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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Measurement of away-side broadening with self-subtraction of flow in Au+Au collisions at ${{\sqrt{s_{NN}} = 200}}$ GeV

High transverse momentum ($p_T$) particle production is suppressed due to parton (jet) energy loss in the hot dense medium created in relativistic heavy-ion collisions. Redistribution of energy at low-to-modest $p_T$ has been elusive to measure because of large anisotropic backgrounds. Here, we report a novel data-driven method for background evaluation and subtraction, exploiting the away-side pseudorapidity gaps, to measure the jetlike correlation shape in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV with the STAR experiment. The correlation shapes, for trigger particle $p_T$ > 3 GeV/$c$ and various associated particle $p_T$ ranges within 0.5 < $p_T$ < 10 GeV/$c$, are consistent with Gaussians and their widths are found to increase with centrality. The results indicate jet broadening in the medium created in central heavy-ion collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

High power coupler development for EIC

The synchrotron radiation loss in EIC Electron Storage Ring is as high as up to 10 MW. This energy loss will be compensated by 17 2K 591 MHz single-cell SRF cavities with a combined total of 34 high power fundamental power couplers. Each power coupler will operate 92% of revolution time CW and ~8% of revolution time with 400 kW forward power due to the beam abort gap. To satisfy the EIC needs, we developed two 500 kW standing-wave FPC designs at BNL based on either a BeO and an Al 2 O 3 RF window. This paper will briefly summarize test results of the BeO window FPC , and describe the design development of the Al 2 O 3 window based FPC.

43 PARTICLE ACCELERATORS↗
NASA NTRS1973

Variations of the relative abundances of He, (C,N,O) and Fe-group nuclei in solar cosmic rays and their relationship to solar particle acceleration

Measurements of the flux of helium nuclei in the 24 January 1971 event and of helium and (C,N,O) nuclei in the 1 September 1971 event are combined with previous measurements to obtain the relative abundances of helium, (C,N,O), and Fe-group nuclei in these events. These data are then summarized together with previously reported results to show that, even when the same detector system using a dE/dx plus range technique is used, differences in the He/(C,N,O) value in the same energy/nucleon interval are observed in solar cosmic ray events. Further, when the He/(C,N,O) value is lower the He/(Fe-group nuclei) value is also systematically lower in these large events. When solar particle acceleration theory is analyzed, it is seen that the results suggest that, for large events, Coulomb energy loss probably does not play a major role in determining solar particle composition at higher energies (10 MeV). The variations in multicharged nuclei composition are more likely due to partial ionization during the acceleration phase.

Bertsch, D. L.↗
NASA NTRS1974

Acceleration, containment, and emission of very low energy solar flare particles

We present the first observations of protons down to 44 keV and electrons down to less than about 2 keV emitted in an impulsive solar particle event. The observations are from the Apollo 15 Subsatellite during a flare event which began on September 1, 1971. We obtain a lower limit estimate of the energy contained in protons above about 0.05 MeV in the flare. The effects of adiabatic deceleration in the interplanetary medium and dE/dx energy loss in the corona are discussed. We conclude that energetic protons may constitute a major energy release in large solar flares.

Lin, R. P.↗
NASA NTRS1976

Formation of the 0.511 MeV line in solar flares

The slowing down and annihilation of positrons and the formation of positronium in a solar flare plasma are investigated to determine how the width of the 0.511-MeV line and its strength relative to the three-photon continuum from positronium decay depend on the temperature and density of the medium in which the positron comes to rest. The calculations are limited to the cases of annihilation in a completely ionized plasma, in a partially ionized plasma with an electron/neutron density ratio of 1.0 or 0.1, and in an atomic gas with a very small ion density. Thermally averaged rate coefficients are obtained for the free annihilation of positrons and for positronium formation through radiative recombination in the fully ionized plasma. Positronium formation rates and the resultant energy distributions of the positronium atoms in the partially ionized medium are determined by numerically solving the Fokker-Planck equation in a medium where the ambient free electrons have a Maxwell-Boltzmann distribution of finite temperature but the density of the medium is sufficiently low that positronium atoms decay without further collisions following their formation. A Monte Carlo calculation is performed for the positron energy loss, positronium formation through charge exchange, and positronium breakup in the weakly ionized medium. The energy distributions of decaying positronium atoms and the relative number of triplet to singlet positronium decays are evaluated for ion concentrations and densities characteristic of the solar photosphere.

