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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Energy Spectra of Cosmic Ray Nuclei to Above 100 Gev/nucleon

The chemical composition cosmic rays as a function of energy in the range of a few GeV/nucleon to some hundreds of GeV/nucleon for boron through iron are presented. The experiment combined an ionization spectrometer and a gas Cherenkov counter, which was flown on a balloon, to perform two different and independent energy measurements. The experimental apparatus is described in detail. The energy dependence of the cosmic ray escape length for boron and iron is reported and predicted changes in the energy dependence of the ratios of primary nuclei 0/C and iron/C+0 are discussed.

Simon, M.↗
NASA NTRS1984

The cosmic-ray pathlength distribution at low energy - A new probe of the source/acceleration regions

Compiled measurements of secondary to primary ratios covering the charge range Z = 3-26 and the energy range 0.05 - 50 GeV/nucleon are analyzed in energy dependent galactic propagation plus solar modulation calculations. The cosmic ray pathlength distribution is shown to consist of two energy dependent components interpreted as representing confinement in the galaxy and confinement in the 'source' regions.

Guzik, T. G.↗
NASA NTRS1996

The effect of nonablative laser energy on joint capsular properties. An in vitro histologic and biochemical study using a rabbit model

The purpose of this study was to evaluate the effect of laser energy at nonablative levels on joint capsular histologic and biochemical properties in an in vitro rabbit model. The medial and lateral portions of the femoropatellar joint capsule from both stifles of 12 mature New Zealand White rabbits were used. Specimens were divided into three treatment groups (5 watts, 10 watts, and 15 watt) and one control group using a randomized block design. Specimens were placed in a 37 degrees bath of lactated Ringer's solution and laser energy was applied using a holmium:yttrium-aluminum-garnet laser in four transverse passes across the tissue at a velocity of 2 mm/sec with the handpiece set 1.5 mm from the synovial surface. Histologic analysis revealed thermal alteration of collagen (fusion) and fibroblasts (pyknosis) at all energy densities, with higher laser energy causing significantly greater morphologic changes over a larger area (P < 0.05). Application of laser energy did not significantly alter the biochemical parameters evaluated, including type I collagen content and nonreducible crosslinks (P > 0.05). This study demonstrated that nonablative laser energy caused significant thermal damage to the joint capsular tissue in an energy-dependent fashion, but type I collagen content and nonreducible crosslinks (P > 0.05). This study demonstrated that nonablative laser energy caused significant thermal damage to the joint capsular tissue in an energy-dependent fashion, but type I Collagen content and nonreducible corsslinks were not significantly altered.

NASA Discipline Musculoskeletal↗
NASA NTRS1988

Ionic rotational branching ratios in resonant enhanced multiphoton ionization of NO via the A2Sigma(+)(3s sigma) and D2Sigma(+)(3p sigma) states

Results are presented for the rotationally resolved photoelectron spectra resulting from a (2 + 1) one-color resonant enhanced multiphoton ionization (REMPI) of NO via the rotationally clean S21(11.5) and mixed S11(15.5) + R21(15.5) branches of the 0-0 transition in the D-X band. The calculations were done in the fixed-nuclei frozen core approximation. The resulting photoionization spectra, convoluted with a Lorentzian detection function, agree qualitatively with experimental results of Viswanathan et al. (1986) and support their conclusion that the nonspherical nature of the molecular potential creates a substantial l-mixing in the continuum, which in turn leads to the intense Delta N = 0 peak. The rather strong photoelectron energy dependence of the rotational branching ratios of the D 2Sigma(+) S21(11.5) line was investigated and compared to the weak energy dependence of the A 2Sigma(+) R22(21.5) line.

Rudolph, H.↗
DOE OSTI2025

Analysis of SPND Material Candidates for Real-Time Neutron Spectrum Monitoring Poster

The future of the nuclear industry will be shaped by advanced reactor designs requiring innovative instrumentation for safe operation. A key area of innovation is the ability to accurately and reliably monitor the neutron energy spectrum during operations, which would also enhance the experimental capabilities of existing research reactors. To address this need, our research focuses on the potential use of Self-Powered Neutron Detectors (SPNDs) for real-time neutron spectrum monitoring. We investigated various candidate materials for SPNDs by evaluating their energy-dependent reaction rates. Promising materials were further modeled using MCNP to determine the free electron production per neutron across the neutron energy spectrum, approximating their energy-dependent signal sensitivity. Our findings identified Samarium (Sm) and Gadolinium (Gd) as top candidates for thermal neutrons, Hafnium (Hf) and Thulium (Tm) for epithermal neutrons, and Tantalum (Ta) for fast neutrons. These materials will undergo future experimental validation to confirm the modeled responses and assess their feasibility for real-time neutron spectrum measurements.

