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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Effects of ion demagnetization in the plasma sheet

The processes in the plasma sheet in the earth's magnetotail that can generate the field-aligned currents associated with auroral arcs are investigated using a two-and-a-half-dimensional nonradiative electromagnetic particle code in the Darwin approximation. All three components of the magnetic field, as well as the effect of electrostatic interaction, are calculated. The results include the response of the plasma sheet to the application of a convection electric field, the heating of plasma sheet ions, and the generation of y-directed magnetic fields and currents in the plane of simulation. The relation of these results to other morphological features of auroral/magnetospheric substorms is discussed.

Swift, Daniel W.↗
DOE OSTI2022

Studies of EC pre-ionization in DIII-D to support development of ITER plasma initiation

New experiments have been conducted at DIII-D to improve the physics understanding of plasma initiation assisted by electron cyclotron (EC) wave injection, allowing better extrapolation to ITER. This has been achieved by applying an EC pulse prior to start of the inductive plasma initiation (i.e. the generation of a loop voltage). A pre-plasma was formed during the EC pulse that was characterized in terms of the maximum density and temperature. Parametric scans were performed to study the influence of the EC injected power, EC injection angle, and pre-fill gas pressure on the pre-plasma creation process. These experiments showed that pre-ionized plasma of good quality can have a significant effect on the subsequent V loop induced plasma initiation process, i.e. a high density pre-plasma, increases the plasma current rise and speed at which ionization is achieved when the V loop is applied. Here, a good quality pre-plasma is one that achieved a significant degree of ionization, mainly obtained by providing sufficient ECH power in DIII-D of the order of 1 MW. It was found that a minimum EC power of 0.5 MW was required in DIII-D to create ionization, and this would scale to a minimum power of roughly 6.5 MW for ITER.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2018

Collisionless Relaxation of the Ion Ring Distribution in Space Plasma

Energetic processes often produce transversely-heated angular distributions of the magnetized core (lowest energy) plasma. This characteristic is found in solar wind ion pickup, resulting from cometary or interstellar gas ionization, in Earths' ionosphere, and with hot ions formed around the Space Transportation System during gas releases. We investigate the thermalization of O+ ion pickup using the 2.5D hybrid simulation method (with fluid electrons and kinetic ions) of the ion pickup (ring) distributions, formed in the auroral ionosphere, with a range of ring velocities and thermal to magnetic pressure ratios. We find that in the unstable collisonless regime the anisotropy of the non-thermal distribution produces the ion-cyclotron instability, and the nonlinear relaxation is accompanied by wave-particle scattering that results in an emitted power of EMIC waves. We conclude that ionospheric pickup thermalization is slow due to the small ring speed compared to the thermal and Alfven speeds, while in the solar wind and other space plasmas regions with larger ion-ring velocity the collisionless relaxation and thermalization is rapid in terms of O+ ion gyro-period.

Ofman, Leon↗
NASA NTRS2011

Space Environmental Erosion of Polar Icy Regolith

While regions at the floors of permanently shadowed polar craters are isolated from direct sunlight, these regions are still exposed to the harsh space environment, including the interplanetary Lyman-a background, meteoric impacts, and obstacle-affected solar wind. We demonstrate that each of these processes can act to erode the polar icy regolith located at or near the surface along the crater floor. The Lyman-a background can remove/erode the icy-regolith via photon stimulated desorption [1], meteoric impacts can vaporize the regolith [2], and redirected solar wind ions can sputter the ice-regolith mix [3]. As an example we shall examine in detail the inflow of solar wind ions and electrons into polar craters, One might expect such ions to flow horizontally over the crater top (see Figure). However, we find that plasma ambipolar processes act to deflect passing ions into the craters [3]. We examine this plasma process and determine the ion flux as a function of position across a notional crater floor. We demonstrate that inflowing solar wind ions can indeed create sputtering along the crater floor, effectively eroding the surface. Erosion time scales rrom sputtering will be presented. We shall also consider the effect of impact vaporization on buried icy-regolith regions. There will also be a discussion of solar wind electrons that enter into the PSR, demonstrating that these also have the ability rree surface-bound atoms via electron stimulated desorption processes [l].

