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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Interactions among decaying leaf litter, root litter and soil organic matter vary with mycorrhizal type

Abstract Root‐derived inputs are increasingly viewed as primary controls of soil organic matter (SOM) formation; however, we have a limited understanding of how root decay rates depend on soil factors, and how decaying roots influence the breakdown of leaf litter and SOM. We incubated root and leaf litter (alone and in combination) from arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) trees in soils collected from forest plots dominated by AM and ECM trees in a factorial design. In each microcosm, we quantified litter decay rates and the effects of decaying litters on soil C balance. We hypothesized that (1) AM root litters would decompose faster than ECM root litters, (2) root litter decay would be greatest when decomposed in “home” soils (e.g. AM litters in AM soils and ECM litters in ECM soils) and (3) root and leaf litters would decompose faster when decaying in the same microcosms than when decaying in separate microcosms, resulting in the largest CO 2 losses. Overall, AM root litter decomposed faster than ECM root litter, and the magnitude of this effect depended on soil origin. AM litters decayed fastest in AM soils, but ECM and mixed AM–ECM litters were unaffected by soil origin. Decaying roots increased leaf litter mass loss, but only in microcosms containing soils of the same origin (e.g. AM litters in AM soils; mixed litters in mixed soils). Carbon losses were dominated by microbial respiration, and the magnitude of this flux depended on litter type and soil origin. When leaves and roots decayed together, respiratory losses exceeded those from microcosms containing leaves and roots alone, with the largest losses occurring in each litters' “home” soil. In AM soils, elevated losses were driven by roots accelerating leaf decay, while in ECM soils, elevated losses resulted from roots and leaves accelerating the decay of SOM; in mixed soils, root‐induced increases in leaf and SOM decay contributed to elevated C losses. Synthesis . Our results suggest that root, leaf and SOM decay are intertwined, and that measurements of these processes in isolation may lead to incorrect estimates of the magnitude and source of C losses from soils.

Jacobs, Luke M.↗
DOE OSTI2020

Precision measurement of the neutral pion lifetime

The explicit breaking of the axial symmetry by quantum fluctuations gives rise to the so-called axial anomaly. This phenomenon is solely responsible for the decay of the neutral pion π0 into two photons (γγ), leading to its unusually short lifetime. Here, we precisely measured the decay width Γ of the π 0 → γγ process. The differential cross sections for π0 photoproduction at forward angles were measured on two targets, carbon-12 and silicon-28, yielding Γ(π 0 → γγ)=7.798±0.056(stat.)±0.109(syst.) eV, where stat. denotes the statistical uncertainty and syst. the systematic uncertainty. We combined the results of this and an earlier experiment to generate a weighted average of Γ(π 0 → γγ)=7.802±0.052(stat.)±0.105(syst.) eV. Our final result has a total uncertainty of 1.50% and confirms the prediction based on the chiral anomaly in quantum chromodynamics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Aluminum-clad Spent Nuclear Fuel Engineering Scale Drying Experiment Design

The purpose of this document is to provide the technical specifications for the Engineering Scale Design for the drying tests of aluminum-clad spent nuclear fuel (ASNF). The engineering scale design is to accommodate both forced helium drying (FHD) as well as vacuum drying. The experiments will employ mock ASNF assemblies with a limited number of chemically treated aluminum plates to simulate the aluminum hydroxides found on ASNF. The goal here is to understand the transformation that may occur in plates including the loss of chemisorbed water and changes in morphology. Physiosorbed and bulk water found in experiments will be dried in the process and the effect on drying operations noted. Decay heat will be simulated in one assembly using a custom designed resistance heating element. A typical radial arrangement of assemblies will be employed using a modified Type 1A Basket design. For the chamber/canister, a single assembly layer with full radial dimension will be employed. Modifications to the standard canister design and configuration include the addition of a siphon tube to enable recirculation of hot gas for forced helium drying. A ring of ports/flanges are added near the top of the chamber to accommodate the feedthroughs for instrumentation and power needed for the experiment and data collection. Four viewports are added to the main section of the chamber with two in line with one of the fuel assembly and siphon tube. The other two viewports are on the opposite side of the chamber. The purpose here is to provide the option of thermal imaging in addition to the nearly four dozen thermocouples available inside the chamber. Modeling of the chamber, basket, and mock ASNF assemblies was conducted to estimate temperature distributions throughout the chamber during forced helium drying and over the anticipated drying period. This modeling was used as input to decisions on the Engineering Scale Design. Work on modeling continues in the period during setup and testing to develop preliminary drying models. Analysis of experimental results will later be used to validate these and subsequent models.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

