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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Cosmic-ray exposure history of North Ray and South Ray material

Cosmic-ray exposure ages for two breccias, 68815 and 69935, in the vicinity of South Ray Crater give consistent values of 2.0 plus or minus 0.2 m.y. when measured by the Kr-81-Kr, Na-22-Ne, and particle track methods. These also agree with estimates of exposure ages made by others using microcrater counts on six rocks in the same vicinity, including 69935. It is likely that this represents the age of South Ray Crater. Soils from stations close to South Ray Crater appear to be mature, well-irradiated materials containing little, if any, of a 2 m.y. component. Reviewing various lines of evidence, it is concluded that there are no compelling reasons to believe that so-called South Ray soils contain a large fraction of South Ray ejecta. However, if they do contain such ejecta, this material must have been well irradiated in situ prior to being thrown out in the South Ray event. A chip from a large boulder on the rim of North Ray Crater gives a Kr-81-Kr age of 50.6 plus or minus 3.8 m.y. Similar ages are found by the Na-22-Ne and the particle track methods. The agreement of this result with other data on large North Ray boulders fixes the age of North Ray Crater as 50 m.y.

Behrmann, C.↗
DOE OSTI2025

General field evaluation in high-order meshes on GPUs

Robust and scalable function evaluation at any arbitrary point in the finite/spectral element mesh is required for querying the partial differential equation solution at points of interest, comparison of solution between different meshes, and Lagrangian particle tracking. This is a challenging problem, particularly for high-order unstructured meshes partitioned in parallel with MPI, as it requires identifying the element that overlaps a given point and computing the corresponding reference space coordinates. Here, we present a robust and efficient technique for general field evaluation in large-scale high-order meshes with quadrilaterals and hexahedra. In the proposed method, a combination of globally partitioned and processor-local maps are used to first determine a list of candidate MPI ranks, and then locally candidate elements that could contain a given point. Next, element-wise bounding boxes further reduce the list of candidate elements. Finally, Newton’s method with trust region is used to determine the overlapping element and corresponding reference space coordinates. Since GPU-based architectures have become popular for accelerating computational analyses using meshes with tensor-product elements, specialized kernels have been developed to utilize the proposed methodology on GPUs. The method is also extended to enable general field evaluation on surface meshes. The paper concludes by demonstrating the use of the proposed method in various applications ranging from mesh-to-mesh transfer during r-adaptivity to Lagrangian particle tracking.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1976

Preliminary study of contaminant particulates around Skylab

Techniques originally developed for the Skylab T025 contamination experiment were applied to S052 white-light coronagraph data in a preliminary study to investigate particulates around Skylab. Periods were selected which contained some contamination, even though there were no apparent dumps or vents during these periods. Velocity and size distributions were determined from optical data for particles within 200 meters of the spacecraft. Both photographic (61 particle tracks) and video (34 particles) observations yield an upper limit on particle radius of 100 micrometers. Selected photometric data from the S073 zodiacal light experiment during mission SL-2 were also examined for evidence of contamination.

Schuerman, D. W.↗
NASA NTRS1982

Predicting radiation sensitivity of polymers

Recently two independent applications have emerged for highly radiation-sensitive polymers: as resists for production of microelectronic circuitry and as materials to record the tracks of energetic nuclear particles. The relief images used for masking in resist materials are generated by radiation-induced differential dissolution rates, whereas the techniques used in recording nuclear particle tracks employ differential etching processes, that is, development by a chemical etchant that actually degrades the polymer. It is found that the sensitivity of materials to these very different processes is related to their gamma-ray scission efficiency. This correlation provides a predictive capability.

Osullivan, D.↗
NASA NTRS2003

Robust Extraction and Multi-Technique Analysis of Micrometeoroids Captured in Low Earth Orbit

