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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

The soft X-ray spectrum of Sirius B - Evidence for the photospheric hypothesis

The soft X-ray spectrum of Sirius obtained by the HEAO 1 A-2 experiment is used to investigate the origin of the X-radiation from that system. It is shown that, if the emission is coronal, then the coronal temperature must be less than 150,000 K, and the coronal luminosity must be greater than 10 to the 33rd ergs/s. Such a corona conflicts severely with EUV observations and is physically untenable. White dwarf atmosphere models are fitted to the spectrum and it is shown that a photospheric temperature of 28,000 K is much more consistent with the data. The relative consistency of the soft X-ray, EUV, and UV observations of Sirius B is discussed and it is concluded that the evidence favors the white dwarf photosphere as the origin of the soft X-rays.

Martin, C.↗
NASA NTRS1964

The X-Irradiation of Hydrazine and 1,1- Dimethylhydrazine

Hydrazine and 1,1-dimethylhydrazine were radiolyzed at room temperature by using about 1 gram of liquid or 1/2 to 2 liters of vapor at room-temperature vapor pressure. A tungsten-target X-ray source operating at 300 kilovolts and 6 to 8 milliamperes (0.1 to 1.0 A) was used at intensities of 1 times 10 (sup 2) to 1 times 10 (sup 3) roentgens per minute to give total doses of 4.1 rads to 2.3 times 10 (sup 6) rads. The amounts of decomposition were dependent on total dose and independent of dose rate. In the case of hydrazine vapor, the decomposition was also directly related to surface area. There was a lesser surface effect with liquid hydrazine, but this variable was not studied for 1,1-dimethylhydrazine. The order of decreasing sensitivity to X-radiation is as follows: hydrazine vapor, 1,1-dimethylhydrazine vapor, 1,1-dimethylhydrazine liquid, and hydrazine liquid. The decomposition products of hydrazine were nitrogen, hydrogen, ammonia, and unidentified products. The same products plus methylamine, dimethylamine, and hydrazine were found from the decomposition of 1,1-dimethylhydrazine. In addition, the 1,1-dimethylhydrazine underwent post-irradiation changes. Values for G (number of molecules of sample decomposed per 100 electronvolts of absorbed energy) of the order of 10 (sup 6) suggest that the vapor-phase decompositions are chain reactions.

X-RAY IRRADIATION↗
NASA NTRS1989

Dynamical diffraction imaging (topography) with X-ray synchrotron radiation

By contrast to electron microscopy, which yields information on the location of features in small regions of materials, X-ray diffraction imaging can portray minute deviations from perfect crystalline order over larger areas. Synchrotron radiation-based X-ray optics technology uses a highly parallel incident beam to eliminate ambiguities in the interpretation of image details; scattering phenomena previously unobserved are now readily detected. Synchrotron diffraction imaging renders high-resolution, real-time, in situ observations of materials under pertinent environmental conditions possible.

Kuriyama, M.↗
NASA NTRS1964

On the x-ray emission in the aurora zones

The X-radiation, occurring in the aurora zone, was first revealed in the summer of 1952 [1,2] rockets above 50 km. This radiation is mainly concentrated between the 62 and 77° geomagnetic latitude, with a maximum near 67.5°. It is generated at fast electron collisions with upper atmosphere particles.

PLANET↗
NASA NTRS1970

Production of gamma rays in the crab nebula pulsar

The gamma-ray flux at energies above 50 MeV from NP0532 is evaluated for a pulsar model in which the optical and X-radiation is produced by synchrotron effect. Synchrotron radiation and inverse Compton scattering are considered as production mechanisms of the gamma-rays. The theoretical estimates are compared with the experimental values.

Treves, A.↗
NASA NTRS1971

RBE for late somatic effects in mice irradiated with 60 MeV protons relative to X-rays.

Investigation of the relative biological effectiveness of energetic protons for the induction of somatic effects in a mammal (mice) following whole body irradiation. The proton energy used approximates the mean energy for proton spectra accompanying solar events. The effects on longevity and the incidence of major neoplastic diseases are summarized. The results obtained suggest that medium energy proton irradiation is no more effective, and on the whole, probably less effective, than conventional X radiation for the induction of late radiation effects in the mouse.

