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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

First Search for Axion Dark Matter with a MADMAX Prototype

This Letter presents the first search for dark matter axions with mass in the ranges 76.56 to 76.82 μ⁢eV and 79.31 to 79.53 μ⁢eV using a prototype setup for the MAgnetized Disk and Mirror Axion eXperiment (MADMAX). The experimental setup employs a dielectric haloscope consisting of three sapphire disks and a mirror to resonantly enhance the axion-induced microwave signal within the magnetic dipole field provided by the 1.6 T Morpurgo magnet at CERN. Over 14.5 days of data collection, no axion signal was detected. A 95% CL upper limit on the axion-photon coupling strength down to |𝑔 𝑎⁢𝛾 |∼2×10 −11 GeV −1 is set in the targeted mass ranges, surpassing previous constraints, assuming a local axion dark matter density 𝜌 𝑎 of 0.3 GeV/cm 3 . This study marks the first axion dark matter search using a dielectric haloscope.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Renewal: Coherent control of spin states in organic electronics – discovery and investigation of complex room-temperature magnetic quantum excitations

In the course of four funding cycles of this project, its research focused on the exploration and understanding of spin-dependent electronic processes in organic semiconductors. It aimed to investigate the potential of harnessing the spin degree of freedom in organic materials for various applications such as spin electronics, quantum information, sensors, and as well as quantum coherent spin phenomena of charge carrier states in organic semiconductors, with the aim to develop room-temperature-based quantum applications. Specifically, the project aimed to: Apply new diagnostic tools, i.e. spin spectroscopy techniques, for paramagnetic charge carrier states in organic semiconductors, based on coherent control with pulsed electron spin resonance to understand spin relaxation and spin mixing mechanisms in organic semiconductor materials and devices such as OLEDs. Explore the nature of charge carrier spin-coupling and pathways for its manipulation to control the physical behaviors of these materials. This involves investigating spin interactions through materials structure, composition, morphological dependencies, isotopic effects, and externally applied electric and magnetic fields, with the goal to manipulate electrical and optical material properties by adjusting spin-orbit, spin-dipolar, spin-exchange, as well as spin-hyperfine interactions to open up this materials class for new applications. Study spin-dependent charge carrier transport and recombination and how these observables are governed by spin-propagation, especially coherent spin propagation as well as collective spin-effects such as the spin-Dicke effect and resonant multi-photon magnetic dipole transitions. The project utilized pulsed electrically detected magnetic resonance (pEDMR) and pulsed optically detected magnetic resonance (pODMR) techniques over a wide frequency range. These techniques enabled the observation and quantification of various spin-spin coupling types, including spin-exchange, spin-dipolar, hyperfine, and spin-orbit interactions. The project will leverage low- to mid-frequency pEDMR/pODMR facilities and collaboration with the National High Magnetic Field Laboratory.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Commissioning the Super High Momentum Spectrometer in Hall C at Jefferson Lab

The Super High Momentum Spectrometer (SHMS) is a new spectrometer installed in Hall C at Jefferson Lab that can detect particles over a range of central momenta from 2-11 GeV/c and scattering angles from 5.5 to 40 degrees. Jefferson Lab delivers a high intensity electron beam with an energy up to 11 GeV to fixed targets in Hall C. The SHMS is a highly precise and essential upgrade for the 12 GeV Jefferson Lab physics program. Its beam line consists of a dipole magnet with a 3-degree horizontal bend, three quadrupole magnets for horizontal and vertical focusing of the beam, and the spectrometer dipole capable of a 4 T central magnetic field and 18.4-degree bend angle. Measurements in Hall C can be taken with the SHMS independently or in coincidence with the existing High Momentum Spectrometer (HMS). The SHMS was installed in the spring of 2017 and commissioned during the fall 2017/winter 2018 using a range of electron beam energies. This talk summarizes the initial results of the optics tuning of the SHMS and the performance during recent experimental running to include initial elastic hydrogen scattering measurements.

