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Results for “X-ray image analysis”

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 109 records · Page 6
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NASA NTRS1979

Analysis of NOAA-MSFC GOES X-ray telescope

The general telescope system was assumed to be a paraboloid-hyperboloid in a Wolter Type 1 configuration. The equations which specify the telescope parameters and the resolution as a function of the collecting area are discussed as well as the spot size and point response function for off-axis rays. The measured resolution of the Goddard ATM X-ray telescope (S-056) is compared to the rms blur circle radius and the full width half maximum of the line spread function. An empirical scaling formula, Eq. 26, which transforms the rms blur circle radius into a more accurate measure of resolution, is introduced. The geometrical imaging properties of the proposed NOAA-MSFC GOES X-ray telescope are considered. Conclusions and alternate mirror designs are included.

Shealy, D. L.↗
NASA NTRS1978

Iodine imaging using spectral analysis

Existing radiographic imaging systems provide images which represent an integration or averaging over the energy spectrum. In order to provide noninvasive angiography it is necessary to image the relatively small amounts of iodine which are available following an intravenous administration. This is accomplished by making use of the special spectral characteristics of iodine. Two methods will be presented. One involves a special grating for encoding the iodine information in the form of a fine line pattern. This is subsequently decoded to provide images of iodinated structures which are otherwise almost invisible. The second method utilizes a scanned X-ray beam which is rapidly switched in the high energy region. In this region, iodine experiences significant variations in the attenuation coefficient while bone and soft tissue do not. An efficient and accurate X-ray detector can be used with scanned X-ray beams. This provides a high degree of sensitivity enabling the visualization of small vessels containing relatively dilute iodine.

Macovski, A.↗
NASA NTRS1986

Theoretical analysis of segmented Wolter/LSM X-ray telescope systems

The Segmented Wolter I/LSM X-ray Telescope, which consists of a Wolter I Telescope with a tilted, off-axis convex spherical Layered Synthetic Microstructure (LSM) optics placed near the primary focus to accommodate multiple off-axis detectors, has been analyzed. The Skylab ATM Experiment S056 Wolter I telescope and the Stanford/MSFC nested Wolter-Schwarzschild x-ray telescope have been considered as the primary optics. A ray trace analysis has been performed to calculate the RMS blur circle radius, point spread function (PSF), the meridional and sagittal line functions (LST), and the full width half maximum (PWHM) of the PSF to study the spatial resolution of the system. The effects on resolution of defocussing the image plane, tilting and decentrating of the multilayer (LSM) optics have also been investigated to give the mounting and alignment tolerances of the LSM optic. Comparison has been made between the performance of the segmented Wolter/LSM optical system and that of the Spectral Slicing X-ray Telescope (SSXRT) systems.

Shealy, D. L.↗
NASA NTRS1977

Spectrophotometry of the transient X-ray source A0620-00

Optical observations of the transient X-ray source A0620-00 over the wavelength range from about 3200 to 6600 A are analyzed which were made with the 5-m Hale telescope using a multichannel spectrometer, a digital spectrograph with a cooled integrating SIT vidicon, and an image photon-counting system attached to the camera of the coude spectrograph. Infrared observations at 1.65, 2.2, and 3.5 microns are also examined. Individual spectral lines of special interest are discussed, the E(B-V) color excess is estimated to be about 0.40, and a distance of 1200 pc is adopted. Analysis of the continuous spectrum yields several simple binary models. A specific model is proposed in which one of the continuum sources is an optically thick object characterized by a model atmosphere at a temperature of 25,000 to 30,000 K and the second source is either a cool black body at 4000 K or a partially optically thick source of bound-free plus free-free radiation from a hydrogen gas with an electron temperature of at least 100,000 K. Some possible parameters of these sources and of the accretion disk are considered.

Oke, J. B.↗
NASA NTRS1987

X-ray observations of solar flares with the Einstein Observatory

The first Einstein Observatory Imaging Proportional Counter (IPC) observations of solar flares are presented. These flares were detected in scattered X-ray light when the X-ray telescope was pointed at the sunlit earth. The propagation and scattering of solar X-rays in the earth's atmosphere are discussed in order to be able to deduce the solar X-ray flux incident on top of the atmosphere from scattered X-ray intensity measurements. After this correction, the scattered X-ray data are interpreted as full-disk observations of the sun obtained with the same instrumentation used for observations of flares on other stars. Employing the same data analysis and interpretation techniques, extremely good agreement is found between the physical flare parameters deduced from IPC observations and 'known' properties of compact loop flares. This agreement demonstrates that flare observations with the IPC can reveal physical parameters such as temperature and density quite accurately in the solar case and therefore suggests that the interpretations of stellar X-ray flare observations are on a physically sound basis.

