Search NASA⌕ Search

SEARCH · Search NASA

Results for “magnetic alignment”

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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Parallel diffusion operator for magnetized plasmas with improved spectral fidelity

Diffusive transport processes in magnetized plasmas are highly anisotropic, with fast parallel transport along the magnetic field lines sometimes faster than perpendicular transport by orders of magnitude. This constitutes a major challenge for describing non-grid-aligned magnetic structures in Eulerian (grid-based) simulations. Here, the present paper describes and validates a new method for parallel diffusion in magnetized plasmas based on the anti-symmetry representation [Halpern and Waltz, Phys. Plasmas 25, 060703 (2018)]. In the anti-symmetry formalism, diffusion manifests as a flow operator involving the logarithmic derivative of the transported quantity. Qualitative plane wave analysis shows that the new operator naturally yields better discrete spectral resolution compared to its conventional counterpart. Numerical simulations comparing the new method against existing finite difference methods are carried out, showing significant improvement. In particular, we find that combining anti-symmetry with finite differences in diagonally staggered grids essentially eliminates the so-called “artificial numerical diffusion” that affects conventional finite difference and finite volume methods.

Anisotropic diffusion↗
NASA NTRS1988

Effect of vertical magnetic field on convection and segregation in vertical Bridgman crystal growth

A previous finite-element analysis of vertical Bridgman growth for dilute and nondilute alloys is extended to include the effect of a vertically-aligned magnetic field in the limit of zero magnetic Reynolds number. Calculations are presented for growth of a dilute gallium-germanium alloy in a vertically stabilized Bridgman-Stockbarger system and in a furnace with a uniform temperature gradient imposed along the ampoule. Steady cellular convection driven by radial temperature gradients causes good axial and radial mixing in both systems without a magnetic field. A weak magnetic field decreases the intensity of convection and the effectiveness of solute mixing. The radial nonuniformity is greatest for an intermediate field strength. Stronger fields suppress flow recirculation completely, and lead to uniform solute segregation across the crystal and to diffusion-controlled axial segregation.

Kim, Do Hyun↗
NASA NTRS1967

Improved ion sources

Ion sources with magnetically aligned electron beam and compatibility with quadrupole mass spectrometer for planetary atmospheric analysis

ELECTRON BEAM↗
DOE OSTI2025

Thermal Performance of a Conduction-Cooled CCT Dipole ReBCO Magnet: Several Cycles of Cool-Down and Thermal Gradient Measurements

Here, this paper presents experimental results from conduction-cooled thermal testing of a ReBCO canted cosine theta (CCT) magnet (C2), originally designed and fabricated at LBNL using CORC cables. While the performance of the coil under liquid helium and nitrogen environments has been previously established, this study explores its behavior under conduction cooling using a large test cryostat at The Ohio State University. The magnet, measuring 613 mm in length and weighing ∼75 kg, consists of four helical layers wound with ReBCO-based CORC wire and was thermally anchored to a copper cold ring supported by a G-10 strongback. Cooling was provided by two Sumitomo RDK-415D cryocoolers, offering a combined 3 W at 4.2 K and 150 W at 77 K. Multiple thermal cycles were performed, with cooldown durations of up to 45 hours. Final base temperatures of approximately 10.8 K (at the coil edge) and 12.0 K (at the coil center) were achieved, with an axial temperature difference of approximately 1.2 K. The warm-up period extended over approximately 24.6 hours. Voltage measurements from all four layers were recorded during cooldown and warmup. The system demonstrated stable cooldown performance, repeatable gradients, and good thermal anchoring. These results support the feasibility of conduction cooling in large-scale HTS magnets, aligning with broader goals for “green” cryogen-free accelerator technologies and paving the way for more sustainable, scalable, and energy-efficient high-field magnet systems in next-generation particle accelerators.

Canted cosine theta magnets↗
DOE OSTI2023

Production of permanent magnets using electrophoretic deposition

In one embodiment, a magnet includes a plurality of layers, each layer having a microstructure of sintered particles. The particles in at least one of the layers are characterized as having preferentially aligned magnetic orientations in a first direction.

