Discrete extrasolar X-ray sources.
Galactic X ray sources observed in EM spectrum high energy region, discussing hot plasma cloud thermal radiation and electrons synchrotron radiation as emission sources
Rossi, B. B.↗
SEARCH · Engineering Papers
Results for “Radiation and Electronics”
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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Polarization reversal of solar microwave bursts
Solar microwave bursts polarization reversal mechanism, considering radiating electrons gyrosynchrotron absorption
Holt, S. S.↗
Solar active regions at millimeter wavelengths
Solar active regions at millimeter wavelengths, discussing brightness temperature, background radiation, electron density, optical thickness, polarization and chromospheric magnetic fields
Kundu, M. R.↗
Stark broadening of H-beta, H-gamma, and H-delta - A comparison of theory and experiment
H beta, H gamma and H delta Stark broadened profiles, investigating perturbing electron- radiating atom inelastic collisions, Gaunt factors and half widths
Gerardo, J. B.↗
The electron diffusion coefficient in Jupiter's magnetosphere
A steady-state model of Jupiter's electron radiation belt is developed. The model includes injection from the solar wind, radial diffusion, energy degradation by synchrotron radiation, and absorption at Jupiter's surface. A diffusion coefficient of the form D sub RR/R sub J squared = k times R to the m-th power is assumed, and then observed data on synchrotron radiation are used to fit the model. The free parameters determined from this fit are m = 1.95 plus or minus 0.5, k = 1.7 plus or minus 0.5 x 10 to the 9th power per sec, and the magnetic moment of injected particles equals 770 plus or minus 300 MeV/G. The value of m shows quite clearly that the diffusion is not caused by magnetic pumping by a variable solar wind or by a fluctuating convection electric field. The process might be field line exchange driven by atmospheric-ionospheric winds; our diffusion coefficient has roughly the same radial dependence but is considerably smaller in magnitude than the upper bound diffusion coefficients recently suggested for this process by Brice and McDonough (1973) and Jacques and Davis (1972).
Birmingham, T.↗
Thin silicon solar cell performance characteristics
Refined techniques for surface texturizing, back surface field and back surface reflector formation were evaluated for use with shallow junction, single-crystal silicon solar cells. Each process was characterized individually and collectively as a function of device thickness and bulk resistivity. Among the variables measured and reported are open circuit voltage, short circuit current and spectral response. Substantial improvements were obtained by the utilization of a low cost aluminum paste process to simultaneously remove the unwanted n(+) diffused region, form the back surface field and produce an ohmic contact metallization. The highly effective BSF which results from applying this process has allowed fabrication of cells 0.05 mm thick with initial outputs as high as 79.5 mW/4 sq cm (28 C, AM0) and superior electron radiation tolerance. Cells of 0.02 mm to 0.04 mm thickness have been fabricated with power to mass ratios well in excess of 2 watts per gram.
Gay, C. F.↗
Short circuit current changes in electron irradiated GaAlAs/GaAs solar cells
Heteroface p-GaAlAs/p-GaAs/n-GaAs solar cells with junction depths of 0.8, 1.5, and 4 microns were irradiated with 1 MeV electrons. The short-circuit current for the 4 micron junction depth cells is significantly reduced by the electron irradiation. Reduction of the junction depth to 1.5 microns improves the electron radiation resistance of the cells while further reduction of the junction depth to 0.8 microns improves the stability of the cells even more. Primary degradation is in the blue region of the spectrum. Considerable recovery of lost response is obtained by annealing the cells at 200 C. Computer modeling shows that the degradation is caused primarily by a reduction in the minority carrier diffusion length in the p-GaAs.
Walker, G. H.↗
Ultraviolet lasers. Citations from the International Aerospace Abstracts data base
Reports cited from the international literature describe various aspects of ultraviolet lasers including laser output, far ultraviolet radiation, electron pumping, optical pumping, and laser materials. Gas lasers, pulsed lasers, dye lasers, CO2 lasers, xenon fluoride lasers, and transversely excited atmospheric (TEA) lasers are considered. This updated bibliography contains 283 citations, 66 of which are new additions to the previous edition.
