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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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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Imaging of spatial distributions of the millimeter wave intensity by using the Visible Continuum Radiation from a discharge in a Cs–Xe mixture. Part II: Demonstration of application capabilities of the technique

The paper presents the second part of the review on a high-sensitive technique for time-resolved imaging and measurements of the 2D intensity profiles of millimeter-wave radiation by means of Visible Continuum Radiation emitted by the positive column of a medium-pressure Cs-Xe DC Discharge (VCRD method). The first part of the review was focused on the operating principles and fundamentals of this new technique [Plasma Phys. Rep. 43, 253 (2017)]. The second part of the review focuses on experiments demonstrating application of this imaging technique to measure the parameters of radiation at the output of moderate-power millimeter-wave sources. In particular, the output waveguide mode of a moderate-power W-band gyrotron with a pulsed magnetic field was identified and the relative powers of some spurious modes at the outputs of this gyrotron and a pulsed D-band orotron were evaluated. The paper also reviews applications of the VCRD technique for real-time imaging and nondestructive testing with a frame rate of higher than 10 fps by using millimeter waves. Shadow projection images of objects opaque and transparent for millimeter waves have been obtained using pulsed watt-scale millimeter waves for object illumination. Near video frame rate millimeter-wave shadowgraphy has been demonstrated. It is shown that this technique can be used for single-shot screening (including detection of concealed objects) and time-resolved imaging of time-dependent processes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Visible supercontinuum radiation of light bullets in the femtosecond filamentation of IR pulses in fused silica

We report experimental and theoretical investigations of visible supercontinuum generation in the formation of light bullets in a filament produced by IR pulses. In the filamentation of a 1700 – 2200 nm pulse in fused silica, bright tracks are recorded resulting from the recombination glow of carriers in the laser plasma produced by a sequence of light bullets and from the scattering in silica of the visible supercontinuum generated by the light bullets. It is found that the formation of a light bullet is attended with an outburst of a certain portion of supercontinuum energy in the visible range. The energy outburst is the same for all bullets in the sequence and becomes smaller with increasing pulse wavelength. (extreme light fields and their applications)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Rattling of Oxygen Ions in a Sub-Nanometer-Sized Cage Converts Terahertz Radiation to Visible Light

A simple and robust approach to visualization of terahertz (THz) light would open up opportunities to couple physical phenomena that occur at fundamentally different energy scales. Here we demonstrate how nanoscale cages of Ca 12 Al 14 O 33 crystal enable a novel method for conversion THz radiation to visible light. These crystallographic cages contain weakly bonded oxygen ions and give rise to a low-energy conduction band that can populated with localized yet mobile electrons. THz light excites a nearly stand-alone rattling motion of the encaged species, which promotes electron transfer from them to the neighboring cages. When the power of THz light reaches tens of watts, the coupling between forced rattling in the confined space, electronic excitation and ionization of oxygen species and corresponding recombination processes result in emission of bright visible light.

Toda, Yoshitake↗
NASA NTRS1974

UCLA International Conference on Radiation and Remote Probing of the Atmosphere, University of California, Los Angeles, Calif., August 28-30, 1973, Proceedings

Approaches for solving multiple scattering problems in planetary atmospheres are considered along with the solution of the radiative transfer theory problems by the Monte Carlo method, the radiative transfer of visible radiation in turbid atmospheres, aspects of scattering and absorption from poly-dispersed aerosols, and multiple scattering in cloud layers. Other subjects discussed include particulate sizes from polarization measurements, lidar observations of atmospheric particulate content, methods of calculating infrared transfer, molecular absorption parameters in atmospheric modelling, and infrared remote sounding. The influence of the atmosphere on spectral radiance and contrasts of natural formations measured from space is investigated and analytical results for radiative transfer in thick atmospheres are presented. Individual items are announced in this issue.

