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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.

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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Probing magnetic and electric optical responses of silicon nanoparticles

We study experimentally both magnetic and electric optically induced resonances of silicon nanoparticles by combining polarization-resolved dark-field spectroscopy and near-field scanning optical microscopy measurements. We reveal that the scattering spectra exhibit strong sensitivity of electric dipole response to the probing beam polarization and attribute the characteristic asymmetry of measured near-field patterns to the excitation of a magnetic dipole mode. The proposed experimental approach can serve as a powerful tool for the study of photonic nanostructures possessing both electric and magnetic optical responses.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Influence of Compaction During Reaction Heat Treatment on the Interstrand Contact Resistances of Nb 3 Sn Rutherford Cables for Accelerator Magnets

The high field superconducting magnets required for ongoing and planned upgrades to the Large Hadron Collider (LHC) will be wound with Nb 3 Sn Rutherford cables for which reason studies of Nb 3 Sn strand, cable, and magnet properties will continue to be needed. Of particular importance is field quality. Here, the amplitudes of multipoles in the bore fields of dipole and quadrupole magnets, induced by ramp-rate-dependent coupling currents, are under the control of the interstrand contact resistances-crossing strand, R c , adjacent strand, R a , or a combination of them, R eff . Although two decades ago it was agreed that for the LHC R c should be in the range 10-30 μΩ, more recent measurements of LHC quadrupoles have revealed R c values ranging from 95 to 230 μΩ. This paper discusses ways in which these values can be achieved. In a heavily compacted cable R eff can be tuned to some predictable value by varying the width of an included stainless steel (effectively “insulating”) core. But cables are no longer heavily compacted with the result that the crossing strands of the impregnated cable are separated by a thick epoxy layer that behaves like an insulating core. If a stainless steel core is actually present, Reff must be independent of core width. Since there is no guarantee that a fixed predetermined amount of interlayer separation could be reproduced from winding to winding it would be advisable to include a full width core.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

THE EFFECT OF MAGNETIC TOPOLOGY ON THERMALLY DRIVEN WIND: TOWARD A GENERAL FORMULATION OF THE BRAKING LAW

Stellar wind is thought to be the main process responsible for the spin down of main-sequence stars. The extraction of angular momentum by a magnetized wind has been studied for decades, leading to several formulations for the resulting torque. However, previous studies generally consider simple dipole or split monopole stellar magnetic topologies. Here we consider, in addition to a dipolar stellar magnetic field, both quadrupolar and octupolar configurations, while also varying the rotation rate and the magnetic field strength. Sixty simulations made with a 2.5D cylindrical and axisymmetric set-up, and computed with the PLUTO code, were used to find torque formulations for each topology. We further succeed to give a unique law that fits the data for every topology by formulating the torque in terms of the amount of open magnetic flux in the wind. We also show that our formulation can be applied to even more realistic magnetic topologies, with examples of the Sun in its minimum and maximum phases as observed at the Wilcox Solar Observatory, and of a young K-star (TYC-0486-4943-1) whose topology has been obtained by Zeeman-Doppler Imaging.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Performance of a MQXF Nb 3 Sn Quadrupole Magnet Under Different Stress Level

In a dipole or in a quadrupole accelerator magnet, the displacement of the coil turns induced by the electromagnetic forces can cause quenches limiting the magnet performance. For this reason, an azimuthal preload is applied to avoid azimuthal movements of the coil up to the required operational current. However, several tests showed that accelerator magnets can operate with a partial preload, i.e. that coil unloading during the ramp does not prevent reaching higher currents. This issue is particularly relevant for Nb 3 Sn magnets, where the loads applied to the Nb3Sn filaments can reach the degradation limits of critical current. In order to investigate the impact of coil preload on the quench performance, the MQXFS6 short model quadrupole for the High Luminosity Upgrade was tested under an azimuthal preload at 80% of the short sample current, reaching 93% of short sample current at 1.9 K. The preload was then released to 60%, still showing ability to operate in the range of 80-85% of short sample current as required by HL-LHC project. With this lower preload, the ability of going above 90% of short sample was lost, and a significant training appeared above 85%. When the preload was restored to the original 80% value, the magnet reached with few quenches 95% of short sample (13.4 T peak field). Magnetic measurements confirm the larger movement of the coil in the case with lower preload, and agree with finite element simulations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Frustrated Dipole Order Induces Noncollinear Proper Ferrielectricity in Two Dimensions

Within Landau theory, magnetism and polarity are homotopic, displaying a one-to-one correspondence between most physical characteristics. Yet, despite widely reported noncollinear magnetism, spontaneous noncollinear electric dipole order as a ground state is rare. In this work, a dioxydihalides family is suggested to display noncollinear ferrielectricity, induced by competing ferroelectric and antiferroelectric soft modes. This intrinsic of dipoles generates unique physical properties, such as $\mathbb{Z_{2}×Z_{2}}$ topological domains, atomic-scale dipole vortices, and negative piezoelectricity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

