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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
DOE OSTI2013

Nuclear Data Sheets for A=31

Nuclear spectroscopic information for the known nuclides of mass 31 (F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar) has been evaluated. A useful source of many of the Adopted Levels for {sup 31}P and {sup 31}S is presented in Endt's evaluations (1998En04,1990En08,1978En02,1973EnVA), however all the adopted properties of levels and gamma rays have been re-evaluated in this work. The data sets for reactions and decays, including all available gamma–ray data, are based mostly on the original literature. The 31Mg nuclide is a prime candidate for the study of ‘island-of-inversion’ as its ground state and first excited state can only be explained by intruder orbitals in a deformed shell-model approach. {sup 31}S is of importance in astrophysics rp-process as a possible ‘bottleneck’ nuclide. There are no data available for excited states in {sup 31}F, {sup 31}Ne and {sup 31}Ar. No gamma transitions are known in {sup 31}Cl. For {sup 31}Na, only one excited state is known. The radioactive decay characteristics of {sup 31}F and {sup 31}Ne isotopes have not yet been investigated. The {sup 31}S and {sup 31}Mg nuclei are currently being pursued intensively by various experimental groups, including recent work by Nuclear Astrophysics group at McMaster, the results of which will soon become available.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2020

Corrosion Behavior of Stainless Steel 304 and Nickel 625 Under Iodine Vapor at 300 °C

The chemical, structural, and microstructural behavior of stainless steel 304 (SS 304) and nickel 625 (Ni 625) were probed after exposure to iodine vapor laminar flow at 300 °C. This work was conducted in support of the development of in-space propulsion utilizing iodine as a propellant. The kinetics of corrosion was measured in a custom-built iodine-compatible thermogravimetric analyzer rig at 300 °C in which samples were exposed to an iodine laminar vapor flow of 1 mg/min (carried by 20 mL/min argon gas) for up to 31 days. Samples were characterized after the experiment by X-ray diffraction, electron microscopy, energy dispersive X-ray spectroscopy, and dynamic secondary ion mass spectrometry. All samples formed scales consisting mainly of metal oxyiodides showing different chemistry, microstructure, and crystalline phases. The paralinear rate law best describes the kinetics of oxidation of the samples. SS 304 exhibited slightly slower kinetics of oxidation (106±3·10(exp –5) mg/sq.cm/day) than Ni 625 (122±3·10(exp –5) mg/sq.cm/day) in the low-oxygen and low-water environment.

Chemistry and Materials↗
NASA NTRS1976

A hybrid computer program for rapidly solving flowing or static chemical kinetic problems involving many chemical species

A hybrid chemical kinetic computer program was assembled which provides a rapid solution to problems involving flowing or static, chemically reacting, gas mixtures. The computer program uses existing subroutines for problem setup, initialization, and preliminary calculations and incorporates a stiff ordinary differential equation solution technique. A number of check cases were recomputed with the hybrid program and the results were almost identical to those previously obtained. The computational time saving was demonstrated with a propane-oxygen-argon shock tube combustion problem involving 31 chemical species and 64 reactions. Information is presented to enable potential users to prepare an input data deck for the calculation of a problem.

Mclain, A. G.↗
DOE OSTI2015

Mass Measurements Demonstrate a Strong N = 28 Shell Gap in Argon

We present results from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. We report the first mass measurements of 48Ar and 49Ar and find atomic mass excesses of -22.28(31) MeV and -17.8(1.1) MeV, respectively. These masses provide strong evidence for the closed shell nature of neutron number N = 28 in argon, which is therefore the lowest even-Z element exhibiting the N = 28 closed shell. The resulting trend in binding-energy differences, which probes the strength of the N = 28 shell, compares favorably with shell-model calculations in the sd-pf shell using SDPF-U and SDPF-MU Hamiltonians.

Meisel, Z.↗
DOE OSTI2024

Report on Initial Tribological Studies of Graphite in Dry Argon and Molten Salt Environment

This report documents completion of the Advanced Reactor Technologies (ART) Level 2 Milestone M2TG-24OR0501081: “Complete report on initial tribological studies within molten salt environment”, due January 31, 2024. This milestone is a carryover milestone from FY23 M2TG-23OR0501091. The report summarizes the initial studies on tribological characterization of the graphite–graphite sliding interface in a dry argon and molten FLiNaK salt environment. The experiments were conducted on a high-temperature multifunctional tribometer placed in a glovebox. This configuration enables probing the wear and friction properties at high temperatures in an inert environment. The worn surfaces were analyzed using high-resolution microscopy and white-light profilometry to determine the wear modes and wear rates. This report discusses the previous wear and friction studies on 316H stainless steel (SS) sliding against graphite in molten salt for different temperatures, sliding speeds, and salt amount. Moreover, key tribological parameters of pebble-on-pebble interaction in gas-cooled and molten salt reactors (MSRs) are analyzed and used to design an experimental test matrix for future studies. The outcomes of this project could provide key information about the tribological behavior of graphite pebbles in gas-cooled and MSRs, thereby contributing to safer operation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Line Identification of Atomic and Ionic Spectra of Holmium in the Near-UV. Part I. Spectrum of Ho i

