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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Antiferromagnetic ordering and dipolar interactions of YbAlO 3

Here, we report low-temperature magnetic properties of the rare-earth perovskite material YbAlO 3 . Results of elastic and inelastic neutron scattering experiment, magnetization measurements along with the crystalline electrical field (CEF) calculations, indicate that the ground state of Yb moments is a strongly anisotropic Kramers doublet, and the moments are confined in the ab plane, pointing at an angle of φ=±23.5° to the $a$ axis. With temperature decreasing below T N =0.88 K, Yb moments order into the coplanar but noncollinear antiferromagnetic (AFM) structure $AxGy$, where the moments are pointed along their easy axes. In addition, we highlight the importance of the dipole-dipole interaction, which selects the type of magnetic ordering and may be crucial for understanding magnetic properties of other rare-earth orthorhombic perovskites. Further analysis of the broad diffuse neutron scattering shows that one-dimensional interaction along the c axis is dominant and implies YbAlO 3 as a new member of one-dimensional quantum magnets.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Magnetizabilities of relativistic hydrogenlike atoms in some arbitrary discrete energy eigenstates

We present the results of numerical calculations of magnetizability (χ) of the relativistic one-electron atoms with a pointlike, spinless and motionless nuclei of charge Ze. Exploiting the analytical formula for χ recently derived by us Stefańska (2015), valid for an arbitrary discrete energy eigenstate, we have found the values of the magnetizability for the ground state and for the first and the second set of excited states (i.e.: 2s{sub 1/2}, 2p{sub 1/2}, 2p{sub 3/2}, 3s{sub 1/2}, 3p{sub 1/2}, 3p{sub 3/2}, 3d{sub 3/2}, and 3d{sub 5/2}) of the Dirac one-electron atom. The results for ions with the atomic number 1⩽Z⩽137 are given in 14 tables. The comparison of the numerical values of magnetizabilities for the ground state and for each state belonging to the first set of excited states of selected hydrogenlike ions, obtained with the use of two different values of the fine-structure constant, i.e.: α{sup −1}=137.035 999 139 (CODATA 2014) and α{sup −1}=137.035 999 074 (CODATA 2010), is also presented.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

The Muon g-2 Experiment overview and status as of June 2016

The Muon g-2 Experiment at Fermilab will measure the anomalous magnetic moment of the muon to a precision of 140 parts per billion, which is a factor of four improvement over the previous E821 measurement at Brookhaven. The experiment will also extend the search for the electric dipole moment (EDM) of the muon by approximately two orders of magnitude, with a sensitivity down to 10 -21 e.cm. Both of these measurements are made by combining a precise measurement of the 1.45T storage ring magnetic field with an analysis of the modulation of the decay rate of higher-energy positrons (from anti-muons), recorded by 24 calorimeters and 3 straw tracking detectors. Furthermore, the recent progress in the alignment of the electrostatic quadrapole plates and the trolley rails inside the vacuum chambers, and in establishing the uniform storage ring magnetic field will be described.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Fast magnetic response in gigahertz-band for columnar-structured Fe nanoparticle assembly

High density Fe-based ferromagnetic nanoparticle (NP) assembly is expected to have unique magnetic properties, such as superferromagnetism and super-spin-glass, different from magnetically isolated NP systems due to strong dipole interactions among the NPs. A high dipole interaction field, H{sub dip}, of ∼3.5 kOe can result in a high effective internal field to the magnetic moment of the NP, expecting for ultra-fast magnetic response, that is, a high magnetic resonance frequency, f{sub r}, of ∼10 GHz. However, for a simply molded Fe NP assembly, a low f{sub r} was observed due to inhomogeneous distribution of the internal field, implying the necessity of a unidirectional state of H{sub dip} for higher f{sub r}. In this study, we fabricated a columnar Fe NP assembly for realizing the unidirectional state of H{sub dip} by applying our uniquely developed external field-induced agglomeration method for monodispersed Fe NPs (13 nm in average size) as a function of the field (0–30 kOe) and volume fraction of the Fe NPs (0.5%–51%) in a polymer matrix with dimensions of 4 mm × 4 mm × 0.7 mm{sup t}. A columnar-structured Fe NP assembly was successfully achieved along an in-plane direction (defined as the x-axis) under optimized conditions. From static magnetization curves, induced uniaxial magnetic anisotropy was observed according to the shape of the columnar structure of the Fe NP assembly, where easy and hard axes of magnetization were realized along the parallel (x-axis) and normal directions (in-plane y-axis and z-axis in the thickness direction) to the external field during the process, respectively. Interestingly, this fabricated columnar-structured Fe NP assembly exhibited very high f{sub r} in the range from 3 to 11 GHz judging from the complex susceptibility spectra obtained. The f{sub r} values were well-scaled by a modified Snoek's-limit-law using demagnetization factors quantitatively estimated from the static magnetization curves. Thus, shape-induced anisotropy originating from the unidirectional state of H{sub dip} in the columnar structure of the Fe NP assembly plays an important role for high frequency magnetic response in the GHz-band.

