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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

CALET on the International Space Station: the first three years of observations

The CALorimetric Electron Telescope CALET is a space instrument designed to carry out precision measurements of high energy cosmic-rays on the JEM-EF external platform on the International Space Station, where it has been collecting science data continuously since mid-October 2015. In addition to its primary goal of identifying nearby sources of high-energy electrons and possible signatures of dark matter in the electron spectrum, CALET is carrying out extensive measurements of the energy spectra, relative abundances and secondary-to-primary ratios of elements from proton to iron, and even above (up to Z = 40), studying the details of galactic particle propagation and acceleration. An overview of CALET based on the data taken during the first three years of observations is presented, including a direct measurement of the electron+positron energy spectrum from 11 GeV to 4.8 TeV. The proton spectrum has been measured from 50 GeV to 10 TeV covering, for the first time with a single space-borne instrument, the whole energy interval previously investigated in separate sub-ranges by magnetic spectrometers and calorimetric instruments. Preliminary spectra of cosmic-ray nuclei are also presented, together with gamma-ray observations and searches for an e.m. counterpart of LIGO/ Virgo GW events.

P Brogi↗
NASA NTRS1990

Spatial variations in the suprathermal ion distributions during substorms in the plasma sheet

The preinjection and postinjection suprathermal energy spectra of the ion species H(+), O(+), He(+), and He(++) in two events in which substorm-associated particle injections were observed in both the near-earth plasma sheet and farther down the tail were determined using data obtained by the Suprathermal Energetic Ion Charge Analyzer on AMPTE IRM and the Charge Energy Mass Spectrometer on AMPTE CCE. Similar spectral changes were observed in both locations. In both cases, the spectra became harder with injection. Postinjection, the flux decreased exponentially with radial distance. The gradients observed for all ion species were very similar.

Kistler, L. M.↗
NASA NTRS1972

Observations of Interchange Between Acceleration and Thermalization Processes in Auroral Electrons

The results of high time-resolution measurements of energetic electrons in an auroral break up are presented. Electrons with energies from 500 eV to over 100 keV and pitch angles from 0 to 150 deg were detected with two detectors onboard sounding rocket 18:63 UE. Complete energy spectra were taken every 0.1 seconds. The procedure for cleaning and activating the BeCu dynodes of a small, rugged, high gain electron multiplier is described. A theoretical study of the energy-angular response of a spherical plate electrostatic analyzer is compared to experimental results. An energy spectrum unfolding technique which does not require the assumption of a histogram-type energy spectrum is presented. A method of determining sounding rocket orientation from the output of a single magnetometer is described.

Pongratz, M. B.↗
NASA NTRS1994

Fourfold Clusters of Rovibrational Energies in H2Te Studied With an Ab Initio Potential Energy Function

We report an ab initio investigation of the cluster effect (i.e., the formation of nearly degenerate, four member groups of rotation-vibration energy levels at higher J and K(sub a). values) in the H2Te molecule. The potential energy function has been calculated ab initio at a total of 334 molecular geometries by means of the CCSD(T) method where the (1s-4f) core electrons of Te were described by an effective core potential. The values of the potential energy function obtained cover the region up to around 10,000/cm above the equilibrium energy. On the basis of the ab initio potential, the rotation-vibration energy spectra of H2Te-130 and its deuterated isotopomers have been calculated with the MORBID (Morse Oscillator Rigid Bender Internal Dynamics) Hamiltonian and computer program. In particular, we have calculated the rotational energy manifolds for J less than or = 40 in the vibrational ground state, the upsilon(sub 2) state, the "first triad" (the upsilon(sub l)/upsilon(sub 3)/2upsilon(sub 2) interacting vibrational states), and the "second triad" (the upsilon(sub 1) + upsilon(sub 2/upsilon(sub 2) + upsilon(sub 3)/3upsilon(sub 2) states) of H2Te-130. We find that the cluster formation in H2Te is very similar to those of of H2Se and H2S, which we have studied previously. However, contrary to semiclassical predictions, we do not determine any significant displacement of the clusters towards lower J values relative to H2Se. Hence the experimental observation of the cluster states in H2Te will be at least as difficult as in H2Se.

Jensen, Per↗
NASA NTRS2005

The Electron Spectrum above 20 GeV Measured by ATIC-2

The Advanced Thin Ionization Calorimeter (ATIC) Balloon Experiment has been flown from McMurdo, Antarctica in 2000-01 (test flight) and 2002-03 (science flight). ATIC is composed of a segmented BGO calorimeter following a carbon target with scintillator tracking layers and a Silicon matrix detector at the entrance. ATIC measures the composition and energy spectra of the nuclei plus electrons. We present the electron spectrum derived from the ATIC-2 science flight, from 20 GeV to 1.5 TeV, and compare it to existing very high energy measurements from emulsion chambers and to the results of galactic propagation calculations. The good energy resolution and high statistics in the ATIC data allow detailed astrophysical interpretation of the results.

