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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Pair Production and Gamma-Ray Emission in the Outer Magnetospheres of Rapidly Spinning Young Pulsars

Electron-positron pair production and acceleration in the outer magnetosphere may be crucial for a young rapidly spinning canonical pulsar to be a strong Gamma-ray emitter. Collision between curvature radiated GeV photons and soft X-ray photons seems to be the only efficient pair production mechanism. For Crib-like pulsars, the magnetic field near the light cylinder is so strong, such that the synchrotron radiation of secondary pairs will be in the needed X-ray range. However, for majority of the known Gamma-ray pulsars, surface emitted X-rays seem to work as the matches and fuels for a gamma-ray generation fireball in the outer magnetosphere. The needed X-rays could come from thermal emission of a cooling neutron star or could be the heat generated by bombardment of the polar cap by energetic particles generated in the outer magnetosphere. With detection of more Gamma-ray pulsars, it is becoming evident that the neutron star's intrisic geometry (the inclination angle between the rotation and magnetic axes) and observational geometry (the viewing angle with respect to the rotation axis) are crucial to the understanding of varieties of observational properties exhibited by these pulsars. Inclination angles for many known high energy Gamma-ray pulsars appear to be large and the distribution seems to be consistent with random orientation. However, all of them except Geminga are pre-selected from known radio pulsars. The viewing angles are thus limited to be around the respective inclination angles for beamed radio emission, which may induce strong selection effect. The viewing angles as well as the inclination angles of PSR 1509-58 and PSB 0656+14 may be small such that most of the high energy Gamma-rays produced in the outer accelerators may not reach the observer's direction. The observed Gamma-rays below 5 MeV from this pulsar may be synchrotron radiation of secondary electron-positron pairs produced outside the accelerating regions.

Ruderman, Malvin↗
NASA NTRS1985

Correcting for particle counting bias error in turbulent flow

An ideal seeding device is proposed generating particles that exactly follow the flow out are still a major source of error, i.e., with a particle counting bias wherein the probability of measuring velocity is a function of velocity. The error in the measured mean can be as much as 25%. Many schemes have been put forward to correct for this error, but there is not universal agreement as to the acceptability of any one method. In particular it is sometimes difficult to know if the assumptions required in the analysis are fulfilled by any particular flow measurement system. To check various correction mechanisms in an ideal way and to gain some insight into how to correct with the fewest initial assumptions, a computer simulation is constructed to simulate laser anemometer measurements in a turbulent flow. That simulator and the results of its use are discussed.

Edwards, R. V.↗
NASA NTRS1974

Ferrographic analysis of wear debris from boundary lubrication experiments with a five-ring polyphenyl ether

The types of wear particles generated by a five-ring polyphenyl ether in boundary lubrication experiments in various atmospheres were determined by ferrographic analysis. The types of wear particles observed included cylindrical or rocklike organometallic debris, adhesive and cutting wear particles, and some spherical debris. Interpretations as to the mechanism of generation of the various types of particles are presented.

Jones, W. R., Jr.↗
NASA NTRS1974

Ferrographic analysis of wear debris from boundary lubrication experiments with a five ring polyphenyl ether

The types of wear particles generated by a five-ring polyphenyl ether in boundary lubrication experiments in various atmospheres were determined by ferrographic analysis. The types of wear particles observed included: cylindrical or rock-like organo-metallic debris, adhesive and cutting wear particles, and some spherical debris. Interpretations as to the mechanism of generation of the various types of particles are presented.

Jones, W. R., Jr.↗
DOE OSTI2023

Monitoring and characterization of particle contamination in the pulse compression chamber of the OMEGA EP laser system

The laser-damage performance of optics is known to be negatively affected by microscale particle contamination induced by the operational environment. This work investigates the properties of particles accumulating in various locations near critical optics inside the OMEGA EP grating compressor chamber during quarterly operational periods over a 2-year duration. The particles found were characterized using optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The analysis indicates significant concentrations of micrometer- to nanometer-scale particles inside the vacuum chamber, with higher values observed near the port leading to the OMEGA EP target chamber. The distribution of the chemical composition of these particles varies between collection periods. Although understanding of the mechanisms of particle generation and transport remains uncertain, the hypothesis is that this particle load represents a risk for contaminating the surfaces of high-value optics located inside the chamber, including the compression gratings and deformable mirrors, and therefore affecting their laser-damage resistance and overall operational lifetime.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Next-Generation Video Ice Particle Sampler Field Campaign Report

