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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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NASA NTRS1992

Accelerated cometary ions observed downstream of the Comet Halley bow shock

Results are presented of fluxes of energetic ions with energies exceeding 100 keV that were detected upstream of the bow shock of Comet Halley by the Tuende instrument on board the VEGA 1 spacecraft. Downstream of the shock, ion fluxes in the energy range 100 to 180 keV were observed. The measured ion fluxes were transformed into distribution functions in the solar wind frame using a variety of assumptions concerning the energy dependence of the distribution function and the identity of the ion species. The derived distribution function upstream of the shock falls off steeply with energy between 100 and 150 keV, with an effective temperature of about 7 keV or spectral index of about -15. The distribution function increases with decreasing cometocentric distance, on average, reaching a maximum at the bow shock. The measured distribution functions are compared with those obtained by similar instruments on Giotto and ICE as well as with the predictions of several theoretical models that employ different acceleration mechanisms.

Kecskemety, K.↗

NASA NTRS1994

Evidence of circumstellar matter surrounding the Hercules X-1 system

We analyze data from two eclipse ingresses of Her X-1 observed with Ginga on 1989 April 30 and May 19. These observations occur, respectively, during the MAIN HIGH and SHORT HIGH states in the 35 day modulation of Her X-1 intensity. We find significant residual X-ray flux during eclipse, with a gradual decrease in flux following the occultation of the neutron star by the atmosphere of HZ Her. During the central part of the eclipse the count rate becomes nearly constant, at 0.5 mCrab in the energy range 1.7-36.8 keV. From a spectral analysis of the residual emission during the total eclipse of the central source in the MAIN HIGH state, we determine the energy spectral index, alpha = 0.8, similar to that before eclipse. A remarkable feature of the eclipse spectrum is that it does not show a significant iron line feature in contrast to massive wind-fed pulsars, such as Vela X-1 and Cen X-3. From a timing analysis of the same eclipse data, we show that there are no pulses. These results imply that the emission comes from the scattering of continuum X-rays by material in a region considerably larger than the companion star. An extended accretion disk corona may be responsible for this scattering. However, partial eclipse of an extended accretion disk corona may be responsible for this scattering. However, partial eclipse of an extended accretion disk corona is insufficient to account for the count rates in mid-eclipse, when known parameters of the binary system are used. Based on the present results, we suggest that scattering occurs not only in the accretion disk corona but also in the circumstellar matter surrounding the system of Her X-1/HZ Her.

Choi, C. S.↗

NASA NTRS1997

Using Strong Solar Coronal Emission Lines as Coronal Flux Proxies

A comparison of Skylab results with observations of the strong EUV lines of Fe XVI at 335 A and 361 A from the Goddard Solar EUV Rocket Telescope and Spectrograph (SERTS) flight of 1989 suggests that these lines, and perhaps others observed with SERTS, might offer good proxies for estimating the total coronal flux over important wavelength ranges. In this paper, we compare SERTS observations from a later, 1993 flight with simultaneous cospatial Yohkoh soft X-ray observations to test this suggestion over the energy range of the Soft X-ray Telescope (SXT) on Yohkoh. Both polynomial and power-law fits are obtained, and errors are estimated, for the SERTS lines of Fe XVI 335 A and 361 A, Fe XV 284 A and 417 A, and Mg IX 368 A. It is found that the power-law fits best cover the full range of solar conditions from quiet Sun through active region, though not surprisingly the 'cooler' Mg IX 368 A line proves to be a poor proxy. The quadratic polynomial fits yield fair agreement over a large range for all but the Mg IX line, but the linear fits fail conspicuously when extrapolated into the quiet Sun regime. The implications of this work for the He 11 304 A line formation problem are briefly considered. The paper concludes with a discussion of the value of these iron lines observed with SERTS for estimating stellar coronal fluxes, as observed for example with the EUVE satellite.

Falconer, David A.↗

NASA NTRS2004

Measurement of the Abundance of Radioactive Be-10 and Other Light Isotopes in Cosmic Radiation Up to 2 GeV /Nucleon with the Balloon-Borne Instrument Isomax

