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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Status of a Single-Aperture 11 T Nb3Sn Demonstrator Dipole for LHC Upgrades

The planned upgrade of the LHC collimation system includes two additional collimators to be installed in the dispersion suppressor areas of points 2, 3 and 7. The necessary longitudinal space for the collimators could be provided by replacing some 8.33 T NbTi LHC main dipoles with 11 T dipoles based on Nb3Sn superconductor and compatible with the LHC lattice and main systems. To demonstrate t his possibility Fermilab and CERN have started in 2011 a joint R&D program with the goal of building b y 2014 a 5.5-m long twin-aperture dipole prototype suitable for installation in the LHC. The first step of this program is the development of a 2-m long single-aperture demonstration dipole with the nominal field of 11 T at the LHC nominal current of ~11. 85 kA and 60 mm bore with ~20% margin. This paper describes the design, construction and test results of the single-aperture Nb3Sn demonstrator model for the LHC collimation system upgrade.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Nb$_{3}$Sn 11 T Dipole for the High Luminosity LHC (FNAL). Chapter 8

This chapter describes the design and parameters of the 11 T dipole developed at the Fermi National Accelerator Laboratory (FNAL) in collaboration with the European Organization for Nuclear Research (CERN) for the High Luminosity LHC project, and presents details of the single-aperture and twin-aperture dipole models that were constructed and tested. Magnet test results including magnet quench performance, magnetic measurements, and quench protection studies performed using the dipole mirror and single-aperture and twin-aperture dipole models are summarized and discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Influence of substituents on the vectorial difference static dipole upon excitation in synthetic bacteriochlorins

Organic dye aggregates have been shown to exhibit exciton delocalization in natural and synthetic systems. Such dye aggregates show promise in the emerging area of quantum information science (QIS). We believe that the difference static dipole (Δd) is an essential dye parameter in the development of molecular QIS systems. However, a foundational understanding of the structural factors influencing Δd remains elusive. Bacteriochlorins play a vital role in photosynthesis due to their exceptional photophysical properties. Therefore, bacteriochlorins are particularly suitable dyes for the construction of aggregate systems for QIS. Synthetic bacteriochlorins further offer stability and tunability via chemical modifications. Here, the influence of substituents on the Δd of monomeric (non-aggregated) dyes was investigated via density functional theory (DFT) and time-dependent (TD-)DFT in a set of 5-methoxybacteriochlorins progressively substituted with ethynyl, phenyl, and phenylethynyl substituents at the 3,13- and 3,13,15-positions of the macrocycle. Symmetrically substituted 5-methoxybacteriochlorins were shown to have the largest Δd. The increase in Δd in the series of dyes was largely due to changes in orientation of the static dipole upon excitation rather than large changes in magnitude. In addition, the transition dipole (μ) and the angle between Δd and μ (ζ) were calculated. Three 5-methoxybacteriochlorins with high predicted Δd and μ were synthesized and characterized spectroscopically. The trend in Δd values empirically determined using the solvatochromic Stokes shift method was comparable with the DFT calculations.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Measuring Dipole Inversion in Self-Assembled Nano-Dielectric Molecular Layers

A self-assembled nanodielectric (SAND) is an ultrathin film, typically with periodic layer pairs of high-k oxide and phosphonic-acid-based $π$-electron (PAE) molecular layers. IPAE, having a molecular structure similar to that of PAE but with an inverted dipole direction, has recently been developed for use in thin-film transistors. In this paper we report that replacing PAE with IPAE in SAND-based thin-film transistors induces sizable threshold and turn-on voltage shifts, indicating the flipping of the built-in SAND polarity. The bromide counteranion (Br–) associated with the cationic stilbazolium portion of PAE or IPAE is of great importance, because its relative position strongly affects the electric dipole moment of the organic layer. Hence, a set of X-ray synchrotron measurements were designed and performed to directly measure and compare the Br– distributions within the PAE and IPAE SANDs. Two trilayer SANDs, consisting of a PAE or IPAE layer sandwiched between an HfOx and a ZrOx layer, were deposited on the SiOx surface of Si substrates or periodic Si/Mo multilayer substrates for X-ray reflectivity and X-ray standing wave measurements, respectively. Along with complementary DFT simulations, the spacings, elemental (Hf, Br, and Zr) distributions, molecular orientations, and Mulliken charge distributions of the PAE and IPAE molecules within each of the SAND trilayers were determined and correlated with the dipole inversion.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Diabatization based on the dipole and quadrupole: The DQ method

