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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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Excited nuclei electromagnetic de-excitation rate by inelastic scattering in stellar particles calculated as function of temperature, density, transition energy and multipole functions
Electronic excitation energy transfer as function of distance measured, noting energy transfer process use as spectroscopic ruler
An ionization spectrometer consisting of 12 layers of tungsten each 6.13 gm cm/2 thick and 7 iron modules each 70 gm cm/2 thick was flown in a balloon at an altitude of 6 gm cm/2 for 16 hours. The distributions of the first interaction points are used to determine the mean free path of the incident particles. At energies of 20 GeV the proton m.f.p. of 140 gm cm/2 is in agreement with that of other workers. The m.f.p.'s of heavy nuclei have been determined as a function of energy up to a total energy of 1000 GeV. These results are compared with the overlap model of nucleus-nucleus collisions. For C nuclei interacting with W the overlap parameter is -2.6 x 10/13 cm. The energy dependence of this parameter is discussed.
The transport of electrons through material is discussed with emphasis on space radiation problems. Brief reviews of the electron radiation environment and electron transport properties are presented. Parametric representations of the electron transmitted fraction, energy spectrum, angular distribution, backscatter coefficient, and energy deposition are given as functions of electron energy and target material. Parametric equations for thick target bremsstrahlung are presented. Calculations of the transport of isotropically incident electrons relevant to space applications are shown. Comparisons of parametric representation with data, photon attenuation coefficients, electron energy deposition data, flux-to-dose conversion relations, and formalism applicable to space shielding problems are presented.
An Integrated Power and Attitude Control System (IPACS) concept with potential application to a broad class of space missions is discussed. A description is given of the basic concept of combining the onboard energy storage and attitude control functions by storing energy in spinning flywheels which are used to provide control torques. A shuttle-launched Research and Applications Module (RAM) A303B solar-observatory mission having stringent pointing requirements (1.0 arc second) is selected to investigate possible interactions between energy storage and attitude control. A simulation of this spacecraft involving actual laboratory-model control-system hardware is presented. Simulation results are discussed which indicate that the IPACS concept, even in a failure-mode configuration, can readily meet the RAM A303B pointing requirements.
The energy spectra and charge ratios of Li, Be, B, C, N, and O nuclei in the energy range 200 MeV/nuc to 3 GeV/nuc are examined with measurements obtained during a 50 hour balloon flight in 1977 from a telescope containing several scintillation and Cerenkov counters. The ratios Li/C, Be/C, and B/C are compared with predictions based on the leaky box interstellar propagation model showing that the ratios steadily increase in the apparent interstellar matter path length down to energies of about 400 to 600 MeV/nuc, where it is between 6.5 and 7.5 g/square cm. The effects of solar modulation upon the ratios are considered for energies less than about 1 GeV/nuc as well as for a modulation parameters of phi not less than 400 MV. By examining the ratios Li/Be, Li/B, and Be/B as a function of energy, it is shown that the Li/Be ratio is most sensitive to the solar modulation effects, and that the observed changes in this ratio with energy can be explained by a relatively large modulation consistent with a phi equal to 400 MV in 1977.
Reasonable boundary conditions and test functions for photospheric line-tying are discussed, and their effects on the ideal MHD stability of coronal loops are considered. It is concluded that the plasma at the footpoints of a loop may safely be assumed to be stationary. When a simple perturbed test function is used for the energy principle, the function should be helical in form. Constraints on the test function should be discarded because they overestimate stability.
Extragalactic number counts and diffuse backgrounds at 25, 60, and 100 microns are predicted using new luminosity functions and improved spectral-energy distribution density functions derived from IRAS observations of nearby galaxies. Galaxies at redshifts z less than 3 that are like those in the local universe should produce a minimum diffuse background of 0.0085, 0.038, and 0.13 MJy/sr at 25, 60, and 100 microns, respectively. Models with significant luminosity evolution predict backgrounds about a factor of 4 greater than this minimum.