Crannell, C. J.↗
NASA NTRS1979

The energy balance and pressure in the solar transition zone for network and active region features

The electron pressure and energy balance in the solar transition zone are determined for about 125 network and active region features on the basis of high spectral and spatial resolution extreme ultraviolet spectra. Si III line intensity ratios obtained from the Naval Research Laboratory high-resolution telescope and spectrograph during a rocket flight are used as diagnostics of electron density and pressure for solar features near 3.5 x 10 to the 4th K. Observed ratios are compared with the calculated dependence of the 1301 A/1312 A and 1301 A/1296 A line intensity ratios on electron density, temperature and pressure. Electron densities ranging from 2 x 10 to the 10th/cu cm to 10 to the 12th/cu cm and active region pressures from 3 x 10 to the 15th to 10 to the 16th/cu cm K are obtained. Energy balance calculations reveal the balance of the divergence of the conductive flux and turbulent energy dissipation by radiative energy losses in a plane-parallel homogeneous transition zone (fill factor of 1), and an energy source requirement for a cylindrical zone geometry (fill factor less than 0.04).

Nicolas, K. R.↗
NASA NTRS1982

Transport of energetic electrons in a fully ionized hydrogen plasma

A Monte Carlo method for calculating energetic electron transport in a plasma is presented. The energy loss and angular deflection due to Coulomb collisions as a function of travel distance and energy are derived for energetic electrons in a fully ionized plasma with a uniform magnetic field. Formulas which include the effect of nonuniform B fields on the angular deflection are derived. The Monte Carlo method is applied to the thick-target beam model in which the energetic electrons are injected vertically downward.

Bai, T.↗
NASA NTRS1985

Energetics of a double flare on November 8, 1980

In the energy balance analysis of a double impulsive hard X-ray flare presently completed, it is deduced on the basis of spatial observations that both flares probably occur in the same loop, within the resolution limits of the data. Total energy losses are noted to be a factor of two lower than the calculated fast electron energy; this is interpreted as an indication that the first flare occurred in a small loop, with fast electrons heating the chromosphere and resulting in a chromospheric evaporation that increased the density in the loop. For the second flare, most of the heating occurred at the electron acceleration site. The estimated altitude of the acceleration site is 5500 km above the photosphere.

Doyle, J. G.↗
NASA NTRS2002

Solar Selective Coatings Developed for Space Power Applications

A solar collector having the combined properties of high solar absorptance, low infrared emittance, and high thermal conductivity is envisioned for space power applications on minisatellites. A high solar absorptance is needed to collect as much of the incident solar radiation as possible and a low infrared emittance is needed to minimize radiant energy losses. A lightweight material having a high thermal conductivity is needed to transport the absorbed energy to where it is needed. Such a solar collector may be used with a low temperature-differential heat engine to provide electric power to the minisatellite components or as a source of thermal energy for a thermal bus that would heat remote regions of the spacecraft. The key to such a collector is the use of cermet coatings. Cermet coatings are composed of molecular islands of metal embedded in a three-dimensional matrix of dielectric. Recent research on molecular mixtures of aluminum and aluminum oxide at the NASA Glenn Research Center has yielded cermet coatings with a solar absorptance a of 0.797 and an infrared emittance epsilon of 0.131, yielding an alpha/epsilon ratio of 6. Although additional work is needed to further increase the alpha/epsilon ratio, these coatings are attractive owing to their potential durability in the space environment. The aluminum oxide surface should provide substantial protection from the atomic oxygen found in low Earth orbit. To help minimize emittance, these coatings are deposited on a smooth surface. The selected surface is aluminum that has been diamond turned to a mirror finish. Cermet coatings are manufactured by sputter deposition. To achieve the desired variable composition, Glenn's researchers implemented a novel approach using a cylindrical target composed of aluminum and aluminum oxide. Rotating the cylinder during the deposition process yields a coating of variable composition. A photograph of the custom-made aluminum and aluminum oxide cylindrical target installed in the sputter deposition chamber is shown.