Szumila-Vance, Holly↗
DOE OSTI2010

SEARCHING FOR THE PULSAR IN G18.95-1.1: DISCOVERY OF AN X-RAY POINT SOURCE AND ASSOCIATED SYNCHROTRON NEBULA WITH CHANDRA

Using the Chandra X-ray Observatory, we have pinpointed the location of a faint X-ray point source (CXOU J182913.1-125113) and an associated diffuse nebula in the composite supernova remnant (SNR) G18.95-1.1. These objects appear to be the long-sought pulsar and its wind nebula. The X-ray spectrum of the point source is best described by an absorbed power-law model with {Gamma} = 1.6 and an N{sub H} of {approx}1 x 10{sup 22} cm{sup -2}. This model predicts a relatively low unabsorbed X-ray luminosity of about L{sub X} (0.5-8.0 keV) {approx_equal} 4.1 x 10{sup 31} D{sup 2} {sub 2} erg s{sup -1}, where D{sub 2} is the distance in units of 2 kpc. The best-fit model of the diffuse nebula is a combination of thermal (kT = 0.48 keV) and non-thermal (1.4 {<=} {Gamma} {<=} 1.9) emission. The unabsorbed X-ray luminosity of L{sub X} {approx_equal} 5.4 x 10{sup 33} D{sup 2}{sub 2} erg s{sup -1} in the 0.5-8 keV energy band seems to be largely dominated by the thermal component from the SNR, providing 87% of L{sub X} in this band. No radio or X-ray pulsations have been reported for CXOU J182913.1-125113. If we assume an age of {approx}5300 yr for G18.95-1.1 and use the X-ray luminosity for the pulsar and the wind nebula together with the relationship between spin-down luminosity (via magnetic dipole radiation) and period, we estimate the pulsar's period to be P {approx_equal} 0.4 s. Compared to other rotation-powered pulsars, a magnetic field of 2.2 x 10{sup 13} G is implied by its location in the P- P-dot diagram, a value which is close to that of the quantum critical field.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Incorporation of drift loss cone effects on the trapping of an artificial radiation belt into LANL's modeling capability

Los Alamos National Laboratory has developed an end-to-end model that quantifies the total ionizing dose that a shielded component on a space asset will accrue due to interactions with trapped beta-decay electrons produced after a high-altitude nuclear explosion. The model consists of three major components: initial trapping, spatio-temporal evolution of the trapped population, and interaction of the evolving trapped population with a space asset to produce total ionizing dose. The initial trapping module calculates the fraction of betas produced by radioactive decay of nuclear fission products that will be trapped in the magnetic field surrounding Earth for at least one drift around Earth. Previously, the initial trapping calculation assumed a centered dipole magnetic field model whereas we know that Earth’s magnetic field is offset from its geographic center and has higher-order non-dipole terms. Both the offset and the higher-order terms are captured in the International Geomagnetic Reference Field (IGRF) internal field model. In a centered dipole, the electrons that are trapped on a magnetic field line at one longitude will be trapped at all other longitudes as they drift around Earth due to azimuthal symmetry of the field, but the offset and higher-order terms of the IGRF field affects the drift of the trapped electrons and causes some that are trapped at one longitude to be lost at other longitudes. These electrons are called "quasi-trapped" and are said to be in the drift loss cone since they will be lost during their first drift around Earth. In this paper we report on the effect of incorporating the drift of electrons around Earth using the IGRF field on the trapping fraction as compared to using a centered dipole. Here, we find that the new, more accurate, methodology produces higher trapping fractions for bursts above the South Atlantic Anomaly, a region of low magnetic field strength, and lower trapping fractions for bursts in regions with higher magnetic field strength than expected from a centered dipole.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

On the Magnetic Field of the Ultraluminous X-Ray Pulsar M82 X-2

The discovery of the ultraluminous X-ray pulsar M82 X-2 has stimulated lively discussion on the nature of the accreting neutron star. In most of the previous studies the magnetic field of the neutron star was derived from the observed spin-up/down rates based on the standard thin, magnetized accretion disk model. However, under super-Eddington accretion the inner part of the accretion disk becomes geometrically thick. In this work we consider both radiation feedback from the neutron star and the sub-Keplerian rotation in a thick disk and calculate the magnetic moment–mass accretion rate relations for the measured rates of spin change. We find that the derived neutron star's dipole magnetic field depends on the maximum accretion rate adopted, but is likely ≲10{sup 13} G. The predicted accretion rate change can be used to test the proposed models by comparison with observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Electronic excitations and spin interactions in chromium trihalides from embedded many-body wavefunctions