The Isotope Magnet Experiment (ISOMAX), a balloon-borne superconducting magnet spectrometer, was designed to measure the isotopic composition of the light isotopes (3 les than or = Z less than or = 8) of cosmic radiation up to 4 GeV/nucleon with a mass resolution of better than 0.25 amu by using the velocity versus rigidity technique. To achieve this stringent mass resolution, ISOMAX was composed of three major detector systems: a magnetic rigidity spectrometer with a precision drift chamber tracker in conjunction with a three-layer time-of-flight system, and two silica-aerogel Cerenkov counters for velocity determination. A special emphasis of the ISOMAX program was the accurate measurement of radioactive Be-10 with respect to its stable neighbor isotope Be-9, which provides important constraints on the age of cosmic rays in the Galaxy. ISOMAX had its first balloon flight on 1998 August 4-5 from Lynn Lake, Manitoba, Canada. Thirteen hours of data were recorded during this flight at a residual atmosphere of less than 5 g/sq cm. The isotopic ratio at the top of the atmosphere for Be-10/Be-9 was measured to be 0.195 +/- 0.036 (statistical) +/- 0.039 (systematic) between 0.26 and 1.03 GeV/nucleon and 0.317 +/- 0.109(statistical) +/- 0.042(systematic) between 1.13 and 2.03 GeV/nucleon. This is the first measurement of its kind above l GeV/nucleon. ISOMAX results tend to be higher than predictions from current propagation models. In addition to the beryllium results, we report the isotopic ratios of neighboring lithium and boron in the energy range of the time-of-flight system (up to approx. 1 GeV/nucleon). The lithium and boron ratios agree well with existing data and model predictions at similar energies.

Hams, T.↗

NASA NTRS2009

Fermi (Formerly GLAST) at Six Months

The Fermi Gamma-ray Space Telescope, formerly called GLAST, is a mission to measure the cosmic gamma-ray flux in the energy range 20 MeV to more than 300 GeV, with supporting measurements for gamma-ray bursts from 8 keV to 30 MeV. In addition to breakthrough capabilities in energy coverage and localization, the very large field of view enables observations of 20% of the sky at any instant, and the entire sky on a timescale of a few hours. With its recent launch on 11 June 2008, Fermi now opens a new and important window on a wide variety of phenomena, including pulsars, black holes and active galactic nuclei, gamma-ray bursts, the origin of cosmic rays and supernova remnants, and searches for hypothetical new phenomena such as supersymmetric dark matter annihilations. In addition to early results and the science opportunities, this talk includes a description of the instruments and the mission status and plans.

Ritz, Steven M.↗

NASA NTRS2009

Fermi Mission Results, Status, and Plans

Ritz, Steven M.↗

NASA NTRS2009

Radiation Belt Storm Probe (RBSP) Mission

Scheduled to launch in May 2012, NASA's dual spacecraft Living With a Star Radiation Belt Storm Probe mission carries the field and particle instrumentation needed to determine the processes that produce enhancements in radiation belt ion and electron fluxes, the dominant mechanisms that cause the loss of relativistic electrons, and the manner by which the ring current and other geomagnetic phenomena affect radiation belt behavior. The two spacecraft will operate in low-inclination elliptical lapping orbits around the Earth, within and immediately exterior to the Van Allen radiation belts. During course of their two year primary mission, they will cover the full range of local times, measuring both AC and DC electric and magnetic fields to 10kHz, as well as ions from 50 eV to 1 GeV and electrons with energies ranging from 50 eV to 10 MeV.

Sibeck, D. G.↗

DOE OSTI2026

Low-energy ion beam sputtering of polycrystalline diamond

Ion beam milling is a highly versatile and precise technique for the microfabrication of diamond films, enabling controlled material removal at both micrometer and sub-micrometer scales while accommodating complex geometries and surface features. Comprehensive sputtering yield data are essential for process optimization. In this work, we systematically measure the sputter yield of polycrystalline diamond bombarded with $\textrm{N}_2^+$, Ne + , Ar + , Kr + , and Xe + ions over an energy range of 300–900 eV and beam incidence angles of 0°−80°, providing data critical for precision machining applications. Results show that the sputter yield increases with both ion energy and the incidence angle and decreases with increasing ion mass. For $\textrm{N}_2^+$ ions, the sputter yield is largely insensitive to ion energy and exceeds values expected for pure physical sputtering. The concurrent formation of volatile C 2 N 2 molecules during $\textrm{N}_2^+$ ion bombardment suggests that the process is dominated by chemical sputtering. The absence of a peak in the dependence of the sputter yield on the beam incidence angle expected at oblique incidence angles is attributed to the effects of surface roughness.

