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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,387 records · Page 77

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NASA NTRS1981

Inference of the ring current ion composition by means of charge exchange decay

The analysis of data from the Explorer 45 (S3-A) electrostatic analyzer in the energy range 5-30 keV has provided some new results on the ring current ion composition. It has been well established that the storm time ring current has a decay time of several days, during which the particle fluxes decrease nearly monotonically. By analyzing the measured ion fluxes during the several day storm recovery period and assuming that beside hydrogen other ions were present and that the decays were exponential in nature, three separate lifetimes for the ions were established. These fitted decay lifetimes are in excellent agreement with the expected charge exchange decay lifetimes for H(+), O(+) and He(+) in the energy and L value range of the data.

Smith, P. H.↗

NASA NTRS1983

Particulate erosion mechanisms

Particulate damage and erosion of ductile metals are today plaguing design and field engineers in diverse fields of engineering and technology. It was found that too many models and theories were proposed leading to much speculation from debris analysis and failure mechanism postulations. Most theories of solid particle erosion are based on material removal models which do not fully represent the actual physical processes of material removal. The various mechanisms proposed thus far are: melting, low-cycle fatigue, extrusion, delamination, shear localization, adhesive material transfer, etc. The experimental data on different materials highlighting the observed failure modes of the deformation and cutting wear processes using optical and scanning electron microscopy are presented. The most important mechanisms proved from the experimental observations of the specimens exposed to both spherical and angular particles are addressed, and the validity of the earlier theories discussed. Both the initial stages of damage and advanced stages of erosion were studied to gain a fundamental understanding of the process.

Veerabhadrarao, P.↗

NASA NTRS1987

Dynamical studies of Saturn's rings

Several investigations of Saturn's rings employing data from three Voyager experiments are discussed. These investigations concentrated on the regularily organized C ring. A search for eccentric or inclined features, a photometric study of regions of different optical depth, an analysis of wavelike structures at three locations, and a study of the size distribution of meter-sized particles are dicussed.

Nicholson, Philip D.↗

NASA NTRS1988

Instrumentation for gamma-ray astronomy

The current status of gamma-ray-telescope technology for ground, airborne, and space observations is surveyed and illustrated with drawings, diagrams, and graphs and tables of typical data. For the low- and medium-energy ranges, consideration is given to detectors and detector cooling systems, background-rejection methods, radiation damage, large-area detectors, gamma-ray imaging, data analysis, and the Compton-interaction region. Also discussed are the gamma-ray interaction process at high energies; multilevel automated spark-chamber gamma-ray telescopes; the Soviet Gamma-1 telescope; the EGRET instrument for the NASA Gamma-Ray Observatory; and Cerenkov, air-shower, and particle-detector instruments for the TeV and PeV ranges. Significant improvements in resolution and sensitivity are predicted for the near future.

Bertsch, David L.↗

NASA NTRS1990

Analysis of troposphere-stratosphere exchange

The overall goal is to improve our understanding of stratosphere-troposphere exchange processes in the tropics and midlatitudes. Specifically, modeling and analysis are performed using aircraft, radiosonde, and satellite data from the 1980 and 1987 NASA tropical field experiments in Panama and Australia, respectively, and the 1986 NASA jet stream field experiment in California. The objectives are to: (1) examine the structure of ozone, temperature, horizontal winds, tropospheric tracers, water and ice particles, and water vapor within, around, and above cumulus anvils in the tropics and jet streams in midlatitudes; (2) establish the presence, during each of the experimental periods, of various potential mechanisms of exchange, such as direct injection by cumulus, gravity wave fluxes, turbulent fluxes, and radiative heating; and (3) evaluate quantitatively, if possible, the mass of air transferred by these mechanisms during specific transport events.

