Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “MAGNETIC DIPOLES”

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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

High spatial and energy resolution electron energy loss spectroscopy of the magnetic and electric excitations in plasmonic nanorod oligomers

We leverage the high spatial and energy resolution of monochromated aberration-corrected scanning transmission electron microscopy to study the hybridization of cyclic assemblies of plasmonic gold nanorods. Detailed experiments and simulations elucidate the hybridization of the coupled long-axis dipole modes into collective magnetic and electric dipole plasmon resonances. We resolve the magnetic dipole mode in these closed loop oligomers with electron energy loss spectroscopy and confirm the mode assignment with its characteristic spectrum image. The energy splitting of the magnetic mode and antibonding modes increases with the number of polygon edges (n). For the n=3-6 oligomers studied, optical simulations using normal incidence and s-polarized oblique incidence show the respective electric and magnetic modes’ extinction efficiencies are maximized in the n=4 arrangement.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Exploiting Nonlinear Elasticity for Anomalous Magnetoresponsive Stiffening

Here, a paradigm for enhanced magnetorheological elastic materials is introduced and experimentally established. We show that a nonlinearly stiffening polymer matrix can be exploited to achieve anomalous magneto-elastomer stiffening exceeding standard magneto-elastomer theory and experiment in terms of percentage stiffness change and sensitivity to applied magnetic flux. Using a model system of a semifexible fibrin network embedded with micron sized carbonyl iron particles, we demonstrate that even at a modest particle volume fraction (0.5-4%), a coupling between the magnetically-interacting dipoles and a strain-stiffening polymer mesh provides previously unexplored opportunities for material design. Our experiments indicate that confined particles within thefibrin network internally tension and stiffen the polymer mesh when an external field is applied, resulting in a field-dependent stiffening response from the polymer mesh that superposes with the magnetic interparticle interactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1993

Improvement of persistent magnetic field trapping in bulk Y-Ba-Cu-O superconductors

For type-II superconductors, magnetic field can be trapped due to persistent internal supercurrent. Quasi-persistent magnetic fields near 2 T at 60 K (and 1.4 T at 77 K) have been measured in minimagnets made of proton-irradiated melt-textured Y-Ba-Cu-O (MT-Y123) samples. Using the trapping effect, high-field permanent magnets with dipole, quadrupole, or more complicated configurations can be made of existing MT-Y123 material, thus bypassing the need for high-temperature superconductor (HTS) wires. A phenomenological current model has been developed to account for the trapped field intensity and profile in HTS samples. This model is also a guide to select directions of materials development to further improve field trapping properties. General properties such as magnetic field intensities, spatial distributions, stabilities, and temperature dependence of trapped field are discussed.

Chen, In-Gann↗
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↗
NASA NTRS1994

Global, quasi-steady dynamics of the distant solar wind. 1: Origin of north-south flows in the outer heliosphere

Regular, large amplitude north-south flow deflections were observed near the heliographic equator by Voyager 2 in the outer heliosphere in 1986. We present results of numerical simulations supporting the idea that these motions are driven by interplanetary dynamical interactions occurring at quasi-steady stream fronts associated with the tilted-dipole coronal magnetic configuration at solar minimum. It is shown that under these conditions the coronal geometry is deeply impressed upon the large scale flow and it determines the disposition and orientation of solar wind structures to great heliocentric distances. The observed predominance of the north-south flow deflections (relative to the east-west deflections) and their observed quasiperiodicity are seen to be a natural consequence of the two-sector tilted-dipole stream structure in which the fronts of successive corotating interaction regions have opposing north-south tilts.

Pizzo, V. J.↗
NASA NTRS1995

Expanding our knowledge of the heliosphere

Milestones on our road to understanding the heliosphere between 1950 and 1988 are recalled. Among these are early studies of solar energetic particles suggesting a heliospheric boundary at 5 AU, the discovery of the solar wind and the sectored nature of the interplanetary magnetic field. Recent results, particularly from the Ulysses spacecraft, confirm the arrival of neutrals from interstellar space, the pick-up of singly charged ions by the solar wind and the acceleration of these ions to become anomalous cosmic rays. Two distinct solar wind regimes have been discovered. At low heliolatitudes a highly variable solar wind blows at an average speed around 450 km/s, while at high latitudes a relatively smooth 750 km/s flow is observed. No indicators of a dipole-like magnetic field have been seen by Ulysses in solar polar latitudes. The cosmic radiation increase with latitude is much smaller than predicted. The status of and plans for the Voyager 1 and 2, Pioneer 10 and 11, and Ulysses spacecraft are outlined.

