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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Production of Energetic Light Fragments in the Cascade Exciton Model (CEM)

Emission of light fragments (LF) from nuclear reactions is an open question because different reaction mechanisms contribute to their production, and the relative roles of each, and how they change with incident energy, mass number of the target, and the type and emission energy of the fragments is not completely understood. None of the available models are able to accurately predict emission of LF from arbitrary reactions. However, the ability to describe production of LF (especially at energies ≳ 30 MeV) from many reactions is important for different applications, such as cosmic-ray-induced Single Event Upsets (SEUs), radiation protection, and cancer therapy with proton and heavy ion beams, to name just a few. The Cascade-Exciton Model (CEM) version 03.03 and the Los Alamos version of the Quark-Gluon String Model (LAQGSM) version 03.03 event generators in Monte Carlo N-Particle Transport Code version 6 (MCNP6) describe well the spectra of fragments with sizes up to 4 He across a broad range of target masses and incident energies (up to ∼ 5 GeV for CEM and up to ∼ 1 TeV/A for LAQGSM). However, they do not predict the high-energy tails of LF spectra heavier than 4 He well because most LF with energies above several tens of MeV are emitted during the precompound stage of a reaction, and the current versions of the CEM and LAQGSM event generators do not account for pre compound emission of LF larger than 4 He. The aim of our work is to extend the precompound model in them to include emission of light fragments up to 28 Mg, leading to an increase of predictive power of LF-production in MCNP6. This entails upgrading the Modified Exciton Model currently used at the preequilibrium stage in CEM and LAQGSM. It will also include investigation and possible expansion of the coalescence and Fermi break-up models used in the precompound stages of spallation reactions within CEM and LAQGSM. Extending our models to include emission of fragments heavier than 4 He at the precompound stage has already provided preliminary results that have much better agreement with experimental data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Precompound Emission of Energetic Light Fragments in Spallation Reactions [Dissertation]

Emission of light fragments (LF) from nuclear reactions is an open question. Different reaction mechanisms contribute to their production; the relative roles of each, and how they change with incident energy, mass number of the target, and the type and emission energy of the fragments is not completely understood. None of the available models are able to accurately predict emission of LF from arbitrary reactions. However, the ability to describe production of LF (especially at energies ≳ 30 MeV) from many reactions is important for different applications, such as cosmic-ray-induced Single Event Upsets (SEUs), radiation protection, and cancer therapy with proton and heavy-ion beams, to name just a few. The Cascade-Exciton Model (CEM) version 03.03 and the Los Alamos version of the Quark-Gluon String Model (LAQGSM) version 03.03 event generators in Monte Carlo N-Particle Transport Code version 6 (MCNP6) describe quite well the spectra of fragments with sizes up to 4 He across a broad range of target masses and incident energies (up to ~ 5 GeV for CEM and up to ~ 1 TeV/A for LAQGSM). However, they do not predict the high energy tails of LF spectra heavier than 4 He well. Most LF with energies above several tens of MeV are emitted during the precompound stage of a reaction. The current versions of the CEM and LAQGSM event generators do not account for precompound emission of LF larger than 4 He. The aim of our work is to extend the precompound model in them to include such processes, leading to an increase of predictive power of LF-production in MCNP6. This entails upgrading the Modified Exciton Model currently used at the preequilibrium stage in CEM and LAQGSM. It also includes expansion and examination of the coalescence and Fermi break-up models used in the precompound stages of spallation reactions within CEM and LAQGSM. Extending our models to include emission of fragments heavier than 4 He at the precompound stage has indeed provided results that have much better agreement with experimental data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

β-decay of neutron-rich Z∼60 nuclei and the origin of rare earth elements

A large fraction of the rare-earth elements observed in the solar system is produced in the astrophysical rapid neutron capture process (r-process). However, current stellar models cannot completely explain the relative abundance of these elements partially because of nuclear physics uncertainties. To address this problem, a β-decay spectroscopy experiment was performed at RI Beam Factory (RIBF) at RIKEN, aimed at studying a wide range of very neutron-rich nuclei with Z∼60 that are progenitors of the rare-earth elements with mass number A∼460. The experiment provides a test of nuclear models as well as experimental inputs for r-process calculations. This contribution presents the experimental setup and some preliminary results of the experiment.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Development of an aerosol microphysical module: Aerosol Two-dimensional bin module for foRmation and Aging Simulation (ATRAS)