36 MATERIALS SCIENCE↗
NASA NTRS1981

Topology of Saturn's main magnetic field

The reported analysis of Saturn's main magnetic field takes into account the data obtained by Voyager 1 during its close flyby of Saturn in November 1980. A magnetic field model for the analysis of Saturn's main field in which the distributed ring currents are explicitly modelled is constructed. The considered internal field parameters constitute a first approximation to Saturn's main field. Several model current systems that might be expected on physical grounds to be active in Saturn's magnetosphere are considered. It is pointed out that certain aspects of Saturn's main magnetic field relevant to the planet's interior have been discussed by Stevenson (1980). In particular, the unexpectedly small dipole moment seems to be consistent with the gravitational settling of helium, which leads to a much smaller electrically conducting and convecting region than would be expected of a homogeneous distribution of hydrogen and helium.

Acuna, M. H.↗
DOE OSTI2013

Communication: Theoretical study of ThO for the electron electric dipole moment search

An experiment to search for the electron electric dipole moment (eEDM) on the metastable H{sup 3}Δ{sub 1} state of ThO molecule was proposed and now prepared by the ACME Collaboration [ http://www.electronedm.org ]. To interpret the experiment in terms of eEDM and dimensionless constant k{sub T,} {sub P} characterizing the strength of the T,P-odd pseudoscalar–scalar electron–nucleus neutral current interaction, an accurate theoretical study of an effective electric field on electron, E{sub eff}, and a parameter of the T,P-odd pseudoscalar–scalar interaction, W{sub T,} {sub P}, in ThO is required. We report our results for E{sub eff} (84 GV/cm) and W{sub T,} {sub P} (116 kHz) together with the hyperfine structure constant, molecule frame dipole moment, and H{sup 3}Δ{sub 1} → X{sup 1}Σ{sup +} transition energy, which can serve as a measure of reliability of the obtained E{sub eff} and W{sub T,} {sub P} values. Besides, our results include a parity assignment and evaluation of the electric-field dependence for the magnetic g factors in the Ω-doublets of H{sup 3}Δ{sub 1}.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Alignment of the straw tracking detectors for the Fermilab Muon $g − 2$ experiment and systematic studies for a muon electric dipole moment measurement

The Fermilab Muon $g-2$ experiment is currently preparing for its fourth data-taking period (Run-4). The experiment-wide effort on the analysis of Run-1 data is nearing completion, with the announcement of the first result expected in the coming months. The final goal of the experiment is to determine the muon magnetic anomaly to a precision of 140 ppb. This level of precision will provide indirect evidence of new physics, if the central value agrees with the previously-measured value of the magnetic anomaly. Essential in reducing the systematic uncertainty, through measurements of the muon beam profile, are the in-vacuum straw tracking detectors. A crucial prerequisite in obtaining accurate distributions of the beam profile is the internal alignment of the tracking detectors, which is described in this thesis. As a result of this position calibration, the tracking efficiency has increased by 3%, while the track quality increased by 4%. This thesis also discusses an additional measurement that will be made using the tracking detectors: a search for an electric dipole moment (EDM) of the muon, through the direct detection of an oscillation in the average vertical angle of the electron from the muon decay. An observation of a muon EDM would be evidencemore » of new physics and would provide a new source of CP violation in the charged lepton sector. Essential in measuring the EDM are accurate and precise estimations of potential non-zero radial and longitudinal magnetic fields, which were estimated using the Run-1 data. In addition, a preliminary analysis using the Run-1 data was undertaken to estimate the available precision for the magnetic anomaly measurement using the tracking detectors.« less

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

The UHECR dipole and quadrupole in the latest data from the original Auger and TA surface detectors