The next-generation video ice particle sampler (ngVIPS) was operated on the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) user facility’s tethered balloon system (TBS) during the IFFExO (Ice Fog Field Experiment at Oliktok Point) project in November, 2020. The purpose of the project was to study ice fog microphysics and the environmental conditions during ice fog to enable better predictions during low-visibility conditions. This project was conducted at the site of the third ARM Mobile Facility (AMF3) at Oliktok Point, Alaska. Among a suite of other instruments, the ngVIPS was operated to observe atmospheric ice particles.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Wino and Real Minimal Dark Matter Excluded by Fermi Gamma-Ray Observations

We show that minimal, fermionic dark matter (DM) models in the $n$-dimensional representation of the weak force with zero hypercharge that make up 100% of the DM under the standard cosmological history are strongly excluded for $n < 9$. This includes the thermal wino, which we show is ruled out even allowing for DM core sizes up to $\sim$6.7 kpc with the preferred local DM density or $\sim$3.7 kpc in addition to the local DM density being half the preferred value, at less than $0.2$ GeV/cm$^3$. We reach these conclusions through dedicated searches with 14 years of Fermi gamma-ray data in the inner Galaxy between 30 GeV and 2 TeV for the continuum gamma-rays produced in the decays of unstable particles produced in DM annihilation and bound-state formation processes. We consider a variety of Milky Way DM profiles in our analyses, including those motivated by modern hydrodynamic cosmological simulations, and show that all the $n < 9$ minimal DM models are disfavored even under the most conservative assumptions for these density profiles. While wino, quintuplet ($n=5$), and $n = 7$ DM models are strongly disfavored by our analyses under the standard cosmology, we discuss how non-standard cosmological histories or DM sub-fractions could still allow for these particles to be realized in nature, with discovery opportunities at next-generation particle colliders and gamma-ray telescopes.

Cosmology and Nongalactic Astrophysics (astro-ph.C↗
NASA NTRS1977

Ferrographic analysis of wear debris generated in accelerated rolling element fatigue tests

Ferrographic analysis was used to determine the types and quantities of wear particles generated during accelerated rolling contact fatigue tests. The NASA five-ball rolling contact fatigue tester was used. Ball specimens were made of AMS 5749, a corrosion-resistant high-temperature bearing steel. The lubricant was a super-refined naphthenic mineral oil. Conditions included a maximum Hertz stress of 5.52 billion Pa and a shaft speed of 10,000 rpm. Four types of wear particles were observed: normal rubbing wear particles, fatigue spall particles, spheres, and friction polymer.

Jones, W. R., Jr.↗
DOE OSTI2023

New signature method for identifying organic material in atmosphere and water samples

The levels of plastic contamination in the earth’s oceans have steadily increased over the past century, creating a threat to marine life and increasing climate change. Several methods have been developed over the past decade to try to determine the amount and accumulation rate of plastic impurities in the ecosystem. These methods have proven promising but suffer from long measurement times, bulky non-mobile systems, and sample degradation. We propose a smaller, faster system that employs an electron beam to examine seawater samples for polyethylene contamination levels. This process generates a full electron and photon energy spectrum analyses based on the subatomic particles generated from electron interactions. Our simulations have already been developed based on the known molecular composition of seawater and polyethylene, showing the possibility of discerning molecular plastics from microorganisms. With a system the size of a suitcase, this system would be easily deployable to remote locations around the world or installed as a monitoring system for manufacturing facilities. This concept could lead to a new methodology for the science of signatures and be applied to other biological hazard investigations, such as general virus detection.

