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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 55 records · Page 3
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NASA NTRS1990

Single nucleon emission in relativistic nucleus-nucleus reactions

Significant discrepancies between theory and experiment have previously been noted for nucleon emission via electromagnetic processes in relativistic nucleus-nucleus collisions. The present work investigates the hypothesis that these discrepancies have arisen due to uncertainties about how to deduce the experimental electromagnetic cross section from the total measured cross section. An optical-model calculation of single neutron removal is added to electromagnetic cross sections and compared to the total experimental cross sections. Good agreement is found thereby resolving some of the earlier noted discrepancies. A detailed comparison to the recent work of Benesh, Cook, and Vary is made for both the impact parameter and the nuclear cross section. Good agreement is obtained giving an independent confirmation of the parametrized formulas developed by those authors.

NASA Discipline Radiation Health↗
NASA NTRS2007

The Electron Calorimeter (ECAL) Long Duration Balloon Experiment

Accurate measurements of the cosmic ray electron energy spectrum in the energy region 50 GeV to greater than 1 TeV may reveal structure caused by the annihilation of exotic dark matter particles and/or individual cosmic ray sources. Here we describe a new long duration balloon (LDB) experiment, ECAL, optimized to directly measure cosmic ray electrons up to several TeV. ECAL includes a double layer silicon matrix, a scintillating optical fiber track imager, a neutron detector and a fully active calorimeter to identify more than 90% of the incident electrons with an energy resolution of about 1.7% while misidentifying only 1 in 200,000 protons and 0.8% of secondary gamma rays as electrons. Two ECAL flights in Antarctica are planned for a total exposure of 50 days with the first flight anticipate for December 2009.

Guzik, T. G.↗
NASA NTRS1991

Target correlation effects on neutron-nucleus total, absorption, and abrasion cross sections

Second order optical model solutions to the elastic scattering amplitude were used to evaluate total, absorption, and abrasion cross sections for neutron nucleus scattering. Improved agreement with experimental data for total and absorption cross sections is found when compared with first order (coherent approximation) solutions, especially below several hundred MeV. At higher energies, the first and second order solutions are similar. There are also large differences in abrasion cross section calculations; these differences indicate a crucial role for cluster knockout in the abrasion step.

Cucinotta, Francis A.↗
NASA NTRS1988

The Geminga X-ray counterpart and a blue optical identification

Based on optical photometry, the identification of the X-ray source 1E 0630+178 with a blue object inside the Einstein error circle is reported. The question of whether the X-rays could be thermal emission from the surface of a neutron star is addressed. The new optical data confirm that relative fluxes in the optical, X-ray, and gamma-ray bands closely match those of the Vela pulsar. The Vela pulsar is adopted as an 'observational model' for Geminga, whereby only the lack of radio emission from Geminga remains to be accounted for. Previous observational results and theoretical models for Geminga are reviewed in light of the new findings.

Halpern, J. P.↗
NASA NTRS2003

Transparent Metal-Salt-Filled Polymeric Radiation Shields

"COR-RA" (colorless atomic oxygen resistant -- radiation shield) is the name of a transparent polymeric material filled with x-ray-absorbing salts of lead, bismuth, cesium, and thorium. COR-RA is suitable for use in shielding personnel against bremsstrahlung radiation from electron-beam welding and industrial and medical x-ray equipment. In comparison with lead-foil and leaded-glass shields that give equivalent protection against x-rays (see table), COR-RA shields are mechanically more durable. COR-RA absorbs not only x-rays but also neutrons and rays without adverse effects on optical or mechanical performance. The formulation of COR-RA with the most favorable mechanical-durability and optical properties contains 22 weight percent of bismuth to absorb x-rays, plus 45 atomic percent hydrogen for shielding against neutrons.

Edwards, David↗
NASA NTRS1997

Broadband High-Energy Observations of the Superluminal Jet Source GRO J1655-40 During an Outburst

The X-ray/radio transient superluminal jet source GRO J1655-40 was recently suggested to contain a black hole from optical observations. Because it is a relatively close-by system (d approximately 3.2 kpc), it can likely provide us with rich information about the physics operating in both Galactic and extragalactic jet sources. We present the first simultaneous broadband high-energy observations of GRO J1655-40 during the 1995 July-August outburst by three instruments: ASCA, WATCH/Granat, and BATSE/CGRO, in the energy band from 1 keV to 2 MeV. Our observations strengthen the interpretation that GRO J1655-40 contains a black hole. We detected a two-component energy spectrum, commonly seen from other Galactic black hole binaries, but never detected from a neutron star system. Combining our results with the mass limits derived from optical radial velocity and orbital period measurements, we further constrain the mass of the central object to be between 3.3 and 5.8 solar mass, above the well-established mass upper limit of 3.2 solar mass for a neutron star (the optical mass function for GRO J1655-40 is 3.16 + 0.2 solar mass). This system is therefore the first Galactic superluminal jet source for which there is strong evidence that the system contains a stellar mass black hole. The inclination angle of the binary system is constrained to be between 76 deg and 87 deg, consistent with estimates obtained from optical light curves and radio jet kinematics.

