Search NASA⌕ Search

SEARCH · Search NASA

Results for “Proton structure”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Strain-Modulated Platinum–Palladium Nanowires for Oxygen Reduction Reaction

Electrocatalytic activity of alloy nanocatalytsts can be manipulated effectively by tuning their physical properties (ensemble, geometric, and ligand effects) to afford optimal surface structure and compositions for proton exchange membrane fuel cell (PEMFC) application. Herein, highly catalytic platinum-palladium nanowires (Pt n Pd 100-n NWs) with a subtle lattice strain and Boerdijk-Coxeter helix type morphology are synthesized through a surfactant-free, thermal single phase solvent method. X-ray diffraction results show that Pt n Pd 100-n NWs are exposed through the (111) facets and their shrinking or expanding lattice parameters can be modulated by the alloy compositions. Electrochemical results reveal that their high catalytic activity correlates with the lattice shrinking, facets, and bimetallic compositions, showing higher activity when the ratio of Pt and Pd is similar to ~78:22, which is further supported by DFT results. Compared to the nanoparticle type platinum-palladium alloyed catalysts with similar metal compositions (Pt n Pd 100-n NPs), the Pt n Pd 100-n NWs exhibit significantly improved electrocatalytic activity and stability for the oxygen reduction reaction. Our findings open new strategies to design the highly active and stable alloy nanocatalysts with controllable compositions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Selectivity of Electrochemical Ion Insertion into Manganese Dioxide Polymorphs

The ion insertion redox chemistry of manganese dioxide has diverse applications in energy storage, catalysis, and chemical separations. Unique properties derive from the assembly of Mn–O octahedra into polymorphic structures that can host protons and nonprotonic cations in interstitial sites. Despite many reports on individual ion-polymorph couples, much less is known about the selectivity of electrochemical ion insertion in MnO 2 . In this work, we use density functional theory to holistically compare the electrochemistry of A x MnO 2 (where A = H + , Li + , Na + , K + , Mg 2+ , Ca 2+ , Zn 2+ , Al 3+ ) in aqueous and nonaqueous electrolytes. We develop an efficient computational scheme demonstrating that Hubbard-U correction has a greater impact on calculating accurate redox energetics than choice of exchange-correlation functional. Using PBE+U, we find that for nonprotonic cations, ion selectivity depends on the oxygen coordination environments inside a polymorph. When H + is present, however, the driving force to form hydroxyl bonds is usually stronger. In aqueous electrolytes, only three ion-polymorph pairs are thermodynamically stable within water’s voltage stability window (Na + and K + in α-MnO 2 , and Li + in λ-MnO 2 ), with all other ion insertion being metastable. We find Al 3+ may insert into the δ, R, and λ polymorphs across the full 2-electron redox of MnO 2 at high voltage; however, electrolytes for multivalent ions must be designed to impede the formation of insoluble precipitates and facilitate cation desolvation. We also show that small ions coinsert with water in α-MnO 2 to achieve greater coordination by oxygen, while solvation energies and kinetic effects dictate water coinsertion in δ-MnO 2 . Finally, taken together, these findings explain reports of mixed ion insertion mechanisms in aqueous electrolytes and highlight promising design strategies for safe, high energy density electrochemical energy storage, desalination batteries, and electrocatalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Dual-Band Electrochromism in Hydrous Tungsten Oxide

The independent modulation of visible and near-infrared light by a single material, termed dualband electrochromism, is highly desirable for smart windows to enhance the energy efficiency of buildings. Tungsten oxides are commercially important electrochromic materials, exhibiting reversible visible and near-infrared absorption when electrochemically reduced in an electrolyte containing small cations or protons. The presence of structural water in tungsten oxides has been associated with faster electrochromic switching speeds. Here, we find that WO 3 ·H 2 O, a crystalline hydrate, exhibits dual-band electrochromism unlike the anhydrous WO 3 providing a heretofore unexplored route to tune the electrochromic response of tungsten oxides. Absorption of near-infrared light is achieved at low Li + /e - injection, followed by the absorption of visible light at higher Li + /e - injection as a result of an electrochemically-induced phase transition. We propose that this dual-band modulation is possible due to the more open structure of WO 3 ·H 2 O as compared to WO 3 . This facilitates a more extended solid solution Li + insertion regime that benefits the modulation of near-infrared radiation via plasmon absorption. Higher degrees of Li + /e - insertion lead to polaronic absorption associated with localized charge storage. Furthermore, these results inform how structural factors influence the electrochemically induced spectral response of transition metal oxides and the important role of structural water beyond optical switching speed.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2025

