Search NASA⌕ Search

SEARCH · Search NASA

Results for “x-ray fluorescence imaging”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Enhanced orbital geochemical images by the Laplacian subtraction method

Orbital geochemical studies of the moon based on X-ray fluorescence and gamma-ray spectroscopy have been successful. There are, however, difficulties if geologic units or other features to be investigated are too small. Investigations have been conducted with the objective to improve with the aid of image enhancement methods both spatial resolution and contrast for the geochemical experiments. A description is provided of the Laplacian subtraction method of enhancement. It was found that the application of a least-squares version of this method to the Mg/Al ratios obtained by orbital X-ray fluorescence improved geochemical images considerably. The spatial resolution increased by about a factor of 2 and the contrast also increased. The Laplacian of an image can also be used to detect very small 'hot' or 'cold' spots in an image.

Schonfeld, E.↗
NASA NTRS1982

High spatial resolution Mg/Al maps of the western Crisium and Sulpicius Gallus regions

High spatial resolution Mg/Al ratio maps of the western Crisium and Sulpicius Gallus regions of the moon are presented. The data is from the X-ray fluorescence experiment and the image enhancement technique in the Laplacian subtraction method using a special least-squares version of the Laplacian to reduce noise amplification. In the highlands region west of Mare Crisium several relatively small patches of smooth material have high local Mg/Al ratio similar to values found in mare sites, suggesting volcanism in the highlands. In the same highland region there were other smooth areas with no high Mg/Al local values and they are probably Cayley Formation material produced by impact mass wasting. The Sulpicius Gallus region has variable Mg/Al ratios. In this region there are several high Mg/Al ratio spots, two of which occur at the highland-mare interface. Another high Mg/Al ratio area corresponds to the Sulpicius Gallus Rima I region. The high Mg/Al ratio material in the Sulpicius Gallus region is probably pyroclastic.

Schonfeld, E.↗
NASA NTRS1993

X-ray based displacement and strain measurements for hostile environments

A completely new method of non-contacting, hostile environment displacement and strain measurement based on the focus and scanning of x-rays, has been developed and demonstrated. The new technique has the ability to overcome many of the limitations associated with available methods. The system is based on the focus and scanning of low energy, hard x-rays such as those emanating from table top copper or molybdenum sources. The x-rays are focused into a narrow and intense line image which can be swept onto targets that fluoresce secondary x-ray radiation. By monitoring the secondary radiation intensity and comparing it with the focused x-ray image's position as it is swept over the target edge, the position of the target edge relative to the focused image can be determined. The present system has a resolution of 0.5 micron, which has been shown to be limited by bearing backlash (or 'yaw' error) in the linear translation table. Its use has been demonstrated in the presence of an open flame with a resultant target temperature in excess of 2000 degrees Fahrenheit (1000 degrees Celsius). Strain measurements have been conducted in a laboratory environment at both room temperature and at a specimen temperature of 1300 degrees Fahrenheit, with an accuracy of within 20 microstrain (primarily a function of the 0.5 micron resolution limit). The main advantage of the technique lies in the penetrating, non-refractive nature of x-rays, which are virtually immune to the presence of refracting gas layers, smoke, flame or intense thermal radiation.

Canistraro, Howard A.↗
NASA NTRS1977

Imaging of lunar surface chemistry from orbital X-ray data

Color images of the lunar surface from 20 deg W to 120 deg E were prepared which map the variations in the distribution of Al, Mg, and Si as expressed by the ratios of the Al/Si and the Mg/Al fluorescent X-ray intensities. Through the use of image enhancement techniques developed for the La Jolla Consortium on remote sensing of the moon, detailed information previously unobserved has been made available. The frequency distribution of the Apollo 15 and 16 intensity ratios for individual 0.25 x 0.25 deg surface units is clearly bimodal, peaking at 0.81 for mare material and 1.12 for nearside highland material, which values correspond to concentration ratios of 0.39 and 0.54, respectively, for Al/Si.

Bielefeld, M. J.↗
NASA NTRS1992

X-ray-based displacement measurement for hostile environments

A new method on noncontacting, high temperature extensometry based on the focus and scanning of X-rays is currently under development and shows great promise of overcoming limitations associated with available techniques. The chief advantage is the ability to make undisturbed measurements through stratified or flowing gases, smoke, and flame. The system is based on the ability to focus and scan low energy, hard X-rays such as those emanating from copper or molybdenum sources. The X-rays are focused into a narrow and intense line image which can be scanned onto targets that fluoresce secondary X-ray radiation. The final goal of the system is the ability to conduct macroscopic strain measurements in hostile environments by utilizing two or more fluorescing targets. Current work is limited to displacement measurement of a single target with a resolution of 1.25 micro-m and a target temperature of 1200 C, directly through an open flame. The main advantage of the technique lies in the penetrating nature of X-rays which are not affected by the presence of refracting gas layers, smoke, flame, or intense thermal radiation, all of which could render conventional extensometry methods inoperative or greatly compromise their performance.

