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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Crystallographic and magnetic properties of the spinel-type ferrites Zn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} (0.0 ≤ x ≤ 0.75)

Ultrahigh frequencies (UHF) have applications in signal and power electronics to minimize product sizes, increase production quantity and lower manufacturing cost. In the UHF range of 300 MHz to 3 GHz, ferrimagnetic iron oxides (ferrites) are especially useful because they combine the properties of a magnetic material with that of an electrical insulator. Ferrites have much higher electrical resistivity than metallic ferromagnetic materials, resulting in minimization of the eddy current losses, and total penetration of the electromagnetic (EM) field. Hence ferrites are frequently applied as circuit elements, magnetic storage media like read/write heads, phase shifters and Faraday rotators. The electromagnetic properties of ferrites are affected by operating conditions such as field strength, temperature and frequency. The spinel system Zn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} (x=0.0, 0.25, 0.50 and 0.75) has been prepared by the standard solid state sintering method. X-ray and neutron powder diffraction measurements were performed at room temperature. Neutron diffraction data analysis confirms the cubic symmetry corresponding to the space group Fd3m. The distribution of three cations Zn{sup 2+}, Co{sup 2+} and Fe{sup 3+} over the spinel lattice and other crystallographic parameters like lattice constant, oxygen position parameter, overall temperature factor and occupancies of different ions in different lattice sites for the samples have been determined from the analysis of neutron diffraction data. The lattice constant increases with increasing Zn content in the system. The magnetic structure was found to be ferrimagnetic for the samples with x≤0.50. Magnetization measurements show that with the increase of Zn content in the system the value of saturation magnetization first increases and then decreases. The variation of the magnetic moment with Zn substitution has been discussed in terms of the distribution of magnetic and non-magnetic ions over the A and B sub-lattices and their exchange coupling.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Features of Formation of the Magnetocaloric Phenomena in Mn{sub 1–} {sub t}Ti{sub t}As and Mn{sub 1–} {sub x}Cr{sub x}NiGe Systems

The magnetocaloric properties of the systems exhibiting magnetic (paramagnetism (PM)–ferromagnetism (FM)) and structural (hexagonal lattice–orthorhombic lattice) transitions separated (overlapped) in temperature are analyzed in terms of a model of interacting parameters of magnetic and structural orders. It is shown that the magnetocaloric characteristics of the system can increase or decrease during overlapping of the structural (P6{sub 3}/mmc–P{sub nma}) and magnetic (PM–FM) transitions in the dependence of the character of combination of the low-symmetric orthorhombic (P{sub nma}) and high-symmetric hexagonal (P6{sub 3}/mmc) phases with a ferromagnetic order.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Thermal Analysis of a Helical Superconducting Undulator Cryostat

A novel cryocooler-cooled helical superconducting undulator (HSCU) was built and installed in the Advanced Photon Source (APS) storage ring and has been in operation since January 2018. The new cryostat for the HSCU is a major improvement of the cryogenic system used for the existing APS planar superconducting undulators. In both systems, superconducting magnets are cooled independently from the beam chamber by liquid helium (LHe) passing through a channel in the magnet/mold assembly. The original planar undulator cryostat consists of three thermal circuits: the outer shield circuit to cool both the warm part of the magnet current leads and the outer shield, the beam chamber cooling circuit to cool the beam chamber and the inner shield, and the magnet cooling circuit to cool the magnets and the LHe tank. On the other hand, the new system consists of only two thermal circuits: the thermal shield circuit to cool the beam chamber, the shield, and the warm part of the magnet leads; and the magnet cooling circuit to cool the LHe tank and the magnet/mold assembly. An finite element analysis-based thermal model of the new HSCU cryostat was developed while the cryogenic performance of the HSCU was measured in a series of standalone tests as well as after installation in the storage ring. This paper presents a thermal analysis of the new HSCU cryostat and, in particular, a comparison of calculated and measured temperatures as well as the excess cooling capacity of the new cryostat in static and dynamic (beam-induced heating) modes.

cryocooler↗
DOE OSTI2014

High-frequency fluctuation measurements by far-infrared laser Faraday-effect polarimetry-interferometry and forward scattering system on MST

