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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 NTRS2001

Novel Diffusivity Measurement Technique

A common-path interferometer (CPI) system was developed to measure the diffusivity of liquid pairs. The CPI is an optical technique that can be used to measure changes in the gradient of the refraction index of transparent materials. This system uses a shearing interferometer that shares the same optical path from a laser light source to the final imaging plane. Hence, the molecular diffusion coefficient of liquids can be determined using the physical relations between changes in the optical path length and the liquid phase properties. The data obtained with this interferometer were compared with similar results from other techniques and demonstrated that the instrument is superior in measuring the diffusivity of miscible liquids while keeping the system very compact and robust. CPI can also be used for studies in interface dynamics and other diffusion-dominated-process applications.

Rashidnia, Nasser↗

NASA NTRS1984

The Smallest Sizes of Diffuse Interstellar Clouds

By observing the difference in optical depths between absorption spectra toward the two components of double sources, the variations in opacity over lengths of less than 0.1 up to 10 pc inside diffuse interstellar clouds were measured. Significant variations were detected on scales larger than about 0.2 pc, but not less. This may represent the minimum size for diffuse cloud structure. By comparing the variations of Gaussian fitted line parameters, it was found that variations in the internal velocity field of diffuse clouds explain the data better than tiny independent cloudlets.

Dickey, J. M.↗

NASA NTRS1986

X-ray-selected M dwarfs and the diffuse X-ray background

A systematic optical identification program was carried out for serendipitous X-ray sources discovered by the Einstein Observatory. A total of 104 were detected above the threshold flux of 3 x 10 to the -13th ergs/sq cm per sec in the 114 sq deg survey region; 11 of these 104 sources are dM stars. Including X-ray-selected M dwarfs from the LMC survey, the Medium Sensitivity Survey, and the Einstein Deep Survey, a dwarf M star composite X-ray spectrum was constructed; the best-fit thermal model yields kT = 1.3 + or - 0.3 keV, consistent with typical active star spectra. An M dwarf X-ray luminosity function was also constructed and it is concluded that the integrated contribution to the diffuse soft (0.28-1.0 keV) X-ray background from such stars is less than 10 percent, a factor of more than about 2 lower than previous estimates. This result is consistent with a limit on the dwarf M star contribution derived from a spectral decomposition of the observed X-ray background spectrum.

Caillault, J.-P.↗

NASA NTRS2002

Diffuse X-ray Emission from M101

The total 0.45-2.0 keV luminosity of M101 is 3.1 x 10(exp 39) ergs/s, of which 2.2 x 10(exp 39) ergs/s is due to diffuse emission. Of the diffuse emission, no more than 6% can be due to unresolved point sources such as X-ray binaries, and approx. 11% is due to dwarf stars. The diffuse emission traces the spiral arms and is roughly correlated with the H alpha and FUV (far ultraviolet) emission. The radial distribution closely follows the optical profile. The bulk of the diffuse emission is characterized by a two thermal component spectrum with kT = 0.20,0.75 keV, and the ratios of the emission measures of the two components is roughly constant as a function of both radius and surface brightness. The softer component has a sufficiently large covering factor that the bulk of the emission is likely extra-planar. We find no evidence of an extended axisymmetric X-ray halo, suggesting that any such halo has a strength much smaller than current predictions.

Kuntz, K. D.↗

NASA NTRS1973

The application of far IR lasers to the investigation of the optical properties of materials

The effect of diffusion on the saturation and absorption properties of molecular gases is considered. The analysis starts with a simple derivation of the multi-level rate equations. Incorporating the diffusion term, calculations are carried out both for the homogeneous and inhomogeneous broadening cases. Both graphical and analytical solutions are obtained for the absorption coefficient and the saturation intensity. It is shown that the effect of diffusion is characterized by a diffusion function, which varies inversely with the radius of the beam at low pressures and small beam sizes. The analysis is done in terms of two parameters k1a and k2a, which are simple functions of the intensity of the beam I, the effective relaxation rate w, and the effective diffusion constant D the a is designated as the radius of the beam.

Stafsudd, O. M.↗

NASA NTRS1981

Static diffusion cloud chambers

The chamber geometry and optical arrangement are described. The supersaturation range is given and consists of readings taken at five fixed points: 0.25%, 0.5%, 0.75%, 1.0%, and 1.25%. The detection system is described including light source, cameras, and photocell detectors. The temperature control and the calibration of the chamber are discussed.

