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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Electric Field Control of Phonon Lifetimes and Thermal Conductivity in Relaxor-Based Ferroelectric

The demand for high energy efficiency drives intense interest in thermal-management technology. Phonons are a major contributor to heat transfer in solids and controlling them through external stimuli is a key challenge for thermal management due to their weak interactions with applied fields. We report significant changes in phonon transport with the application of an electric field over a broad temperature range in a relaxor-based ferroelectric using neutron-scattering and -transport measurements. Phonon lifetimes increase along the applied poling field and this results in a tripling of the thermal conductivity in that direction. We also observe a suppression of nanoscale antiferroelectric fluctuations along the poling direction and argue that this increases the phonon lifetimes. Our results highlight a promising yet underexplored route to realistic solid-state heat switching from electric-field-modified nanostructures altering the phonon lifetimes in disordered functional materials.

Phonons↗
DOE OSTI2024

Charge lifetime improvement of the Continuous Electron Beam Accelerator Facility photogun with a biased anode

GaAs photocathodes in dc high-voltage photoguns are highly susceptible to ion back-bombardment, which reduces the photocathode quantum efficiency and limits the useful operating lifetime for producing polarized electron beams. This paper demonstrates that applying a small positive bias to the photogun anode can significantly suppress ion back-bombardment and increase charge lifetime. This technique was studied extensively using the Continuous Electron Beam Accelerator Facility photogun, where highly polarized electron beams created using a strained-superlattice GaAs / GaAsP photocathode were used and charge lifetimes improved by almost a factor of 2. A new simulation code was developed to model ion production and tracking in order to better understand and explain the factors that led to the performance improvement. Results of the experiments and simulations are discussed in detail. Published by the American Physical Society 2024

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Phase-controlled improvement of photon lifetime in coupled superconducting cavities

High-quality cavities are crucial for various fundamental physical studies and applications. Here we find that by coupling two cavities directly or via a phase-tunable coupling channel, the photon lifetime of the local field can exceed that of the bare cavities. The cavity photon lifetime is modified by the phases of the initial states and the phase accumulation on the coupling channel, which affect the interference between cavities. In experiments, by coupling superconducting radio-frequency cavities via phase-tunable cables, we realize a factor of 2 improvement in the cavity photon lifetime. The results can bring rich revenue to quantum information science, sensing, and high-energy physics.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Lifetime measurements of excited states in neutron-rich 53 Ti: Benchmarking effective shell-model interactions

Level lifetimes of the yrast (5/2 - ) to 13/2 - states in the neutron-rich nucleus 53 Ti, produced in a multinucleon-transfer reaction, have been measured for the first time. The recoil distance Doppler-shift method was employed and lifetimes of the excited states were extracted by a lineshape analysis aided by GEANT4-based Monte-Carlo simulations. The experiment was performed at the Grand Accelerateur National d'Ions Lourds facility in Caen, France, by using the Advanced Gamma Tracking Array for the gamma-ray detection coupled to the large-acceptance variable mode spectrometer for an event-by-event particle identification and the Cologne plunger for deep-inelastic reactions. Reduced transition probabilities, deduced from the lifetimes, give new information on the nuclear structure of 53 Ti, and are used to benchmark different shell-model calculations using established interactions in the fp shell.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Lifetime measurements of 0 + states in Er 168 with the Doppler-shift attenuation method

