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NASA NTRSDate not supplied

Nuclear Fusion Space Propulsion Research, Experimentation, Theory Development, and Systems Analysis Efforts Led by the NASA Glenn Research Center (1994-2004)

This review paper summarizes work performed from 1994 to 2004 by a several interrelated government, academic, and industry teams led by the NASA Glenn Research Center. The nuclear fusion space propulsion system concept was predicated on a spherical torus reactor, which enabled manned missions to the outer planets in less than one year. Moderate thrust levels (1,000’s lbf)from direct nuclear fusion exhaust plasma via a magnetic nozzle enabled high thrust-to-weight. An entire vehicle conceptual design, including an artificial gravity crew habitat, was created by the NASA Glenn Research Center. The proof of concept experiment test article and facility upgrade was performed at the Ohio State University which also included staff from the Ohio Aerospace Institute and Science Applications International Corporation.The governing equations for the plasma physics theory of magnetic nozzle operation were derived by the Los Alamos National Laboratory. A preliminary investigation of a proof of concept test utilizing Coaxial Helicity Ejection as a means to supply plasma for propulsion at the National Spherical Torus Experiment reactor was outlined by the Princeton Plasma Physics Laboratory. An industry standard on nuclear fusion propulsion conceptual design was created by two AIAA teams. Despite extremely modest funding levels, significant progress was made advancing the state of the art.The result was a coordinated conceptual, theoretical, and experimental design effort to guide fusion space propulsion development.

Nuclear fusion↗

DOE OSTI2020

Evaluating diffusion and the thermodynamic factor for binary ionic mixtures

Molecular dynamics (MD) simulations are a powerful tool for the calculation of transport properties in mixtures. Not only are MD simulations capable of treating multicomponent systems, they are also applicable over a wide range of temperatures and densities. In plasma physics, this is particularly important for applications such as inertial confinement fusion. While many studies have focused on the effect of plasma coupling on transport properties, here we focus on the effects of mixing. We compute the thermodynamic factor, a measure of ideal/non-ideal mixing, for three binary ionic mixtures. Here, we consider mixtures of hydrogen and carbon, hydrogen and argon, and argon and carbon, each at 500 randomly generated state points in the warm dense matter and plasma regimes. The calculated thermodynamic factors indicate different mixing behavior across phase space, which can significantly affect the corresponding mutual diffusion coefficients. As MD simulations are still computationally expensive, we apply modern data science tools to predict the thermodynamic factor over a large phase space. Further, we propose a more accurate approximation to the mutual diffusion coefficient than the commonly applied Darken relation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2022

Kinetic theory of particle-in-cell simulation plasma and the ensemble averaging technique

Abstract We derive the kinetic theory of fluctuations in physically and numerically stable particle-in-cell (PIC) simulations of electrostatic plasmas. The starting point is the single-time correlation at the start of the simulation between the statistical fluctuations of the weighted densities of macroparticle centers in the plasma particle phase-space. The fluctuations are associated with different initial conditions, typically due to the random initial conditions (in velocity space) of the macroparticles/simulation plasma, assigned according to their initial distribution of probability. The single-time correlations at all time steps and in each spatial grid cell are then determined from the Laplace–Fourier transforms of the discretized Klimontovich-like equation for the macroparticles and Maxwell’s equations for the fields, as computed by modern PIC codes. We recover the expressions for the electrostatic field and the plasma particle density fluctuation autocorrelation spectra as well as the kinetic equations describing the average evolution of PIC-simulated plasma particles, first derived by Langdon (1970b Proc. 4th Conf. Numerical Simulation of Plasmas ) using a test macroparticle approach perturbing a discretized Vlasovian plasma and then averaging the obtained physical quantity over the initial macroparticle velocity distribution. We generalize and extend these results to the modern algorithms in PIC codes using arbitrary macroparticle weights. Analytical estimates of statistical fluctuation amplitudes are derived as a function of the plasma simulation parameters, using the central limit theorem in the limit of a large number of macroparticles per cell. The theory is then used to analyze the ensemble averaging technique of PIC simulations where statistical averages are performed over ensembles of PIC simulations, modeling the same plasma physics problem but using different statistical realizations of the initial distribution functions of the macroparticles. This method is illustrated by linear Landau damping uncovering (from noise, which is usually considered numerical) the physical fluctuations driven by a single small amplitude electrostatic wave perturbing a PIC simulation plasma in equilibrium.

