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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Preliminary plume characteristics of an arcjet thruster

An experimental investigation of a low power arcjet plume was conducted using emission spectroscopy. A laboratory model arcjet incorporating a segmented anode was run on simulated hydrazine at a flow rate of 5 x 10(exp -5) kg/s. The complete visible spectrum measured in the exit plane of the arcjet showed the presence of N2, N2(+), NH, and H. Radial intensity profiles for the H alpha, H sub beta, and the NH A(sup 3)Pi yields X(sup 3)Sigma(0,0) transitions at four different axial locations were measured. These line of sight intensity measurements, spaced 0.05 mm apart, were deconvoluted to give the radial intensity distribution using an inverse Abel transformation. The ratio between the intensities from the H sub alpha and H sub beta transitions indicated a non-Boltzmann energy distribution between excited states in the plume. Axial intensity profiles taken on center line indicated the decay rate of excited states in the plume. An electron number density of 2 x 10(exp 13)/cu cm at the exit plane was determined based on Stark broadening of the H sub beta line. Rotational temperatures of 750 K, 1750 K, and 2500 K were determined for N2, N2(+), and NH respectively. The results demonstrate that the location of the current attachment on the anode has a measurable effect on the electronically excited species in the plume and that dissociation is the dominant frozen flow loss mechanism in low power arcjets.

Manzella, David H.↗
NASA NTRS1992

P/Machholz 1986 8 and quadrantid meteoroid stream. Orbital evolution and relationship

The evolution of the P/Machholz's meteoroid stream was simulated. It shows that this stream may produce eight meteor showers. There are the known observed meteor showers such as the Quadrantids, Ursids, Northern and Southern delta-Aquarids, Daytime Arietids, and alpha-Cetids. A satisfactory agreement of the theoretical and observed geocentric radiants and orbits allows one to conclude that the above showers could have been resulted from the decay of the P/Machholz nucleus. The age of the stream is estimated to be 7.5 millennia.

Babadzhanov, Pulat B.↗
NASA NTRS2000

Numerical Simulations of Homogeneous Turbulence Using Lagrangian-Averaged Navier-Stokes Equations

The Lagrangian-averaged Navier-Stokes (LANS) equations are numerically evaluated as a turbulence closure. They are derived from a novel Lagrangian averaging procedure on the space of all volume-preserving maps and can be viewed as a numerical algorithm which removes the energy content from the small scales (smaller than some a priori fixed spatial scale alpha) using a dispersive rather than dissipative mechanism, thus maintaining the crucial features of the large scale flow. We examine the modeling capabilities of the LANS equations for decaying homogeneous turbulence, ascertain their ability to track the energy spectrum of fully resolved direct numerical simulations (DNS), compare the relative energy decay rates, and compare LANS with well-accepted large eddy simulation (LES) models.

Mohseni, Kamran↗
NASA NTRS1971

The evolution of hydrogen-helium stars.

Investigation of the premain sequence evolution and the main sequence evolution of stars of 5, 10, 20, 30, 100, and 200 solar masses. Normal stars in this entire mass range normally convert hydrogen into helium by the CN-cycle on the main sequence. The present hydrogen-helium stars of 5 and 10 solar masses must reach higher central temperatures in order to convert hydrogen to helium by the proton-proton chains. Consequently, the mean densities in the stars are greater, and the surface temperatures are higher than in normal stars. In the stars of 20 solar masses and larger, the proton-proton chains do not succeed in supplying the necessary luminosity of the stars by the time the contraction has produced a central temperature near 10 to the 8th K. At that point triple-alpha reactions generate small amounts of C12, which then acts as a catalyst in the CN-cycle, the rate of which is then limited by the beta-decays occurring within the cycle. During the evolution of these more massive stars, the central temperature remains in the vicinity of 10 to the 8th K, and the surface temperature on the main sequence approaches 100,000.

Ezer, D.↗
DOE OSTI2022

Evaluated Nuclear Structure Data File (ENSDF)

Contains recommended nuclear structure and decay data for all the known nuclides, which are obtained following a critical review of all available experimental data, supplemented with systematic trend studies and theoretical models. ENSDF data include (i) nuclear level properties, such as observation source, energy, half-life, decay modes, spin and parity; (ii) gamma ray energies, intensities, multipolarities, mixing ratios and conversion coefficients; (iii) nuclear radiation energy and intensity as well as radiation-specific data for different radiation types, such as such as gammas, alphas, betas and neutrons. Data for about 220 nuclides are fully evaluated each year; additionally, many datasets are partially updated each year. Nearly all the evaluation work is supported by the US Nuclear Data Program. The National Nuclear Data Center at Brookhaven National Laboratory is responsible for coordinating the evaluation effort as well as its web and journal dissemination.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1985