Number concentrations, size distributions, and mixing states of aerosols are essential parameters for accurate estimation of aerosol direct and indirect effects. In this study, we developed an aerosol module, designated Aerosol Two-dimensional bin module for foRmation and Aging Simulation (ATRAS), that can represent these parameters explicitly by considering new particle formation (NPF), black carbon (BC) aging, and secondary organic aerosol (SOA) processes. A two-dimensional bin representation is used for particles with dry diameters from 40 nm to 10 µm to resolve both aerosol size (12 bins) and BC mixing state (10 bins) for a total of 120 bins. The particles with diameters from 1 to 40 nm are resolved using an additional 8 size bins to calculate NPF. The ATRAS module was implemented in the WRF-chem model and applied to examine the sensitivity of simulated mass, number, size distributions, and optical and radiative parameters of aerosols to NPF, BC aging and SOA processes over East Asia during the spring of 2009. BC absorption enhancement by coating materials was about 50% over East Asia during the spring, and the contribution of SOA processes to the absorption enhancement was estimated to be 10 – 20% over northern East Asia and 20 – 35% over southern East Asia. A clear north-south contrast was also found between the impacts of NPF and SOA processes on cloud condensation nuclei (CCN) concentrations: NPF increased CCN concentrations at higher supersaturations (smaller particles) over northern East Asia, whereas SOA increased CCN concentrations at lower supersaturations (larger particles) over southern East Asia. Application of ATRAS to East Asia also showed that the impact of each process on each optical and radiative parameter depended strongly on the process and the parameter in question. The module can be used in the future as a benchmark model to evaluate the accuracy of simpler aerosol models and examine interactions between NPF, BC aging, and SOA processes under different meteorological conditions and emissions.

Matsui, H.↗
DOE OSTI2018

Mass Spectrometry of the Xylitol Molecule

We describe a method and presents results of a mass-spectrometric investigation of the yield of positive ions formed as a result of the direct and dissociative ionization of xylitol molecules by electron impact. The mass spectra of xylitol in a range of ion mass numbers within 1–170 Da and electron impact energies 5–80 eV were measured at various temperatures. The ionization energy of xylitol and the appearance energies of related fragment ions were determined for the first time from energy dependences of the effective electron-impact ionization cross sections. The dynamics of formation of the molecular-fragment ions of xylitol by electron impact was studied in the interval of sample evaporation temperatures within 340–400 K.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2025

Discovery of new isotopes in the fragmentation of 82 Se and insights into their production

The production cross sections of neutron-rich nuclei for elements just above 60 Ca were measured at the Facility for Rare Isotope Beams (FRIB). Four previously unobserved isotopes ( 63 Sc, 65,66 Ti, and 68 V) were produced, separated, and identified for the first time using the Advanced Rare Isotope Separator (ARIS). One event was found to be consistent with 61 Ca . The new isotopes were created through the interaction of an 82 Se beam with a carbon target at an energy of 228 MeV/𝑢 and a primary beam current of 1.07 p⁢µ⁢A. The event-by-event particle identification of the mass number (𝐴), atomic number (𝑍), and ionic charge state (𝑞) for the reaction products was achieved by combining measurements of energy loss, time of flight, magnetic rigidity, and total kinetic energy. This successful search for new isotopes, conducted at the beginning of FRIB's third year of operation, highlights the facility's discovery potential, which will continue to grow as the beam current increases. The production cross sections were analyzed in the context of the newly developed Δ⁢𝐵⁢𝐸 systematics that provides trends in neutron-rich regions and increased sensitivity to nuclear binding, an important nuclear structure observable. Furthermore, the new systematics addresses gaps in 𝑄 𝑔 -based methods commonly used to interpret the production cross sections of light neutron-rich elements, and provides an efficient empirical approach to describe cross-section trends across isotopic chains. Good agreement with the measured data was obtained when the Δ⁢𝐵⁢𝐸 systematics and abrasion-ablation calculations were performed using the Hartree-Fock-Bogoliubov (HFB-22) mass table.