Farrell, William M.↗
NASA NTRS1984

Correlations between plasma variables and the deposition process of Si films from chlorosilanes in low pressure RF plasma of argon and hydrogen

The dissociation of chlorosilanes to silicon and its deposition on a solid substrate in a RF plasma of mixtures of argon and hydrogen were investigated as a function of the macrovariables of the plasma. The dissociation mechanism of chlorosilanes and HCl as well as the formation of Si in the plasma state were studied by sampling the plasma with a quadrupole mass spectrometer. Macrovariables such as pressure, net RF power input and locations in the plasma reactor strongly influence the kinetics of dissociation. The deposition process of microcrystalline silicon films and its chlorine contamination were correlated to the dissociation mechanism of chlorosilanes and HCl.

Avni, R.↗
DOE OSTI2024

Open-air plasma-assisted deposition of organosilicon coating for corrosion protection of AZ91D Mg alloy

As a corrosion barrier layer, open-air plasma-assisted organosilicon coating was applied on AZ91D Mg alloy. Organosilicon-coated AZ91D samples, prepared from two different plasma coating processes, were used for corrosion evaluation based on multistep electrochemical and H 2 collection measurements in 3.5 wt% sodium chloride (NaCl) solution. Some coated AZ91D samples were characterized with and without corrosion exposure in NaCl solution using electron microscopies and X-ray chemical analysis techniques. Further, the results indicate that the organosilicon coatings from open-air plasma processes are effective to delay the initiation of corrosion attack and also reduce the corrosion rate for AZ91D substrate. The corrosion attack was considered to develop after permeation of NaCl solution through the coating layer.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Similarity properties in capacitive radio frequency plasmas with nonlinear collision processes

Abstract Similarity laws (SL) are essential for correlating the characteristics of plasmas at different dimensional scales, which have been validated for radio frequency (rf) discharges at low pressure but under limited conditions. In this work, we evaluate the effects of nonlinear collisions (e.g. stepwise ionization) on the similarity properties in capacitive rf discharges in argon across a wide range of pressure regimes via fully kinetic particle-in-cell simulations. The SL scalings of fundamental discharge parameters, e.g. the electron power absorption and electron energy probability function, are examined with and without nonlinear collisions, respectively. Without the nonlinear collisions, the similarity scalings are found to be rigorously valid. When the nonlinear collisions are considered, the similarity properties in rf discharges still exist approximately, which indicates that the violations caused by the nonlinear collisions are still minor in the studied cases. The reasons for the effectiveness of SL scalings with nonlinear collision processes are also discussed. The results from this study confirmed the validity of similarity transformations with more complex reaction kinetics, which may promote the applicability of the SL scalings for the design and fabrications of plasma devices.

Physics↗
NASA NTRS2007

Development of Numerical Tools for the Investigation of Plasma Detachment from Magnetic Nozzles

A multidimensional numerical simulation framework aimed at investigating the process of plasma detachment from a magnetic nozzle is introduced. An existing numerical code based on a magnetohydrodynamic formulation of the plasma flow equations that accounts for various dispersive and dissipative processes in plasmas was significantly enhanced to allow for the modeling of axisymmetric domains containing three.dimensiunai momentum and magnetic flux vectors. A separate magnetostatic solver was used to simulate the applied magnetic field topologies found in various nozzle experiments. Numerical results from a magnetic diffusion test problem in which all three components of the magnetic field were present exhibit excellent quantitative agreement with the analytical solution, and the lack of numerical instabilities due to fluctuations in the value of del(raised dot)B indicate that the conservative MHD framework with dissipative effects is well-suited for multi-dimensional analysis of magnetic nozzles. Further studies will focus on modeling literature experiments both for the purpose of code validation and to extract physical insight regarding the mechanisms driving detachment.

Sankaran, Kamesh↗
DOE OSTI2022

The 2022 Plasma Roadmap: low temperature plasma science and technology

Abstract The 2022 Roadmap is the next update in the series of Plasma Roadmaps published by Journal of Physics D with the intent to identify important outstanding challenges in the field of low-temperature plasma (LTP) physics and technology. The format of the Roadmap is the same as the previous Roadmaps representing the visions of 41 leading experts representing 21 countries and five continents in the various sub-fields of LTP science and technology. In recognition of the evolution in the field, several new topics have been introduced or given more prominence. These new topics and emphasis highlight increased interests in plasma-enabled additive manufacturing, soft materials, electrification of chemical conversions, plasma propulsion, extreme plasma regimes, plasmas in hypersonics, data-driven plasma science and technology and the contribution of LTP to combat COVID-19. In the last few decades, LTP science and technology has made a tremendously positive impact on our society. It is our hope that this roadmap will help continue this excellent track record over the next 5–10 years.

