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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 1,711 records · Page 95
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

An emerging network storage management standard: Media error monitoring and reporting information (MEMRI) - to determine optical tape data integrity

Sophisticated network storage management applications are rapidly evolving to satisfy a market demand for highly reliable data storage systems with large data storage capacities and performance requirements. To preserve a high degree of data integrity, these applications must rely on intelligent data storage devices that can provide reliable indicators of data degradation. Error correction activity generally occurs within storage devices without notification to the host. Early indicators of degradation and media error monitoring 333 and reporting (MEMR) techniques implemented in data storage devices allow network storage management applications to notify system administrators of these events and to take appropriate corrective actions before catastrophic errors occur. Although MEMR techniques have been implemented in data storage devices for many years, until 1996 no MEMR standards existed. In 1996 the American National Standards Institute (ANSI) approved the only known (world-wide) industry standard specifying MEMR techniques to verify stored data on optical disks. This industry standard was developed under the auspices of the Association for Information and Image Management (AIIM). A recently formed AIIM Optical Tape Subcommittee initiated the development of another data integrity standard specifying a set of media error monitoring tools and media error monitoring information (MEMRI) to verify stored data on optical tape media. This paper discusses the need for intelligent storage devices that can provide data integrity metadata, the content of the existing data integrity standard for optical disks, and the content of the MEMRI standard being developed by the AIIM Optical Tape Subcommittee.

Podio, Fernando↗
NASA NTRS2000

Bolometric Array Detectors for Space-Borne Astronomy

Funding from the NASA Innovative Research Grant was used to develop bolometric detectors. As described in the proposal, silicon nitride micromesh ('spider-web') absorbers had been demonstrated at U.C. Berkeley but not developed to be flight-worthy devices. We proceeded to first fabricate bolometers with Neutron Transmutation Doped (NTD) Ge thermistors that demonstrated high optical coupling (Church et al. 1996) and were developed for a ground-based millimeter-wave receiver (Mauskopf et al. 1997). The next generation of devices used In bump-bonded thermistors to achieve devices with performance product NEP*sqrt(tau) = 3e - 18 j at 300 mK, demonstrating a full order of magnitude improvement over pervious devices. These devices achieved an NEP = 1e-18 W/rtHz (Murray et al. 1996) as promised in the proposal. Sensitivities as good as 1e - 19 W/rtHz appear achievable with the silicon nitride architecture (Bock et al. 1997). Finally, arrays of micromesh bolometers were shown to be feasible in the last year of the program by etching a large number of devices on a single silicon wafer (75 mm). Full arrays were subsequently demonstrated for selection on the ESA/NASA Far-Infrared Space Telescope (FIRST) in competition with detectors provided by CEA in France and GSFC in the US Micromesh bolometer arrays are now baselined for both the ESA/NASA Planck and FIRST missions.

Lange, Andrew E.↗
NASA NTRS2008

Linear FMCW Laser Radar for Precision Range and Vector Velocity Measurements

An all fiber linear frequency modulated continuous wave (FMCW) coherent laser radar system is under development with a goal to aide NASA s new Space Exploration initiative for manned and robotic missions to the Moon and Mars. By employing a combination of optical heterodyne and linear frequency modulation techniques and utilizing state-of-the-art fiber optic technologies, highly efficient, compact and reliable laser radar suitable for operation in a space environment is being developed. Linear FMCW lidar has the capability of high-resolution range measurements, and when configured into a multi-channel receiver system it has the capability of obtaining high precision horizontal and vertical velocity measurements. Precision range and vector velocity data are beneficial to navigating planetary landing pods to the preselected site and achieving autonomous, safe soft-landing. The all-fiber coherent laser radar has several important advantages over more conventional pulsed laser altimeters or range finders. One of the advantages of the coherent laser radar is its ability to measure directly the platform velocity by extracting the Doppler shift generated from the motion, as opposed to time of flight range finders where terrain features such as hills, cliffs, or slopes add error to the velocity measurement. Doppler measurements are about two orders of magnitude more accurate than the velocity estimates obtained by pulsed laser altimeters. In addition, most of the components of the device are efficient and reliable commercial off-the-shelf fiber optic telecommunication components. This paper discusses the design and performance of a second-generation brassboard system under development at NASA Langley Research Center as part of the Autonomous Landing and Hazard Avoidance (ALHAT) project.