Although chromium trihalides are widely regarded as a promising class of two-dimensional magnets for next-generation devices, an accurate description of their electronic structure and magnetic interactions has proven challenging to achieve. Here, we quantify electronic excitations and spin interactions in CrX 3 (X = Cl, Br, I) using embedded many-body wavefunction calculations and fully generalized spin Hamiltonians. We find that the three trihalides feature comparable d-shell excitations, consisting of a high-spin 4 A 2 ($t^3_{2g}$$e^0_g$) ground state lying 1.5–1.7 eV below the first excited state 4 T 2 ($t^2_{2g}$$e^1_g$). CrCl 3 exhibits a single-ion anisotropy A sia = - 0.02 meV, while the Cr spin-3/2 moments are ferromagnetically coupled through bilinear and biquadratic exchange interactions of J 1 = - 0.97 meV and J 2 = - 0.05 meV, respectively. The corresponding values for CrBr 3 and CrI 3 increase to A sia = -0.08 meV and A sia = - 0.12 meV for the single-ion anisotropy, J 1 = -1.21 meV, J 2 = -0.05 meV and J 1 = -1.38 meV, J 2 = -0.06 meV for the exchange couplings, respectively. We find that the overall magnetic anisotropy is defined by the interplay between A sia and A dip due to magnetic dipole–dipole interaction that favors in-plane orientation of magnetic moments in ferromagnetic monolayers and bulk layered magnets. The competition between the two contributions sets CrCl 3 and CrI 3 as the easy-plane (A sia + A dip >0) and easy-axis (A sia + A dip <0) ferromagnets, respectively. The differences between the magnets trace back to the atomic radii of the halogen ligands and the magnitude of spin–orbit coupling. Our findings are in excellent agreement with recent experiments, thus providing reference values for the fundamental interactions in chromium trihalides.

36 MATERIALS SCIENCE↗
DOE OSTI2010

The P-bar ANDA Experiment at FAIR

The P-bar ANDA experiment (Pbar ANnihilations at DArmstadt) is a next generation hadron physics detector under design for the Facility for Antiproton and Ion Research (FAIR) at Darmstadt, Germany. It will be using cooled antiproton beams with an energy between 1.5 GeV and 15 GeV interacting with various internal targets.The experiment is focusing on hadron spectroscopy, in particular the search for exotic states in the charmonium region, on the interaction of charm hadrons with the nuclear medium and on double-hypernuclei.With physics requiring precise partial wave analysis the experiment has almost 4{pi} acceptance, a solenoid magnet for high p{sub T} tracks and a dipole magnet for the forward part of reaction products. A silicon vertex detector surrounds the interaction point. In both spectrometer parts tracking, charged particle identification, electromagnetic calorimetry and muon identification are available.The experiment is being designed to fully exploit the extraordinary physics potential arising from the availability of high-intensity, cooled antiproton beams.Significant progress beyond the present understanding of the field is expected thanks to improvements in statistics and precision of the data.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Accelerator Magnet Development Based on COMB Technology with STAR Wires

This paper reports progress in the development of COMB magnet technology with STAR wires. A two-layer dipole magnet with 60 mm clear bore has been recently fabricated and tested in liquid nitrogen. The purpose of the test was to determine what kind of critical current degradation occurs in the process of winding the STAR wire into the COMB structure.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Probing top-Z dipole moments at the LHC and ILC

We investigate the weak electric and magnetic dipole moments of top quark-Z boson interactions at the Large Hadron Collider (LHC) and the International Linear Collider (ILC). Their vanishingly small magnitude in the Standard Model makes these couplings ideal for probing New Physics interactions and for exploring the role of top quarks in electroweak symmetry breaking. In our analysis, we consider the production of two top quarks in association with a Z boson at the LHC, and top quark pairs mediated by neutral gauge bosons at the ILC. These processes yield direct sensitivity to top quark-Z boson interactions and complement indirect constraints from electroweak precision data. Our computation is accurate to next-to-leading order in QCD, we include the full decay chain of top quarks and the Z boson, and account for theoretical uncertainties in our constraints. Furthermore, we find that LHC experiments will soon be able to probe weak dipole moments for the first time.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