Analytic and numerical results on particle acceleration in 2D collisionless magnetic reconnection are presented. The particles are followed until they reach an outgoing flux surface at the same distance from the origin as the starting surface. The magnetic moment is not conserved for particles passing through the unmagnetized region around the X line at the origin. Other particles cross the separatrix without passing near the X line. The magnetic moment of the first class of outgoing particles is randomized, whereas it can be considered for the second class. The analytic model is based upon the observation of the final kinetic energy as a function of the initial conditions. Analytic results are shown to predict a Maxwellian tail for the distribution function in the perpendicular kinetic energy, with this energy much greater than the parallel kinetic energy. Numerical results showing that the predicted tail temperature agrees with the numerically computed temperature to within 10 percent over 4 orders of magnitude in the electric field are presented.
Ultraviolet auroral images from the Ultraviolet Imager onboard the POLAR satellite can be used as quantitative remote diagnostics of the auroral regions, yielding estimates of incident energy characteristics, compositional changes, and other higher order data products. In particular, images of long and short wavelength N2 Lyman-Birge-Hopfield (LBH) emissions can be modeled to obtain functions of energy flux and average energy that are basically insensitive to changes in seasonal and solar activity changes. This technique is used in this study to estimate incident electron energy flux and average energy during substorm activity occurring on May 19, 1996. This event was simultaneously observed by WIND, GEOTAIL, INTERBALL, DMSP and NOAA spacecraft as well as by POLAR. Here incident energy estimates derived from Ultraviolet Imager (UVI) are compared with in situ measurements of the same parameters from an overflight by the DMSP F12 satellite coincident with the UVI image times.
Knowledge of the prompt fission neutron spectrum is crucial for understanding the behavior of energetic nuclear systems. Although this energy spectrum has been measured for the major actinides {sup 235}U and {sup 239}Pu for decades, the majority of the available literature data lack the coverage of both incident and outgoing neutron energies and the precision required to accurately guide evaluations and fission models. The Chi-Nu experiment is designed to measure the prompt fission neutron spectrum for a wide range of incident and outgoing neutron energies with attention to uncertainty estimation and assessment of systematic errors in order to provide reliable guidance for evaluations and models of nuclear fission. Preliminary results of the prompt fission neutron spectrum from the neutron-induced fission of {sup 235}U and {sup 239}Pu are presented here, with a focus on the presence of spectral features near multi-chance fission thresholds, pre-equilibrium neutrons in the deduced spectrum, and also on trends of the mean fission neutron energy as a function of the incident neutron energy. While the mean energies of from ENDF/B-VIII.0 are in good agreement with those reported for {sup 235}U spectra, significant disagreements exist above an incident neutron energy of approximately 13 MeV for {sup 239}Pu. Furthermore, in general, the physics features regarding multi-chance fission and pre-equilibrium neutron emission newly-introduced into ENDF/B-VIII.0 appear provide an improved description of the data as compared to ENDF/B-VII.1. (authors)
The first group of slides provides background information on the isotopic composition of plutonium. It is shown that 240 Pu is the critical isotope in neutron coincidence/multiplicity counting. Next, response function analysis to determine isotopic composition is discussed. The isotopic composition can be determined by measuring the net peak counts from each isotope and then taking the ratio of the counts for each isotope relative to the total counts for the element. Then FRAM (Fixed energy Response function Analysis with Multiple efficiencies) is explained. FRAM can control data acquisition, automatically analyze newly acquired data, analyze previously acquired data, provide information on the quality of the analysis, and facilitate analysis in unusual situations (non-standard energy calibrations, gamma rays from non-SNM isotopes, poor spectra (within limits)).
In the setting of continuum elasticity martensitic phase transformations are characterized by a non-convex free energy density function that possesses multiple wells in strain space and includes higher-order gradient terms for regularization. Metastable martensitic microstructures, defined as solutions that are local minimizers of the total free energy, are of interest and are obtained as steady state solutions to the resulting transient formulation of Toupin’s gradient elasticity at finite strain. This type of problem poses several numerical challenges including stiffness, the need for fine discretization to resolve microstructures, and following solution branches. Accurate time-integration schemes are essential to obtain meaningful solutions at reasonable computational cost. Here in this work we introduce two classes of unconditionally stable second-order time-integration schemes for gradient elasticity, each having relative advantages over the other. Numerical examples are shown highlighting these features.
