provide direct measurements of the elastic compression of the crystal lattice, onset of plastic flow, strength-strain rate dependence, structural phase transitions, and density of crystal defects such as dislocations. Here, we present a cost effective, compact X-ray source for XRD measurements on pulsed-power-driven ramp-loaded samples. This combination of magnetically-driven ramp compression of materials with single, short-pulse XRD diagnostic will be a powerful capability for the dynamic materials community. The success in fielding this new XRD diagnostic dramatically improves our predictive capability and understanding of rate-dependent behavior at or near phase transition. As Sandia plans the next-generation pulse-power driver platform, a key element needed to deliver new state-of-the-art experiments will be having the necessary diagnostic tools to probe new regimes and phenomena. These diagnostics need to be as versatile, compact, and portable as they are powerful. The development of a platform-independent XRD diagnostic gives Sandia researchers a new window to study the microstructure and phase dynamics of materials under load. This project has paved the way for phase transition research in a variety of materials with mission interest.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Increasing plasma parameters using sheared flow stabilization of a Z-pinch

The ZaP and ZaP-HD Flow Z-pinch experiments at the University of Washington have successfully demonstrated that sheared plasma flows can be used as a stabilization mechanism over a range of parameters that has not previously been accessible to long-lived Z-pinch configurations. The stabilization is effective even when the plasma column is compressed to small radii, producing predicted increases in magnetic field and electron temperature. The flow shear value, extent, and duration are shown to be consistent with theoretical models of the plasma viscosity, which places a design constraint on the maximum axial length of a sheared flow stabilized Z-pinch. Measurements of the magnetic field topology indicate simultaneous azimuthal symmetry and axial uniformity along the entire 100 cm length of the Z-pinch plasma. Separate control of plasma acceleration and compression has increased the accessible plasma parameters and has generated stable plasmas with radii of 0.3 cm, as measured with a high resolution digital holographic interferometer. Compressing the plasma with higher pinch currents has produced high magnetic fields (8.5 T) and electron temperatures (1 keV) with an electron density of 2×10 17 cm -3 , while maintaining plasma stability for many Alfvén times (approximately 50 μs). Thus, the results suggest that sheared flow stabilization can be applied to extend Z-pinch plasma parameters to high energy densities.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Structural and electronic evolution of Cr[subscript 2]O[subscript 3] on compression to 55 GPa

Synchrotron single-crystal x-ray diffraction experiments have been performed on corundum-type Cr{sub 2}O{sub 3} up to a pressure of 55 GPa in Ne and He pressure transmitting media. Diffraction experiments were complemented by measurements of optical absorption spectra with single crystal samples up to 60 GPa. Results of the diffraction data analysis rule out the earlier reported monoclinic distortion at 15-30 GPa, but indicate evidence of two discontinuous transitions of electronic or magnetic nature, most likely associated with a change in magnetic ordering and charge transfer. The compression mechanism established from single crystal refinements indicates much smaller distortion of the Cr{sup 3+} coordination environment than was previously assumed.

Dera, Przemyslaw↗
DOE OSTI2016

Effect of sintering treatment on structural and magnetic properties of Ni{sub 0.5}Co{sub 0.5}Fe{sub 2}O{sub 4} ferrites

Two sets of Ni{sub 0.5}Co{sub 0.5}Fe{sub 2}O{sub 4} ferrites were synthesized using sol-gel method. Both the samples were heat treated at different temperatures. The effect of sintering treatment analyzed on structural and magnetic properties. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used for structural analysis. Alternating gradient magnetometer (AGM) is used for magnetic measurements. In structural analysis, grains size is calculated using Debye - Scherrer’s formula and Williamson-Hall (W-H) plot. From both the techniques, grain size is found nearly same and increased in size with increase sintering temperature. Increased particle size is confirmed from SEM micrographs. Strain value is calculated from intercept of W-H plot. In both the samples, compressive strain in nature is found. Magnetic properties were also varying under different heat treatment. The change in magnetic properties with change in structural change at different sintering treatment is discussed in this report.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Electron and Proton Heating in Transrelativistic Magnetic Reconnection