International Collaboration Activities on Engineered Barrier Systems

The Spent Fuel Waste Science and Technology (SFWST) campaign from the DOE Fuel Cycle and Technology (FCT) program has been engaging in international collaborations between repository R&D programs for nuclear waste disposal to leverage on the extensive research investigations and laboratory/field data of engineered barrier system (EBS) components (e.g., near-field) and characterization of transport phenomena in the host rock (e.g., far-field) processes from state-of-the-art underground research laboratories (URL) experiments. Thermal heating from radionuclide decay in the waste canisters will generate increases in temperature that will drive chemical and transport processes in the near- and far-field domains of the repository. URL sites provide the ideal setting to conduct heater test experiments to simulate the thermal effects of heat-generating nuclear waste in disposal galleries and surrounding host rock.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1974

Cosmic electrons

The published literature on cosmic electrons is summarized. The primary and secondary sources of cosmic electrons are discussed, and the propagation of the electrons in the interstellar medium is studied with respect to energy loss mechanisms, age distributions, and spectral modifications during flight. Various portions of the electron and positron spectra are then considered in relation to problems of astrophysics. New information is presented on such topics as the origin of low-energy positrons, the decay kinematics of the pi-mu-e process, the application of age distributions for nuclear cosmic rays to cosmic electrons, and the possibility of nonidentical sources for cosmic electrons and protons.

Ramaty, R.↗
NASA NTRS1991

Mesoscale characteristics of a monsoon rainband

A Doppler-radar-based case study of a monsoonal rainband (MRB) observed on the evening of January 12, 1990 near Darwin, Austrialia, is presented. Convective and mesoscale circulation features of this system are elucidated. The structure of the MRB is similar to the conceptual model of Houze (1989). The convergence profiles observed in the stratiform region differed considerably from the classical Houze model. Divergence and not convergence existed at heights of 3-6 km. It is suggested that in the MRB stratiform region, consistent with the observed rearward advection of decaying convective cells, the observed mesoscale updraft/downdraft configuration is a result of decaying convection and not a separately evolving mesoscale process.

Keenan, T. D.↗
NASA NTRS1993

Radiations from hot nuclei

The investigation indicates that nuclei with excitation energy of a few hundred MeV to BeV are more likely to radiate hot nuclear clusters than neutrons. These daughter clusters could, furthermore, de-excite emitting other hot nuclei, and the chain continues until these nuclei cool off sufficiently to evaporate primarily neutrons. A few GeV excited nuclei could radiate elementary particles preferentially over neutrons. Impact of space radiation with materials (for example, spacecraft) produces highly excited nuclei which cool down emitting electromagnetic and particle radiations. At a few MeV excitation energy, neutron emission becomes more dominant than gamma-ray emission and one often attributes the cooling to take place by successive neutron decay. However, a recent experiment studying the cooling process of 396 MeV excited Hg-190 casts some doubt on this thinking, and the purpose of this investigation is to explore the possibility of other types of nuclear emission which might out-compete with neutron evaporation.

Malik, F. Bary↗
DOE OSTI2021

Bulk viscosity from Urca processes: npeμ matter in the neutrino-trapped regime

In this work, we extend our previous study of the bulk viscosity of hot and dense npe matter induced by the Urca process in the neutrino trapped regime to npeμ matter by adding the muonic Urca processes as well as the purely leptonic electroweak processes involving electron-muon transition. Here, the nuclear matter is modeled in a relativistic density functional approach with two different parametrizations which predict neutrino dominated matter (DDME2 model) and anti-neutrino dominated matter (NL3 model) at temperatures for which neutrinos/anti-neutrinos are trapped. In the case of neutrino-dominated matter, the main equilibration mechanism is lepton capture, whereas in the case of antineutrino-dominated matter this is due to neutron decay. We find that the equilibration rates of Urca processes are higher than that of the pure leptonic processes, which implies that the Urca bulk viscosity can be computed with the leptonic reactions assumed to be frozen. We find that the bulk viscosity decreases with temperature as ζ~T –2 at moderate temperatures. At high temperatures this scaling breaks down by sharp drops of the bulk viscosity close to the temperature where the proton fraction is density-independent and the matter becomes scale-invariant. This occurs also when the matter undergoes a transition from the antineutrino-dominated regime to the neutrino-dominated regime where the bulk viscosity attains a local maximum. We also estimate the bulk viscous dissipation timescales and find that these are in the range ≳ 1 s for temperatures above the neutrino trapping temperature. These timescales would be relevant only for long-lived objects formed in binary neutron star mergers and hot proto-neutron stars formed in core-collapse supernovas.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Search for η c ( 2 S ) → ω ω and ω ϕ and measurements of χ c J → ω ω and ω ϕ in ψ ( 2 S ) radiative processes