Magnetic fluctuation-induced transport driven by global tearing modes has been measured by Faraday-effect polarimetry and interferometry (phase measurements) in the MST reversed field pinch. However, the role of small-scale broadband magnetic and density turbulence in transport remains unknown. In order to investigate broadband magnetic turbulence, we plan to upgrade the existing detector system by using planar-diode fundamental waveguide mixers optimized for high sensitivity. Initial tests indicate these mixers have ×10 sensitivity improvement compared to currently employed corner-cube Schottky-diode mixers and ×5 lower noise. Compact mixer design will allow us to resolve the wavenumbers up to k ∼ 1–2 cm{sup −1} for beam width w = 1.5 cm and 15 cm{sup −1} for beam width w = 2 mm. The system can also be used to measure the scattered signal (amplitude measurement) induced by both plasma density and magnetic fluctuations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Inelastic Neutron Scattering Data for Ba₃Zn(Ru₀.₁Sb₁.₉)O₉

This dataset contains inelastic neutron scattering measurements on the magnetically dilute compound Ba₃Zn(Ru₀.₁Sb₁.₉)O₉, collected at the Spallation Neutron Source using the Cold Neutron Chopper Spectrometer (CNCS) and the SEQUOIA Fine-Resolution Fermi Chopper Spectrometer. The sample consists of nominally 5% magnetic Ru⁵⁺ ions (S = 3/2) randomly substituted into a diamagnetic Sb⁵⁺ matrix. Measurements were performed at base temperature (2–5 K) and 300 K using multiple incident energies (1.00, 3.32, 12.0, and 100 meV) to resolve magnetic excitations from isolated monomers and small Ru clusters (dimers, trimers, etc.). The dataset includes raw event-mode files, momentum- and energy-resolved spectra, and supporting metadata for instrument configuration, sample environment, and reduction parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Recovering the Waste Energy from the Electron-Ion Collider Cooling Water Systems

While only a fraction of the electricity required for the EIC goes into the collision itself, most of the energy ultimately ends up being rejected to the environment via the infrastructure cooling systems. The energy utilized by the RF amplifiers, power supplies, magnets, vacuum systems, and cryogenics systems is rejected to the cooling towers that ultimately dissipate the energy to the atmosphere. Current estimates indicate approximately 50 MW of heat is dissipated at a low temperature by the cooling towers. This technical note is prepared to conceptually demonstrate that feasible options exist to recover the low temperature energy from the EIC cooling water systems.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Formation of a magnetic hole above the mirror-instability threshold in a plasma with sloshing ions

Within the framework of paraxial approximation it is shown that in an anisotropic plasma with sloshing ions confined an open-ended system a magnetic hole is formed near the turning point of the sloshing ions above the threshold of the mirror instability. The magnetic field experiences a jump at the hole boundary from the side of the magnetic mirror. For a small excess over the mirror instability threshold, the surface of the discontinuity has the shape of a truncated paraboloid, and the magnitude of the magnetic field jump at the system axis is proportional to the radius of the hole and gradually decreases to zero away of the axis. It is argued that disappearance of the magnetic hole because of the widening of the sloshing ions angular spread in the course of the neutral beam injection results in abrupt anticorrelated changes of the diamagnetic signals measured near the turning point of the sloshing ions and near the midplane of the gas-dynamic trap.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Synthesis of magnetic and upconversion nanocapsules as multifunctional drug delivery system

Multifunctional hollow nanocapsules with magnetic and upconversion luminescence properties were synthesized. Hollow Fe{sub 3}O{sub 4}@SiO{sub 2} was firstly prepared by using rodlike β-FeOOH as the template followed by silica coating, calcinations and reduction. Then Fe{sub 3}O{sub 4}@SiO{sub 2}@α-NaYF{sub 4}:Yb{sup 3+},Er{sup 3+} nanocapsules (FeSiUCNP) were synthesized by the hydrothermal transformation of the Y(Yb{sup 3+}, Er{sup 3+})(OH)CO{sub 3} (YOC) deposited onto the surface of nanocapsules through a urea-assisted homogeneous precipitation method. The hollow nanocapsules with porous structure provide space and entrance for the drug molecules. Due to the outside shell of α-NaYF{sub 4}:Yb{sup 3+}, Er{sup 3+}, the nanomaterial shows upconverting red emission upon 980 nm NIR-light excitation. Moreover, the nanocomposites with hollow magnetite core exhibit a high relaxivity with r{sub 2} value of 183 mM{sup −1} s{sup −1}, which reveal the potential as T{sub 2}-weighted contrast agents for magnetic resonance imaging (MRI). The as-prepared nanocapsules can be performed as anti-cancer drug carriers for investigation of drug loading/release properties, which demonstrated a sustained drug release pattern and a comparable cytotoxicity with free doxorubicin (DOX). The multifunctional nanocapsules incorporated upconverting luminescence, T{sub 2}-weighted MRI imaging and drug targeting delivery modalities have great potential for theranostic applications in cancer treatment. - Graphical abstract: Multifunctional hollow nanocapsules with upconverting luminescence, T{sub 2}-weighted MRI imaging and drug targeting delivery modalities were synthesized for cancer treatment. - Highlights: • Multifunctional porous Fe{sub 3}O{sub 4}@SiO{sub 2}@α-NaYF{sub 4}:Yb{sup 3+},Er{sup 3+} nanocapsules were synthesized. • The nanocapsules show upconverting red emission upon 980 nm NIR-light excitation. • The nanocapsules exihibit potential as T{sub 2}-weighted contrast agents for MRI. • The DOX loaded nanocapsules demonstrated a comparable cytotoxicity with free DOX.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