Pfister, Leonhard↗

NASA NTRS1995

Regions of abnormally low proton temperature as signatures of ejecta: Solar cycle dependence and association with other ejecta signatures

Solar wind proton temperatures lower than expected for 'normal' solar wind expansion are a common signature of 'ejecta' (i.e. interplanetary coronal mass ejections). We have surveyed the OMNI solar wind data base for 1965-1991, and Helios data for 1974-1980, to identify regions of abnormally low temperatures. Their occurrence rate is clearly dependent on solar activity levels, in particular when the minority of events associated with encounters with the heliospheric plasma sheet are excluded. The analysis of the OMNI data may provide an indication of the rate of ejecta at the Earth, and hence of the CME rate, extending back to before spacecraft coronagraph observations became available in the early 1970's. We discuss the association of these solar wind structures with cosmic ray depressions bidirectional particle flows, and other ejecta signatures. Our impression is that no one ejecta signature provides a truly comprehensive indication of the presence of ejecta, but that abnormally low temperature depressions encompass most of the regions identified by these other individual signatures.

Richardson, I. G.↗

NASA NTRS1999

Predicting Slag Generation in Sub-Scale Test Motors Using a Neural Network

Generation of slag (aluminum oxide) is an important issue for the Reusable Solid Rocket Motor (RSRM). Thiokol performed testing to quantify the relationship between raw material variations and slag generation in solid propellants by testing sub-scale motors cast with propellant containing various combinations of aluminum fuel and ammonium perchlorate (AP) oxidizer particle sizes. The test data were analyzed using statistical methods and an artificial neural network. This paper primarily addresses the neural network results with some comparisons to the statistical results. The neural network showed that the particle sizes of both the aluminum and unground AP have a measurable effect on slag generation. The neural network analysis showed that aluminum particle size is the dominant driver in slag generation, about 40% more influential than AP. The network predictions of the amount of slag produced during firing of sub-scale motors were 16% better than the predictions of a statistically derived empirical equation. Another neural network successfully characterized the slag generated during full-scale motor tests. The success is attributable to the ability of neural networks to characterize multiple complex factors including interactions that affect slag generation.

Wiesenberg, Brent↗

NASA NTRSDate not supplied

On the Importance of Producing and Characterizing Laboratory Analogs of Cosmic Grains, Planetary Atmospheric Aerosols, and Surface Materials

Carbonaceous dust and aerosols have been observed in interstellar/circumstellar and planetary environments. Dedicated laboratory experiments have been developed to produce analogs of these solid materials under different experimental conditions (molecular precursors, temperature, pressure, energy source…). These experimental studies are key to investigating the physical and chemical processes that drive the formation of solid particles from gas and solid phase molecular precursors in astrophysical and planetary environments. They also allow the characterization of the physical, optical, and chemical properties of these laboratory-generated analogs, hence providing critical information that can be used as input parameters in models for the analysis and interpretation of observational data. Here, as an example of these laboratory efforts, we will present various studies that combined (1) experiments performed with the NASA Ames COSmIC facility to produce analogs of Titan’s atmospheric aerosols and cosmic grains from gas phase molecular precursors, and (2) the characterization of these analogs with the NASA Ames Optical Constants Facility (OCF) to provide the real and imaginary parts of their refractive indices, n + ik, to the community, from the visible to the far-infrared (0.59–200 µm, 16,950–50 per cm). We will also discuss the importance of the wavelength and spectral range coverage of these optical constants, n and k, for their use in radiative transfer, atmospheric and reflectance models, and present a new effort to develop an Optical Constant database (OCdb) to provide this critical data to the scientific community.

Cosmic Grains↗

DOE OSTI2024

Spatially Resolved Raman Spectroscopic Investigation of Uranyl Fluoride: A Case Study in the Importance of Instrument Optimization

