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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Cyclotron resonance accelerators for industrial applications

Here, this paper describes novel configurations for cyclotron resonance acceleration of electrons and ions that have several attractive features including: a compact robust room-temperature single-cell RF cavity as the accelerator structure; and continuous high current accelerated un-bunched beam output with self-scanning, obviating need for a separate beam scanner. An electron accelerator version, the electron Cyclotron Resonance Accelerator (eCRA), is under development to be an efficient source for high power electron and x-ray beams for medical, research, sterilization, and National Security applications, so as to replace radioactive materials. An ion accelerator version, the ion Cyclotron Auto-Resonance Accelerator (iCARA) is described here, suggesting its potential to produce, as an example, a high-current multi-MeV beam of deuterons which could be highly competitive with that produced either with linacs or cyclotrons. Such a deuteron beam could produce a high flux of fast neutrons via deuteron stripping, for applications including the transmutation of used nuclear fuel, material studies relevant for a fusion reactor inner wall, tritium breeding and medical isotope production. For the high-current, high efficiency simulated performance for eCRA and iCARA as described in this paper, the particle beams produced may not exhibit the low emittance values that are important for most discovery research. Rather, the beams could be useful for industrial applications where higher emittance and some energy spread can be tolerated, in favor of high beam power.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Coupling Two Laser-Cooled Ions via a Room-Temperature Conductor

We demonstrate coupling between the motions of two independently trapped ions with a separation distance of 620 μm. Here, the ion-ion interaction is enhanced via a room-temperature electrically floating metallic wire which connects two surface traps. Tuning the motion of both ions into resonance, we show flow of energy with a coupling rate of 11 Hz. Quantum-coherent coupling is hindered by strong surface electric-field noise in our device. Our ion-wire-ion system demonstrates that room-temperature conductors can be used to mediate and tune interactions between independently trapped charges over distances beyond those achievable with free-space dipole-dipole coupling. This technology may be used to sympathetically cool or entangle remotely trapped charges and enable coupling between disparate physical systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Revealing the loss mechanisms of a 3D superconducting microwave cavity for use in a dark matter search

Superconducting microwave cavities have found applications in many areas including quantum computing, particle accelerators, and dark matter searches. Their extremely high quality factors translate to very narrow bandwidth, which makes them key components of sensitive detectors. In this study, we aim to understand the loss mechanisms of an aluminium cavity, with a fundamental mode frequency of about 2.5123 GHz, and how they change as the cavity material transitions from the superconducting to normal state. We found that at temperatures not much lower than the transition temperature $T_c$, losses are dominated by quasiparticle excitations and are well described by the Bardeen–Cooper–Schrieffer theory. The exponential decrease of the quasiparticle density below $T_c$ results in a 1000-fold increase of the quality factor, as well as a shift of the resonance frequency due to the change of the kinetic inductance of the superconductor. At very low temperatures, losses due to two-level systems begin to dominate giving a peak in the quality factor of about 2.76 x 10 7 at 130 mK. Understanding the loss mechanisms is invaluable, as the working temperature of the cavity may vary during operation regardless of its application.

Physics - Physics of elementary particles and fiel↗
NASA NTRS1989

Fast spectroscopic variations on rapidly-rotating, cool dwarfs. 3: Masses of circumstellar absorbing clouds on AB Doradus

New time-resolved H alpha, Ca II H and K and Mg II h and k spectra of the rapidly-rotating K0 dwarf star AB Doradus (= HD 36705). The transient absorption features seen in the H alpha line are also present in the Ca II and Mg II resonance lines. New techniques are developed for measuring the average strength of the line absorption along lines of sight intersecting the cloud. These techniques also give a measure of the projected cloud area. The strength of the resonance line absorption provides useful new constraints on the column densities, projected surface areas, temperatures and internal turbulent velocity dispersions of the circumstellar clouds producing the absorption features. At any given time the star appears to be surrounded by at least 6 to 10 clouds with masses in the range 2 to 6 x 10(exp 17) g. The clouds appear to have turbulent internal velocity dispersions of order 3 to 20 km/s, comparable with the random velocities of discrete filamentary structures in solar quiescent prominences. Night-to-night changes in the amount of Ca II resonance line absorption can be explained by changes in the amplitude of turbulent motions in the clouds. The corresponding changes in the total energy of the internal motions are of order 10(exp 29) erg per cloud. Changes of this magnitude could easily be activated by the frequent energetic (approximately 10(exp 34) erg) x ray flares seen on this star.