46 - INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AN↗
NASA NTRS1972

K-shell photoionization cross-sections.

Approximate values for the threshold energies, threshold cross sections, and energy dependence of the cross sections for K-shell photoionization are tabulated for H, He, C, N, O, Ne, Mg, Si, and S in all stages of ionization. The approximation of these data is based on the assumptions that the threshold energy is a simple function of the nuclear charge and the number of electrons present in the atom, and that the threshold values and energy dependence of the cross sections are determined only by the threshold energy.

Daltabuit, E.↗
NASA NTRS2011

Bursty Precipitation Driven by Chorus Waves

The electron precipitation bursts have been shown to be a major sink for the radiation belt relativistic electrons. As underlying mechanism of such bursts, we propose particle scattering into the loss cone due to nonlinear resonance interaction between electrons and chorus. Stochastic heating due to the coupling leads to diffusion in pitch angle, and the rate of diffusion would be sufficient to account for the emptying of the Earth's radiation belt over the time of the main phase of geomagnetic storms. The results obtained in the present paper account for a strong energy dependence in the electron precipitation event and the correlation between the energization and loss processes on macroscopic timescales, which is primarily attributed to the cooperative effects of the coupling. This mechanism of chorus scattering should produce pitch angle distributions that are energy-dependent and butterfly-shaped. The calculated timescales and the total energy input to the atmosphere from precipitating relativistic electrons are in reasonable agreement with experimental data.

Khazanov, G. V.↗
NASA NTRS1975

Charge and energy spectra of heavy cosmic rays

Relative abundances of elements with Z values between 14 and 28 in the energy range from 870 to 1400 MeV/nucleon are reported, including Ni/Fe ? 0.050 + or - 0.004 and Co/Fe below 0.012 + or - 0.006. The Si/Fe ratio shows no major energy dependence, but the ratio of Fe-secondaries (Z values between 21 and 25) to Fe shows some variation, approximately consistent with the energy dependence of the fragmentation cross-sections.

Benegas, J. C.↗
DOE OSTI2020

Guided Ion Beam and Quantum Chemical Investigation of the Thermochemistry of Thorium Dioxide Cations: Thermodynamic Evidence for Participation of f Orbitals in Bonding

Kinetic energy dependent reactions of ThO + with O 2 are studied using a guided ion beam tandem mass spectrometer. The formation of ThO 2 + in the reaction of ThO + with O 2 is observed to be slightly endothermic and also exhibits two obvious features in the cross section. These kinetic energy dependent cross sections were modeled to determine a 0 K bond dissociation energy of D 0 (OTh + - O) = 4.94 ± 0.06 eV. This value is slightly larger but within experimental uncertainty of less precise previously reported experimental values. The higher energy feature in the ThO 2 + cross section was also analyzed and suggests formation of an excited state of the product ion lying 3.1 ± 0.2 eV above the ground state. Additionally, the thermochemistry of ThO 2 + was explored by quantum chemical calculations, including a full Feller-Peterson-Dixon (FPD) composite approach with correlation contributions up to CCSDT(Q) and four-component spin-orbit corrections, as well as more approximate CCSD(T) calculations including semiempirical estimates of spin-orbit energy contributions. The FPD approach predicts D 0 (OTh + -O) = 4.87 ± 0.04 eV, in good agreement with the experimental value. Analogous FPD results for ThO+, ThO, and ThO 2 are also presented, including ionization energies for both ThO and ThO 2 . The ThO 2 + bond energy is larger than those of its transition metal congeners, TiO 2 + and ZrO 2 + , which can be attributed partially to an actinide contraction, but also to contributions from the participation of f orbitals on thorium that are unavailable to the transition metal systems.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Reversible electron spirals by chirped attopulses at zero time delay

