Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “DIPOLE MAGNET”

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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Structural, magnetic and electrical transport properties of YMnAl

The intermetallic compound YMnAl, crystallizing in the cubic C-15 (MgCu 2 -type) structure, was prepared using arc-melting and annealing. Rietveld refinement of the XRD pattern yields a lattice parameter of a = 7.816(1) Å⁠. The system exhibits antiferromagnetic order with a transition temperature of approximately 38 K, along with indications of a spin-glass–like phase. The effective magnetic moment, estimated from Curie–Weiss fitting of the susceptibility versus temperature curve, is 6.06 μ B /f.u. and the Curie–Weiss temperature of −79 K confirming the antiferromagnetic nature. Isothermal magnetization measurements below and above the Néel temperature show no saturation, with a maximum magnetization of 0.09 μ B /f.u observed at an applied field of 9 T. The temperature dependence of resistivity exhibits a negative temperature coefficient, characteristic of dirty metals. Hall effect measurements indicate the absence of an anomalous Hall contribution. The Hall coefficient RH, carrier concentration n, and mobility μ estimated from R XY (H) are -1.05×10 -8 m 3 /C, 5.92×10 26 m -3 and 1.05×10 -3 m 2 /V.s, respectively. Our first-principles calculations indicate that YMnAl in the orthorhombic (Imma) structure has the lowest energy; however, the substitutional disorder occurring during experimental synthesis may favor the formation of the cubic Laves phase.

Crystallography↗
DOE OSTI2010

Beam Tests of a Clearing Electrode for Electron Cloud Mitigation at KEKB Positron Ring

In order to mitigate the electron cloud instability in an intense positron ring, an electron clearing electrode with a very thin structure has been developed. The electrode was tested with a positron beam of the KEKB B-factory (KEKB). A drastic reduction in the electron density around the beam was demonstrated in a wiggler magnet with a dipole-type magnetic field of 0.78 T. The clearing electrode was then applied to a copper beam pipe with antechambers assuming an application of the electrode to a wiggler section in the Super KEKB. The beam pipe was installed at a magnetic-free region in the ring and tested with beam. No extra heating of the electrodes and feed-throughs were observed. A reduction in the electron density reasonable in a magnetic-free region was also obtained.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Giant Skyrmions Stabilized by Dipole-Dipole Interactions in Thin Ferromagnetic Films

Motivated by a recent magnetization reversal experiment on a TbFeCo thin film, we study a topological excitation in the anisotropic nonlinear sigma model together with the Zeeman and magnetic dipole-dipole interactions. Dipole-dipole interactions turn a ferromagnet into a frustrated spin system, which allows a nontrivial spin texture such as a giant Skyrmion. We derive an analytic formula for the Skyrmion radius. The radius is controllable by the external magnetic field. It is intriguing that a Skyrmion may have already been observed as a magnetic domain. A salient feature is that a single Skyrmion can be created or destroyed experimentally. An analysis is made also on Skyrmions in chiral magnets.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Dual AC Dipole Excitation for the Measurement of Magnetic Multipole Strength from Beam Position Monitor Data

An experiment was conducted at Jefferson Lab's Continuous Electron Beam Accelerator Facility to develop a technique for characterizing the nonlinear fields of the beam transport system. Two air-core dipole magnets were simultaneously driven at two different frequencies to provide a time-dependent transverse modulation of the electron beam. Fourier decomposition of beam position monitor data was then used to measure the amplitude of these frequencies at different positions along the beamline. For a purely linear transport system one expects to find solely the frequencies that were applied to the dipoles with amplitudes that depend on the phase advance of the lattice. In the presence of nonlinear fields one expects to also find harmonics of the driving frequencies that depend on the order of the nonlinearity. The technique was calibrated using one of the sextupole magnets in a CEBAF beamline and then applied to a dipole to measure the sextupole and octupole strength of the magnet. A comparison is made between the beam-based measurements, results from TOSCA and data from our Magnet Measurement Facility.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Spatial Landau-Zener-Stueckelberg interference in spinor Bose-Einstein condensates