59 ≤ A ≤ 89↗
DOE OSTI2015

NEUTRINO-DRIVEN WINDS IN THE AFTERMATH OF A NEUTRON STAR MERGER: NUCLEOSYNTHESIS AND ELECTROMAGNETIC TRANSIENTS

We present a comprehensive nucleosynthesis study of the neutrino-driven wind in the aftermath of a binary neutron star merger. Our focus is the initial remnant phase when a massive central neutron star is present. Using tracers from a recent hydrodynamical simulation, we determine total masses and integrated abundances to characterize the composition of unbound matter. We find that the nucleosynthetic yields depend sensitively on both the life time of the massive neutron star and the polar angle. Matter in excess of up to 9 × 10{sup −3} M{sub ⊙} becomes unbound until ∼200 ms. Due to electron fractions of Y{sub e} ≈ 0.2–0.4, mainly nuclei with mass numbers A < 130 are synthesized, complementing the yields from the earlier dynamic ejecta. Mixing scenarios with these two types of ejecta can explain the abundance pattern in r-process enriched metal-poor stars. Additionally, we calculate heating rates for the decay of the freshly produced radioactive isotopes. The resulting light curve peaks in the blue band after about 4 hr. Furthermore, high opacities due to heavy r-process nuclei in the dynamic ejecta lead to a second peak in the infrared after 3–4 days.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Identification of the New Isotope 244 Md

In an experiment performed at Lawrence Berkeley National Laboratory’s 88-inch cyclotron, the isotope Md 244 was produced in the Bi 209 ( Ar 40 , 5 n ) reaction. Decay properties of Md 244 were measured at the focal plane of the Berkeley Gas-filled Separator, and the mass number assignment of A = 244 was confirmed with the apparatus for the identification of nuclide A . The isotope Md 244 is reported to have one, possibly two, α -decaying states with α energies of 8.66(2) and 8.31(2) MeV and half-lives of 0.4 – 0.1 + 0.4 and ~ 6 s , respectively. Furtermore, first evidence of the α decay of Bk 236 was observed and is reported.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Nuclear Data Sheets for A=245

Available information pertaining to the nuclear structure of ground and excited states for all known nuclei with mass numbers A=245 have been compiled and evaluated. In this work, the adopted level and decay schemes, as well as the detailed nuclear properties and configuration assignments based on experimental data, are presented for these nuclides. When there are insufficient data, expected values from systematics of nuclear properties and/or theoretical calculations are utilized. Unexpected or discrepant experimental results are also noted. Since the last evaluation, new rotational bands in 245 Pu have been observed to high spin from transfer reaction 244 Pu( 209 Bi, 208 Biγ) by 2014Ho16. While in 245 Am, the 249 Bk α decay measurements by 2013Ah03 added a new rotational band based on π3/2[521] configuration. The 245 Pu β - decay scheme is basically what was proposed in the late 60's and 47 γ rays have still not been placed. In 245 Cm, precise alpha energies and intensities were measured by 2015Ah03 in 249Cf α decay. Their reported alpha energies of the main α group were about 2 keV lower than in the previous evaluation. The spin and parity of the g.s. of 245 Es is still ambiguous as more detailed information on the decay is needed. With the production of 249 No via fusion evaporation reaction by groups in Dubna and GSI, it's alpha decay was studied and some properties of the daughter 245 Fm were published and included in this evalaution. Information on the other nuclides is scarce and not much has been investigated since the last evaluation. A summary and compilation of the discovery of the various nuclides in this mass region is given in: 2013Fr02 ( 245 Pu, 245 Am, 245 Cm, 245 Bk, 245 Cf), 2011Me01 ( 245 Es), and 2013Th02 ( 245 Md, 245 Fm).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Precision Mass Measurements Reveal Low Neutron Pairing in Tin beyond 𝑁=82 and Its Impact on Stellar Nucleosynthesis