In this work, we present a method, called the DQ scheme (where D and Q stand for dipole and quadrupole, respectively), for transforming a set of adiabatic electronic states to diabatic states by using the dipole and quadrupole moments to determine the transformation coefficients. It is more broadly applicable than methods based only on the dipole moment; for example, it is not restricted to electron transfer reactions, and it works with any electronic structure method and for molecules with and without symmetry, and it is convenient in not requiring orbital transformations. We illustrate this method by prototype applications to two cases, LiH and phenol, for which we compare the results to those obtained by the fourfold-way diabatization scheme.

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

Improved study of electric dipoles on the Si(100)-2 × 1 surface by non-contact scanning nonlinear dielectric microscopy

We studied a Si(100)-2 × 1 surface by non-contact scanning nonlinear dielectric microscopy (NC-SNDM). Simultaneously taken images of the topography and electric dipole moment distribution show that negative electric dipole moments are locally formed on individual dimers on the surface. In addition, we obtained the dc bias voltage dependence of the ε{sub local}(3) signal on a specific dimer by using an atom-tracking technique with NC-SNDM. We observed that the electric dipole induced a surface potential of around −250 mV on the dimer.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

A molecular symmetry analysis of the electronic states and transition dipole moments for molecules with two torsional degrees of freedom

We present a molecular symmetry analysis of electronic states and transition dipole moments for molecules which undergo large amplitude intramolecular torsions. The method is based on the correlation between the point group of the molecule at highly symmetric configurations and the molecular symmetry group. As an example, we determine the global irreducible representations of the electronic states and transition dipole moments for the quinodimethane derivative 2-[4-(cyclopenta-2,4-dien-1-ylidene)cyclohexa-2,5-dien-1-ylidene]-2H-1, 3-dioxole for which two torsional degrees of freedom can be activated upon photo-excitation and construct the resulting symmetry adapted transition dipole functions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Spectroscopic studies of biologically active coumarin laser dye: Evaluation of dipole moments by solvatochromic shift method

In this paper we attempted to record absorption and emission spectra of 2-acetyl-3H-benzo[f]chromen-3-one [2AHBC] laser dye in different solvents of varying polarities to investigate its solvatochromic behavior. The two electronic states dipole moments of 2AHBC are calculated using solvatochromic spectral shifts which are correlated with dielectric constant (ε) refractive index (n) of various solvents. A systematic approach is made to estimate ground and excited state dipole moments on the basis of different solvent correlation methods like Bilot-Kawski equations, Lippert-Mataga, Bakhsheiv, Kawaski-Chamma-Viallet and Reichardt methods. Dipole moments in the excited state was found to be higher than the ground state by confirming π→π* transition.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

THE SUBMILLIMETER AND MILLIMETER EXCESS OF THE SMALL MAGELLANIC CLOUD: MAGNETIC DIPOLE EMISSION FROM MAGNETIC NANOPARTICLES?

The Small Magellanic Cloud (SMC) has surprisingly strong submillimeter- and millimeter-wavelength emission that is inconsistent with standard dust models, including those with emission from spinning dust. Here, we show that the emission from the SMC may be understood if the interstellar dust mixture includes magnetic nanoparticles, emitting magnetic dipole radiation resulting from thermal fluctuations in the magnetization. The magnetic grains can be metallic iron, magnetite Fe{sub 3}O{sub 4}, or maghemite {gamma}-Fe{sub 2}O{sub 3}. The required mass of iron is consistent with elemental abundance constraints. The magnetic dipole emission is predicted to be polarized orthogonally to the normal electric dipole radiation if the nanoparticles are inclusions in larger grains. We speculate that other low-metallicity galaxies may also have a large fraction of the interstellar Fe in magnetic materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

SGR 0418+5729: A SMALL INCLINATION ANGLE RESULTING IN A NOT SO LOW DIPOLE MAGNETIC FIELD?