Cameron, A. Collier↗
DOE OSTI2023

Nonlinear Dispersion Relation and Out‐of‐Plane Second Harmonic Generation in MoSSe and WSSe Janus Monolayers

Janus transition metal dichalcogenides are an emerging class of atomically thin materials with engineered broken mirror symmetry that gives rise to long‐lived dipolar excitons, Rashba splitting, and topologically protected solitons. They hold great promise as a versatile nonlinear optical platform due to their broadband harmonic generation tunability, ease of integration on photonic structures, and nonlinearities beyond the basal crystal plane. Here, second and third harmonic generation in MoSSe and WSSe Janus monolayers is studied. Polarization‐resolved spectroscopy is used to map the full second‐order susceptibility tensor of MoSSe, including its out‐of‐plane components. In addition, the effective third‐order susceptibility and the second‐order nonlinear dispersion close to exciton resonances for both MoSSe and WSSe are measured at room and cryogenic temperatures. This work sets a bedrock for understanding the nonlinear optical properties of Janus transition metal dichalcogenides and probing their use in the next‐generation on‐chip multifaceted photonic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Band Edge Excitons and Amplified Spontaneous Emission of Mercury Chalcogenide Nanoplatelets

Colloidal nanoplatelets of HgSe and HgTe prepared indirectly through cation exchange reactions can transfer many of the advantageous properties of atomically precise, 2D cadmium chalcogenides to the near-infrared (NIR) spectral window. In this work, HgSe and HgTe nanoplatelets are studied to understand their fundamental photophysical properties, particularly those areas of similarity and difference from cadmium-based NPLs, and to examine their potential as optical gain media. Similar to cadmium chalcogenide NPLs, low-temperature photoluminescence of HgTe NPLs displays two-color emission that depends on temperature, sample, fluence, excitation frequency, and irradiation time. Both HgTe and HgSe show nanosecond emission dynamics at temperatures as low as 2.5 K, with no indication that bright-dark excitonic splitting governs the low-temperature photoluminescence. Collectively, experimental data is most consistent with emission from a negative trion state at low temperature. Although the mercury chalcogenide nanoplatelets are shown to have broadened optical resonances compared to the cadmium chalcogenides from which they are derived, they retain slow Auger recombination and can display low-threshold amplified spontaneous emission in the NIR spectral window. Optical pumping thresholds for HgTe NPLs are observed as low as 4.4 µJ cm -2 and highlight the potential 2D nanoplatelets as gain medium in the near-infrared.

36 MATERIALS SCIENCE↗
DOE OSTI2026

First identification of resonant states in the {sup 45}V(p, {gamma}){sup 46}Cr reaction and their influence on the production of {sup 44}Ti in Core Collapse Supernovae

The observation of active 44Ti in supernova remnants offers the potential to solve one of the most debated questions in modern astrophysics, the exact underlying explosion mechanism of core collapse supernovae (CCSNe). In particular, a comparison between the predicted synthesized yield of 44Ti and the ejected flux is expected to allow for a determination of the mass cut of the star. Unfortunately, such comparisons are currently severely hindered by large uncertainties in the nuclear reactions governing the production and destruction of 44Ti. On this note, the astrophysical 45Vðp; γÞ46Cr reaction is expected to play a decisive role. We present the first experimental information on resonant states in the 45Vðp; γÞ46Cr reaction. Excitation energies have been measured with high precision for ten previously unknown, low-spin, proton-unbound states in 46Cr, and spin-parity-assignment constraints have been made using observed γ-decay patterns and shell-model calculations. We find that an l ¼ 1 resonance at 714 keV dominates the 45Vðp; γÞ46Cr reaction for the entire temperature range of α-rich freezeout. Moreover, the nominal rate is found to be ∼25–50% of previous estimates for T > 1.2 GK, indicating an increase in 44Ti production in CCSNe of ∼20–35%.