We present a study on neutron-rich tin (𝑍 =50) isotopes beyond the doubly closed shell of 𝑁 = 82 through high-precision mass measurements, including the first-ever measurements of the masses of 136 Sn, 137 Sn, and 138 Sn isotopes. These measurements enhance our understanding of the nuclear structure and astrophysical nucleosynthesis in this previously unexplored region. The new mass data are used for evaluation of the final abundances of mass numbers 𝐴 =135 and 137 in 𝑟-process network calculations. Our findings reveal a notable change in the empirical pairing gap for tin isotopes beyond the 𝑁 = 82 closed shell and a shift in the two-neutron-separation energy slope compared to heavier elements above the shell closure. A new set of ab initio calculations effectively describes these observed trends.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Electroproduction of K+ Λ at JLab Hall-C

A Λ hypernuclear spectroscopic experiment, JLab E05-115 was performed at JLab Hall-C in 2009 by the (e, e' K + ) reaction. Data of Λ hypernuclei with mass numbers from A = 7 to A = 52 were successfully taken, and the analyses are in progress. A polyethylene (CH 2 ) target was used as a proton target to calibrate energy scales, and to study elementary process of the p(e, e' K + )Λ, Σ 0 reaction. We report a preliminary differential cross section of K + Λ electro-production at low Q 2 [~0.01 (GeV/c) 2 ] and at small kaon angles (cosΘ$CM\atop{K}$ ~0.97) in the present article.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Review on characterization of nano-particle emissions and PM morphology from internal combustion engines: Part 2 [Review on morphology and nanostructure characterization of nano-particle emission from internal combustion engines]

This study presents a review of the characterization of physical properties, morphology, and nanostructure of particulate emissions from internal combustion engines. Because of their convenience and readiness of measurement, various on-line commercial instruments have been used to measure the mass, number, and size distribution of nano-particles from different engines. However, these on-line commercial instruments have inherent limitations in detailed analysis of chemical and physical properties, morphology, and nanostructure of engine soot agglomerates, information that is necessary to understand the soot formation process in engine combustion, soot particle behavior in after-treatment systems, and health impacts of the nano-particles. For these reasons, several measurement techniques used in the carbon research field, i.e., highresolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and Raman spectroscopy, were used for analysis of engine particulate matter (PM). This review covers a brief introduction of several measurement techniques and previous results from engine nano-particle characterization studies using those techniques.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Imaging the initial condition of heavy-ion collisions and nuclear structure across the nuclide chart

High-energy nuclear collisions encompass three key stages: the structure of the colliding nuclei, informed by low-energy nuclear physics, the initial condition , leading to the formation of quark–gluon plasma (QGP), and the hydrodynamic expansion and hadronization of the QGP, leading to final-state hadron distributions that are observed experimentally. Recent advances in both experimental and theoretical methods have ushered in a precision era of heavy-ion collisions, enabling an increasingly accurate understanding of these stages. However, most approaches involve simultaneously determining both QGP properties and initial conditions from a single collision system, creating complexity due to the coupled contributions of these stages to the final-state observables. To avoid this, we propose leveraging established knowledge of low-energy nuclear structures and hydrodynamic observables to independently constrain the QGP’s initial condition. By conducting comparative studies of collisions involving isobar-like nuclei—species with similar mass numbers but different ground-state geometries—we can disentangle the initial condition’s impacts from the QGP properties. This approach not only refines our understanding of the initial stages of the collisions but also turns high-energy nuclear experiments into a precision tool for imaging nuclear structures, offering insights that complement traditional low-energy approaches. Opportunities for carrying out such comparative experiments at the Large Hadron Collider and other facilities could significantly advance both high-energy and low-energy nuclear physics. Additionally, this approach has implications for the future electron-ion collider. While the possibilities are extensive, we focus on selected proposals that could benefit both the high-energy and low-energy nuclear physics communities. Originally prepared as input for the long-range plan of U.S. nuclear physics, this white paper reflects the status as of September 2022, with a brief update on developments since then.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Nuclear Data Sheets for A = 75

