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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Experimental demonstration and modeling of a robotic neutron detector with spectral and directional sensitivity for treaty verification

International safeguards and arms control agreements often require labor-intensive, intrusive onsite inspections to perform verification tasks. The ability to localize a neutron source and/or characterize a neutron field may be imperative for identifying anomalies. We are interested in the role of autonomous mobile robots, which, if designed properly, may be more effective and efficient and less intrusive than their human counterparts. Toward developing such a capability, we, for this study, have constructed the N-SpecDir Bot, comprised of three boron-coated straw detectors azimuthally-distributed within a cylinder of high-density polyethylene, which is mounted on an omni-directional robotic platform. Our N-SpecDir Bot is specifically designed to provide spectral and directional sensitivity, in addition to gross counts, by utilizing the signals from the three detectors. The detection system has been extensively characterized by MCNP modeling, which has been benchmarked to experiments conducted at the Princeton Plasma Physics Laboratory. We demonstrate the spectral and directional sensitivity experimentally and in simulation, and provide a simple yet robust method for directional measurements.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
NASA NTRS2005

Miniature Focusing Time-of-Flight Mass Spectrometer

An improved miniature time-of-flight mass spectrometer has been developed in a continuing effort to minimize the sizes, weights, power demands, and costs of mass spectrometers for such diverse applications as measurement of concentrations of pollutants in the atmosphere, detecting poisonous gases in mines, and analyzing exhaust gases of automobiles. Advantageous characteristics of this mass spectrometer include the following: It is simple and rugged. Relative to prior mass spectrometers, it is inexpensive to build. There is no need for precise alignment of its components. Its mass range is practically unlimited Relative to prior mass spectrometers, it offers high sensitivity (ability to measure relative concentrations as small as parts per billion). Its resolution is one dalton (one atomic mass unit). An entire mass spectrum is recorded in a single pulse. (In a conventional mass spectrometer, a spectrum is recorded mass by mass.) The data-acquisition process takes only seconds. It is a lightweight, low-power, portable instrument. Although time-of-flight mass spectrometers (TOF-MSs) have been miniaturized previously, their performances have not been completely satisfactory. An inherent adverse effect of miniaturization of a TOF-MS is a loss of resolution caused by reduction of the length of its flight tube. In the present improved TOF-MS, the adverse effect of shortening the flight tube is counteracted by (1) using charged-particle optics to constrain ion trajectories to the flight-tube axis while (2) reducing ion velocities to increase ion flight times. In the present improved TOF-MS, a stream of gas is generated by use of a hypodermic needle. The stream of gas is crossed by an energy-selected, pulsed beam of electrons (see Figure 1). The ions generated by impingement of the electrons on the gas atoms are then focused by three cylindrical electrostatic lenses, which constitute a segmented flight tube. After traveling along the flight tube, the ions enter a charged-particle detector. The output of the detector is fed to a counting circuit to obtain data on the counting rate as a function of time. Inasmuch as time of flight is directly proportional to the ion mass, a plot of the counting rate versus time of flight is equivalent to a mass spectrum (see Figure 2).

Kanik, Isik↗
NASA NTRS1995

Solid-state image sensor with focal-plane digital photon-counting pixel array

A photosensitive layer such as a-Si for a UV/visible wavelength band is provided for low light level imaging with at least a separate CMOS amplifier directly connected to each PIN photodetector diode to provide a focal-plane array of NxN pixels, and preferably a separate photon-counting CMOS circuit directly connected to each CMOS amplifier, although one row of counters may be time shared for reading out the photon flux rate of each diode in the array, together with a buffer memory for storing all rows of the NxN image frame before transfer to suitable storage. All CMOS circuitry is preferably fabricated in the same silicon layer as the PIN photodetector diode for a monolithic structure, but when the wavelength band of interest requires photosensitive material different from silicon, the focal-plane array may be fabricated separately on a different semiconductor layer bump-bonded or otherwise bonded for a virtually monolithic structure with one free terminal of each diode directly connected to the input terminal of its CMOS amplifier and digital counter for integration of the photon flux rate at each photodetector of the array.