The great flare of 1982 June 6

The great soft X-ray (SXR) flare (X12) of the past solar maximum was observed by Hinotori and by Big Bear Solar Observatory (BBSO) on June 6, 1982. Hinotori data consist of hard X-ray (HXR) and SXR images in the rise and decay of the flare, high-resolution soft X-ray spectra throughout the flare, and HXR and gamma-ray data. The BBSO data include films of H-alpha, H-alpha blue wing, D3 and longitudinal magnetic field, as well as video tapes of continuum. Images in HXR, SXR, H-alpha, D3 and the continuum are compared and SXR spectra analyzed. The flare resulted from extended motion of a large spot shearing the magnetic field. D3 and white-light images exhibit a progression from fast flashes to two ribbons, while both HXR and SXR are centered on the optical kernels. The continuum emission shows the same temporal behavior as the HXR at 160 keV. In its early phases, the Fe XXV line was double-peaked, and a decreasing blueshifted (up to 400 km/sec) component was observed, from which the evaporation rate of chromospheric material was estimated. It is suggested that this upflow is adequate to supply the coronal cloud. Flare energetics are discussed in detail, and it is concluded that a significant amount of energy was deposited in the corona, and that nonthermal electrons are the major energy input.

Tanaka, K.↗
NASA NTRS1990

Microwave structure of the quiet sun at 8.5 GHz

Multifrequency VLA observations of the quiet sun near 8.5 GHz are presented. Two regions of the sun were observed, one dominated by an enhanced network corresponding to a decayed active region, and the other corresponding to an enhanced network with no active features. The full-day synthesis maps for both show nearly perfect correspondence to H-alpha images, and to longitudinal magnetograms. The coronal loops were observed to appear as regions of radio emission with no underlying longitudinal magnetic fields, being aligned with H-alpha fibrils in the photosphere, and connecting regions of opposite magnetic polarity. The emission can be modeled as optically thin free-free emission from a coronal loop with a peak axial density of approximately 2.4-2.8 x 10 to the 9th/cu cm, for an assumed coronal temperature of 1-2 x 10 to the 6th K. The quiet chromosphere sources are measured, and the significance of these measurements for existing chromospheric models is discussed.

Gary, Dale E.↗
DOE OSTI2021

Pulse shape discrimination in CUPID-Mo using principal component analysis

CUPID-Mo is a cryogenic detector array designed to search for neutrinoless double-beta decay ($0\nu\beta\beta$) of $^{100}$Mo. It uses 20 scintillating $^{100}$Mo-enriched Li$_2$MoO$_4$ bolometers instrumented with Ge light detectors to perform active suppression of $\alpha$ backgrounds, drastically reducing the expected background in the $0\nu\beta\beta$ signal region. As a result, pileup events and small detector instabilities that mimic normal signals become non-negligible potential backgrounds. These types of events can in principle be eliminated based on their signal shapes, which are different from those of regular bolometric pulses. We show that a purely data-driven principal component analysis based approach is able to filter out these anomalous events, without the aid of detector response simulations.

47 OTHER INSTRUMENTATION↗
NASA NTRS1971

Solar flares in the extreme ultraviolet.

Measurements of flare-related impulsive enhancements in solar emission lines in the extreme ultraviolet, observed from the satellite OSO-III, are reported. The enhancement of a line, expressed in percent of the total disk intensity in the line, is of the same order of magnitude as the flare area, expressed in heliocentric square degrees. Rise-times and decay-times of impulsive enhancements average about 2 min and 5 min, respectively. The maximum enhancements of radiation from ions in the chromosphere-corona transition region precede the H-alpha maximum by an average of 2 min, and occur in the same period of time as the hard component of solar X rays and the impulsive microwave bursts. Coronal lines in the extreme ultraviolet are less impulsive than the transition region lines in flare-related enhancements and their maxima follow the H-alpha maximum.

Hall, L. A.↗
NASA NTRS1978

Analysis of X-ray observations of the 15 June 1973 flare in active region NOAA 131

Observations and analyses of the 1B/M3 flare of 15 June, 1973 in active region NOAA 131 (McMath 12379) are presented. The X-ray observations, consisting of broadband photographs and proportional counter data from the Skylab/ATM NASA-MSFC/Aerospace S-056 experiment, are used to infer temperatures, emission measures, and densities for the flaring plasma. The peak temperature from the spatially resolved photographs is 25,000,000 K, while the temperature from the full-disk proportional counter data is approximately 15,000,000 K. The density is 3 times 10 to the 10th/cu cm. The X-ray flare emission appears to come primarily from two low-lying curvilinear features lying perpendicular to and centered on the line where the photospheric longitudinal magnetic field is zero. Similarities in the preflare and postflare X-ray emission patterns indicate that no large-scale relaxation of the coronal magnetic configuration was observed. Also discussed are H-alpha and magnetic field observations of the flare and the active region. Finally, results of numerical calculations, including thermal conduction, radiative loss, and chromospheric evaporation, are in qualitative agreement with the decay phase observations.