Jaworske, Donald A.↗
NASA NTRS2007

Description of a Generalized Analytical Model for the Micro-dosimeter Response

An analytical prediction capability for space radiation in Low Earth Orbit (LEO), correlated with the Space Transportation System (STS) Shuttle Tissue Equivalent Proportional Counter (TEPC) measurements, is presented. The model takes into consideration the energy loss straggling and chord length distribution of the TEPC detector, and is capable of predicting energy deposition fluctuations in a micro-volume by incoming ions through both direct and indirect ionic events. The charged particle transport calculations correlated with STS 56, 51, 110 and 114 flights are accomplished by utilizing the most recent version (2005) of the Langley Research Center (LaRC) deterministic ionized particle transport code High charge (Z) and Energy TRaNsport WZETRN), which has been extensively validated with laboratory beam measurements and available space flight data. The agreement between the TEPC model prediction (response function) and the TEPC measured differential and integral spectra in lineal energy (y) domain is promising.

Badavi, Francis F.↗
DOE OSTI2021

HIGH POWER COUPLER DEVELOPMENT FOR EIC

The synchrotron radiation loss in EIC Electron Storage Ring is as high as up to 10 MW. This energy loss will be compensated by 17 2K 591 MHz single-cell SRF cavities with a combined total of 34 high power fundamental power couplers. Each power coupler will operate 92% of revolution time CW and ~8% of revolution time with 400 kW forward power due to the beam abort gap. To satisfy the EIC needs, we developed two 500 kW standing-wave FPC designs at BNL based on either a BeO and an Al2O3 RF window. This paper will briefly summarize test results of the BeO window FPC, and describe the design development of the Al2O3 window based FPC.

43 PARTICLE ACCELERATORS↗
NASA NTRS1991

Opacity effects on the radiative losses of coronal loops

This paper presents calculations of radiative losses, which include the effects of geometry and optical depth, that can be used to improve the energy losses in many flux-tube calculations for loops with constant and variable cross sections. The results include the non-LTE ionization state of hydrogen and helium, thus allowing the determination of the ionization energy in the gas and the relative importance of collisional and radiative processes. These calculations show that optical depth effects are important under solar conditions in the temperature range of 8000-40,000 K.

Kuin, N. P. M.↗
NASA NTRS1978

Absorption of solar radiation by alkali vapors

A theoretical study of the direct absorption of solar radiation by the working fluid of high temperature, high efficiency energy converters has been carried out. Alkali vapors and potassium vapor in particular were found to be very effective solar absorbers and suitable thermodynamically for practical high temperature cycles. Energy loss via reradiation from a solar boiler was shown to reduce the overall efficiency of radiation-heated energy converters, although a simple model of radiation transfer in a potassium vapor solar boiler revealed that self-trapping of the reradiation may reduce this loss considerably. A study was also made of the requirements for a radiation boiler window. It was found that for sapphire, one of the best solar transmitting materials, the severe environment in conjunction with high radiation densities will require some form of window protection. An aerodynamic shield is particularly advantageous in this capacity, separating the window from the absorbing vapor to prevent condensation and window corrosion and to reduce the radiation density at the window.

