Search NASA⌕ Search

SEARCH · Search NASA

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 1,405 records · Page 78
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Efficient production of large {sup 39}K Bose-Einstein condensates

We describe an experimental setup and the cooling procedure for producing {sup 39}K Bose-Einstein condensates of over 4x10{sup 5} atoms. Condensation is achieved via a combination of sympathetic cooling with {sup 87}Rb in a quadrupole-Ioffe-configuration (QUIC) magnetic trap and direct evaporation in a large-volume crossed optical dipole trap, where we exploit the broad Feshbach resonance at 402 G to tune the {sup 39}K interactions from weak and attractive to strong and repulsive. In the same apparatus we create quasipure {sup 87}Rb condensates of over 8x10{sup 5} atoms.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Ultracold spin-polarized mixtures of {sup 2}{Sigma} molecules with S-state atoms: Collisional stability and implications for sympathetic cooling

The prospects of sympathetic cooling of polar molecules with magnetically cotrapped alkali-metal atoms are generally considered poor due to strongly anisotropic atom-molecule interactions leading to large spin relaxation rates. Using rigorous quantum scattering calculations based on ab initio interaction potentials, we show that inelastic spin relaxation in low-temperature collisions of CaH({sup 2}{Sigma}) molecules with Li and Mg atoms occurs at a slow rate despite the strongly anisotropic interactions. This unexpected result, which we rationalize using multichannel quantum-defect theory, opens up the possibility of sympathetic cooling of polar {sup 2}{Sigma} molecules with alkali-metal atoms in a magnetic trap and with alkaline-earth-metal atoms in an optical dipole trap.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Quench performance and field quality of FNAL twin-aperture 11 T Nb 3 Sn dipole model for LHC upgrades

A 2 m long single-aperture dipole demonstrator and two 1 m long single-aperture models based on Nb 3 Sn superconductor have been built and tested at FNAL. The two 1 m long collared coils were then assembled in a twin-aperture Nb 3 Sn dipole demonstrator compatible with the LHC main dipole and tested in two thermal cycles. This paper summarizes the quench performance of the FNAL twin-aperture Nb 3 Sn 11 T dipole in the temperature range of 1.9-4.5 K. The results of magnetic measurements for one of the two apertures are also presented. Test results are compared to the performance of coils in a single-aperture configuration. Lastly, a summary of quench propagation studies in both apertures is given.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Magneto-Mechanical Optimization of Cross-Sections for $ \text{cos}(\theta)$Accelerator Magnets

The cross-section design of cos (θ) superconducting magnets is historically developed in a two-step process: initially, the coil geometry is defined on the basis of magnetic optimizations; then, the structure is designed around the coil. The first step searches for the best coil cross-section maximizing the magnetic field, margin, field quality and conductor efficiency. The latter step aims at limiting the coil stresses and deformations. However, the coil design, defined with the initial magnetic optimization, can influence the mechanical behaviour of the magnet, altering, for example, the peak stress during operation. As the critical current is a function of the applied strain, the mechanical implications of the coil cross-section design can limit the achievable performance. In this paper we propose an integrated optimization process that targets the peak stress on the conductor in addition to the magnetic objectives. Here the results are presented for a sample high-field Nb 3 Sn dipole: a 4-layer design aiming at ultimate conductor performance.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Nonradiative recombination of excitons in semimagnetic quantum dots

The mechanisms of the nonradiative recombination of excitons in neutral and charged quantum dots based on II–VI semimagnetic semiconductors are investigated. It is shown that, along with the dipole–dipole and direct-exchange mechanisms, there is one more mechanism referred to as the indirect-exchange mechanism and related to sp–d mixing. The selection rules for nonradiative recombination by exchange mechanisms are subsequently derived. The dependence of the efficiency of all recombination mechanisms on the quantum-dot size is studied. The experimentally observed growth in the intracenter photoluminescence intensity with decreasing size of dots and nanocrystals is accounted for. Methods for experimental determination of the contributions of different mechanisms to nonradiative recombination are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Accident Scenarios for IOTA Ring and Dose Distributions Calculated with MARS15 Code

