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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

A drift kinetic model for the expander region of a magnetic mirror

Here, we present a drift kinetic model for the free expansion of a thermal plasma out of a magnetic nozzle. This problem relates to plasma space propulsion systems, natural environments such as the solar wind, and end losses from the expander region of mirror magnetically confined fusion concepts such as the gas dynamic trap. The model incorporates trapped and passing orbit types encountered in the mirror expander geometry and maps to an upstream thermal distribution. This boundary condition and quasineutrality require the generation of an ambipolar potential drop of ~5T e /e, forming a thermal barrier for the electrons. The model for the electron and ion velocity distributions and fluid moments is confirmed with data from a fully kinetic simulation. Finally, the model is extended to account for a population of fast sloshing ions arising from neutral beam heating within a magnetic mirror, again resulting in good agreement with a corresponding kinetic simulation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1974

Preliminary Pioneer 10 encounter results from the Ames Research Center plasma analyzer experiment

Preliminary results from the Ames Research Center plasma analyzer experiment for the Pioneer 10 Jupiter encounter indicate that Jupiter has a detached bow shock and magnetopause similar to the case at Earth but much larger in spatial extent. In contrast to Earth, Jupiter's outer magnetosphere appears to be highly inflated by thermal plasma and therefore highly responsive in size to changes in solar wind dynamic pressure.

Wolfe, J. H.↗
NASA NTRS1982

Conical pitch angle distributions of very low-energy ion fluxes observed by ISEE 1

Observations are presented of conical distributions of low-energy ion fluxes from throughout the magnetosphere. The data were provided by the plasma composition experiment (PCE) on ISEE 1. ISEE 1 was launched in October 1977 into a highly elliptical orbit with a 30 deg inclination to the equator and 22.5 earth radii apogee. Particular attention is given to data taken when the instrument was in its thermal plasma mode, sampling ions in the energy per charge range 0-100 eV/e. Attention is given to examples of conical distributions in 0- to 100-eV/e ions, the occurrence of conical distributions of 0- to 100-eV ions in local time-geocentric distance and latitude-geocentric distance coordinates, the cone angles in 0- to 100-eV ion conics, Kp distributions of 0- to 100-eV ion conics, and some compositional aspects of 0- to 100-eV ion conics.

Horwitz, J. L.↗
NASA NTRS1986

Plasma and field observations of a Pc 5 wave event

The particle detector and electric field data collected by the Dynamo Explorer 1 on the Pc 5 wave event encounter on July 14, 1982 are presented, yielding a nearly complete picture of the event. The overall structure of the Pc 5 seems to order the event into two distinct halves, suggesting a temporal or spatial variation of the micropulsation. Thermal plasma measurements showed that the dominant ion throughout both lobes was H(+). Significant quantities of He(+), O(+), N(+), and O(2+) were also observed to be present and rotating together in a plane normal to the magnetic field direction, due to the Pc5 E x B drift. The plasma parameters determined for the two lobes were used in theoretical calculations to predict the period of the observed resonance.

Waite, J. H.↗
DOE OSTI2023

Spheroidization of Nd–Fe–B particles

Spherical powders are required for many advanced manufacturing techniques due to their inherent requirement of flowability, either within feed tubes or during powder spreading. As advanced manufacturing of magnets continues to develop, new production methods for feedstocks are also sought. Plasma spheroidization is a high-yield method to produce spherical Nd–Fe–B powders from irregularly shaped particles, with advantages including high throughput and a well-controlled size distribution. Highly spherical Nd–Fe–B powders with large scale production (i.e., kg) have been demonstrated using an inductively coupled thermal plasma system; however, the magnetic properties of the output powder display significant degradation. The coercivity was decreased from the initial 8 kOe (636 kA/m) of the as-received to 0.7 kOe (55 kA/m) for spheroidized powders. Microstructural investigation reveals 6% Nd depletion caused by the extreme temperatures of the plasma, leading to the formation of low-coercivity α-Fe and a subsequent decrease in energy product. In conclusion, post-spheroidization heat treatments with Nd can partially mitigate the coercivity degradation, increasing to 1.7 kOe (135 kA/m), potentially offering a pathway toward spherical powders for a range of applications.