Canistraro, H. A.↗
NASA NTRS1992

Performance of a multistep fluorescence-gated proportional counter for hard X-ray astronomy

Results from the first flight of our proportional counter in an imaging telescope led us to rebuild the detector. We have used a Penning gas mixture (xenon + 1 percent isobutylene) and introduced a preamplification region to improve the energy resolution. We have rebuilt the pressure vessel making novel use of molybdenum as the housing material in order to reduce the residual instrument background, particularly in the fluorescence-gated mode for which the detector design has been optimized. We have also increased the sensitive gas depth from 9 to 14 cm to further increase the sensitivity to both fluorescent pairs and conventional singles. Our calibrations have shown that the overall energy resolution of the detector has been enhanced by a factor of 2, and we predict that the sensitivity at float will increase by a factor of 3 in the 50-70 keV energy band.

Dietz, K. L.↗
NASA NTRS1977

Lunar surface chemistry - A new imaging technique

Detailed chemical maps of the lunar surface have been constructed by applying a new weighted-filter imaging technique to Apollo 15 and Apollo 16 X-ray fluorescence data. The data quality improvement is amply demonstrated by (1) modes in the frequency distribution, representing highland and mare soil suites, which are not evident before data filtering, and (2) numerous examples of chemical variations which are correlated with small-scale (about 15 kilometer) lunar topographic features.

Andre, C. G.↗
NASA NTRS1976

A correlation study based on Al/Si X-ray fluorescence data from southwestern part of Mare Serenitatis

A correlation study based on Al/Si intensity ratios, broad-spectrum visible-albedo measurements, color-difference photography, color-ratio images, and spectral-reflectivity curves was undertaken to understand why the Tacquet Formation in southwestern Mare Serenitatis has unusually low visible albedos for the Al/Si intensity ratios measured by the Apollo 15 X-ray fluorescence experiment. The statistical analysis of the Al/Si data is described, general correlations among all the remote-sensing data are noted, and correlations in the area of the Tacquet Formation are examined. It is shown that the discrepancy between visible albedos and Al/Si intensities may be due primarily to the presence of unevenly deposited highland-type ejecta from Menaleus crater, although the possibility cannot be excluded that the Tacquet Formation is more complex than a simple mixture of highland and mare materials.

Andre, C. G.↗
NASA NTRS1976

Terrestrial bodies orbiter, LUNAR - A system for detailed global measurements of a planet's properties

The NASA Lunar Polar Orbiter, to be launched by a Delta vehicle in 1980, is designed to perform a global exploration of such moon properties as the gravity field, figure, and surface composition, as well as a lunar resource survey. The paper reviews the mission, spacecraft, and data system concepts in terms of baseline mission sequence, choice of orbits, spacecraft configuration requirements, mission sequence requirements and data system and operations. Scientific experiments planned for the Orbiter mission include geophysical altimetry and gravity experiments, heat flow experiment, magnetic field experiments, measurements of the moon's natural gamma-ray spectrum, X-ray fluorescence of lunar surface materials, sunlight reflectance spectroscopy, and spectro-stereo imaging. Characteristics of instruments designed for use in these investigations are examined. Through the use of advanced sensors and data-system techniques, coupled with well-developed spacecraft systems, the mission promises to return a very large quantity and variety of lunar data at a cost comparable with that of simpler missions in the past.

Burke, J. D.↗
NASA NTRS1992

High-resolution Elemental Mapping of the Lunar Surface

New instruments and missions are being proposed to study the lunar surface as a result of the resurgence of interest in returning to the Moon. One instrument recently proposed is similar in concept to the x-ray fluorescence detectors flown on Apollo, but utilizes fluorescence from the L- and M-shells rather than the K-shell. This soft X-Ray Flourescence Imager (XRFI) is discussed.

Edwards, Bradley C.↗
NASA NTRS1985

On the viability of exploiting L-shell fluorescence for X-ray polarimetry

It has been suggested that one may build an X-ray polarimeter by exploiting the polarization dependence of the angular distribution of L-shell fluorescence photons. In this paper the sensitivity of this approach to polarimetry is examined theoretically. The calculations are applied to several detection schemes using imaging proportional counters that would have direct application in X-ray astronomy. It is found, however, that the sensitivity of this method for measuring X-ray polarization is too low to be of use for other than laboratory applications.

Weisskopf, M. C.↗
NASA NTRS1978

Interdisciplinary investigations of comparative planetology

Research supported wholly or in part by NASA's Planetary Programs Office is summarized. Topics covered include: the evaporation of ice in planetary atmospheres: ice-covered rivers on Mars; reducing greenhouses and the temperature history of Earth and Mars; particle motion on Mars inferred from the Viking Lander cameras; the nature and visibility of crater-associated streaks on Mars; the equilibrium figure of Phobos and other small bodies; striations on Phobos; radiation pressure and Poynting-Robertson drag for small spherical particles; direct imaging of extra-solar planets with stationary occultations; the relation between planetology and conventional astrophysics; remote spectral studies and in situ X-ray fluorescence analysis of the Martian surface; small channels on Mars; junction angles of Martian channels; constraints on Aeolian phenomena on Mars; the geology of Mars; and the flow of erosional debris on the Martian terrain.