Chang, J.↗
NASA NTRS2006

Dynamic Theory of Relativistic Electrons Stochastic Heating by Whistler Mode Waves with Application to the Earth Magnetosphere

In the Hamiltonian approach an electron motion in a coherent packet of the whistler mode waves propagating along the direction of an ambient magnetic field is studied. The physical processes by which these particles are accelerated to high energy are established. Equations governing a particle motion by group symmetries of the problem were transformed in to a closed pair of nonlinear difference equations. The solutions of these equations have shown there exists the energetic threshold below that the electron motion is regular, and when the initial energy is above the threshold an electron moves stochastically. It is proved that the upper boundary of particle stochastic heating is conditioned by intrinsic property of the particle chaotic motion. Particle energy spectra and pitch angle electron scattering are described by the Fokker-Planck-Kolmogorov equations. It is shown that significant pitch angle diffusion occurs for the Earth radiation belt electrons with energies from a few keV up to a few MeV.

Khazanov, G. V.↗
NASA NTRS2014

Comparison of Martian Surface Radiation Predictions to the Measurements of Mars Science Laboratory Radiation Assessment Detector (MSL/RAD)

For the analysis of radiation risks to astronauts and planning exploratory space missions, detailed knowledge of particle spectra is an important factor. Detailed measurements of the energetic particle radiation environment on the surface of Mars have been made by the Mars Science Laboratory Radiation Assessment Detector (MSL-RAD) on the Curiosity rover since August 2012, and particle fluxes for a wide range of ion species (up to several hundred MeV/u) and high energy neutrons (8 - 1000 MeV) have been available for the first 200 sols. Although the data obtained on the surface of Mars for 200 sols are limited in the narrow energy spectra, the simulation results using the Badhwar-O'Neill galactic cosmic ray (GCR) environment model and the high-charge and energy transport (HZETRN) code are compared to the data. For the nuclear interactions of primary GCR through Mars atmosphere and Curiosity rover, the quantum multiple scattering theory of nuclear fragmentation (QMSFRG) is used, which includes direct knockout, evaporation and nuclear coalescence. Daily atmospheric pressure measurements at Gale Crater by the MSL Rover Environmental Monitoring Station are implemented into transport calculations for describing the daily column depth of atmosphere. Particles impinging on top of the Martian atmosphere reach the RAD after traversing varying depths of atmosphere that depend on the slant angles, and the model accounts for shielding of the RAD by the rest of the instrument. Calculations of stopping particle spectra are in good agreement with the RAD measurements for the first 200 sols by accounting changing heliospheric conditions and atmospheric pressure. Detailed comparisons between model predictions and spectral data of various particle types provide the validation of radiation transport models, and thus increase the accuracy of the predictions of future radiation environments on Mars. These contributions lend support to the understanding of radiation health risks to astronauts for the planning of various mission scenarios.

Kim, Myung-Hee Y.↗
NASA NTRS1972

Enrichment of very heavy nuclei in the composition of solar accelerated particles.

Measurement of the abundances of the nuclei C, N, O, Ne, Mg, Si, Ar, and Ca and the group Cr-Co relative to oxygen from seven solar energetic-particle events in the energy range from about 14 to 61 MeV per nucleon with a solid-state detector telescope on the OGO-5 satellite, 1968-1971. The differential energy spectra of O (14 to 29 MeV per nucleon) and Cr-Co (3 to 61 MeV per nucleon) have a spectral index of about (-3) for a power law in kinetic energy. The relative abundances of C, N, O, and Ne are in excellent agreement with emulsion studies. However, when compared with the solar photospheric and coronal abundances, the OGO-5 measurements show a large enhancement of relative abundances beginning with Si, and extending to the Cr-Co group. The enhancement over the solar and universal abundances is in rough agreement with the composition of the galactic cosmic radiation.

Mogro-Campero, A.↗
NASA NTRS1976

Radioactivity in the galactic plane

The paper reports the detection of a large concentration of interstellar radioactivity during balloon-altitude measurements of gamma-ray energy spectra in the band between 0.02 and 12.27 MeV from galactic and extragalactic sources. Enhanced counting rates were observed in three directions towards the plane of the Galaxy; a power-law energy spectrum is computed for one of these directions (designated B 10). A large statistical deviation from the power law in a 1.0-FWHM interval centered near 1.16 MeV is discussed, and the existence of a nuclear gamma-ray line at 1.15 MeV in B 10 is postulated. It is suggested that Ca-44, which emits gamma radiation at 1.156 MeV following the decay of radioactive Sc-44, is a likely candidate for this line, noting that Sc-44 arises from Ti-44 according to explosive models of supernova nucleosynthesis. The 1.16-MeV line flux inferred from the present data is shown to equal the predicted flux for a supernova at a distance of approximately 3 kpc and an age not exceeding about 100 years.