Materials science↗

NASA NTRS1981

Steady-state observations of geomagnetically trapped energetic heavy ions and their implications for theory

Data from the Heavy Ion Telescope on board Explorer 45 and the heavy ion channels on the ATS-6 spacecraft are used to describe the equatorial radial profiles of protons and He ions in the energy range of 0.1-1 MeV/nucleon. Measurements during a quiet period in June 1972 revealed that: fluxes of energetic protons and heavy ions inside L equals 4.5 are stable, with no observed decay; He ions of a given level are confined to the equatorial plane in a narrow L-range centered at Lmax; the equatorial differential flux ratio, compared on the basis of equal energy/ion, can exceed unity, indicating that He ion fluxes can be greater than equivalent energy proton fluxes; radial diffusion driven by variations of the magnetic field adequately models processes occurring in the inner magnetosphere for ion energies over 200 keV. The ATS-6 data from GEO found energetic heavy ions always present at L equals 6.6 and enhanced during magnetospheric substorms.

Fritz, T. A.↗

NASA NTRS1982

Upper limits to pulsed gamma ray emission from PSR 0833-45, 1747-46, and 1818-04

Pulsed gamma ray emission from three pulsars (PSR 0833-45, 1747-46, and 1818-04) have been sought on a balloon flight of the University of New Hampshire Large Gamma Ray Telescope, which incorporates a shielded sodium iodide scintillator array, and was launched from Alice Springs, Australia. Over the energy range 0.1 - 10 MeV, no evidence is found for pulsed gamma rays, and upper limits are set for Vela which are comparable to, or below, the extrapolation to lower energies of the pulsed emission reported by SAS-2 and COS-B.

Cherry, M. L.↗

NASA NTRS1983

Gamma ray detection with long NaI/Tl/ scintillator bars

Test measurements with a prototype NaI(Tl) scintillator for energy, position, and timing measurements in gamma ray astronomy are reported. The scintillator bar is 100 x 5 x 5 cu cm in size, and allows detection of the arrival times and pulse heights of signals from two photomultiplier tubes, one at each end of the bar. Data is gathered on the energy loss, linear position, and time-of-flight of gamma ray interactions within the bar over an energy range of 0.5-20 MeV. A mean attenuation coefficient of 0.015/cm has been determined, as have a FWHM resolution of 5 cm, 9.4%, and 10 nsec at an energy of 0.662 MeV. At 1.25 MeV the timing resolution was 6 nsec, and at 6.13 MeV the spatial resolution was 2.2 cm. The instrument is a prototype of a Compton scatter telescope being constructed for two balloon flights, one each in the Northern and Southern Hemispheres, in 1984.

Zych, A. D.↗

NASA NTRS1985

A measurement of the cosmic ray elements C to Fe in the two energy intervals 0.5-2.0 GeV/n and 20-60 GeV/n

The study of the cosmic ray abundances beyond 20 GeV/n provides additional information on the propagation and containment of the cosmic rays in the galaxy. Since the average amount of interstellar material traversed by cosmic rays decreases as its energy increases, the source composition undergoes less distortion in this higher energy region. However, data over a wide energy range is necessary to study propagation parameters. Some measurements of some of the primary cosmic ray abundance ratios at both low (near 2 GeV/n) and high (above 20 GeV/n) energy are given and compared to the predictions of the leaky box mode. In particular, the integrated values (above 23.7 GeV/n) for the more abundant cosmic ray elements in the interval C through Fe and the differential flux for carbon, oxygen, and the Ne, Mg, Si group are presented. Limited statistics prevented the inclusion of the odd Z elements.

Derrickson, J. H.↗

NASA NTRS1985

Single-Event Upset (SEU) model verification and threshold determination using heavy ions in a bipolar static RAM

Single-Event Upset (SEU) response of a bipolar low-power Schottky-diode-clamped TTL static RAM has been observed using Br ions in the 100-240 MeV energy range and O ions in the 20-100 MeV range. These data complete the experimental verification of circuit-simulation SEU modeling for this device. The threshold for onset of SEU has been observed by the variation of energy, ion species and angle of incidence. The results obtained from the computer circuit-simulation modeling and experimental model verification demonstrate a viable methodology for modeling SEU in bipolar integrated circuits.

Zoutendyk, J. A.↗

NASA NTRS1992

The AXAF CCD imaging spectrometer

The current status of the instrument design and the status of the CCDs being fabricated for the AXAF CCD Imaging Spectrometer (ACIS) are summarized. The instrument consists of an image recording array of CCDs and a linear arrangement of CCDs to record the spectra formed by the objective grating spectrometer. Both arrays employ CCDs with pixel dimensions which correspond to about 0.5 arcsec samples of the image. The CCDs provide moderate spectral resolution and good detection efficiency over the energy range 0.5 to 10 keV. Spectral resolution of 200 or more is achievable using the objective grating with the grating array. Radiation damage effects are shown to degrade the energy resolution of CCDs. Specially designed CCD pixel architecture is employed together with shielding and low temperature operation to slow the effects of radiation damage.

