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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Comments on 'Pulsed electron beam emission in space' by Neubert et al. (1988)

Using the potentials measured by the Spacelab's Charge and Current Probe during beam ejections and the signature of the harmonic emissions generated by pulsed electron beams, Neubert et al. (1988) presented evidence that overdense electron beams (with electron density above 150,000/cu cm) can escape the near vicinity of the Shuttle. This paper supplements these results by presenting a further indication of the beam escape and propagation out to at least 200 m, using the whistler-mode wave signature obtained during the SL-12 electron beam ejection which occurred on DOY 213 of 1985 from 03:30 to 03:37 UT. The combined results support the hypothesis that overdense electron beams can and will escape from a spacecraft, contrary to predictions based upon idealized simulations of the injection process.

Farrell, W. M.↗
DOE OSTI2023

Measurement of differential distributions of B → D*$\ell\bar{v}_{\ell}$ and implications on | V cb |

We present a measurement of the differential shapes of exclusive B → D*$\ell\bar{v}_{\ell}$ (B = B - , $\bar{B}$ 0 and $\ell$ = e, μ) decays with hadronic tag-side reconstruction for the full 711 fb -1 Belle dataset. We extract the Caprini-Lellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) form factor parameters and use an external input for the absolute branching fractions to determine the Cabibbo-Kobayashi-Maskawa matrix element and find |V cb | CLN = (40.2 ± 0.9) x 10 -3 and |V cb | BGL = (40.7 ± 1.0) x 10 -3 with the zero-recoil lattice QCD point $\mathcal{F}$(1) = 0.906 ± 0.013. We also perform a study of the impact of beyond zero-recoil lattice QCD calculations on the |V cb | determinations. Additionally, we present the lepton-flavor universality ratio R eμ = $\mathcal{B}$(B → D*e$\bar{v}$ e )/$\mathcal{B}$(B → D*μ$\bar{v}$ μ ) = 0.993 ± 0.023 ± 0.023, the electron and muon forwardbackward asymmetry and their difference ΔA FB = 0.028 ± 0.028 ± 0.008, and the electron and muon D* longitudinal polarization fraction and their difference ΔF$^{D*}_L$ = 0.030 ± 0.025 ± 0.007. The uncertainties quoted correspond to the statistical and systematic uncertainties, respectively.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Generative Models for Crystalline Materials

Understanding structure-property relationships in materials is fundamental in condensed matter physics and materials science. Over the past few years, machine learning (ML) has emerged as a powerful tool for advancing this understanding and accelerating materials discovery. Early ML approaches primarily focused on constructing and screening large material spaces to identify promising candidates for various applications. More recently, research efforts have increasingly shifted toward generating crystal structures using end-to-end generative models. This review analyzes the current state of generative modeling for crystal structure prediction and de novo generation. It examines crystal representations, outlines the generative models used to design crystal structures, and evaluates their respective strengths and limitations. Furthermore, the review highlights experimental considerations for evaluating generated structures and provides recommendations for suitable existing software tools. Emerging topics, such as modeling disorder and defects, integration in advanced characterization, incorporating synthetic feasibility constraints, and model explainability are explored. Ultimately, this work aims to inform both experimental scientists looking to adapt suitable ML models to their specific circumstances and ML specialists seeking to understand the unique challenges related to inverse materials design and discovery.

Metni, Houssam [Karlsruhe Inst. of Technology (KIT↗
DOE OSTI2026

Super-leading logarithms in top-quark pair production at hadron colliders

To date, the appearance and resummation of “super-leading” logarithms in hadron-hadron collisions has been studied only for massless parton states. We extend the formalism to include an arbitrary number of massive final states. We derive the corresponding anomalous dimension and identify an additional Coulomb phase that gives rise to a new source of super-leading logarithms. We then perform a systematic leading-logarithmic resummation of these contributions for 2 → M processes. Finally, we analyze the numerical impact in partonic scattering processes for $t\bar{t}$ production, including a treatment of the Sommerfeld enhancement observed near threshold.