The sources of ultra-high-energy cosmic rays are still unknown, but assuming standard physics, they are expected to lie within a few hundred megaparsecs from us. Indeed, over cosmological distances cosmic rays lose energy to interactions with background photons, at a rate depending on their mass number and energy and properties of photonuclear interactions and photon backgrounds. The universe is not homogeneous at such scales, hence the distribution of the arrival directions of cosmic rays is expected to reflect the inhomogeneities in the distribution of galaxies; the shorter the energy loss lengths, the stronger the expected anisotropies. Galactic and intergalactic magnetic fields can blur and distort the picture, but the magnitudes of the largest-scale anisotropies, namely the dipole and quadrupole moments, are the most robust to their effects. Measuring them with no bias regardless of any higher-order multipoles is not possible except with full-sky coverage. In this work, we achieve this in three energy ranges (approximately $8$--$16~EeV$, $16$--$32~EeV$, and $32$--$\infty~EeV$) by combining surface-detector data collected at the Pierre Auger Observatory until 2020 and at the Telescope Array (TA) until 2019, before the completion of the upgrades of the arrays with new scintillator detectors. We find that the full-sky coverage achieved by combining Auger and TA data reduces the uncertainties on the north-south components of the dipole and quadrupole in half compared to Auger-only results.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1987

Revised upper limit on the internal magnetic moment of Venus

Over four Venus years of low altitude nightside PVO magnetometer observations are used to establish a new upper limit for the magnetic moment of Venus. Improvements over previous studies include data coverage and new instrument calibration information. The upper limit on an internal dipole moment is determined to be 8.4 x 10 to the 10th T cu m.

Phillips, J. L.↗
NASA NTRS1979

Models of an early lunar dynamo

The hypothesis that a dynamo once existed in the moon, and hence was the source of lunar paleomagnetism, is tested using a model for the global thermoremanent magnetization of spherical lithospheres. Various models of an ancient lunar dipole field are used which incorporate intensity variations and reversals, and which are consistent with lunar sample paleointensities. It is found that non-reversing lunar dynamos which have simple exponential decay histories beginning at 4.6 b.y. ago are inconsistent with this limit, unless the moon has been thoroughly demagnetized to a depth of tens of kilometers by impacts or other processes. An early lunar dynamo cannot be excluded by global scalar measurements unless the permanent lunar dipole moment is shown to be significantly less than 10 to the 13th power G/cu cm by future spacecraft measurements, which may be technologically impossible; vector measurements of lunar magnetic anomalies over the whole moon offer a possibility of determining the source of the field which magnetized the lunar crust.

Srnka, L. J.↗
DOE OSTI2016

Program for studying fundamental interactions at the PIK reactor facilities

A research program aimed at studying fundamental interactions by means of ultracold and polarized cold neutrons at the GEK-4-4′ channel of the PIK reactor is presented. The apparatus to be used includes a source of cold neutrons in the heavy-water reflector of the reactor, a source of ultracold neutrons based on superfluid helium and installed in a cold-neutron beam extracted from the GEK-4 channel, and a number of experimental facilities in neutron beams. An experiment devoted to searches for the neutron electric dipole moment and an experiment aimed at a measurement the neutron lifetime with the aid of a large gravitational trap are planned to be performed in a beam of ultracold neutrons. An experiment devoted to measuring neutron-decay asymmetries with the aid of a superconducting solenoid is planned in a beam of cold polarized neutrons from the GEK-4′ channel. The second ultracold-neutron source and an experiment aimed at measuring the neutron lifetime with the aid of a magnetic trap are planned in the neutron-guide system of the GEK-3 channel. In the realms of neutrino physics, an experiment intended for sterile-neutrino searches is designed. The state of affairs around the preparation of the experimental equipment for this program is discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Excitation and tunneling spectra of a fractional quantum Hall system in the thin-cylinder limit

Here, the excitations of fractional quantum Hall effect (FQHE) states have been largely inaccessible to experimental probes until recently. New electron scanning tunneling microscopy (STM) results from Hu et al. [Nat. Phys. 21, 716 (2025)] show promise in detecting and identifying these excited states via the local density of states (LDOS) spectrum. On a torus, there exists a mapping from the lowest Landau level states to a 1D lattice with a Hamiltonian that features dipole moment conservation. In this work, we apply perturbation theory starting from the thin-cylinder limit (𝐿 𝑥 → ∞, 𝐿 𝑦 < 𝑙 𝐵 for torus dimensions 𝐿 𝑥 and 𝐿 𝑦 and magnetic length 𝑙 𝐵 ) to obtain an analytical approach to the low-lying neutral and charged excitations of the 𝜈 = 1/3 FQHE state. Notably, in the thin cylinder, we can systematically enumerate all the low-lying excitations by the patterns of “dipoles” formed by the electron occupation pattern on the 1D lattice. We find that the thin-cylinder limit predicts a significant dispersion of the low-lying neutral excitations but sharpness of the LDOS spectra, which measure charged excitations. We also discuss connections between our work and several different approaches to the FQHE STM spectra, including those using the composite fermion theory. Numerical exact diagonalization beyond the thin-cylinder limit suggests that the energies of charged excitations remain largely confined to a narrow range of energies, which in experiments might appear as a single peak.