Krall, K. R.↗
DOE OSTI2023

Development of digital electronics for the search of SHE nuclei using GARIS-II/III at RIKEN

This work describes the implementation of a digital data acquisition system for the search and study of short-lived isotopes or superheavy elements at the GARIS-III separator at the RIKEN Nishina Center. Here a reduction to 26 ± 0.5 keV in the average value of the Full Width at Half Maximum of the alpha spectrum at 7.133 MeV was achieved, combined with a reduction of the dead time of the overall system to around a few tens of nanoseconds for the detection of very fast decay chains. Moreover, we measured a reduction of the background induced by particles crossing the implantation detector using pulse shape analysis techniques. The detail of the optimization and analysis will be presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Progress toward hydro-equivalent ignition in OMEGA direct-drive DT-layered implosions

Considerable progress has been made in deuterium-tritium-layered implosion experiments on the OMEGA Laser System, bringing the prospects for thermonuclear ignition in direct-drive configurations with megajoule-class lasers closer to reality. Doing so has required navigating the balance between improved 1D performance and multidimensional stability. Using statistical modeling based on over 350 cryogenic implosions to identify various degradation mechanisms, and combined with multidimensional simulations and experimental techniques such as target offsets to combat residual flows, core conditions have repeatably been achieved that extrapolate to the burning-plasma state when scaled to 2.15 MJ of symmetric laser illumination. Using high implosion velocities (⁠> 450 km/s) and moderately high adiabats (⁠~5⁠), these experiments produced record-high scaled Lawson parameters in direct drive equal to 89 ± 2% of that required for ignition with expected yields of up to 1.5 ± 0.2 MJ. To improve these results still further, focused physics studies are performed to improve physics understanding and identify routes to even greater performance. Recent studies include investigations into the impact of mounting features, laser imprint, reduced fuel temperatures, and greater on-target intensities through subscale experiments. This manuscript gives a summary of the cryogenic direct-drive program on the OMEGA laser, including routes taken to achieve the current best performance, the status of recent focused physics investigations, and future designs—such as target solutions to laser imprint and reducing vapor density to increase convergence—that are expected lead to the demonstration of hydro-equivalent ignition on OMEGA.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Improvements to the 115g/115m Cd Nuclear Data

Repeated measurements of the isotope 115m Cd by Los Alamos National Laboratory (LANL), Pacific Northwest National Laboratory (PNNL), and Atomic Weapons Establishment (AWE) have revealed a consistent discrepancy between beta and gamma counting. This suggests that a significant disparity exists between the true value of the isotope’s gamma-ray branching ratios and the values reported by the National Nuclear Data Center (NNDC). Enriched 114 Cd was irradiated using thermal neutrons to produce a high-purity 115m/g Cd source for counting and analysis using traditional singles gamma-ray spectroscopy, liquid scintillation counting, gas-proportional counting, and analysis using the new Gamma-Alpha-Beta-Gamma (GABγ) and Gamma-Alpha-Beta Radio-Isotope EvaLuator (GABRIEL) coincidence detection systems. Using the D-T fusion generated neutrons, reduces the wait time required to let the short-lived 115Cd ground state decay away by leveraging the 1:1 production ratio of the ground and metastable state of 115 Cd from the 115 In (n,p) reaction relative to the 10:1 production ratio of the ground and metastable isotopes of 115 Cd by thermal neutron capture on 114 Cd. However, the much higher flux in from the Washington State University TRIGA reactor is a more rapid method of production of 115m/gCd but requires access to enriched 114 Cd. High purity 115m/g Cd samples were analyzed on regular intervals over a period of 140-days. The activity of 115m Cd measured by beta and gamma show a clear discrepancy using the current best known gamma-ray decay branching ratios. Based on these observations and measurements, a set of new branching ratio recommendations have been produced using conventional counting techniques and the advanced GAB? and GABRIEL instruments.

07 ISOTOPE AND RADIATION SOURCES↗
NASA NTRS1980

High-resolution X-ray spectra of solar flares. III - General spectral properties of X1-X5 type flares

High-resolution X-ray spectra of six class X1-X5 solar flares are discussed. The spectra were recorded by spaceborne Bragg crystal spectrometers in the ranges 1.82-1.97, 2.98-3.07 and 3.14-3.24 A. Electron temperatures derived from dielectronic satellite line to resonance line ratios for Fe XXV and Ca XIX are found to remain fairly constant around 22,000,000 and 16,000,000 K respectively during the rise phase of the flares, then decrease by approximately 6,000,000 K during the decay phase. Nonthermal motions derived from line widths for the April 27, 1979 event are found to be greatest during the rise phase (approximately 130 km/sec) and decrease to about 60 km/sec during decay. Volume emission measures for Fe XXV, Ca XIX and Ca XX are derived from photon fluxes as a function of temperature, and examination of the intensity behavior of the Fe K alpha emission as a function of time indicates that it is a result of fluorescence. Differences between the present and previous observations of temperature variation are discussed, and it is concluded that the flare plasmas are close to ionization equilibrium for the flares investigated.