Walraven, G. D.↗
NASA NTRS1977

Observations of 10-eV to 25-keV electrons in steady diffuse aurora from Atmosphere Explorer C and D

Electron energy spectra from 10 eV to 25 keV have been obtained from steady diffuse auroral forms at altitudes above 150 km by the Atmosphere Explorer C and D spacecraft. Overlapping coverage of the energy range was provided by the photoelectron spectrometer experiment (10-500 eV) and the low-energy electron experiment (0.2-25 keV). The spectral shape between 10 and 20 eV is independent of altitude between 150 and 270 km, has variable energy dependence between about 20 and 150 eV, and above approximately 150 eV has energy dependence determined primarily by the details of the energy spectrum of electrons incident on the atmosphere. The observed results are in satisfactory agreement with two recently published model calculations.

Peterson, W. K.↗
NASA NTRS1988

Shot noise cross-correlation functions and cross spectra - Implications for models of QPO X-ray sources

The cross-correlation functions (CCFs) and cross spectra expected for quasi-periodic oscillation (QPO) shot noise models are calculated under various assumptions, and the results are compared to observations. Effects due to possible coherence of the QPO oscillations are included. General formulas for the cross spectrum, the cross-phase spectrum, and the time-delay spectrum for QPO shot models are calculated and discussed. It is shown that the CCFs, cross spectra, and power spectra observed for Cyg X-e2 imply that the spectrum of the shots evolves with time, with important implications for the interpretation of these functions as well as of observed average energy spectra. The possible origins for the observed hard lags are discussed, and some physical difficulties for the Comptonization model are described. Classes of physical models for QPO sources are briefly addressed, and it is concluded that models involving shot formation at the surface of neutron stars are favored by observation.

Shibazaki, N.↗
NASA NTRS1972

Advanced dosimetry systems for the space transport and space station

Advanced dosimetry system concepts are described that will provide automated and instantaneous measurement of dose and particle spectra. Systems are proposed for measuring dose rate from cosmic radiation background to greater than 3600 rads/hr. Charged particle spectrometers, both internal and external to the spacecraft, are described for determining mixed field energy spectra and particle fluxes for both real time onboard and ground-based computer evaluation of the radiation hazard. Automated passive dosimetry systems consisting of thermoluminescent dosimeters and activation techniques are proposed for recording the dose levels for twelve or more crew members. This system will allow automatic onboard readout and data storage of the accumulated dose and can be transmitted to ground after readout or data records recovered with each crew rotation.

Wailly, L. F.↗
NASA NTRS1977

The streaming of 1.3 - 2.3 MeV cosmic-ray protons during periods between prompt solar particle events

The anisotropy of 1.3 to 2.3 MeV protons in interplanetary space was measured using the Caltech electron/isotope spectrometer aboard IMP-7 for 317 6 hour periods from 72/273 to 74/2. Periods dominated by prompt solar particle events are not included. The convective and diffusive anisotropies were determined from the observed anisotropy using concurrent solar wind speed measurements and observed energy spectra. The diffusive flow of particles was found to be typically toward the sun, indicating a positive radial gradient in the particle density. This anisotropy was inconsistent with previously proposed sources of low energy proton increases seen at 1 AU which involve continual solar acceleration. The typical properties of this new component of low-energy cosmic rays were determined for this period which is near solar minimum.

Marshall, F. E.↗
NASA NTRS2019

CALET Results After Three Years on Orbit on the International Space Station

The CALorimetric Electron Telescope (CALET) is an astroparticle physics experiment installed on the International Space Station since August 2015. The CALET mission was conceived to address several outstanding questions of high-energy astroparticle physics, like indirect detection of dark matter, the origin of cosmic rays (CRs), their mechanisms of acceleration and galactic propagation, the presence of possible nearby astrophysical CR sources. That can be achieved by precise measurements of the fluxes of CR electrons and gamma-rays up to the unexplored region above 1 TeV, and the energy spectra and composition of CR nuclei from a few tens of GeV to hundreds of TeV. In order to perform these observations, the instrument combines a thick total absorption PWO crystal calorimeter for energy measurement, a scintillator hodoscope for charge identi cation and thin imaging tungsten-scintillating fiber calorimeter providing accurate particle tracking and complementary charge measurement. In this paper, we will present an overview of the main CALET results based on the data collected in the first three years of the mission.

P Maestro↗