43 PARTICLE ACCELERATORS↗
NASA NTRS1996

Soot Imaging and Measurement

Soot, sometimes referred to as smoke, is made up primarily of the carbon particles generated by most combustion processes. For example, large quantities of soot can be seen issuing from the exhaust pipes of diesel-powered vehicles. Heated soot also is responsible for the warm orange color of candle flames, though that soot is generally consumed before it can exit the flame. Research has suggested that heavy atmospheric soot concentrations aggravate conditions such as pneumonia and asthma, causing many deaths each year. To understand the formation and oxidation of soot, NASA Lewis Research Center scientists, together with several university investigators, are investigating the properties of soot generated in reduced gravity, where the absence of buoyancy allows more time for the particles to grow. The increased time allows researchers to better study the life cycle of these particles, with the hope that increased understanding will lead to better control strategies. To quantify the amount of soot present in a flame, Lewis scientists developed a unique imaging technique that provides quantitative and qualitative soot data over a large field of view. There is significant improvement over the single-point methods normally used. The technique is shown in the sketch, where light from a laser is expanded with a microscope objective, rendered parallel, and passed through a flame where soot particles reduce the amount of light transmitted to the camera. A filter only allows light at the wavelength of the laser to pass to the camera, preventing any extraneous signals. When images of the laser light with and without the flame are compared, a quantitative map of the soot concentration is produced. In addition to that data, a qualitative image of the soot in the flame is also generated, an example of which is displayed in the photo. This technique has the potential to be adapted to real-time process control in industrial powerplants.

Source record↗
DOE OSTI2025

Accurate models of the added mass force of a uniform random distribution of spherical particles or bubbles

The added mass force resulting from the acceleration of a body in a fluid is of fundamental and practical interest in dispersed multiphase flows. Euler–Lagrange (EL) and Euler–Euler (EE) simulations require closure terms for the added mass force in order to accurately couple the conserved variables between phases. Presently, a more thorough understanding of the added mass force in a multi-particle system is developed based on potential flow resulting in a resistance matrix formulation analogous to Stokesian dynamics. This formulation is then used to generate a dataset of added mass resistance matrices for large systems of randomly generated particles. This methodology is used to create a volume fraction corrected binary model for predicting the added mass force in large systems as well as generate statistics of the added mass force in such systems. This work provides clarification to the theory of the added mass force for particle clouds, and modelling options that may be implemented in existing EL and EE codes.

42 ENGINEERING↗
NASA NTRS2022

Spectral Power-law Formation by Sequential Particle Acceleration in Multiple Flare Magnetic Islands

We present a first-principles model of pitch-angle and energy distribution function evolution as particles are sequentially accelerated by multiple flare magnetic islands. Data from magnetohydrodynamic (MHD) simulations of an eruptive flare/coronal mass ejection provide ambient conditions for the evolving particle distributions. Magnetic islands, which are created by sporadic reconnection at the self-consistently formed flare current sheet, contract and accelerate the particles. The particle distributions are evolved using rules derived in our previous work. In this investigation, we assume that a prescribed fraction of particles sequentially "hops" to another accelerator and receives an additional boost in energy and anisotropy. This sequential process generates particle number spectra that obey an approximate power law at mid-range energies and presents low- and high-energy breaks. We analyze these spectral regions as functions of the model parameters. We also present a fully analytic method for forming and interpreting such spectra, independent of the sequential acceleration model. The method requires only a few constrained physical parameters, such as the percentage of particles transferred between accelerators, the energy gain in each accelerator, and the number of accelerators visited. Our investigation seeks to bridge the gap between MHD and kinetic regimes by combining global simulations and analytic kinetic theory. The model reproduces and explains key characteristics of observed flare hard X-ray spectra as well as the underlying properties of the accelerated particles. Our analytic model provides tools to interpret high-energy observations for missions and telescopes, such as RHESSI, FOXSI, NuSTAR, Solar Orbiter, EOVSA, and future high-energy missions.

magnetic reconnection↗
DOE OSTI2020

Experimental demonstration of externally driven millimeter-wave particle accelerator structure

We report the experimental demonstration of a mm-wave electron accelerating structure powered by a high-power rf source. We demonstrate reliable coupling of an unprecedented rf power—up to 575kW into the mm-wave accelerator structure using a quasi-optical setup. This standing wave accelerating structure consists of a single-cell copper cavity and a Gaussian to TM 01 mode converter. The accelerator structure is powered by 110 GHz, 10-ns long rf pulses. These pulses are chopped from 3 microsecond pulses from a gyrotron oscillator using a laser-driven silicon switch. We show an unprecedented high gradient up to 230MV/m that corresponds to a peak surface electric field of more than 520 MV/m. We have achieved these results after conditioning the cavity with more than 100,000 pulses. We also report preliminary measurements of rf breakdown rates, which are important for understanding rf breakdown physics in the millimeter-wave regime. Furthermore, these results open up many frontiers for applications not only limited to the next generation particle accelerators but also x-ray generation, probing material dynamics, and nonlinear light-matter interactions at mm-wave frequency.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