McCall, Scott K.↗
NASA NTRS2020

SOFIA/HAWC plus Traces the Magnetic Fields in NGC 1068

We report the first detection of galactic spiral structure by means of thermal emission from magnetically aligned dust grains. Our 89μm polarimetric imaging of NGC 1068 with the High-resolution Airborne Wideband Camera/Polarimeter(HAWC+)on NASAs Stratospheric Observatory for Infrared Astronomy(SOFIA)also sheds light on magnetic field structure in the vicinity of the galaxyʼs inner-bar and active galactic nucleus(AGN).We find correlations between the 89μm magnetic field vectors and other tracers of spiral arms, and a symmetric polarization pattern as a function of the azimuthal angle arising from the projection and inclination of the disk field component in the plane of the sky. The observations can befit with a logarithmic spiral model with pitch angle of-+16.92.82.7and a disk inclination of 48°±2°. We infer that the bulk of the interstellar medium from which the polarized dust emission originates is threaded by a magnetic field that closely follows the spiral arms. Inside the central starburst disk(<1.6 kpc), the degree of polarization is found to be lower than for far-infrared sources in the Milky Way, and has minima at the locations of most intense star formation near the outer ends of the inner-bar. Inside the starburst ring, the field direction deviates from the model, becoming more radial along the leading edges of the inner-bar. The polarized flux and dust temperature peak∼3′′–6′′NE of the AGN at the location of a bow shock between the AGN outflow and the surrounding interstellar medium, but the AGN itself is weakly polarized(<1%)at both 53 and 89μm.

Active galactic nuclei↗
NASA NTRS1999

3D-Stereoscopic Analysis of Solar Active Region Loops: SoHo/EIT Observations at Temperatures of 1.5-2.5 MK - 2

In this paper we study the three-dimensional (3D) structure of hot (T(sub e) approximately equals 1.5 - 2.5 MK) loops in solar active region NOAA 7986, observed on 1996 August 30 with the Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SoHO). This complements a first study on cooler (T(sub e) approximately equals 1.0 - 1.5 MK) loops of the same active region, using the same method of Dynamic Stereoscopy to reconstruct the 3D geometry. We reconstruct the 3D-coordinates x(s), y(s), z(s), the density n(sub e)(s), and temperature profile T(sub e)(s) of 35 individual loop segments (as function of the loop coordinate s) using EIT 195 A and 284 A images. The major findings are: (1) All loops are found to be in hydrostatic equilibrium, in the entire temperature regime of T(sub e) = 1.0 - 2.5 MK; (2) The analyzed loops have a height of 2-3 scale heights, and thus only segments extending over about one vertical scale height have sufficient emission measure contrast for detection; (3) The temperature gradient over the lowest scale height is of order dT/ds is approximately 1 - 4 K/km; (4) The radiative loss rate is found to exceed the conductive loss rate by about two orders or magnitude, making thermal conduction negligible to explain the temperature structure of the loops; (5) A steady-state can only be achieved when the heating rate E(sub H) matches the radiative loss rate in hydrostatic equilibrium, requiring a heat deposition length lambda(sub H) of the half density scale height lambda, predicting a scaling law with the loop base pressure, EH varies as p(sub 0 exp 2). This favors coronal heating mechanisms that operate near the loop footpoints; (6) We find a reciprocal correlation between the loop pressure p(sub 0) and loop length L, i.e. p(sub 0) varies as 1/L, implying a scaling law of the steady-state requirement with loop length, i.e. E(sub H ) varies as 1/L(exp 2). The heating rate shows no correlation with the loop-aligned magnetic field component B(sub z) at the footpoints, but is correlated with the azimuthal field B(sub phi) = Bz(RDelta Phi/L) of a twisted loop, and is thus consistent with heating mechanisms based on field-aligned currents.

Aschwanden, Markus J.↗
DOE OSTI2026

Spin reorientations in structurally metastable, disordered, and hexagonal Cr 7 ⁢Te 8

Vapor deposited two-dimensional Cr 7 ⁢Te 8 displays unusual temperature dependent Hall effect properties, including a room-temperature anomalous Hall effect, sign reversals of the Hall resistivity on cooling, and a peak in the Hall resistivity at low temperatures. The two-dimensional Cr 7⁢ Te 8 heterostructures that form the basis of these measurements are hexagonal in structure. We study the magnetic and structural properties of bulk Cr 7 ⁢Te 8 synthesized by quenching from 1000⁢°C with the goal of relating the magnetic, structural, and electronic properties. This quenched phase is metastable, hexagonal, and displays different magnetic properties from the slow-cooled and more thermodynamically stable monoclinic phase. High-resolution x-ray diffraction of the quenched hexagonal phase finds a first-order transition to a lower symmetry monoclinic phase on heating above ∼550 K. Magnetic susceptibility measurements of the quenched hexagonal phase reveal ferromagnetic ordering above room temperature, along with the two distinct transitions at ∼220 K and ∼70 K. Through neutron diffraction studies, we find the ∼220 K anomaly is a spin reorientation transition of the ferromagnetically aligned magnetic moments and the ∼70K feature represents a transition from a high-temperature ferromagnet to a low-temperature antiferromagnet. We suggest that these magnetic transitions are related to changes in the unit-cell dimensions and are connected to the temperature-dependent Hall resisitivity studied in two-dimensional heterostructures. This implies a link between structural, magnetic, and electronic properties in the “pseudo” two-dimensional chromium tellurides.

