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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 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Production of 26 Al in stellar hydrogen-burning environments: Spectroscopic properties of states in 27 Si

Model predictions of the amount of the radioisotope Al-26 produced in hydrogen-burning environments require reliable estimates of the thermonuclear rates for the Al-26g(p,gamma) Si-27 and Al-26m(p,gamma)Si-27 reactions. These rates depend upon the spectroscopic properties of states in Si-27 within about 1 MeV of the Al-26g + p threshold (S-p = 7463 keV). We have studied the Si-28(He-3,alpha)Si-27 reaction at 25 MeV using a high-resolution quadrupole-dipole-dipole-dipole magnetic spectrograph. For the first time with a transfer reaction, we have constrained J(pi) values for states in Si-27 over E-x = 7.0-8.1 MeV through angular distribution measurements. Aside from a few important cases, we generally confirm the energies and spin-parity assignments reported in a recent gamma-ray spectroscopy study. The magnitudes of neutron spectroscopic factors determined from shell-model calculations are in reasonable agreement with our experimental values extracted using this reaction.

Parikh, A.↗
DOE OSTI2015

Electroexcitation of the Δ ( 1232 ) 3 2 + and Δ ( 1600 ) 3 2 + in a light-front relativistic quark model

Here, the magnetic-dipole form factor and the ratios R EM and R SM for the γ* N → Δ(1232)3/2 + transition are predicted within light-front relativistic quark model up to photon virtuality Q 2 =12 GeV 2 . Furthermore, we predict the helicity amplitudes of the γ* N → Δ(1600)3/2 + transition assuming the Δ(1600)3/2 + is the first radial excitation of the ground state Delta(1232)3/2 + .

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Investigation into the semimagic nature of the tin isotopes through electromagnetic moments

A complete set of electromagnetic moments, B(E2;0 + 1 2 + 1 ), Q(2 + 1 ), and g(2 + 1 ), have been measured from Coulomb excitation of semi-magic 112,114,116,118,120,122,124 Sn (Z = 50) on natural carbon and titanium targets. The magnitude of the B(E2) values, measured to a precision of ~4%, disagree with a recent lifetime study [Phys. Lett. B 695, 110 (2011)] that employed the Doppler- shift attenuation method. The B(E2) values show an overall enhancement compared with recent theoretical calculations and a clear asymmetry about midshell, contrary to naive expectations. A new static electric quadrupole moment, Q(2 + 1 ), has been measured for 114 Sn. The static quadrupole moments are generally consistent with zero but reveal an enhancement near midshell; this had not been previously observed. The magnetic dipole moments are consistent with previous measurements and show a near monotonic decrease in value with neutron number. The current theory calculations fail to reproduce the electromagnetic moments of the tin isotopes. The role of 2p-2h and 4p-4h intruders, which are lowest in energy at mid shell and outside of current model spaces, needs to be investigated in the future.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Effective field theory for vibrations in odd-mass nuclei

Heavy even-even nuclei exhibit low-energy collective excitations that are separated in scale from the microscopic (fermion) degrees of freedom. This separation of scale allows us to approach nuclear vibrations within an effective field theory (EFT). In odd-mass nuclei collective and single-particle properties compete at low energies, and this makes their description more challenging. In this article we describe spherical odd-mass nuclei with ground-state spin I = 1/2 by means of an EFT that couples a fermion to the collective degrees of freedom of an even-even core. The EFT relates observables such as energy levels, electric quadrupole transition strengths, and magnetic dipole moments of the odd-mass nucleus to those of its even-even neighbor and allows us to quantify theoretical uncertainties. For isotopes of rhodium and silver the theoretical description is consistent with data within experimental and theoretical uncertainties. Here, several testable predictions are made.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