Raman spectroscopy is an emerging technique for rapid and nondestructive analysis of nuclear materials for forensic and nonproliferation applications as it is a powerful tool for distinguishing multiple chemical forms of materials with similar stoichiometries. Recent developments in spectroscopic software have enabled rapid data collection with high-speed Raman spectroscopic mapping capabilities. However, some uranium-rich materials are susceptible to degradation in humid air and/or laser-induced phase transformations. To mitigate environmental or measurement-related sample degradation of potential samples of interest, we have taken a systematic approach to define optimized data collection parameters for high-throughput measurements of uranyl fluoride (UO 2 F 2 ), which is an important intermediate material in the nuclear fuel cycle. First, we systematically describe the influence of optical magnification (5× to 100×), laser power, and exposure time on obtained signal for identical particles of UO 2 F 2 and find that at low laser power and exposure times, comparable signal is obtained regardless of optical magnification. Second, we ensure sample integrity during data collection, and third, collect spectroscopic maps that employ optimized parameters to reduce the time required to obtain spatially resolved spectroscopic information. Reductions of 90% and 99% in measurement times are discussed as they relate to differences in resolving spectroscopic features of particles in identical mapping areas. Finally, during this work, we found that additional data processing options were needed and thus developed a customized Python script for importing, processing, analyzing, and visualizing Raman spectroscopic map data.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2023

Review of multi-faceted morphologic signatures of actinide process materials for nuclear forensic science

Particle morphology is an emerging signature that has the potential to identify the processing history of unknown nuclear materials. Using readily available scanning electron microscopes (SEM), the morphology of nearly any solid material can be measured within hours. Coupled with robust image analysis and classification methods, the morphological features can be quantified and support identification of the processing history of unknown nuclear materials. The viability of this signature depends on developing databases of morphological features, coupled with a rapid data analysis and accurate classification process. With developed reference methods, datasets, and throughputs, morphological analysis can be applied within days to (i) interdicted bulk nuclear materials (gram to kilogram quantities), and (ii) trace amounts of nuclear materials detected on swipes or environmental samples. In conclusion, this review aims to develop validated and verified analytical strategies for morphological analysis relevant to nuclear forensics.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Evaluating the ProtoDUNE-SP Detector Performance to Measure a 6 GeV/c Positive Kaon Inelastic Cross Section on Argon

The ProtoDUNE Single-Phase Liquid Argon Time Projection Chamber \\ (ProtoDUNE-SP LArTPC) is a prototype for the Deep Underground Neutrino Experiment (DUNE), a future long-baseline neutrino oscillation experiment. Based at the CERN Neutrino Platform, ProtoDUNE-SP LArTPC collected data from a charged test beam in the fall of 2018. It then took data of cosmic-ray muons from November 2018 to the summer of 2020. The main goals of the prototype were to measure parameters related to charged particle passage in argon and evaluate the performance of the detector to inform future DUNE Far Detector development. The test beam provided kaons, pions, muons, protons, and electrons to the detector. These particles represent common final state particles in neutrino interactions, therefore providing information to DUNE on modeling charged particles in argon for its neutrino physics program. In addition to neutrino physics, DUNE has proposed an analysis using the DUNE Far Detector module to set limits for proton decay through the decay channel $p\rightarrow K^++\bar{\nu}$. This measurement would require information on kaons in argon, providing ProtoDUNE-SP LArTPC another opportunity to aid DUNE. This thesis describes the calibration of ProtoDUNE-SP and its detector performance, which serves as a benchmark for the performance of the DUNE Far Detector modules. A specific calibration highlighted is the evaluation of the liquid argon purity in the detector. These measurements use cosmic-ray muons reconstructed in the detector that are calibrated and matched to data from scintillator strips external to the TPC, known as the Cosmic Ray Tagger (CRT). The thesis will discuss the algorithms to match the data between the ProtoDUNE-SP LArTPC and the CRT and discuss the liquid argon purity measurements using one of the algorithms. Data sets of calibrated tracks measured the liquid argon contamination as consistently below 100 ppt oxygen equivalent. After these discussions on the ProtoDUNE-SP LArTPC detector, the thesis will present an evaluation of the inclusive inelastic, sometimes referred to as a reactive, cross section on argon of kaons from the ProtoDUNE-SP test beam with an average momentum of 6 GeV/c.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2020

Results on low-mass weakly interacting massive particles from a 11 kg-day target exposure of DAMIC at SNOLAB

