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Results for “X-RAY DENSITY MEASUREMENT”

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 NTRS1972

Location of the electron acceleration region in solar flares.

Observations of impulsive solar flare X rays (energy greater than 10 keV) by the OGO-5 satellite and the measurements of energetic solar electrons made with the Explorer-35 and Explorer-41 (IMP-5) satellites during the period March 1968-September 1969 have been analyzed in order to determine the ion density in the X-ray source region as well as the location of the electron acceleration region in the solar atmosphere. The ion density in the X-ray source region varies from event to event and lies between 1 and 100 billion ions per cu cm for those events in which the impulsive X-ray emission could be detected; for those events in which no impulsive emission was detected above threshold, the ion density in the X-ray source was less than one billion ions per cu cm. At least in some small solar flares, the region where the electrons are accelerated during the flash phase is located in the lower corona.

Kane, S. R.↗
NASA NTRS1976

On the ultrasoft X-ray background

The soft X-ray background has been studied down to energies of the order of 90 eV. The spectrum is found to be extremely soft, though not as steeply rising toward very low energies as indicated by Yentis et al. (1972). The background is both softer and more intense at high northern galactic latitudes than at low latitudes. Measured pulse-height spectra are analyzed under the assumption of different source models. The results are consistent with an origin of the background in a hot interstellar plasma with a temperature of about 800,000 K and a hot electron density of approximately 0.001 per cu cm. Upper limits are set on the soft X-ray emission from several interesting stellar objects.

Levine, A.↗
NASA NTRS1972

Retraction of cold-drawn polyethylene - Influence of lamellar thickness and density.

The role of crystal morphology in the retraction of oriented linear polyethylene was studied utilizing samples crystallized under conditions controlled to vary, separately, lamellar crystal thickness and density. Samples were oriented in a simple shear deformation to a strain of 4.0 prior to measuring retraction tendency in creep- and relaxation-type tests. Characterizations of specimens were made using wide- and small-angle x-ray techniques. The specific morphological variations were chosen to test the hypothesis that a long-range elastic restoring force can originate in conjunction with deformation of lamellar crystals and the consequent increase in lamellar crystal surface area and surface free energy. The results support this hypothesis.

Falender, J. R.↗
NASA NTRS1973

Computer enhancement of radiographs

Examination of three relevant noise processes and the image degradation associated with Marshall Space Flight Center's (MSFC) X-ray/scanning system was conducted for application to computer enhancement of radiographs using MSFC's digital filtering techniques. Graininess of type M, R single coat and R double coat X-ray films was quantified as a function of density level using root-mean-square (RMS) granularity. Quantum mottle (including film grain) was quantified as a function of the above film types, exposure level, specimen material and thickness, and film density using RMS granularity and power spectral density (PSD). For various neutral-density levels the scanning device used in digital conversion of radiographs was examined for noise characteristics which were quantified by RMS granularity and PSD. Image degradation of the entire pre-enhancement system (MG-150 X-ray device; film; and optronics scanner) was measured using edge targets to generate modulation transfer functions (MTF). The four parameters were examined as a function of scanning aperture sizes of approximately 12.5 25 and 50 microns.

Dekaney, A.↗
NASA NTRS1975

Ultraviolet observations of alpha Aurigae from Copernicus

Emission lines of L-alpha (1215.67 A) and O VI (1031.94 A) were detected in the spectroscopic binary alpha Aur (Capella) with the Princeton experiment on Copernicus. Temperatures of the emitting regions are inferred to be in excess of 300,000 K. The temperature and emission measure are consistent with a variable source of soft X-rays. If the emission is attributed to the primary star (G5 III), the atmosphere is expanding with velocities of about 20-100 km/s. Such expansion can lead to material within the binary system. The density of interstellar hydrogen inferred from absorption of stellar L-alpha appears to be approximately 0.01 hydrogen atoms per cu cm.

Dupree, A. K.↗
NASA NTRS1973

High resolution studies of the solar X-ray corona from Aerobee rockets

The research in high resolution solar X-ray astronomy is reported. The payload for the Aerobee 150 launch vehicle, which included a 23 cm diameter mirror whose polished surface was a nickel-phosphorus alloy is discussed along with the high resolution measurements, by Flight 13.028 CS, of the temperature and density structure of the lower corona. Flight 13.029 CS is also discussed.