Pierrottet, Diego↗
DOE OSTI2024

Status of h-BN quasi-bulk crystals and high efficiency neutron detectors

III-nitrides have fomented a revolution in the lighting industry and are poised to make a huge impact in the field of power electronics. In the III-nitride family, the crystal growth and use of hexagonal BN (h-BN) as an ultrawide bandgap (UWBG) semiconductor are much less developed. Bulk crystals of h-BN produced by the high-temperature/high-pressure and the metal flux solution methods possess very high crystalline and optical qualities but are impractical to serve as substrates or for device implementation as their sizes are typically in millimeters. The development of crystal growth technologies for producing thick epitaxial films (or quasi-bulk or semi-bulk crystals) in large wafer sizes with high crystalline quality is a prerequisite for utilizing h-BN as an UWBG electronic material. Compared to traditional III-nitrides, BN has another unique application as solid-state neutron detectors, which however, also require the development of quasi-bulk crystals to provide high detection efficiencies because the theoretical efficiency (ηi) relates to the detector thickness (d) by ηi=1−e−dλ, where λ denotes the thermal neutron absorption length which is 47 μm (237 μm) for 10B-enriched (natural) h-BN. We provide an overview and recent progress toward the development of h-BN quasi-bulk crystals via hydride vapor phase epitaxy (HVPE) growth and the attainment of thermal neutron detectors based on 100 μm thick 10B-enriched h-BN with a record efficiency of 60%. The thermal neutron detection efficiency was shown to enhance at elevated temperatures. Benchmarking the crystalline and optical qualities of h-BN quasi-bulk crystals with the state-of-the-art mm-sized bulk crystal flakes and 0.5 μm thick epitaxial films identified that reducing the density of native defects such as vacancies remains the most critical task for h-BN quasi-bulk crystal growth by HVPE.

Physics↗
DOE OSTI2021

Recent Advances in Vertically Aligned Nanocomposites with Tunable Optical Anisotropy: Fundamentals and Beyond

Developing reliable and tunable metamaterials is fundamental to next-generation optical-based nanodevices and computing schemes. In this review, an overview of recent progress made with a unique group of ceramic-based functional nanocomposites, i.e., vertically aligned nanocomposites (VANs), is presented, with the focus on the tunable anisotropic optical properties. Using a self-assembling bottom-up deposition method, the as-grown VANs present great promise in terms of structural flexibility and property tunability. Such broad tunability of functionalities is achieved through VAN designs, material selection, growth control, and strain coupling. The as-grown multi-phase VAN films also present enormous advantages, including wafer scale integration, epitaxial quality, sharp atomic interface, as well as designable materials and geometries. This review also covers the research directions with practical device potentials, such as multiplex sensing, high-temperature plasmonics, magneto-optical switching, as well as photonic circuits.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Spectral interferometry-based microwave-frequency vibrometry for integrated acoustic wave devices

Microwave phononics is a promising platform for sensing, computing, and quantum information science; thus, sensitive and high-throughput characterization tools are needed not only for device verification and optimization but also for revealing transient and nonlinear dynamics. Existing interferometric optical vibrometers for 2D mapping are challenged by operating point stabilization, surface reflectivity contrast, and long acquisition time. Here, we use spectral interferometry, which is insensitive to these factors and utilizes a continuous raster scanning scheme for vibration mapping with high throughput. We intensity-modulate our broadband light source with an electro-optic modulator to resolve vibrations at microwave frequencies. Our system requires no fast photodetector or digitizer operating in the microwave frequency range. We image the 1 GHz vibration field of a 300 × 150 µm 2 area of an entire surface acoustic wave device in 10 min with simultaneous surface profilometry. Our system has a vibration sensitivity of 120 fm/sqrt(Hz) and a linear throughput of 0.77 mm/s on the chip surface. The technique offers capabilities for characterizing a wide range of acoustic wave and micromechanical devices to better understand their behavior and performance.

47 OTHER INSTRUMENTATION↗
NASA NTRS1988

Optical Detection Of Cryogenic Leaks

Conceptual system identifies leakage without requiring shutdown for testing. Proposed device detects and indicates leaks of cryogenic liquids automatically. Detector makes it unnecessary to shut equipment down so it can be checked for leakage by soap-bubble or helium-detection methods. Not necessary to mix special gases or other materials with cryogenic liquid flowing through equipment.

Wyett, Lynn M.↗
NASA NTRS1989

Monolithically integrated two-dimensional arrays of optoelectronic threshold devices for neural network applications

A monolithic 10 x 10 two-dimensional array of 'optical neuron' optoelectronic threshold elements for neural network applications has been designed, fabricated, and tested. Overall array dimensions are 5 x 5 mm, while the individual neurons, composed of an LED that is driven by a double-heterojunction bipolar transistor, are 250 x 250 microns. The overall integrated structure exhibited semiconductor-controlled rectifier characteristics, with a breakover voltage of 75 V and a reverse-breakdown voltage of 60 V; this is attributable to the parasitic p-n-p transistor which exists as a result of the sharing of the same n-AlGaAs collector between the transistors and the LED.

