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At least 919 records · Page 51

All sources NASA NTRS DOE OSTI

NASA NTRSDate not supplied

Topographic Slant Range Modeling and Fault Detection for Precision Planetary Landing

This work presents a novel landing site relative topographic measurement model for aslant range sensor being utilized for precision planetary landing operations. The measurement model accounts for the local terrain the slant range sensor captures and leverages knowledge of the estimated landing site provided by the navigation filter. Notably, in contrast to previous works, the new model does not rely on surface normal approximation, reducing the model’s sensitivity to noisy digital elevation maps which represent the local topography. In addition to the measurement model, this work introduces a novel fault detection method, denoted the probabilistic inspection of topographic filter altitude likelihood (PITFAL) algorithm, that implements a statistical outlier rejection algorithm. PITFAL is designed for multi-beam slant range sensors, such as the Navigation Doppler LIDAR (NDL), and identifies statistically inconsistent range estimates through a consensus check on the set of apparent altitudes computed for each individual beam. These models are numerically validated by the Safe and Precise Landing Capability Evolution (SPLICE) project’s high-fidelity terrestrial and lunar lander simulations.

Davis W Adams↗

NASA NTRSDate not supplied

Lunar Laser Ranging in the Artemis Era

The retroreflector arrays placed on the lunar surface by the Apollo astronauts and the Soviet Luna missions continue to contribute to our understanding of gravitational physics, Earth and Moon geophysics, geodesy, and dynamics. The key science questions addressed by Lunar Laser Ranging remain very relevant today: What is the interior structure of the Moon? Is the Equivalence Principle exact? Does the strength of gravity vary with space and time? What is the nature of spacetime? Do extra dimensions or other new physics alter the inverse square law of gravity? The lunar retroreflectors are also an essential component of the realizations of the lunar reference frames. The half-century old lunar retroreflectors continue to provide excellent ranging targets but are showing signs of degradation and the measurement error associated with their physical size and varying tilt is becoming a limitation in the quest for more precise range measurements. In addition, the clustering of the arrays in the mid-latitudes of the Moon limits their geometrical strength and coverage. The south polar region planned for Artemis presents an ideal opportunity for improving the geometric distribution. Retroreflectors utilizing a large optical cross-section single cube corner do not have tilt error associated with the existing arrays making them good options for lunar deployment. Several new retroreflectors of this type are being prepared for upcoming Commercial Lunar Payload Services missions as well as Artemis. This presentation will discuss NASA’s plans for expanding the lunar laser ranging capabilities with a focus on the Artemis Lunar Laser Retroreflector.

Stephen Merkowitz↗

NASA NTRS2025

Topographic Slant Range Modeling and Fault Detection for Precision Planetary Landing

Davis W Adams↗

DOE OSTI2012

Saturation and Dynamic Range of Microchannel Plate-Based X-Ray Imagers

This paper describes recent advances in Monte Carlo simulations of microchannel plate (MCP)–based x-ray detectors, a continuation of ongoing work in this area. A Monte Carlo simulation model has been developed over the past several years by National Security Technologies, LLC (NSTec). The model simulates the secondary electron emission process in an MCP pore and includes the effects of gain saturation. In this work we focus on MCP gain saturation and dynamic range. We have performed modeling and experimental characterizations of L/D = 46, 10-micron diameter, MCP-based detectors. The detectors are typically operated by applying a subnanosecond voltage pulse, which gates the detector on. Agreement between the simulations and experiment is very good for a variety of voltage pulse waveforms ranging in width from 150 to 300 ps. The results indicate that such an MCP begins to show nonlinear gain around 5 × 10^4 electrons per pore and hard saturation around 105 electrons per pore. The simulations show a difference in MCP sensitivity vs voltage for high flux of photons producing large numbers of photoelectrons on a subpicosecond timescale. Simulations and experiments both indicate an MCP dynamic range of 1 to 10,000, and the dynamic range depends on how the voltage is applied.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2018

Review of Inorganic Salt Hydrates with Phase Change Temperature in Range of 5°C to 60°C and Material Cost Comparison with Common Waxes