We investigate the Stueckelberg oscillations of a spin-1 Bose-Einstein condensate subject to a spatially inhomogeneous transverse magnetic field and a periodic longitudinal field. We show that the time-domain Stueckelberg oscillations result in modulations in the density profiles of all spin components due to the spatial inhomogeneity of the transverse field. This phenomenon represents the Landau-Zener-Stueckelberg interference in the space domain. Since the magnetic dipole-dipole interaction between spin-1 atoms induces an inhomogeneous effective magnetic field, interference fringes also appear if a dipolar spinor condensate is driven periodically. We also point out some potential applications of this spatial Landau-Zener-Stuekelberg interference.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

On the theory of double quantum NMR in polymer systems: The second cumulant approximation for many spin I = 1/2 systems

General analytical expressions for Double Quantum Nuclear Magnetic Resonance (DQ NMR) kinetic curves of many-spin I = 1/2 systems are derived with an accuracy of the second cumulant approximation. The expressions obtained exactly describe the initial part of the kinetic curves and provide a reasonable approximation up to times of about the effective spin-relaxation time. For the case when the system contains two isolated spins, this result exactly reproduces known expressions. In the case of polymer melts, the intermolecular magnetic dipole-dipole interactions significantly influence the time dependence of the DQ NMR kinetic curves.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Most spin-1/2 transition-metal ions do have single ion anisotropy

The cause for the preferred spin orientation in magnetic systems containing spin-1/2 transition-metal ions was explored by studying the origin of the easy-plane anisotropy of the spin-1/2 Cu{sup 2+} ions in CuCl{sub 2}·2H{sub 2}O, LiCuVO{sub 4}, CuCl{sub 2}, and CuBr{sub 2} on the basis of density functional theory and magnetic dipole-dipole energy calculations as well as a perturbation theory treatment of the spin-orbit coupling. We find that the spin orientation observed for these spin-1/2 ions is not caused by their anisotropic spin exchange interactions, nor by their magnetic dipole-dipole interactions, but by the spin-orbit coupling associated with their crystal-field split d-states. Our study also predicts in-plane anisotropy for the Cu{sup 2+} ions of Bi{sub 2}CuO{sub 4} and Li{sub 2}CuO{sub 2}. The results of our investigations dispel the mistaken belief that magnetic systems with spin-1/2 ions have no magnetic anisotropy induced by spin-orbit coupling.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Spin Emitters beyond the Point Dipole Approximation in Nanomagnonic Cavities

Control over transition rates between spin states of emitters is crucial in a wide variety of fields ranging from quantum information science to the nanochemistry of free radicals. We present an approach to drive both electric and magnetic dipole-forbidden transitions of a spin emitter by placing it in a nanomagnonic cavity, requiring a description of both the spin emitter beyond the point dipole approximation and the vacuum magnetic fields of the nanomagnonic cavity with a large spatial gradient over the volume of the spin emitter. We specifically study the silicon vacancy (SiV – ) defect in diamond, whose Zeemansplit ground states comprise a logical qubit for solid-state quantum information processing, coupled to a magnetic nanoparticle serving as a model nanomagnonic cavity capable of concentrating microwave magnetic fields into deeply subwavelength volumes. Through first-principles modeling of the SiV – spin orbitals, we calculate the spin transition densities of magnetic dipole-allowed and -forbidden transitions and calculate their coupling rates to various multipolar modes of the nanomagnonic cavity. We envision using such a framework for manipulation of quantum spin states.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Communication: Proton NMR dipolar-correlation effect as a method for investigating segmental diffusion in polymer melts