Here, the lowest-lying shape oscillations of deformed nuclei have been described as quadrupole in nature (λ = 2), resulting in two types of vibrations or oscillations: β vibrations with oscillations along the symmetry axis (K π = 0 + ) and γ vibrations breaking axial symmetry with a projection of K π = 2 + on the symmetry axis. The γ vibration seems to be well characterized as the first K π = $2^+_1$ (or $2^+_γ$) band in deformed nuclei and exhibits a systematic behavior across the region. The nature of the K π = 0 + excitations, however, has remained poorly understood and has been open to debate for some decades. The goal of this work is to understand the nature of 0 + states observed in 168 Er through measurements of the lifetimes of these states and to determine if they are consistent with oscillations built on a deformed ground state, the minima of other coexisting shapes, single-particle states, or a mixture of effects. Lifetimes of excited states in the 168 Er nucleus were measured with the Doppler Shift Attenuation Method (DSAM) and the inelastic neutron scattering reaction, (n, n'γ), at the University of Kentucky Accelerator Laboratory. Numerous 0 + states had been observed by the (p, t) reaction. We confirm the 0 + states at 1217.2, 1421.5, 1833.6, 2364.9, 2392.1, and 2643.0 keV in 168 Er. We could not, however, support the previous assignments of 0 + levels at 2114.1, 2200.6, 2572.5, and 2617.4 keV. We report measured lifetimes for six confirmed 0 + excitations and additional members of 0 + bands. The results for 168 Er show that it is the third excited K π = 0 + ($0^+_4$) excitation that carries the collective strength and, therefore, the potential to be an oscillation on the ground state. This result is similar to the case in 166 Er, where it was also the $0^+_4$ state that exhibited greater collectivity than the first excited K π = 0 + band. The Delaroche et al. prediction for a collective K π = 0 + band is at E T =1.818 MeV which corresponds the third excited K π = 0 + band.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Measurement of the free neutron lifetime in a magneto-gravitational trap with in situ detection

Here, in this study, we publish three years of data from the UCNτ experiment performed at the Los Alamos Ultracold Neutron Facility at the Los Alamos Neutron Science Center. These data are in addition to our previously published data. Our goals in this paper are to better understand and quantify systematic uncertainties and to improve the lifetime statistical precision. We previously reported a value from our 2017–2018 data for the neutron lifetime of 877.75 ± 0.28 (statistical) +0.22–0.16 (systematic) s. We have collected an additional three years of data reported here for the first time. When all the data from UCNτ are averaged for 2017, 2018, 2020, 2021, and 2022, we report an updated value for the lifetime of 877.83 ± 0.22 (statistical)+0.20–0.17 (systematic) s. We utilized improved monitor detectors, reduced our correction due to UCN upscattering on residual gas, and employed four different UCN detector geometries both to reduce the correction required for rate dependence and to explore potential contributions due to phase space evolution.

Cabibbo-Kobayashi-Maskawa matrix↗
DOE OSTI2024

Constraints on light dark sector particles from lifetime difference of heavy neutral mesons

Heavy meson decays with missing energy in the final state offer interesting avenues to search for light invisible new physics such as dark matter (DM). In this context, we show that such new physics (NP) interactions also affect lifetime difference in neutral meson-antimeson mixing. We consider general dimension-six effective quark interactions involving a pair of DM particles and calculate their contributions to lifetime difference in beauty and charm meson systems. We use the latest data on mixing observables to constrain the relevant effective operators. We find that lifetime differences provide novel and complementary flavor constraints compared to those obtained from heavy meson decays. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2020

Lifetime of Almost Strong Edge-Mode Operators in One-Dimensional, Interacting, Symmetry Protected Topological Phases

Almost strong edge-mode operators arising at the boundaries of certain interacting one-dimensional symmetry protected topological phases with Z 2 symmetry have infinite temperature lifetimes that are nonperturbatively long in the integrability breaking terms, making them promising as bits for quantum information processing. We extract the lifetime of these edge-mode operators for small system sizes as well as in the thermodynamic limit. For the latter, a Lanczos scheme is employed to map the operator dynamics to a one-dimensional tight-binding model of a single particle in Krylov space. We suggest this model to be that of a spatially inhomogeneous Su-Schrieffer-Heeger model with a hopping amplitude that increases away from the boundary, and a dimerization that decreases away from the boundary. We associate this dimerized or staggered structure with the existence of the almost strong mode. Thus, the short time dynamics of the almost strong mode is that of the edge mode of the Su-Schrieffer-Heeger model, while the long time dynamics involves decay due to tunneling out of that mode, followed by chaotic operator spreading. Furthermore, we show that competing scattering processes can lead to interference effects that can significantly enhance the lifetime.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Reduction of bright exciton lifetimes by radiation-induced disorder