Fossum, Eric R.↗
DOE OSTI2023

Autonomous Polycrystalline Material Decomposition For Hyperspectral Neutron Tomography

Hyperspectral neutron tomography is an effective method for analyzing crystalline material samples with complex compositions in a non-destructive manner. Since the counts in the hyperspectral neutron radiographs directly depend on the neutron cross-sections, materials may exhibit contrasting neutron responses across wavelengths. Therefore, it is possible to extract the unique signatures associated with each material and use them to separate the crystalline phases simultaneously.We introduce an autonomous material decomposition (AMD) algorithm to automatically characterize and localize polycrystalline structures using Bragg edges with contrasting neutron responses from hyperspectral data. The algorithm estimates the linear attenuation coefficient spectra from the measured radiographs and then uses these spectra to perform polycrystalline material decomposition and reconstructs 3D material volumes to localize materials in the spatial domain. Our results demonstrate that the method can accurately estimate both the linear attenuation coefficient spectra and associated reconstructions on both simulated and experimental neutron data.

Samin nur chowdhury, Mohammad↗
DOE OSTI2020

Filtration Performance Results: Sierra Peaks Material No. 4

Sandia National Laboratories (SNL) assessed the filtration performance of materials from Sierra Peaks to identify alternatives which may perform similarly to materials used in FDA-approved N95 respirators. This work is meant to characterize the aerosol performance of materials to give Sierra Peaks information for them to determine if they elect to submit masks made using these materials for follow-on N95 certification testing at an accredited facility. The R&D testbed used is a large-scale filtration system designed to test commercial filter boxes. System modifications were performed to simulate, where possible, parameters defined by the National Institute for Occupational Safety and Health (NIOSH) for certification of filter materials for N95 respirators (NIOSH 2019). The system is a pull-through design. Air enters through a Laminar Flow Element (LFE) and the volumetric flow is measured based on the pressure drop across the LFE. Pressure is measured via a Pressure Transducer (PT). The air then passes through a High Efficiency Particulate Air (HEPA) filter to purge the air of ambient airborne particulates. Test aerosol is injected into the flow shortly after and mixing is induced via a coarse mesh. The airflow is allowed to fully develop prior to arriving at the test section. The aerosol then passes through the test material mounted in a box in the test section. Pressure drop across the test article is measured and aerosol sampling probes measure the aerosol concentrations upstream and downstream of the sample. The air passes through a second HEPA filter prior to being exhausted to ambient by a blower. A Topas aerosol generator is used to produce the test aerosol from Sodium Chloride (NaC1) dissolved in deionized (DI) water. Generated aerosol passes through a heated mixing chamber and a desiccant dryer to produce nanosized solid-state particulates. A dilution loop allows for the aerosol concentration to be regulated. The aerosol sampling probes upstream and downstream of the test section are aligned with the flow path. These are ducted directly to the aerosol sizing and counting instruments. A Laser Aerosol Spectrometer (LAS) was used for data collection in the original configuration of the system and was also used for initial testing in this project. Because the lower measurement range for the LAS is 90 nanometers (nm), the LAS was switched out for a more complicated Scanning Mobility Particle Sizer (SMPS) spectrometer system. The SMPS is comprised of an Electrostatic Classifier (EC), Differential Mobility Analyzer (DMA), and a Condensation Particle Counter (CPC). This enabled data collection at 75 nm, the particle size called out in the NIOSH guidelines.