Ayers, G.↗

NASA NTRS2003

Diffusivity Measured as a Function of Concentration

Optical diagnostic techniques have become an integral part of many measurements in industrial and research laboratories. Many types of interferometers and their phase-shifted versions have been used to measure optical wave fronts for lens testing and combustion and fluid flow diagnostics. One such instrument is the point diffraction interferometer (PDI), which is considered to be robust because it has a common-path design. However, the PDI is difficult to align and has limited measurement range for liquid phase applications. Interferometry and schlieren techniques have been widely used for many years for gas flow visualization.

Rashidnia, Nasser↗

NASA NTRS1977

Automated array assembly task, phase 1

Various aspects of a sensitivity analysis, in particular, the impact of variations in metal sheet resistivity, metal line width, diffused layer sheet resistance, junction depth, base layer lifetime, optical coating thickness and optical coating refractive index and on process reproducibility for A's diffusion from a polymer dopant source and on module fabrication were studied. Model calculations show that acceptable process windows exist for each of these parameters.

Carbajal, B. G.↗

DOE OSTI2026

Non-classical ion-indiffusion processes in quasi-one-dimensional ionic conductor KTiOPO4

Developments in coercive field engineering and waveguide writing via ion-exchange in the ferroelectric ionic-conductor KTiOPO4 (KTP) have led to breakthroughs within the field of nonlinear optics and quantum photonics. However, the microscopic diffusion dynamics of ion-exchange in KTP are poorly understood and show signs of non-classical diffusion dynamics. The precise control of ion-exchange gradients is critical for developing KTP into a mature, integrated nonlinear optical material but requires a level of control that, in turn, demands a deeper understanding of the ion-exchange process. We employ direct ToF-SIMS mapping to untangle the complex diffusion dynamics of the commonly used ion-exchange dopant ions: Rb, Ba, and K. We map periodic diffusion gradients of two exchanges, one dominated by Rb-ions and the other by Ba-ions. For the first time, we show the interdependent nature of the Ba- and Rb ion in the ion-exchange diffusion gradient. The low incorporation of the Ba ion is mapped and quantified, and dopant–crystal interactions are identified. This work highlights the complex diffusion dynamics of dopants in the KTP structure and lays the foundation for deterministic control of diffusion gradients for the next generation of integrated nonlinear and quantum photonic devices.

Barrett, Laura [ORNL]↗

NASA NTRS1978

Protogalaxy interactions in newly formed clusters - Galaxy luminosities, colors, and intergalactic gas

The role of protogalaxy interactions in galactic evolution is studied during the formation of galaxy clusters. In the early stages of the collapse, coalescent encounters of protogalaxies lead to the development of a galactic luminosity function. Once galaxies acquire appreciable random motions, mutual collisions between galaxies in rich clusters will trigger the collapse of interstellar clouds to form stars. This provides both a source for enriched intracluster gas and an interpretation of the correlation between luminosity and color for cluster elliptical galaxies. Other observational consequences that are considered include optical, X-ray, and diffuse nonthermal radio emission from newly formed clusters of galaxies.

Silk, J.↗

NASA NTRS1985

Reversing Optical Damage In LiNbO3 Switches

One symptom of optical damage in Ti-diffused LiNbO3 directional-coupler switch reversed by temporarily raising input illumination to higher-thannormal power level. Healing phenomenon used to restore normal operation, increase operating-power rating, and stabilize operating characteristics at lower powers. Higher operating power is tolerated after treatment.

Gee, C. M.↗

NASA NTRS1983

Passive remote sensing of ocean optical propagation parameters

A method is described for producing a global data of ocean optical properties through the exploitation of optical remote sensing techniques. The diffuse attenuation, K, and the radiance reflectance factor R sub L, of the ocean surface waters can be derived from the radiance data provided by the Coastal Zone Color Scanner and compiled into a computer based atlas of these properties. While these remotely sensed values can only be directly related to the water properties in the first or upper attenuation length, extensive in water measurements have demonstrated that a useful correlation exists between the K that applies to the upper attenuation length, for example, and the mean K over the upper 100 or 200 meters of the ocean. Such an empirical finding greatly enhances the usefulness of this remotely sensed propagation parameter. Examples of the type of information being produced and archived for the atlas are presented.

Austin, R. W.↗

NASA NTRS1987

Oscillator strengths for visible and ultraviolet observations of interstellar molecules

Optical observations of molecules in diffuse interstellar clouds are discussed. The role of oscillator strengths in determining cloud properties such as densities, temperatures, and particle and photon fluxes is examined. The use of an emission technique, molecular and atomic lifetime measurements, and absorption measurements to estimate oscillator strengths is described. It is noted that the lifetime and absorption measurements are more advantageous than the emission technique to estimate oscillator strengths.