High-isospin multiplets in 𝐴=15 and 16 nuclei

Isospin quartets (T=3/2) and quintets (T=2) have been investigated for A=15 and A=16 nuclei, respectively. Data from an invariant-mass experiment, with a 17 Ne beam, were reanalyzed and the T=3/2 and T=2 states in 15 O and 16 F, associated with p+ 14 N and 2p+ 14 N exit channels respectively, were found. In some cases, γ-ray gating was used to tag on events that decay to the excited 0 + , T=1 state in 14 N rather than the ground state. With the new states, the lowest-energy 1/2 + and 5/2 + quartets for A=15 and the 0 + and 2 + quintets for A=16 are completed. In addition, members of these multiplets in 15 F and 16 Ne decaying to the p+ 14 O and 2p+ 14 O channels are reevaluated by gating on events where the 14 O fragment recoils perpendicular to beam axis in the parent reference frame. Such transverse-decay events have the best invariant-mass resolution. No evidence for deviations from a quadratic dependence of the mass on the isospin projection was found for the A=15 quartets. However for the A=16 0 + and 2 + quintets, evidence for deviations were found.

Coulomb energies↗
DOE OSTI2022

Glassy quantum nuclear pasta in neutron star crusts

We conduct a comprehensive survey of the shape parameter space of the nuclear pasta phases in neutron star crusts by conducting three-dimensional Hartree-Fock + BCS calculations. Spaghetti, waffles, lasagna, bicontinuous phases and cylindrical holes occupy local minima in the resulting constant-pressure Gibbs energy surfaces, implying multiple geometries coexist at a given depth. Notably, the bicontinuous phase, in which both the neutron gas and nuclear matter extend continuously in all dimensions appears over a large depth range. Our results support the idea that nuclear pasta is a glassy system. At a characteristic temperature, of order 10 8 – 10 9 K, different phases may become frozen into domains whose sizes we estimate to be 1–50 times the lattice spacing and over which the local density and electron fraction can vary. Above this temperature, very little long-range order exists and matter is an amorphous solid. Electron scattering off domain boundaries may contribute to the disorder resistivity of the pasta phases. Annealing of the domains may occur during cooling; repopulating of local minima during crustal heating might lead to temperature-dependent transport properties in the deep crust layers. We identify four regions distinguished by whether pasta is the true ground state, and whether the pasta structure allows delocalization of protons. The whole pasta region can occupy up to 70% of the crust by mass and 25% by thickness, and the layer in which protons are delocalized could occupy 45% of the crust mass and 15% of its thickness.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Resonant structure of 18 Na and the N = 8 shell

The resonant structure of the proton-unbound nucleus 18 Na has been studied via knockout reactions of a 20 Mg beam on a 9 Be target. Three resonant states in 18 Na are identified through the invariant-mass reconstruction of 17 Ne+1⁢𝑝 events, including the 1$^−_1$ ground state with one-proton decay energy of 1.38(2) MeV. In comparison with the low-lying states in the mirror neutron-rich nucleus 18 N, the 1$^−_1$ ground state and 2$^−_1$ excited state with 𝜋⁢(1⁢𝑑 5/2 ) 3 ⊗ 𝜈⁢1⁢𝑝 1/2 configurations in 18 Na likely correspond to different proton seniorities, 𝜈=3 and 1, respectively, while the 0$^−_1$ and 1$^−_2$ states with 𝜋⁢(1⁢𝑑 5/2 ) 2⁢ (2⁢𝑠 1/2 ) ⊗ 𝜈⁢1⁢𝑝 1/2 configuration show obvious Thomas-Ehrman shifts. With the more-precise atomic mass of 18 Na, the one-neutron separation energy 𝑆𝑛⁡( 19 Na)=20.31⁢(2)⁢MeV is derived. Based on the systematics of the differences in experimental one-neutron separation energy in the isotopic chains from 𝑍=9 to 12, the shell effects at 𝑁=8 for proton-rich nuclei are discussed.