Schmitt, J. H. M. M.↗
NASA NTRS1984

A detailed X-ray and radio comparison of Kepler's supernova remnant

High-resolution radio images of Kepler's SNR (SNR (SN 1604) at 6 and 21 cm have been obtained using the VLA. The orientation of linear polarization in the SNR implies a substantial nonrandom radial component for the magnetic field of the remnant. Based on a new X-ray picture of the SNR, obtained using the Einstein Observatory, a detailed comparison of the X-ray and radio morphology is carried out. There is a good correlation between rotation measure, obtained from the radio maps, and emission measure, an X-ray-derived quantity in the SNR shell. From the mean electron density value infered from an analysis of X-ray fluxes, a mean radial magnetic field of 14 micro G and a total magnetic field of 70 microG are estimated. The energy density of relativistic electrons in Kepler's SNR in the shell comparable to the energy density in the magnetic field; the relativistic electron-pressure is 2 percent of the thermal gas pressure. The strong correlation between radio emissivity and X-ray emissivity found over the SNR in somewhat large scale can be ascribed to acceleration of thermal electrons at the shock wave and insignificant diffusion of resultant relativistic electrons.

Matsui, Y.↗
NASA NTRS1987

Imaging observations of the evolution of meter-decameter burst emission during a major flare

The results of a study of the evolution of the February 3, 1986 flare at meter-decameter wavelengths are presented, using the two-dimensional imaging observations made with the Clark Lake multifrequency radioheliograph. The flare was complex and produced various types of meter-decameter bursts. The preflare activity was observed in the form of type III bursts some tens of minutes prior to the impulsive onset. From the positional analysis of the preflare and impulsive phase type III bursts and other measured characteristics, the characteristics of energy release and possible magnetic field configurations in the vicinity of the energy release region are discussed. From positional and temporal studies of the flare continuum and type II burst in relation to the microwave and hard X-ray emissions, the possible magnetic field structures in which the accelerated particles are confined or along which they propagate are discussed; a schematic model of the flaring region is developed, based upon this study.

Gopalswamy, N.↗
NASA NTRS1988

A comprehensive study of the X-ray structure and spectrum of IC 443

This paper presents the results of a comprehensive study of the X-ray emission from the supernova remnant IC 443, using the solid state spectrometer, IPC, and high-resolution images of the Einstein Observatory, and the medium-energy detector of the HEAO 1 A-2 experiment. A soft X-ray appearance was observed, highly atypical of a supernova remnant in the adiabatic phase, with little correlation between X-ray and optical or radio features. The best-fit models of the low-energy X-ray spectrum of the brightest area of the remnant suggest either that the remnant has not yet attained ionization equilibrium or that the X-rays arise in a multiphase medium. Pronounced soft X-ray spectral differences across the remnant are accounted for by variations in absorption by an intervening molecular cloud. The analysis suggests that, despite the atypical X-ray appearance, the X-ray emission in IC 443 is probably confined to a thin (0.1 pc) shell.

Petre, R.↗
NASA NTRS1985

Search for scattered X-ray halos around variable sources - The X-ray halo of Cygnus X-1

The results of a program to search for the presence of halos due to X-ray scattering by interstellar grains in the line-of-sight to variable X-ray sources are reported. As part of this program, four Einstein HRI images of Cyg X-1 were examined. The analysis technique exploits the intrinsic aperiodic variability of this source to map the point response function of the optics. Any scattered halo present will not reflect short-term central source time variability, since such variability is smoothed by differential time delays of order days. Thus, a residual, nonvariable component to the surface brightness distribution (comprising about 12 percent or more of the source flux) is interpreted as a scattered halo. The Cyg X-1 halo is consistent with those of other sources found in previous studies using different techniques. Comparison is also made with a scattering model and, despite uncertainties in source spectrum and distance, reasonable agreement with the observatons is found using a standard interstellar grain model. The potential of X-ray scattering as a probe of the properties of interstellar grains is demonstrated.

Bode, M. F.↗
NASA NTRS1987

Two dimensional imaging observations of meter-decameter bursts associated with the February 1986 flare activity

An analysis is presented of the two dimensional imaging observations of a flare observed on 3 Feb. l986 using the Clark Lake Multifrequency Radioheliograph. The flare produced almost all types of Meter-decimeter radio emission: enhanced storm radiation, type III/V bursts, II and IV and flare continuum. The flare continuum had early (FCE) and late (FC II) components and the type II occurred during the period between these two components. Comparing the source positions of type III/V and FCE it was found that these bursts must have occurred along adjacent open and closed field lines, respectively. The positional analysis of type II and FC II implies that the nonthermal electrons responsible for FC II need not be accelerated by type II shock and this conclusion is further supported by the close association of FC II with a microwave peak. Using the positional and temporal analysis of all these bursts and the associated hard X-ray and microwave emissions, a schematic model is developed for the magnetic field configuration in the flaring region in which the nonthermal particles responsible for these bursts are confined or along which they propagate.