Doschek, G. A.↗
DOE OSTI2021

Ultra low background time projection alpha particle detector ( Phase II Final Scientific/Technical Report)

When alpha particles are emitted into a gas they create an ionization track of gas ions and electrons. In our commercial UltraLo instrument we apply a voltage between a planar sample and an anode, integrate the anode signal as it collects the electrons, and distinguish between alphas emitted from the sample and elsewhere (anode, sidewalls) by the duration and shape of the resultant signal. The major contributors limiting the instrument’s lower detection limit are cosmic rays that pass through the detector close to the sample and Rn decays that produce charge tracks the originate in the gas and end on the sample. In this work we proposed to identify and reject these events by converting the anode into a multi-pixel array and operating in time projection mode. Cosmic rays would be eliminated by generating charge on many pixels, while charge collection asymmetry would distinguish between sample events (Bragg curve up) and Rn events (Bragg curve down). We therefore proposed to modify an UltraLo by pixilating its anode, developing low noise, low power multiplexed electronics to track each pixel’s signal individually, and develop analysis software to make the required discriminations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1982

Statistical aspects of the 1980 solar flars. 1: Data base, frequency distributions, and overview remarks

AII1349 H alpha flares occurring in 1980 which have known start, maximum brightness, and end times, latitudes, and associated importance and X-ray classes were used to perform a statistical study of flare rise time, decay time, duration, latitude, importance (areal and relative intensity), and X-ray class. Frequency distributions of these parameters are tabulated and plotted.

Wilson, R. M.↗
NASA NTRS2010

Measuring and Modeling Solar Flares with SDO EVE

The Flare Irradiance Spectral Model (FISM) currently provides estimations of the solar Vacuum Ultra-Violet (VUV; 0.1-190 nm) irradiance from 1947 to present at 1 nm bins and 60 second temporal resolution. The accuracy of FISM is limited to 1nm because the TIMED SEE Level 3 and Level 3A measurement, for which the FISM relationships were based on, were at Inm. With the launch of the Solar Dynamics Observatory (SDO) in Feb 2010, the EUV Variability Experiment (EVE) will provide more accurate, increased spectral resolution (0.1 nm) measurements from 6 nm to 106 nm every 10-seconds and almost 100% duty cycle. EVE also observes additional broadband measurements for 0.1-7 nm, some EUV bands from 16 nm to 40 nm, and Hydrogen Lyman alpha at 121.6 nm. Along with the better spectral resolution of EVE leading to similar spectral resolution improvements in FISM, other significant improvements provide by SDO/EVE measurements will be multi-thermal gradual phase decay, impulsive phase center-to-limb variation characterization, non-flare sub-daily variations, and multi-thermal proxies. SDO/EVE observations of various solar flares with different characteristics will be presented, with the discussion theme focused on how EVE observations will help improve the accuracy of the FISM in the future. The final topic will present the updated FISM website that now has easier access to the FISM results and produce real-time updates that are useful for Space Weather studies.

Chamberlin, Phillip C.↗
DOE OSTI2021

Constraining Cosmic Microwave Background Temperature Evolution With Sunyaev–Zel’Dovich Galaxy Clusters from the Atacama Cosmology Telescope

The Sunyaev–Zel'dovich (SZ) effect introduces a specific distortion of the blackbody spectrum of the cosmic microwave background (CMB) radiation when it scatters off hot gas in clusters of galaxies. The frequency dependence of the distortion is only independent of the cluster redshift when the evolution of the CMB radiation is adiabatic. Here, using 370 clusters within the redshift range 0.07 ≲ z ≲ 1.4 from the largest SZ-selected cluster sample to date from the Atacama Cosmology Telescope, we provide new constraints on the deviation of CMB temperature evolution from the standard model $\alpha ={0.017}_{-0.032}^{+0.029}$, where $T(z)={T}_{0}{\left(1+z\right)}^{1-\alpha }$. This result is consistent with no deviation from the standard adiabatic model. Combining it with previous, independent data sets we obtain a joint constraint of α = –0.001 ± 0.012. Attributing deviation from adiabaticity to the decay of dark energy, this result constrains its effective equation of state ${w}_{\mathrm{eff}}=-{0.998}_{-0.010}^{+0.008}$.

79 ASTRONOMY AND ASTROPHYSICS↗