Phase change materials (PCMs) with desirable phase change temperatures can be used to provide a constant temperature thermal source or sink for diverse applications. As such, incorporating PCMs into building materials, equipment, or appliances can shift and/or reduce the energy load. The motivation of this work is to identify low-cost inorganic salt hydrate PCMs that can complement current building systems and designs, and compare them with common paraffins.In this work, we analyzed inorganic salt hydrates with phase change temperatures in the range of 5-60°C, to target both space heating and cooling applications. The properties of the salt hydrates were compared with paraffins over the same temperature range. The results showed that PCMs with a melting temperature above 20°C, salt hydrates have advantages over paraffins including higher thermal energy density (45-120 kWh/m3 for salt hydrates; 45-60 kWh/m3 for paraffins) and generally lower material energy cost (1-20 $/kWh for salt hydrates; 20-30 $/kWh for comparable paraffins). For PCMs with a melting temperature less than 20°C, the material cost is higher for both salt hydrates and paraffins (30-110 $/kWh for both classes of materials) and salt hydrates retain their advantage of greater thermal energy density (50-120 kWh/m3 for salt hydrates; 45-60 kWh/m3 for paraffins). In all cases, factors including thermal cyclability, stability, congruency, corrosion, and supercooling must be considered when comparing paraffins and salt hydrates for a particular application. Finally, we give an overview of enhancement techniques for salt hydrate PCMs and find that limited efforts have been pursued to tune salt hydrate phase change temperatures, with a wider range of studies investigating stabilization and minimization of supercooling. This analysis shows the potential of developing salt hydrate PCMs for low-cost heating and cooling thermal energy storage systems for a range of applications.

Hirschey, Jason↗

DOE OSTI2020

Synthetic-aperture radar (SAR) imaging with range-resolved reflection data

SAR imaging may be performed with range-resolved reflection data, where a spread-spectrum signal, such as a code division multiple access (CDMA) signal, is transmitted instead of a simple frequency chirp. The reflected spread-spectrum signal may be analyzed to gather range-resolved reflection data. Range-resolved reflection data may be gathered at each angular view. This data may be used to construct a more accurate approximation of the Fourier transform of the desired image than can be done by a conventional SAR approach. The image may be reconstructed from this Fourier transform using Fourier inversion techniques similar to those used in conventional SAR approaches. The range-resolved reflection scheme generally requires somewhat more processing to recover the image as compared with conventional SAR systems, but provides a significantly more stable image with less degradation from effects that plague conventional SAR systems. This can eliminate the need for phase coherency altogether and also eliminate “phase drift,” which leads to image distortion. This may be especially well suited for high resolution imaging of relatively large targets.

47 OTHER INSTRUMENTATION↗

DOE OSTI2021

Short Range Correlations and Few Body Precision Measurements

This talk will discuss the exciting experimental program studying short range correlations and few body dynamics at Jefferson Lab in ?=3 nuclei. Quasi-elastic electron scattering on these light nuclei have readily calculable ground states but can already exhibit complex nuclear behavior including nucleon-nucleon (NN) short range correlations (SRCs). 3H and 3He, being mirror nuclei, exploit the maximum available isospin asymmetry and can be compared directly with ab initio calculations. This talk will summarize the recent Hall A 3H and 3He results. The first measurement of SRC nucleons in 3He using the CLAS detector from Hall B and identifying lead neutrons in ?? pairs at high missing momentum will be shown. These fascinating results will be extended in an approved experiment using the CLAS12 detector to measure high-statistics and absolute cross sections on 2H, 3He, and 3H with a wide range of kinematical coverage. This talk will discuss the recent and proposed measurements and their implications on nuclear models for few body nuclear dynamics and short range structure.

Szumila-Vance, Holly↗

DOE OSTI2015

Studies of a proton phase beam monitor for range verification in proton therapy

A primary subject of the present research in particle therapy is to ensure the precise irradiation of the target volume. The prompt gamma timing (PGT) method provides one possibility for in vivo range verification during the irradiation of patients. Prompt gamma rays with high energies are emitted promptly due to nuclear reactions of protons with tissue. The arrival time of these gammas to the detector reflects the stopping process of the primary protons in tissue and are directly correlated to the range. Due to the time resolution of the detector and the proton bunch time spread, as well as drifts of the bunch phase with respect to the accelerator frequency, timing spectra are smeared out and compromise the accuracy of range information intended for future clinical applications. Nevertheless, counteracting this limitation and recovering range information from the PGT measured spectra, corrections using a phase beam monitor can be performed. A first prototype of phase beam monitor was tested at GSI Darmstadt, where measurements of the energy profile of the ion bunches were performed. At the ELBE accelerator Helmholtz-Zentrum Dresden-Rossendorf (HZDR), set up to provide bremsstrahlung photons in very short pulses, a constant fraction algorithm for the incoming digital signals was evaluated, which is used for optimizing the time resolution. Studies of scattering experiments with different thin targets and detector positions are accomplished at Oncoray Dresden, where a clinical proton beam is available. These experiments allow a basic characterization of the proton bunch structure and the detection yield. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2024

Supervisory genset control in range-extended electric vehicle

A controls system for a range-extended electric vehicle comprising an overall system control unit, an engine control module configured to control a range extender of the range-extended electric vehicle, power electronics configured to control a generator of the range-extended electric vehicle, and a supervisory control module coupled between the overall system control unit and the engine control module and the power electronics, the supervisory control module configured to receive information from the overall system control unit and provide commands to the engine control module and the power electronics.

