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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

High-resolution X-ray spectroscopy of four active galaxies - Probing the intercloud medium

The focal plane crystal spectrometer (FPCS) on the Einstein Observatory has been used to perform a high-resolution spectroscopic search for oxygen X-ray line emission from four active galaxies: Fairall 9, Mrk 421, Mrk 501, and PKS 0548 - 322. Specifically, O VIII Ly-alpha and Ly-beta, whose unredshifted energies are 653 and 775 eV, respectively, were sought. No narrow-line emission was detected within the energy bands searched. Upper limits are calculated on the line flux from these sources of 30 eV equivalent width and use a photoionization model to place corresponding upper limits on the densities of diffuse gas surrounding the active nuclei. The upper limits on gas density range from about 0.02-50/cu cm and probe various radial distances from the central source. This is the first time high-resolution X-ray spectroscopy has been used to place constraints on the intercloud medium in active galaxies.

Lum, Kenneth S. K.↗
NASA NTRS2004

High Resolution Digital Elevation Models of Pristine Explosion Craters

In order to effectively capture a realistic terrain applicable to studies of cratering processes and landing hazards on Mars, we have obtained high resolution digital elevation models of several pristine explosion craters at the Nevada Test Site. We used the Airborne Terrain Mapper (ATM), operated by NASA's Wallops Flight Facility to obtain DEMs with 1 m spacing and 10 cm vertical errors of 4 main craters and many other craters and collapse pits. The main craters that were mapped are Sedan, Scooter, Schooner, and Danny Boy. The 370 m diameter Sedan crater, located on Yucca Flat, is the largest and freshest explosion crater on Earth that was formed under conditions similar to hypervelocity impact cratering. As such, it is effectively pristine, having been formed in 1962 as a result of a controlled detonation of a 100 kiloton thermonuclear device, buried at the appropriate equivalent depth of burst required to make a simple crater. Sedan was formed in alluvium of mixed lithology and subsequently studied using a variety of field-based methods. Nearby secondary craters were also formed at the time and were also mapped by ATM. Adjacent to Sedan and also in alluvium is Scooter, about 90 m in diameter and formed by a high-explosive event. Schooner (240 m) and Danny Boy (80 m) craters were also important targets for ATM as they were excavated in hard basalt and therefore have much rougher ejecta. This will allow study of ejecta patterns in hard rock as well as engineering tests of crater and rock avoidance and rover trafficability. In addition to the high resolution DEMs, crater geometric characteristics, RMS roughness maps, and other higher-order derived data products will be generated using these data. These will provide constraints for models of landing hazards on Mars and for rover trafficability. Other planned studies will include ejecta size-frequency distribution at the resolution of the DEM and at finer resolution through air photography and field measurements, correlation of ejecta size and composition with radar and visible-thermal IR remote sensing signatures, and comparison of these results with similar measurements of Mars. The final DEMs, ancillary data sets, and derived data products will be made available to the community.

T G Farr↗
NASA NTRS1993

Fluid dynamics and convective heat transfer in impinging jets through implementation of a high resolution liquid crystal technique

A combined convective heat transfer and fluid dynamics investigation in a turbulent round jet impinging on a flat surface is presented. The experimental study uses a high resolution liquid crystal technique for the determination of the convective heat transfer coefficients on the impingement plate. The heat transfer experiments are performed using a transient heat transfer method. The mean flow and the character of turbulent flow in the free jet is presented through five hole probe and hot wire measurements, respectively. The flow field character of the region near the impingement plate plays an important role in the amount of convective heat transfer. Detailed surveys obtained from five hole probe and hot wire measurements are provided. An extensive validation of the liquid crystal based heat transfer method against a conventional technique is also presented. After a complete documentation of the mean and turbulent flow field, the convective heat transfer coefficient distributions on the impingement plate are presented. The near wall of the impingement plate and the free jet region is treated separately. The current heat transfer distributions are compared to other studies available from the literature. The present paper contains complete sets of information on the three dimensional mean flow, turbulent velocity fluctuations, and convective heat transfer to the plate. The experiments also prove that the present nonintrusive heat transfer method is highly effective in obtaining high resolution heat transfer maps with a heat transfer coefficient uncertainty of 5.7 percent.