The Integrable Optics Test Accelerator (IOTA) at Fermilab’s Accelerator Science and Technology (FAST) facility [1] is a storage ring for advanced high intensity beam physics research. Layout of the ring is shown in Fig. 1. A plan view of the ring with enclosure walls are shown in Fig. 2. The entire beam, stored in the IOTA ring, is assumed to be completely lost at either of the three locations shown in Fig. 2. Therefore, we will consider three separate corresponding accident scenarios. The maximal amount of electrons stored in the IOTA ring is estimated to be 2×10 10 electrons with energy of 150 MeV. At locations 1 and 2 the beam is lost on 60-deg dipole walls, while at location 3 the beam is lost on Lambertson magnet wall.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

PRECISION MØLLER POLARIMETRY AND APPLICATIONS AT JEFFERSON LABORATORY

Jefferson Lab's cutting-edge parity-violating electron scattering program has increasingly stringent requirements for systematic errors. Beam polarimetry is often one of the dominant systematic errors in these experiments. A new Møller Polarimeter in Hall A of Jefferson Lab (JLab) was installed in 2015 and has taken first measurements for a polarized scattering experiment. Upcoming parity violation experiments in Hall A include CREX, PREX-II, MOLLER and SOLID with the latter two requiring <0.5% precision on beam polarization measurements, a precision which has not been achieved to date. The polarimeter measures the Møller scattering rates of the polarized electron beam incident upon an iron target placed in a saturating magnetic field. The spectrometer consists of four quadrupoles and one momentum selection dipole. The detector is designed to measure the scattered and knock out target electrons in coincidence. Beam polarization is extracted by constructing an asymmetry from the scattering rates when the incident electron spin is parallel and antiparallel to the target electron spin. The largest systematic errors associated with Møller polarimetry comes from the precision that the target polarization and the detector acceptance is known will be discussed. Other errors including the Levchuk effect, beam stability, and target heating will be addressed.

Henry, William↗
DOE OSTI2025

Multi-qubit nanoscale sensing with entanglement as a resource

Nitrogen vacancy (NV) centres in diamond are widely deployed as local magnetic sensors, using single-qubit control to measure both time-averaged fields and noise with nanoscale spatial resolution. Moving beyond single qubits to multi-qubit control enables new sensing modalities such as measuring nonlocal spatiotemporal correlators or using entangled states to enhance measurement sensitivity. Here, in this work, we describe protocols for using optically unresolved NV centre pairs and nuclear spins as multi-qubit sensors for measuring correlated noise at nanometre length scales. For noninteracting NV centres, we implement a phase-cycling protocol that disambiguates magnetic correlations from variance fluctuations, leveraging the presence of a third qubit, a 13 C nucleus, to effect coherent single-NV spin flips and enable phase cycling even for co-aligned NV centres that are spectrally unresolved. For length scales around 10 nm, we create maximally entangled Bell states through dipole–dipole coupling between two NV centres and use these entangled states to directly read out the magnetic field correlation, rather than reconstructing it from independent measurements of unentangled NV centres. Importantly, this changes the scaling of sensitivity with readout noise from quadratic to linear. For conventional off-resonant readout of the NV centre spin state (for which the readout noise is roughly 30 times the quantum projection limit), this results in more than an order of magnitude improvement in sensitivity. Finally, we demonstrate methods for detecting high spatial- and temporal-resolution correlators with pairs of strongly interacting NV centres.

condensed-matter physics↗
DOE OSTI2014

Theoretical estimates of the anapole magnetizabilities of C{sub 4}H{sub 4}X{sub 2} cyclic molecules for X=O, S, Se, and Te

Calculations have been carried out for C{sub 4}H{sub 4}X{sub 2} cyclic molecules, with X=O, S, Se, and Te, characterized by the presence of magnetic-field induced toroidal electron currents and associated orbital anapole moments. The orbital anapole induced by a static nonuniform magnetic field B, with uniform curl C=∇×B, is rationalized via a second-rank anapole magnetizability tensor a{sub αβ}, defined as minus the second derivative of the second-order interaction energy with respect to the components C{sub α} and B{sub β}. The average anapole magnetizability a{sup ¯} equals −χ{sup ¯}, the pseudoscalar obtained by spatial averaging of the dipole-quadrupole magnetizability χ{sub α,βγ}. It has different sign for D and L enantiomeric systems and can therefore be used for chiral discrimination. Therefore, in an isotropic chiral medium, a homogeneous magnetic field induces an electronic anapole A{sub α}, having the same magnitude, but opposite sign, for two enantiomorphs.