Garmire, G. P.↗

NASA NTRS1993

MeV ion-beam analysis of optical data storage films

Our objectives are threefold: (1) to accurately characterize optical data storage films by MeV ion-beam analysis (IBA) for ODSC collaborators; (2) to develop new and/or improved analysis techniques; and (3) to expand the capabilities of the IBA facility itself. Using H-1(+), He-4(+), and N-15(++) ion beams in the 1.5 MeV to 10 MeV energy range from a 5.5 MV Van de Graaff accelerator, film thickness (in atoms/sq cm), stoichiometry, impurity concentration profiles, and crystalline structure were determined by Rutherford backscattering (RBS), high-energy backscattering, channeling, nuclear reaction analysis (NRA) and proton induced X-ray emission (PIXE). Most of these techniques are discussed in detail in the ODSC Annual Report (February 17, 1987), p. 74. The PIXE technique is briefly discussed in the ODSC Annual Report (March 15, 1991), p. 23.

Leavitt, J. A.↗

NASA NTRS1994

Evidence of Circumstellar Matter Surrounding the Hercules X-1 System

We analyze data from two eclipse ingresses of Her X-1 observed with Ginga on 1989 April 30 and May 19. These observations occur, respectively, during the MAIN HIGH and SHORT HIGH states in the 35 day modulation of Her X-1 intensity. We find significant residual X-ray flux during eclipse, with a gradual decrease in flux following the occultation of the neutron star by the atmosphere of HZ Her. During the central part of the eclipse the count rate becomes nearly constant, at 0.5 mcrab in the energy range 1.7-36.8 keV. From a spec- tral analysis of the residual emission during the total eclipse of the central source in the MAIN MGH state, we determine the energy spectral index, alpha = 0.8, similar to that before eclipse. A remarkable feature of the eclipse spectrum is that it does not show a significant iron line feature in contrast to massive wind-fed pulsars, such as Vela X-1 and Cen X-3. From a timing analysis of the same eclipse data, we show that there are no pulses. These results imply that the emission comes from the scattering of continuum X-rays by material in a region considerably larger than the companion star. An extended accretion disk corona may be responsible for this scattering. However, partial eclipse of an extended accretion disk corona is insufficient to account for the count rates in mid-eclipse, when known parameters of the binary system are used. Based on the present results, we suggest that scattering occurs not only in the accretion disk corona but also in the circumstellar matter surrounding the system of Her X-1/HZ Her.

Choi, C. S.↗

NASA NTRS2002

Future Experiments in Astrophysics

The measurement methodologies of astrophysics experiments reflect the enormous variation of the astrophysical radiation itself. The diverse nature of the astrophysical radiation, e.g. cosmic rays, electromagnetic radiation, and neutrinos, is further complicated by the enormous span in energy, from the 1.95 Kappa relic neutrino background to cosmic rays with energy greater than 10(exp 20)eV. The measurement of gravity waves and search for dark matter constituents are also of astrophysical interest. Thus, the experimental techniques employed to determine the energy of the incident particles are strongly dependent upon the specific particles and energy range to be measured. This paper summarizes some of the calorimetric methodologies and measurements planned by future astrophysics experiments. A focus will be placed on the measurement of higher energy astrophysical radiation. Specifically, future cosmic ray, gamma ray, and neutrino experiments will be discussed.

Krizmanic, John F.↗

DOE OSTI2023

Impact of High Energy νe (ν¯e) Events on NOvA Oscillation Sensitivities

NOvA is a two detector, long-baseline neutrino oscillation experiment located at Fermilab, Batavia, IL, USA. It is primarily designed to constraint neutrino oscillation parameters using muon neutrino (anti-neutrino) disappearance data and electron neutrino (anti-neutrino) appearance data. NOvA detects neutrinos from Fermilab’s Neutrinos at Main Injector (NuMI) beam-line. The un-oscillated muon neutrino and beam $\nu_e$ events are observed by the NOvA Near Detector (ND), which is 100m underground and at a distance of 1km from the beam source. The Far Detector (FD), situated 809 km away from the ND, is in Ash River, MN, USA, and observes $\nu_\mu$ and $\nu_e$ events after oscillations. Traditionally, NOvA has used $\nu_e$ events in the energy range 1 < E < 4 GeV for 3-flavor neutrino oscillation analyses to constraint the neutrino oscillation parameters. In this study we looked at the impact of including high-energy neutrino events with energies up to 12 GeV in the analysis with the aim of constraining the beam electron neutrino/antineutrino background events. Event count predictions after adding this high-energy sample events and latest three flavor oscillation results of the NOvA experiment are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