On the He–McKellar–Wilkens phase of an electric dipole

The He–McKellar–Wilkens (HMW) phase of an electric dipole moving in a static magnetic field is derived by explicitly considering the interaction between the currents associated with the moving dipole and the magnetic vector potential. Conditions for the observation of the HMW phase in different field configurations are investigated. A practical setup is proposed that provides essentially a radial magnetic field with inverse radial dependence for the observation of the HMW phase with magnetic field alone. Possible magnetic field control of exciton current in an open ring setup is discussed. - Highlights: • Conditions for the observation of the HMW phase in different field configurations are investigated. • A practical setup is proposed that for the observation of the HMW phase with magnetic field alone. • Possible magnetic field control of exciton current in an open ring setup is discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

MAGNETIC BRAKING FORMULATION FOR SUN-LIKE STARS: DEPENDENCE ON DIPOLE FIELD STRENGTH AND ROTATION RATE

We use two-dimensional axisymmetric magnetohydrodynamic simulations to compute steady-state solutions for solar-like stellar winds from rotating stars with dipolar magnetic fields. Our parameter study includes 50 simulations covering a wide range of relative magnetic field strengths and rotation rates, extending from the slow- and approaching the fast-magnetic-rotator regimes. Using the simulations to compute the angular momentum loss, we derive a semi-analytic formulation for the external torque on the star that fits all of the simulations to a precision of a few percent. This formula provides a simple method for computing the magnetic braking of Sun-like stars due to magnetized stellar winds, which properly includes the dependence on the strength of the magnetic field, mass loss rate, stellar radius, surface gravity, and spin rate, and which is valid for both slow and fast rotators.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Proof-of-Principle Design of a High-Field Overpass/Underpass Nb 3 Sn Dipole

A block coil geometry is appealing in the body of particle accelerator dipole or quadrupole magnets, but less so in the ends of conventional designs, because conductors near the midplane of the beam tube must be bent in the hard direction to cross over to the other side of the tube. In order to avoid damage to brittle conductors such as Nb 3 Sn or HTS, the bend must be very gradual, resulting in undesirably long magnet ends. An alternative design -"overpass/underpass" or "cloverleaf" - can ramp the conductor within a short length with bending only in the easy direction. Described here is a proof-of-principle design and analysis of an "overpass/underpass" coil geometry for a block coil dipole of 11 Tor more.

47 OTHER INSTRUMENTATION↗
DOE OSTI2026

Design and Construction of a Superconducting “Direct Wind” R&D Magnet for the EIC Interaction Region

Brookhaven National Laboratory (BNL) was chosen to host the international Electron-Ion Collider (EIC), which will collide high energy and highly polarized hadron and electron beams with a center of mass energy up to 140 GeV. The Interaction Region (IR) [1] requires several large aperture, relatively high field superconducting dipole and quadrupole magnets, some of which are very closely spaced.\r\nA value engineering effort is underway as part of the EIC Project to construct and test a Direct Wind magnet [2] (coil comprised of NbTi conductor deposited directly onto a support tube, in this instance tapered, and secured mechanically against Lorentz forces afterwards) to replace two Rutherford cable collared magnets. This magnet exceeds the combination of aperture, number of coil \r\nlayers, and magnetic field, as compared to existing accelerator and R&D Direct Wind magnets to date. Furthermore, construction has been completed using a newly commissioned winding machine, upgraded in anticipation of the upcoming EIC production coil fabrication. Design, analysis, construction issues, lessons learned and accomplishments to date shall be discussed, including the \r\nachieved corrections to multipoles made to successive coil layers based on warm magnetic measurements of preceding layers.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Development of Cogging at the Fermilab Booster

The development of magnetic cogging is part of the Fermilab Booster upgrade within the Proton Improvement Plan (PIP). The Booster is going to send 2.25E17 protons/hour which is almost double the present flux, 1.4E17 protons/hour to the Main Injector (MI) and Recycler (RR). The extraction kicker gap has to synchronize to the MI and RR injection bucket in order to avoid a beam loss at the rising edge of the extraction and injection kickers. Magnetic cogging is able to control the revolution frequency and the position of the gap using the magnetic field from dipole correctors while radial position feedback keeps the beam at the central orbit. The new cogging is expected to reduce beam loss due to the orbit changes and reduce beam energy loss when the gap is created. The progress of the magnetic cogging system development is going to be discussed in this paper.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