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

Mössbauer investigations of hyperfine interactions features of {sup 57}Fe nuclei in BiFeO{sub 3} ferrite

New results of {sup 57}Fe Mössbauer studies on BiFeO{sub 3} powder sample performed at various temperatures above and below magnetic phase transitions point T{sub N} ≈ 640K are reported. We have performed self-consistent calculations of the lattice contributions to the EFG tensor, taking into account dipole moments of the O{sup 2−} and Bi{sup 3+} ions. Low-temperature {sup 57}Fe Mössbauer spectra recorded at T < T{sub N} were analyzed assuming an anharmonic cycloidal modulation of the Fe{sup 3+} magnetic moments. The cycloidal modulation of the iron spin was described with the elliptic Jacobi function sn[(±4K(m)/λ)x,m]. The good fit of the experimental spectra was obtained for the anharmonicity m = 0.44 ± 0.04 (T = 4.9K) resulting from the easy-axis magnetic anisotropy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Investigation on the pyroelectric property of polycrystalline GdMnO{sub 3}

Pyroelectric property of orthorhomic GdMnO{sub 3} polycrystalline samples was investigated. Two pyrocurrent peaks were observed with the sharp one near 20 K and the broad one at around 120 K. The dependences of these two peaks on magnetic field, heating rate, and poling voltage were explored systematically. The sharp peak is related to the ferroelectric transition, while the behavior of the broad one corresponds to dipole reorientation. Some key pyroelectric features are proposed to separate the spin-induced ferroelectricity from other effects. This work is helpful for understanding the pyroelectric property of multiferroic materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Magnetar Broadband X-Ray Spectra Correlated with Magnetic Fields: Suzaku Archive of SGRs and AXPs Combined with NuSTAR, Swift, and RXTE

The 1–70 keV persistent spectra of 15 magnetars, observed with Suzaku from 2006 to 2013, were studied as a complete sample. Combined with early NuSTAR observations of four hard X-ray emitters, nine objects showed a hard power-law emission dominating at ≳10 keV with the 15–60 keV flux of ∼1–11×10{sup −11} erg s{sup −1} cm{sup −2}. The hard X-ray luminosity L{sub h}, relative to that of a soft-thermal surface radiation L{sub s}, tends to become higher toward younger and strongly magnetized objects. Their hardness ratio, updated from a previous study and defined as ξ=L{sub h}/L{sub s}, is correlated with the measured spin-down rate P-dot as ξ=0.62×( P-dot /10{sup −11}ss{sup −1}){sup 0.72}, corresponding to positive and negative correlations with the dipole field strength B{sub d} (ξ∝B{sub d}{sup 1.41}) and the characteristic age τ{sub c} (ξ∝τ{sub c}{sup −0.68}), respectively. Among our sample, five transients were observed during X-ray outbursts, and the results are compared with their long-term 1–10 keV flux decays monitored with Swift/XRT and RXTE/PCA. Fading curves of three bright outbursts are approximated by an empirical formula used in the seismology, showing a ∼10–40 day plateau phase. Transients show the maximum luminosities of L{sub s} ∼ 10{sup 35} erg s{sup −1}, which are comparable to those of persistently bright ones, and fade back to ≲10{sup 32} erg s{sup −1}. Spectral properties are discussed in the framework of the magnetar hypothesis.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Model-independent analysis of the Fermilab Tevatron turn-by-turn beam position monitor measurements

Coherent transverse beam oscillations in the Tevatron were analyzed with the model-independent analysis (MIA) technique. This allowed one to obtain the model-independent values of coupled betatron amplitudes, phase advances, and dispersion function around the ring from a single dipole kick measurement. In order to solve the MIA mode mixing problem which limits the accuracy of determination of the optical functions, we have developed a new technique of rotational MIA mode untangling. The basic idea is to treat each beam position monitor (BPM) as two BPMs separated in a ring by exactly one turn. This leads to a simple criterion of MIA mode separation: the betatron phase advance between any BPM and its counterpart shifted by one turn should be equal to the betatron tune and therefore should not depend on the BPM position in the ring. Furthermore, we describe a MIA-based technique to locate vibrating magnets in a storage ring.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

The effect of polymer stiffness on magnetization reversal of magnetorheological elastomers