A class of linear, spiral phenomena is discovered in the photoelectron momentum distribution when studying photoionization of S -state atoms by a pair of linearly chirped, oppositely circularly polarized attosecond pulses eventually delayed in time by $\tau$. This controllable effect, dubbed. reversible electron spirals because of its energy-dependent sense of rotation, is identified and can be isolated in the absence of time delay for the case of opposite chirp rates. Further, the astrophysical concept of spiral arm pitch angle is borrowed to gain a better insight into the energy dependence of the reversible spiral rotation, to determine the attochirp as well as the binding energy characteristic of an atomic target. Our results indicate potential applications in attochirpmetry and polarimetry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Generalized boost transformations in finite volumes and application to Hamiltonian methods

The investigation of hadron interactions within lattice QCD has been facilitated by the well-known quantisation condition, linking scattering phase shifts to finite-volume energies. Additionally, the ability to utilise systems at finite total boosts has been pivotal in smoothly charting the energy-dependent behaviour of these phase shifts. The existing implementations of the quantization condition at finite boosts rely on momentum transformations between rest and moving frames, defined directly in terms of the energy eigenvalues. This energy dependence is unsuitable in the formulation of a Hamiltonian. In this work, we introduce a novel approach to generalise the three-momentum boost prescription, enabling the incorporation of energy-independent finite-volume Hamiltonians within moving frames. We demonstrate the application of our method through numerical comparisons, employing a phenomenological ππ scattering example.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1986

An assessment of transport coefficient approximations used in galactic heavy ion shielding calculations

An energy-dependent, perturbation expansion solution for heavy ion transport in one dimension is used to perform depth-dose calculations for 670/MeV nucleon Ne-20 beams incident upon a thick water target. Comparisons of predictions obtained by using typical energy-independent approximations and those obtained with fully energy-dependent input parameters are made. It is found that the calculated doses are underestimated when the energy-independent input approximations are used. The major source of error, however, is the lack of charge and mass conservation in the Silberberg-Tsao fragmentation parameters.

Townsend, Lawrence W.↗
DOE OSTI2021

Calibration of a versatile multi-energy soft x-ray diagnostic for WEST long pulse plasmas

A compact multi-energy soft x-ray diagnostic is being installed on the W Environment in Steady-state Tokamak (WEST), which was designed and built to test ITER-like tungsten plasma facing components in a long pulse (~1000 s) scenario. The diagnostic consists of a pinhole camera fielded with the PILATUS3 photon-counting Si-based detector (≲100 kpixel). The detector has sensitivity in the range 1.6–30 keV and enables energy discrimination, providing a higher energy resolution than conventional systems with metal foils and diodes with adequate space and time resolution (≲1 cm and 2 ms). The lower-absorption cut-off energy is set independently on each one of the ~100 kpixels, providing a unique opportunity to measure simultaneously the plasma emissivity in multiple energy ranges and deduce a variety of plasma parameters (e.g., T e , n Z , and ΔZ eff ). The energy dependence of each pixel is calibrated here over the range 3–22 keV. The detector is exposed to a variety of monochromatic sources—fluorescence emission from metallic targets—and for each pixel, the lower energy threshold is scanned to calibrate the energy dependence. The data are fit to a responsivity curve (“S-curve”) that determines the mapping between the possible detector settings and the energy response for each pixel. Here, the calibration is performed for three energy ranges: low (2.3–6 keV), medium (4.5–13.5 keV), and high (5.4–21 keV). We determine the achievable energy resolutions for the low, medium, and high energy ranges as 330 eV, 640 eV, and 950 eV, respectively. The main limitation for the energy resolution is found to be the finite width of the S-curve.

47 OTHER INSTRUMENTATION↗
NASA NTRS2016

Heavy Ion Induced Degradation in SiC Schottky Diodes: Bias and Energy Deposition Dependence

Experimental results on ion-induced leakage current increase in 4H-SiC Schottky power diodes are presented. Monte Carlo and TCAD simulations show that degradation is due to the synergy between applied bias and ion energy deposition. This degradation is possibly related to thermal spot annealing at the metal semiconductor interface. This thermal annealing leads to an inhomogeneity of the Schottky barrier that could be responsible for the increase leakage current as a function of fluence.

modeling↗
DOE OSTI2023

Bond Energies of UO + and UC + : Guided Ion Beam and Quantum Chemical Studies of the Reactions of Uranium Cation with O 2 and CO