Chemical synthesis↗
NASA NTRS1993

Relativistic electron-positron beams in gamma-ray bursters

Beams of relativistic electrons and/or positrons leaving the surface of a strongly magnetized neutron star may give rise to gamma-ray bursts. The beams could be accelerated by strong, magnetically aligned electric fields that are produced by oscillations of the stellar surface. Here we investigate the particle acceleration in these electric fields, the resulting electron-positron pair cascade, and the gamma-ray emission. We find that beams of electrons and positrons moving parallel to the magnetic field are generated, with a reported differential energy distribution. These beams produce the bulk of the gamma-ray burst radiation below about 1 MeV by the resonant Compton scattering of thermal photons emitted from the stellar surface. The escaping synchrotron radiation from the cascade dominates the radiation spectrum above about 1 MeV.

Smith, I. A.↗
DOE OSTI2024

Nuclear magnetic resonance investigation of superconducting and normal state Nb 3 Sn

The superconductor Nb3Sn has important applications for construction of very high-field superconducting magnets. In this work we investigate its microscopic electronic structure with 93 Nb nuclear magnetic resonance (NMR). The high-quality Nb 3 Sn powder sample was studied in both 3.2 T and 7 T magnetic fields in the temperature range from 4 K to 300 K. From measurement of the spectrum and its theoretical analysis, we find evidence for anisotropy despite its cubic crystal structure. Magnetic alignment of the powder grains in the superconducting state was also observed. The Knight shift and spin-lattice relaxation rate, T 1 -1 , were measured and the latter compared with BCS theory for the energy gap Δ(0) = 2.7 ± 0.3k B T c at 3.2 T and Δ(0) = 2.33 ± 0.07 k B T c at 7 T, indicating suppression of the order parameter by magnetic field.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2023

Extragalactic Magnetism with SOFIA (SALSA Legacy Program). V. First Results on the Magnetic Field Orientation of Galaxies

We present the analysis of the magnetic field ( B -field) structure of galaxies measured with far-infrared (FIR) and radio (3 and 6 cm) polarimetric observations. We use the first data release of the Survey of extragALactic magnetiSm with SOFIA of 14 nearby (<20 Mpc) galaxies with resolved (5"-18" ; 90 pc–1 kpc) imaging polarimetric observations using SOFIA/HAWC+ from 53 to 214 μm . We compute the magnetic pitch-angle (𝜓 B ) profiles as a function of the galactocentric radius. We introduce a new magnetic alignment parameter ( ζ ) to estimate the disordered-to-ordered ratio of spiral B -fields. We find FIR and radio wavelengths to not generally trace the same B -field morphology in galaxies. The 𝜓 B profiles tend to be more ordered across all galactocentric radii in radio ( ζ 6cm = 0.93 + 0.03) than in FIR ( ζ 154μm = 0.84 + 0.14). For spiral galaxies, FIR B -fields are 2%–75% more turbulent than the radio B -fields. For starburst galaxies, we find that FIR polarization is a better tracer of the B -fields along the galactic outflows than radio polarization. Our results suggest that the B -fields associated with dense, dusty, turbulent star-forming regions (those traced at FIR) are less ordered than warmer, less dense regions (those traced at radio) of the interstellar medium. The FIR B -fields seem to be more sensitive to the activity of the star-forming regions and molecular clouds within a vertical height of a few hundred parsecs in the disk of spiral galaxies than the radio B -fields.

magnetic field (B-field)↗
NASA NTRS2023

Extragalactic Magnetism with SOFIA (SALSA Legacy Program) - V. First Results on the Magnetic Field Orientation of Galaxies