Quantum-radiative decay is a fundamental process in many optoelectronic systems such as laser diodes and solar cells. The bright exciton lifetime is a critical factor in determining the performance of these systems. Motivated by the ever-increasing need for laser systems in space and nuclear applications, we develop a many-particle approach to predict the radiative lifetime under harsh radiation environments. Here, using GaAs as a model system, we find that radiation-induced band tailing reduces the bright exciton lifetime. This result shows that the efficiency of radiative recombination, in addition to nonradiative recombination, can be affected by ionization radiation. Our approach enables a detailed understanding of the interplay between correlation, localization, and radiation that affect the performance of gain media.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Carrier Lifetime as a Function of Se Content for CdSexTe1-x Films Grown on Al2O3 and MgZnO

Time-resolved photoluminescence (TRPL) with two excitation wavelengths – 670 (standard) and 405 nm – was used to examine the effect on carrier lifetime of two significant recent advances in CdTe: the incorporation of Se to form graded CdSe x Te 1-x and the use of Mg y Zn 1-y O buffers. The two excitation wavelengths probe depths of approximately 130 and 35 nm, respectively, and their comparison helps differentiate interface and bulk contributions to carrier lifetime. It was found that x = 0.2 Se was required to obtain lifetime improvements, primarily in the bulk. Additionally, TRPL traces for Mg y Zn 1-y O/CdSe x Te 1-x samples showed fast initial decay followed by a long-lived tail, which may be indicative of trap-dominated recombination. This behavior was not present for CdSe x Te 1-x films grown on Al 2 O 3 , which is currently state-of-the-art for surface passivation in CdTe. This indicates that further work is required to sufficiently passivate the front interface.

cadmium telluride↗
DOE OSTI2020

Effect of Air Plasma Sprayed Flash Bond Coatings on Furnace Cycle Lifetime of Disks and Rods

Air plasma sprayed (APS) flash coatings on high velocity oxygen fuel (HVOF) bond coatings are well known to extend the lifetime of thermal barrier coatings (TBCs). Recent work compared flash coatings of NiCoCrAlY and NiCoCrAlYHfSi applied to both rods and disk substrates of alloy 247. For rod specimens, 100 h cycles were used at 1100 °C in wet air. Both flash coatings significantly improved the lifetime compared to HVOF-only and vacuum plasma spray (VPS)-only MCrAlY bond coatings with no statistical difference between the two flash coatings. For disk specimens tested in 1 h cycles at 1100 °C in wet air, the NiCoCrAlY flash coating significantly outperformed an HVOF-only NiCoCrAlYHfSi bond coating and a NiCoCrAlYHfSi flash coating. The flash coatings formed a mixed oxide-metal zone that appeared to inhibit crack formation and therefore extend lifetime. In addition to the flash coating increasing the bond coating roughness, the underlying HVOF layer acted as a source of Al for this intermixed zone and prevented the oxide from penetrating deeper into the bond coating. Here, the lower Y+Hf content in the Y-only flash coating appeared to minimize oxidation in the flash layer, thereby increasing the benefit compared to a NiCoCrAlYHfSi flash coating.