Zhang, S. N.↗
NASA NTRS2011

NASA Tech Briefs, October 2011

Topics covered include: Laser Truss Sensor for Segmented Telescope Phasing; Qualifications of Bonding Process of Temperature Sensors to Deep-Space Missions; Optical Sensors for Monitoring Gamma and Neutron Radiation; Compliant Tactile Sensors; Cytometer on a Chip; Measuring Input Thresholds on an Existing Board; Scanning and Defocusing Properties of Microstrip Reflectarray Antennas; Cable Tester Box; Programmable Oscillator; Fault-Tolerant, Radiation-Hard DSP; Sub-Shot Noise Power Source for Microelectronics; Asynchronous Message Service Reference Implementation; Zero-Copy Objects System; Delay and Disruption Tolerant Networking MACHETE Model; Contact Graph Routing; Parallel Eclipse Project Checkout; Technique for Configuring an Actively Cooled Thermal Shield in a Flight System; Use of Additives to Improve Performance of Methyl Butyrate-Based Lithium-Ion Electrolytes; Li-Ion Cells Employing Electrolytes with Methyl Propionate and Ethyl Butyrate Co-Solvents; Improved Devices for Collecting Sweat for Chemical Analysis; Tissue Photolithography; Method for Impeding Degradation of Porous Silicon Structures; External Cooling Coupled to Reduced Extremity Pressure Device; A Zero-Gravity Cup for Drinking Beverages in Microgravity; Co-Flow Hollow Cathode Technology; Programmable Aperture with MEMS Microshutter Arrays; Polished Panel Optical Receiver for Simultaneous RF/Optical Telemetry with Large DSN Antennas; Adaptive System Modeling for Spacecraft Simulation; Lidar-Based Navigation Algorithm for Safe Lunar Landing; Tracking Object Existence From an Autonomous Patrol Vehicle; Rad-Hard, Miniaturized, Scalable, High-Voltage Switching Module for Power Applications; and Architecture for a 1-GHz Digital RADAR.

Source record↗
NASA NTRS1988

Igneous history of the aubrite parent asteroid - Evidence from the Norton County enstatite achondrite

Numerous specimens of the Norton County enstatite achondrite (aubrite) were studied by optical microscopy, electron microprobe, and neutron-activation analysis. Norton County is found to be a fragmental impact breccia, consisting of a clastic matrix made mostly of crushed enstatite, into which are embedded a variety of mineral and lithic clasts of both igneous and impact melt origin. The Norton County precursor materials were igneous rocks, mostly plutonic orthopyroxenites, not grains formed by condensation from the solar nebula. The Mg-silicate-rich aubrite parent body experienced extensive melting and igneous differentiation, causing formation of diverse lithologies including dunites, plutonic orthopyroxenites, plutonic pyroxenites, and plagioclase-silica rocks. The presence of impact melt breccias (the microporphyritic clasts and the diopside-plagioclase-silica clast) of still different compositions further attests to the lithologic diversity of the aubrite parent body.

Okada, Akihiko↗
NASA NTRS1997

Evidence for a New Class of Extreme Ultraviolet Sources

Most of the sources detected in the extreme ultraviolet (EUV; 100-600 A) by the ROSAT/WFC and EUVE all-sky surveys have been identified with active late-type stars and hot white dwarfs that are near enough to the Earth to escape absorption by interstellar gas. However, about 15 per cent of EUV sources are as yet unidentified with any optical counterparts. We examine whether the unidentified EUV sources may consist of the same population of late-type stars and white dwarfs. We present B and R photometry of stars in the fields of seven of the unidentified EUV sources. We detect in the optical the entire main-sequence and white dwarf population out to the greatest distances where they could still avoid absorption. We use color-magnitude diagrams to demonstrate that, in most of the fields, none of the observed stars has the colours and magnitudes of late-type dwarfs at distances less than 100 pc. Similarly, none of the observed stars is a white dwarf within 500 pc that is hot enough to be a EUV emitter. The unidentified EUV sources we study are not detected in X-rays, while cataclysmic variables, X-ray binaries, and active galactic nuclei generally are. We conclude that some of the EUV sources may be a new class of nearby objects, which are either very faint at optical bands or which mimic the colours and magnitudes of distant late-type stars or cool white dwarfs. One candidate for optically faint objects is isolated old neutron stars, slowly accreting interstellar matter. Such neutron stars are expected to be abundant in the Galaxy, and have not been unambiguously detected.