fluctuations correlations↗

DOE OSTI2022

Hybrid-gyrokinetic simulations of low- n toroidal Alfvén eigenmodes using gKPSP

Here, we report a benchmark study of toroidal Alfvén eigenmode (TAE) simulation using the hybrid-gyrokinetic code GyroKinetic Plasma Simulation Program (gKPSP). A simulation capability for energetic particles based on the gyrokinetic δf method has been newly implemented in the gKPSP code. Benchmark simulations have been performed in both circular and realistic tokamak geometries. Good agreement has been found with previously reported results, demonstrating the new capability of the gKPSP code. We have investigated the effects of the distribution function on TAE stability by examining both isotropic and anisotropic slowing-down distributions of energetic particles. The slowing-down distribution produces a higher linear growth rate than a Maxwellian distribution, while a growth rate scan with the anisotropy shows an opposite trend. This can be attributed to competition between Landau damping and the linear drive, which are correlated with the fraction of resonant passing particles and their distribution in phase space.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2026

Autonomous Ion Mass Spectrometer Sentry (AIMSS)

Satellite measurements of plasma density and temperature help predict the intensity of geomagnetic storms, which can impact satellites, communications, and power systems. Accurate forecasting requires knowledge of plasma composition. However, typical orbital mass spectrometers have difficulty distinguishing between nitrogen (N+) and oxygen (O+) ions due to their similar masses. This limitation makes it difficult to validate modern space weather models, which depend on accurate knowledge of ion composition in near-Earth space. N+ and O+ ions behave differently in space due to differences in their origin, transport, and loss mechanisms. Improving our ability to distinguish between these ions is critical for understanding and predicting space weather.

47 OTHER INSTRUMENTATION↗

NASA NTRSDate not supplied

Inner Magnetospheric Physics

A brief overview of inner magnetospheric physics will be given. As a discipline, magnetospheric physics is a young science. Its earliest experimental beginnings were in the 1950s with the study of low frequency radio waves originating from lightning and later with the first orbiting satellite, Explorer 1. The solar wind drives the coupled magnetospheric system from the ionosphere-thermosphere, plasmasphere, ring current, radiation belts, out through the region of interface to interplanetary space, the magnetosheath and bow shock. The basic plasma systems, their motions, and responses to the driving solar wind will be mentioned. These highlights of the magnetospheric system are intended only to provide points of reference for further more in-depth study.

inner magnetosphere, physical processes↗

DOE OSTI2020

Measurement of Kinetic-Scale Current Filamentation Dynamics and Associated Magnetic Fields in Interpenetrating Plasmas

Here, we present the first local, quantitative measurements of ion current filamentation and magnetic field amplification in interpenetrating plasmas, characterizing the dynamics of the ion Weibel instability. The interaction of a pair of laser-generated, counterpropagating, collisionless, supersonic plasma flows is probed using optical Thomson scattering (TS). Analysis of the TS ion-feature revealed anticorrelated modulations in the density of the two ion streams at the spatial scale of the ion skin depth c/ω pi = 120 μm, and a correlated modulation in the plasma current. The inferred current profile implies a magnetic field amplitude ~30 ± 6 T , corresponding to ~1% of the flow kinetic energy, indicating that magnetic trapping is the dominant saturation mechanism.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2024

Formation of collisionless shocks driven by strongly magnetized relativistic electrons in the laboratory

In experiments performed with the OMEGA EP laser system, proton deflectometry captured magnetic field dynamics consistent with collisionless shock formation driven by strongly magnetized relativistic electrons. During laser-foil interactions, shocks can form as relativistic electrons and strong surface magnetic fields generated by a short-pulse laser impinge on a cooler plasma produced by a longer-pulse laser. Three-dimensional particle-in-cell simulations reproduce the magnetic draping and fast formation speeds measured in the experiment and reveal that this relativistic-electron-driven shock forms at an interface that is unstable to shear and streaming instabilities. The simulation results provide insight into the microphysics that may influence high-energy shocks observed in extreme astrophysical environments. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2026

Toward the origins of binding energy shifts and “satellites” formation during plasma-XPS measurements

In-plasma x-ray photoelectron spectroscopy (plasma-XPS) emerges as a powerful platform for real-time, in situ chemical analysis under conditions relevant to semiconductor processing and other plasma-enabled technologies. This study investigates the origins of binding energy (BE) shifts and the formation of “satellite” peaks observed during plasma-XPS measurements across conductive, dielectric, and gas-phase systems. Using a standard laboratory-based ambient pressure XPS apparatus coupled with an alternating current (AC)-driven capacitively coupled plasma source, we demonstrate that metastable surface species, such as transient Au oxides, can be detected during plasma exposure, revealing chemical states that are hardly accessible using conventional ultrahigh vacuum (UHV) XPS. In dielectric samples (e.g., undoped diamond, sapphire), we observe pressure- and plasma-type-dependent BE shifts of more than 50 eV, attributed to x-ray-induced and plasma-mediated surface charging. These shifts are mitigated at higher pressures/plasmas or in electronegative plasmas (e.g., O 2 ), the latter due to enhanced charge compensation mechanisms involving slow negative ions. For gas-phase species, AC-plasma excitation leads to spectral broadening and the emergence of “satellite” peaks with energy separations of a few electron volts, linked to oscillating local plasma potentials in the probing volume. Furthermore, these findings highlight the complex and important interplay between plasma parameters, surface charging, and local electric fields in shaping XPS spectra. Overall, plasma-XPS emerges as a critical metrological tool for probing transient surface chemistry, with implications for semiconductor processing, material synthesis, and plasma diagnostics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1973