energy levels↗
DOE OSTI2026

Moments of parton distribution functions of the pion from lattice QCD using gradient flow

We present a nonperturbative determination of the pion valence parton distribution function (PDF) moment ratios ⟨𝑥 𝑛−1 ⟩/⟨𝑥⟩ up to 𝑛 = 6, using the gradient flow in lattice quantum chromodynamics (QCD). As a testing ground, we employ SU(3) isosymmetric gauge configurations generated by the OpenLat initiative with a pseudoscalar mass of 𝑚 𝜋 ≃ 411 MeV. Our analysis uses four lattice spacings and a nonperturbatively improved action, enabling full control over the continuum extrapolation, and the limit of vanishing flow time, 𝑡 →0. The flowed ratios exhibit O(𝑎 2 ) scaling across the ensembles, and the continuum-extrapolated results, matched to the $\overline{MS}$ scheme at 𝜇 = 2 GeV using next-to-next-to-leading order matching coefficients, show only mild residual flow-time dependence. The resulting ratios, computed with a relatively small number of configurations, are consistent with phenomenological expectations for the pion’s valence distribution, with statistical uncertainties that are competitive with modern global fits. These findings demonstrate that the gradient flow provides an efficient and systematically improvable method to access partonic quantities from first principles. Future extensions of this work will target lighter pion masses toward the physical point, and applications to nucleon structure such as the proton PDFs and the gluon and sea-quark distributions.

lattice QCD↗
DOE OSTI2020

A Proposed Forward Silicon Tracker for the Future Electron-Ion Collider and Associated Physics Studies

The future Electron-Ion Collider (EIC) will explore several fundamental questions in a broad Bjorken-x (x BJ ) and Q 2 phase space. Heavy flavor and jet products are ideal probes to precisely study the tomography of nucleon/nuclei structure, help solve the proton spin puzzle and understand the hadronizaton processes in vacuum or in the QCD medium. Due to the asymmetric collisions at the EIC, most of the final state hadrons are produced in the nucleon/nuclei beam going (forward) direction. A silicon vertex/tracking is critical to precisely measure these forward hadrons at the EIC. Details of different conceptual designs of the proposed Forward Silicon Tracker (FST) and the relevant detector performance are presented in this technical note. The associated heavy flavor and jet studies with the evaluated FST performance are discussed as well.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

The Status and Ambitions of the US Heavy Element Program

The aim of this whitepaper is to highlight the current capabilities and priorities of the US Heavy Element community and to provide the framework for a coordinated advancement of nuclear science from these studies. This is an organized effort to reflect on what has been achieved in the field given the recommendations and initiatives of the 2015 NSAC Long Range Plan, and on what can be realized in the next decade given current and possibly expanded investments. Current investments have positioned the US community to be among the world leaders in studies of the nuclear and chemical properties of the heaviest elements. These include studies of reaction mechanisms, moving us ever closer to the “island of stability”, in spectroscopy, allowing us to better understand nuclear structure at these extreme proton numbers, in chemical behavior, looking to determine how these elements should be placed on the Periodic Table, in performing the first measurements where isotopes are directly identified by their mass numbers, and in laying the foundation for a potential US-led new element discovery experiment. At present, the highest priority of the US Heavy Element community is to capitalize on the current investments by supporting the operations of US facilities at optimal values. These facilities include the Argonne Tandem Linac Accelerator System at Argonne National Laboratory and other Department of Energy facilities such as the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory, which has a dedicated superheavy element program, as well as university laboratories, including Texas A&M University. The High Flux Isotope Reactor at Oak Ridge National Laboratory is crucial to providing the radioactive isotopes required for heavy element science targets. This facility should be supported to provide the actinide materials that are essential for US-based science. Production of stable, rare isotopes for beam material, including 48 Ca, 50 Ti, 54 Cr and 58 Fe, at the Stable Isotope Production and Research Center is critical to continued research in heavy element science and should be a priority. The continued development of targets for heavy element science and retaining US-based expertise is critical for the heavy element community. This is an area that is currently under pressure. For example, the target laboratory at Argonne National Laboratory serves a broad community and is currently under threat due to loss of critical personnel. The skills needed to make targets for nuclear science and develop new targetry methods need to be supported long term at Argonne, Oak Ridge and Lawrence Livermore National Laboratories as well as maintaining the programs at Oregon State University and San José State University as vital pipelines for training students. Advances in theory are the foundation to understand how nuclei behave and to predict those behaviors in new circumstances. Progress in these studies will necessitate continued and new investment and access to high-performance computing. The future health of the heavy element field is dependent on the continuous support of talented early-career professionals at all levels. It is critical that opportunities continue to be created for the next generation to become established in heavy element research so that we can ensure the field is attracting and retaining the best minds for continued success. It is also clear that to ensure diversity of ideas, perspectives and techniques, we need to recruit diverse personnel that are trained at the best facilities. The heavy element community is in support of continued investment to programs with initiatives in diversity, equity, and inclusion. Looking to the next decade of research, support needs to maintain and grow US leadership in heavy element science. Specifically, new investments in state-of-the-art instrumentation will be essential to scientific development of the field and in expanding scientific knowledge. Advances in the next generation of electron cyclotron resonance ion sources, multi-reflection time-of-flight devices, laser spectroscopy, trapping methods and next generation alpha and gamma spectroscopy systems should be prioritized.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2024