First determination of ground state electromagnetic moments of Fe 53

Here, the hyperfine coupling constants of neutron deficient 53 Fe were deduced from the atomic hyperfine spectrum measured using the bunched-beam collinear laser spectroscopy technique. The low-energy 53 Fe beam was produced by projectile-fragmentation reactions followed by gas stopping, and used for the first time for laser spectroscopy. Ground state magnetic-dipole and electric-quadrupole moments were determined as μ= –0.65(1)μ N and Q=+35(15)e 2 fm 2 , respectively. The multiconfiguration Dirac-Fock method was used to calculate the electric field gradient to deduce Q from the quadrupole hyperfine coupling constant, since the quadrupole coupling constant has not been determined for any Fe isotopes. Both experimental values agree well with nuclear shell model calculations using the GXPF1A effective interaction performed in a full fp shell model space, which support the soft nature of the 56 Ni nucleus.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Prompt and delayed spectroscopy of At 203 : Observation of a shears band and a 29 / 2 + isomeric state

Using fusion-evaporation reactions, a gas-filled recoil separator, recoil-gating technique and recoil-isomer decay tagging technique we have extended the level scheme of 203 At(N=118) significantly. We have observed an isomeric [τ=14.1(3)μs] state with a spin and parity of 29/2 + . The isomeric state is suggested to originate from the π(h 9/2 )Ⓧ|| 202 Po;11 – > coupling, and it is depopulated through 286 keV E 2 and 366 keV E 3 transitions. Additionally, we have observed a cascade of magnetic-dipole transitions which is suggested to be generated by the shears mechanism.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Effective operators in two-nucleon systems

Effective Hamiltonians and effective electroweak operators are calculated with the Okubo-Lee-Suzuki formalism for two-nucleon systems. Working within a harmonic oscillator basis, first without and then with a confining harmonic oscillator trap, we demonstrate the effects of renormalization on observables calculated for truncated basis spaces. We illustrate the renormalization effects for the root-mean-square point-proton radius, electric quadrupole moment, magnetic dipole moment, Gamow-Teller transition and neutrinoless double-beta decay operator using nucleon-nucleon interactions from chiral Effective Field Theory. Renormalization effects tend to be larger in the weaker traps and smaller basis spaces suggesting applications to heavier nuclei with transitions dominated by weakly-bound nucleons would be subject to more significant renormalization effects within achievable basis spaces.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Transition form factors: γ * + p → Δ ( 1232 ) , Δ ( 1600 )

We report that electroproduction form factors describing the γ * p → Δ + ( 1232 ) , Δ + ( 1600 ) transitions are computed using a fully dynamical diquark-quark approximation to the Poincaré-covariant three-body bound-state problem in relativistic quantum field theory. In this approach, the Δ ( 1600 ) is an analogue of the Roper resonance in the nucleon sector, appearing as the simplest radial excitation of the Δ ( 1232 ) . Precise measurements of the γ * p → Δ + ( 1232 ) transition already exist on 0 ≤ Q 2 ≲ 8 GeV 2 , and the calculated results compare favorably with the data outside the meson-cloud domain. The predictions for the γ * p → Δ + ( 1600 ) magnetic dipole and electric quadrupole transition form factors are consistent with the empirical values at the real photon point, and extend to Q 2 ≈ 6 m p 2 , enabling a meaningful direct comparison with experiment once analysis of existing data is completed. In both cases, the electric quadrupole form factor is particularly sensitive to deformation of the Δ -baryons. Interestingly, while the γ * p → Δ + ( 1232 ) transition form factors are larger in magnitude than those for γ * p → Δ + ( 1600 ) in some neighborhood of the real photon point, this ordering is reversed on Q 2 ≳ 2 m p 2 , suggesting that the γ * p → Δ + ( 1600 ) transition is more localized in configuration space.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Role of Chiral Two-Body Currents in 6 Li Magnetic Properties in Light of a New Precision Measurement with the Relative Self-Absorption Technique

A direct measurement of the decay width of the excited $0^+_1$ state of 6 Li using the relative self-absorption technique is reported. Our value of $Γ_{γ,0^{+}_{1}} → 1^{+}_{1}$ = 8.17 (14) stat. (11) syst. eV provides sufficiently low experimental uncertainties to test modern theories of nuclear forces. The corresponding transition rate is compared to the results of ab initio calculations based on chiral effective field theory that take into account contributions to the magnetic dipole operator beyond leading order. This allows for a precision test of the impact of two-body currents that enter at next-to-leading order.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Ab Initio Prediction of the 4 $\mathrm{H}$e($d, γ$) 6 $\mathrm{L}$i Big Bang Radiative Capture