Gopalswamy, N.↗
NASA NTRS1985

A First Look at Airborne Imaging Spectrometer (AIS) Data in an Area of Altered Volcanic Rocks and Carbonate Formations, Hot Creek Range, South Central Nevada

Three flight lines of Airborne Imaging Spectrometer (AIS) data were collected in 128 bands between 1.2 and 2.4 microns in the Hot Creek Range, Nevada on July 25, 1984. The flight lines are underlain by hydrothermally altered and unaltered Paleozoic carbonates and Tertiary rhyolitic to latitic volcanics in the Tybo mining district. The original project objectives were to discriminate carbonate rocks from other rock types, to distinguish limestone from dolomite, and to discriminate carbonate units from each other using AIS imagery. Because of high cloud cover over the prime carbonate flight line and because of the acquisition of another flight line in altered and unaltered volcanics, the study has been extended to the discrimination of alteration products. In an area of altered and unaltered rhyolites and latites in Red Rock Canyon, altered and unaltered rock could be discriminated from each other using spectral features in the 1.16 to 2.34 micron range. The altered spectral signatures resembled montmorillonite and kaolinite. Field samples were gathered and the presence of montmorillonite was confirmed by X-ray analysis.

Feldman, S. C.↗
NASA NTRS1976

Evidence for magnetic energy storage in coronal active regions

Examination of X-ray images obtained by the S-054 X-ray spectrographic telescope on Skylab shows the presence of some atypical X-ray-emitting coronal structures in active regions which are not consistent with potential extrapolations of photospheric magnetic fields. Analysis of the observed temporal changes in the X-ray-emitting active-region structures demonstrates that the majority of these consist of brightness changes representing temperature (and perhaps density) variations of the material in the loops.

Krieger, A. S.↗
NASA NTRS1979

Ray-tracing the convex curved crystal X-ray spectrograph

The convex curved crystal X-ray spectrograph has recently seen increasing use for the spectral analysis of transient plasmas. The present paper describes the calculation of ray paths through the spectrograph for both localized and extended sources. The method traces a ray from any given source point to its point of diffraction by the curved crystal and then to the imaging circle, where the image point is obtained. Application of the ray tracing method is made to some actual experimental configurations to obtain resolution values and source sizes. Wavelength calibrations are obtainable with the ray tracing method in advance of instrument construction.

Kastner, S. O.↗
NASA NTRS1984

Nuclear Science Symposium, 30th, and Symposium on Nuclear Power Systems, 15th, San Francisco, CA, October 19-21, 1983, Proceedings

The range of disciplines covered includes physics instrumentation, data acquisition, FASTBUS, radiation detectors, scintillators, photomultipliers and optical detectors, subnanosecond 2-D imaging, medical and health instrumentation, reactor instrumentation, and space instrumentation. Cerenkov detectors, the prevention and rate capability of breakdown processes in wire chambers, and an interactive parallel processor for data analysis are studied. Attention is also given to bismuth germanate's role in gamma-ray spectroscopy, and the construction of a broadband universal sampling head is described. Gamma-ray imaging with a rotating hexagonal uniform redundant array, and broadband X-ray astronomical spectrometry are considered.

Nakamura, M.↗
NASA NTRS1984

The Euclidean slope of the X-ray source counts - A 'cosmic conspiracy'

The selection criteria adopted for the Einstein Observatory Medium Sensitivity survey are delineated and the results of an analysis of the source-count relation for extragalactic X ray sources is presented. Only IPC fields at least 20 deg outside of the galactic plane, and then only those images in the center of the fields, were included. A total of 345 objects were sighted in the 0.3-3.5 keV energy interval, and 77 percent were concluded to be extragalactic. Most were associated with active galactic nuclei (AGN), including Seyfert galaxies and quasars, and galactic clusters. A slope of about 1.7 was calculated for the power law of the energy spectra of AGNs and close to 1.0 for clusters.

Gioia, I. M.↗
NASA NTRS1987

A laboratory demonstration of high-resolution hard X-ray and gamma-ray imaging using Fourier-transform techniques

A laboratory imaging system has been developed to study the use of Fourier-transform techniques in high-resolution hard X-ray and gamma-ray imaging, with particular emphasis on possible applications to high-energy astronomy. Considerations for the design of a Fourier-transform imager and the instrumentation used in the laboratory studies is described. Several analysis methods for image reconstruction are discussed including the CLEAN algorithm and maximum entropy methods. Images obtained using these methods are presented.

Palmer, David↗
NASA NTRS1987

A search for millisecond periodic and quasi-periodic pulsations in low-mass X-ray binaries

The results of a Fourier analysis to detect fast periodic and quasi-periodic pulsations in the X-ray emission from the sources 4U 0614 + 091, 4U 1636 - 536, 4U 1735 - 44, 4U 1820 30, GX 5 - 1, GX 9 + 9, Ser X-1, and Cyg X-2 are presented. This search has been carried out for the first time in the soft energy band (0.2-2.0 keV), using data from the Einstein Observatory high resolution imager instrument. An approximate method of minimizing the decrease in search sensitivity produced by the Doppler shift of the pulse periods due to source orbital motion is discussed. No pulsations have been detected, and upper limits, which depend on the orbital parameters assumed for the sources, are set on the pulsed flux fraction.

Mereghetti, S.↗