The spin-down behaviors of SGR 0418+5729 are investigated. The pulsar spin-down model of Contopoulos and Spitkovsky is applied to SGR 0418+5729. It is shown that SGR 0418+5729 lies below the pulsar death line and its rotation-powered magnetospheric activities may therefore have stopped. The compact star is now spun down by the magnetic dipole moment perpendicular to its rotation axis. Our calculations show that under these assumptions there is the possibility of SGR 0418+5729 having a strong dipole magnetic field, if there is a small magnetic inclination angle. Its dipole magnetic field may be much higher than the characteristic magnetic field. Therefore, SGR 0418+5729 may be a normal magnetar instead of a low magnetic field magnetar.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

CONSTRAINT ON LIGHT DIPOLE DARK MATTER FROM HELIOSEISMOLOGY

We investigate the effects of a magnetic dipole moment of asymmetric dark matter (DM) in the evolution of the Sun. The dipole interaction can lead to a sizable DM scattering cross section even for light DM, and asymmetric DM can lead to a large DM number density in the Sun. We find that solar model precision tests, using as diagnostic the sound speed profile obtained from helioseismology data, exclude dipolar DM particles with a mass larger than 4.3 GeV and magnetic dipole moment larger than 1.6 × 10{sup –17} e cm.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Lattice QCD and the Neutron Electric Dipole Moment

The recent lattice QCD calculations of the neutron and proton electric dipole moments and the CP-violating πNN coupling constant due to the θ term are reviewed. Progress toward nucleon electric dipole moment calculations, including the Weinberg three-gluon operator, the quark chromoelectric dipole moment operator, and their renormalization, is also discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Tradeoff between Intermolecular Interaction and Backbone Disorder by High Molecular Dipole Block for Improving Blend Morphology of Polymer Solar Cells

Constructing terpolymer has attracted increasing attention as a strategy to improve the performance of polymer solar cell. Terpolymer usually offers an opportunity to lower the frontier molecular orbital energy level, introduces additional absorption band and sometimes optimizes the morphology of the active blend. Generally, the additional segment in terpolymer backbone inevitably introduces backbone disorder, which causes entropy rises. However, selecting a suitable dipole unit introduces extra driving forces for crystallization by enhancing intermolecular interactions. This provides a handy knob for tradeoff between intermolecular interaction and backbone disorder, thus regulating the blend morphology. In this study, a high dipole and electron-deficient group of pyrrolo[3,4-f ]benzotriazole-5,7(6H)-dione (TzBI) is incorporated into the high-performance donor polymer and a series of terpolymers with different content of TzBI are designed. As expected, the morphology is optimized gradually for improving charge generation and charge transport, also suppressing charge recombination. The champion device with 10% TzBI exhibited a power conversion efficiency (PCE) of 18.36%, which is 5% increase compared to the controlled device. This study presents a charming terpolymer strategy by highly electron-deficient and high dipole segment to realize a tradeoff between intermolecular interaction and backbone disorder, facilitating the optimization of morphology and elevation of fill factor and device efficiency.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Nonvolatile Magnetoelectric Switching of Magnetic Tunnel Junctions with Dipole Interaction

The magnetoelectric effect is technologically appealing because of its ability to manipulate magnetism using an electric field rather than magnetic field or current, thus providing a promising solution for the development of energy-efficient spintronics. Although 180° magnetization switching is vital to spintronic devices, the achievement of 180° magnetization switching via magnetoelectric coupling is still a fundamental challenge. Here, in this work, voltage-driven full resistance switching of a magnetic tunnel junction (MTJ) with dipole interaction on a ferroelectric substrate through switchable parallel/antiparallel magnetization alignment is demonstrated. Parallel magnetization alignment along the y direction is obtained under a bias magnetic field. By rotating the magnetic easy axis via strain-mediated magnetoelectric coupling, the parallel magnetizations in the MTJ reorient to the x axis with opposite paths because of dipole interaction, thus resulting in antiparallel alignment. Moreover, this voltage switching of MTJs is nonvolatile owing to variations in dipole interaction and can be well understood via phase field simulations. The results provide an avenue to realize electrical switching of MTJs and are significant for exploring energy-efficient spintronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Saddle-Shaped Third Component with Out-of-Plane Electrostatic Dipole for Realizing High-Performance Photovoltaic Donor Terpolymers