Kim, K.↗
DOE OSTI2020

Advances in High Resolution Ultrafast Scintillators for Fast timing Applications

Scintillation detectors exhibiting high spatial resolution and fast timing capabilities are of vital importance for synchrotron sources. These detectors may be exposed to a variety of X-ray energies (up to 140 keV) and used in high frame rate applications. Here, we describe the advances in the development of thin-film LuI3:Ce scintillators for higher energy X-ray imaging, with fast timing and high spatial resolution. When grown in a single crystalline form, these scintillators are bright, producing 115 000 photons/MeV. However, to achieve high spatial resolution, these scintillators are grown in thin-film form with a microcolumnar structure, controllable to column diameters of <1-30 mu m. Thus, a much thicker scintillator layer (10 mu m-3 mm or higher) may be grown, providing superior X-ray absorption while achieving high resolutions of 50 mu m or better, at the cost of reduced light yield. To study the timing characteristics of the scintillator, time-resolved X-ray excited optical luminescence (TR-XEOL) was performed on two different sets of three samples of LuI3 at the 1-BM beamline of the Advanced Photon Source at Argonne National Laboratory. Besides, we report timing measurements obtained using a photomultiplier tube (PMT) and oscilloscope at Radiation Monitoring Devices (RMD) Inc. Using the TR-XEOL, we determined the decay constants of LuI3 as a function of Ce doping, recording a fast decay component as low as 3.6 ns (39%), one of the fastest values recorded in inorganic scintillators. This fast decay opens up numerous novel applications, where ultrahigh frame rates are important using synchrotron X-rays. This article will discuss fabrication, characterization, and potential applications for this novel scintillator.

fast timing↗
DOE OSTI2020

High-resolution X-ray spectroscopy of the stellar wind in Vela X-1 during a flare

In this work, we present a ~130 ks observation of the prototypical wind-accreting, high-mass X-ray binary Vela X-1 collected with XMM-Newton at orbital phases between 0.12 and 0.28. A strong flare took place during the observation that allows us to investigate the reaction of the clumpy stellar wind to the increased X-ray irradiation. To examine the wind’s reaction to the flare, we performed both time-averaged and time-resolved analyses of the RGS spectrum and examined potential spectral changes. We focused on the high-resolution XMM-Newton RGS spectra and divided the observation into pre-flare, flare, and post-flare phases. We modeled the time-averaged and time-resolved spectra with phenomenological components and with the self-consistent photoionization models calculated via CLOUDY and XSTAR in the pre-flare phase, where strong emission lines due to resonant transitions of highly ionized ions are seen. In the spectra, we find emission lines corresponding to K-shell transitions in highly charged ions of oxygen, neon, magnesium, and silicon as well as radiative recombination continua (RRC) of oxygen. Additionally, we observe potential absorption lines of magnesium at a lower ionization stage and features identified as iron L lines. The, CLOUDY and XSTAR photoionization models provide contradictory results, either pointing towards uncertainties in theory or possibly a more complex multi-phase plasma, or both. We are able to demonstrate the existence of a plethora of variable narrow features, including the firm detection of oxygen lines and RRC that RGS enables to observe in this source for the first time. We show that Vela X-1 is an ideal source for future high-resolution missions, such as XRISM and Athena.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1991

First results from the faint object camera - High-resolution observations of the central object R136 in the 30 Doradus nebula

R136 is the luminous central object of the giant H II region 30 Doradus in the LMC. The first high-resolution observations of R136 with the Faint Object Camera on board the Hubble Space Telescope are reported. The physical nature of the brightest component R136a has been a matter of some controversy over the last few years. The UV images obtained show that R136a is a very compact star cluster consisting of more than eight stars within 0.7 arcsec diameter. From these high-resolution images a mass upper limit can be derived for the most luminous stars observed in R136.

Weigelt, G.↗
NASA NTRS1989

Toward an image compression algorithm for the high-resolution electronic still camera

Taking pictures with a camera that uses a digital recording medium instead of film has the advantage of recording and transmitting images without the use of a darkroom or a courier. However, high-resolution images contain an enormous amount of information and strain data-storage systems. Image compression will allow multiple images to be stored in the High-Resolution Electronic Still Camera. The camera is under development at Johnson Space Center. Fidelity of the reproduced image and compression speed are of tantamount importance. Lossless compression algorithms are fast and faithfully reproduce the image, but their compression ratios will be unacceptably low due to noise in the front end of the camera. Future efforts will include exploring methods that will reduce the noise in the image and increase the compression ratio.