Smith, Peter L.↗

NASA NTRS1993

A ROSAT high resolution x ray image of NGC 1068

The soft x ray properties of the Seyfert 2 galaxy NGC 1068 are a crucial test of the 'hidden Seyfert 1' model. It is important to determine whether the soft x rays come from the nucleus, or from a number of other possible regions in the circumnuclear starburst disk. We present preliminary results of a ROSAT HRI observation of NGC 1068 obtained during the verification phase. The fraction of x rays that can be attributed to the nucleus is about 70 percent so the 'soft x ray problem' remains. There is also significant diffuse x ray flux on arcminute scales, which may be related to the 'diffuse ionized medium' seen in optical emission lines, and the highly ionized Fe K(alpha) emission seen by BBXRT.

Halpern, J.↗

NASA NTRS1992

COBE anisotropy from supercluster gas

It is suggested that the microwave background anisotropy detected by the COBE DMR might be dominated not by the direct gravitational effect of primordial fluctuations in the last scattering surface, but by scattering off of moving electrons in optically thin, nearby superclusters. Hot diffuse clouds of ionized gas created during supercluster collapse produce Sunyaev-Zel'dovich and Doppler background anisotropy whose properties may closely mimic those of primordial anisotropy in current data. Strategies for and difficulties in separating the effects are discussed, based on the anisotropy spectrum, autocorrelation, correlation with galaxy catalogs, X-ray emission, and integrated spectral distortions.

Hogan, Craig J.↗

NASA NTRS1993

Mineralogy of three slightly palagonitized basaltic tephra samples from the summit of Mauna Kea, Hawaii

The paper characterizes the mineralogy and spectral properties of three slightly palagonitized basaltic tephra samples collected near the summit of Mauna Kea in order to contribute to the basis for inferring mineralogy and processes for Martian surface materials. The mineralogy of size fractions of these samples is examined by diffuse reflectance and FIR spectroscopy, optical microscopy, X-ray diffraction, Moessbauer spectroscopy, magnetic analysis, EMPA, TEM, and SEM. For the 20-1000 micron size fraction, sample HWMK11 (red) is essentially completely oxidized and has a hematite (Ti-hematite) pigment dispersed throughout the silicate matrix. Sample HWMK12 (black) has the lowest proportion of ferric-bearing phases and is thus least weathered. For HWMK11, the amount of hematite is essentially constant, and mica is present only in the coarse clay-sized fraction; smectites are low in structural Fe.

Golden, D. C.↗

NASA NTRS2002

P1 Nonconforming Finite Element Method for the Solution of Radiation Transport Problems

The simulation of radiation transport in the optically thick flux-limited diffusion regime has been identified as one of the most time-consuming tasks within large simulation codes. Due to multimaterial complex geometry, the radiation transport system must often be solved on unstructured grids. In this paper, we investigate the behavior and the benefits of the unstructured P(sub 1) nonconforming finite element method, which has proven to be flexible and effective on related transport problems, in solving unsteady implicit nonlinear radiation diffusion problems using Newton and Picard linearization methods. Key words. nonconforrning finite elements, radiation transport, inexact Newton linearization, multigrid preconditioning

Kang, Kab S.↗

NASA NTRS2016

Connecting the Interstellar Gas and Dust Properties in Distant Galaxies Using Quasar Absorption Systems

Gas and dust grains are fundamental components of the interstellar medium and significantly impact many of the physical processes driving galaxy evolution, such as star-formation, and the heating, cooling, and ionization of the interstellar material. Quasar absorption systems (QASs), which trace intervening galaxies along the sightlines to luminous quasars, provide a valuable tool to directly study the properties of the interstellar gas and dust in distant, normal galaxies. We have established the presence of silicate dust grains in at least some gas-rich QASs, and find that they exist at higher optical depths than expected for diffuse gas in the Milky Way. Differences in the absorption feature shapes additionally suggest variations in the silicate dust grain properties, such as in the level of grain crystallinity, from system-to-system. We present results from a study of the gas and dust properties of QASs with adequate archival IR data to probe the silicate dust grain properties. We discuss our measurements of the strengths of the 10 and 18 micron silicate dust absorption features in the QASs, and constraints on the grain properties (e.g., composition, shape, crystallinity) based on fitted silicate profile templates. We investigate correlations between silicate dust abundance, reddening, and gas metallicity, which will yield valuable insights into the history of star formation and chemical enrichment in galaxies.

Aller, Monique C.↗