Terpolymer fabrication is an effective methodology for molecular engineering and generating high-performance organic photovoltaic materials to construct highly efficient polymer solar cells. Modification of the polymer PM6 by incorporating a third component resulting in the formation of a ternary copolymer is reported to outperform PM6 in achieving enhanced device performances. However, one of the major challenges in constructing high-performance terpolymers is to counter the molecular disorder caused by the backbone entropy induced by the third moiety. Here, in this work, double B←N bridged bipyridine (BNBP) is used as the third component, which possesses a strong out-of-plane electrostatic dipole owing to the saddle-shaped B←N fused ring structure. The out-of-plane dipole moment introduced in the modified PM6 terpolymer can be used as a means for tuning and optimizing the nanostructures of the blended films. The prepared PM6-BNBP-4 blend polymer with 4% of the benzodithiophene dione monomers replaced by BNBP results in excellent power conversion efficiency of 19.13%. This work demonstrates that the out-of-plane electrostatic dipole moment in saddle-shaped molecules is valuable for achieving high-performance organic photovoltaic donor materials.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Pairing Toroidal and Magnetic Dipole Resonances in Elliptic Dielectric Rod Metasurfaces for Reconfigurable Wavefront Manipulation in Reflection

Abstract A novel approach for reconfigurable wavefront manipulation with gradient metasurfaces based on permittivity‐modulated elliptic dielectric rods is proposed. It is shown that the required 2π phase span in the local electromagnetic response of the metasurface can be achieved by pairing the lowest magnetic dipole Mie resonance with a toroidal dipole Mie resonance, instead of using the lowest two Mie resonances corresponding to fundamental electric and magnetic dipole resonances as customarily exercised. This approach allows for the precise matching of both the resonance frequencies and quality factors. Moreover, the accurate matching is preserved if the rod permittivity is varied, allowing for constructing reconfigurable gradient metasurfaces by locally modulating the permittivity in each rod. Highly efficient tunable beam steering and beam focusing with ultrashort focal lengths are numerically demonstrated, highlighting the advantage of the low‐profile metasurfaces over bulky conventional lenses. Notably, despite using a matched pair of Mie resonances, the presence of an electric polarizability background allows to perform the wavefront shaping operations in reflection, rather than transmission. This has the advantage that any control circuitry necessary in an experimental realization can be accommodated behind the metasurface without affecting the electromagnetic response.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Beam steering characteristics of highly directive photoconductive dipole phased array antenna for terahertz imaging application

In this paper, the beam-steering characteristics of photoconductive dipole phased array antenna configuration at 1.95 THz is presented. The proposed array antenna configuration with frequency selective surface favourably improves its gain and directivity which is useful to upsurge the imaging capabilities to address the deliberations such as limited depth-of-field (DoF) and size-weight-and-power of the THz source for imaging applications. These are important considerations for applications like stand-off imaging and surveillance of moving targets where the high angular resolution as well as extended DoF are the important parameters for successful detection of concealed explosives. The projected planar profile and compact highly directive (2×2) small-gap photoconductive dipole phased array antenna can be castoff for the exposure of concealed explosives such as RDX, TNT, and HMX which illustrate their substantial spectral absorption fingerprints in terahertz (1.4–2.2 THz) regime of the spectrum. A simple method of beam-steering has been explored based on phase controlled optical excitation of highly directive small-gap photoconductive dipole array antenna. Further, the effects of uniform progressive phase shift on the beam-steering of uniform linear array (along x-axis) as well as planar array (x-axis and y-axis) is investigated.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Tailoring electric dipole of hole-transporting material p-dopants for perovskite solar cells

We report Li-TFSI/t-BP are the most widely employed p-dopants for hole-transporting materials (HTMs) within the state-of-the-art perovskite solar cells (PSCs). The hygroscopicity and migration of these dopants, however, lead to devices with limited stability. To solve this problem, we report here on a diphenyl iodide cation and pentafluorophenyl boric acid anion-based dopant (DIC-PBA) with an oriented interfacial dipole moment as an alternative to Li-TFSI/t-BP. Theoretical and experimental data reveal that DIC-PBA exhibits deep doping of poly[bis(4-phenyl)(2,4,6-triMethylphenyl)aMine] (PTAA) and also creates p-doping of perovskite surface, which originates from ionic interactions-derived dipole arrangement that yields fast interfacial charge transport. The improved intrinsic stability of PSCs originates from the inhibition of dipole moment degeneration on the perovskite surface. Devices prepared with DIC-PBA yielded high efficiency of 22.86%, and the modules (aperture area: 33.2 cm 2 ) efficiency reached 19.13%. Importantly, the storage stability also significantly improved exceeding to 90% after aging 1,200 h under air ambient.

14 SOLAR ENERGY↗