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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

System and method of detecting and analyzing a threat in a confined environment

A system and method of detecting and analyzing a threat in a confined environment is disclosed. An audio board detects and analyzes audio signals. A RF board transmits the signals for emergency response. A battery provides power to the audio board and the RF board. The audio board includes a microcontroller with at least one band-pass filter for distinguishing between a threat and a non-threat event and for measuring or counting pulses if the event is a threat.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

High power conditioning and benchmarking of planar nitrogen-incorporated ultrananocrystalline diamond field emission electron source

Planar nitrogen-incorporated ultrananocrystalline diamond [(N)UNCD] has emerged as a unique field emission source attractive for accelerator applications because of its capability to generate a high charge beam and handle moderate vacuum conditions. Most importantly, (N)UNCD sources are simple to produce: Conventional high aspect ratio isolated emitters are not required to be formed on the surface, and the actual emitter surface roughness is on the order of only 10–100 nm. A careful reliability assessment of (N)UNCD is required before it may find routine application in accelerator systems. In the present study using an L-band normal conducting single-cell rf gun, a (N)UNCD cathode has been conditioned to ~ 42 MV / m in a well-controlled manner. It reached a maximum output charge of 15 nC corresponding to an average current of 6 mA during an emission period of 2.5 $μ$s . Imaging of the emission current revealed a large number of isolated emitters (density over 100/cm 2 ) distributed on the cathode, which is consistent with previous tests in dc environments. The performance metrics, the emission imaging, and the systematic study of emission properties during rf conditioning in a wide gradient range assert (N)UNCD as an enabling electron source for rf injector designs serving industrial and scientific applications. These studies also improve the fundamental knowledge of the practical conditioning procedure via a better understanding of the emission mechanisms.

43 PARTICLE ACCELERATORS↗
NASA NTRS2014

Frame Decoder for Consultative Committee for Space Data Systems (CCSDS)

GNU Radio is a free and open source development toolkit that provides signal processing to implement software radios. It can be used with low-cost external RF hardware to create software defined radios, or without hardware in a simulation-like environment. GNU Radio applications are primarily written in Python and C++. The Universal Software Radio Peripheral (USRP) is a computer-hosted software radio designed by Ettus Research. The USRP connects to a host computer via high-speed Gigabit Ethernet. Using the open source Universal Hardware Driver (UHD), we can run GNU Radio applications using the USRP. An SDR is a "radio in which some or all physical layer functions are software defined"(IEEE Definition). A radio is any kind of device that wirelessly transmits or receives radio frequency (RF) signals in the radio frequency. An SDR is a radio communication system where components that have been typically implemented in hardware are implemented in software. GNU Radio has a generic packet decoder block that is not optimized for CCSDS frames. Using this generic packet decoder will add bytes to the CCSDS frames and will not permit for bit error correction using Reed-Solomon. The CCSDS frames consist of 256 bytes, including a 32-bit sync marker (0x1ACFFC1D). This frames are generated by the Space Data Processor and GNU Radio will perform the modulation and framing operations, including frame synchronization.

Reyes, Miguel A. De Jesus↗
DOE OSTI2017

Ultrawide‐Bandgap Semiconductors: Research Opportunities and Challenges

Abstract Ultrawide‐bandgap (UWBG) semiconductors, with bandgaps significantly wider than the 3.4 eV of GaN, represent an exciting and challenging new area of research in semiconductor materials, physics, devices, and applications. Because many figures‐of‐merit for device performance scale nonlinearly with bandgap, these semiconductors have long been known to have compelling potential advantages over their narrower‐bandgap cousins in high‐power and RF electronics, as well as in deep‐UV optoelectronics, quantum information, and extreme‐environment applications. Only recently, however, have the UWBG semiconductor materials, such as high Al‐content AlGaN, diamond and Ga 2 O 3 , advanced in maturity to the point where realizing some of their tantalizing advantages is a relatively near‐term possibility. In this article, the materials, physics, device and application research opportunities and challenges for advancing their state of the art are surveyed.