36 MATERIALS SCIENCE↗
NASA NTRS1976

Radioactivity in the galactic plane

The paper reports the detection of a large concentration of interstellar radioactivity during balloon-altitude measurements of gamma-ray energy spectra in the band between 0.02 and 12.27 MeV from galactic and extragalactic sources. Enhanced counting rates were observed in three directions towards the plane of the Galaxy; a power-law energy spectrum is computed for one of these directions (designated B 10). A large statistical deviation from the power law in a 1.0-FWHM interval centered near 1.16 MeV is discussed, and the existence of a nuclear gamma-ray line at 1.15 MeV in B 10 is postulated. It is suggested that Ca-44, which emits gamma radiation at 1.156 MeV following the decay of radioactive Sc-44, is a likely candidate for this line, noting that Sc-44 arises from Ti-44 according to explosive models of supernova nucleosynthesis. The 1.16-MeV line flux inferred from the present data is shown to equal the predicted flux for a supernova at a distance of approximately 3 kpc and an age not exceeding about 100 years.

Walraven, G. D.↗
NASA NTRS2018

Performance Analysis of Airborne Photon-Counting Lidar Data in Preparation for the ICESat-2 Mission

Two airborne photon-counting laser altimeters have been deployed in direct support of National Aeronautics and Space Adminsitration (NASA's) upcoming Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) mission. Multiple Altimeter Beam Experimental Lidar (MABEL) was developed specifically for ICESat-2 testing and development. MABEL data are used to simulate key aspects of the ICESat-2 measurement strategy and are critical to the development of the algorithms for geophysical data-product generation. Slope Imaging Multipolarization Photon-counting Lidar (SIMPL) is a NASA Goddard Space Flight Center instrument that has also been deployed in support of ICESat-2 performance discovery. Both instruments are photon-counting, small footprint laser altimeters that sample in both the 532- and 1064-nm wavelengths. And both instruments serve as a proxy for ICESat-2 operational performance and error assessment and a basis for the development of potential validation strategies. This paper provides an overview of how data from MABEL and SIMPL overflights have specifically provided the foundation for understanding the quality of ICESat-2 data and how we can plan to evaluate ICESat-2 products through comparison with other modalities of lidar data and/or groundtruth locations using ground fiducials.

MABEL↗
NASA NTRS2001

Auroral, Polar Cap, and Polar Cusp Modeling and Data Analysis for the IMAGE Mission and LENA Instrument

One of the chief mysteries in the LENA perigee pass data is the lack of an apparent auroral oval in the images. Another is that in some cases ENA are seen from any direction near the Earth regardless of the latitude of the spacecraft. These facts lead one to ask a fundamental question: Is the instrument responding to ENA primarily? One possible way to get out of the "ambiguity" of the data is to assume that at least part of the signal is produced by something other than ENA. The two main candidates for this "something else" are UV light and energetic charged particles. UV light could only effect the instrument when its fan shaped aperture points toward the source. The most intense of which will be the sun, with day glow being the second strongest and the auroral zone, the third. We can rule out UV light as a prime source of counts in the perigee pass data for the following reasons: 1) The perigee pass signal is different in form and much stronger than the sun pulse signal seen just before or just after perigee; 2) There is no indication of the auroral zone, which would produce at least two peaks in the counts versus spin phase curve; 3) Mike Colliers' analysis of the sun pulse signal shows that it varies with the flux of the solar wind and not with variations in the solar UV flux. Charge particles that enter the aperture of the instrument and produce counts would show up when the instrument looks in the direction from which they come. In all of the data I am analyzing voltages were being applied to the collimators so that most charged particles should have been excluded from the instrument but this effect could still show up where the flux of energetic particles is high enough. The most likely place would be in the auroral zone where energetic electrons and protons precipitate. If these particles are producing counts then they should be seen when the instrument looks in and near the zenith direction. In nearly all of the perigee passes the zenith direction is devoid of counts.