SIMULATIONS OF WINDS OF WEAK-LINED T TAURI STARS. II. THE EFFECTS OF A TILTED MAGNETOSPHERE AND PLANETARY INTERACTIONS

Based on our previous work, we investigate here the effects on the wind and magnetospheric structures of weak-lined T Tauri stars due to a misalignment between the axis of rotation of the star and its magnetic dipole moment vector. In such a configuration, the system loses the axisymmetry presented in the aligned case, requiring a fully three-dimensional (3D) approach. We perform 3D numerical magnetohydrodynamic simulations of stellar winds and study the effects caused by different model parameters, namely the misalignment angle {theta}{sub t}, the stellar period of rotation, the plasma-{beta}, and the heating index {gamma}. Our simulations take into account the interplay between the wind and the stellar magnetic field during the time evolution. The system reaches a periodic behavior with the same rotational period of the star. We show that the magnetic field lines present an oscillatory pattern. Furthermore, we obtain that by increasing {theta}{sub t}, the wind velocity increases, especially in the case of strong magnetic field and relatively rapid stellar rotation. Our 3D, time-dependent wind models allow us to study the interaction of a magnetized wind with a magnetized extrasolar planet. Such interaction gives rise to reconnection, generating electrons that propagate along the planet's magnetic field lines and produce electron cyclotron radiation at radio wavelengths. The power released in the interaction depends on the planet's magnetic field intensity, its orbital radius, and on the stellar wind local characteristics. We find that a close-in Jupiter-like planet orbiting at 0.05 AU presents a radio power that is {approx}5 orders of magnitude larger than the one observed in Jupiter, which suggests that the stellar wind from a young star has the potential to generate strong planetary radio emission that could be detected in the near future with LOFAR. This radio power varies according to the phase of rotation of the star. For three selected simulations, we find a variation of the radio power of a factor 1.3-3.7, depending on {theta} {sub t}. Moreover, we extend the investigation done in Vidotto et al. and analyze whether winds from misaligned stellar magnetospheres could cause a significant effect on planetary migration. Compared to the aligned case, we show that the timescale {tau}{sub w} for an appreciable radial motion of the planet is shorter for larger misalignment angles. While for the aligned case {tau}{sub w} {approx_equal} 100 Myr, for a stellar magnetosphere tilted by {theta}{sub t} = 30{sup 0}, {tau} {sub w} ranges from {approx}40 to 70 Myr for a planet located at a radius of 0.05 AU. Further reduction on {tau}{sub w} might occur for even larger misalignment angles and/or different wind parameters.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Analysis of Screening Current Effects in a Hybrid Nb$_{3}$Sn/REBCO Superconducting Accelerator Magnet Using a T - A Formulation

To explore the feasibility of using high-temperature superconducting (HTS) REBCO coated conductors in future accelerator magnets, two REBCO flat racetrack coils were fabricated using 4-mm wide EuBCO tapes at the High Energy Accelerator Research Organization (KEK). These coils were tested as an insert inside a Nb$_{3}$Sn common-coil dipole magnet, which provides a background field of up to $\sim$ 9.5T, at the Brookhaven National Laboratory (BNL). REBCO tapes offer exceptionally high critical current density under strong magnetic fields; however, they also exhibit significant magnetization due to screening currents, leading to magnetic field errors. Here, this study presents a 2D finite element model of screening current-induced fields (SCIF) in REBCO coils using the T-A formulation, along with the results obtained. Simulations were then performed for two KEK test cases: one where the REBCO conductors were oriented with the HTS tapes parallel to the background field, and another where the tapes were perpendicular to it. Since screening currents also influence the stress distribution and increase the peak stress in the coils, the mechanical effects of these currents were analyzed. The implications of these simulation and test results for the design of Nb$_{3}$Sn/REBCO superconducting accelerator magnets are discussed.

Accelerator magnets↗
DOE OSTI2024

Progress on the normal conducting magnets for the Electron-Ion Collider

The electron-ion collider (EIC) at Brookhaven National Laboratory (BNL) is designed to deliver a peak luminosity of 1e+34 1/cm2 1/sec. The EIC will take advantage of the existing Relativistic Heavy Ion Collider (RHIC) facility. Two additional rings will be installed: an electron storage ring (ESR) and a rapid cycling electron synchrotron ring (RCS).This paper presents an update on the normal conducting magnet designs required for both the ESR and RCS rings. The ESR will store polarized electron beams up to 18 GeV and utilizes a triplet of dipole magnets to increase the emittance at 5 GeV and generate excess bending to create additional radiation damping to allow a larger beam-beam tune shift. The RCS will accelerate single bunches of spin-polarized electrons at various energies from 5 GeV to 18 GeV, with a ramp rate of 100 ms and 1 Hz repetition rate. Both rings require dipole, quadrupole and sextupole magnets with different specifications.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Origin-independent calculation of quadrupole intensities in X-ray spectroscopy

For electronic excitations in the ultraviolet and visible range of the electromagnetic spectrum, the intensities are usually calculated within the dipole approximation, which assumes that the oscillating electric field is constant over the length scale of the transition. For the short wavelengths used in hard X-ray spectroscopy, the dipole approximation may not be adequate. In particular, for metal K-edge X-ray absorption spectroscopy (XAS), it becomes necessary to include higher-order contributions. In quantum-chemical approaches to X-ray spectroscopy, these so-called quadrupole intensities have so far been calculated by including contributions depending on the square of the electric-quadrupole and magnetic-dipole transition moments. However, the resulting quadrupole intensities depend on the choice of the origin of the coordinate system. Here, we show that for obtaining an origin-independent theory, one has to include all contributions that are of the same order in the wave vector consistently. This leads to two additional contributions depending on products of the electric-dipole and electric-octupole and of the electric-dipole and magnetic-quadrupole transition moments, respectively. We have implemented such an origin-independent calculation of quadrupole intensities in XAS within time-dependent density-functional theory, and demonstrate its usefulness for the calculation of metal and ligand K-edge XAS spectra of transition metal complexes.