We report the rate at which helium ( 4 He ) and deuterium (d) fuse together to produce lithium-6 ( 6 Li) and a γ ray, 4 $\mathrm{H}$e($d, γ$) 6 $\mathrm{L}$i, is a critical puzzle piece in resolving the discrepancy between big bang predictions and astronomical observations for the primordial abundance of 6 Li . The accurate determination of this radiative capture rate requires the quantitative and predictive description of the fusion probability across the big bang energy window (30 keV ≲ E ≲ 400 keV), where measurements are hindered by low counting rates. We present first-principle (or, ab initio) predictions of the 4 $\mathrm{H}$e($d, γ$) 6 $\mathrm{L}$i astrophysical S factor using validated nucleon-nucleon and three-nucleon interactions derived within the framework of chiral effective field theory. By employing the ab initio no-core shell model with continuum to describe 4 He-d scattering dynamics and bound 6 Li product on an equal footing, we accurately and consistently determine the contributions of the main electromagnetic transitions driving the radiative capture process. Our results reveal an enhancement of the capture probability below 100 keV owing to previously neglected magnetic dipole (M1) transitions and reduce by an average factor of 7 the uncertainty of the thermonuclear capture rate between 0.002 and 2 GK.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Effects of Rolling Reduction on Critical Current Density and Microstructure of Bi-2212 Wires

Bi-2212 Rutherford cables have been fabricated into flat racetrack coils and canted-cosine-theta dipole magnets. The performance gap between the magnets made with Rutherford cables and the “short-sample-limit” is about 30%. To better understand the influence of Rutherford cable processing on the strand performance, we studied three Bi-2212 wires with filament architectures of 37 × 18 and 55 × 18 and diameters of 0.8 and 1.0 mm. To simulate the deformation caused by cabling process, the three wires were rolled with thickness reductions ranging from 10% to 30%. The aspect ratios of rolled strands are between 1.29 and 2.05. The low aspect-ratio wire is also an interesting form for fabricating solenoid coils with higher packing density. The round and rolled strands were heat-treated under 50 bar and with maximum heat treatment temperatures of 885.5 °C and 890.5 °C. The rolling deformation reduced filament size uniformity, resulting in filament merging in fully heat-treated wires. It was found that rolling reduction reduced wire critical current density (JE) by 16 to 18%, but the JE decrease saturated at 15 to 20% of the thickness reduction. It is believed that the reduced JE results from the filament merging caused by rolling and non-uniform shrinking during overpressure heat treatment.

Bi-2212 wire↗
DOE OSTI2020

Special Issue: To Commemorate the Legacy of Malcolm J. Andrews—Scientist, Educator, and Leader

This special issue celebrates the scientific legacy of Dr. Malcolm J. Andrews, former Editor of the ASME Journal of Fluids Engineering (2010–2018). Malcolm devoted his career to the development and applications of computational, experimental, and analytical tools to investigate and solve diverse, complex fluid dynamics, and heat transfer problems. Malcolm’s most notable research accomplishments include: (i) contributions to innovative experiments, simulations, and theory to understand buoyancydriven turbulent mixing due to Rayleigh–Taylor instability; (ii) development of the multiphase particle-in-cell method for understanding fragmentation in spray jets, coal-water slurry, and other dense particulate flows; (iii) mixing in nano- and biomaterials in applications ranging from protein glues to carbon nanotube composites; (iv) determining dispersion in proteins to improve therapeutic drug delivery via micro-encapsulation; (v) innovative methods for storing information using nanopinned dipole magnetic vortices in superconducting materials; and (vi) modeling and design modifications for shell-and-tube heat exchangers, as well as heat transfer in rotating systems such as turbine blades. The results of his research have been published in a long series of trend-setting journal and conference papers, book chapters, and patents.