The Fourier Transform spectra of a Holmium hollow cathode discharge lamp have been investigated in the UV spectral range from 25,000 up to 31,530 cm{sup −1} (317 to 400 nm). Two Ho spectra have been measured with neon and argon as buffer gases. Based on the intensity ratios from these two spectra, a distinction was made between atomic and ionic lines (ionic lines are discussed in an accompanying paper). Using the known Ho i energy levels, 71 lines could be classified as transitions of atomic Ho, 34 of which have not been published previously. Another 32 lines, which could not be classified, are listed in the literature and assigned as atomic Ho. An additional 370 spectral lines have been assigned to atomic Ho based on the signal-to-noise ratio in the two spectra measured under different discharge conditions, namely with buffer gases argon and neon, respectively. These 370 lines have not been previously listed in the literature.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

Sensitivity to Thermonuclear Reaction Rates in Modeling the Abundance Anomalies of NGC 2419

Abundance anomalies in globular clusters provide strong evidence for multiple stellar populations within each cluster. These populations are usually interpreted as distinct generations, with the currently observed second-generation stars having formed in part from the ejecta of massive, first-generation “polluter” stars, giving rise to the anomalous abundance patterns. The precise nature of the polluters and their enrichment mechanism are still unclear. Even so, the chemical abundances measured in second-generation stars within the globular cluster NGC 2419 provide insight into this puzzling process. Previous work used Monte Carlo nuclear reaction network calculations to constrain the temperature–density conditions that could reproduce the observed abundances, thereby placing robust limits on the origins of the polluter material. The effect of individual reaction rates on these conditions has not been studied, however. Thus, we perform an exhaustive sensitivity study on the nuclear physics input to determine which reactions have the greatest impact on these predictions. We find that the {sup 30}Si(p,γ){sup 31}P, {sup 37}Ar(p,γ){sup 38}K, {sup 38}Ar(p,γ){sup 39}K, and {sup 39}K(p,γ){sup 40}Ca reactions are all critical in determining the temperature–density conditions, and ultimately, the origins of the polluter material. We conclude with recommendations for future experiments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Generation of an isolated sub-40-as pulse using two-color laser pulses: Combined chirp effects

In this paper, we theoretically discuss the combined chirp effects on the isolated attosecond generation when a model Ar is exposed to an intense 5-fs, 800-nm fundamental chirped pulse combined with a weak 10-fs, 1200-nm controlling chirped pulse. It shows that for the case of the chirp parameters {beta}{sub 1} = 6.1 (corresponding to the 800-nm field) and {beta}{sub 2} = 4.0 (corresponding to the 1200-nm field), both the harmonic cutoff energy and the supercontinuum can be remarkably extended resulting in a 663-eV bandwidth. Moreover, due to the introduction of the chirps, the short quantum path is selected to contribute to the harmonic spectrum. Finally, by superposing a properly selected harmonic spectrum in the supercontinuum region, an isolated pulse as short as 31 as (5 as) is generated without (with) phase compensation.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

High pressure shock tube ignition delay time measurements during oxy-methane combustion with high levels of CO 2 dilution

For this study, ignition delay times and methane species time-histories were measured for methane/O 2 mixtures in a high CO 2 diluted environment using shock tube and laser absorption spectroscopy. The experiments were performed between 1300 K and 2000 K at pressures between 6 and 31 atm. The test mixtures were at an equivalence ratio of 1 with CH 4 mole fractions ranging from 3.5% -5% and up to 85% CO 2 with a bath of argon gas as necessary. The ignition delay times and methane time histories were measured using pressure, emission, and laser diagnostics. Predictive ability of two literature kinetic mechanisms (GRI 3.0 and ARAMCO Mech 1.3) was tested against current data. In general, both mechanisms performed reasonably well against measured ignition delay time data. The methane time-histories showed good agreement with the mechanisms for most of the conditions measured. A correlation for ignition delay time was created taking into the different parameters showing that the ignition activation energy for the fuel to be 49.64 kcal/mol. Through a sensitivity analysis, CO 2 is shown to slow the overall reaction rate and increase the ignition delay time. To the best of our knowledge, we present the first shock tube data during ignition of methane/CO 2 /O 2 under these conditions. In conclusion, current data provides crucial validation data needed for development of future kinetic mechanisms.