Darden, E. B., Jr.↗
NASA NTRS1971

Erythropoietic radiosensitivity of the rat during altitude acclimatization.

The effect of a sublethal dose (300 R) of X-radiation upon the erythropoietic system of the rat, during 60-day acclimatization to moderate hypoxia (3,800 m altitude), was studied. Past work has shown that hypoxic animals are damaged less by radiation than animals irradiated in a normal environment; therefore, it was postulated that if, after acclimatization to hypoxia the bone marrow oxygen tension returns to sea-level values, these animals should suffer radiation damage equivalent to animals at sea level. The principal parameters followed were the rate of depletion of injected Fe-59 from the plasma of chronically catheterized rats, and its subsequent reappearance in the circulating erythrocytes. After 20 days of acclimatization, both parameters for altitude-irradiated animals returned to the values of animals irradiated at sea level, previously having reflected increased erythropoiesis. In altitude nonirradiated animals the parameters indicated erythropoietic stimulation persisting up to 45 days acclimatization. The protective effect of the hypoxia on the stem cells vanished during acclimatization, presumably as cellular oxygen tension rose.

Gaugl, J. F.↗
NASA NTRS1972

Diffuse galactic X-rays from discrete sources.

The galactic ridge is interpreted as a population of intrinsically weak X-ray sources, and calculations are presented of the predicted intensity as a function of scale height and radial gradient. Observations of diffuse galactic X-radiation above 1 keV impose severe constraints on discrete-source interpretations of the galactic-plane excess observed at 0.25 keV.

Silk, J.↗
NASA NTRS1972

An X-ray monitor for measurement of a titanium tritide target thickness

An X-ray device capable of measuring titanium tritide film thickness from 0.1 to 30 micrometers has been built and tested. The monitor was designed for use in a rotating target system which used thick targets and incorporated a sputtering electrode to remove depleted layers from the target surface. The thickness measurement can be done in the presence of an intense background of bremsstrahlung and characteristic titanium X-radiation. A measurement can be accomplished in situ in two hours with reasonable accuracy.

Alger, D. L.↗
NASA NTRS1972

An X-ray monitor for measurement of a titanium tritide target thickness.

An X-ray device capable of measuring titanium tritide film thickness from 0.1 to 30 microns has been built and tested. The monitor was designed for use in a rotating target system which used thick targets and incorporated a sputtering electrode to remove depleted layers from the target surface. The thickness measurement can be done in the presence of an intense background of bremsstrahlung and characteristic titanium X-radiation. A measurement can be accomplished in situ in two hours with reasonable accuracy.

Alger, D. L.↗
NASA NTRS1974

Soft X-ray bremsstrahlung and fluorescent line production in the atmosphere by low energy electrons

The effect of low energy quasi-trapped or precipitating electrons which impact on the counter windows of soft X-ray detectors are discussed. The errors caused by X-rays produced in the residual atmosphere above a rocket-borne detector because of the resemblance to X-rays of cosmic origin are examined. The design and development of counter windows which make it possible to identify the atmospherically produced X-rays are described. Curves are presented to show the following: (1) preliminary low energy electron data from Atmospheric Explorer C, (2) X-ray flux in electron-excited nitrogen and oxygen, (3) typical proportional counter response to low energy cosmic rays, and (4) proportional counter response to X-radiation produced by electrons incident upon a gas of oxygen to nitrogen number of 0.4.

Kraushaar, W. L.↗
NASA NTRS1975

Photographic film image enhancement

A series of experiments were undertaken to assess the feasibility of defogging color film by the techniques of optical spatial filtering. A coherent optical processor was built using red, blue, and green laser light input and specially designed Fourier transformation lenses. An array of spatial filters was fabricated on black and white emulsion slides using the coherent optical processor. The technique was first applied to laboratory white light fogged film, and the results were successful. However, when the same technique was applied to some original Apollo X radiation fogged color negatives, the results showed no similar restoration. Examples of each experiment are presented and possible reasons for the lack of restoration in the Apollo films are discussed.