Mauk, S. C.↗
GaAs homojunction solar cell development
The Lincoln Laboratory n(+)/p/p(+) GaAs shallow homojunction cell structure was successfully demonstrated on 2 by 2 cm GaAs substrates. Air mass zero efficiencies of the seven cells produced to date range from 13.6 to 15.6 percent. Current voltage (I-V) characteristics, spectral response, and measurements were made on all seven cells. Preliminary analysis of 1 MeV electron radiation damage data indicate excellent radiation resistance for these cells.
Flood, D. J.↗
Evaluation of solar cell covers and encapsulant materials for space application
The effects of space radiation (electrons and protons), vacuum, and thermal cycling on a variety of solar cell covers are investigated. Cover materials evaluated include glass resins, 2 mil glass applied with adhesives or electrostatically bonded, and thin plastic films of FEP or PFA applied with adhesive. Solar cells were exposed to environmental conditions simulating those encountered in outer space. These test conditions include 1 MeV electrons, 0.5 MeV protons, and thermal cycling in vacuum. During testing the solar cells were monitored for variations in electrical characteristics and structural changes.
Russell, D. A.↗
Large area, low cost space solar cells with optional wraparound contacts
Design parameters for two large area, low cost solar cells are presented, and electron irradiation testing, thermal alpha testing, and cell processing are discussed. The devices are a 2 ohm-cm base resistivity silicon cell with an evaporated aluminum reflector produced in a dielectric wraparound cell, and a 10 ohm-cm silicon cell with the BSF/BSR combination and a conventional contact system. Both cells are 5.9 x 5.9 cm and require 200 micron thick silicon material due to mission weight constraints. Normalized values for open circuit voltage, short circuit current, and maximum power calculations derived from electron radiation testing are given. In addition, thermal alpha testing values of absorptivity and emittance are included. A pilot cell processing run produced cells averaging 14.4% efficiencies at AMO 28 C. Manufacturing for such cells will be on a mechanized process line, and the area of coverslide application technology must be considered in order to achieve cost effective production.
Michaels, D.↗
Variability of compact radio sources at a wavelength of 1 millimeter
Broad-band 1 mm continuum observations of 3C 273, 3C 279, BL Lac, 3C 84, OJ 287, and 3C 345 made between 1977 March and 1981 January are reported. With the possible exception of 3C 279, all of the objects exhibited evidence for variability in the 1 mm flux density on the time scale of a few months. Flux variations at wavelengths of 1 mm and 2 cm are well correlated for the 'blazars' (BL Lac objects and optically violent variable quasars) observed; emission outbursts occur simultaneously and have similar amplitude at the two wavelengths. In contrast, an outburst in the flux from the Seyfert galaxy 3C 84 was observed at a wavelength of 1 mm in early 1980 but has not appeared at 2 cm as of 1 yr later. The observed relationship between 'blazar' emission variability at 1 mm and 2 cm is inconsistent with the canonical expanding-source model of radio variability or any of its modifications. Instead, models in which the number of synchrotron-radiating electrons is time variable (due to particle injection or acceleration behind a relativistic shock) are required.
Ennis, D. J.↗
Extragalactic 1 millimeter sources - Simultaneous observations at centimeter, millimeter, and visual wavelengths
Observations simultaneously made at visual (B, V, and R) wavelengths, at 1, 1.4, and 3.4 mm and at 1.3, 2, 6, and 20 cm of 9 QSOs and BL Lac objects are reported. The range of the millimeter-visual spectral index alpha sub mv was only 0.65-0.82, typical of optically thin synchrotron emission. This may indicate that the electrons radiating synchrotron emission in this portion of the spectrum are not subjected to large radiation losses, and therefore relativistic bulk motion with Doppler factors of about 10 are required. The visual spectral index is much more broadly distributed and typically larger than alpha sub mv. The spectral energy distributions have not changed much in the last two to five years except for 2251+15 and perhaps 0235+164. Only 1749+09 shows a sharp spectral break shortward of 1 mm. Sixteen other sources were observed at 1 mm, of which seven were detected.