36 MATERIALS SCIENCE↗
NASA NTRS1988

On the need for space tests of plasma contactors as electron collectors

An analysis is presented of laboratory experiments that have shown that hollow plasma sources can provide low-impedance contact with a background plasma. In particular, some experiments show an report an 'ignited mode' of electron collection using plasma sources where almost an ampere was collected at a potential of 100 volts. The experimental results are compared with theoretical and computational models of plasma layers. Preliminary results indicate that the measured potential profiles and collected currents during the 'ignited mode' correspond to an increase in the background plasma thermal current of more than an order of magnitude. The results imply that the 'ignited mode' results are substantially impacted by the laboratory electron source and the tank size. Only experiments performed in space will be able to provide the correct boundary conditions for reliably testing high electron collection by plasma contactors.

Katz, Ira↗
NASA NTRS1986

Medium-energy electrons and heavy ions in Jupiter's magnetosphere - Effects of lower hybrid wave-particle interactions

A theory of medium-energy (about keV) electrons and heavy ions in Jupiter's magnetosphere is presented. Lower hybrid waves are generated by the combined effects of a ring instability of neutral wind pickup ions and the modified two-stream instability associated with transport of cool Iogenic plasma. The quasi-linear energy diffusion coefficient for lower hybrid wave-particle interactions is evaluated, and several solutions to the diffusion equation are given. Calculations based on measured wave properties show that the noise substantially modifies the particle distribution functions. The effects are to accelerate superthermal ions and electrons to keV energies and to thermalize the pickup ions on time scales comparable to the particle residence time. The S(2+)/S(+) ratio at medium energies is a measure of the relative contribution from Iogenic thermal plasma and neutral wind ions, and this important quantity should be determined from future measurements. The theory also predicts a preferential acceleration of heavy ions with an accleration time that scales inversely with the root of the ion mass. Electrons accelerated by the process contribute to further reionization of the neutral wind by electron impact, thus providing a possible confirmation of Alfven's critical velocity effect in the Jovian magnetosphere.

Barbosa, D. D.↗
NASA NTRS2006

2-D Drift Velocities from the IMAGE EUV Plasmaspheric Imager

The IMAGE Mission extreme ultraviolet imager (EW) observes He(+) plasmaspheric ions throughout the inner magnetosphere. Limited by ionizing radiation and viewing close to the Sun, images of the He(+) distribution are available every 10 minutes for many hours as the spacecraft passes through apogee in its highly elliptical orbit. As a consistent constituent at about 15%, He(+) is an excellent surrogate for monitoring all of the processes that control the dynamics of plasmaspheric plasma. In particular, the motion of He' transverse to the ambient magnetic field is a direct indication of convective electric fields. The analysis of boundary motions has already achieved new insights into the electrodynamic coupling processes taking place between energetic magnetospheric plasmas and the ionosphere. Yet to be fulfilled, however, is the original promise that global E W images of the plasmasphere might yield two-dimensional pictures of mesoscale to macro-scale electric fields in the inner magnetosphere. This work details the technique and initial application of an IMAGE EUV analysis that appears capable of following thermal plasma motion on a global basis.

Gallagher, D. L.↗
NASA NTRS2007

2-D Drift Velocities from the IMAGE EUV Plasmaspheric Imager

The IMAGE Mission extreme ultraviolet imager (EUY) observes He+ plasmaspheric ions throughout the inner magnetosphere. Limited by ionizing radiation and viewing close to the Sun, images of the He+ distribution are available every 10 minutes for many hours as the spacecraft passes through apogee in its highly elliptical orbit. As a consistent constituent at about 15%, He+ is an excellent surrogate for monitoring all of the processes that control the dynamics of plasmaspheric plasma. In particular, the motion ofHe+ transverse to the ambient magnetic field is a direct indication of convective electric fields. The analysis of boundary motions has already achieved new insights into the electrodynamic coupling processes taking place between energetic magnetospheric plasmas and the ionosphere. Yet to be fulfilled, however, is the original promise that global EUY images of the plasmasphere might yield two-dimensional pictures of meso-scale to macro-scale electric fields in the inner magnetosphere. This work details the technique and initial application of an IMAGE EUY analysis that appears capable of following thermal plasma motion on a global basis.