A simple and fast method for the investigation of segmental diffusion in high molar mass polymer melts is presented. The method is based on a special function, called proton dipolar-correlation build-up function, which is constructed from Hahn Echo signals measured at times t and t/2. The initial rise of this function contains additive contributions from both inter- and intramolecular magnetic dipole-dipole interactions. The intermolecular contribution depends on the relative mean squared displacements (MSDs) of polymer segments from different macromolecules, while the intramolecular part reflects segmental reorientations. Separation of both contributions via isotope dilution provides access to segmental displacements in polymer melts at millisecond range, which is hardly accessible by other methods. The feasibility of the method is illustrated by investigating protonated and deuterated polybutadiene melts with molecular mass 196 000 g/mol at different temperatures. The observed exponent of the power law of the segmental MSD is close to 0.32 ± 0.03 at times when the root MSD is in between 45 Å and 75 Å, and the intermolecular proton dipole-dipole contribution to the total proton Hahn Echo NMR signal is larger than 50% and increases with time.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Measurements of the persistent current decay and snapback effect in Nb3Sn Fermilab-built accelerator prototype magnets

In recent years, Fermilab has been performing an intensive R an D program on Nb{sub 3}Sn accelerator magnets. This program has included dipole and quadrupole magnets for different programs and projects, including LARP and VLHC. A systematic study of the persistent current decay and snapback effect in the fields of these magnets was executed at the Fermilab Magnet Test Facility. The decay and snapback were measured under a range of conditions including variations of the current ramp parameters and flattop and injection plateau durations. This study has mostly focused on the dynamic behavior of the normal sextupole and dodecapole components in dipole and quadrupole magnets respectively. The paper summarizes the recent measurements and presents a comparison with previously measured NbTi magnets.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

Effect of magnetic hysteresis on the dipole field in the EIC Rapid Cycling Synchrotron

The soft iron material, of which the yoke of a normal conducting magnet is made of, is subject to magnetic hysteresis under a time varying excitation. The hysteresis loop is influenced by the flow of induced eddy currents, which further affects the magnet field. The Rapid Cycling Synchrotron (RCS) at the planned Electron Ion Collider (EIC) facility will accelerate polarized electrons up to 18 GeV at 1 Hz. The impact of hysteresis in the magnet yoke on the magnet field during the ramp, including potential effects on cycle-to-cycle reproducibility, need to be evaluated. This will be the subject of discussion of this tech note in the context of the RCS dipoles.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Electron-cyclotron damping of helicon waves in low diverging magnetic fields

Particle-in-cell simulations are performed to investigate wave propagation and absorption behavior of low-field (B{sub 0}<5 mT) helicon waves in the presence of a diverging magnetic field. The 1D electromagnetic simulations, which include experimental external magnetic field profiles, provide strong evidence for electron-cyclotron damping of helicon waves in the spatially decaying nonuniform magnetic field. For a dipole-type magnetic field configuration, the helicon waves are absence in the downstream (lower field) region of the plasma and are observed to be completely absorbed. As the magnetic field is changed slightly however, wave damping decreases, and waves are able to propagate freely downstream, confirming previous experimental measurements of this phenomenon.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2010

Undulator Beam Pipe Magnetic Shielding Effect Tests

The proposed stainless steel beampipe for the LCLS undulator has a measurable shielding effect on the magnetic field of the LCLS undulators. This note describes the tests used to determine the magnitude of the shielding effect, as well as deviations in the shielding effect caused by placing different phase shims in the undulator gap. The effect of the proposed Steel strongback which will be used to support the beam pipe, was also studied. A hall probe on a 3 axis movement system was set up to measure the main component of the magnetic field in the Prototype Undulator. To account for temperature variations of the magnetic field of the undulator for successive tests, a correction is applied which is described in this technical note. Using this method, we found the shielding effect, the amount which the field inside the gap was reduced due to the placement of the beampipe, to be {approx}10 Gauss. A series of tests was also performed to determine the effect of phase shims and X and Y correction shims on the shielding. The largest effect on shielding was found for the .3 mm phase shims. The effect of the .3 mm phase shims was to increase the shielding effect {approx}4 Gauss. The tolerance for the shielding effect of the phase shims is less than 1 gauss. The effect of the strongback was seen in its permanent magnetic field. It introduced a dipole field across the measured section of the undulator of {approx}3 gauss. This note documents the tests performed to determine these effects, as well as the results of those tests.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Muon Acceleration with RLA and Non-scaling FFAG Arcs