Cousins, C↗
DOE OSTI2024

Principles of two-dimensional terahertz spectroscopy of collective excitations: The case of Josephson plasmons in layered superconductors

Two-dimensional terahertz spectroscopy (2DTS), a terahertz analog of nuclear magnetic resonance, is a new technique poised to address many open questions in complex condensed matter systems. The conventional theoretical framework used ubiquitously for interpreting multidimensional spectra of discrete quantum level systems is, however, insufficient for the continua of collective excitations in strongly correlated materials. Here, in this work, we develop a theory for 2DTS of a model collective excitation, the Josephson plasma resonance in layered superconductors. Starting from a mean-field approach at temperatures well below the superconducting phase transition, we obtain expressions for the multidimensional nonlinear responses that are amenable to intuition derived from the conventional single-mode scenario. We then consider temperatures near the superconducting critical temperature T c , where dynamics beyond mean-field become important and conventional intuition fails. As fluctuations proliferate near T c , the dominant contribution to nonlinear response comes from an optical parametric drive of counterpropagating Josephson plasmons, which gives rise to 2D spectra that are qualitatively different from the mean-field predictions. As such, and in contrast to one-dimensional spectroscopy techniques, such as third harmonic generation, 2DTS can be used to directly probe thermally excited finite-momentum plasmons and their interactions. Our theory can readily be tested in cuprates, and we discuss implications beyond the present context of Josephson plasmons.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Freezing of the Lattice in the Kagome Lattice Heisenberg Antiferromagnet Zn-Barlowite ZnCu 3 (OD) 6 FBr

Here, we use 79 Br nuclear quadrupole resonance (NQR) to demonstrate that ultraslow lattice dynamics set in below the temperature scale set by the Cu-Cu superexchange interaction J (≃160 K) in the kagome lattice Heisenberg antiferromagnet Zn-barlowite. The lattice completely freezes below 50 K, and 79 Br NQR line shapes become twice broader due to increased lattice distortions. Moreover, the frozen lattice exhibits an oscillatory component in the transverse spin echo decay, a typical signature of pairing of nuclear spins by indirect nuclear spin-spin interaction. This indicates that some Br sites form structural dimers via a pair of kagome Cu sites prior to the gradual emergence of spin singlets below ~30 K. Our findings underscore the significant roles played by subtle structural distortions in determining the nature of the disordered magnetic ground state of the kagome lattice.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Data for "Integrated Green Biorefinery for the Production of Anthocyanins, Fermentable Sugars, and High Pure Lignin from Miscanthus × giganteus "

Miscanthus x giganteus (Mxg) is a promising perennial crop for producing natural colorants, renewable fuels, and bioproducts. However, natural recalcitrance and high pretreatment cost are major barriers to their complete conversion. In this study, a green processing method has been investigated for efficient recovery of natural pigments (anthocyanins), fermentable sugars, and pure lignin from Mxg genotypes using choline chloride-based natural deep eutectic solvents (NADES) systems. Interestingly, choline chloride: lactic acid (ChCl: LA) NADES-processed biomass resulted in 67.8 ± 2.1 μg g−1 of anthocyanins from dry biomass. A maximum of 87.4%–94.1% glucose yield was achieved after enzymatic saccharification. The effective extraction of lignin with high purity with higher β-aryl ether (βO4) bonds from advanced crops is crucial for lignin valorization. Notably, highly pure lignin (≈93.4% ± 1.4%) is achieved after low-temperature NADES pretreatment while retaining lignin’s native structure. 31P nuclear magnetic resonance demonstrated that total phenolics for ChCl: LA-lignin resulted in 1.20 mmol g−1 hydroxyls. The relative monolignol composition of syringyl (S), guaiacyl (G), and p-hydroxyphenyl (H) is 19.0, 65.7, and 14.3%, respectively, as evidenced by heteronuclear single quantum coherence analysis. This study provides a novel approach for obtaining high-purity lignin for catalytic depolymerization for oligomers and bifunctional monoaromatics production and leverages current cellulosic biorefinery technologies.