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

Electro-optic switching in iron oxide nanoparticle embedded paramagnetic chiral liquid crystal via magneto-electric coupling

The variation in optical texture, electro-optic, and dielectric properties of iron oxide nanoparticles (NPs) embedded ferroelectric liquid crystal (FLC) with respect to change in temperature and electrical bias conditions are demonstrated in the current investigations. Improvement in spontaneous polarization and response time in nanocomposites has been attributed to magneto-electric (ME) coupling resulting from the strong interaction among the ferromagnetic nanoparticle's exchange field (due to unpaired e{sup −}) and the field of liquid crystal molecular director. Electron paramagnetic resonance spectrum of FLC material gives a broad resonance signal with superimposed components indicating the presence of a source of spin. This paramagnetic behavior of host FLC material had been a major factor in strengthening the guest host interaction by giving an additional possibility of (a) spin-spin interaction and (b) interactions between magnetic-dipole and electric-dipole moments (ME effects) in the composite materials. Furthermore, the phenomenon of dielectric and static memory effect in these composites are also observed which yet again confirms the coupling of magnetic NP's field with FLC's director orientation. We therefore believe that such advanced soft materials holding the optical and electrical properties of conventional LCs with the magnetic and electronic properties of ferromagnetic nanoparticles are going to play a key role in the development of futuristic multifunctional optical devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Novel "Straight" Merger for Energy Recovery Linacs

One of the most critical design considerations for an energy recovery linac (ERL) is how to merge the injected bunch onto the linac axis with minimal beam degradation. All merger designs in established and upcoming machines involve significant bending of the injected beam ’ even using a so-called straight merger bends the injected beam several degrees. We propose a merger which reduces the bending of the injected beam by an order of magnitude. By passing both beams through a septum magnet followed by an rf separator cavity with a superimposed dipole magnetic field, the injected beam bends minimally within the cavity, while the recirculated beam bends to align with the linac axis. Here we describe the concept in detail and present simulation results to demonstrate the advantages of such a design, particularly for magnetized beams or minimal energy separation between the injected and recirculated beams. Measurements from an experiment at CBETA evaluating the beam dynamics of the rf separator are presented and compared with simulation results.

Deitrick, K. E.↗
DOE OSTI2011

A Test of HTS Power Cable in a Sweeping Magnetic Field

Short sample HTS power cable composed of multiple 344C-2G strands and designed to energize a fast-cycling dipole magnet was exposed to a sweeping magnetic field in the (2-20) T/s ramping rate. The B-field orientation toward the HTS strands wide surface was varied from 0{sup 0} to 10{sup 0}, in steps of 1{sup 0}. The test arrangement allowed measurement of the combined hysteresis and eddy current power losses. For the validity of these measurements, the power losses of a short sample cable composed of multiple LTS wire strands were also performed to compare with the known data. The test arrangement of the power cable is described, and the test results are compared with the projections for the eddy and hysteresis power losses using the fine details of the test cable structures.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

THE HIDDEN MAGNETIC FIELD OF THE YOUNG NEUTRON STAR IN KESTEVEN 79

Recent observations of the central compact object in the Kesteven 79 supernova remnant show that this neutron star (NS) has a weak dipole magnetic field (a few Multiplication-Sign 10{sup 10} G) but an anomalously large ({approx}64%) pulse fraction in its surface X-ray emission. We explore the idea that a substantial sub-surface magnetic field exists in the NS crust, which produces diffuse hot spots on the stellar surface due to anisotropic heat conduction, and gives rise to the observed X-ray pulsation. We develop a general-purpose method, termed 'Temperature Template with Full Transport' (TTFT), that computes the synthetic pulse profile of surface X-ray emission from NSs with arbitrary magnetic field and surface temperature distributions, taking into account magnetic atmosphere opacities, beam pattern, vacuum polarization, and gravitational light bending. We show that a crustal toroidal magnetic field of order a few Multiplication-Sign 10{sup 14} G or higher, varying smoothly across the crust, can produce sufficiently distinct surface hot spots to generate the observed pulse fraction in the Kes 79 NS. This result suggests that substantial sub-surface magnetic fields, much stronger than the 'visible' dipole fields, may be buried in the crusts of some young NSs, and such hidden magnetic fields can play an important role in their observational manifestations. The general TTFT tool we have developed can also be used for studying radiation from other magnetic NSs.

79 ASTRONOMY AND ASTROPHYSICS↗