plasma diagnostics↗
DOE OSTI2022

Simulation of Liquid Lithium Divertor Geometry Using SOLPS-ITER

Here, plasma-facing component (PFC) geometries are evaluated for a Fusion Nuclear Science Facility (FNSF) design to find solutions that are compatible with flowing liquid lithium components while satisfying requirements from the perspective of plasma and neutral particle transport. Flowing liquid metal (LM) divertor systems offer important advantages due to continual regeneration of the surface material, but may require modifications from standard optimized tokamak divertor designs. Scrape Off Layer Plasma Simulator for the International Thermonuclear Experimental Reactor (SOLPS-ITER) simulations are used to compare standard vertical target, open, and balanced baffled geometries. It is found that the open geometry offers little control of neutral particles and has narrow operating windows where the divertor fluxes can be lowered to acceptable levels, while maintaining the required upstream density. The addition of neutral baffles allows greater control over the divertor conditions with less impact on the upstream density. The divertor neutral pressure in the baffled geometry is slightly higher than the open divertor, but not as large with a vertical target. A first-pass coupling of the SOLPS solution with sheath and implantation/erosion models to compute the lithium emission shows that the lithium is largely confined to the near-surface region due to the small ionization mean free path and large main ion flow toward the surface. The lithium source was varied by three orders of magnitude. At the highest rate, when the sourced lithium approaches the level of the main ion recycling flux, a high core lithium concentration (~10%) is observed with only moderate power dissipation to affect the divertor plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2010

Effect of a Second, Parallel Capacitor on the Performance of a Pulse Inductive Plasma Thruster

Pulsed inductive plasma accelerators are electrodeless space propulsion devices where a capacitor is charged to an initial voltage and is then discharged through an inductive coil that couples energy into the propellant, ionizing and accelerating it to produce thrust. A model that employs a set of circuit equations (as illustrated in Fig. 1a) coupled to a one-dimensional momentum equation has been previously used by Lovberg and Dailey [1] and Polzin et al. [2-4] to model the plasma acceleration process in pulsed inductive thrusters. In this paper an extra capacitor, inductor, and resistor are added to the system in the manner illustrated in the schematic shown in Fig. 1b. If the second capacitor has a smaller value than the initially charged capacitor, it can serve to increase the current rise rate through the inductive coil. Increasing the current rise rate should serve to better ionize the propellant. The equation of motion is solved to find the effect of an increased current rise rate on the acceleration process. We examine the tradeoffs between enhancing the breakdown process (increasing current rise rate) and altering the plasma acceleration process. These results provide insight into the performance of modified circuits in an inductive thruster, revealing how this design permutation can affect an inductive thruster's performance.

Polzin, Kurt A.↗
DOE OSTI2025

Electron–positron pair annihilation in kinetic plasma

The process of electron–positron pair annihilation, driven by strong fields (inverse Schwinger mechanism) and high-frequency waves, is studied using the Dirac–Heisenberg–Wigner formalism. In an electron–positron plasma, the presence of a strong field leads to both pair creation and annihilation. Depending on plasma properties such as non-degeneracy and the momentum distribution, pair annihilation can dominate over pair creation. The energy released from annihilated pairs can lead to an enhancement of the field energy, provided that the plasma effectively blocks the creation of new pairs. Additionally, pair annihilation induced by high-frequency waves is shown to occur when the photon energy matches the energy of the pairs in the plasma.

Al-Naseri, Haidar [SLAC National Accelerator Labor↗
NASA NTRS2008

Impact of Universal Plasma and Energetic Particle Processes on Icy Bodies of the Kuiper Belt and the Oort Cloud

Modeling of space plasma and energetic particle interactions with icy bodies of the outer solar system is simplified when there is commonality of the underlying source, acceleration, and transport processes in spatially distinct regions from the supersonic heliosphere through the heliosheath into the local interstellar medium (LISM). Current trends in the Voyager heliosheath measurements suggest strong commonality to processes in the LISM. The Fisk-Gloeckler "universal" spectrum at suprathermal energies apparently plays a strong role in coupling the plasma and high energy particle regimes in the spatial and energetic transitions from the outer heliosphere to the LISM. Dominant processes in consecutive energy regimes project to varying effects versus irradiation depth on exposed upper surfaces of airless small icy bodies and to upper atmospheres of larger bodies such as Titan and Pluto. Relative absence of the universal suprathermal spectrum in the mid-heliospheric region of the classical Kuiper Belt may profoundly affect surface color diversity of icy bodies in this region.