Recirculating Linear Accelerators (RLA) are the most likely means to achieve the rapid acceleration of shortlived muons to multi-GeV energies required for Neutrino Factories and TeV energies required for Muon Colliders. In this paper, we present a novel return-arc optics design based on a Non Scaling Fixed Field Alternating Gradient (NS-FFAG) lattice that allows 5 and 9 GeV/c muons of both charges to be transported in the same string of magnets. The return arcs are made up of super cells with each super cell consisting of three triplets. By employing combined function magnets with dipole, quadrupole, sextupole and octupole magnetic field components, each super cell is designed to be achromatic and to have zero initial and final periodic orbit offsets for both 5 and 9 GeV/c muon momenta. This solution would reduce the number of arcs by a factor of 2, simplifying the overall design.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Muon acceleration with RLA and non-scaling FFAG ARCS

Recirculating Linear Accelerators (RLA) are the most likely means to achieve the rapid acceleration of short-lived muons to multi-GeV energies required for Neutrino Factories and TeV energies required for Muon Colliders. In this paper, we present a novel return-arc optics design based on a Non Scaling Fixed Field Alternating Gradient (NS-FFAG) lattice that allows 5 and 9 GeV/c muons of both charges to be transported in the same string of magnets. The return arcs are made up of super cells with each super cell consisting of three triplets. By employing combined function magnets with dipole, quadrupole, sextupole and octupole magnetic field components, each super cell is designed to be achromatic and to have zero initial and final periodic orbit offsets for both 5 and 9 GeV/c muon momenta. This solution would reduce the number of arcs by a factor of 2, simplifying the overall design.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Spontaneous magnetic ordering in a ferromagnetic spinor dipolar Bose-Einstein condensate

We study the spin dynamics of a spin-1 ferromagnetic Bose-Einstein condensate with magnetic dipole-dipole interaction (MDDI) based on the Gross-Pitaevskii and Bogoliubov theories. We find that various magnetic structures such as checkerboards and stripes emerge in the course of the dynamics due to the combined effects of spin-exchange interaction, MDDI, quadratic Zeeman and finite-size effects, and nonstationary initial conditions. However, the short-range magnetic order observed by the Berkeley group [Phys. Rev. Lett. 100, 170403 (2008)] is not fully reproduced in our calculations; the periodicity of the order differs by a factor of 3 and the checkerboard pattern eventually dissolves in the course of time. Possible reasons for the discrepancy are discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Hydrodynamic equation of a spinor dipolar Bose-Einstein condensate

We introduce equations of motion for spin dynamics in a ferromagnetic Bose-Einstein condensate with magnetic dipole-dipole interaction, written using a vector expressing the superfluid velocity and a complex scalar describing the magnetization. This simple hydrodynamical description extracts the dynamics of spin wave and affords a straightforward approach by which to investigate the spin dynamics of the condensate. To demonstrate the advantages of the description, we illustrate dynamical instability and magnetic fluctuation preference, which are expressed in analytical forms.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2013

Low-temperature magnetization relaxation in magnetic molecular solids

The low temperature relaxation of the magnetization in molecular magnetic solids such as Fe{sub 8} is studied using Monte Carlo simulations. A set of rate equations is then developed to understand the simulations, and the results are compared. The simulations show that the magnetization of an initially saturated sample deviates as a square-root in time at short times, as observed experimentally, and this law is derived from the rate equations analytically. -- Highlights: •A novel set of non-linear rate equations for the coupled evolution of the magnetization and dipole field distribution. •An analytic derivation of the short-time square root in time behavior of the magnetization relaxation. •Agreement between theory and simulations without further fitting parameters.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