The use of low-density silica aerogel as the primary capture cell technology for the NASA Discovery mission Stardust to Comet Wild-2 [1] is a strong motivation for researchers within the Meteoritics community to develop techniques to handle this material. The unique properties of silica aerogel allow dust particles to be captured at hypervelocity speeds and to remain partially intact. The same unique properties present difficulties in the preparation of particles for analysis. Using tools borrowed from microbiologists, we have developed techniques for robustly extracting captured hypervelocity dust particles and their residues from aerogel collectors[2-3]. It is important not only to refine these extraction techniques but also to develop protocols for analyzing the captured particles. Since Stardust does not return material to Earth until 2006, researchers must either analyze particles that are impacted in the laboratory using light-gasgun facilities [e.g. 41 or examine aerogel collectors that have been exposed in low-Earth orbit (LEO) [5]. While there are certainly benefits in laboratory shots, i.e. accelerating known compositions of projectiles into aerogel, the LEO capture particles offer the opportunity to investigate real particles captured under real conditions. The aerogel collectors used in this research are part of the NASA Orbital Debris Collection Experiment that was exposed on the MIR Space Station for 18 months [5]. We have developed the capability at the UCB Space Sciences Laboratory to extract tiny volumes of aerogel that completely contain each impact event, and to mount them on micromachined fixtures so that they can be analyzed with no interfering support (Fig.1). These aerogel keystones simultaneously bring the terminal particle and the particle track to within 10 m (15 g cm- ) of the nearest aerogel surface. The extracted aerogel wedges containing both the impact tracks and the captured particles have been characterized using the synchrotron total external reflection X-ray fluorescence (TXRF) microprobe at SSRL, the Nuclear Microprobe at LLNL, synchrotron infrared microscopy at the ALS facility at LBL and the NSLS at BNL, and the Total Reflection X-ray Fluorescence (TXRF) facility at SLAC.

Westphal, A. J.↗
DOE OSTI2025

Influence of gradation on shear behavior and pore water response of sand

Here, this paper examines the influence of particle size distribution (PSD) on the shearing behavior of sand using axisymmetric triaxial compression (ATC) testing in conjunction with 3D imaging using synchrotron micro-computed tomography (SMT). Angular sand was sieved to obtain a narrow gradation (uniform) and a wide gradation (non-uniform) with uniformity coefficients (C u ) of 1.2 and 3.0, respectively. Experiments were conducted under drained conditions and a constant effective cell pressure (σ$^{'}_3$) of 50 kPa at low and high back pressures (BP). Results of paired ATC-SMT were analyzed in terms of global constitutive behavior, strain localization, and localized flow characteristics. A new particle tracking algorithm is developed to expose strain localization. Relative particle translation gradient (RPTG) results revealed that gradation affects how early the shear band develops and a tendency for narrow gradation to exhibit varying degrees of diffused shear band at high axial strain (ε 1 ) even though a clear single shear band was observed at the peak strength. Geometric tortuosity (τ) is used as a quantitative parameter to assess flow changes and the efficiency of the flow path. Representative elementary volumes (REVs) inside and outside the shear band were analyzed and the results showed a variation in flow path characteristics where wide gradation specimens had preferential flow paths.

Computed tomography↗
NASA NTRS2003

An Extraction and Curation Technique for Particles Captured in Aerogel Collectors

In 2006, the STARDUST mission will return samples of cometary, interplanetary and interstellar dust captured in aerogel collectors. The curation strategy (or strategies) for STARDUST remain to be defined. Here we present a technique for curation of particles captured in aerogel which will simultaneously preserve the entire particle track, and could allow for the elemental in situ analysis of both the particle residue at the terminus of the track and any particle residues located along the track. This builds on work that we have previously reported elsewhere.

Westphal, A. J.↗
NASA NTRS1972

High Z particle Apollo astronaut dosimetry with plastics

On Apollo missions, the individual astronauts' high Z particle exposure is measured by means of Lexan polycarbonate plastic. These layers form one component of the passive dosimetry packets worn in the constant wear garment. They serve as threshold type, high Z, charged particle track detectors, recording only the very highly ionizing particles. The detectors yield information on the particles' charge, energy, and direction of travel. This data, in turn, is used to obtain the track fluence, the stopping particle density as an integral Z distribution, and the particles' integral LET spectrum. Some of the data gathered on Apollo missions 8-13 is presented.

Benton, E. V.↗
DOE OSTI2024

Growth of organized flow coherent motions within a single-stream shear layer: 4D-PTV measurements