Using ( 2712 ± 14 ) × 10 6 ψ ( 2 S ) events collected with the BESIII detector at the BEPCII collider, we search for the decays η c ( 2 S ) → ω ω and η c ( 2 S ) → ω ϕ via the process ψ ( 2 S ) → γ η c ( 2 S ) . No statistically significant signals are observed. The upper limits of their product branching fractions at the 90% confidence level are determined to be B ( ψ ( 2 S ) → γ η c ( 2 S ) , η c ( 2 S ) → ω ω ) < 1.04 × 10 − 6 and B ( ψ ( 2 S ) → γ η c ( 2 S ) , η c ( 2 S ) → ω ϕ ) < 1.85 × 10 − 7 , respectively. We also update the branching fractions of χ c J → ω ω and χ c J → ω ϕ via the ψ ( 2 S ) → γ χ c J transition. Their branching fractions are determined to be B ( χ c 0 → ω ω ) = ( 10.66 ± 0.11 ± 0.57 ) × 10 − 4 , B ( χ c 1 → ω ω ) = ( 6.43 ± 0.07 ± 0.31 ) × 10 − 4 , B ( χ c 2 → ω ω ) = ( 8.75 ± 0.08 ± 0.42 ) × 10 − 4 , B ( χ c 0 → ω ϕ ) = ( 1.18 ± 0.03 ± 0.07 ) × 10 − 4 , B ( χ c 1 → ω ϕ ) = ( 2.04 ± 0.15 ± 0.11 ) × 10 − 5 , and B ( χ c 2 → ω ϕ ) = ( 9.58 ± 1.07 ± 0.76 ) × 10 − 6 , where the first uncertainties are statistical and the second are systematic. Published by the American Physical Society 2025

Ablikim, M.↗
DOE OSTI2017

FISPACT-II: An Advanced Simulation System for Activation, Transmutation and Material Modelling

Fispact-II is a code system and library database for modelling activation-transmutation processes, depletion-burn-up, time dependent inventory and radiation damage source terms caused by nuclear reactions and decays. The Fispact-II code, written in object-style Fortran, follows the evolution of material irradiated by neutrons, alphas, gammas, protons, or deuterons, and provides a wide range of derived radiological output quantities to satisfy most needs for nuclear applications. It can be used with any ENDF-compliant group library data for nuclear reactions, particle-induced and spontaneous fission yields, and radioactive decay (including but not limited to TENDL-2015, ENDF/B-VII.1, JEFF-3.2, JENDL-4.0u, CENDL-3.1 processed into fine-group-structure files, GEFY-5.2 and UKDD-16), as well as resolved and unresolved resonance range probability tables for self-shielding corrections and updated radiological hazard indices. The code has many novel features including: extension of the energy range up to 1 GeV; additional neutron physics including self-shielding effects, temperature dependence, thin and thick target yields; pathway analysis; and sensitivity and uncertainty quantification and propagation using full covariance data. The latest ENDF libraries such as TENDL encompass thousands of target isotopes. Nuclear data libraries for Fispact-II are prepared from these using processing codes PREPRO, NJOY and CALENDF. These data include resonance parameters, cross sections with covariances, probability tables in the resonance ranges, PKA spectra, kerma, dpa, gas and radionuclide production and energy-dependent fission yields, supplemented with all 27 decay types. All such data for the five most important incident particles are provided in evaluated data tables. The Fispact-II simulation software is described in detail in this paper, together with the nuclear data libraries. The Fispact-II system also includes several utility programs for code-use optimisation, visualisation and production of secondary radiological quantities. Included in the paper are summaries of results from the suite of verification and validation reports available with the code.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Nuclear data for r-process models from ion trap measurements

To truly understand how elements are created in the universe via the astrophysical r process, accurate nuclear data are required. Historically, the isotopes involved in the r process have been difficult to access for study, but the development of new facilities and measurement techniques have put many of the r-process isotopes within reach. This paper will discuss the new CARIBU facility at Argonne National Laboratory and two pieces of experimental equipment, the Beta-decay Paul Trap and the Canadian Penning Trap, that will dramatically increase the nuclear data available for models of the astrophysical r process.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Simplification of femtosecond transient absorption microscopy data from CH 3 NH 3 PbI 3 perovskite thin films into decay associated amplitude maps

Our work aims to simplify multi-dimensional femtosecond transient absorption microscopy (TAM) data into decay associated amplitude maps that describe the spatial distributions of dynamical processes occurring on various characteristic timescales. Application of this method to TAM data obtained from a model methyl-ammonium lead iodide (CH 3 NH 3 PbI 3 ) perovskite thin film allows us to simplify the dataset consisting of a 68 time-resolved images into 4 decay associated amplitude maps. Furthermore, these maps provide a simple means to visualize the complex electronic excited-state dynamics in this system by separating distinct dynamical processes evolving on characteristic timescales into individual spatial images. This approach provides new insight into subtle aspects of ultrafast relaxation dynamics associated with excitons and charge carriers in the perovskite thin film, which have recently been found to coexist at spatially distinct locations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