Mattick, A. T.↗
DOE OSTI2022

An experimental study on round-trip efficiency of a preheating control with a medium office building

The interactions between building energy efficiency and demand response (DR) with buildings may complicate their impacts on the electricity grid and buildings, yet those interactions are not well understood. This work fills this gap by presenting an experimental study that quantifies the effects of DR on building energy efficiency. Unlike existing studies, this work 1) investigates the uncertainty levels when assessing the effects of DR; 2) studies the impact of rooftop heat pumps with direct expansion refrigerant-to-air coils on the round-trip efficiency. Specifically, we considered a medium office building (~1860 m 2 ), which is served by rooftop units, located in eastern Washington State. We performed preheating control tests during typical heating days in the year 2022 and compared the building’s energy consumption during the testing days to that during normal operation days under similar weather conditions. To understand how well those normal operation days represent the baseline for the assessment, the relationship between the energy performance of this building and weather conditions was also studied. Experimental results reveal that the round-trip efficiency (i.e., the ratio of discharging energy output from the building to charging energy input into the building) was between 0.16 and 0.92. The results show that significant energy loss may occur during the preheating process. Finally, it also suggests a significant correlation between the energy efficiency of the studied building under the preheating control and the outdoor temperature; and a highly nonlinear relationship between the zone temperature changing rate and the weather condition.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

Precise ${dd}$ excitations and commensurate intersite Coulomb interactions in the dissimilar cuprates YBa 2 Cu 3 O 7–y and La 2–x Sr x CuO 4

Using high-resolution extreme ultraviolet resonant inelastic X-ray scattering (EUVRIXS) spectroscopy at Cu M-edge, we observed the doping dependent spectral shifts of inter-orbital (${dd}$) excitations of YBa 2 Cu 3 O 7-y and La 2-x Sr x CuO 4 . With increasing hole doping level from undoped to optimally doped superconducting compositions, the leading edge of ${dd}$ excitations is found to shift towards lower energy loss in a roughly linear trend that is irrespective to the cuprate species. The magnitude of energy shift can be explained by including a 0.15 eV Coulomb attraction between Cu 3d(x 2 -y 2 ) electrons and the doped holes on the surrounding oxygens in the atomic multiplet calculations. Finally, the consistent energy shift between distinct cuprate families suggests that this inter-site Coulomb interaction energy scale is relatively material-independent, and provides an important reference point for understanding charge density wave phenomena in the cuprate phase diagram.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1977

Ionization induced damage in crystalline silicon

Close examination of the interaction of the energetic knock-on atoms with the local lattice environment reveals a damage mechanism which does satisfy the experimental data on proton irradiation of silicon. A proton-atom interaction with high energy transfer is considered where the proton path is delineated by a trail of ionization, and the silicon ion path is characterized by much heavier ionization terminating in a dense displacement cluster. At collision, many of the silicon electrons are stripped off, and the resulting energetic ion subsequently loses energy rapidly by Coulomb interaction with bound electrons. The rate of energy loss depends on the charge state and velocity of the knock-on ion. For ion energies in excess of 1 MeV, the intensity of ionization is sufficient to permit lattice atoms, stripped of their binding electrons, to reorient randomly before having an opportunity to recombine with electrons and re-establish the lattice. The path of a knock-on ion thus becomes a thin cylinder of amorphous material within the crystal. Amorphous silicon has a Fermi level closer to mid-band than does single crystal silicon, and a strong field therefore, results around this damaged region. The field produces a large depletion region, representing a very large capture cross section for minority carriers.

Meulenberg, A., Jr.↗
NASA NTRS1987

Energetics of oscillating lifting surfaces using integral conservation laws

The energetics of oscillating flexible lifting surfaces in two and three dimensions is calculated by the use of integral conservation laws in inviscid incompressible flow for general and harmonic transverse oscillations. Total thrust is calculated from the momentum theorem and energy loss rate due to vortex shedding in the wake from the principle of conservation of mechanical energy. Total power required to maintain the oscillations and hydrodynamic efficiency are also determined. In two dimensions, the results are obtained in closed form. In three dimensions, the distribution of vorticity on the lifting surface is also required as input to the calculations. Thus, unsteady lifting-surface theory must be used as well. The analysis is applicable to oscillating lifting surfaces of arbitrary planform, aspect ratio, and reduced frequency and does not require calculation of the leading-edge thrust.

Ahmadi, Ali R.↗