Particle and field payloads

The capability of the Space Shuttle for the conduct of magnetospheric experiments is critically analyzed. Some physical problems are discussed on which a particle and field payload program could be based. They include the study of magnetospheric plasma processes, wave-particle interactions and auroral phenomena, both by artificial modification experiments and by systematic wide-scale observations of naturally occurring magnetospheric perturbation events.

Roederer, J. G.↗

DOE OSTI2021

The radioactive nuclei 26 Al and 60 Fe in the Cosmos and in the solar system

The cosmic evolution of the chemical elements from the Big Bang to the present time is driven by nuclear fusion reactions inside stars and stellar explosions. A cycle of matter recurrently re-processes metal-enriched stellar ejecta into the next generation of stars. The study of cosmic nucleosynthesis and this matter cycle requires the understanding of the physics of nuclear reactions, of the conditions at which the nuclear reactions are activated inside the stars and stellar explosions, of the stellar ejection mechanisms through winds and explosions, and of the transport of the ejecta towards the next cycle, from hot plasma to cold, star-forming gas. Due to the long timescales of stellar evolution, and because of the infrequent occurrence of stellar explosions, observational studies are challenging, as they have biases in time and space as well as different sensitivities related to the various astronomical methods. Here, we describe in detail the astrophysical and nuclear-physical processes involved in creating two radioactive isotopes useful in such studies, 26 Al and 60 Fe. Due to their radioactive lifetime of the order of a million years, these isotopes are suitable to characterise simultaneously the processes of nuclear fusion reactions and of interstellar transport. We describe and discuss the nuclear reactions involved in the production and destruction of 26 Al and 60 Fe, the key characteristics of the stellar sites of their nucleosynthesis and their interstellar journey after ejection from the nucleosynthesis sites. This allows us to connect the theoretical astrophysical aspects to the variety of astronomical messengers presented here, from stardust and cosmic-ray composition measurements, through observation of γ rays produced by radioactivity, to material deposited in deep-sea ocean crusts and to the inferred composition of the first solids that have formed in the Solar System. We show that considering measurements of the isotopic ratio of 26 Al to 60 Fe eliminate some of the unknowns when interpreting astronomical results, and discuss the lessons learned from these two isotopes on cosmic chemical evolution. This review paper has emerged from an ISSI-BJ Team project in 2017–2019, bringing together nuclear physicists, astronomers, and astrophysicists in this inter-disciplinary discussion.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1990

Three dimensional reconnection in astrophysical plasmas

Theoretical issues related to three-dimensional reconnection and its application to the space and astrophysical environment are reviewed. Consideration is given to the meaning of reconnection in three dimensions, the way in which periodic and nonperiodic magnetic topologies alter the physics of reconnections, and the effects of chaotic magnetic fields on the reconnection process.

Spicer, D. S.↗

DOE OSTI2021

Robust analysis of space-, time-, and energy-resolved soft x-ray measurements of magnetically confined fusion plasmas (invited)

A novel compact multi-energy soft x-ray (ME-SXR) diagnostic based on the PILATUS3 100K x-ray detector has been developed in collaboration between the Princeton Plasma Physics Laboratory and the University of Wisconsin-Madison and tested on the Madison Symmetric Torus (MST) reversed-field pinch. This solid-state photon-counting detector consists of a two-dimensional array of ~100 000 pixels for which the lower photon absorption cutoff energy can be independently set, allowing it to be configured for a unique combination of simultaneous spatial, spectral, and temporal resolution of ~1 cm, 100 eV, and 500 Hz, respectively. The diagnostic is highly versatile and can be readily adapted to diverse plasma operating conditions and scientific needs without any required downtime. New results from improved-confinement and quasi-single helicity plasmas in the MST demonstrate how the detector can be applied to study multiple aspects of the evolution of magnetically confined fusion-grade plasmas. These include observing the evolution of thermal emissivity, characterizing the energy of mid-Z excitation lines, extracting the T e profile, and observing the evolution of non-thermal populations. A technique for integrating the ME-SXR diagnostic into an integrated data analysis framework based on Bayesian inference is also presented. As a result, this allows ME-SXR measurements to be combined with data for complementary diagnostics in order to simultaneously infer Te and nZ from all available information.