Tsao, J. Y.↗
DOE OSTI2014

Effects of thermal treatment on the Mg{sub x}Zn{sub 1−x}O films and fabrication of visible-blind and solar-blind ultraviolet photodetectors

Highlights: • Single-phase wurtzite/cubic Mg{sub x}Zn{sub 1−x}O films were grown by RF magnetron sputtering technique. • We focus on the red-shift caused by annealing the Mg{sub x}Zn{sub 1−x}O films. • MSM-structured visible-blind and solar-blind UV photodetectors were fabricated. - Abstract: A series of single-phase Mg{sub x}Zn{sub 1−x}O films with different Mg contents were prepared on quartz substrates by RF magnetron sputtering technique using different MgZnO targets, and annealed under the atmospheric environment. The absorption edges of Mg{sub x}Zn{sub 1−x}O films can cover the whole near ultraviolet and even the whole solar-blind spectra range, and the solar-blind wurtzite/cubic Mg{sub x}Zn{sub 1−x}O films have been realized successfully by the same method. In addition, the absorption edges of annealed films shift to a long wavelength, which is caused by the diffusion of Zn atoms gathering at the surface during the thermal treatment process. Finally, the truly solar-blind metal-semiconductor-metal structured photodetectors based on wurtzite Mg{sub 0.445}Zn{sub 0.555}O and cubic Mg{sub 0.728}Zn{sub 0.272}O films were fabricated. The corresponding peak responsivities are 17 mA/W at 275 nm and 0.53 mA/W at 250 nm under a 120 V bias, respectively.

36 MATERIALS SCIENCE↗
NASA NTRS1992

Simulation of the synergistic low Earth orbit effects of vacuum thermal cycling, vacuum UV radiation, and atomic oxygen

In order to assess the low Earth orbit (LEO) durability of candidate space materials, it is necessary to use ground laboratory facilities which provide LEO environmental effects. A facility combining vacuum thermal cycling and vacuum ultraviolet (VUV) radiation has been designed and constructed at NASA Lewis Research Center for this purpose. This facility can also be operated without the VUV lamps. An additional facility can be used to provide VUV exposure only. By utilizing these facilities, followed by atomic oxygen exposure in an RF plasma asher, the effects of the individual vacuum thermal cycling and VUV environments can be compared to the effect of the combined vacuum thermal cycling/VUV environment on the atomic oxygen durability of materials. The synergistic effects of simulated LEO environmental conditions on materials were evaluated by first exposing materials to vacuum thermal cycling, VUV, and vacuum thermal cycling/VUV environments followed by exposure to atomic oxygen in an RP plasma asher. Candidate space power materials such as atomic oxygen protected polyimides and solar concentrator mirrors were evaluated using these facilities. Characteristics of the Vacuum Thermal Cycling/VUV Exposure Facility which simulates the temperature sequences and solar ultraviolet radiation exposure that would be experienced by a spacecraft surface in LEO are discussed. Results of durability evaluations of some candidate space power materials to the simulated LEO environmental conditions will also be discussed. Such results have indicated that for some materials, atomic oxygen durability is affected by previous exposure to thermal cycling and/or VUV exposure.

Dever, Joyce A.↗
NASA NTRS1999

Wireless Video System for Extra Vehicular Activity in the International Space Station and Space Shuttle Orbiter Environment

The Wireless Video System (WVS) provides real-time video coverage of astronaut extra vehicular activities during International Space Station (ISS) assembly. The ISS wireless environment is unique due to the nature of the ISS structure and multiple RF interference sources. This paper describes how the system was developed to combat multipath, blockage, and interference using an automatic antenna switching system. Critical to system performance is the selection of receiver antenna installation locations determined using Uniform Geometrical Theory of Diffraction (GTD) techniques.

Loh, Yin C.↗
NASA NTRS2008

Application of Ruze Equation for Inflatable Aperture Antennas

Inflatable aperture reflector antennas are an emerging technology that NASA is investigating for potential uses in science and exploration missions. As inflatable aperture antennas have not been proven fully qualified for space missions, they must be characterized properly so that the behavior of the antennas can be known in advance. To properly characterize the inflatable aperture antenna, testing must be performed in a relevant environment, such as a vacuum chamber. Since the capability of having a radiofrequency (RF) test facility inside a vacuum chamber did not exist at NASA Glenn Research Center, a different methodology had to be utilized. The proposal to test an inflatable aperture antenna in a vacuum chamber entailed performing a photogrammetry study of the antenna surface by using laser ranging measurements. A root-mean-square (rms) error term was derived from the photogrammetry study to calculate the antenna surface loss as described by the Ruze equation. However, initial testing showed that problems existed in using the Ruze equation to calculate the loss due to errors on the antenna surface. This study utilized RF measurements obtained in a near-field antenna range and photogrammetry data taken from a laser range scanner to compare the expected performance of the test antenna (via the Ruze equation) with the actual RF patterns and directivity measurements. Results showed that the Ruze equation overstated the degradation in the directivity calculation. Therefore, when the photogrammetry study is performed on the test antennas in the vacuum chamber, a more complex equation must be used in light of the fact that the Ruze theory overstates the loss in directivity for inflatable aperture reflector antennas.