Page, D. E.↗
DOE OSTI2026

A flexible and differentiable coil proxy for stellarator equilibrium optimization

Balancing plasma performance and coil cost is a significant challenge when designing a stellarator power plant. Most current stellarator designs are produced through two-stage optimization: stage-1 for the equilibrium and stage-2 for a coil design that reproduces its magnetic configuration. Because few proxies connect both stages, two-stage optimization can produce plasmas that have high-quality physical properties but overly complex coils. In recent years, single-stage optimization has increasingly been used to optimize the plasma and coils simultaneously in order to improve the plasma–coil balance. However, all existing single-stage tools are specialized for filament coils, cannot model coil systems containing permanent magnets or dipole arrays, and continue to be challenged by numerical problems. The quasi-single-stage optimization finds a middle ground by integrating a coil optimization subproblem into stage-1 optimization. We present a flexible, differentiable coil complexity proxy based on the newly developed QUADCOIL coil optimization code. QUADCOIL is fast and can target realistic coil metrics and constraints that are unavailable to codes with comparable speed. We demonstrate the effectiveness and flexibility of the QUADCOIL proxy by presenting two QSS optimization studies. The first study produces a permanent magnet solution for the MUSE stellarator with 34% fewer magnets than previous solutions. The second study produces a coil solution for the ARIES-CS stellarator with 30% reductions in both peak and root-mean-square force.

Fu, Lanke [Princeton Plasma Physics Laboratory (PP↗
DOE OSTI2016

Remote temperature distribution sensing using permanent magnets

Remote temperature sensing is essential for applications in enclosed vessels where feedthroughs or optical access points are not possible. A unique sensing method for measuring the temperature of multiple closely-spaced points is proposed using permanent magnets and several three-axis magnetic field sensors. The magnetic field theory for multiple magnets is discussed and a solution technique is presented. Experimental calibration procedures, solution inversion considerations and methods for optimizing the magnet orientations are described in order to obtain low-noise temperature estimates. The experimental setup and the properties of permanent magnets are shown. Finally, experiments were conducted to determine the temperature of nine magnets in different configurations over a temperature range of 5 to 60 degrees Celsius and for a sensor-to-magnet distance of up to 35 mm. Furthermore, to show the possible applications of this sensing system for measuring temperatures through metal walls, additional experiments were conducted inside an opaque 304 stainless steel cylinder.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

Wakefields of a Beam near a Single Plate in a Flat Dechirper

At linac-based, X-ray free electron lasers (FELs), there is interest in streaking the beam by inducing the transverse wakes in a flat dechirper, by passing the beam near to one of its two jaws. For LCLS-II - as has already been done for LCLS-I - this way of using the dechirper will e.g. facilitate two-color and fresh slice schemes of running the FEL. With the beam a distance from the near wall of say b ~ 0.25 mm and from the far wall by ≳ 5 mm, the second wall will no longer affect the results. The physics will be quite different from the two plate case: with two plates the impedance has a resonance spike whose frequency depends on the plate separation 2a; in the single plate case this parameter no longer exists. Formulas for the longitudinal, dipole, and quadrupole wakes for a beam off-axis between two dechirper plates, valid for the range of bunch lengths of interest in an X-ray FEL, are given in reference 3. By taking the proper limit, we can obtain the corresponding wakes for a beam close to one dechirper plate and far from the other. This is the task we perform in this note.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Size and Strength of Self-excited Dynamos in Jupiter-like Extrasolar Planets