The experimental nuclear spectroscopic data for known nuclides of mass number 75 (Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Kr, Rb, Sr) have been evaluated and presented together with Adopted properties for levels and γ rays. New high-spin data are available for {sup 75}Ga, and {sup 75}Rb; and lifetime data for high-spin states in {sup 75}Br and {sup 75}Kr. For ΔJ =1, M1+E2 transitions in two rotational bands in {sup 75}Kr, several B(E2)(W.u.) values are anomalously high, deviating by 2–3 σ values from currently accepted RUL(E2) = 300. In the opinion of the evaluators, there is need to remeasure level lifetimes and multipole mixing ratios in {sup 75}Kr to resolve this serious discrepancy. New precise single-particle transfer cross section data are available for {sup 75}Ga, {sup 75}Ge, {sup 75}As and {sup 75}Se from several different reactions (2009Ka06,2008Sc03); these data give information for occupancy of valence neutron orbitals in the ground states of target nuclides: {sup 76}Ge, {sup 76}Se and {sup 78}Se. No significant new data since the 1999 NDS for A = 75 have been reported for {sup 75}As and {sup 75}Se. No data are yet available for excited states in {sup 75}Co, {sup 75}Ni and {sup 75}Sr. For {sup 75}Fe, only the isotopic identification is made with one observed event. The radioactive decay schemes of {sup 75}Co and {sup 75}Ni are unknown while those for {sup 75}Rb and {sup 75}Sr are incomplete. This work supersedes the data presented in the previous NDS evaluation of A = 75 published by 1999Fa05.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Nuclear Data Sheets for A = 129

The experimental nuclear spectroscopic data for known nuclides of mass number 129 (Ag, Cd, In, Sn, Sb, Te, I, Xe, Cs, Ba, La, Ce, Pr, Nd, Pm, Sm) have been evaluated and presented together with adopted properties for levels and γ rays. This evaluation represents a revision of the previous one 18 years ago by Y. Tendow (1996Te01). Extensive new data have become available for many nuclides in the intervening years, although, no data are available for excited states in {sup 129}Pm and {sup 129}Sm, and for {sup 129}Ag and {sup 129}Cd, only limited information is available for the g.s. and isomers. The decay schemes of {sup 129}Ag, {sup 129}Pm and {sup 129}Sm are unknown, and those for {sup 129}Cd, {sup 129}In, {sup 129}Ce, {sup 129}Pr and {sup 129}Nd are incomplete. Many γ rays and extended level schemes have been reported for the ground state and isomer decays of {sup 129}Ba to {sup 129}Cs, yet the adopted set of intensities in this evaluation originate from a brief paper in an annual laboratory report. There remain several unplaced gamma rays, coupled with ambiguity about division of intensities amongst the two activities of {sup 129}Ba with nearly the same half-lives. Isomerism is expected in {sup 129}Pr, but there is no confirmed identification. Low-lying level structure in {sup 129}Nd, including identification of a possible third long-lived isomer in this nuclide, remains uncertain. The spin-parity assignments of (5/2+) for the ground state and (7/2−) for an isomer at 107.6 keV in {sup 129}Ce are assigned based on strong support from systematics and band configurations, yet this result is in contradiction with the quadrupole interaction hyperfine structure measurement which favors 9/2− over 7/2− for the isomer, consequently 7/2+ for the ground state. Direct measurements of spins of ground state and isomer of {sup 129}Ce are needed to settle this issue. Confirmed spins and parities of the ground state and isomer of {sup 129}La are also lacking. Assignments in this work are mainly based on systematics of h{sub 11/2} decoupled structures. A direct measurement of ground state spin of {sup 129}La will also be desirable. Recommended data presented in this work supersede those in previous NDS evaluations of A=129 nuclides published by 1996Te01, 1983Ha46 and 1972Ho55.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Nuclear Data Sheets for A = 248

Detailed level schemes, decay schemes, and the experimental data on which they are based are presented for all nuclei with mass number A=248. The experimental reaction and decay data are evaluated; inconsistencies and discrepancies are noted; and adopted values are given for various level properties (including spin and parity, halflife, and configuration), γ properties (including energy, intensity, and multipole character) and α properties (including energy, intensity, and hindrance factor). This evaluation replaces the A=248 evaluation published by A. Akovali in Nuclear Data Sheets 87, 249 (1999)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