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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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

High energy X-ray diffraction measurement of residual stresses in a monolithic aluminum clad uranium–10 wt% molybdenum fuel plate assembly

Residual stresses are expected in monolithic, aluminum clad uranium 10 wt% molybdenum (U–10Mo) nuclear fuel plates because of the large mismatch in thermal expansion between the two bonded materials. The full residual stress tensor of the U–10Mo foil in a fuel plate assembly was mapped with 0.1 mm resolution using high-energy (86 keV) X-ray diffraction. The in-plane stresses in the U–10Mo foil are strongly compressive, roughly -250 MPa in the longitudinal direction and -140 MPa in the transverse direction near the center of the fuel foil. The normal component of the stress is weakly compressive near the center of the foil and tensile near the corner. The disparity in the residual stress between the two in-plane directions far from the edges and the tensile normal stress suggest that plastic deformation in the aluminum cladding during fabrication by hot isostatic pressing also contributes to the residual stress field. A tensile in-plane residual stress is presumed to be present in the aluminum cladding to balance the large in-plane compressive stresses in the U–10Mo fuel foil, but cannot be directly measured with the current technique due to large grain size.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2025

Energy resolution and gain measurements in Argon-based gas mixtures: Exploring Ar:CF 4 for low energy measurements with TPCs

Time Projection Chambers (TPCs) are among the most advanced charged-particle detectors. Gas-filled TPCs have tracking capabilities that provide 3D-imaging of charged particles with a good energy resolution for spectroscopy. Different gas mixtures have different properties that determine the energy resolution as well as the spatial resolution. Therefore, optimization of operating conditions is required to simultaneously obtain adequate gain, energy resolution, spatial/track resolution, as well as higher drift velocities for high counting rates applications. Ar:CF 4 gas mixture has higher electron drift velocities and lower electron diffusion, which makes it an attractive candidate for TPC filling gas for low energy nuclear physics applications as compared to commonly used Ar:CH 4 and Ar:CO 2 gas mixtures, namely when tracking information is needed. However, other properties, including energy resolution and gain, remain largely unexplored in Ar:CF 4 especially at pressures and other operating conditions relevant for low-energy nuclear physics applications. Here, in this paper we report on gain and energy resolution measurements, using Gas Electron Multipliers (GEMs), in the less explored Ar:CF 4 mixture (Alfonsi et al., 2006), as well as in the more commonly used gas mixtures Ar:CH 4 and Ar:CO 2 . In addition to obtaining energy resolution and gain, we provide results from Garfield++ simulations for gain fluctuations, and their impact on energy resolution is discussed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

The feasibility of isobaric suppression of 26 Mg via post-accelerator foil stripping for the measurement of 26 Al [The feasibility of isobaric suppression of 26Mg via post-accelerator foil stripping for the measurement of 26Al.]

Most accelerator mass spectrometry measurements of 26 Al utilize the Al- ion despite lower source currents compared with AlO- since the stable isobar 26 Mg does not form elemental negative ions. A gas-filled magnet allows sufficient suppression of 26 Mg thus enabling the use of the more intense 26 AlO- ion. However, most AMS systems do not include a gas-filled magnet. We therefore explored the feasibility of suppressing 26 Mg by using a post-accelerator stripping foil. With this approach, combined with the use of alternative cathode matrices, we were able to suppress 26 Mg by a factor of twenty. This suppression was insufficient to enable the use of 26 AlO-, however further refinement of our system may permit its use in the future.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2019

Directed flow of quarks from the RHIC Beam Energy Scan measured by STAR

Directed flow (ν 1 ) is a good probe of the early-stage dynamics of collision systems, and the ν 1 slope at midrapidity ( dv 1 /dy| y=0 ) is sensitive to the system's equation of state. STAR has published ν 1 (y) measurements for ten particle species (π ± ,$p, \bar{p},Λ,\bar{Λ},ϕ,K^± and K_S^0$) in Au+Au collisions at eight beam energies from $ \sqrt{s_{NN}}$ = 7.7 GeV to 200 GeV. In this study, we employ a simple coalescence idea to decompose ν 1 of hadrons into ν 1 of constituent quarks. The dv 1 /dy values of $\bar{p},\bar{K},$ and $\bar{Λ}$ are used to test the coalescence sum rule for produced quarks. Data involving produced quarks support the coalescence picture at $ \sqrt{s_{NN}}$ =11.5 GeV to 200 GeV, and a sharp deviation from this picture is observed at 7.7 GeV. The dv 1 /dy of transported quarks is studied via net particles (net p and net Λ). In these proceedings, we further extract the ν 1 slopes of produced and transported quarks, assuming that the coalescence sum rule is valid.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Measurement of key resonance states for the P 30 ( p , γ ) S 31 reaction rate, and the production of intermediate-mass elements in nova explosions