INDUCED MAXIMUM MAGNETIC FIELD IN COSMIC OUTFLOW SYSTEM BY A RELATIVISTIC CURRENT FILAMENTATION INSTABILITY: EXACT ANALYTICAL MODEL

We present an analytical study of current filamentation instability (CFI) in a fully relativistic cold plasma system, including arbitrary currents. For our purposes, we employ the cold fluid equations, together with Maxwell's equations as well as the plasma shell concept and boost frame method, to obtain an exact solution of the instability growth rate. A simple relation is found for the maximum growth rate of the CFI (for any arbitrary current system), which remarkably is used to calculate the large magnitude of an induced magnetic field in astrophysical environments such as active galactic nuclei (AGNs), microquasars, supernova remnants (SNRs), and stellar winds. We find that the magnetic field is amplified in the SNR up to the level required to justify the recent discovery of the year-scale variability in the X-ray emission of SNRs. Also, the maximum magnetic field of two and three orders higher (or two orders lower) than that of the SNR has been derived for microquasars and AGNs (or stellar winds), respectively. Moreover, making use of the exact analytical solution of the CFI, it is shown that the maximum magnetic field up to around 10{sup 8} G can be detected from a classical cold counterstreaming system after a saturation time.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Final Report for contract DE-SC0010151, "A Cost-Effective Oxygen Separation System Based on Open Gradient Magnetic Field by Polymer Beads"

At present much of the oxygen enrichment market is based primarily on cryogenic systems, ion transport membranes made of ceramics, or polymer membranes technologies. All these methods have some positive and some negative attributes, but remain too expensive for the cost effective production of pure oxygen needed for clean renewable energy conversion projects. In a very successful Phase I period, the ITN-TAMU team accomplished the completion of most of the sub-tasks on oxygen separation based on our proposed magnetic field gradients. Theoretical and computer simulation data under different conditions of flow rates, magnetic flux, magnetic beads packing density, pressure and temperature have resulted very valuable observations. Chitosan based polymer magnetic beads showed the best results for uniformity and column packing. Due to limited magnetic force of 1 Tesla, we were restricted to use only single small column of magnetic beads and limited air pressure with controlled flow rate. We also fabricated smaller sized beads column with metal and clear plastic frames to be used for more concentrated packed capacity. Beads made with rare earth Neodymium were not uniform and were quite brittle. Different surfactants have minimized the effect of the de-aggregation of polymer magnetic beads. This Phase I development work also included overcoming key packaging hurdles such as high packing capacity of magnetic polymer beads and formation of consistent batch of magnetic beads. Market and commercialization studies were also initiated to show that there is a growing market for the proposed cost-effective oxygen separation system for energy conversion projects.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2025

Challenges in Continuous In-Field Critical Current Testing of High-Temperature Superconducting Tapes: Thermal and Mechanical Perspectives