42 ENGINEERING↗
DOE OSTI2023

Lifetime measurement of excited states in 116 Xe

Lifetimes of excited states in 116 Xe were measured using the recoil-distance Doppler-shift technique. Excited 116 Xe nuclei were populated in the fusion-evaporation reaction 102 Pd( 16 O,2n) 116 Xe. Lifetimes of the $2^{+}_{1}$ and $4^{+}_{1}$ states were evaluated using the differential decay-curve method with $\gamma$-$\gamma$-coincidence data as well as lifetimes of the $6^{+}_{1}$ and $7^{-}_{1}$ states using simulations of spectra considering Doppler-shift attenuation effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Lifetimes of negative parity states in 162 Dy

Lifetimes of excited states in 162 Dy were measured using the (n,n’$γ$) reaction with the Doppler-Shift Attenuation Method (DSAM) at the University of Kentucky’s Accelerator Laboratory. A total of eighteen level lifetimes were obtained, including eleven negative-parity states, seven of which are new. These measurements significantly expand the experimental database of transition probabilities for negative-parity bands in the well-deformed rare earth region of nuclei. The extracted B(E1) and B(E2) values reveal enhanced interband E1 (10 -3 or 10 -4 ) W.u. and E2 strengths (several W.u.) between negative- and positive parity bands, particularly for the K π = $2^{-}_{1,2}$ bands decaying to the K π = $2^+_γ$ band, consistent with signatures of octupole-quadrupole coupling. In contrast, the K π = $0^{-}_1$ and K π = $1^{-}_3$ bands, which exhibit strong E1 transitions to the ground state band, are indicative of octupole-vibrational excitations built on the deformed ground state. Comparison of transition rates with Alaga rules supports this interpretation and distinguishes collective excitations from likely quasi-particle states. These new results establish 162 Dy as the most extensively characterized rare-earth nucleus for negative parity lifetimes and provide critical experimental benchmarks for theoretical models.

Aprahamian, A. [University of Notre Dame, IN (Unit↗
DOE OSTI2023

BLAST-Lite (Battery Lifetime Analysis and Simulation Tool - Lite) [SWR-22-69] Related to: BLAST aka: BLAST-Py

Battery Lifetime Analysis and Simulation Toolsuite (BLAST) provides a library of battery lifetime and degradation models for various commercial lithium-ion batteries from recent years. Degradation models are identified from publicly available lab-based aging data using NREL's battery life model identification toolkit. The battery life models predicted the expected lifetime of batteries used in mobile or stationary applications as functions of their temperature and use (state-of-charge, depth-of-discharge, and charge/discharge rates). Model implementation is in both Python and MATLAB programming languages. The MATLAB code also provides example applications (stationary storage and EV), climate data, and simple thermal management options. For more information on battery health diagnostics, prediction, and optimization, see NREL's Battery Lifespan webpage.

Smith, Kandler↗
DOE OSTI2020

Long interior carrier lifetime in selective-area InAs nanowires on silicon

Catalyst-free, position-controlled indium arsenide (InAs) nanowires (NWs) of variable diameters were grown on Si (111) by selective-area epitaxy (SAE). Ultrafast pump-probe spectroscopy was conducted, from which carrier recombination mechanisms on the NW surface and interior were resolved and characterized. NWs grown using SAE demonstrated high optical quality, showing minority carrier lifetimes more than two-fold longer than that of the randomly-positioned (RP) NWs. The extracted SAE-InAs NW interior recombination lifetime was found to be as long as 7.2 ns , 13X longer than previous measurements on RP-NWs; and the surface recombination velocity 4154 cm · s - 1 . Transmission electron microscopy revealed a high density of stacking defects within the NWs, suggesting that interior recombination lifetime can be further increased by improving NW interior crystalline quality.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Improving the Operational Lifetime of the CEBAF Photo-Gun by Anode Biasing

The operating lifetime of GaAs-based photocathodes in DC high voltage electron photo-guns is dominated by the ionization rate of residual beamline gas molecules. In this work, experiments were performed to quantify the improvement in photocathode charge lifetime by biasing the photo-gun anode with a positive voltage, which repels ions generated downstream of the anode. The photo-cathode charge lifetime improved by almost a factor of two when the anode was biased compared to the usual grounded configuration. Simulations were performed using the particle tracking code General Particle Tracer (GPT) with a new custom element. The simulation results showed that both the number and energy of ions play a role in the pattern of QE degradation. The experiment results and conclusions supported by GPT simulations will be presented.

