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Results for “R PROCESS”

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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Shape evolution in neutron-rich nuclei near the r-process path

To assess the resources needed to field a quantitative measurement to advance our knowledge on shape evolution, we have carried out a numerical simulation of the Coulomb excitation for 112 Ru at 460 MeV bombarding energy on a 208 Pb target of 1 mg/cm 2 using a semiclassical code, GOSIA with GRETINA/CHICO2.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

{sup 13,14}B(n, γ) via Coulomb Dissociation for Nucleosynthesis towards the r-Process

Radioactive beams of {sup 14,15}B produced by fragmentation of a primary {sup 40}Ar beam were directed onto a Pb target to investigate the neutron breakup within the Coulomb field. The experiment was performed at the LAND/R{sup 3}B setup. Preliminary results for the Coulomb dissociation cross sections as well as for the astrophysically interesting inverse reactions, {sup 13,14}B(n,γ), are presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

β-decay and β-delayed Neutron Emission Measurements at GSI-FRS Beyond N=126, for r-process Nucleosynthesis

New measurements of very exotic nuclei in the neutron-rich region beyond N=126 have been performed at the GSI facility with the fragment separator (FRS). The aim of the experiment is to determine half-lives and β-delayed neutron emission branching ratios of isotopes of Hg, Tl and Pb in this region. This contribution summarizes final counting statistics for identification and for implantation, as well as the present status of the data analysis of the half-lives. In summary, isotopes of Pt, Au, Hg, Tl, Pb, Bi, Po, At, Rn and Fr were clearly identified and several of them ({sup 208-211}Hg, {sup 211-215}Tl, {sup 214-218}Pb) were implanted with enough statistics to determine their half-lives. About half of them are expected to be neutron emitters, in such cases it will become possible to obtain the neutron emission probabilities, Pn.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Determination of Solar System R-Process Abundances using ENDF/B-VIII.0 and TENDL-2015 libraries

Recent multi-messenger detection of the binary neutron star merger (GW170817) energized the astrophysical community and encouraged further research for determination of nuclear physics observables. Comprehensive studies of atomic nuclei in the cosmos provide an opportunity for investigating these astrophysical phenomena and acquiring complementary information on stellar nucleosynthesis processes that can be verified using the latest nuclear data. Evaluated Nuclear Data File (ENDF) libraries contain complete collections of reaction cross sections over the energy range relevant to astrophysics, fission yields and decay data. These data collections have been used worldwide in nuclear science, industry and national security applications. There is great interest in exploring the ENDF/B-VIII.0 and TALYS Evaluated Nuclear Data Library (TENDL-2015) for nuclear astrophysics purposes and comparing findings with the Karlsruhe Astrophysical Database of Nucleosynthesis in Stars (KADoNiS). The Maxwellian-averaged cross sections (MACS) and astrophysical reaction rates have been calculated using the ENDF/B-VIII.0 and TENDL-2015 evaluated data sets. The calculated cross sections were combined with the solar system abundances and fitted using the classical model of stellar nucleosynthesis. Astrophysical rapid- and slow-neutron capture, r- and s-process, respectively, abundances were obtained from present data and compared with available values. Further analysis of MACS reveals potential evaluated libraries data deficiencies and a strong need for new measurements. The current results demonstrate a large nuclear astrophysics potential of evaluated libraries and mutually beneficial relations between nuclear industry and research e orts.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

Materials Processing R&D with a Free Electron Laser

A unique light source to explore and develop laser-based processes may be based on a free electron laser driven by an energy-recovering linac. It can address much of the vast "white space" between the output wavelengths of conventional fixed-frequency lasers. The greatest success of conventional lasers is in delivering great energy intensity for ever-shorter pulse duration with increasing average power. They serve as sources of spatio-temporally dense electronic excitation, which can be converted to heat, especially in metals. In contrast, the inherent tunability of the FEL provides opportunity for channeling energy into specific vibrational pathways in a material to achieve desired effects. Organic materials offer a significant example, attracting as they do growing attention for next-generation photonics and electronics, with some applications already commercialized. Present fabrication techniques based on solvents or evaporation set limits on materials selection. Tuning the FEL to an IR absorption band, on the other hand, offers a path to molecule-selective energy deposition, enabling pulsed laser deposition, processing, and analysis of otherwise intractable materials. The UV FEL now coming into operation at JLab will offer further opportunities, as it will be able to drive electronic transition directly as well as the vibrational transitions accessible with the IR FEL. Authored by Jefferson Science Associates LLC under U.S.DOE Contract No. DE-AC05-06OR23177

Kelley, Michael↗
NASA NTRS1978

An interpretation of special and general isotopic anomalies in r-process nuclei

My analysis of new discoveries by McCulloch and Wasserburg of Ba and Nd isotopic anomalies in inclusions of the Allende meteorite argues that (1) these anomalies contain special extinct radioactivities resulting from radioactive decay within grains formed in and ejected from the supernova interior, (2) the inclusions studied are fused assemblies of interstellar grains that were never totally vaporized, and (3) theoretical separation into r and s abundances suggests that fluctuations between r and s components has occurred during the accumulation processes. These points lend support to a new chemical picture of the early solar system that I have developed, although many interpretations remain possible. Measurements of the neutron-capture cross sections of Nd isotopes are urgently needed to experimentally validate these conclusions.

Clayton, D. D.↗
DOE OSTI2018

Update on Plasma Processing R&D for LCLS-II

SRF cavities performance preservation is crucial, from vertical test to accelerator operation. Field emission is still one of the main problems to overcome and plasma cleaning has been proven successful by SNS, in cleaning field emitters and increasing the work function of Nb. A collaboration has been established between FNAL, SLAC and ORNL with the purpose of applying plasma processing to LCLS-II cavities, in order to minimize and overcome field emission without affecting the high Q of N-doped cavities. The recipe will follow the neon-oxygen active plasma adopted at SNS, allowing in-situ processing of cavities and cryomodules from hydrocarbon contaminants. A novel method for plasma ignition has been developed at FNAL: a plasma glow discharge is ignited using high order modes to overcome limitations imposed by the fundamental power coupler. The results of experiments on 9-cell LCLS-II cavity are presented, along with plasma ignition studies. In addition the RF system is shown and N-doped Nb samples studies are discussed.

43 PARTICLE ACCELERATORS↗