Maoz, Dan↗
NASA NTRS2003

Uncovering The Properties of Young Neutron Stars and Their Surrounding Supernova A Remnants

In the third year of this program, the following studies have been undertaken in support of this effort: G292.0+1.8: In our previous work on this SNR, we discovered a young neutron star and its associated pulsar wind nebula. Radio observations by Camilo et al. (2002) have identified a young 136 ms pulsar in the direction of G292.0+1.8. We have used Chandra HRC observations of the central source to identify X-ray pulsations at the same period, thus establishing the neutron star as the radio pulsar counterpart. We have also set limits on the cooling of this young neutron star based on the unpulsed component of the X-ray emission. We find that the limit falls slightly below standard cooling models in which the modified Urca process is responsible for the bulk of the interior neutrino emission. A paper summarizing these results is currently being circulated amongst co-authors for review prior to publication. 3c 58: Our Chandra observations of this Crab-like SNR revealed the presence of a young, rapidly rotating pulsar as well as a central compact nebula which we interpret as a toroidal structure associated with the pulsar wind termination shock. Our modeling of this structure has allowed us to establish a temperature upper limit for the neutron star which falls well below predictions from standard cooling models, and implies the presence of exotic particles (such as pion condensates) or other processes that increase the neutrino production rate in the interior. A paper summarizing this work has been published in the Astrophysical Journal (Slane, Helfand, & Murray 2002, ApJ, 571, L45), and the results were the subject of a NASA Space Science Update (4/10/2002) which led to extensive media coverage. Based upon our initial observations, we submitted a successful Chandra Large Project proposal for a 350 ks observation of this young neutron star and its wind nebula. Kes 79: Our Chandra observations of this SNR reveal a compact central source which appears to be the neutron star formed in the explosion that produced the remnant. There is no evidence for a surrounding pulsar wind nebula. The source properties are similar to the central source in Cas A even though the Kes 79 remnant is considerably older. The results have been published in the Astrophysical Journal (Seward, Slane, Smith, and Sun 2003, ApJ, 584,414). Chandra Survey for Compact Objects in Supernova Remnants: We have formed a collaboration to carry out an extensive search for young neutron stars in nearby supernova remnants. Using X-ray observations from an approved Chandra Large Project, as well as from additional approved XMM observations, we are investigating a volume-limited sample of SNRs for which there is currently no evidence of associated neutron stars. We have obtained extensive optical and 1R data to complement the project, and analysis of these data is currently underway.

Slane, Patrick O.↗
NASA NTRS2006

Rotational-translational fourier imaging system requiring only one grid pair

The sky contains many active sources that emit X-rays, gamma rays, and neutrons. Unfortunately hard X-rays, gamma rays, and neutrons cannot be imaged by conventional optics. This obstacle led to the development of Fourier imaging systems. In early approaches, multiple grid pairs were necessary in order to create rudimentary Fourier imaging systems. At least one set of grid pairs was required to provide multiple real components of a Fourier derived image, and another set was required to provide multiple imaginary components of the image. It has long been recognized that the expense associated with the physical production of the numerous grid pairs required for Fourier imaging was a drawback. Herein one grid pair (two grids), with accompanying rotation and translation, can be used if one grid has one more slit than the other grid, and if the detector is modified.

Campbell, Jonathan W.↗
NASA NTRS2015

Multifunctional Electroactive Nanocomposites Based on Piezoelectric Boron Nitride Nanotubes

Space exploration missions require sensors and devices capable of stable operation in harsh environments such as those that include high thermal fluctuation, atomic oxygen, and high-energy ionizing radiation. However, conventional or state-of-the-art electroactive materials like lead zirconate titanate, poly(vinylidene fluoride), and carbon nanotube (CNT)-doped polyimides have limitations on use in those extreme applications. Theoretical studies have shown that boron nitride nanotubes (BNNTs) have strength-to-weight ratios comparable to those of CNTs, excellent high-temperature stability (to 800 C in air), large electroactive characteristics, and excellent neutron radiation shielding capability. In this study, we demonstrated the experimental electroactive characteristics of BNNTs in novel multifunctional electroactive nanocomposites. Upon application of an external electric field, the 2 wt % BNNT/polyimide composite was found to exhibit electroactive strain composed of a superposition of linear piezoelectric and nonlinear electrostrictive components. When the BNNTs were aligned by stretching the 2 wt % BNNT/polyimide composite, electroactive characteristics increased by about 460% compared to the nonstretched sample. An all-nanotube actuator consisting of a BNNT buckypaper layer between two single-walled carbon nanotube buck-paper electrode layers was found to have much larger electroactive properties. The additional neutron radiation shielding properties and ultraviolet/visible/near-infrared optical properties of the BNNT composites make them excellent candidates for use in the extreme environments of space missions. utilizing the unique characteristics of BNNTs.