Kuriyan, J. G.↗
NASA NTRS1996

A Model of Radiative and Conductive Energy Transfer in Planetary Regoliths

The thermal regime in planetary regoliths involves three processes: propagation of visible radiation, propagation of thermal radiation, and thermal conduction. The equations of radiative transfer and heat conduction are formulated for particulate media composed of anisotropically scattering particles. Although the equations are time dependent, only steady state problems are considered in this paper. Using the two-stream approximation, solutions are obtained for two cases: a layer of powder heated from below and an infinitely thick regolith illuminated by visible radiation. Radiative conductivity, subsurface temperature gradients, and the solid state greenhouse effect all appear intrinsically in the solutions without ad hoc additions. Although the equations are nonlinear, approximate analytic solutions that are accurate to a few percent are obtained. Analytic expressions are given for the temperature distribution, the optical and thermal radiance distributions, the hemispherical albedo, the hemispherical emissivity, and the directional emissivity. Additional applications of the new model to three problems of interest in planetary regoliths are presented by Hapke.

Hapke, Bruce↗
DOE OSTI2014

Soft chemical synthesis of Ag{sub 3}SbS{sub 3} with efficient and recyclable visible light photocatalytic properties

Highlights: • Highly crystalline Ag{sub 3}SbS{sub 3} synthesized using soft chemical approach. • First time report of photocatalytic activity of Ag{sub 3}SbS{sub 3}. • Ag{sub 3}SbS{sub 3} degraded the harmful organic dyes rapidly under visible radiation. • Pseudo first order kinetics have been followed in these sets of reactions. • Up to 90% of Methylene Blue degraded even after 4th cycle of catalyst reuse. • Structure of catalyst is intact after reuse. • As the catalyst is heavy, its separation after use is quite simple. - Abstract: Application of Ag{sub 3}SbS{sub 3}, obtained by soft chemical approach involving rapid reaction of air stable metal–thiourea complexes in ethylene glycol medium, as visible light photocatalyst for the degradation of dye solutions was investigated. Ag{sub 3}SbS{sub 3} was confirmed by high resolution powder X-ray diffraction pattern and its no defined morphology was present in SEM images. From UV–vis spectroscopy measurements, optical band gap of 1.77 eV was deduced for Ag{sub 3}SbS{sub 3}. Rapid degradation kinetics and recyclability was exhibited by Ag{sub 3}SbS{sub 3} towards Methylene Blue, Methyl Orange, Malachite Green, and Rhodamine 6G dye solutions under visible radiation. All these processes followed pseudo first order kinetics. High surface area (6.39 m{sup 2}/g), with mesopores (3.81 nm), arising from solvent mediated synthesis of Ag{sub 3}SbS{sub 3} has been correlated to its catalytic activity.

36 MATERIALS SCIENCE↗
DOE OSTI2016

X-ray optical system for imaging laser plumes with a spatial resolution of up to 70 nm

We consider an X-ray optical system which permits obtaining laser plume images at a wavelength of 13.5 nm with a resolution of up to 70 nm. The X-ray optical system comprises an X-ray Schwarzschild objective made up of two aspherical multilayer mirrors, a scintillator (YAG : Ce ceramics), which converts X-rays to the visible radiation, and a visible-optical system, which images the scintillator surface onto a CCD camera. The spatial resolution of the system is limited by the resolution of the optical system (0.7 μm) and the magnification (10{sup ×}) of the X-ray objective and is as high as 70 nm. The effect of Schwarzschild objective mirror shapes on the spatial resolution is analysed. The profile of concave mirror aspherisation is considered, which provides the attainment of the diffraction-limited quality of the objective. Data are given for the quantum efficiency of the system at a wavelength of 13.5 nm. We describe the experimental test bench intended for studying the developed X-ray optical system and outline the first experimental data which illustrate its efficiency. Owing to the natural division into the 'X-ray' and 'visible' parts, the optical system under discussion permits an easy change of the magnification and the field of view without realigning the X-ray optical elements. The wavelength may be varied in a range between 3 and 40 nm by changing the multilayer mirrors. (extreme laser radiation: physics and fundamental applications)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1971

High contrast cathode ray tube

A layer of material is described, which contains fine grains of phosphor material stimulated by electrons to produce visible radiation. The layer, which also contains fine grains of cobalt oxide, is deposited on the glass screen of a cathode ray tube to provide high contrast, by absorbing most of the visible radiation which is directed to the layer through the screen, while not materially affecting the visible light which the phosphor material produces in response to the electron stimulation.