Wilson, Gordon R.↗
DOE OSTI2025

Fast event-based electron counting for small-molecule structure determination by MicroED

Electron counting helped realize the resolution revolution in single-particle cryoEM and is now accelerating the determination of MicroED structures. Its advantages are best demonstrated by new direct electron detectors capable of fast (kilohertz) event-based electron counting (EBEC). This strategy minimizes the inaccuracies introduced by coincidence loss (CL) and promises rapid determination of accurate structures. We used the Direct Electron Apollo camera to leverage EBEC technology for MicroED data collection. Given its ability to count single electrons, the Apollo collects high-quality MicroED data from organic small-molecule crystals illuminated with incident electron beam flux densities as low as 0.01–0.045 e − /Å 2 /s. Under even the lowest flux density (0.01 e − /Å 2 /s) condition, fast EBEC data produced ab initio structures of a salen ligand (268 Da) and biotin (244 Da). Each structure was determined from a 100° wedge of data collected from a single crystal in as few as 50 s, with a delivered fluence of only ∼0.5 e − /Å 2 . Fast EBEC data collected with a fluence of 2.25 or 3.33 e − /Å 2 also facilitated a 1.5 Å structure of thiostrepton (1665 Da). While refinement of these structures appeared unaffected by CL, a CL adjustment applied to EBEC data further improved the distribution of intensities measured from the salen ligand and biotin crystals. However, CL adjustment only marginally improved the refinement of their corresponding structures, signaling the already high counting accuracy of detectors with counting rates in the kilohertz range. Overall, by delivering low-dose structure-worthy data, fast EBEC collection strategies open new possibilities for high-throughput MicroED.

EBEC↗
DOE OSTI2026

Machine learning pipeline for denoising low signal-to-noise ratio and out-of-distribution transmission electron microscopy datasets

High-resolution transmission electron microscopy (HRTEM) is crucial for observing material’s structural and morphological evolution at Angstrom scales, but the electron beam can alter these processes. Devices such as CMOS-based direct-electron detectors operating in electron-counting mode can be utilized to substantially reduce the electron dosage. However, the resulting images often lead to a low signal-to-noise ratio, which requires frame integration that sacrifices temporal resolution. Several machine learning (ML) models have been recently developed to successfully denoise HRTEM images. Yet, these models are often computationally expensive, and their inference speeds on GPUs are outpaced by the imaging speed of advanced detectors, precluding in situ analysis. Furthermore, the performance of these denoising models on datasets with imaging conditions that deviate from the training datasets has not been evaluated. To mitigate these gaps, we propose a new self-supervised ML denoising pipeline specifically designed for time-series HRTEM images. This pipeline integrates a blind-spot convolution neural network with pre-processing and post-processing steps, including drift correction and low-pass filtering. Results demonstrate that our model outperforms various other ML and non-ML denoising methods in noise reduction and contrast enhancement, leading to improved visual clarity of atomic features. Additionally, the model is drastically faster than U-Net-based ML models and demonstrates excellent out-of-distribution generalization. The model’s computational inference speed is in the order of milliseconds per image, rendering it suitable for application in in-situ HRTEM experiments.

36 MATERIALS SCIENCE↗
NASA NTRS1975

Strapdown cost trend study and forecast

The potential cost advantages offered by advanced strapdown inertial technology in future commercial short-haul aircraft are summarized. The initial procurement cost and six year cost-of-ownership, which includes spares and direct maintenance cost were calculated for kinematic and inertial navigation systems such that traditional and strapdown mechanization costs could be compared. Cost results for the inertial navigation systems showed that initial costs and the cost of ownership for traditional triple redundant gimbaled inertial navigators are three times the cost of the equivalent skewed redundant strapdown inertial navigator. The net cost advantage for the strapdown kinematic system is directly attributable to the reduction in sensor count for strapdown. The strapdown kinematic system has the added advantage of providing a fail-operational inertial navigation capability for no additional cost due to the use of inertial grade sensors and attitude reference computers.