47 OTHER INSTRUMENTATION↗

NASA NTRS1977

X-ray emission from high temperature plasmas

The physical processes occurring in plasma focus devices were investigated with particular emphasis on X-ray emission. Topics discussed include: trajectories of high energy electrons; detection of ion trajectories; spatial distribution of neutron emission; space and time resolved emission of hard X-rays from a plasma focus; the staged plasma focus as a variation of the hypocloidal pinch; formation of current sheets in a staged plasma focus; and X-ray and neutron emission from a staged plasma focus. The possibility of operating dense plasma-focus type devices in multiple arrays beyond the scaling law for a single gun is discussed.

Harries, W. L.↗

NASA NTRS1980

The application of artificial electron beams to magnetospheric research

Scientific and technical progress made in the utilization of electron beams injected from large sounding rockets for the investigation of magnetospheric structure and dynamics and plasma physics is reviewed. Consideration is given to the problem of vehicle neutralization during the generation of electron beams in the ionosphere and the stability and electromagnetic wave emissions of electron beams propagating in space. Optical effects observed during the two Hess artificial aurora experiments, the Minnesota Echo IV and V experiments, the Zarnitsa-1 artificial aurora experiment and the Precede-Excede experiments are discussed, together with atmospheric scattering effects observed during Echo I, II and III, and results of the three experimental programs which have detected and analyzed beams after passage through the distant magnetosphere (the second Hess experiment, ARAKS and the Electron Echo experiments) are presented. Finally, plans for future research are outlined, and a chronology and complete bibliography of the programs conducted to date are included.

Winckler, J. R.↗

NASA NTRS1990

Ultra-low-frequency magnetic pulsations in the earth's magnetosphere

Spacecraft observations have shown that geomagnetic pulsations originating in magnetospheric processes, in spite of their small amplitude on the ground, have amplitudes in space relative to the local magnetic field of 5-10 percent and occasionally up to about 50 percent. It is noted that by studying geomagnetic pulsations, a detailed comparison can be made between plasma physics theory and observations that are not possible in laboratory experiments. Also geomagnetic pulsations play a role in magnetospheric dynamics and energy transport, and their study forms an integral part of enhancing the knowledge of the magnetosphere. The importance of spacecraft observations are discussed and attention is given to such topics as waves in the magnetosphere, field-line resonances, the quantitative analysis of a dipole field, plasma instabilities, and energy flow.

Anderson, Brian J.↗

NASA NTRS2018

Current Activities in the Advanced Exploration Systems ISRU Project

Media Filter MOXIE support: completed flow performance tests and initial dust loading tests of the MOXIE HEPA filter in the Mars Flow Loop Designed and fabricated prototype full-scale scroll filter for testing of renewable filter performance Mars Flow Loop upgrades: installed more sensitive instrumentation, improved imaging, and increased run duration capability Electrostatic Precipitator (ESP) Plasma-physics based model predicts particle charge and trajectory Characterizing dust environment from fluidized-bed injection dust environment using laser sheet visualization and Fine Particle Analyzer Sabatier Design Study Defined the Sabatier design space, including reactor type, thermal management, gas recycling/separation Modeled Sabatier systems with one or two reactors with different types of thermal management Adding thermal management schemes and recycling and gas separation to model Catalyst Screening Performing compression testing on new and used catalyst pellets Performing vibration testing on different catalyst pellet types under different load conditions Preparing to test catalysts for performance and degradation

In-Situ Resource Utilization↗

NASA NTRS2020

The Role of Solar Wind Hydrogen in Space Weathering: Insights from Laboratory-Irradiated Northwest Africa 12008

Micrometeoroid impacts, solar wind plasma interactions, and regolith gardening drive the complicated and nuanced mechanism of space weathering (or optical maturation); a process by which a material’s optical properties are changed as a result of chemical and physical alterations at the surface of grains on airless bodies. Reddened slopes, attenuated absorption bands, and an overall reduction in albedo in the visible and near-IR wavelength ranges are primarily the result of native iron nanoparticle (npFe0) production within glassy rims that form from sputtering and vaporization. The sizes and abundance of these particles provide information about the relative surface exposure age of a particular grain. In addition, many studies have indicated that composition greatly affects the rate at which optical maturation occurs. Despite our understanding of how npFe0 affects optical signatures, the relative roles of micrometeoroid bombardment and solar wind interactions remains undetermined. To simulate the early effects of weathering by the solar wind and to determine thresholds for optical change with respect to a given mineral phase, we irradiated a fine-grained lunar basalt with 1 keV H+ to a fluence of 6.4 x 1016 H+ per sq.cm. Surface alterations within four phases have been evaluated using transmission electron microscopy (TEM). We found that for a given fluence of H+, the extent of damage acquired by each grain was dependent on its composition. No npFe(0) was produced in any of the phases evaluated in this study. These results are consistent with many previous studies conducted using ions of similar energy, but they also provide valuable information about the onset of space weathering and the role of the solar wind during the early stages of optical maturation.

Shusterman, M. L.↗