Yoskowitz, J. T.↗
DOE OSTI2021

2020 Report - SRNL Aging and Lifetimes program tritium aging studies on structural alloys

This report documents work performed in calendar year 2020 at SRNL in support of the Aging and Lifetimes program. This work is part of an on-going collaboration between SRNL and SNL to understand tritium embrittlement of structural metals in Gas Transfer System reservoirs which informs lifetime assessments and lifetime predictions. In this effort, test coupons are precharged with tritium and allowed to age in a freezer to minimize tritium egress and allow for born-in helium levels to systematically increase. Coupons are then removed periodically and tested to develop an understanding of how mechanical properties degrade as helium levels increase. This report summarizes test results from coupons which are in various stages of aging as they were tritium precharged in previous years.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Development of an Open-source Alloy Selection and Lifetime Assessment Tool for Structural Components in CSP

Lack of sufficient data on high temperature mechanical and corrosion behavior of structural materials is a huge barrier in the technological maturity of current and future Concentrating Solar Power (CSP) technologies. Rapid development and selection of materials cannot be achieved by expensive and time-consuming acquisition of experimental data. The goal of the proposed work is development of an open-source alloy selection and lifetime prediction tool that will integrate validated physics-based models to describe influence of temperature, alloy composition, environment and component geometry (thickness) on mechanical and corrosion behavior of Ni and Fe-based alloys employed in molten salts/sCO 2 heat exchangers. This one-year project leveraged the extensive dataset on the creep\corrosion behavior of candidate materials generated at ORNL through past projects and input from current collaborations with industrial partners. Based on previous experience and the feedback provided by industry (Brayton Energy and Echogen), three candidate materials of interest, Ni-based alloys 740H, 282 and 625 and application-specific operating conditions (max. temperature of 730 °C and stress of 150 MPa) were identified for the heat exchanger. An extensive corrosion and creep dataset was assimilated for the relevant operating conditions and was supported by detailed characterization of about 100 metallographic cross-sections. The corrosion dataset consisted of scanning electron microscopy images (secondary electron and backscatter electron), measured concentration profiles of alloying elements using energy dispersive X-ray spectroscopy (EDS), widths of denuded zones (dissolution of strengthening phases) and depths of attack in molten KCl-MgCl 2 mixtures using image analyses. The creep dataset comprised of creep rupture data and creep strain curves (for 740H and 282). Coupled thermodynamic-kinetic microstructure-based models were employed to predict the stress-corrosion induced compositional and phase evolutions in the alloy during operation under the identified operating conditions. Reduced order models were developed from advanced physics-based models and were integrated in a user-friendly alloy selection tool. The corrosion model was able to predict the time to a critical Cr concentration at the oxide/alloy interface (chemical lifetime) within ±10% (1 standard deviation) of typical statistical variation in corrosion tests and EDS measurement errors (±0.5 wt%). The initial scope of the project was limited to predict creep rupture times (Larson-Miller parameter). Based on the input provided by industry, the mechanical lifetime of the heat exchanger is governed by accumulated creep strains (2%) rather than creep rupture. To be able to predict the times to specific creep strains, a more extensive creep model development was undertaken largely beyond the initial scope of the project. The continuum damage mechanics creep model was able to predict times to 2% creep strain, t 2% with an accuracy of ±500h. Ultimately, a screening protocol for SiC was generated to demonstrate the pathway for integration of one of the currently immature materials from a commercial adoption standpoint in the current material evaluation tool. The modeling tool developed here is accessible to the science community and stakeholders and lays the foundation for methods that will enable a rapid evaluation of optimum materials for CSP applications and reliable prediction of material degradation thereby considerably reducing operational costs, improving reliability and increasing overhaul intervals. However, the complete potential of such a tool to include a wider range of materials and test conditions can only be realized with a more concentrated combined experimental-characterization-computation effort.

14 SOLAR ENERGY↗