42 ENGINEERING↗
DOE OSTI2020

When the Moon had a magnetosphere

Apollo lunar samples reveal that the Moon generated its own global magnetosphere, lasting from ~4.25 to ~2.5 billion years (Ga) ago. At peak lunar magnetic intensity (4 Ga ago), the Moon was volcanically active, likely generating a very tenuous atmosphere, and, it is believed, was at a geocentric distance of ~18 Earth radii (R E ). Solar storms strip a planet’s atmosphere over time, and only a strong magnetosphere would be able to provide maximum protection. We present simplified magnetic dipole field modeling confined within a paraboloidal-shaped magnetopause to show how the expected Earth-Moon coupled magnetospheres provide a substantial buffer from the expected intense solar wind, reducing Earth’s atmospheric loss to space.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

CEPC booster design study

In September 2012, Chinese scientists proposed a Circular Electron Positron Collider (CEPC) in China at 240 GeV center-of-mass energy for Higgs studies. The booster provides 120 GeV electron and positron beams to the CEPC collider for top-up injection at 0.1 Hz. The design of the full energy booster ring of the CEPC is a challenge. The ejected beam energy is 120 GeV and the injected beam energy is 6 GeV. Here in this paper we describe two alternative schemes, the wiggler bend scheme and the normal bend scheme. For the wiggler bend scheme, we propose to operate the booster ring as a large wiggler at low energy and as a normal ring at high energy to avoid the problem of very low dipole magnet fields. Finally, for the normal bend scheme, we implement the orbit correction to correct the earth field.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

tprimarywholesp.f90

Program tprimarywholesp.f90 calculates primary field d Bz / dt , directly in the time domain, for a unit strength magnetic dipole source pulse in a conducting medium (whole space). The source pulse wave function may be a step function turn-off, or square or triangular pulse of arbrary duration, or a ramp turn-off.

Smith, Torquil↗
DOE OSTI2019

Hysteresis in the spontaneous emission induced by VO 2 phase change

We investigate the spontaneous emission of a two-level quantum emitter in the vicinity of a vanadium dioxide (VO 2 ) thin film. By taking advantage of effective medium techniques to describe the dielectric constant of the VO 2 , we demonstrate that, in the near-field regime, the spontaneous emission rate of both electric and magnetic dipole emitters can be maximized at the insulator-to-metal phase transition temperature of the film. We find that VO 2 ’s thermal hysteresis curve produces clear fingerprints in the emitter’s decay process, offering a new degree of freedom to dynamically control light emission at the nanoscale. We also find that the spontaneous emission rate is a non-monotonic function of the emitter transition wavelength, presenting a pronounced peak at infrared frequencies. Altogether, our results reveal that VO 2 phase transition is a promising mechanism to achieve on-demand tuning of an emitter’s lifetime.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Experimental realization of a terahertz all-dielectric metasurface absorber

Metamaterial absorbers consisting of metal, metal-dielectric, or dielectric materials have been realized across much of the electromagnetic spectrum and have demonstrated novel properties and applications. However, most absorbers utilize metals and thus are limited in applicability due to their low melting point, high Ohmic loss and high thermal conductivity. Other approaches rely on large dielectric structures and / or a supporting dielectric substrate as a loss mechanism, thereby realizing large absorption volumes. Here we present a terahertz (THz) all dielectric metasurface absorber based on hybrid dielectric waveguide resonances. We tune the metasurface geometry in order to overlap electric and magnetic dipole resonances at the same frequency, thus achieving an experimental absorption of 97.5%. A simulated dielectric metasurface achieves a total absorption coefficient enhancement factor of F T =140, with a small absorption volume. Our experimental results are well described by theory and simulations and not limited to the THz range, but may be extended to microwave, infrared and optical frequencies. In conclusion, the concept of an all-dielectric metasurface absorber offers a new route for control of the emission and absorption of electromagnetic radiation from surfaces with potential applications in energy harvesting, imaging, and sensing.

36 MATERIALS SCIENCE↗