Hot collisionless accretion flows, such as the one in Sgr A* at our Galactic center, provide a unique setting for the investigation of magnetic reconnection. Here protons are nonrelativistic, while electrons can be ultrarelativistic. By means of 2D particle-in-cell simulations, we investigate electron and proton heating in the outflows of transrelativistic reconnection (i.e., ${\sigma }_{w}\sim 0.1\mbox{--}1$, where the magnetization ${\sigma }_{w}$ is the ratio of magnetic energy density to enthalpy density). For both electrons and protons, we find that heating at high ${\beta }_{{\rm{i}}}$ (here ${\beta }_{{\rm{i}}}$ is the ratio of proton thermal pressure to magnetic pressure) is dominated by adiabatic compression ("adiabatic heating"), while at low ${\beta }_{{\rm{i}}}$ it is accompanied by a genuine increase in entropy ("irreversible heating"). For our fiducial ${\sigma }_{w}=0.1$, the irreversible heating efficiency at ${\beta }_{{\rm{i}}}\lesssim 1$ is nearly independent of the electron-to-proton temperature ratio ${T}_{{\rm{e}}}/{T}_{{\rm{i}}}$ (which we vary from 0.1 up to 1), and it asymptotes to $\sim 2 \% $ of the inflowing magnetic energy in the low-${\beta }_{{\rm{i}}}$ limit. Protons are heated more efficiently than electrons at low and moderate ${\beta }_{{\rm{i}}}$ (by a factor of ~7), whereas the electron and proton heating efficiencies become comparable at ${\beta }_{{\rm{i}}}\sim 2$ if ${T}_{{\rm{e}}}/{T}_{{\rm{i}}}=1$, when both species start already relativistically hot. We find comparable heating efficiencies between the two species also in the limit of relativistic reconnection (${\sigma }_{w}\gtrsim 1$). Finally, our results have important implications for the two-temperature nature of collisionless accretion flows and may provide the subgrid physics needed in general relativistic MHD simulations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

The Operating Principle of a Fully Solid State Active Magnetic Regenerator

As an alternative refrigeration technology, magnetocaloric refrigeration has the potential to be safer, quieter, more efficient, and more environmentally friendly than the conventional vapor compression refrigeration technology. Most of the reported active magnetic regenerator (AMR) systems that operate based on the magnetocaloric effect use heat transfer fluid to exchange heat, which results in complicated mechanical subsystems and components such as rotating valves and hydraulic pumps. This paper presents an operating principle of a fully solid state AMR, in which an alternative mechanism for heat transfer between the AMR and the heat source/sink is proposed. The operating principle of the fully solid state AMR is based on moving rods/sheets (e.g. copper, brass, iron or aluminum), which are employed to replace the heat transfer fluid. Such fully solid state AMR would provide a significantly higher heat transfer rate than a conventional AMR because the conductivity of moving solid rods/plates is high and it enables the increase in the machine operating frequency hence the cooling capacity. The details of operating principle are presented and discussed here. One of the key enabling features for this technology is the contact between the moving rods/sheets and magnetocaloric material, and heat exchange mechanism at the heat source/sink. This paper provides an overview of the design for a fully solid state magnetocaloric refrigeration system along with guidelines for their optimal design.

Abdelaziz, Omar↗
DOE OSTI2015

STRONG SOLAR WIND DYNAMIC PRESSURE PULSES: INTERPLANETARY SOURCES AND THEIR IMPACTS ON GEOSYNCHRONOUS MAGNETIC FIELDS

In this investigation, we first present a statistical result of the interplanetary sources of very strong solar wind dynamic pressure pulses (DPPs) detected by WIND during solar cycle 23. It is found that the vast majority of strong DPPs reside within solar wind disturbances. Although the variabilities of geosynchronous magnetic fields (GMFs) due to the impact of positive DPPs have been well established, there appears to be no systematic investigations on the response of GMFs to negative DPPs. Here, we study both the decompression effects of very strong negative DPPs and the compression from strong positive DPPs on GMFs at different magnetic local time sectors. In response to the decompression of strong negative DPPs, GMFs on the dayside near dawn and near dusk on the nightside, are generally depressed. But near the midnight region, the responses of GMF are very diverse, being either positive or negative. For part of the events when GOES is located at the midnight sector, the GMF is found to abnormally increase as the result of magnetospheric decompression caused by negative DPPs. It is known that under certain conditions magnetic depression of nightside GMFs can be caused by the impact of positive DPPs. Here, we find that a stronger pressure enhancement may have a higher probability of producing the exceptional depression of GMF at the midnight region. Statistically, both the decompression effect of strong negative DPPs and the compression effect of strong positive DPPs depend on the magnetic local time, which are stronger at the noon sector.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Study of Implosion of Combined Nested Arrays