Lisovicz, E. J.↗
DOE OSTI2017

Imaging of spatial distributions of the millimeter wave intensity by using visible continuum radiation from a discharge in a Cs–Xe mixture. Part I: Review of the method and its fundamentals

The first part of the review is presented which is dedicated to the time-resolved method of imaging and measuring the spatial distribution of the intensity of millimeter waves by using visible continuum (VC) emitted by the positive column (PC) of a dc discharge in a mixture of cesium vapor with xenon. The review focuses on the operating principles, fundamentals, and applications of this new technique. The design of the discharge tube and experimental setup used to create a wide homogeneous plasma slab with the help of the Cs–Xe discharge at a gas pressure of 45 Torr are described. The millimeter-wave effects on the plasma slab are studied experimentally. The mechanism of microwave-induced variations in the VC brightness and the causes of violation of the local relation between the VC brightness and the intensity of millimeter waves are discussed. Experiments on the imaging of the field patterns of horn antennas and quasi-optical beams demonstrate that this technique can be used for good-quality imaging of millimeter-wave beams in the entire millimeter-wavelength band. The method has a microsecond temporal resolution and a spatial resolution of about 2 mm. Energy sensitivities of about 10 μJ/cm{sup 2} in the Ka-band and about 200 μJ/cm{sup 2} in the D-band have been demonstrated.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Gamma-ray bounds from EAS detectors and heavy decaying dark matter constraints

The very high energy Galactic γ-ray sky is partially opaque in the (0.1–10) PeV energy range. In the light of the recently detected high energy neutrino flux by IceCube, a comparable very high energy γ-ray flux is expected in any scenario with a sizable Galactic contribution to the neutrino flux. Here we elaborate on the peculiar energy and anisotropy features imposed upon these very high energy γ-rays by the absorption on the cosmic microwave background photons and Galactic interstellar light. As a notable application of our considerations, we study the prospects of probing the PeV-scale decaying DM scenario, proposed as a possible source of IceCube neutrinos, by extensive air shower (EAS) cosmic ray experiments. In particular, we show that anisotropy measurements at EAS experiments are already sensitive to τ{sub DM}∼O(10{sup 27}) s and future measurements, using better gamma/hadron separation, can improve the limit significantly.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1977

An infrared upconverter for astronomical imaging

An imaging upconverter has been constructed which is suitable for use in the study of the thermal 10-micron radiation from astronomical sources. The infrared radiation is converted to visible radiation by mixing in a 1-cm-long proustite crystal. The phase-matched 2-kayser bandpass is tunable from 9 to 11 microns. The conversion efficiency is 2 by 10 to the -7th power and the field of view of 40 arc seconds on the sky contains several hundred picture elements, approximately diffraction-limited resolution in a large telescope. The instrument has been used in studies of the sun, moon, Mercury, and VY Canis Majoris.

Boyd, R. W.↗
NASA NTRS1989

The spatial distribution of infrared radiation from visible reflection nebulae

The emission at IRAS 12 and 25 micron bands of reflection nebulae is far in excess of that expected from the longer wavelength equilibrium thermal emission. The excess emission in the IRAS 12 micron band is a general phenomenon, seen in various components of interstellar medium such as IR cirrus clouds, H II regions, atomic and molecular clouds, and also normal spiral galaxies. This excess emission has been attributed to UV excited fluorescence in polycyclic aromatic hydrocarbon (PAH) molecules or to the effect of temperature fluctuations in very small grains. Results are presented of studies of IRAS data on reflection nebulae selected from the van den Bergh reflection nebulae sample. Detailed scans of flux ratio and color temperature across the nebulae were obtained in order to study the spatial distribution of IR emission. A model was used to predict the spatial distribution of IR emission from dust grains illuminated by a B type star. The model was also used to explore the excitation of the IRAS 12 micron band emission as a function of stellar temperature. The model predictions are in good agreement with the analysis of reflection nebulae, illuminated by stars with stellar temperature ranging from 21,000 down to 3,000 K.