Li, Ke↗

DOE OSTI2022

Impact of battery cell imbalance on electric vehicle range

Due to manufacturing variation, battery cells often possess heterogeneous characteristics, leading to battery state-of-charge variation in real-time. Since the lowest cell state-of-charge determines the useful life of battery pack, such variation can negatively impact the battery performance and electric vehicles range. Existing research has been focused on control design to mitigate cell imbalance. However, it is yet unclear how much impacts the cell imbalance can have on electric vehicle range. This paper closes this knowledge gap by using a simulation environment consisting of real-world driving speed data, vehicle longitudinal control, propulsion and vehicle dynamics, and cell level battery modeling. In particular, each battery cell is modeled as an equivalent circuit model, and variations among cell parameters are introduced to assess their impact on electric vehicles range and to identify the most influential parameter variations. Simulation results and analysis can be used to assist balancing control design and to benchmark control performance.

25 ENERGY STORAGE↗

DOE OSTI2016

TU-FG-BRB-09: Thermoacoustic Range Verification with Perfect Co-Registered Overlay of Bragg Peak onto Ultrasound Image

Purpose: The potential of particle therapy has not yet been fully realized due to inaccuracies in range verification. The purpose of this work was to correlate the Bragg peak location with target structure, by overlaying thermoacoustic localization of the Bragg peak onto an ultrasound image. Methods: Pulsed delivery of 50 MeV protons was accomplished by a fast chopper installed between the ion source and the inflector of the 88″ cyclotron at Lawrence Berkeley National Lab. 2 Gy were delivered in 2 µs by a beam with peak current of 2 µA. Thermoacoustic emissions were detected by a cardiac array and Verasonics V1 ultrasound system, which also generated a grayscale ultrasound image. 1024 thermoacoustic pulses were averaged before filtering and one-way beamforming focused signal onto the Bragg peak location with perfect co-registration to the ultrasound images. Data was collected in a room temperature water bath and gelatin phantom with a cavity designed to mimic the intestine, in which gas pockets can displace the Bragg peak. Experiments were performed with the cavity both empty and filled with olive oil. Results: In the waterbath overlays of the Bragg peak agreed with Monte Carlo simulations to within 800±170 µm. Agreement within 1.3 ± 0.2 mm was achieved in the gelatin phantom, although relative stopping powers were estimated only to first order from CT scans. Protoacoustic signals were detected after travel from the Bragg peak through 29 mm and 65 mm of phantom material when the cavity was empty and full of olive oil, respectively. Conclusion: Protoacoustic range verification is feasible with a commercial clinical ultrasound array, but at doses exceeding the clinical realm. Further optimization of both transducer array and injection line chopper is required to enable range verification within a 2 Gy dose limit, which would enable online adaptive treatment. This work was supported in part by a UWM Intramural Instrumentation Grant and by the Director, Office of Science, Office of Nuclear Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. YMQ was supported by a UWM-OUR summer fellowship.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2018

Small-Scale Structure of Thermal X-Ray Background of the Solar Corona and Microflares in the Photon Energy Range of 3-16 keV

The small-scale structure of the thermal X-ray background of the solar corona and microflares in the photon energy range from 3 to 16 keV according to the RHESSI data obtained on March–April 2003 is analyzed. The study of the reduction in the X-ray intensity in this spectral range is continued. A reduction and, in some cases, an increase in the X-ray intensity of the thermal background of the solar corona and microflares in narrow subranges of the X-ray spectrum of the quiet Sun are revealed in the photon energy range of 3–11 keV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2018

Dielectric Properties of Nanocrystalline Tungsten Oxide in the Temperature Range of 223–293 K

The dielectric properties of nanocrystalline tungsten oxide are studied in the temperature range of 223–293 K and in the frequency range ν = 10{sup –2}–10{sup 6} Hz. Powders of WO{sub 3} with particle sizes of 110, 150, and 200 nm are prepared by the heat treatment of ammonium paratungstate at various temperatures. It is established that the frequency dependences of the conductivity for all samples increase with an increase in frequency, while the polarization characteristics ε'(ν) and ε'(ν) decrease. It is found that the frequency dependences of the conductivity are described by a function of the form ν{sup s} with an index in the range of (0.83–0.90) ± 0.01, which is characteristic of the “hopping” mechanism of charged-particle motion (complexes) over localized states confined by potential barriers and structural defects.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Short- and Intermediate-Range Structure and Dynamics of Fe-Ni-C Liquid Under Compression