Abstract This study investigates the evolution of a single-stream shear layer (SSSL) originating from a wall boundary layer past a backward-facing step. Utilizing a time-resolved 3D-Particle Tracking Velocimetry (4D-PTV) technique, we track the trajectories of fluorescent particles to gain insight into the flow characteristics of the SSSL. A compact water tunnel facility ( $$\textrm{Re}_\tau =1\,240$$ Re τ = 1 240 ) is fabricated to obtain an SSSL with a perpendicular slow entrainment stream past the separation edge. A hybrid interpolation approach that combines ensemble binning and Gaussian weighting is implemented to derive minimally filtered mean and instantaneous lower- and higher-order flow field parameters. Spanwise-dominant coherent motion accompanied by finer flow scales is observed to grow due to flow entrainment through “nibbling” actions of small-scale vortices, “engulfing” by large-scale vortices, and vortex pairing events. Furthermore, the non-zero-speed stream edge grows relatively faster than the zero-speed stream edge, showing a strong asymmetry in mixing composition across a mixing layer. The SSSL reaches self-similarity at a streamwise distance of $$\approx 55\,\theta _{0}$$ ≈ 55 θ 0 , where $$\theta _0$$ θ 0 is the initial momentum thickness from the separation edge, i.e., considerably shorter than reported in previous studies. A literature comparison of growth rate parameters raises intriguing questions regarding a potential inclusive growth scaling unifying the free shear layers. A turbulent kinetic energy (TKE) budget analysis reveals a negative production region immediately downstream of the separation edge attributed to a large positive streamwise gradient of streamwise velocity. In the self-similar region, the phase-averaged flow mapping demonstrates a larger concentration of turbulence production rate around the outer edges of spanwise vortices, specifically at the intersection of braids and vortices. Furthermore, a spatial separation exists in the regions of peak production and dissipation rates within the vortex core region favoring dissipation. The braids exhibit a larger concentration of turbulence diffusion rates, indicating their function as a conduit for exchanging turbulence between neighboring coherent motions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1999

Tracks to therapy

Studies of the structure of particle tracks have led to models of track effects based on radial dose and radiobiological target theory that have been very successful in describing and predicting track effects in physical, chemical, and biological systems. For describing mammalian cellular inactivation two inactivation modes are required, called gamma-kill and ion-kill, the first due to synergistic effects of delta rays from adjacent ion paths thus resembling the effects from gamma rays, and the second to the effects of single ion transits through a cell nucleus. The ion-kill effect is more severe, where the fraction of cells experiencing ion kill is responsible for a decrease in the oxygen enhancement ratio, and an increase in relative biological effectiveness, but these are accompanied by loss of repair, hence to a reduction in the efficiency of fractionation in high LET therapy, as shown by our calculations for radiobiological effects in the "spread out Bragg Peak".

Review, Tutorial↗
NASA NTRS1993

Optical imaging chamber for X-ray astronomy

The light emitted by electron avalanches in a parallel plate chamber can be used to image the tracks of photoelectrons liberated by the interaction of an incident X-ray with the gas filling the chamber. The differing morphologies of photoelectron tracks and high-energy charged particle tracks can be used for background rejection. The initial direction (before scattering) of the liberated photoelectron also contains information about the polarization of the incident radiation. We have built a small test chamber with which we have imaged photoelectron tracks using an intensified CCD camera. Our results show that optical imaging could be used in a hard X-ray imaging polarimeter useful for astronomy.

Austin, Robert A.↗
NASA NTRS2011

The Super-TIGER Instrument to Probe Galactic Cosmic Ray Origins

Super-TIGER (Super Trans-Iron Galactic Element Recorder) is under construction for the first of two planned Antarctic long-duration balloon flights in December 2012. This new instrument will measure the abundances of ultra-heavy elements (30Zn and heavier), with individual element resolution, to provide sensitive tests of the emerging model of cosmic-ray origins in OB associations and models of the mechanism for selection of nuclei for acceleration. Super-TIGER builds on the techniques of TIGER, which produced the first well-resolved measurements of elemental abundances of the elements 31Ga, 32Ge, and 34Se. Plastic scintillators together with acrylic and silica-aerogel Cherenkov detectors measure particle charge. Scintillating-fiber hodoscopes track particle trajectories. Super-TIGER has an active area of 5.4 sq m, divided into two independent modules. With reduced material thickness to decrease interactions, its effective geometry factor is approx.6.4 times larger than TIGER, allowing it to measure elements up to 42Mo with high statistical precision, and make exploratory measurements up to 56Ba. Super-TIGER will also accurately determine the energy spectra of the more abundant elements from l0Ne to 28Ni between 0.8 and 10 GeV/nucleon to test the hypothesis that microquasars or other sources could superpose spectral features. We will discuss the implications of Super-TIGER measurements for the study of cosmic-ray origins and will present the measurement technique, design, status, and expected performance, including numbers of events and resolution. Details of the hodoscopes, scintillators, and Cherenkov detectors will be given in other presentations at this conference.