Gallagher, D.↗
NASA NTRS1974

A multi-satellite study of the nature of wavelike structures in the magnetospheric plasma

An intercomparison is made of the wavelike structures in the data from the light ion mass spectrometer and the fluxgate magnetometer on OGO 5. The wavelike structures appear simultaneously in the data from both experiments. The waves contain both transverse and compressional modes and exhibit periods of 100 to 200 seconds. The waves are usually observed outside the plasmapause and are located primarily on the dayside of the magnetosphere. One possible cause of the apparent density fluctuation is a velocity modulation of the thermal plasma which causes the particles to drift into and out of the ion spectrometer.

Shelley, E. G.↗
NASA NTRS2011

Entropy Generation Across Earth's Bow Shock

Earth's bow shock is a transition layer that causes an irreversible change in the state of plasma that is stationary in time. Theories predict entropy increases across the bow shock but entropy has never been directly measured. Cluster and Double Star plasma experiments measure 3D plasma distributions upstream and downstream of the bow shock that allow calculation of Boltzmann's entropy function H and his famous H-theorem, dH/dt ~ O. We present the first direct measurements of entropy density changes across Earth's bow shock. We will show that this entropy generation may be part of the processes that produce the non-thermal plasma distributions is consistent with a kinetic entropy flux model derived from the collisionless Boltzmann equation, giving strong support that solar wind's total entropy across the bow shock remains unchanged. As far as we know, our results are not explained by any existing shock models and should be of interests to theorists.

Parks, George K.↗
NASA NTRS1978

Plasmapause signatures in the ionosphere and magnetosphere

Isis 2 observations of a variety of topside ionospheric 'signatures' of the plasmapause are compared with simultaneously acquired equatorial electron-density profiles obtained by the whistler technique. The satellite data were acquired at about 1400-km altitude at dusk and dawn in the sunlit Northern Hemisphere summer ionosphere within about 15 deg longitude of the VLF receiver. Results suggest that the dynamics of plasma coupling between the ionosphere and plasmasphere dominate the topside data and obscure the location of the equatorial plasmapause field line. The total density and light-ion troughs begin 2 to 10 deg equatorward of the field line through the equatorial plasmapause and are not clear plasmapause signatures. The invariant latitude of the region of steep spatial gradient in thermal plasma density, the plasmapause, appears to increase with altitude. Thus measurements of its position at different altitudes may give different results. Plasma-sheet electrons, however, are observed on field lines just outside the equatorial plasmapause at both dawn and dusk. Their low-latitude extent at 1400-km altitude can be used as a signature of the equatorial plasmapause position.

Foster, J. C.↗
DOE OSTI2020

Atmospheric Pressure Plasma Deposition of TiO2: A Review

Atmospheric pressure plasma (APP) deposition techniques are useful today because of their simplicity and their time and cost savings, particularly for growth of oxide films. Among the oxide materials, titanium dioxide (TiO2) has a wide range of applications in electronics, solar cells, and photocatalysis, which has made it an extremely popular research topic for decades. Here, we provide an overview of non-thermal APP deposition techniques for TiO2 thin film, some historical background, and some very recent findings and developments. First, we define non-thermal plasma, and then we describe the advantages of APP deposition. In addition, we explain the importance of TiO2 and then describe briefly the three deposition techniques used to date. We also compare the structural, electronic, and optical properties of TiO2 films deposited by different APP methods. Lastly, we examine the status of current research related to the effects of such deposition parameters as plasma power, feed gas, bias voltage, gas flow rate, and substrate temperature on the deposition rate, crystal phase, and other film properties. The examples given cover the most common APP deposition techniques for TiO2 growth to understand their advantages for specific applications. In addition, we discuss the important challenges that APP deposition is facing in this rapidly growing field.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1997

The Diagnostics of the External Plasma for the Plasma Rocket

The plasma rocket is located at NASA Johnson Space Center. To produce a thrust in space. an inert gas is ionized into a plasma and heated in the linear section of a tokamak fusion device to 1 x 10(exp 4) - 1.16 x 10(exp 6)K(p= 10(exp 10) - 10(exp 14)/cu cm ). The magnetic field used to contain the plasma has a magnitude of 2 - 10k Gauss. The plasma plume has a variable thrust and specific impulse. A high temperature retarding potential analyzer (RPA) is being developed to characterize the plasma in the plume and at the edge of the magnetically contained plasma. The RPA measures the energy and density of ions or electrons entering into its solid angle of collection. An oscilloscope displays the ion flux versus the collected current. All measurements are made relative to the facility ground. A RPA is being developed in a process which involves the investigation of several prototypes. The first prototype has been tested on a thermal plasma. The knowledge gained from its development and testing were applied to the development of a RPA for collimated plasma. The prototypes consist of four equally spaced grids and an ion collector. The outermost grid is a ground. The second grid acts as a bias to repel electrons. The third is a variable v voltage ion suppressor. Grid four (inner grid) acts to repel secondary electrons, being biased equal to the first. Knowledge gained during these two stages are being applied to the development of a high temperature RPA Testing of this device involves the determination of its output parameters. sensitivity, and responses to a wide range of energies and densities. Each grid will be tested individually by changing only its voltage and observing the output from the RPA. To verify that the RPA is providing proper output. it is compared to the output from a Langmuir or Faraday probe.