Luan, Ling↗
DOE OSTI2013

Characterization and calibration of compact array spectrometers in the ultraviolet spectral region

Array-based spectrometers, with their compact size, low weight, low cost, and fast measurement time, are now frequently used in place of both conventional single-channel scanning monochromators, and broadband meters. Their rapid measurement capability makes them an attractive option for routine solar UV spectral measurements, where shortterm variability in signal is a challenge. However, compactness, portability, low cost and high speed are achieved at the expense of the spectrometer's optical and electronic performance. Thus such spectrometers are more prone to measurement error from environmental changes, and more prone to other intrinsic sources of error such as stray light and detector non-linearity, which significantly affect solar UV measurements, than a scanning monochromator. The effects of stray light and non-linearity can be reduced either by improved optical and detector design or by a detailed spectrometer characterization. We present in this paper our investigation of the performance of three different commercial array spectrometers: two mini-spectrometers, and a more elaborate array spectrometer with an on-board image amplifier device. These were tested for a subset of performance parameters: their wavelength accuracy and stability, electronic linearity, responsivity linearity, stray light sensitivity, and mechanical stability and repeatability. With all three spectrometers we found that these parameters, particularly but not limited to stray light, had a significant impact on the measurement of the incoming optical radiation. This meant that, without characterization, the instruments would be unable to accurately measure the UV component of any source with significant visible radiation. We discuss various simple and low-cost solutions for improving the performance of these instruments, and providing a rigorous calibration using a straightforward set-up including optical filters and the quasi-monochromatic light from a double monochromator.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1980

Radiative energy output of the 5 September 1973 flare

Measurements of the radiative energy output of the solar flare of Sept. 5, 1973, over a wavelength range of more than ten decades, from below 1 A to above 1 m are presented. Observations of soft X-rays (0.5-20 A), XUV and EUV lines (171-1863 A) and EUV continua (1400-1960 A), H alpha radiation, visible lines and continua (3700-8700 A) and radio emission (centimeter to meter wavelengths) were obtained concurrently by Skylab and ground-based instruments. Estimates of power output at flare maximum are obtained for the observed wavelengths with uncertainty of at least half an order of magnitude, due to corresponding uncertainties in EUV and visible fluxes. Taking into account energy radiated at unobserved wavelengths and the characteristic time of the best-reduced data (the soft X-ray), calculations indicate a total radiated flare energy of approximately 4 x 10 to the 29th erg.

Canfield, R. C.↗
DOE OSTI2012

Visible light emission and energy transfer processes in Sm-doped nitride films

Even though the great interest in studying the near-infrared light emission due to Er{sup 3+} ions for telecommunication purposes, efficient visible radiation can be achieved from many different rare-earth (RE) ions. In fact, visible and/or near-infrared light emission takes place in RE-doped wide bandgap semiconductors following either photon or electron excitation, suggesting their technological potential in devices such as light-emitting diodes (LED's) and flat-panel displays, for example. Taking into consideration these aspects, the present contribution reports on the investigation of AlN, BeN, GeN, and SiN thin films doped with samarium. The samples were prepared by sputtering and as a result of the deposition method and conditions they present an amorphous structure and Sm concentrations in the low 0.5 at. %. After deposition, the samples were submitted to thermal annealing treatments and investigated by different spectroscopic techniques. A detailed examination of the experimental data allowed to identify optical transitions due to Sm{sup 3+} and Sm{sup 2+} ions as well as differences in their mechanisms of photon excitation and recombination. Moreover, it is shown that the Sm-related spectral features and emission intensity are susceptible, respectively, to the atomic environment the Sm{sup 3+}/Sm{sup 2+} ions experience and to the presence of non-radiative recombination centers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