Welch, Bryan W.↗
DOE OSTI2016

LTE Band 13 and Band 14 Interference Test Summary

Introduction Verizon Wireless operates a nationwide commercial LTE system in Band 13 in the United States. FirstNet will deploy a nationwide Public Safety LTE system in the neighboring Band 14 spectrum to provide first responders with much needed broadband data services. The Idaho National Laboratory’s (INL) Wireless Test Bed (WTB) conducted interference testing between LTE Band 13 and Band 14 systems at typical vertical separation distances encountered on towers with co-located systems. The test configuration mimicked a co-location scenario where Band 13 and Band 14 systems are placed on the same tower with a vertical separation distance of 10 feet. The Band 13 and Band 14 interference testing was conducted in an open-air environment in a location off the INL Test Range that does not have RF emissions in either Band 13 or Band 14. A 30-mile area in the Little Lost River Valley in South Central Idaho was identified that is northwest of the INL range that meets that criterion. The GPS coordinates of the test area are 44° 9’ 14.89” N, 113° 21’ 56.58” W. Based on the noise floor measurements, very little RF noise is present in LTE Band 13 and Band 14 in the remote test location in the Little Lost River Valley in Idaho. This RF isolated area provides a great place to conduct testing of LTE Band 13 and Band 14 performance without effecting or being effected by existing LTE Band 13 or Band 14 systems. The Band 13 baseline average overall throughput was 72.0 Mbps which compares to an overall average throughput of 73.7 Mbps when both Band 13 and Band 14 were transmitting with a typical 10 foot vertical separation. This separation is also required for the antennas to be isolated from each other and not interfere with each other [2]. The Band 14 baseline average overall throughput was 65.2 Mbps which compares to an overall average throughput of 65.9 Mbps when both Band 13 and Band 14 were transmitting with a typical 10 foot vertical separation. These results indicate neither Band 13 nor Band 14 was affected by adjacent channel interference in a co-location scenario with 10 foot vertical separation between radiation centers. Horizontal separation testing should be conducted to verify interference would not exist in a nearby site scenario where Band 13 and Band 14 systems are placed on either adjacent towers or on rooftops of adjacent buildings in close proximity to each other. Interference testing should also be conducted between LTE Band 14 systems and the adjacent Public Safety Narrowband LMR systems. The 1 MHz guard band between LTE Band 14 and the LMR band may not be sufficient enough to prevent interference between these disparate systems. The LMR handsets transmit up to 5W in narrowband channels as narrow as 6.25 kHz bandwidth, which could de-sensitize the Band 14 eNodeB receivers especially in a near-far scenario.

42 ENGINEERING↗
DOE OSTI2014

Electrostatic sensors for SPIDER experiment: Design, manufacture of prototypes, and first tests

A system of electrostatic sensors has been designed for the SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) experiment, prototype RF source of the ITER NBI (neutral beam injection). A prototype of the sensor system was manufactured and tested at the BATMAN (BAvarian Test MAchine for Negative ions) facility, where the plasma environment is similar to that of SPIDER. Different aspects concerning the mechanical manufacturing and the signal conditioning are presented, among them the RF compensation adopted to reduce the RF effects which could lead to overestimated values of the electron temperature. The first commissioning tests provided ion saturation current values in the range assumed for the design, so the deduced plasma density estimate is consistent with the expected values.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1975

Study of growth of single crystal ribbon in space

The technical feasibility is studied of growing single-crystal silicon ribbon in the space environment. Procedures are described for calculating the electromagnetic fields produced in a silicon ribbon by an rf shaping coil. The forces on the ribbon and the degree of shaping to be expected are determined. The expected steady-state temperature distribution in the ribbon is calculated in the one-dimensional approximation. Calculations on simplified models indicate, that lack of flatness of the shaped ribbon and excessive heating of the melt by the eddy currents induced by the shaping fields may pose problems. An analysis of the relative effects of various kinds of forces other than electromagnetic showed that in the space environment capillarity forces would dominate, and that the shape of the melt is thus principally determined by the shape of any solids with which it comes in contact. This suggests that ribbon may be produced simply by drawing between parallel wires. A concept is developed for a process of off-angle growth, in which the ribbon is pulled at an angle to the solidification front. Such a process promises to offer increased growth rate, better homogeneity, and thinner ribbon.