Effective Field Theories of QCD↗
DOE OSTI2025

Feature review of photovoltaic modeling software utilizing blind performance assessment

While confidence in photovoltaic (PV) modeling software has always been essential, the rapid pace of new PV plant developments makes accuracy and credibility more critical than ever. Independent assessments, particularly through blind modeling comparisons, are therefore necessary to ensure unbiased benchmarking across PV modeling software. Previous studies have been limited by a narrow range of models compared, anonymized results, or system size. This study presents results from the first-ever onymous blind modeling comparison, evaluated using both lab- and utility-scale fixed-tilt, monofacial, south-facing systems at sub-hourly time intervals. Seven commercially used PV software tools were compared: 3E SynaptiQ, PlantPredict, PVsyst, RatedPower, SAM, SolarFarmer, and Solargis Evaluate. Predictions were submitted directly by software representatives, providing unique insights into each software’s implementation and resulting prediction behavior. Notable features, including plane-of-array (POA) transposition model, module temperature model, shading model, and performance model were analyzed and compared. Four summary tables compile these features of the software, serving as a resource to help users understand the methodological differences and select the most suitable software for their applications. The software tools show deviations from mean error in annual yield up to 2.5 % in the lab-scale system, increasing to 6.0 % for the utility-scale system. These differences arise from a combination of user decisions and the inherent behavior of the software, indicating the need for continuous and rigorous validation of modeling methods using these software tools against complex, real-world systems.

14 SOLAR ENERGY↗
DOE OSTI2023

New physics searches at kaon and hyperon factories

Rare meson decays are among the most sensitive probes of both heavy and light new physics. Among them, new physics searches using kaons benefit from their small total decay widths and the availability of very large datasets. On the other hand, useful complementary information is provided by hyperon decay measurements. We summarize the relevant phenomenological models and the status of the searches in a comprehensive list of kaon and hyperon decay channels. We identify new search strategies for under-explored signatures, and demonstrate that the improved sensitivities from current and next-generation experiments could lead to a qualitative leap in the exploration of light dark sectors.

NA62 experiment↗
DOE OSTI2023

50 Years of quantum chromodynamics

Quantum Chromodynamics, the theory of quarks and gluons, whose interactions can be described by a local SU(3) gauge symmetry with charges called “color quantum numbers”, is reviewed; the goal of this review is to provide advanced Ph.D. students a comprehensive handbook, helpful for their research. When QCD was “discovered” 50 years ago, the idea that quarks could exist, but not be observed, left most physicists unconvinced. Then, with the discovery of charmonium in 1974 and the explanation of its excited states using the Cornell potential, consisting of the sum of a Coulomb-like attraction and a long range linear confining potential, the theory was suddenly widely accepted. This paradigm shift is now referred to as the November revolution. It had been anticipated by the observation of scaling in deep inelastic scattering, and was followed by the discovery of gluons in three-jet events.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Two-loop contributions of axion-like particles to electromagnetic and chromomagnetic form factors

Abstract Axions and axion-like particles emerge in many models for physics beyond the Standard Model. Thus, they have gained increasing research interest in both experimental and theoretical physics apart from their original proposition as a solution to the strong CP -problem. Among other aspects it has recently been shown that ALPs can potentially provide a solution to the long-lasting discrepancy between theory and experiment of the anomalous magnetic moment of the muon. Provided that the ALP has flavor-violating couplings to leptons, they can also mediate flavor-violating decays like $$\mu \rightarrow e\gamma $$ μ → e γ . Both processes are mediated through related form factors that we compute to two-loop order. We further show numerical implications of our calculations and how they might affect constraints on ALP couplings derived from experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRSDate not supplied

Seasons of Syn

Explore the source record for details and available documents.

Kristen R. Hunter‐Cevera↗
NASA NTRS1970

A proposed laser measurement system for determining surface contour

Electro-optical system can scan a large /100 ft./ antenna in 30 seconds. Comparison of the reflected signal with a reference signal from a Pockel-cell modulator driver yields a signal that can be correlated with the distance covered by the laser. A scanning arrangement then enables contour measurement.