Kang, Jin Ho↗
NASA NTRS1985

Low-mass X-ray binaries

A review is given of current understanding of low-mass X-ray binaries (LMXBs), which are luminous X-ray sources composed of a late-type optical companion (mass less than about 1 solar mass) and a neutron star (or possibly a black hole). Thirty-two LMXBs have been identified with optical counterparts in the Galaxy and one in the Large Magellanic Cloud (Brad and McClintock, 1983). It is unlikely that there are more than about 100 active LMXBs in the Galaxy, compared with about 200,000 cataclysmic variables. Topics covered in the review are: typical X-ray and optical properties; orbital periods; the nature of the compact source; accretion disks; formation; mass transfer mechanisms; and globular clusters and bright bulge X-ray sources.

Mcclintock, J. E.↗
NASA NTRS1992

Gamma-ray bursts and cosmic rays from accretion-induced collapse

It is shown that the birth of naked or nearly naked neutron stars in accretion-induced collapse or in the bare collapse of white dwarfs can produce cosmological gamma-ray bursts and can provide the required injection rate of cosmic rays into the interstellar space. It is estimated that most of the e(+)e(-) pairs annihilate in flight on a short time scale in the vicinity of the neutron star. It is shown that the gamma-ray bursts, the 0.511 MeV Galactic annihilation radiation, and the cosmic rays exclude the possibility that the large uncertainties in the Galactic pulsar birthrate and the Galactic SN II explosion rate would allow a significant contribution to the pulsar birthrate from naked or nearly naked neutron star formation. The upper bound on the Galactic birthrate of naked or nearly naked neutron stars of less than 1 in 1000 yr makes it very unlikely that a neutrino burst unaccompanied by optical emission from the birth of a naked or nearly naked neutron star will be detected in the near future by underground neutrino telescopes.

Dar, Arnon↗
NASA NTRS1989

Physics of systems containing neutron stars

The following is a summary of work done during the period of Mar. to Oct. 1989. Three major topics were extensively looked into during this time: the reported 2,000 Hz optical signal from the direction of SNR1987A, the possibility that neutron stellar surface magnetic fields do not decay except when the star is accreting, and the 6 Hz QPOs of LMXBs.

Shaham, Jacob↗
NASA NTRS1982

Gamma-ray astronomy

Cosmic gamma rays, the physical processes responsible for their production and the astrophysical sites from which they were seen are reported. The bulk of the observed gamma ray emission is in the photon energy range from about 0.1 MeV to 1 GeV, where observations are carried out above the atmosphere. There are also, however, gamma ray observations at higher energies obtained by detecting the Cerenkov light produced by the high energy photons in the atmosphere. Gamma ray emission was observed from sources as close as the Sun and the Moon and as distant as the quasar 3C273, as well as from various other galactic and extragalactic sites. The radiation processes also range from the well understood, e.g. energetic particle interactions with matter, to the still incompletely researched, such as radiation transfer in optically thick electron positron plasmas in intense neutron star magnetic fields.

Ramaty, R.↗
NASA NTRS1980

Simultaneous X-ray and optical observations of the 7.7 second X-ray pulsar 4U 1626-67

Simultaneous X-ray and optical observations of the 7.7-s X-ray pulsar 4U 1626-67, obtained during May 29-31, 1978, reveal the presence of (1) intense, correlated optical and X-ray flares and (2) 7.7-s optical pulsations which agree in phase with the 1-3 keV X-ray pulsations to within 0.5 s (two standard deviations) and which agree in period to within 0.001 s (one standard deviation). From these data it is concluded that a substantial fraction (a minimum of 8%) and possibly all of the optical emission is produced from within approximately 0.5 light sec or 1.5 x 10 to the 10th cm of the neutron star. Furthermore, the data rule out the possibility that this optical emission comes from the X-ray heated surface of a degenerate or nondegenerate dwarf companion. It most likely comes from an accretion disk.

Mcclintock, J. E.↗
NASA NTRS1979

Initial conceptual design study of self-critical nuclear pumped laser systems

An analytical study of self-critical nuclear pumped laser system concepts was performed. Primary emphasis was placed on reactor concepts employing gaseous uranium hexafluoride (UF6) as the fissionable material. Relationships were developed between the key reactor design parameters including reactor power level, critical mass, neutron flux level, reactor size, operating pressure, and UF6 optical properties. The results were used to select a reference conceptual laser system configuration. In the reference configuration, the 3.2 m cubed lasing volume is surrounded by a graphite internal moderator and a region of heavy water. Results of neutronics calculations yield a critical mass of 4.9 U(235) in the form (235)UF6. The configuration appears capable of operating in a continuous steady-state mode. The average gas temperature in the core is 600 K and the UF6 partial pressure within the lasing volume is 0.34 atm.

Rodgers, R. J.↗