The magnetization of solar and extrasolar gas giants is critically dependent on electronic and mass transport coefficients of their convective fluid interiors. We analyze recent laboratory experimental results on metallic hydrogen to derive a new conductivity profile for the Jovian-like planets. We combine this revised conductivity with a polytropic-based thermodynamic equation of state to study the dynamo action in 100 extrasolar giant planets varying from synchronous hot Jupiters to fast rotators, with masses ranging from 0.3M J to 15M J . We find dynamo cores larger than previous estimates, but consistent with the results from Juno, suggesting that the field generation in the more massive planets might be shallow-seated. Our results reveal that most extrasolar giants are expected to possess dipole surface magnetic fields in the range of 0.1-10 Gauss. Assuming radio emission processes similar to our solar giants, the stronger emitters are expected to have maximal cyclotron frequencies between 20-40 MHz and for those within few 10 pc, few have flux densities greater than 1 mJy. In conclusion, our work places new bounds on the observational detectability of extrasolar magnetic fields.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Confusion-Driven Machine Learning of Structural Phases of a Flexible, Magnetic Stockmayer Polymer

We use a semisupervised, neural-network-based machine learning technique, the confusion method, to investigate structural transitions in magnetic polymers, which we model as chains of magnetic colloidal nanoparticles characterized by dipole–dipole and Lennard-Jones interactions. As input for the neural network, we use the particle positions and magnetic dipole moments of equilibrium polymer configurations, which we generate via replica-exchange Wang–Landau simulations. We demonstrate that by measuring the classification accuracy of neural networks, we can effectively identify transition points between multiple structural phases without any prior knowledge of their existence or location. We corroborate our findings by investigating relevant conventional order parameters. Our study furthermore examines previously unexplored low-temperature regions of the phase diagram, where we find new structural transitions between highly ordered helicoidal polymer configurations.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Mechanical Design of the Interaction Region Dipole B1pF for Electron Ion Collider

Here, the Electron-Ion Collider (EIC), planned for construction at Brookhaven National Laboratory, will consist of two intersecting beams of intense electrons and high-energy protons or heavier atomic nuclei. The collider will need many demanding components, including high field superconducting magnets for the Interaction Region (IR). It has been decided that a prototype of one such magnet, the B1pF dipole, shall be built, to validate design choices common to all Rutherford cable dipole and quadrupole IR magnets. B1pF is one of several high field magnets in the interaction region whose design is based on the 15.1 mm wide NbTi cable, a cable like the one used in the main dipole coil of the Large Hadron Collider (LHC) at CERN. The current design is based on a single layer coil with an inner diameter of 300 mm and magnetic length of ~3 m which generates a magnetic field at the center of the magnet of about 3.7 T at a current of ~11 kA at design. This paper presents the mechanical design of the B1pF dipole magnet, and the R&D effort associated with the development of the prototype, including tests for successfully winding and curing coils of the needed configuration into proper structural and magnetic elements, and including a multilayer magnetic return yoke which meets field requirements while providing an initial reduced structure suitable for operational testing in an existing test facility.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Force on an electric/magnetic dipole and classical approach to spin–orbit coupling in hydrogen-like atoms

We carry out the classical analysis of spin–orbit coupling in hydrogen-like atoms, using the modern expressions for the force and energy of an electric/magnetic dipole in an electromagnetic field. We disclose a novel physical meaning of this effect and show that for a laboratory observer the energy of spin–orbit interaction is represented solely by the mechanical energy of the spinning electron (considered as a gyroscope) due to the Thomas precession of its spin. Concurrently we disclose some errors in the old and new publications on this subject. - Highlights: • Classical analysis of spin–orbit coupling in a laboratory frame was erroneous. • Electromagnetic energy of electron in atom does not contribute to spin–orbit coupling. • Spin–orbit splitting results from the energy of Thomas precession of electron spin.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Magnetic and Mechanical Analysis of Bi-2212 Rutherford Cable in a Cos-Theta Sub-Scale Dipole Coil