Kim, J. H.↗
NASA NTRS1994

The RSA survey of dwarf galaxies, 1: Optical photometry

We present detailed surface photometry, based on broad B-band charge coupled device (CCD) images, of about 80 dwarf galaxies. Our sample represents approximately 10% of all dwarf galaxies identified in the vicinity of Revised Shapley-Ames (RSA) galaxies on high resolution blue photographic plates, referred to as the RSA survey of dwarf galaxies. We derive global properties and radial surface brightness profiles, and examine the morphologies. The radial surface brightness profiles of dwarf galaxies, whether early or late type, display the same varieties in shape and complexity as those of classical giant galaxies. Only a few are well described by a pure r(exp 1/4) law. Exponential profiles prevail. Features typical of giant disk galaxies, such as exponential profiles with a central depression, lenses, and even, in one case (IC 2041), a relatively prominent bulge are also found in dwarf galaxies. Our data suggest that the central region evolves from being bulge-like, with an r(exp 1/4) law profile, in bright galaxies to a lens-like structure in dwarf galaxies. We prove detailed surface photometry to be a helpful if not always sufficient tool in investigating the structure of dwarf galaxies. In many cases kinematic information is needed to complete the picture. We find the shapes of the surface brightness profiles to be loosely associated with morphological type. Our sample contains several new galaxies with properties intermediate between those of giant and dwarf ellipticals (but no M32-like objects). This shows that such intermediate galaxies exist so that at least a fraction of early-type dwarf ellipticals is structurally related to early-type giants instead of belonging to a totally unrelated, disjunct family. This supports an origin of early-type dwarf galaxies as originally more massive systems that acquired their current morphology as a result of substantial, presumable supernova-driven, mass loss. On the other hand, several early-type dwarfs in our sample are merger candidates. Merger events may lead to anisotropic velocity distributions in systems of any luminosity, including dwarfs. The RSA sample of dwarf galaxies is more likely to contain mergers because, in contrast to earlier dwarf galaxy surveys that have focused on clusters and rich groups of galaxies, the RSA dwarfs are typically located in low density environments. The occurrence of mergers among dwarf galaxies is of interest in connection with the rapid evolution of faint blue galaxy counts at redshift z less than 1 which suggests that dwarf galaxies were about five times more numerous in the recent past. Finally, our sample contains several examples of late-type dwarfs and 'transition' types that are potential precursors of nucleated early-type dwarfs. All the above processes--mass loss, mergers, astration--are likely to have contributed to the formation of the current population of diffuse early-type dwarfs. A few new redshifts of dwarf galaxies are reported in this paper.

Vader, J. Patricia↗
DOE OSTI2022

Structure-controlled intramolecular charge transfer in asymmetric pyrene-based luminogens: synthesis, characterization and optical properties

Full-colour emitting materials have been widely studied driven by their promising potential application in fluorescence imaging and optoelectronic devices. In this paper, the synthesis and charactization of four asymmetric D–A type pyrene-based luminogens 2 is presented. Here, the experimental results revealed that this type of pyrene derivative possesses tunable optical properties by introducing D/A groups at the 1-, 3-positions and K-region (5-position) of the pyrene core. Wide emission bands from deep blue (429 nm) to yellow (567 nm) were obtained in different solutions or states. Combined with the theoretical calculations, this work provides an efficient strategy to develop pyrene-based full-colour photoelectric materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Evaluation of accuracy and resolution of the electron beam profile scanner at the Fermilab Main Injector

The objective of this work is to assess the accuracy of measurements made by the Electron Beam Profile Scanner (EBPS), which captures the trajectory of an electron beam with and without a proton beam present. The proton beam induces deflection in the electron beam, which is influenced by proton charges.For high-resolution images, the probe beam needs to be of high intensity, small diameter, and small divergence, evaluated using a YAG screen and an optical transition radiation (OTR) screen. Additionally, the point spread function (PSF) will be calculated to characterize the optical system's properties using ZEMAX software. The capabilities of the Hamamatsu Charge-Injection Device (CID) camera and Kimball Physics electron gun (e-gun) will be considered for accuracy.

Mwaniki, Matilda [IIT, Chicago; Fermilab]↗
NASA NTRS1973

Imaging techniques in X-ray astronomy.