biomass analytics↗
DOE OSTI2023

Multi-scale Dynamics of Kinetic Turbulence in Weakly Collisional, High-Beta Plasmas (Final Report for DOE Grant DE-SC0019046)

This grant was a collaborative grant between Prof Matt Kunz (Princeton) and Prof. Eliot Quataert. Quataert was initially a faculty member at UC Berkeley when the grant was funded but moved to Princeton during the timeframe of this grant. Over the course of this grant we made major progress on understanding turbulence and multi-scale dynamics in weakly collisional high-beta plasmas. The most important contributions included: We developed one of the most compelling theoretical explanations for a decades-old puzzle at the heart of our understanding of the origin of the solar wind. The puzzle is that many of the observations of ion temperatures and distribution functions in the solar wind are consistent with cyclotron resonant heating. However, theoretical models of MHD turbulence in the solar wind show that most of the turbulent energy remains at low frequencies below the cyclotron frequency. In Squire et al. (2022), we showed, however, that in imbalanced turbulence (in which there is an asymmetry in the Alfven-wave flux in opposite directions along the magnetic field), which is the norm in the fast solar wind, the turbulent energy reaches a ‘bottleneck’ near the ion Larmor radius, and the amplitude and characteristic frequency of the fluctuations grow until the cyclotron frequency is reached.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1974

Absolute rate parameters for the reaction of ground state atomic oxygen with carbonyl sulfide

The rate parameters for the reaction of O(3P) with carbonyl sulfide, O(3P) + OCS yields CO + SO, have been determined directly by monitoring O(3P) using the flash photolysis-resonance fluorescence technique. The value for reaction rate was measured over a temperature range of 263-502 K and the data were fitted to an Arrhenius expression with good linearity. A comparison of the present results with those from previous studies of this reaction is also presented.

Klemm, R. B.↗
NASA NTRS1979

Advances in the stability of high precision crystal resonators

Advances in technology directed toward minimizing the temporal changes in frequency of crystal resonators are described. Specific emphasis is placed on reducing their susceptibility to temperature, acceleration, and other environmental effects.

Ballato, A.↗
NASA NTRS1995

Cosmic-ray heating of the interstellar gas

Cosmic rays streaming out of the Galaxy can become locked to resonantly excited Alfven waves as they pass through a region of increasing temperature at the disk-halo interface. A large fraction of the energy is approximately greater than 1 GeV cosmic rays goes into heating of the thermal gas via nonlinear Landau damping of the waves. This mode of cosmic-ray heating can balance radiative cooling for gas in the temperature range 10(exp 4.5) K approximately less than T approximately less than 10(exp 6), creating a thermal transition zone with a column density exceeding that of an ordinary conductive interface. This layer could be the site of much of the observed emission and absorption by highly ionized species such as C IV, N V, and O VI.

Begelman, Mitchell C.↗
NASA NTRS1997

Glycolonitrile oligomerization: structure of isolated oxazolines, potential heterocycles on the early earth

A study of glycolonitrile polymerization has led to the isolation and characterization of two 2,5-dihydro-4-aminooxazoles, 4 and 5. Previous reports have misassigned these structures as s-triazines or pyrimidines. X-ray diffraction analysis of crystals of 4 and an acetylated oxazole derivative of 5 (6) confirm the proposed structures. Ab initio computations are used to assess the relative thermodynamic stability of three trimer isomers (an s-triazine, an aminohydroxypyrimidine, and an aminooxazoline), and the results indicate that 4 is a novel kinetic product. Mechanistic considerations rationalize kinetic oxazole formation over the more customary triazine or pyrimidine trimers.

Non-NASA Center↗