We present constraints on the existence of weakly interacting massive particles (WIMPs) from a 11 kg-day target exposure of the DAMIC experiment at the SNOLAB underground laboratory. The observed energy spectrum and spatial distribution of ionization events with electron-equivalent energies $>$200 eV$_{\rm ee}$ in the DAMIC CCDs are consistent with backgrounds from natural radioactivity. An excess of ionization events is observed above the analysis threshold of 50 eV$_{\rm ee}$. While the origin of this low-energy excess requires further investigation, our data exclude spin-independent WIMP-nucleon scattering cross sections $\sigma_{\chi-n}$ as low as $3\times 10^{-41}$ cm$^2$ for WIMPs with masses $m_{\chi}$ from 7 to 10 GeV$c^{-2}$ . These results are the strongest constraints from a silicon target on the existence of WIMPs with $m_{\chi}$$<$9 GeV$c^{-2}$ and are directly relevant to any dark matter interpretation of the excess of nuclear-recoil events observed by the CDMS silicon experiment in 2013.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

The information content of jet quenching and machine learning assisted observable design

Jets produced in high-energy heavy-ion collisions are modified compared to those in proton-proton collisions due to their interaction with the deconfined, strongly-coupled quark-gluon plasma (QGP). In this work, we employ machine learning techniques to identify important features that distinguish jets produced in heavy-ion collisions from jets produced in proton-proton collisions. We formulate the problem using binary classification and focus on leveraging machine learning in ways that inform theoretical calculations of jet modification: (i) we quantify the information content in terms of Infrared Collinear (IRC)-safety and in terms of hard vs. soft emissions, (ii) we identify optimally discriminating observables that are in principle calculable in perturbative QCD, and (iii) we assess the information loss due to the heavy-ion underlying event and background subtraction algorithms. We illustrate our methodology using Monte Carlo event generators, where we find that important information about jet quenching is contained not only in hard splittings but also in soft emissions and IRC-unsafe physics inside the jet. This information appears to be significantly reduced by the presence of the underlying event. We discuss the implications of this for the prospect of using jet quenching to extract properties of the QGP. Since the training labels are exactly known, this methodology can be used directly on experimental data without reliance on modeling. We outline a proposal for how such an experimental analysis can be carried out, and how it can guide future measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Large-x partons from Jefferson Lab to the LHC

This project addressed the longitudinal quark and gluon structure of hadrons, a key topic in the 2015 and 2023 NSAC long range plans for nuclear science. The research encompassed and combined theoretical studies with advanced Quantum Chromo Dynamics (QCD) analysis of experimental data, from Jefferson Lab to the Large Hadron Collider. The results have pushed the boundaries in both aspects, and capitalized on the results and methods developed in previous grant renewals.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Measurement of Rayleigh Scattering in Liquid Argon at Vacuum Ultraviolet Wavelengths

Liquid argon based detectors are limited in scintillation light analysis capabilities due to inconsistent measurements of fundamental constants essential for the reconstruction of scintillation events. This experiment measures the Rayleigh scattering length of vacuum ultraviolet light propagating in liquid argon in support of liquid argon experiments. Preliminary results are presented for the Rayleigh scattering length in a range of vacuum ultraviolet wavelengths. Current data collection and analysis methods in this measurement require further advancements to understand and eliminate anomalous phenomena in the data. Future measurements in this experiment aim to precisely measure the liquid argon ultraviolet light scattering length. Results will contribute to the development of new photon system analysis methods for liquid argon experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

QLBT: a linear Boltzmann transport model for heavy quarks in a quark-gluon plasma of quasi-particles