New experimental data on the implosion of plasma of nested kapron−tungsten arrays are obtained at the Angara-5-1 facility. The mode of plasma implosion is implemented in which a shock wave region forms in the space between the inner and outer arrays where a transition from the super-Alfvénic (V{sub r} > V{sub A}) to sub-Alfvénic (V{sub r} < V{sub A}) plasma flow takes place. Specific features of the formation and decay of the shock region are studied using laser shadow imaging and X-ray frame photography. The plasma density in the transition region is estimated. By comparing the experimental data with the results of simulations of quasi-steady implosion of a nested array with allowance for extended plasma production, the physical conditions are determined at which the implosion mode with the formation the shock region takes place. Stable compression of the plasma of the inner array was observed during the implosion of combined nested arrays with a fiber outer array and tungsten inner array. Suppression of magnetic Rayleigh-Taylor instability during the compression of the inner array plasma results in the formation of a compact radiating Z-pinch and generation of a soft X-ray pulse with a peak power of 4 TW and duration of about 5 ns.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Controlling Magnetism of F-Adsorbed BN Nanosheets by Applying Isotropic Strain

Magnetic properties of the h-BN monolayer with nonmetal atoms adsorbed are studied by the first-principle methods. Different dopants (C, Cl, F, and O) and adsorption sites are considered. On one hand, magnetic behavior is observed in two-dimensional (2D) BN system with C, Cl, and O atoms and nonmagnetic state is shown in the F-adsorbed system. On the other hand, the F-adsorbed system shows a more stable formed structure among all the systems. Thus, we study the magnetic properties in F-adsorbed 2D-BN system under the applied tensile and compressive strain. Interestingly, as the strain increases, a maximum magnetic moment of 1.12 μ{sub B} is observed, which originates from the p-p hybridization among F, B, and N atoms. Our results suggest some potential applications of the F-adsorbed BN nanosheet.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Tuning magnetic coercivity with external pressure in iron-rhenium based ferrimagnetic double perovskites

We studied the effect of physical pressure on the electronic and magnetic properties of ferrimagnetic double perovskites A 2 FeReO 6 (A = Ca, Ba) using Re L 2,3 edge x-ray absorption spectroscopy and powder diffraction measurements. Volume compression is shown to dramatically increase the magnetic coercivity (H c ) in polycrystalline samples of both compounds with ΔH c /ΔV similar to 150-200 Oe/Å 3 . A nearly eight-fold increase in H c , from 0.2 to 1.55 T, is obtained in Ba 2 FeReO 6 at P = 29 GPa. While no signs of structural phase transitions are seen in either sample to similar to 30 GPa, the structural data points to a pressure-driven increase in tetragonal distortion of ReO 6 octahedra. A sizable but pressure-independent Re orbital-to-spin magnetic moment ratio is observed, pointing to the critical role of spin-orbit interactions at Re sites. We present a J(eff) description of the electronic structure that combines effects of crystal field and spin-orbit coupling on the Re 5d 2 orbitals and use this description to provide insight into the pressure-induced enhancement of magnetic anisotropy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effect of MWCNT Content on the Structure and Properties of Spark Plasma-Sintered Iron-MWCNT Composites Synthesized by High-Energy Ball Milling

The effect of multiwall carbon nanotube (MWCNT) content on the physical and mechanical properties of Fe-MWCNT composites has been studied. High-energy ball milling (HEBM) is employed to produce the composite powder; following this, spark plasma sintering (SPS) process has been adopted for powder consolidation. The composite powder and the sintered products were subjected to structural characterization by XRD. Microstructural studies were carried out by optical, field-emission scanning and high-resolution transmission electron microscopy. While Fourier transform infrared spectroscopic study of composites was done to understand the bonding characteristics, Raman spectroscopy was employed to assess the structural damage of MWCNT after HEBM. The effects of processing on the behavior of C-C, C-O and Fe-O bonds are studied by x-ray photoelectron spectroscopy. Microhardness and compressive strength of composites are also determined. Finally, magnetic and electrical properties of the composites were characterized. It was observed that optimized ball milling conditions help to preserve the structural identity of MWCNT. Consolidation by SPS insured good interfacial bonding. The microhardness and compression strength are significantly improved in MWCNT-reinforced iron matrix composite. MWCNT has appreciably improved the electrical conductivity of the composites. Tethering of MWCNT by iron oxide has led to appreciable improvement in saturation magnetization till 3 wt.% MWCNT.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Measurements of the Strain Dependence of Critical Current of Commercial REBCO Tapes at 15 T Between 4.2 and 40 K for High Field Magnets