Energy systems function as both technological systems and temporal institutions that shape how societies coordinate, justify, and support collective choices over time. This paper introduces the concept of governance horizons to explain why energy transitions can remain morally supported yet become institutionally weak under increasing pressure. We argue that governability depends on institutions' capacity to synchronize across multiple timeframes - aligning short-term decisions with intermediate coordination and long-term commitments. When this synchronization fails, transitions struggle not because their goals are dismissed, but because governance lacks sufficient time to justify, coordinate, and uphold decisions. Comparative analysis of San Antonio, Texas, and Interior Alaska reveals how energy system pressures generate distinct temporal configurations: San Antonio exhibits governance horizon stretching, where institutions must simultaneously meet near-term reliability demands and long-term transformation goals, while Interior Alaska exhibits horizon compression, where extreme environmental constraints force decision-making into short stabilization cycles. In both contexts, public support for sustainability goals coexists with institutional strain because evaluative judgments are unevenly distributed over time. A temporal configuration analysis is introduced as a diagnostic analytic stance for identifying these patterns. By treating temporal alignment as an explanatory variable rather than a background condition, this approach clarifies how feasibility, sequencing, and legitimacy are shaped by constraints on institutional time. The analysis demonstrates that successful energy transitions depend not only on technological innovation or institutional support, but on governance systems’ ability to sustain credible coordination across multiple time horizons.
The time-resolved Electron Energy Distribution Functions (EEDFs) have been measured at different phases of moving striations in a positive column of DC discharge in argon gas. A very low gas pressure of 10 mTorr, a high energy resolution (to resolve the low energy part of the EEDF), and the dynamic range up to 3–4 orders of magnitude (to resolve the EEDF tail) with a temporal resolution of 2.5 μs distinguish our work from previous publications. The measured EEDFs reveal drastic changes in time of their low energy parts with the formation of a low energy peak. The observed EEDF dynamics is explained in the framework of nonlocal electron kinetics as electric field reversals and the trapping of low-energy electrons in potential wells propagating with striation along the discharge tube. Finally, the formation of the low energy peak in the EEDF is similar to that in rf capacitive and inductive discharges at low gas pressures where the low-energy electrons are trapped in the potential well created by the ambipolar electric field and cannot penetrate into the areas of electron heating by strong rf electric fields
We analyze a new mechanism for the creation and confinement of energetic electrons in a mirror-configuration plasma. A Fermi–Ulam-type process, driven by end-localized coherent electrostatic oscillations, provides axial acceleration, while a natural non-adiabaticity of μ provides phase decorrelation and energy isotropization. This novel 2D combination causes the electron energy distribution function, calculated with a diffusive-loss model, to assume a Maxwellian shape with the μ non-adiabaticity, reducing loss-cone escape and annulling the absolute-barrier energy-limiting Chirikov criterion of lower dimensional models. Here, the theoretical predictions are compared with data from an experiment.
The superheavy nuclei push the periodic table of the elements and the chart of the nuclides to their limits, providing a unique laboratory for studies of the electron-nucleus interactions. The most important weak decay mode in known superheavy nuclei is electron capture (EC). In the standard calculations of EC, the lepton wave functions are usually considered in the lowest-order approximation. In this work, we investigate the sensitivity of EC rates on the choice of the electron wave functions by (i) assuming the single-particle approximation for the electron wave functions, and (ii) carrying out Dirac-Hartree-Fock (DHF) calculations. The nuclear response is generated based on the state-of-the-art quasiparticle random phase approximation employing relativistic nuclear energy density functional theory. Here, we show that using the improved lepton wave functions reduces the EC rates up to 40% in the superheavy nucleus oganesson (𝑍=118). Interestingly, because of screening effects, the difference between the EC rates obtained with the DHF and single-particle calculations is fairly small.
Laboratory experiments sensitive to the equation of state of neutron rich matter in the vicinity of nuclear saturation density provide the first rung in a “density ladder” that connects terrestrial experiments to astronomical observations. In this context, the neutron skin thickness of 208 Pb ($R$ $^{208}_{skin}$) provides a stringent laboratory constraint on the density dependence of the symmetry energy. In turn, an improved value of $R$ $^{208}_{skin}$ has been reported recently by the PREX collaboration. Exploiting the strong correlation between $R$ $^{208}_{skin}$ and the slope of the symmetry energy L within a specific class of relativistic energy density functionals, we report a value of L = (106 ± 37) MeV—which systematically overestimates current limits based on both theoretical approaches and experimental measurements. Here, the impact of such a stiff symmetry energy on some critical neutron-star observables is also examined.