Landau, R.↗
The central engine of quasars and AGNs: A relativistic proton radiative shock
Active galactic nuclei (AGNs) and quasars (QSOs) appear to emit roughly equal energy per decade from radio to gamma-ray energies (e.g. Ramaty and Ligenfelter 1982). This argues strongly for a nonthermal radiation mechanism (see Rees 1984). In addition, statistical studies have indicated that the spectra of these objects in the IR-UV and 2 to 50 keV X-ray band, can be fitted very well with power laws of specific indices. These spectral indices do not seem to depend on the luminosity or morphology of the objects (Rothschild et al. 1983; Malkan 1984), and any theory should account for them in a basic and model independent way. If shocks accelerate relativistic protons via the first-order Fermi mechanism (e.g. Axfor 1981), the radiating electrons can be produced as secondaries throughout the source by proton-proton (p-p) collisions and pion decay, thus eliminating Compton losses (Protheroe and Kazanas 1983). As shown by Kazanas (1984), if relativistic electrons are injected at high energies, e+-e- pair production results in a steady state electron distribution that is very similar to that observed in AGNs, independent of the details of injection and the dynamics of the source. The conditions required by this mechanism are met in the shock model of Eichler (1984) and Ellison and Eichler (1984) which allows the self-consistent calculation of the shock acceleration efficiency.
Kazanas, D.↗
Studies of molecular properties of polymeric materials: Aerospace environmental effects on three linear polymers
The development of crystal handling techniques for reflection infrared spectroscopy and methods for the fabrication and testing of tensile specimens are discussed. Data from mechanical, ac and dc electrical, and electron paramagnetic resonance studies conducted to determine the effects of 0.1-MeV and 1.0-MeV electron radiation on Mylar, Kapton, Ultem, and metal-doped Ultem are presented. Total doses ranging from 1 X 10 to the 8 rads to 1 X 10 to the 10 rads and dose rates from 5 X 10 to the 7 rads/hr to 1 X 10 to the 9 rads/hr were employed. The results of a study on the effects of aircraft service-environment fluids on Ultem are also reported. The weights and mechanical properties of Ultem were evaluated before and after exposure to water, JP4, Skydrol, an antifreeze, and a paint stripper.
Harries, W. L.↗
Solar gradual hard X-ray bursts and associated phenomena
White-light coronagraph, H-alpha and radio data are presented as well as hard X-ray data for a sample of 10 gradual hard X-ray bursts (GHBs) in an attempt to better understand the nature of these events. It is found that: (1) the hard X-ray photon energy spectrum began to harden near the onset of the GHBs and continued in this fashion during the decay phase; (2) a coronal mass ejection (CME) occurred in association with at least nine of the GHBs; (3) the GHBs occurred in the late phase of major flares; (4) the centimeter wavelength bursts associated with the GHBs had relatively low frequency spectral maxima, and in relation to the observed hard X-ray emission, they were microwave-rich; (5) the associated decimetric bursts showed significant intensity variations on time scales ranging from 0.1 to approximately greater than 1 minute; and (6) the GHBs were most strongly associated with type IV events. It is concluded that the acceleration and trapping of radiating electrons occurs in the postflare loop systems following CMEs.
Cliver, E. W.↗
Space environmental effects on graphite-epoxy compressive properties and epoxy tensile properties
This study characterizes the effects of electron radiation and temperature on a graphite-epoxy composite material. Compressive properties of the T300/934 material system were obtained at -250 F (-157 C), room temperature, and 250 F (121 C). Tensile specimens of the Fiberite 934 epoxy resin were fabricated and tested at room temperature and 250 F (121 C). Testing was conducted in the baseline (nonirradiated) and irradiated conditions. The radiation exposure was designed to simulate 30 year, worst-case exposure in geosynchronous Earth orbit. Mechanical properties tended to degrade at elevated temperature and improve at cryogenic temperature. Irradiation generally degraded properties at all temperatures.
Fox, Derek J.↗
Design study of large area 8 cm x 8 cm wrapthrough cells for space station
The design of large area silicon solar cells for the projected NASA space station is discussed. It is based on the NASA specification for the cells which calls for an 8 cm by 8 cm cell of wrapthrough type with gridded back contacts. The beginning of life (BOL) power must be 1.039 watts per cell or larger and maximum end of life (EOL) after 10 years in the prescribed orbit under an equivalent 1MeV electron radiation damage fluence of 5 times 10 to the 13th power e/square cm. On orbit efficiency is to be optimized by a low thermal absorptance goal (thermal alpha) of .63.
Garlick, George F. J.↗