42 ENGINEERING↗
DOE OSTI2023

Probing mass orderings in presence of a very light sterile neutrino in a liquid argon detector

Results from experiments like LSND and MiniBooNE hint towards the possible presence of an extra eV scale sterile neutrino. The addition of such a neutrino will significantly impact the standard three flavor neutrino oscillations. In particular, it can give rise to additional degeneracies due to additional sterile parameters. For an eV scale sterile neutrino, the cosmological constraints dictate that the sterile state is heavier than the three active states. However, for lower masses of sterile neutrinos, the sterile state can be lighter than one and/or more of the three states. In such cases, the mass ordering of the sterile neutrinos also becomes unknown, along with the mass ordering of the active states. In this paper, we explore the mass ordering sensitivity in the presence of a sterile neutrino assuming the mass squared difference |Δ 41 | to be in the range 10 –4 –1 eV 2 . We study (i) how the ordering of the active states, i.e. the determination of the sign of Δ 31 gets affected by the presence of a sterile neutrino in the above mass range, (ii) the possible determination of the sign of Δ 41 for Δ 41 in the range 10 –4 –0.1 eV 2 . This analysis is done in the context of a liquid argon detector using beam neutrinos traveling a distance of 1300 km and atmospheric neutrinos that propagate through a distance ranging from 10 – 10000 km, allowing resonant matter effects. Apart from presenting separate results from these sources, we also do a combined study and probe the synergy between these two in giving an enhanced sensitivity.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Ground state rotational and kinetic temperatures of C 2 molecules in a laser-produced plasma

This study presents an experimental comparison between rotational and kinetic temperatures of molecular species in a laser-produced plasma, utilizing tunable laser absorption spectroscopy. We analyzed high-resolution and time-resolved absorption spectra of 31 rotational transitions within the Phillips A 1 II u –X 1 Σ g 3-0 band of the C 2 molecule, measured from a laser-produced graphite plasma in ~2 Torr argon, within the 771–781 nm spectral range. Spectral fitting provided quantitative state column densities of C 2 rotational energy levels in the ground electronic and vibrational states. Boltzmann analysis revealed thermalized rotational distributions showing rotational temperatures decreasing from 3000 to 600 K within 5–500 μs following the onset of the laser plasma. The measured kinetic and rotational temperatures of C 2 molecules are comparable, suggesting that collisional processes in the laser-produced plasma are sufficient to maintain thermal equilibrium between the C 2 molecules and the Ar background gas.

Absorption spectroscopy↗
DOE OSTI2024

The NuMI Flux Prediction at ICARUS

The Deep Underground Neutrino Experiment (DUNE) is a next-generation long-baseline neutrino oscillation experiment seeking to probe fundamental symmetries within the structure of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix, and perform precision measurements its parameters including the neutrino mass ordering via the sign of $\Delta m^2_{31}$, and the charge-parity violating phase, $\delta_{CP}$. To make these measurements with high precision, DUNE will require external $\nu$-Ar scattering cross section data as a crucial input to the oscillation fit. Imaging Cosmic And Rare Underground Signals (ICARUS) is a 476 t liquid argon neutrino detector located at Fermi National Accelerator Laboratory (FNAL) where it is serving as the far detector for the Short-Baseline Neutrino (SBN) program along the Booster Neutrino Beam (BNB) axis. ICARUS additionally lies 795 m downstream and 100.1 mrad off-axis of the Neutrinos at the Main Injector (NuMI) neutrino beam. From this position, ICARUS is exposed to a large flux of NuMI (anti-)electron and (anti-)muon neutrinos, and poses a unique opportunity to provide high-statistics measurements of quasi-elastic and single pion-production cross sections for four neutrino flavors ($\nu_{\mu}$, $\nu_{e}$, $\bar{\nu}_{\mu}$, $\bar{\nu}_{e}$). This dissertation is centered around accurately characterizing the models and estimating their precision for use in making these measurements. This includes identifying major sources of uncertainty in the models such that they can be properly propagated to the cross section measurements. Specifically, this work focused on the model of the NuMI beamline and its impact on the neutrino fluxes, but also delved into the detector response model and its impact on reconstructed observables in the detector. Significant efforts were made to improve the characterization to enhance precision and thus reduce the level of propagated uncertainty. In particular, the NuMI flux was determined to be composed of 57% $\nu_{\mu}$, 38% $\bar{\nu}_{\mu}$, 3% $\nu_{e}$, and 2% $\bar{\nu}_{e}$ while the horns are operating in the positive-particle focusing configuration. The total uncertainty on the $\nu_{\mu} + \bar{\nu}_{\mu}$ ($\nu_{e} + \bar{\nu}_{e}$) flux while operating in the forward horn operating mode was determined to be 10.84% (9.04%). Compared to the on-axis flux, mesons that eventually decay to neutrinos more frequently reinteract within the NuMI structure, resulting in elevated uncertainty as these processes are not well-constrained by existing hadron interaction cross section measurements. Covariance matrices were calculated to propagate the flux uncertainty characterization to NuMI analyses.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