Eberlein, A. J.↗
NASA NTRS1981

Atmospheric emissions photometric imaging experiment /AEPT/ for Spacelab 1

The atmospheric emissions photometric imaging experiment (AEPI) to be flown on Spacelab 1 is designed to study faint natural and artificial atmospheric emission phenomena. Optical emissions are imaged in the region 2150 A to 7320 A using a television system consisting of two optical channels, one wide-angle and one telephoto. The detection system is an image-enhanced SEC vidicon. A third optical channel images onto the photocathode of a microchannel plate photomultiplier tube that has 100 discrete anodes. Photons are counted for each discrete anode, providing a direct measure of the luminosity of an object viewed by the TV telephoto lens, albeit with low spatial resolution. The AEPI detector is mounted on a two-axis gimbal comprised of a Modified Apollo Telescope Mount Star Tracker (MAST), which provides experiment pointing over a 40-deg x 80-deg range, exclusive of restrictions due to the proximity of other experiments. The pointing stability is 1 arcmin with respect to the spacecraft coordinate system for an exposure of 1 second. The tracking capability is 3.5 deg/s with a stability of 1 arcmin. The detector and pointing system are located on the Spacelab pallet. The experiment is controlled by stored programs resident in the Dedicated Experiment Processor located in the Spacelab module.

Sandie, W. G.↗
NASA NTRS1991

Limits on the density of neutral gas within 100 parsecs from observations of the soft X-ray background

Observations are presented in two soft X-ray bands, the Be band (0.077-0.111 keV) and the B-prime (0.105-0.188 keV), for nine directions in the sky. The ratio of count rates in these two bands remains constant as the rates vary by a factor of three, even though the effective interstellar absorption cross sections in the bands differ by a factor of about 3.5. For a model in which the bulk of the observed soft X-ray emission originates in a uniform low-density region surrounding the sun, the constant ratio between the band rates places an upper limit on the amount of neutral material that can be homogeneously mixed with the X-ray-emitting gas. The 2 sigma upper limit on the H I column density over an average path through the local emitting region is 6.6 x 10 to the 18th/sq cm. If the average path length is about 100 pc, then clouds similar to the one in which the sun is embedded could still have a filling factor as large as 25 percent.

Juda, M.↗
NASA NTRS1994

Ultraviolet observations of galaxies with the FAUST experiment

We have used the set of point sources detected by the Far Ultraviolet Space Telescope (FAUST) instrument to identify galaxies and study the total galaxy flux in a 250 A wide band peaking at 1650 A. A sample of 144 galaxies has been obtained after cross-reference with the RC3 catalog, elimination of objects confused with stars and various corrections for the photometry. The UV-B color dispersion is found to increase while the galaxies get redder from late to early types. The irregular galaxies appear on average redder and the Sbc galaxies bluer than indicated by the spectral energy distributions currently used for the calculations of K-corrections. Various arguments lead us to make the assumption of a constant dust extinction within each galaxy. The UV flux per unit area decreases on average from late to early type spirals. We find a weak correlation between the UV and far infra-red emission while the infra-red to UV flux ratio gets lower when galaxies get bluer (as measured by the UV to B flux ratio). The UV flux per unit area correlates with the HI gas surface density and the total gas surface density when this quantity is available. The correlation with the molecular gas alone is weak. In the Virgo cluster, the UV flux per unit area does not decrease in direct proportion to the HI deficiency. Galaxy counts per square degree and per magnitude interval have been obtained at high-galactic latitudes. Combined with data at fainter magnitudes, they show a variation as a function of magnitude with a near-euclidean slope over a range of 8 magnitudes.

Deharveng, J.-M.↗
NASA NTRS2006

A Lidar for Making Range Resolved CO2 Measurements within the Planetary Boundary Layer

A ground based differential absorption lidar is under development at NASA's Goddard Space Flight Center to make range resolved measurements of CO2 within the planetary boundary layer. This is a direct detection lidar designed for both photon counting and analog use. Technology being developed for this instrument will be discussed including efforts in fiber lasers, optical parametric amplifiers and both InGaAs and HgCdTe solid-state detectors. The capabilities of this system are investigated and preliminary results presented.