Interest for high magnetic fields (>16 T) for applications in high energy physics (HEP) and fusion machines, requires the development of high current cables capable to withstand the large forces, mechanical and electromagnetic, experienced during manufacturing and operations. The critical current (I c ) of REBCO tapes depends on strain, magnetic fields, and operational temperatures. Understanding how these parameters affect the I c of the conductor will be critical to develop robust high-current REBCO cables. However, there are limited reports on the strain dependence of I c , in particular at high fields and elevated temperatures relevant for future high-field compact fusion reactor magnets. We present here I c of commercial REBCO tapes measured as a function of compressive and tensile strain (between -0.6% and +0.65%) at high magnetic fields (12 and 15 T) and different temperatures (within 4.2-40 K). Results at 4.2 and 20 K showed less than 5% reduction in the normalized I c at high strain, while a stronger strain dependence was observed at 40 K. Samples tested at 12 T and 4.2 K showed similar strain dependence as 15 T and 4.2 K. In all tested conditions, the tape experienced reversible I c reduction in both tension and compression. Finite element analysis was used to predict the residual thermal strain accumulated in the REBCO layer prior of testing to account for the effect of the cooldown. A method was also developed to account for the current sharing observed between the sample and the sample holder during the ramp of the current. Our results provide useful input for the development of high-field fusion and HEP magnets using REBCO conductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Modeling the one-dimensional imager of neutrons (ODIN) for neutron response functions at the Sandia Z facility

The one-dimensional imager of neutrons (ODIN) at the Sandia Z facility consists of a 10-cm block of tungsten with rolled edges, creating a slit imager with slit widths of either 250, 500, or 750 μm. Designed with a 1-m neutron imaging line of sight, we achieve about 4:1 magnification and 500-μm axial spatial resolution. The baseline inertial confinement fusion concept at Sandia is magnetized liner inertial fusion, which nominally creates a 1-cm line source of neutrons. ODIN was designed to determine the size, shape, and location of the neutron producing region, furthering the understanding of compression quality along the cylindrical axis of magnetized liner implosions. Challenges include discriminating neutrons from hard x-rays and gammas with adequate signal-to-noise in the 2 × 10 12 deuterium-deuterium (DD) neutron yield range, as well as understanding the point spread function of the imager to various imaging detectors (namely, CR-39). Modeling efforts were conducted with MCNP6.1 to determine neutron response functions for varying configurations in a clean DD neutron environment (without x-rays or gammas). Configuration alterations that will be shown include rolled-edge slit orientation and slit width, affecting the resolution and response function. The experiment to determine CR-39 neutron sensitivity, with and without a high density polyethylene (n, p) converter, an edge spread function, and resolution will be discussed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Development of a cryogenically cooled platform for the Magnetized Liner Inertial Fusion (MagLIF) Program [Development of a cryogenically-cooled platform for the Magnetized Liner Inertial Fusion (MagLIF) Concept]