Ultrasoft magnetorheological elastomers (MREs) offer convenient real-time magnetic field control of mechanical properties that provides a means to mimic mechanical cues and regulators of cells in vitro. Here, we systematically investigate the effect of polymer stiffness on magnetization reversal of MREs using a combination of magnetometry measurements and computational modeling. Poly-dimethylsiloxane-based MREs with Young’s moduli that range over two orders of magnitude were synthesized using commercial polymers Sylgard™ 527, Sylgard 184, and carbonyl iron powder. The magnetic hysteresis loops of the softer MREs exhibit a characteristic pinched loop shape with almost zero remanence and loop widening at intermediate fields that monotonically decreases with increasing polymer stiffness. A simple two-dipole model that incorporates magneto-mechanical coupling not only confirms that micrometer-scale particle motion along the applied magnetic field direction plays a defining role in the magnetic hysteresis of ultrasoft MREs but also reproduces the observed loop shapes and widening trends for MREs with varying polymer stiffnesses.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Creating a three-dimensional intrinsic electric dipole on rotated CrI 3 bilayers

Here two-dimensional (2D) materials are being explored as a novel multiferroic platform. One of the most studied magnetoelectric multiferroic 2D materials are antiferromagnetically coupled (AFM) CrI 3 bilayers. Neglecting magnetism, those bilayers possess a crystalline point of inversion, which is only removed by the antiparallel spin configuration among its two constituent monolayers. The resulting intrinsic electric dipole on those bilayers has a magnitude no larger than 0.04 pC/m, it points out of plane, and it reverts direction when the Ising-like-chromium spins are flipped (toward opposite layers versus away from opposite layers). The combined presence of antiferromagnetism and a weak intrinsic electric dipole makes this material a two-dimensional magnetoelectric multiferroic. Here, we remove the crystalline center of inversion of the bilayer by a relative 60° rotation of its constituent monolayers. This process enhances the out-of-plane intrinsic electric dipole tenfold with respect to its magnitude in the nonrotated AFM bilayer and also creates an even stronger and switchable in-plane intrinsic electric dipole. The ability to create a three-dimensional electric dipole is important because it enhances the magnetoelectric coupling on this experimentally accessible 2D material, which is explicitly calculated here as well.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Spin polarization transfer by the radical pair mechanism

In a three-site representation, we study a spin polarization transfer from radical pair spins to a nearby electron or nuclear spin. The quantum dynamics of the radical pair spins is governed by a constant exchange interaction between the radical pair spins which have different Zeeman frequencies. Radical pair spins can recombine to the singlet ground state or to lower energy triplet states. It is then shown that the coherent dynamics of the radical pair induces spin polarization on the nearby third spin in the presence of a magnetic field. The spin polarization transfer depends on the difference between Zeeman frequencies, the singlet and triplet recombination rates, and on the exchange and dipole-dipole interactions between the different spins. In particular, the sign of the polarization depends on the exchange coupling between radical pair spins and also on the difference between singlet and triplet recombination rate constants.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2010

Physical Properties Of Eu{sub 3}Ba{sub 2}Mn{sub 2}Cu{sub 2}O{sub 12}

The physical properties of the manganocuprate compound, Eu{sub 3}Ba{sub 2}Mn{sub 2}Cu{sub 2}O{sub 12}(Eu-3222) are investigated using X-ray diffraction, resistivity, magnetization and dielectric measurements. The structure of the Eu-3222 compound is made by the intermixing of Eu-123 (oxygen deficient triple perovskite block) and Eu-214 (K{sub 2}NiF{sub 4} type single rock-salt like block). Electrical resistivity data show insulating behavior down to the measurable temperature and exhibits a conduction mechanism which can be explained on the basis of 3D variable range hopping model. Magnetization data shows a antiferromagnetic behavior at 5 K, however without any clear signature of magnetic ordering in the temperature range 5-300 K. Dielectric (Capacitance), measured as a function of temperature at various frequencies exhibits frequency dependence, indicating glassy relaxation of dipole moments.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Beam line shielding calculations for an Electron Accelerator Mo-99 production facility

The purpose of this study is to evaluate the photon and neutron fields in and around the latest beam line design for the Mo-99 production facility. The radiation dose to the beam line components (quadrupoles, dipoles, beam stops and the linear accelerator) are calculated in the present report. The beam line design assumes placement of two cameras: infra red (IR) and optical transition radiation (OTR) for continuous monitoring of the beam spot on target during irradiation. The cameras will be placed off the beam axis offset in vertical direction. We explored typical shielding arrangements for the cameras and report the resulting neutron and photon dose fields.

43 PARTICLE ACCELERATORS↗