Here, guided ion beam tandem mass spectrometry was used to examine the kinetic energy dependent reactions of U + with O 2 and CO. In the reaction of U + with O 2 , the UO + product is formed in a barrierless and exothermic process with a reaction efficiency at low energies of k/k col =1.1±0.2, but increases at higher collision energies. Formation of both UO + and UC + in the reaction of U + with CO is endothermic. 0 K bond dissociation energies (BDEs) of D 0 (U + -O)=7.88±0.09 eV and D 0 (U + -C)=4.03±0.13 eV were determined by analyzing the kinetic energy dependent cross sections in the latter endothermic reactions. These values are within experimental uncertainty of previously reported experimental values. Additionally, the electronic states of UO + and UC + and the potential energy surfaces for the reactions were explored by quantum chemical calculations. The former include a full Feller-Peterson-Dixon composite approach with correlation contributions up to CCSDT(Q) for UO and UO + , yielding D 0 (U-O)=7.82 eV and D 0 (U + -O)=7.99 eV, as well as more approximate CCSD(T) calculations where a semi-empirical model was used to estimate spin-orbit energy contributions, which are generally found to improve the agreement with experiment. Both experimental BDEs are observed to be close to those of their transition metal congeners, ScL + , YL + , and GdL + (L=O and C).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1980

The effect of convection on the propagation of relativistic galactic electrons

The paper presents exact analytical solutions which describe steady-state transport of relativistic electrons subject to diffusion, convection, and radiation losses. The diffusion coefficient is spatially and energy dependent; the bulk convection velocity is considered to be constant and directed outward from the galactic plane. The electron spectral behavior with respect to galactic height and energy indicates that convection provides a 'break' in the steady-state energy spectrum without recourse to distribution of sources. Radio observations of NGC 891 and NGC 4631 galaxies can be used to estimate their diffusion coefficient and its energy dependence. Application of analytical solutions to our Galaxy indicates that the diffusion coefficient and outflow velocity deduced from relativistic electron measurements and radio observations of their synchrotron radiation agree with values based on the transport of the cosmic ray nucleonic component.

Lerche, I.↗
DOE OSTI2020

Experimental determination of electron attenuation lengths in complex materials by means of epitaxial film growth: advantages and challenges

Accurate electron attenuation lengths are of critical importance in using electron spectroscopic methods to quantitatively characterize complex materials. Here we show that analysis of core-level and valence-band x-ray photoelectron spectra excited with monochromatic AlK? x-rays from the substrate and measured as a function of film thickness can be used to determine electron attenuation lengths in epitaxial SrTiO3 films on Ge(001). Closely lattice-matched epitaxial heterojunctions are ideal systems for determining attenuation lengths provided the films grow in a layer-by-layer fashion, leading to atomically flat surfaces, and the buried interfaces are atomically abrupt. In principle, either the rate of attenuation of substrate peak intensities or the rate of increase of film peak intensities can be used for this purpose. However, we find that structural nonuniformities in the films reduce the accuracy of electron attenuation lengths determined from photoelectrons that originate within the films. A more reliable source of information is found in photoelectrons from the substrate which traverse the film. By using the energy dependence of calculated electron attenuation lengths from the NIST database in combination with Ge 3d core and Ge-derived valence band intensities, we determine electron attenuation length as a function of kinetic energy for SrTiO3.

Chambers, Scott A.↗
DOE OSTI2023

Measurement of $$ {e}^{+}{e}^{-}\to p{K}^{-}\overline{\Lambda}+c.c. $$ cross sections between 4.009 GeV and 4.951 GeV

Abstract Usinge + e − collision datasets corresponding to a total integrated luminosity of 21.7 fb −1 collected with the BESIII detector at the BEPCII collider at center-of-mass energies ranging from 4.009 GeV to 4.951 GeV, the energy-dependent cross sections of$$ {e}^{+}{e}^{-}\to p{K}^{-}\overline{\Lambda}+c.c. $$ e + e − → p K − Λ ¯ + c . c . are measured for the first time. By fitting these energy-dependent cross sections, we search for the excitedψstatesψ(4160) andψ(4415), and the vector charmonium-like statesψ(4230),ψ(4360), andψ(4660). No evidence for these is observed and the upper limits on the branching fractions of these states decaying into$$ p{K}^{-}\overline{\Lambda}+c.c. $$ p K − Λ ¯ + c . c . are set at the 90% confidence level.

Physics↗