A cryogenically cooled hardware platform has been developed and commissioned on the Z Facility at Sandia National Laboratories in support of the Magnetized Liner Inertial Fusion (MagLIF) Program. MagLIF is a magneto-inertial fusion concept that employs a magnetically imploded metallic tube (liner) to compress and inertially confine premagnetized and preheated fusion fuel. The fuel is preheated using a ~2 kJ laser that must pass through a ~1.5-3.5-μm-thick polyimide “window” at the target’s laser entrance hole (LEH). As the terawatt-class laser interacts with the dense window, laser plasma instabilities (LPIs) can develop, which reduce the preheat energy delivered to the fuel, initiate fuel contamination, and degrade target performance. Cryogenically cooled targets increase the parameter space accessible to MagLIF target designs by allowing nearly 10 times thinner windows to be used for any accessible gas density. Thinner LEH windows reduce the deleterious effects of difficult to model LPIs. The Z Facility’s cryogenic infrastructure has been significantly altered to enable compatibility with the premagnetization and fuel preheat stages of MagLIF. The MagLIF cryostat brings the liquid helium coolant directly to the target via an electrically resistive conduit. This design maximizes cooling power while allowing rapid diffusion of the axial magnetic field supplied by external Helmholtz-like coils. A variety of techniques have been developed to mitigate the accumulation of ice from vacuum chamber contaminants on the cooled LEH window, as even a few hundred nanometers of ice would impact laser energy coupling to the fuel region. Here, the MagLIF cryostat has demonstrated compatibility with the premagnetization and preheat stages of MagLIF and the ability to cool targets to liquid deuterium temperatures in approximately 5 min.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

High-resolution hybrid simulations of kinetic plasma turbulence at proton scales

We investigate properties of plasma turbulence from magnetohydrodynamic (MHD) to sub-ion scales by means of two-dimensional, high-resolution hybrid particle-in-cell simulations. We impose an initial ambient magnetic field perpendicular to the simulation box, and we add a spectrum of large-scale magnetic and kinetic fluctuations with energy equipartition and vanishing correlation. Once the turbulence is fully developed, we observe an MHD inertial range, where the spectra of the perpendicular magnetic field and the perpendicular proton bulk velocity fluctuations exhibit power-law scaling with spectral indices of −5/3 and −3/2, respectively. This behavior is extended over a full decade in wavevectors and is very stable in time. A transition is observed around proton scales. At sub-ion scales, both spectra steepen, with the former still following a power law with a spectral index of ∼−3. A −2.8 slope is observed in the density and parallel magnetic fluctuations, highlighting the presence of compressive effects at kinetic scales. The spectrum of the perpendicular electric fluctuations follows that of the proton bulk velocity at MHD scales, and flattens at small scales. All these features, which we carefully tested against variations of many parameters, are in good agreement with solar wind observations. The turbulent cascade leads to on overall proton energization with similar heating rates in the parallel and perpendicular directions. While the parallel proton heating is found to be independent on the resistivity, the number of particles per cell, and the resolution employed, the perpendicular proton temperature strongly depends on these parameters.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Bursty magnetic reconnection at the Earth's magnetopause triggered by high-speed jets

The impact of high-speed jets—dynamic pressure enhancements in the magnetosheath—on the Earth's magnetopause has been observed to trigger local magnetic reconnection. We perform a three-dimensional hybrid simulation to study the magnetosheath and magnetopause under turbulent conditions using a quasi-radial southward interplanetary magnetic field (IMF). In contrast to quasi-steady reconnection with a strong southward IMF, we show that after the impact of a jet on the magnetopause, the magnetopause moves inward, the current sheet is compressed and intensified and signatures of local magnetic reconnection are observed, showing similarities to spacecraft measurements.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

WEIBEL INSTABILITY DRIVEN BY SPATIALLY ANISOTROPIC DENSITY STRUCTURES

Observations of afterglows of gamma-ray bursts (GRBs) suggest that post-shock magnetic fields are strongly amplified to about 100 times the shock-compressed value. The Weibel instability appears to play an important role in generating the magnetic field. However, recent simulations of collisionless shocks in homogeneous plasmas show that the magnetic field generated by the Weibel instability rapidly decays. There must be some density fluctuations in interstellar and circumstellar media. The density fluctuations are anisotropically compressed in the downstream region of relativistic shocks. In this paper, we study the Weibel instability in electron–positron plasmas with spatially anisotropic density distributions by means of two-dimensional particle-in-cell simulations. We find that large magnetic fields are maintained for a longer time by the Weibel instability driven by spatially anisotropic density structure. Particles anisotropically escape from the high density region, so that a temperature anisotropy is generated and the Weibel instability becomes unstable. Our simulation results suggest that the Weibel instability driven by an anisotropic density structure can generate sufficiently large magnetic fields and they can cover sufficiently large regions to explain the afterglow emission of GRBs.

79 ASTRONOMY AND ASTROPHYSICS↗