Karr, Gerald R.↗
NASA NTRS1984

Mechanical property measurements of plasma-sprayed thermal-barrier coatings subjected to oxidation

Techniques have been developed for measuring the tensile properties of plasma-sprayed coatings which are used in thermal barrier applications. The measurements have included the average Young's modulus, bond strength and elongation at failure. The oxidation behavior of the bond coat plays an important role in the integrity and adhesion of plasma-sprayed thermal barrier coatings. This work studies the nature of the high temperature degradation on the mechanical properties of the coating. Furnace tests have been carried out on U-700 alloy with bond coats of NiCrAlY or NiCrAlZr and an overlay of ZrO2-8 percent Y2O3. Weight gain measurements on the coatings have been examined with relation to the adhesion strength and failure observations. The results from an initial study are reported in this work.

Berndt, C. C.↗
NASA NTRS1989

Plasma wave observations during electron beam experiments at high altitudes

Electron beam experiments on the nearly geosynchronous P78-2 satellite conducted in 1979 resulted in observations of intense radiation near the local electron gyrofrequency. These signals resembled naturally occurring f(ce) waves during the same period. The amplitude of the simulated waves depended upon beam parameters. During 50-eV beam operations, current levels of 10 microamps produced strong emissions. Current levels of 1 microamp and 100 microamps did not. These emissions correspond in time to previously reported observations of electron distributions, which suggest heating of the local thermal plasma. Sufficient power is in the observed emissions to explain some aspects of the heated electron distributions observed during the experiments.

Olsen, R. C.↗
DOE OSTI2022

Validation of energetic particle transport models for time-dependent integrated simulations of burning plasmas (Final ST Report)

The major goal of this project is to deliver a suite of validated energetic particle (EP) modeling tools for time-dependent integrated tokamak simulations (with the code TRANSP) that can be used for modeling plasma discharges featuring a substantial EP content, such as burning plasmas. During FY20, issues were resolved with an energetic particle transport model called TGLF-EP, with improvements made to the TGLF-EP workflow, generation of input files, and interpretation of runs on the NERSC supercomputing cluster. The recipient also gave input on simulations with the code TRANSP to reproduce the reference JET discharge, and assessed the accuracy and uncertainties of the simulated B field, current evolution, thermal plasma profiles, stored energy, etc. Input was also given on interpretation of fast-ion instability calculations and recommendations for modifications to JET afterglow discharge for the upcoming DT campaign.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Acceleration of the particle-in-cell code Osiris with graphics processing units

Fully relativistic particle-in-cell (PIC) simulations are crucial for advancing our knowledge of plasma physics. Modern supercomputers based on graphics processing units (GPUs) offer the potential to perform PIC simulations of unprecedented scale, but require robust and feature-rich codes that can fully leverage their computational resources. In this work, this demand is addressed by adding GPU acceleration to the PIC code Osiris. An overview of the algorithm, which features a CUDA extension to the underlying Fortran architecture, is given. Detailed performance benchmarks for thermal plasmas are presented, which demonstrate excellent weak scaling on NERSC's Perlmutter supercomputer and high levels of absolute performance. The robustness of the code to model a variety of physical systems is demonstrated via simulations of Weibel filamentation and laser-wakefield acceleration run with dynamic load balancing. Finally, measurements and analysis of energy consumption are provided that indicate that the GPU algorithm is up to ~14 times faster and ~7 times more energy efficient than the optimized CPU algorithm on a node-to-node basis. The described development addresses the PIC simulation community's computational demands both by contributing a robust and performant GPU-accelerated PIC code and by providing insight into efficient use of GPU hardware.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