Some of the imaging problems encountered in space-borne X-ray astronomy are reviewed, along with the techniques considered for their solution. Following a discussion of X-ray focussing and X-ray image processing, the development of X-ray imaging devices is surveyed. It is shown that the imaging devices that will be used in X-ray astronomy will take advantage of developments intended for infrared and optical astronomy. The special requirements of X-ray observation - especially, single photon detection and high time resolution - rule out the use of existing devices, particularly because of readout problems.

Gursky, H.↗
DOE OSTI2020

Optical Absorption-Based In Situ Characterization of Halide Perovskites

Halide perovskites have emerged as materials for high-performance optoelectronic devices. Often, progress made to date in terms of higher efficiency and stability is based on increasing material complexity, i.e., formation of multicomponent halide perovskites with multiple cations and anions. In this review article, the use of in situ optical methods, namely, photoluminescence (PL) and UV-vis, that provide access to the relevant time and length scales to ascertain chemistry–property relationships by monitoring evolving properties is discussed. Additionally, because halide perovskites are electron/ion conductors and prone to solid-state ion transport under various external stimuli, application of these optical methods in the context of ionic movement is described to reveal mechanistic insights. In conclusion, examples of using in situ PL and UV-vis to study degradation and phase transitions are reviewed to demonstrate the wealth of information that can be obtained regarding many different aspects of ongoing research activities in the field of halide perovskites.

36 MATERIALS SCIENCE↗
NASA NTRS1993

Fiber-Optic Discriminator Stabilizes Microwave Oscillator

New fiber-optic delay line discriminator enables stabilization of oscillators directly at microwave output frequency, eliminating need for frequency multiplication. Discriminator is wide-band device, capable of stabilizing outputs of frequency-agile microwave sources over multigigahertz tuning ranges. Use of advanced fiber-optic delay line with wider bandwidth and low noise predicted to yield corresponding improvements in phase-noise performance.

Logan, Ronald T., Jr.↗
DOE OSTI2022

Optical bistability in PECVD silicon-rich nitride

We present a study of optical bi-stability in a 3.02 refractive index at 1550nm plasma enhanced chemical vapor deposition (PECVD) silicon-rich nitride (SRN) film, as it pertains to bi-stable switching, memory applications, and thermal sensing applications. In this work we utilize an SRN ring resonator device, which we first characterize at low-power and then compare thermo-optic coefficients, (2.12 ± 0.125) × 10 −4 /°C, obtained from thermal-heating induced resonance shifts to optically induced resonance shifts as well as estimated propagation loss and absorption. We then measure the time response of this nonlinearity demonstrating the relaxation time to be 18.7 us, indicating the mechanism to be thermal in nature. Finally, we demonstrate bi-stable optical switching.

42 ENGINEERING↗
NASA NTRS1991

High-power single-element pseudomorphic InGaAs/GaAs/AlGaAs single quantum well lasers for pumping Er-doped fiber amplifiers

A 980-nm-ridge waveguide pseudomorphic InGaAs/GaAs/AlGaAs single-quantum-well laser with a maximum single-ended output power of 240 mW from a facet-coated device is fabricated from a graded-index separate-confinement heterostructure grown by molecular-beam epitaxy. The laser oscillates in the fundamental spatial mode, allowing 22 percent coupling efficiency into a 1.55-micron single-mode optical fiber. Life testing at an output power of 30 mW per facet from uncoated devices reveals a superior reliability to GaAs/AlGaAs quantum-well lasers but also the need for protective facet coatings for long term reliability at power levels required for pumping Er-doped fiber amplifiers.

Larsson, A.↗
DOE OSTI2023

Ultrafast Switching of Interfacial Thermal Conductance

Dynamical control of thermal transport at the nanoscale provides a time-domain strategy for optimizing thermal management in nanoelectronics, magnetic devices, and thermoelectric devices. However, the rate of change available for thermal switches and regulators is limited to millisecond time scales, calling for a faster modulation speed. Here, in this work, time-resolved X-ray diffraction measurements and thermal transport modeling reveal an ultrafast modulation of the interfacial thermal conductance of an FeRh/MgO heterostructure as a result of a structural phase transition driven by optical excitation. Within 90 ps after optical excitation, the interfacial thermal conductance is reduced by a factor of 5 and lasts for a few nanoseconds, in comparison to the value at the equilibrium FeRh/MgO interface. The experimental results combined with thermal transport calculations suggest that the reduced interfacial thermal conductance results from enhanced phonon scattering at the interface where the lattice experiences transient in-plane biaxial stress due to the structural phase transition of FeRh. Our results suggest that optically driven phase transitions can be utilized for ultrafast nanoscale thermal switches for device application.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