Abstract We develop a new heavy quark transport model, QLBT, to simulate the dynamical propagation of heavy quarks inside the quark-gluon plasma (QGP) created in relativistic heavy-ion collisions. Our QLBT model is based on the linear Boltzmann transport (LBT) model with the ideal QGP replaced by a collection of quasi-particles to account for the non-perturbative interactions among quarks and gluons of the hot QGP. The thermal masses of quasi-particles are fitted to the equation of state from lattice QCD simulations using the Bayesian statistical analysis method. Combining QLBT with our advanced hybrid fragmentation-coalescence hadronization approach, we calculate the nuclear modification factor $$R_\mathrm {AA}$$ R AA and the elliptic flow $$v_2$$ v 2 of D mesons at the Relativistic Heavy-Ion Collider and the Large Hadron Collider. By comparing our QLBT calculation to the experimental data on the D meson $$R_\mathrm {AA}$$ R AA and $$v_2$$ v 2 , we extract the heavy quark transport parameter $$\hat{q}$$ q ^ and diffusion coefficient $$D_\mathrm {s}$$ D s in the temperature range of $$1-4~T_\mathrm {c}$$ 1 - 4 T c , and compare them with the lattice QCD results and other phenomenological studies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS2010

A First-Order Radiative Transfer Model for Microwave Radiometry of Forest Canopies at L-Band

In this study, a new first-order radiative transfer (RT) model is developed to more accurately account for vegetation canopy scattering by modifying the basic r-co model (the zero-order RT solution). In order to optimally utilize microwave radiometric data in soil moisture (SM) retrievals over moderately to densely vegetated landscapes, a quantitative understanding of the relationship between scattering mechanisms within vegetation canopies and the microwave brightness temperature is desirable. A first-order RT model is used to investigate this relationship and to perform a physical analysis of the scattered and emitted radiation from vegetated terrain. The new model is based on an iterative solution (successive orders of scattering) of the RT equations up to the first order. This formulation adds a new scattering term to the i-w model. The additional term represents emission by particles (vegetation components) in the vegetation layer and emission by the ground that is scattered once by particles in the layer. The new model is tested against 1.4 GHz brightness temperature measurements acquired over deciduous trees by a truck-mounted microwave instrument system called ComRAD in 2007. The model predictions are in good agreement with the data and they give quantitative understanding for the influence of first-order scattering within the canopy on the brightness temperature. The model results show that the scattering term is significant for trees and modifications are necessary to the T-w model when applied to dense vegetation. Numerical simulations also indicate that the scattering term has a negligible dependence on SM and is mainly a function of the angle and polarization of the microwave observation.

Kurum, Mehmet↗

DOE OSTI2026

Strangeness enhancement at its extremes: multiple (multi-)strange hadron production in pp collisions at $\sqrt{s}=5.02$ TeV

The probability to observe a specific number of strange and multi-strange hadrons (nS), denoted as P(nS), is measured by ALICE at midrapidity (|y| < 0.5) in $$\sqrt{s}=5.02$$ TeV proton-proton (pp) collisions, dividing events into several multiplicity-density classes. Exploiting, for the first time, a technique based on counting the number of strange-particle candidates event-by-event, this measurement allows one to extend the study of strangeness production beyond the mean of the distribution. This constitutes a new test bench for production mechanisms, probing events with a large imbalance between strange and non-strange content. The analysis of a large-statistics data sample makes it possible to extract P(nS) up to a maximum nS of 7 for $${\text{K}}_{\text{S}}^{0}$$, 5 for Λ and $$\overline{\Lambda }$$, 4 for Ξ− and $${\overline{\Xi } }^{+}$$, and 2 for Ω− and $${\overline{\Omega } }^{+}$$. From this, the probability of producing strange hadron multiplets per event is calculated, thereby enabling the extension of the study of strangeness enhancement to extreme situations where several strange quarks hadronize in a single event at midrapidity. Moreover, comparing hadron combinations with different u and d quark compositions and equal overall s quark content, the contribution to the enhancement pattern coming from non-strangeness related mechanisms is isolated. The results are compared with state-of-the-art phenomenological models implemented in commonly used Monte Carlo event generators, including PYTHIA 8 Monash 2013, PYTHIA 8 with QCD-based Color Reconnection and Rope Hadronization (QCD-CR + Ropes), and EPOS LHC, which incorporates both partonic interactions and hydrodynamic evolution. These comparisons show that the new approach dramatically enhances the sensitivity to the different underlying physics mechanisms modeled by each generator.

Abualrob, I J↗