Wood, V. E.↗
DOE OSTI2017

Chroma Shift and Gamut Shape: Going Beyond Average Color Fidelity and Gamut Area

Though sometimes referred to as a two-measure system for evaluating color rendition, IES TM-30-15 includes other key components that go beyond the high-level average values IES Rf and IES Rg. This article focuses on the Color Vector Graphic and Local Chroma Shift (IES Rcs,hj), discussing the calculation methods for these evaluation tools and providing context for the interpretation of the values. It also presents alternatives for quantifying the same characteristics, which can inform the development of future measures. The Color Vector Graphic (CVG) is a visual representation of hue and chroma shifts across different hues. It quickly communicates complex information about how object colors will be rendered by a light source, although it is difficult or impossible to use for writing a specification. CVGs demonstrate that increases in chroma for certain hues sometimes means a decrease in chroma for other hues, and illustrates hue shifts for intermediate colors. The combination of shifts over different hues can be referred to as gamut shape. Complementing this information are the IES Rcs,hj values, which quantify the average relative chroma shift for samples in each of the 16 hue-angle bins (j) specified in IES TM-30-15. Unlike measures of average color fidelity and gamut area, gamut shape and hue-specific chroma shift are new concepts with no directly-comparable historical references. It will be critical to incorporate the Color Vector Graphic and Local Chroma Shift values into practice because they capture information about color rendition that is impossible to describe with average measures (such as CIE Ra, IES Rf, or IES Rg), but that is critical to understanding human evaluations of color quality in architectural environments.

Chroma Shift↗
DOE OSTI2020

Nuclear response of additive manufactured GRCop-84 copper for use in Lower hybrid launchers in a fusion environment

Recent advances in selective laser melting (SLM) 3D printing technology allow additive manufacture of lower hybrid current drive (LHCD) RF launchers from a new material, Glenn Research Copper 84 (GRCop-84), a Cr 2 Nb (8 at. % Cr, 4 at. % Nb) precipitation hardened alloy, in configurations unachievable with conventional machining. Tensile strength and thermal conductivity are compared to other competing high conductivity copper alloys for fusion use. Swelling and conductivity at 100 DPA when exposed to the Hanford Fast Flux Test Facility neutron spectrum is predicted in the 1–2 % and 65-70% IACS range, respectively, by comparison to copper alloys with similar precipitate and grain size. Finally, self-similar ion irradiation of a GRCop-84 target at 430 °C to 20 DPA resulted in no noticeable void formation in FIB cross sections or TEM lamella.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Structural and magnetic phase transitions in chromium nitride thin films grown by rf nitrogen plasma molecular beam epitaxy

A magneto-structural phase transition is investigated in single crystal CrN thin films grown by rf plasma molecular beam epitaxy on MgO(001) substrates. While still within the vacuum environment following MBE growth, in-situ low-temperature scanning tunneling microscopy, and in-situ variable low-temperature reflection high energy electron diffraction are applied, revealing an atomically smooth and metallic CrN(001) surface, and an in-plane structural transition from 1×1 (primitive CrN unit cell) to $\sqrt{2}$ × $\sqrt{2}$ -R45° with a transition temperature of 278 ± 3 K, respectively. Ex-situ temperature dependent measurements using neutron diffraction are also per formed, looking at the structural peaks and likewise revealing a first-order structural transition along the [111] out-of-plane direction, with a transition temperatures of 268 ± 3 K. Turning to the magnetic peaks, neutron diffraction confirms a clear magnetic transition from paramagnetic at room temperature to antiferromagnetic at low temperatures with a sharp, first-order phase transition and a Néel temperature of 270 ± 2 K or 280 ± 2 K for two different films. In addition to the experimental measurements of structural and magnetic ordering, we also discuss results from first-principles theoretical calculations which explore various possible magneto-structural models.

Materials Science↗
DOE OSTI2023

Data, scripts, and figures associated with a manuscript studying impact of climate and topography on post-fire vegetation recovery.

This data package is associated with the publication “Impact of Topography and Climate on Post-fire Vegetation Recovery Across Different Burn Severity and Land Cover Types through Machine Learning” submitted to Remote Sensing of Environment (Zahura et al. 2023). In this research, a machine learning algorithm, random forest (RF), was utilized to examine the impact of climate and topography on post-fire vegetation recovery. We used enhanced vegetation index (EVI) to examine varying burn severity and land cover types. The data package includes the input files for RF model training, outputs from model predictions and analysis, and python scripts to run the model, analyze the results to understand model performance and interpretability, and plot manuscript figures. This data package contains three folders (Data, Scripts, and Figures), a file-level metadata (FLMD) csv, and a data dictionary (dd) csv. Please see Postfire_recovery_flmd.csv for a list of all files contained in this data package and descriptions for each. The data dictionary (Postfire_recovery_dd.csv) describes the csv column headers. The “Data” folder provides all the inputs and outputs to train the RF model, evaluate performance, and interpret predictions. The “Scripts” folder contains python scripts and jupyter notebooks for model training and result analysis. The “Figures” folder includes the figures used in the manuscript in “.png” and “.jpg” format.

54 ENVIRONMENTAL SCIENCES↗