K S 0 K S 0 and K S 0 K± femtoscopy in pp collisions at s = 5.02 and 13 TeV

The ALICE collaboration has studied neutral kaon pair correlations and neutral kaon - charged kaon correlations generated from 5.02, 7 and 13 TeV proton-proton collisions produced by the CERN Large Hadron Collider. From analyzing this data, we have show a strong suggestion that the a 0 (980) particle generated in these collisions, which decays into these kaon pairs, is a four-quark particle, instead of the usual two and three-quark particles which are normally seen.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Diagnostic Methodologies of Laser-Initiated 11 B(p,α)2α Fusion Reactions

The detection of the ionic products of low-rate fusion reactions, and in particular of the 11 B(p,α)2α, is one of the recognized main problems in experiments where these reactions are initiated by tailored interaction of intense and high-energy lasers with matter. A thorough description of this important issue, with a critical comparison of the diagnostic opportunities, is indeed so far. In this work, we describe the common diagnostic methodologies used for the detection of the alpha particles generated by the 11 B(p,α)2α reaction and, for each, we outline advantages and limitations, with considerations that can also be applied to other low-rate fusion reactions. We show here that, in general, the univocal characterization of the α products coming from this reaction can be achieved by the simultaneous use of several diagnostic tools placed in close proximity.

11B(p,α)2α reactions↗
DOE OSTI2025

Acute Exposure to Aerosolized Nanoplastics Modulates Redox-Linked Immune Responses in Human Airway Epithelium

Micro- and nanoplastics (MPs and NPs) are pervasive environmental pollutants detected in aquatic ecosystems, with emerging evidence suggesting their presence in airborne particles generated by water body motion. Inhalation exposure to airborne MPs and NPs remains understudied despite documented links between occupational exposure to these particles and adverse respiratory outcomes, including airway inflammation, oxidative stress, and chronic respiratory diseases. This study explored the effects of acute NP exposure on a fully differentiated 3D human airway epithelial model derived from 14 healthy donors. Airway epithelium was exposed to aerosolized 50 nm polystyrene NPs at concentrations ranging from 2.5 to 2500 µg/mL for three minutes per day over three days. Functional assays revealed no significant alterations in tissue integrity, cell survival, mucociliary clearance, or cilia beat frequency, suggesting intact epithelial function post-exposure. However, cytokine and chemokine profiling identified a significant five-fold increase in CCL3 (MIP-1α), a neutrophilic chemoattractant, in NP-exposed samples compared to controls. This was corroborated by increased neutrophil chemotaxis in response to conditioned media from NP-exposed tissues, indicating a pro-inflammatory neutrophilic response. Conversely, levels of interleukins (IL-21, IL-2, IL-15), CXCL10, and TGF-β were significantly reduced, suggesting immunomodulatory effects that may impair adaptive immune responses and tissue repair mechanisms. These findings demonstrate that short-term exposure to NP-containing aerosols induces a distinct pro-inflammatory response in airway epithelium, characterized by enhanced neutrophil recruitment and reduced secretion of key immune modulators. These findings underscore the potential for aerosolized NPs to induce oxidative and inflammatory stress, raising concerns about their long-term impact on respiratory health and redox regulation.

Biochemistry & Molecular Biology↗
DOE OSTI2025

All Particle In Fission Reactor - Energy Deposition

This product includes software developed by Members of the Geant4 Collaboration (http://cern.ch/geant4). The basic principle of ALFRED consists of a k-eigenvalue module in which all generated particles are tracked and all deposited energy is accounted for. An eigenvalue module updates the neutron source after each run based on the neutrons emitted at each fission in the previous run. As a result, the source distribution converges to the fundamental mode of the steady-state eigenvalue problem of the associated critical reactor. ALFRED leverages the High Precision neutron transport package.

Ferney, PaulA. [Idaho National Laboratory (INL), I↗