Booster Neutrino Beam operations and neutrino flux prediction

The Booster Neutrino Beam (BNB) Line is used to produce neutrino beams for the 8 GeV Neutrino Program at Fermilab. This talk will provide a summary of the BNB operations and an estimate of the neutrino flux that is produced by the beamline. The talk will also summarize the work to upgrade the system which records the longitudinal structure of the primary proton beam that is delivered to BNB production target.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Basis light-front quantization approach to nucleon

We obtain the light-front wavefunctions for the nucleon in the valence quark Fock space from an effective Hamiltonian, which includes the transverse and longitudinal confinement and the one gluon exchange interaction with fixed coupling. The wavefunctions are generated by solving the eigenvalue equation in a basis light front quantization. Fitting the model parameters, the wavefunctions lead to good simultaneous description of electromagnetic form factors, radii, and parton distribution functions for the proton.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1976

Explorer 45 observations of the proton ring current

Explorer 45 satellite data on the stormtime proton ring current are reported and analyzed. Storm-associated variations of equatorially mirroring protons, interactions between the ring current and the plasmapause, and storm recovery phase behavior are discussed. Pitch-angle distributions are plotted as a function of proton energy and radial distance, the structure implying domination of pitch-angle diffusion of ring-current protons in the plasmapause region by resonant interactions with ion cyclotron waves during storm recovery. The anisotropic precipitation in the plasmapause region and the more poleward isotropic precipitation observed at low altitudes outside the plasmapause are compared and distinguished.

Lyons, L. R.↗
NASA NTRS1983

Correlated particle and magnetic field observations of a large-scale magnetic loop structure behind an interplanetary shock

From a survey of observations on ISEE-3, an example of correlated particle and magnetic field observations of a large-scale magnetic loop structure is presented. Bidirectional proton fluxes were observed for a period of 40 hours in the energy range 35-1600 keV approximately 12 hours after the passage of the interplanetary shock of December 11, 1980, and directly after the passage of a discontinuity. For each of the eight logarithmically spaced energy channels, a three-dimensional anisotropy analysis reveals streaming along both directions of the magnetic field. The magnetic field rotated slowly but steadily through approximately 180 deg during this same 40-hour period; this is consistent with the existence of a large-scale loop with extent greater than 0.5 AU. The observations suggest that the particles are being injected into the loop sunward of the spacecraft; they appear as bidirectional fluxes in the outermost regions of the loop arising from a combination of focusing and near scatter-free transport.

Sanderson, T. R.↗
NASA NTRS1985

Dynamics of the penetration boundaries of solar protons during a strong magnetic storm

The variations in the equatorial penetration boundary of solar protons with E sub p = 0.9 to 8.0 MeV during a strong magnetic storm of April 3 to 5, were analyzed. The dynamics of this boundary is compared with the dynamics of the outer trapping boundary of electrons with E sub e = - 0.3 to 0.6 MeV. The solar-proton penetration and the structure of the real magnetic field are studied. The unique data on the thin structure of development of a magnetospheric substorm were obtained for the first time.

Glukhov, G. A.↗