Mitchell, John W.↗
DOE OSTI2026

Muon tracking in a LiquidO opaque scintillator detector

LiquidO is an innovative radiation detector concept. The core idea is to exploit stochastic light confinement in a highly scattering medium to self-segment the detector volume. In this paper, we demonstrate event-by-event muon tracking in a LiquidO opaque scintillator detector prototype. The detector consists of a 30 mm cubic scintillator volume instrumented with 64 wavelength-shifting fibres arranged in an 8 × 8 grid with a 3.2 mm pitch and read out by silicon photomultipliers. A wax-based opaque scintillator with a scattering length of approximately 0.5 mm is used. The tracking performance of this LiquidO detector is characterised with cosmic-ray muons and the position resolution is demonstrated to be 450 μm per row of fibres. These results highlight the potential of LiquidO opaque scintillator detectors to achieve fine spatial resolution, enabling precise particle tracking and imaging.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Determining Optimal Running Conditions for TinyTPC Detector

Liquid argon time projection chambers, (LArTPCs), are particle detectors used to collect ionization charge information from particle trajectories, facilitating detailed particle track analysis. They are currently used as particle detectors in major physics projects such as the deep underground neutrino experiment (DUNE), to detect and study the nature of the elusive neutrino particle. TinyTPC is a small scale LArTPC featuring a pixelated readout system (LArPix) that we will use to study liquid argon doping. We expect this doping to enhance the resolution of LAr detectors, especially for low energy particles below 10 MeV which would expand the capabilities of currently running experiments. Housed within a cryostat filled with liquid argon, the TinyTPC will rely on a high and a low voltage system to collect data. In preparation for deployment we found and resolved issues in the HV and LV systems and we determined optimal running conditions in a test vessel. This presentation will go over the detector commissioning process that enabled data taking with the TinyTPC.

Gonzalez, Rebecca↗
DOE OSTI2026

Simulation of electron Bernstein waves using FullWave with a 2D non-local hot plasma model

Hot plasma wave simulation capability is expanded in the FullWave code by updating the hybrid iterative solver in the code with a semi-implicit time stepping method. The new approach is used to simulate Electron Bernstein Wave (EBW) heating in over-dense spherical tokamak plasmas. The code’s hybrid iterative solver circumvents the prohibitive memory cost of direct methods by combining a time evolution of Maxwell’s equations with frequency-domain relaxation, while the conductivity kernel, calculated via 3D particle tracking, captures the essential non-local wave–particle interactions. One-dimensional EBW simulations verify the algorithm’s accuracy by demonstrating mode conversion from X-mode wave to EBW at the upper hybrid resonance and a strong cyclotron damping near the plasma core. Two-dimensional simulation reproduces the predicted short EBW wavelength and quantitatively matches the hot-plasma dispersion relation. This study demonstrates the fidelity of the hybrid solver for the electron cyclotron frequency range.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1974

Particle flow in blade passages of turbomachinery with application to laser-Doppler velocimetry

A theoretical analysis was conducted of the dynamic behavior of micron size particles entrained in gas flow on the two-dimensional blade-to-blade surface of a circular stationary cascade of turbine stator blades. The particle velocity lag and angular deviation relative to the gas was determined as a function of particle diameter and mass density. Particles size and density were varied over ranges selected to correspond to typical laser-Doppler velocimeter (LDV) flow field mapping applications. It was found that velocity lag and angular deviation increased whenever particle size or mass density increased, and that particle tracking was more sensitive to a change in particle diameter than to a change in mass density. Results indicated that LDV applications employing 1 gm/cc tracer particles with diameters greater than approximately 1 micron, or 0.5 micron diameter particles with mass densities greater than 4 gm/cc would experience velocity and angular deviations generally greater than 2 percent and 1 degree, respectively.

Maxwell, B. R.↗
NASA NTRS1975

The fission track record of Apennine Front KREEP basalts

Whitlockite grains in two Apennine Front KREEP soil fragments contain extremely high densities of fission tracks. A new method is described in which particle tracks are examined in an actinide-poor phase bordering an actinide-rich whitlockite phase. This method clearly distinguishes the fission track contributions from other track sources; e.g., Fe-group cosmic rays, spallation recoils, and dislocations. Observed track excesses, when corrected for U- and Th-related fission sources, are 4-20 times greater than the contribution from spontaneous fission of U-238 (based on an age of 4 b.y.), and probably represent a large and variable contribution from the fission of Pu-244. These fragments may have pre-Imbrium ages, underscoring the importance of KREEP as a constituent of the pre-mare lunar crust. Track excesses are not correlated with the U or Th contents of the whitlockite grains. This behavior suggests that Pu fractionates differently from U and Th in lunar igneous KREEP.

Haines, E. L.↗