The role of fission on neutron star mergers and its impact on the r-process peaks

The comparison between observational abundance features and those obtained from nucleosynthesis predictions of stellar evolution and/or explosion simulations can scrutinize two aspects: (a) the conditions in the astrophysical production site and (b) the quality of the nuclear physics input utilized. Here we test the abundance features of r-process nucleosynthesis calculations using four different fission fragment distribution models. Furthermore, we explore the origin of a shift in the third r-process peak position in comparison with the solar r-process abundances which has been noticed in a number of merger nucleosynthesis predictions. We show that this shift occurs during the r-process freeze-out when neutron captures and β-decays compete and an (n,γ)-(γ,n) equilibrium is not maintained anymore. During this phase neutrons originate mainly from fission of material above A = 240. We also investigate the role of β-decay half-lives from recent theoretical advances, which lead either to a smaller amount of fissioning nuclei during freeze-out or a faster (and thus earlier) release of fission neutrons, which can (partially) prevent this shift and has an impact on the second and rare-earth peak as well.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Measurement of two-photon decay width of χ c2 (1 P ) in γγ → χ c2 (1 P ) → J/ψγ at Belle

We report the measurement of the two-photon decay width of χ c2 (1P) in two-photon processes at the Belle experiment. We analyze the process γγ → χ c2 (1P) → J/ψγ, J/ψ → ℓ + ℓ - (ℓ = e or μ) using a data sample of 971 fb -1 collected with the Belle detector at the KEKB e + e - collider. In this analysis, the product of the two-photon decay width of χ c2 (1P) and the branching fraction is determined to be ${\Gamma}_{\gamma \gamma}({\chi}_{c2}(1P))\mathcal{B}({\chi}_{c2}(1P)\to J/\psi \gamma) \mathcal{B} (J/\psi \to {\ell}^{+}{\ell}^{-})=$ 14.8 ± 0.3(stat.) ± 0.7(syst.) eV, which corresponds to Γ γγ (χ c2 (1P)) = 653 ± 13(stat.) ± 31(syst.) ± 17(B.R.) eV, where the third uncertainty is from $\mathcal{B}$ (χ c2 (1P) → J/ψγ) and $\mathcal{B}$ (J/ψ → ℓ + ℓ - ).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the top quark-antiquark pair charge asymmetry in events with highly boosted top quarks in proton-proton collisions at 13 TeV with the CMS detector

The top quark is the heaviest elementary particle, making it a unique tool to search for new physics. In this talk, I will present a new measurement of the top quark pair charge asymmetry for highly boosted top quarks decaying to a single lepton, missing transverse momentum and jets. The analysis is performed on 13TeV proton-proton collision data recorded by the CMS experiment during Run 2. We have defined a dedicated phase space that selects top quark-antiquark pairs with invariant mass greater than 750GeV in a semileptonic final state where the lepton is not necessarily isolated. This highly boosted sample is enhanced in valence quark production and thus expected to be more sensitive to deviations in the charge asymmetry caused by BSM processes. Dedicated tagging techniques are used to identify the decay products of hadronic top quarks and W bosons. An unfolding procedure is used to correct for detector resolution and acceptance, and inefficiencies in the event reconstruction. The result is presented in the full phase space at parton level and can be used as input to global EFT interpretations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Search for a light charged Higgs boson in the H$^\pm$ $\to $ cs channel in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A search is conducted for a low-mass charged Higgs boson produced in a top quark decay and subsequently decaying into a charm and a strange quark. The data sample was recorded in proton-proton collisions at s=13 TeV by the CMS experiment at the LHC and corresponds to an integrated luminosity of 35.9 fb-1. The search is performed in the process of top quark pair production, where one top quark decays to a bottom quark and a charged Higgs boson and the other to a bottom quark and a W boson. With the W boson decaying to a charged lepton (electron or muon) and a neutrino, the final state comprises an isolated lepton, missing transverse momentum, and at least four jets, of which two are tagged as b jets. To enhance the search sensitivity, one of the jets originating from the charged Higgs boson is required to satisfy a charm tagging selection. No significant excess beyond standard model predictions is found in the dijet invariant mass distribution. An upper limit in the range 1.68%–0.25% is set on the branching fraction of the top quark decay to the charged Higgs boson and bottom quark for a charged Higgs boson mass between 80 and 160 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