Davis, J. M.↗
NASA NTRS1976

The temperature and density structures of an X-ray flare during the decay phase

The X-ray flare of 9 August 1973 was characterized by a spatially small kernel structure which persisted throughout its duration. The decay phase of this flare was observed in the objective grating mode of the X-ray telescope aboard the Skylab. Data analysis was carried out by scanning the images with a microdensitometer, converting the density arrays to energy using laboratory film calibration data and taking cross sections of the energy images. The 9 August flare shows two distinct periods in its decay phase, involving both cooling and material loss. The objective grating observations reveal that the two phenomena are separated in time. During the earlier phase of the flare decay, the distribution of emission measure as a function of temperature is changing, the high temperature component of the distribution being depleted relative to the cooler body of plasma. As the decay continues, the emission measure distribution stabilizes and the flux diminishes as the amount of material at X-ray emitting temperatures decreases.

Silk, J. K.↗
NASA NTRS1972

A shock-induced phase change in iron-silicate garnet.

Hugoniot measurements on iron-silicate garnet demonstrate that above a shock pressure of about 205 kbar transition to a high-pressure phase(s), having an apparent zero-pressure density and bulk modulus of 4.44 g/cu cm and 3.3 Mbar, occurs. Crystal chemical systematics and Debye-Scherrer X-ray patterns of a recovered phase(s), which may be the shock-induced high-pressure form, suggest possible formation of a phase with a density of 4.48/cu cm. Occurrence of such a polymorph of garnet in the mantle would give rise to an increase in density and seismic velocity below 600 km in the earth.

Ahrens, T. J.↗
NASA NTRS1976

The interstellar medium in the line of sight to X Persei and 3U 0352+30

The X-ray absorption column of 3U 0352+30 obtained with the Copernicus X-ray telescopes is compared with the atomic and molecular hydrogen column densities in the line of sight to X Per, as measured with the Copernicus ultraviolet telescopes, and with the visible reddening of X Per, by means of reddening/X-ray absorption-column relationships. The results are consistent with both the star and X-ray source being equidistant. When comparing X-ray absorbing column densities with those derived by other means, it is necessary to include the effects of molecular hydrogen in the line of sight to X Per and, in particular, the related number of medium-weight elements. It is suggested that failure to do this in previous work may account for reported discrepancies between the X-ray and radio column densities to the Crab Nebula and other sources. The far-ultraviolet extinction curve of X Per is presented.

Mason, K. O.↗
NASA NTRS1976

X-ray observation of 3U 1700-37

X-ray observations with Copernicus reveal three categories of flux variability in 3U 1700-37. High amplitude hourly variations are energy independent in the 3-11 keV range while a change in the low energy absorbing column causes variations in flux level on an orbital time scale. This absorption is most severe prior to eclipse ingress, suggesting that the distribution of absorbing material around the X-ray source is asymmetrical with respect to the line of centers of the binary system. The absorbing material may be identical with a high density region inferred from optical observations of HD 153919. In the third category, the maximum source intensity per binary cycle is variable by at least a factor of two between observations. Measurement of the eclipse duration on three occasions indicate that it is significantly less than when observed by Uhuru.

Mason, K. O.↗
NASA NTRS1973

Investigation of solidification in zero-gravity environment; M553 sphere forming experiment. Phase C: Evaluation of Skylab specimens

Results on specimen evaluation and discussion of solidification behavior in each case are reported in the following order: (1) specimen SL-1.6, (2) specimen SL-2.8, (3) specimen SL-2.4, (4) specimen SL-1.10 and (5) specimen SL-1.11. Comparison is made with ground-processed specimens of similar composition, whenever pertinent and meaningful. Among the nondestructive evaluation methods the measurement of sphericity was conducted by micrometric and shadowgraphic techniques. The intricate shape of specimens in some cases appeared difficult to define. In measuring the density, liquid penetration inside cavities that outcrop on the surface was avoided by sealing off these cavities. Among the destructive evaluation methods the use of the Quantimet 720 required particular attention, because of the small difference in contrast between second phases and micropores. With regard to microporosity microvoids in the core of some specimens were so fine that X-ray microradiography had to be used.