High-temperature superconductors (HTS) are essential for ultra-high-field applications requiring exceptional current-carrying capacity under extreme conditions. However, systematic characterization of critical current in long-length conductors remains challenging due to complex thermal, electromag netic, and mechanical interactions during continuous testing. This study reports the development of a continuous in-field magnetization testing system for position-dependent critical current measurement in HTS tapes at 20 K under 7.5 T fields applied normal to the tape plane, enabling identification of performance-limiting regions that could compromise magnet stability. Here, the system addresses two fundamental challenges inherent to cryogenic reel to-reel testing. First, thermal management requires continuous cooling of a moving conductor to 20 K, achieved through liquid nitrogen precooling combined with a 100 W@20 K Gifford McMahon cryocooler. Second, screening currents in high fields generate Lorentz forces that induce twisting, bowing, and potential delamination. To mitigate these risks, we propose mechanical reinforcement and active current density suppression strategies. Numerical simulations using the stream function formulation reveal four primary failure modes: frictional heating at guide interfaces, unstable equilibria causing deformation, transverse current-induced stresses at guide transitions, and unsupported forces in vertical spans. Our mitigation strategies include PTFE coated guides to minimize friction, spring-loaded stabilization mechanisms to maintain tape alignment, controlled pre-heating using the liquid nitrogen thermal jacket to suppress critical current at stress points, and optimized guide positioning to minimize force accumulation. The experimental system is nearing completion, with testing planned to commence within two months. Preliminary validation at 65 K under 0.5 T demonstrates strong correlation between simulation-predicted mechanical instabilities and observed critical current variations during conductor tran sitions through the measurement region. These findings establish a robust foundation for quality assurance protocols essential to next-generation superconducting magnet applications.

Chen, Siwei [Princeton Plasma Physics Laboratory (↗
DOE OSTI2018

The magnetic order of a manganese vanadate system with two-dimensional striped triangular lattice

Results of magnetization and neutron diffraction measurements of the manganese vanadate system Mn 5 (VO 4 ) 2 (OH) 4 are reported. The crystal structure of this compound contains triangular [Mn 3 O 13 ] building blocks that produce two-dimensional Mn 2+ magnetic networks with striped triangular topologies. The Mn sheets are connected through the nonmagnetic vanadate tetrahedra extending along the a-axis. Magnetization measurements performed on single crystals reveal the onset of a long-range antiferromagnetic order below approximately 45 K. The magnetic structure is Néel-type with nearest-neighbor Mn atoms coupled via three or four antiferromagnetic bonds. The magnetic moments are confined within the layers and are oriented parallel to the b direction. In conclusion, the magnitudes of ordered moments are reduced, presumably by geometrical frustration and the low-dimensionality of the lattice structure.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Measurement of the Magnet Blocks for SSRF Insertion Devices

Two in-vacuum undulators IVU25s and one elliptically polarized undulator EPU100 have been developed for SSRF. Two IVU25s with the same hybrid design contain about 640 Sm{sub 2}Co{sub 17} magnet blocks and the dimension of blocks is 65 Wx25 Hx9 D. The EPU100 of the APPLE-II type contains about 690 NdFeB magnet blocks with the dimension of 35 Wx35 Hx25 D. This paper describes the magnetic measurements of these magnet blocks with the Helmholtz coil measurement system for IVU25 magnet blocks and the Hall probe measurement system for EPU100 magnet blocks. The measured maximum magnetic moment deviation and the maximum angle deviation are less than {+-}1.0% and 1.1 deg. respectively both for Sm{sub 2}Co{sub 17} blocks and NdFeB blocks and satisfy the specifications of undulators.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Initial state q q g correlations as a background for the chiral magnetic effect in collision of small systems

Motivated by understanding the background to chiral magnetic effect in proton-nucleus collisions from first principles, we compute the three particle correlation in the projectile wave function. We extract the correlations between two quarks and one gluon in the framework of the color glass condensate. This is related to the same-charge correlation of the conventional observable for the chiral magnetic effect. We show that there are two different contributions to this correlation function. One contribution is rapidity-independent and as such can be identified with the pedestal; while the other displays rather strong rapidity dependence. The pedestal contribution and the rapidity-dependent contribution at large rapidity separation between the two quarks result in the negative same charge correlations, while at small rapidity separation the second contribution changes sign. We argue that the computed initial state correlations might be partially responsible for the experimentally observed signal in proton-nucleus collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Influence of geometry on liquid oxygen magnetohydrodynamics