Nerheim, Rosalee↗
DOE OSTI2022

High-resolution electron time-of-flight spectrometers for angle-resolved measurements at the SQS Instrument at the European XFEL

A set of electron time-of-flight spectrometers for high-resolution angle-resolved spectroscopy was developed for the Small Quantum Systems (SQS) instrument at the SASE3 soft X-ray branch of the European XFEL. The resolving power of this spectrometer design is demonstrated to exceed 10 000 (E/ΔE), using the well known Ne 1s –1 3p resonant Auger spectrum measured at a photon energy of 867.11 eV at a third-generation synchrotron radiation source. At the European XFEL, a width of ~0.5 eV full width at half-maximum for a kinetic energy of 800 eV was demonstrated. It is expected that this linewidth can be reached over a broad range of kinetic energies. An array of these spectrometers, with different angular orientations, is tailored for the Atomic-like Quantum Systems endstation for high-resolution angle-resolved spectroscopy of gaseous samples.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Spin and orbital excitations through the metal-to-insulator transition in Cd 2 Os 2 O 7 probed with high-resolution resonant inelastic x-ray scattering

Here, high-resolution resonant inelastic x-ray scattering measurements (ΔE=46meV) have been performed on Cd 2 Os 2 O 7 through the metal-to-insulator transition (MIT). A magnetic excitation at 125 meV evolves continuously through the MIT, in agreement with recent Raman-scattering results, and provides further confirmation for an all-in all-out magnetic ground state. Asymmetry of this feature is likely a result of coupling between the electronic and the magnetic degrees of freedom. We also observe a broad continuum of interband excitations centered at 0.3 eV energy loss. This is indicative of significant hybridization between Os 5d and O 2p states and the concurrent itinerant nature of the system. In turn, this suggests a possible breakdown of the free-ion model for Cd 2 Os 2 O 7 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1972

L-S coupling interpretation of high-resolution LMM Auger spectra of Cu and Zn.

High-resolution LMM Auger spectra of Cu and Zn obtained by X-ray excitation are shown to contain fine structures which have not been reported previously. An attempt has been made to classify these fine structures in terms of pure L-S coupling of the final vacancies of the atom. The agreement between the calculated and the observed energy separations of the fine-structure lines is good within the accuracy of the Hartree-Fock approximation.

Yin, L.↗
NASA NTRS1972

High resolution spectra of Venus - A review.

The existing high-resolution spectra of Venus show considerable variations in the abundance of CO2. As this is the major constituent of the atmosphere, these day-to-day variations indicate that the effective reflecting cloud layer is undergoing substantial vertical displacements over a relatively short time scale. The published observations indicate that CO is uniformly mixed with the CO2, but that the lines of HF may be formed deeper in the atmosphere and HCl lines considerably deeper. These conclusions are based on extrapolations of laboratory measurements and could be considerably altered by new laboratory measurements made under conditions similar to those near the tropopause in Venus.

Young, L. D. G.↗
NASA NTRS1976

Infrared pyrometer for high resolution surface temperature measurement on rotating turbine blades

A high resolution pyrometer was developed and used to obtain temperature profiles of rotating turbine blades at tip speeds up to 366 meters per second. Surface temperature variations from 920 to 1250 K can be measured and variations over distances of 0.05 cm can be resolved. Temperature profiles were obtained in near real time as hard copies from a computer display terminal. Temperatures measured with the prototype pyrometer and with thermocouples agreed to within 2 percent over the temperature range from 977 to 1144.

Uguccini, O. W.↗
NASA NTRS1976

Infrared pyrometer for high resolution surface temperature measurements on rotating turbine blades

A high resolution pyrometer was developed and used to obtain temperature profiles of rotating turbine blades at tip speeds up to 366 meters per second (1200 fps). Surface temperature variations from 920 to 1250 K (1200 to 1800 F) can be measured and variations over distances of 0.05 cm (0.020 in.) can be resolved. Temperature profiles were obtained in near real time as hard copies from a computer display terminal. Temperatures measured with the prototype pyrometer and with thermocouples agreed to within 2 percent over the temperature range from 977 to 1144 K (1300 to 1600 F).

Uguccini, O. W.↗