Adhidewata, Jyesta M. [University of California, B↗
DOE OSTI2018

Quality factor assessment of finite-size all-dielectric metasurfaces at the magnetic dipole resonance

Recently there has been a large interest in achieving metasurface resonances with large quality factors. In this article, we examine metasurfaces that comprised a finite number of magnetic dipoles oriented parallel or orthogonal to the plane of the metasurface and determine analytic formulas for their resonances’ quality factors. These conditions are experimentally achievable in finite-size metasurfaces made of dielectric cubic resonators at the magnetic dipole resonance. Our results show that finite metasurfaces made of parallel (to the plane) magnetic dipoles exhibit low quality factor resonances with a quality factor that is independent of the number of resonators. More importantly, finite metasurfaces made of orthogonal (to the plane) magnetic dipoles lead to resonances with large quality factors, which ultimately depend on the number of resonators comprising the metasurface. In particular, by properly modulating the array of dipole moments by having a distribution of resonator polarizabilities, one can potentially increase the quality factor of metasurface resonances even further. These results provide design guidelines to achieve a sought quality factor applicable to any resonator geometry for the development of new devices such as photodetectors, modulators, and sensors.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Comparative DFT Computational Studies with Experimental Investigations for Novel Synthesized Fluorescent Pyrazoline Derivatives

A novel series of pyrazoline derivatives were synthesized and their spectral properties were characterized via FT-IR, {sup 1}H, and {sup 13}C NMR. The electronic transitions and fluorescence properties were tracked via UV-Vis and emission spectrometry. The density functional theory (DFT) calculations have been also computed to get spot onto the geometry, electronic transitions and spectroscopic properties theoretically that has been compared with the encountered experimental ones. Moreover, the dipole moment, optimized energy, HOMO - LUMO energies and band gaps were calculated for novel candidates pyrazoline derivatives with highly fluorescence quantum yield.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2021

Surface processing and discharge-conditioning of high voltage electrodes for the Ra EDM experiment

The Ra EDM experiment uses a pair of high voltage electrodes to search for the atomic electric dipole moment of 225 Ra. We use identical, plane–parallel electrodes with a primary high gradient surface of 200 mm 2 to generate reversible DC electric fields. Our statistical sensitivity is linearly proportional to the electric field strength in the electrode gap. We adapted surface decontamination and processing techniques from accelerator physics literature to chemical polish and clean a suite of newly fabricated large-grain niobium and grade-2 titanium electrodes. Three pairs of niobium electrodes and one pair of titanium electrodes were discharge-conditioned with a custom high voltage test station at electric field strengths as high as +52.5 kV/mm and –51.5 kV/mm over electrode gap sizes ranging from 0.4 mm to 2.5 mm. One pair of large-grain niobium electrodes was discharge-conditioned and validated to operate at ±20 kV/mm with steady-state leakage current ≤ 25 pA (1σ) and a polarity-averaged 98 ± 19 discharges per hour. These electrodes were installed in the Ra EDM experimental apparatus, replacing a copper electrode pair, and were revalidated to ±20 kV/mm. Here, the niobium electrodes perform at an electric field strength 3.1 times larger than the legacy copper electrodes and are ultimately limited by the maximum output of our 30 kV bipolar power supply.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1984

Structure and polarization of active region microwave emission

Active region radio emission observations made at 6.16 cm wavelength during May 20-27, 1980, are the bases of maps of total intensity and circular polarization presented for the three regions whose Hale numbers are 16850, 16863, and 16864. A detailed comparison is made between these maps and on- and off-band H-alpha pictures and magnetograms. The neutral lines with which the strongest sources were associated have their two opposite polarities close to each other, implying a high magnetic field gradient, and are also associated with arch filament systems. A detailed analysis is undertaken of observations of the circular polarization sense inversion in region 16863. The large scale structure of the magnetic field can be approximated by a dipole with its axis inclined by 11 deg with respect to the photosphere, and with a dipole moment of about 2 x 10 to the 31 power cgs units.

Kundu, M. R.↗