Neubert, H. D.↗
NASA NTRS1973

Development of low-shock pyrotechnic separation nuts

Performance demonstrations and comparisons were made on six flight type pyrotechnic separation nut designs, two of which are standard designs in current use, and four of which were designed to produce low shock on actuation. Although the shock performances of the four low shock designs are considerably lower than the standard designs, some penalties may be incurred in increased volume, weight, or complexity. These nuts, and how they are installed, can significantly influence the pyrotechnic shock created in spacecraft structures. A high response monitoring system has been developed and demonstrated to provide accurate performance comparisons for pyrotechnic separation nuts.

Bement, L. J.↗
NASA NTRS1973

Measurement and analysis of force-time outputs of pyrotechnic nuts

The dynamic loadings produced by two standard pyrotechnic nuts were compared with loadings produced by four recently developed low-shock nuts. The nuts were manufactured by separate contractors. Each nut was given a number designation, the number having no special significance. The results show that the use of the Hopkinson bar to measure force-time outputs of the nuts at stud and housing sides aided greatly in understanding the events occurring in the nuts. Acceleration data appear to be dependable, for the most part, but of more limited value. The low-shock designs show considerable improvement over the standard designs above 4,000 Hz when the results are plotted in shock spectrum form. They involve some penalties with regard to weight and cost.

Neubert, V. H.↗
NASA NTRS1983

High-latitude stratospheric winds near summer solstice - The diurnal and semidiurnal solar tides

A technique for studying winds and tides at altitudes of approximately 30 km is the continuous and precise tracking of zero-pressure, stratospheric balloons. The CONSOL navigation system allows tracking of a balloon over the North Atlantic for two days or longer. Tidal wind data from 14 balloon trajectories (approximately 670 balloon hours) are presented and compared with theoretical predictions.

Neubert, T.↗
NASA NTRS1986

Waves generated during electron beam emissions from the Space Shuttle

Observations from the SEPAC (Space Experiments with Particle Accelerators) experiment on Spacelab 1 Shuttle mission of waves generated during electron beam emissions are presented. The dependence of the wave intensity on the beam parameters and the Shuttle attitude is outlined, and the shape of the wave spectra are discussed. It is found that the noise in the 0.75- to 10 kHz band has a spectral shape that can be characterized by an f exp -n law, and that the VLF signal level depends on the beam angle to the magnetic field, the strongest emissions being observed for parallel beams. These features are found to be consistent with a drift wave instability.

Neubert, T.↗
NASA NTRS1987

Resonance between coherent whistler mode waves and electrons in the topside ionosphere

Landau resonance and cyclotron resonance of coherent whistler mode waves and energetic electrons are explored for magnetoplasmas with appreciable gradients in the plasma density and magnetic field strength. It is shown that in the topside ionosphere of the earth near the ion transition height the gradients in plasma density and magnetic field strength along a magnetic field line may match in a way which enhances both Landau and cyclotron interactions between waves and electrons at the loss cone pitch angle. The pitch angle scattering induced by a signal from a ground-based VLF transmitter in the ionosphere above the transmitter has been estimated and compared to the pitch angle scattering induced by naturally occurring ELF hiss through cyclotron resonance. It is found that the expected scattering due to plasmapheric hiss is an order of magnitude larger than that due to Landau resonance in the topside ionosphere. Pitch angle scattering due to cyclotron resonance in the topside ionosphere, however, may be larger by a factor of 2. It is suggested that the 'fast Trimpi' effect may be caused by a cyclotron resonance interaction in the topside ionosphere.

Neubert, T.↗
NASA NTRS1987

Measurement, data analysis and prediction of pyrotechnic shock from pin-pullers and separation joints

To evaluate the potential for spacecraft damage caused by activation of pyrotechnic mechanisms, pyrotechnic shock tests were conducted on three configurations: pin-pullers on an orthogonal double Hopkinson bar arrangement, pin-pullers on a mock-up of the HALOE (Halogen Occultation Experiment) structure, and a section of separation joint on a single Hopkinson bar. Strains and accelerations were measured. The strains were converted to output stresses, forces and moments. Acceleration shock response spectra are presented for both acceleration- and force-time signals. The devices were attached to the Hopkinson bars with adaptors, which are typical of attachments used in practice. In order to predict the effect of the adaptors, finite element models of the adaptor-bar combinations were analyzed and results are presented with regard to grid size, time interval, and frequency range required to predict the response to pulses of 10 and 100 microsecond duration.

Evans, Maria J.↗