The U.S. Magnet Development Program (US-MDP) explores high-field accelerator magnets compatible with operational conditions beyond the limits of Nb$_3$Sn technology. The ongoing R&D High-Temperature Superconductors (HTS) suggests using Bi$_2$Sr$_2$CaCu$_2$O$_{8-x}$ (Bi-2212) as superconducting element. Bi-2212 Rutherford cables maintain a high critical current (I$_C$) when exposed to a large external magnetic field. However, Bi-2212 exhibits an oversensitive stress-strain response when subject to large Lorentz forces. This paper reports on the magnetic and mechanical analysis of the Bi-2212 cosine-theta insert being developed at Fermilab for a hybrid magnet composed of two external layers of Nb$_3$Sn and two internal layers of Bi-2212. We performed a FEM analysis of the insert to estimate the HTS stress state in the coil's strands under magnetic and mechanical loads.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

SU-E-T-661: Quantitative MRI Assessment of a Novel Direction-Modulated Brachytherapy Tandem Applicator for Cervical Cancer

Purpose: To quantitatively evaluate the MR image quality of a novel direction modulated brachytherapy (DMBT) tandem applicator for cervical cancer, using the clinical MRI scanning protocol for image guided brachytherapy. Methods: The tungsten alloy-based applicator was placed in a water phantom and clinical imaging protocol was performed. Axial images were acquired using 2D turbo-spin echo (TSE) T2-weighted sequence on a 1.5T GE 450w MR scanner and an 8-channel body coil. As multi-channel receiver coil was used, inhomogeneities in the B1 receive field must be considered before performing the quantification process. Therefore the applicator was removed from the phantom and the whole imaging session was performed again for the water phantom with the same parameters. Images from the two scans were then subtracted, resulting in a difference image that only shows the applicator with its surrounding magnetic susceptibility dipole artifact. Line profiles were drawn and plotted on the difference image at various angles and locations along the tandem. Full width at half maximum (FWHM) was measured at all the line profiles to quantify the extent of the artifact. Additionally, the extent of the artifact along the diameter of the tandem was measured at various angles and locations. Results: After removing the background inhomogeneities of the receiver coil, FWHM of the tandem measured 5.75 ± 0.35 mm (the physical tandem diameter is 5.4 mm). The average extent of the artifacts along the diameter of the tandem measured is 2.14 ± 0.56 mm. In contrast to CT imaging of the same applicator (not shown here), the tandem can be easily identified without additional correction algorithms. Conclusion: This work demonstrated that the novel DMBT tandem applicator has minimal susceptibility artifact in T2-weighted images employed in clinical practice for MRI-guided brachytherapy of cervical cancer.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Hyperfine structures and Landé g{sub J}-factors for n=2 states in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations

Energy levels, hyperfine interaction constants, and Landé g{sub J}-factors are reported for n=2 states in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations. Valence, core–valence, and core–core correlation effects are taken into account through single and double-excitations from multireference expansions to increasing sets of active orbitals. A systematic comparison of the calculated hyperfine interaction constants is made with values from the available literature.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

An angular frequency dependence on the Aharonov–Casher geometric phase

A quantum effect characterized by a dependence of the angular frequency associated with the confinement of a neutral particle to a quantum ring on the quantum numbers of the system and the Aharonov–Casher geometric phase is discussed. Then, it is shown that persistent spin currents can arise in a two-dimensional quantum ring in the presence of a Coulomb-type potential. A particular contribution to the persistent spin currents arises from the dependence of the angular frequency on the geometric quantum phase.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Propagation of EMIC Waves From Shabansky Orbits in the Dayside Magnetosphere

We explore the characteristics of EMIC waves generated in a non-dipole, compressed magnetic field at the minimum of the magnetic field. We conducted 2D full-wave simulations using the Petra-M code, focusing on a compressed magnetic field in the outer dayside magnetosphere for a range of L values (L = 8 - 10). By comparing the simulation results with MMS observations, we aim to understand how the observed wave characteristics are affected by a shifting source region across different L-shells. Our findings indicate that the direction of the Poynting vector systematically changes depending on the local source location of the wave, which is consistent with the observations. EMIC waves propagate along the magnetic field line and reach both the northern and southern hemispheres; however, there is a notable difference in the power of EMIC waves between the two hemispheres, indicating seasonal asymmetries in their occurrence.

58 GEOSCIENCES↗