Kattamis, T. Z.↗
NASA NTRS1976

Skylab ATM/S-056 X-ray event analyzer: Instrument description, parameter determination, and analysis example (15 June 1973 1B/M3 flare)

The Skylab ATM/S-056 X-Ray Event Analyzer, part of an X-ray telescope experiment, is described. The techniques employed in the analysis of its data to determine electron temperatures and emission measures are reviewed. The analysis of a sample event - the 15 June 1973 1B/M3 flare - is performed. Comparison of the X-Ray Event Analyzer data with that of the SolRad 9 observations indicates that the X-Ray Event Analyzer accurately monitored the sun's 2.5 to 7.25 A X-ray emission and to a lesser extent the 6.1 to 20 A emission. A mean average peak temperature of 15 million K at 1,412 UT and a mean average peak electron density (assuming a flare volume of 10 to the 13 power cu km) of 27 million/cu mm at 1,416 to 1,417 UT are deduced for the event. The X-Ray Event Analyzer data, having a 2.5 s time resolution, should be invaluable in comparisons with other high-time resolution data (e.g., radio bursts).

Wilson, R. M.↗
NASA NTRS1976

An observation of the diffuse soft X-ray/extreme-ultraviolet background

Results are reported for observations of diffuse radiation in the spectral bands from 114 to 150 A and from 44 to 120 A, which were made with rocket-borne proportional counters in areas of the sky near galactic coordinates 150 deg longitude, -15 deg latitude and 189 deg longitude, 3 deg latitude. The observed fluxes are 0.125 photon per sq cm/s/sr/eV at 180 eV, which is consistent with previous measurements, and 3.2 photons per sq cm/s/sr/eV at 100 eV, which indicates a steeply rising spectrum. It is noted that these fluxes are significantly smaller than those detected by Yentis et al. (1972), and the differences are attributed to either a terrestrial origin of the fluxes or the direction of observation. Constraints are placed on the parameters of simple emission models of celestial origin, and a rigorous upper limit is determined for the space density of white dwarfs at a blackbody temperature of at least 100,000 K.

Cash, W.↗
NASA NTRS1975

The interpretation of simultaneous soft X-ray spectroscopic and imaging observations of an active region

Simultaneous soft X-ray spectroscopic and broad-band imaging observations of an active region have been analyzed together to determine the parameters which describe the coronal plasma. From the spectroscopic data, models of temperature-emission measure-elemental abundance have been constructed which provide acceptable statistical fits. By folding these possible models through the imaging analysis, models which are not self-consistent can be rejected. In this way, only the oxygen, neon, and iron abundances of Pottasch (1967), combined with either an isothermal or exponential temperature-emission-measure model, are consistent with both sets of data. Contour maps of electron temperature and density for the active region have been constructed from the imaging data. The implications of the analysis for the determination of coronal abundances and for future satellite experiments are discussed.

Davis, J. M.↗
NASA NTRS1976

Iron line emission from a high-temperature plasma in Cassiopeia A

The letter reports a measurement of the X-ray spectrum of Cas A with a proportional counter on board OSO-8. The high-energy data (greater than 7 keV) are found to agree equally well with a power law having a number index of about 4.5 and with a thermal spectrum having kT of about 3.9 keV. A narrow iron line predicted by the thermal model is also observed; this line is centered at about 6.67 keV and has an equivalent width of approximately 1270 eV. The low-energy data (below 6 keV) are not fully accounted for by the above thermal spectrum, but are fitted well by an additional low-temperature thermal component with kT not exceeding 0.7 keV and an atomic hydrogen column density of approximately 10 to the 22nd power per sq cm. The iron abundance in the plasma at an electron temperature of 40 keV is estimated from the observed line-to-continuum ratio, and it is shown that a normal cosmic iron abundance is adequate to explain the observation.

Pravdo, S. H.↗
NASA NTRS1976

Absorption of CO2-laser radiation in a hypocycloidal-pinch plasma

Absorption of a 50-J pulsed CO2 laser beam in the plasma produced in a hypocycloidal-pinch apparatus was studied. The apparatus consists of three disk electrodes with a 5-cm hole on the axis. The current sheets are snow-plowed toward the center of the hole to produce a plasma with a density greater than 10 to the 18th/cu cm and a temperature near 1 keV which emits soft X rays for 5 microsec. IR detectors measured the laser radiation incident onto, transmitted through, and scattered from the plasma as functions of time. For a period up to 70 microsec from the onset of X-ray emission, neither transmitted nor scattered laser radiation was observed above the detector threshold of 0.3% of the incident flux. This indicates effective absorption of the laser beam (greater than 99%) and that the particle confinement time extends far beyond the energy confinement time of 5 microsec. Thus, the plasma in this apparatus appears much more amenable to laser heating than that in a theta pinch.

Lee, J. H.↗