We report the first experimental constraints on spectroscopic factors and strengths of key resonances in the P-30(p, gamma)S-31 reaction critical for determining the production of intermediate-mass elements up to Ca in nova ejecta. The P-30(d,n)S-31 reaction was studied in inverse kinematics using the GRETINA gamma-ray array to measure the angle-integrated cross-sections of states above the proton threshold. In general, negative parity states are found to be most strongly produced but the absolute values of spectroscopic factors are typically an order of magnitude lower than predicted by the shell-model calculations employing WBP Hamiltonian for the negative-parity states. The results clearly indicate the dominance of a single 3/2(-) resonance state at 196 keV in the region of nova burning T approximate to 0.10-0.17 GM, well within the region of interest for nova nucleosynthesis. Hydrodynamic simulations of nova explosions have been performed to demonstrate the effect on the composition of nova ejecta.

Kankainen, A. (ORCID:0000000310827602)↗
DOE OSTI2016

Nuclear Magnetic Resonance Measurements and Electronic Structure of Pu(IV) in [(Me)4N]2PuCl6

The synthesis, electronic structure, and characterization via single crystal X-ray diffraction, nuclear magnetic resonance (NMR) spectroscopy, and magnetic susceptibility of (Me4N)2PuCl6 are reported. NMR measurements were performed to both search for the direct 239Pu resonance and to obtain local magnetic and electronic information at the Cl site through 35Cl and 37Cl spectra. No signature of 239Pu NMR was observed. The temperature dependence of the Cl spectra was simulated by diagonalizing the Zeeman and quadrupolar Hamiltonians for 35Cl, 37Cl and 14N isotopes. Electronic structure calculations predict a magnetic ?5 triplet ground state of Pu(IV) in the crystalline electric field of the undistorted PuCl6 octahedron. A tetragonal distortion would result in a very small splitting (20 cm-1) of the triplet ground state into a nonmagnetic singlet and a doublet state. The Cl shifts have an inflection point at T = 15 K, differing from the bulk susceptibility, indicating a nonmagnetic crystal field ground state. The Cl spin-lattice relaxation time is constant down to T = 15 K, below which it rapidly increases, also supporting the nonmagnetic crystal field ground state.

Mounce, Andrew M.↗
DOE OSTI2023

Measuring Relative Energies of Ligand Binding Conformations on Nanocluster Surfaces with Temperature-Dependent FTIR Spectroscopy

We present a method to measure relative energies between binding conformations of carboxylate ligands on InP magic-sized clusters in solution. Using Markov chain Monte Carlo global fitting analysis on temperature-dependent vibrational spectra of cluster-bound ligands, we observe significantly different relative energies between various bidentate and monodentate binding motifs. Relative to the monodentate motif, the chelating conformation is 0.7 ± 0.3 kcal/mol more stable and the syn–syn bridging conformation is 1.1 ± 0.5 kcal/mol more stable, but the syn–anti bridging conformation exhibits no significant difference. Our results demonstrate that the relative energy between monodentate-bound carboxylates and unbound carboxylic acids is 4.52 ± 0.05 kcal/mol, or 1582 ± 19 cm –1 , nearly identical to the carboxylate asymmetric stretching frequency. Here, we suggest that the ligand vibrational energy may play a key role in ligand dissociation by compensating for energy differences between bound and dissociated ligand states. This approach gives important experimental insights into ligand binding and can inform future nanocrystal surface engineering.

Conformation↗
DOE OSTI2017

Measuring Long-Range 13 C– 13 C Correlations on a Surface under Natural Abundance Using Dynamic Nuclear Polarization-Enhanced Solid-State Nuclear Magnetic Resonance [Measuring Long Range 13 C– 13 C Correlations on Surface under Natural Abundance Using DNP-enhanced Solid-state NMR]

Here, we report that spatial (<1 nm) proximity between different molecules in solid bulk materials and, for the first time, different moieties on the surface of a catalyst, can be established without isotope enrichment by means of homonuclear CHHC solid-state nuclear magnetic resonance experiment. This 13 C– 13 C correlation measurement, which hitherto was not possible for natural-abundance solids, was enabled by the use of dynamic nuclear polarization. Importantly, it allows the study of long-range correlations in a variety of materials with high resolution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