Sagan, C.↗
NASA NTRS1989

X-ray calibration of a virtual phase 1024 x 1024 CCD

Results are presented on a calibration with X-rays of a front-illuminated virtual phase CCD with a 1024 x 1024 pixel array, performed as a part of the Solar-A preparation, which is a joint Japanese-U.S.-UK space project scheduled for a launch in August 1991. In the experiment, absolute quantum efficiency (QE) of a virtual CCD was measured at 14 wavelengths between 5.4 and 67.7 A, and its flat field responses to the illumination by C-K and Al-K X-rays were investigated together with its imaging properties in visible light. Higher than expected QE measurements were obtained at soft X-ray and EUV wavelengths; these are considered to be caused by fluorescence occurring in the absorbing layers on the CCD-entrance aperture.

Catura, R. C.↗
NASA NTRS1990

Multistep fluorescence gated proportional counters

A proportional counter is introduced in which the levels of energy and spatial resolutions and background rejection permit the application of the device to X-ray astronomy. A multistep approach is employed in which photons cause a signal that triggers the system and measures the energy of the incident photon. The multistep approach permits good energy resolution from parallel geometry and from the imaging stage due to coupling of the imaging and amplification stages. The design also employs fluorescence gating to reduce background, a method that is compatible with the multistep technique. Use of the proportional counter is reported for NASA's supernova campaign, and the pair background is below 0.0001 counts/sq cm sec keV at the xenon k-edge. Potential improvements and applications are listed including the CASES, POF, and EXOSS mission programs.

Ramsey, Brian D.↗
NASA NTRS1988

High-Resolution Detector For X-Ray Diffraction

Proposed x-ray-sensitive imaging detector offers superior spatial resolution, counting-rate capacity, and dynamic range. Instrument based on laser-stimulated luminescence and reusable x-ray-sensitive film. Detector scans x-ray film line by line. Extracts latent image in film and simultaneously erases film for reuse. Used primarily for protein crystallography. Principle adapted to imaging detectors for electron microscopy and fluorescence spectroscopy and general use in astronomy, engineering, and medicine.

Carter, Daniel C.↗
NASA NTRS1981

Planetary exploration sensor systems

Most of the instruments that have been used in planetary exploration have been either spectrometers or imaging devices. Instruments of these types are being developed for the Galileo and VOIR (Venus Orbiting Imaging Radar) missions. Galileo will take advantage of new CCD (charge-coupled device) technology, and VOIR will use techniques of synthetic aperture radar developed for Seasat. For determining the macrostructure of mineral resources, the best approach is believed to involve acoustic imaging, essentially a seismic data processing technique. Determinations of microstructure would require a light microscope and an electron microscope. For determining the nature and form of volatiles, a differential scanning calorimeter could be used. To determine the mineral composition, an electron beam microprobe with X-ray fluorescence and spectroscopy would be used.

Saunders, R. S.↗
NASA NTRS1989

The MSFC large-area imaging multistep proportional counter

A large-area multistep imaging proportional counter that is being currently developed at the Marshall Space Flight Center is described. The device, known as a multistep fluorescence gated detector, consists of a multiwire proportional counter (MWPC) with a preamplification region. The MWCP features superior spatial resolution with a very high degree of background rejection. It is ideally suited for use in X-ray astronomy in 20-100 keV energy range. The paper includes the MWPC schematic and a list of instrument specifications.

Ramsey, B. D.↗
NASA NTRS1993

Planetary and satellite x ray spectroscopy: A new window on solid-body composition by remote sensing

The rings and most of the satellites of the outer planets orbit within the radiation belts of their parent bodies. This is an environment with intense fluxes of energetic electrons. As a result, these objects are strong emitters of X-rays. The characteristic X-ray lines from these bodies depend on atomic composition, but they are not sensitive to how the material is arranged in compounds or mixtures. X-ray fluorescence spectral analysis has demonstrated its unique value in the laboratory as a qualitative and quantitative analysis tool. This technique has yet to be fully exploited in a planetary instrument for remote sensing. The characteristic X-ray emissions provide atomic relative abundances. These results are complementary to the molecular composition information obtained from IR, visible, and UV emission spectra. The atomic relative abundances are crucial to understanding the formation and evolution of these bodies. They are also crucial to the proper interpretation of the molecular composition results from the other sensors. The intensities of the characteristic X-ray emissions are sufficiently strong to be measured with an instrument of modest size. Recent developments in X-ray detector technologies and electronic miniaturization have made possible space-flight X-ray imaging and nonimaging spectrometers of high sensitivity and excellent energy resolution that are rugged enough to survive long-duration space missions. Depending on the application, such instruments are capable of resolving elemental abundances of elements from carbon through iron. At the same time, by measuring the bremsstrahlung intensity and energy spectrum, the characteristics of the source electron flux can be determined. We will discuss these concepts, including estimated source strengths, and will describe a small instrument capable of providing this unique channel of information for future planetary missions. We propose to build this instrument using innovative electronics packaging methods to minimize size and weight.

Chenette, D. L.↗