Burris, John↗
DOE OSTI2025

Quantum dynamics simulation of the advection-diffusion equation

The advection-diffusion equation is simulated via several quantum algorithms. Three formulations are considered: (1) Trotterization, (2) variational quantum time evolution (VarQTE), and (3) adaptive variational quantum dynamics simulation (AVQDS). These schemes were originally developed for the Hamiltonian simulation of many-body quantum systems. The finite-difference discretized operator of the transport equation is formulated as a Hamiltonian and solved without the need for ancillary qubits. Computations are conducted on a quantum simulator (IBM Qiskit Aer) and a superconducting quantum hardware (IBM Fez). The former emulates the latter without the noise. The actual hardware implementation experiences significant noise. The results of the quantum simulator are compared with data from direct numerical simulation (DNS) with infidelities of the order 10 −5 . In the quantum simulator, Trotterization is observed to have the lowest infidelity and is suitable for fault-tolerant computation. The AVQDS algorithm requires the lowest gate count and circuit depth. The VarQTE algorithm is the next best in terms of gate counts, but the number of its optimization variables is directly proportional to the number of qubits. Due to current hardware limitations, Trotterization cannot be implemented, as it has an overwhelmingly large number of operations. Meanwhile, AVQDS and VarQTE can be executed at the hardware level. These algorithms present a new paradigm for computational transport phenomena on quantum computers.

Alipanah, Hirad [Univ. of Pittsburgh, PA (United S↗
NASA NTRS2000

Ammonia 15N/14N Isotope Ratio in the Jovian Atmosphere

Data from the Galileo Probe Mass Spectrometer has been used to derive the N-15/N-14 isotope ratio in ammonia at Jupiter. Although the mass spectral interference from the water contribution to 18 amu makes an accurate derivation of the (N-15)H3/(N-14)H3 ratio difficult from measurements of the singly ionized signals at 18 and 17 amu, this interference is not present in the doubly charged 8.5 and 9.0 amu signals from (N-14)H3++ and (N-15)H3++ respectively. Although the count rate from the 9 amu signal is low during the direct sampling of the atmosphere, the ammonia signal was considerably enhanced during the first enrichment cell (EC1) experiment that measured gas sampled between 0.8 and 2.8 bar. Count rates at 9 amu in the EC1 experiment reach 60/second and measure ammonia sampled from 0.88 to 2.8 bar. In the EC1 measurements the 8.5 amu signal is not measured directly, but can be calculated from the ammonia contribution to 17 amu and the ratio of NH3 ions of a double to single charged observed during a high resolution mass scan taken near the end of the descent. The high resolution scan gives this ratio from ammonia sampled much deeper in the atmosphere. These results are described and compared with Infrared Space Observatory-Short Wavelength Spectrometer (ISO-SWS) observations that give this ratio at 400 mbar.

Mahaffy, P.R.↗
DOE OSTI2023

Characteristics of Veterans With Depression Who Use the Veterans Choice Program of the Veterans Health Administration

Objective: The Veterans Choice Program (VCP) of the Veterans Health Administration (VHA) allowed eligible veterans to use their benefits with participating providers outside the VHA. The authors aimed to identify characteristics of veterans with depression who used or did not use mental health care through the VCP. Methods: In this cross-sectional study, the authors analyzed secondary data from the national VHA Corporate Data Warehouse. VHA administrative data were linked with VCP claims to examine characteristics of VCP-eligible veterans with depression. Further, the study sample included 595,943 unique veterans who were enrolled in the VHA before 2013, were eligible for the VCP in 2016, were alive in 2018, and had an assessed Patient Health Questionnaire–9 (PHQ-9) score or depressive disorder diagnosis documented in the VHA between 2016 and 2018. Results: Veterans who used the VCP had lower medical comorbidity scores and lived in less socioeconomically disadvantaged counties, compared with veterans who received only VHA care. VCP veterans were also more likely to have a PHQ-9 score assessment and to have higher mean depression scores. Mean counts of annual mental health visits per 1,000 veterans were markedly higher for direct VHA care than for care provided via the VCP. As a percentage of the total counts of visits per 1,000 veterans across the VCP and VHA, residential programs and outpatient procedures were the services that were most frequently delivered through the VCP. Conclusions: Between 2016 and 2018, the VCP was used primarily to augment mental health care provided by the VHA, rather than to fill a gap in care.

60 APPLIED LIFE SCIENCES↗