Properties of liquid Fe alloys under high-pressure conditions are crucial for understanding the composition, thermal state, and dynamics of Earth’s core. Experiments on such liquids, however, are often performed under pressures far below those of the outer core, necessitating long extrapolations of experimental results to core conditions. Such estimates can be complicated by light elements possibly forming pressure-dependent molecular clusters that can significantly affect the physical properties of liquids as core conditions are approached. First-principles molecular dynamics simulations were employed to compute the properties of an Fe-Ni-C liquid with a composition of Fe 3.7 Ni 0.37 C at 1673 K and pressures from 0 to 67 GPa to benchmark computational methods on pressure effects on the structure and properties of the liquid relative to low pressure experimental results. The short-range structure is manifested by the coordination number (CN) of Fe/Ni-Fe/Ni being around 12, indicative of a nearly close-packed structure in the pressure range, and the CN of C-Fe/Ni gradual increasing from 6.5 to 8.5, indicative of an approximately octahedral to cubic transition as pressure increases. The Fe/Ni-Fe/Ni bond distance, however, is found to be 10 times more compressible than the C-Fe/Ni distance. The intermediate-range structure of Fe/Ni-Fe/Ni and C-Fe/Ni subsystems, described by a partial configurationally decomposed distribution function, undergoes substantial changes, characterized by a significant increase of the number of polyhedra that share 3 atoms with each other. Such dense configurations are related to an increased bulk modulus, decreased diffusion coefficient, decreased activation volume for diffusion, and increased shear viscosity. Reproducing the experimental observations at low pressures provides important support for modeling the liquid under the conditions relevant to the outer core.

58 GEOSCIENCES↗

DOE OSTI2016

Short-to-Medium-Range Order and Atomic Packing in Zr 48 Cu 36 Ag 8 Al 8 Bulk Metallic Glass

Due to its excellent glass-forming ability (GFA), the Zr 48 Cu 36 Ag 8 Al 8 bulk metallic glass (BMG) is of great importance in glass transition investigations and new materials development. However, due to the lack of detailed structural information, the local structure and atomic packing of this alloy is still unknown. In this work, synchrotron measurement and reverse Monte Carlo simulation are performed on the atomic configuration of a Zr-based bulk metallic glass. The local structure is characterized in terms of bond pairs and Voronoi tessellation. It is found that there are mainly two types of bond pairs in the configuration, as the body-centered cubic (bcc)-type and icosahedral (ico)-type bond pairs. On the other hand, the main polyhedra in the configuration are icosahedra and the bcc structure. That is, the bcc-type bond pairs, together with the ico-type bond pairs, form the bcc polyhedra, introducing the distortion in bcc clusters in short range. However, in the medium range, the atoms formed linear or planar structures, other than the tridimensional clusters. That is, the medium-range order in glass is of 1D or 2D structure, suggesting the imperfect ordered packing feature.

36 MATERIALS SCIENCE↗

NASA NTRS1964

Microwave modulated optical ranging and tracking systems.

Microwave modulated optical tracking and ranging systems for range and range rate measurement accuracy

DOPPLER RADAR↗

DOE OSTI2020

Effect of Fluorination on Lithium Transport and Short-Range Order in Disordered-Rocksalt-Type Lithium-Ion Battery Cathodes

Fluorine substitution is a critical enabler for improving the cycle life and energy density of disordered rocksalt (DRX) Li-ion battery cathode materials which offer prospects for high energy density cathodes, without the reliance on limited mineral resources. Due to the strong Li–F interaction, fluorine also is expected to modify the short-range cation order in these materials which is critical for Li-ion transport. In this work, density functional theory and Monte Carlo simulations are combined to investigate the impact of Li–F short-range ordering on the formation of Li percolation and diffusion in DRX materials. Additionally, the modeling reveals that F substitution is always beneficial at sufficiently high concentrations and can, surprisingly, even facilitate percolation in compounds without Li excess, giving them the ability to incorporate more transition metal redox capacity and thereby higher energy density. It is found that for F levels below 15%, its effect can be beneficial or disadvantageous depending on the intrinsic short-range order in the unfluorinated oxide, while for high fluorination levels the effects are always beneficial. Using extensive simulations, a map is also presented showing the trade-off between transition-metal capacity, Li-transport, and synthetic accessibility, and two of the more extreme predictions are experimentally confirmed.

25 ENERGY STORAGE↗

DOE OSTI2018

Optical Properties of Amorphous Perfluorinated Polymers in the Terahertz Range

Novel amorphous perfluorinated polymers are synthesized and characterized using terahertz (THz) and x-ray spectra. The polymerization of such polymers in which all H atoms are replaced by F is examined. Their optical properties in the THz range show a record low index of refraction for solids in this range. The minimal possible index of refraction for such polymers is estimated. These materials are demonstrated to be highly transparent. The position of a weak absorption maximum in the range 1–2 THz is compared with the characteristic distance between the polymer structural elements that is obtained from an x-ray diffraction analysis of these materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