Horner, J. L.↗
NASA NTRS1978

Hard X-ray imaging from the solar probe

The solar probe offers a platform with particular advantages for studying solar nonthermal plasma processes via the observations of hard X-radiation from energetic electrons in the chromosphere and corona, these include (1) high sensitivity, (2) a second line of sign (in addition to the earth's) that can aid in three dimensional reconstruction of the source distribution, and, (3) the possibility of correlation with direct measurements of the nonthermal particles from the probe itself.

Hudson, H. S.↗
NASA NTRS1979

The High Energy X-ray Spectrum of 4U1700-37 Observed from OSO-8

The most intense hard X-ray source in the confused region in Scorpius is identified as 4U1700-37. The 3.4-day modulation is seen above 20 keV with the intensity during eclipse being consistent with zero flux. The photon-number spectrum from 20 to 150 keV is well represented by a single power law with a photo-number spectral index of -2.77 + or - 0.35 or by a thermal bremsstrahlung spectrum with kT = 27 96.8-min X-ray modulation previously reported at lower energies. Despite the difficulties in reconciling both the lack of periodic modulation in the emitted X-radiation and the orbital dynamics of the system with theories of the evolution and physical properties of neutron stars, the observed properties of 4U1700-37 are all consistent with the source being a spherically accreting neutron star rather than a black hole.

Dolan, J. F.↗
NASA NTRS1980

The high energy X-ray spectrum of 4U 1700-37 observed from OSO 8

The most intense hard X-ray source in the confused region in Scorpius has been identified as 4U 1700-37 (=HD 153919). Observations extending over three binary periods in 1978 September were carried out with the high-energy X-ray spectrometer on OSO 8. The 3.4 day modulation is seen above 20 keV with the intensity during eclipse being consistent with zero flux. The photonumber spectrum from 20 to 150 keV is well represented by a single power law with a photonumber spectral index of -2.77 + or - 0.35 or by a thermal bremsstrahlung spectrum with kT = 27 (+15, -7)keV. The counting rate above 20 keV outside of eclipse shows no evidence for the 96.8 minute X-ray modulation previously reported at lower energies. Despite the difficulties that exist in reconciling both the lack of periodic modulation in the emitted X-radiation and the orbital dynamics of the system with our currently accepted theories of the evolution and physical properties of neutron stars, the observed properties of 4U 1700-37 are all consistent with the source being a spherically accreting neutron star rather than a black hole.

Dolan, J. F.↗
NASA NTRS1980

The hard X-ray periodicity of GX 1 + 4

Pulses that recur with a 4.27 + or - 0.01 minute period were detected on April 2, 1974 in the 20-64 keV X-radiation from the galactic center region. Apparently emanating from GX 1 + 4, a major contributor to the high-energy radiation from that region, the pulses were 1.25 + or - 0.42 minutes in duration. If it is in fact the same source that has been observed on all occasions, the period is twice that previously believed.

Koo, J.-W. C.↗
NASA NTRS1981

The Pinhole/Occulter Facility

A large occulting system in space can be used for high resolution X-ray observations and for large aperture coronagraphic observations in visible and UV light. The X-ray observations can combine high angular resolution in hand (10 keV) X-radiation with the high sensitivity of a multiple pinhole camera, and can permit sensitive observations of bremsstrahlung from nonthermal particles in the corona. The large aperture coronagraphs have two major advantages: high angular resolution and good photon collection. This will permit observations of small scale structures in the corona for the first time and will give sufficient counting rates above the coronal background rates for sensitive diagnostic analysis of intensities and line profiles for coronal structures in the solar wind acceleration region. The technical basis for performing observations with a large occulting system in these three wavelength ranges is described as well as a pinhole/occulter facility presently being considered for Spacelab. Some indications about future developments are included.

Hudson, H. S.↗
NASA NTRS1982

Role of immobilization of irradiated rats in the protective effect of bone marrow shielding

Rats were exposed to X-radiation to study the influence of immobilization and shielding of part of bone marrow during exposure on survival. It is concluded that (1) the beneficial effect of the stress factor (created by the immobilization of rats during exposure) can aggregate with the effect of bone marrow shielding and, under certain conditions, imitate the latter; and (2) the probability of the protective effect of immobilization should be taken into account when assessing the influence of bone marrow shielding.

Gronskaya, N. F.↗