Magnetic fluid actuators have performed well in industrial applications, but have a limited temperature range due to the freezing point of the carrier fluid. Liquid oxygen (LOX) presents a pure, paramagnetic fluid suitable for use in a cryogenic magnetic fluid system; therefore, it is a potential solution to increasing the thermal range of magnetic fluid technology without the need for magnetic particles. The current study presents experimental work regarding the influence of geometry on the dynamics of a LOX slug in a 1.9 mm quartz tube when pulsed by a solenoid in a closed volume. A numerical analysis calculated the optimal solenoid geometry and balanced the magnetic, damping, and pressure forces to determine optimal slug lengths. Three configurations comprised the experiment: (1) a 24-gauge wire solenoid with an optimized 2.7 cm length slug, (2) a 30-gauge wire solenoid with an optimized 1.3 cm length slug, and (3) a 30-gauge wire solenoid with a nonoptimized 2.5 cm length slug. Typically, the hydrodynamic breakdown limit is calculated and used to determine the system range; however the experiment showed that the hydrodynamic breakdown limit was never reached by the slug. This implied that, instead, the system range should factor in a probabilistic risk of failure calculated as a function of the induced pressure change from its oscillations. The experimental data were also used to establish a nondimensional relationship between the maximum displacement and initial magnetic pressure on the slug. The average initial velocity of the slug was found to be proportional to the initial magnetic pressure, Mason number, and slug length. The results of this study can be used in the design and optimization of a LOX fluid system for space or low-temperature applications. (author)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Design, construction, and testing of no-insulation small subscale solenoids for compact tokamaks

Fusion energy systems studies (FESS) for next-step devices based on the most promising magnetic configurations indicate that high magnetic fields and high current density for magnet coil systems may reduce device size and lower the cost. High current density and radiation resistant fusion magnets are particularly beneficial for low cost, low aspect ratio compact reactor designs such as Fusion Nuclear Science Facility (FNSF), Fusion Pilot Plant (FPP) of low-aspect ratio spherical tokamak (ST) or compact stellarators. Unlike typical high field magnets for nuclear magnetic resonance (NMR), magnetic resonance imaging (MRI), or high energy physics research applications, neutron irradiation damage to organic insulations in the coil winding pack is a critical issue for next generation fusion reactors where orders of magnitude higher neutron fluence than those in present experimental reactors such as ITER are expected. Moreover, a high coil winding pack current density is needed for high field magnets in low cost, compact radial build next step fusion reactors. The slow current charging time, however, is an issue in fully non-insulated coils. In this work, we present the design, construction and testing of subscale Nb3Sn solenoids, up to half the diameter of the central solenoid (CS) for National Spherical Torus Experiment (NSTX), with and without inter-layer insulation for enhancing radiation resistance while improving the winding pack current density and coil performance. The major radius for the NSTX/NSTX-Upgrade (reference for compact ST) is 0.854/0.934 meter, and 4.8 meters for FNSF. The magnetic field for NSTX/NSTX-U at the plasma center is 0.6/1 Tesla and 9 Tesla for FNSF. The inner diameter of the central solenoid coil is 0.2/0.4 meter for NSTX/NSTX-U and 1.2 meters for FNSF. The current charging and discharging behavior of the prototype solenoids was investigated to quantify performance advantages of a simplified coil fabrication without error-prone vacuum pressure impregnation (VPI) for the removal of epoxy organic insulation. Scalability of the no insulation concept for fusion can be addressed via engineered coating for novel insulation on contact resistance or intra-layer no insulations. Radiation resistance and coil winding efficiency were significantly improved in the no insulation coils for next step compact fusion reactors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effect Laws of Different Factors on Levitation Characteristics of High-T{sub c} Superconducting Maglev System with Numerical Solutions

The interaction between the high-temperature superconducting (HTS) bulk and permanent magnet guideway (PMG) has been a topic among the existing HTS magnetic levitation systems. Up to now, the theories about the electromagnetic and force characteristics have been relatively consummated. Here, using the finite element model by COMSOL Multiphysics 5.3a, we investigated the impact of the intrinsic and external factors on the levitation characteristics of HTS maglev systems, the application laws are concluded. Factors including the critical current density and geometric dimensions of the bulk superconductor, as well as the moving velocity, are discussed. The effects of the multiple back and forth movements are also analyzed. By comparing calculation results of the distributions of the induced current and the levitation force of the bulk superconductor, we can clearly confirm the effect laws of various factors on the electromagnetic characteristics and levitation force. These observations support the physical parameters that are difficult to be tested by experiments. And they also have a significant contribution to the experimental condition selections and optimization of the high-temperature superconducting magnetic levitation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