We present the analysis of the magnetic field (B-field) structure of galaxies measured with far-infrared (FIR) and radio (3 and 6 cm) polarimetric observations. We use the first data release of the Survey of extragALactic magnetiSm with SOFIA (SALSA) of 14 nearby (< 20 Mpc) galaxies with resolved (5′′ − 18′′; 90 pc–1 kpc) imaging polarimetric observations using SOFIA/HAWC+ from 53 to 214 μm. We compute the magnetic pitch angle (Ψ B ) profiles as a function of the galactocentric radius. We introduce a new magnetic alignment parameter (ζ) to estimate the disordered-to-ordered ratio of spiral B -fields. We find FIR and radio wavelengths to not generally trace the same B -field morphology in galaxies. The Ψ B profiles tend to be more ordered across all galactocentric radii in radio (ζ 6cm = 0.93 ± 0.03) than in FIR (ζ 154μm = 0.84 ± 0.14). For spiral galaxies, FIR B-fields are 2−75% more turbulent than the radio B -fields. For starburst galaxies, we find that FIR polarization is a better tracer of the B -fields along the galactic outflows than radio polarization. Our results suggest that the B -fields associated with dense, dusty, turbulent star-forming regions, those traced at FIR, are less ordered than warmer, less-dense regions, those traced at radio, of the interstellar medium. The FIR B -fields seem to be more sensitive to the activity of the star-forming regions and molecular clouds within a vertical height of few hundred pc in the disk of spiral galaxies than the radio B -fields.

SALSA↗
DOE OSTI2023

Analysis of X-ray images and spectra (aXis2000): A toolkit for the analysis of X-ray spectromicroscopy data

Spectromicroscopy refers to analytical methods that combine imaging and spectroscopy to provide detailed, spatially resolved analytical information about a sample, such as the type and quantitative spatial distributions of chemical components, geometric or magnetic alignment information, crystal structure, etc. The analysis of X-ray images and spectra (aXis2000) software described in this work provides a set of routines within a single, integrated, graphical-oriented package to read, display, manipulate and analyze spectromicroscopy data, with particular focus on soft X-ray spectromicroscopy methods such as scanning transmission X-ray microscopy (STXM), X-ray photoemission electron microscopy (XPEEM), scanning photoelectron X-ray microscopy (SPEM) and transmission X-ray microscopy (TXM). Here, this free software is described and compared to other software that can provide similar or complementary capabilities. Examples of spectromicroscopic analyses using advanced features of aXis2000 are provided.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Deuteron off-resonance rotating frame relaxation for the characterization of slow motions in rotating and static solid-state proteins

Here, we demonstrate the feasibility of deuterium solid-state NMR off-resonance rotating frame relaxation measurements for studies of slow motions in biomolecular solids. The pulse sequence, which includes adiabatic pulses for magnetization alignment, is illustrated for static and magic-angle spinning conditions away from rotary resonances. We apply the measurements for three systems with selective deuterium labels at methyl groups: a) a model compound, Fluorenylmethyloxycarbonyl methionine-D 3 amino acid, for which the principles of the measurements and corresponding motional modeling based on rotameric interconversions are demonstrated; b) amyloid-β 1-40 fibrils labeled at a single alanine methyl group located in the disordered N-terminal domain. This system has been extensively studied in prior work and here serves as a test of the method for complex biological systems. The essential features of the dynamics consist of large-scale rearrangements of the disordered N-terminal domain and the conformational exchange between the free and bound forms of the domain, the latter one due to transient interactions with the structured core of the fibrils. and c) a 15-residue helical peptide which belongs to the predicted α-helical domain near the N-terminus of apolipoprotein B. The peptide is solvated with triolein and incorporates a selectively labeled leucine methyl groups. The method permits model refinement, indicating rotameric interconversions with a distribution of rate constants.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Cross-field and parallel dynamics of SOL filaments in TCV

Using recently installed scrape-off layer diagnostics on the tokamak à configuration variable, we characterise the poloidal and parallel properties of turbulent filaments. We access both attached and detached divertor conditions across a wide range of core densities (f G ϵ [0.09, 0.66]) in diverted L-mode plasma configurations. With a gas puff imaging (GPI) diagnostic at the outer midplane we observed filaments with a monotonic increase in radial velocity (from 390 m s –1 to 800 m s –1 ) and cross-field radii (from 8.5 mm to 13.4 mm) with increasing core density. Interpreting the filament behaviour in the context of the two-region model, we find that they populate the ideal-interchange regime (C i ) in discharges at very low densities, and the resistive X (RX)-point regime for all other discharges. The scaling of filament velocity versus size shows good agreement with this interpretation. These results are discussed and compared with previous probe-based measurements for similar conditions, which mostly placed filaments in TCV in the resistive ballooning (RB) regime. In addition, for the first time in TCV, the parallel filament extension is studied by magnetically aligning the GPI measurements at the outboard midplane with a reciprocating probe in the divertor. In agreement with the filaments being in the ideal-interchange and the RX-point regimes, they are found to extend beyond the X-point into the outer divertor leg.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1968

Cross-stream instability in a plasma.

Mixed hydromagnetic-electrostatic instability propagating perpendicular to aligned magnetic field and electron streaming in collisionless plasma

Sen, A. K.↗