MAGNETICALLY CONTROLLED ACCRETION FLOWS ONTO YOUNG STELLAR OBJECTS

Accretion from disks onto young stars is thought to follow magnetic field lines from the inner disk edge to the stellar surface. The accretion flow thus depends on the geometry of the magnetic field. This paper extends previous work by constructing a collection of orthogonal coordinate systems, including the corresponding differential operators, where one coordinate traces the magnetic field lines. This formalism allows for an (essentially) analytic description of the geometry and the conditions required for the flow to pass through sonic points. Using this approach, we revisit the problem of magnetically controlled accretion flow in a dipole geometry, and then generalize the treatment to consider magnetic fields with multiple components, including dipole, octupole, and split monopole contributions. This approach can be generalized further to consider more complex magnetic field configurations. Observations indicate that accreting young stars have substantial dipole and octupole components, and that accretion flow is transonic. If the effective equation of state for the fluid is too stiff, however, the flow cannot pass smoothly through the sonic points in steady state. For a multipole field of order l, we derive a general constraint on the polytropic index, n > l + 3/2, required for steady transonic flow to reach free-fall velocities. For octupole fields, inferred on surfaces of T Tauri stars, the index n > 9/2, so that the flow must be close to isothermal. The inclusion of octupole field components produces higher densities at the stellar surface and smaller areas for the hot spots, which occur at higher latitudes; the magnetic truncation radius is smaller (larger) for octupole components that are aligned (anti-aligned) with the stellar dipole. This contribution thus increases our understanding of magnetically controlled accretion for young stellar objects and can be applied to a variety of additional astrophysical problems.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Development of Advanced Nb 3 Sn Superconductors for Future Energy-Frontier Colliders

Development of Advanced Nb 3 Sn Superconductors for Future Energy-Frontier Colliders: • Present record of particle collision energy: 13 TeV, by the LHC. • Further push of the energy frontier requires higher magnetic field in circular accelerators: E (in TeV) = 0.3R (in km)•B (in T). • The proposed Future Circular Collider (FCC) plans to increase B from 8 T (in LHC) to 16 T. • Nb3Sn wires will be the workhorse conductor for building dipole and quadrupole magnets for FCC.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Design, Fabrication, and Testing of a 1.9 m Long, 16.5 mm Period NbTi Superconducting Undulator for the Advanced Photon Source Upgrade

Superconducting undulator (SCU) technology has been in use at the Advanced Photon Source since 2013. Due to the successful and reliable operation of the existing SCUs, the Advanced Photon Source upgrade project has decided to expand the use of NbTi-based SCUs. The first new magnets to be designed and fabricated are 1.9 m long with a period length of 16.5 mm. NbTi superconductor is used for coil winding and there are four separate coils wound on the mandrel to produce the main undulator field along with end compensation and distributed dipole compensation. The magnetic design, fabrication details, assembly, and testing are described in detail.

NbTi.↗
DOE OSTI2015

The magnetic particle in a box: Analytic and micromagnetic analysis of probe-localized spin wave modes

The dipole field from a probe magnet can be used to localize a discrete spectrum of standing spin wave modes in a continuous ferromagnetic thin film without lithographic modification to the film. Obtaining the resonance field for a localized mode is not trivial due to the effect of the confined and inhomogeneous magnetization precession. We compare the results of micromagnetic and analytic methods to find the resonance field of localized modes in a ferromagnetic thin film, and investigate the accuracy of these methods by comparing with a numerical minimization technique that assumes Bessel function modes with pinned boundary conditions. We find that the micromagnetic technique, while computationally more intensive, reveals that the true magnetization profiles of localized modes are similar to Bessel functions with gradually decaying dynamic magnetization at the mode edges. We also find that an analytic solution, which is simple to implement and computationally much faster than other methods, accurately describes the resonance field of localized modes when exchange fields are negligible, and demonstrating the accessibility of localized mode analysis.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Multipole approximation of special nonlinear magnets for the IOTA ring

All existing focusing optics for accelerators are built to be "linear", i.e. the transverse focusing force is proportional to the particle displacement from the closed orbit. Such approach is used in order to make trajectories stable in the entire area of phase space, because the potential describing linear focusing is integrable and does not produce chaotic motion. Technically, the needed field is achieved with the help of dipole and quadrupole magnets. But the linear motion is unstable to perturbations in the focusing fields and excludes any betatron tune spread over particle's energy, which is beneficial for the beam stability. Moreover, the focusing strength depends on the particle's energy deviation from the designed one. These undesired effects are usually suppressed by the addition of non- linear elements, such as sextupoles and octupoles. Unfortunately, these additions make focusing potential nonintegrabe, leading to the limitation of stable phase space area. Recent research showed, that there exist non-linear potentials that, nevertheless, are fully integrable [1, 2]. Thus, there is an opportunity to create stable non-linear focusing optics that provides high betatron tune spread and mitigate magnetic field errors. This approach is to be implemented in electron storage ring called Integrable Optics Test Accelerator (IOTA) at Fermilab [3]. The main goal is to show the possibility to implement the nonlinear integrable system in a realistic accelerator design. Development of a magnet, which creates exact non-linear potential, is a technically complicated task, that takes much time and efforts. However, it is possible to expand the non- linear potential into superposition of multipoles of even orders (i.e quadrupole, octupole, etc.). Though this series is not convergent in the entire space, a few low order terms can be used to model the true potential in some limited area. In turn, each of the multipole potentials can be generated by speci ed electrical current in PCB coiled on the surface of storage ring's vacuum tube. Such approach is much cheaper than the creation of a magnet of solid iron with high current coil and faster than the development of \exact" non-linear magnet, but it can help identify some features of non-linear integrable optics application. The goal of this research work is to find analytically the angular distribution of electrical current on the surface of the vacuum tube, which creates inside it multipole potential with given parameters. Hereafter, there is the task to develop a model of flexible printed circuit board (PCB), which could be coiled around the vacuum tube in order to provide the desired current distribution.

Vorobev, Viktor↗