Cooper, John F.↗
NASA NTRS1994

Plasma heating for containerless and microgravity materials processing

A method for plasma heating of levitated samples to be used in containerless microgravity processing is disclosed. A sample is levitated by electrostatic, electromagnetic, aerodynamic, or acoustic systems, as is appropriate for the physical properties of the particular sample. The sample is heated by a plasma torch at atmospheric pressure. A ground plate is provided to help direct the plasma towards the sample. In addition, Helmholtz coils are provided to produce a magnetic field that can be used to spiral the plasma around the sample. The plasma heating system is oriented such that it does not interfere with the levitation system.

Leung, Emily W.↗
NASA NTRS1992

Plasma separation

This process employs a thermal plasma for the separation and production of oxygen and metals. It is a continuous process that requires no consumables and relies entirely on space resources. The almost complete absence of waste renders it relatively clean. It can be turned on or off without any undesirable side effects or residues. The prime disadvantage is its high power consumption.

Steurer, Wolfgang↗
DOE OSTI2023

Plasma catalytic non-oxidative methane conversion to hydrogen and value-added hydrocarbons on zeolite 13X

Non-thermal plasma has unfolded highly efficient, safe to operate novel routes for methane conversion to hydrogen. In this work, methane conversion is performed under atmospheric dielectric barrier discharge (DBD) plasma with and without 13X zeolite-based catalysts i.e., 13X, Ga/13X, Pd/13X, and Pd-Ga/13X. Experimental results indicate that the plasma catalytic process delivered almost twofold higher product yield than the plasma only route. The binary Pd-Ga catalyst possesses highest catalytic performance with about 40 % CH 4 conversion at an input flowrate of 5 cm 3 min -1 and 2W due to the formation of the Pd-Ga alloy, which acts as catalytic active centre for activating C–H bonds. Product yield can be tailored by the catalyst design where the bimetallic Pd-Ga/13X preferably favours the hydrocarbon formation while H 2 is the dominant product obtained over the Pd/13X. The cleavage of C–H bonds of methane molecule over the plasma only route is mainly governed by energetic electrons in the gaseous phase the catalyst activity, and plasma-catalyst synergism play a significant role in the plasma catalysis process. Further, the findings from this work provide significant insights into the methane activation for subsequent optimization of the methane conversion processes operated on floating production, storage, and offloading vessels (FPSOVs). Exploiting untapped offshore natural gas reserves, where conventional pipeline systems are less economical.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Direct Observation of Plasma-Stimulated Activation of Surface Species Using Multimodal In Situ/Operando Spectroscopy Combining Polarization-Modulation Infrared Reflection-Absorption Spectroscopy, Optical Emission Spectroscopy, and Mass Spectrometry

Nonthermal plasmas (NTPs) produce reactive chemical environments, including electrons, ions, radicals, and vibrationally excited molecules, that can drive chemistry at temperatures at which such species are thermally inaccessible. There has been growing interest in the integration of conventional catalysis with reactive NTPs to promote novel chemical transformations. Unveiling the full potential of plasma-catalytic processes requires a comprehensive understanding of plasma-catalytic synergies, including characterization of plasma-catalytic surface interactions. In this work, we report on a newly designed multimodal spectroscopic instrument combining polarization-modulation infrared reflection-absorption spectroscopy (PM-IRAS), mass spectrometry, and optical emission spectroscopy (OES) for the investigation of plasma–surface interactions such as those found in plasma catalysis. In particular, this tool has been utilized to correlate plasma-phase chemistry with both surface chemistry and gas-phase products in situ (1) during the deposition of carbonaceous surface species via NTP-promoted nonoxidative coupling of methane and (2) during subsequent activation of surface deposits with an atmospheric pressure and temperature argon plasma jet on both nickel (Ni) and silicon dioxide (SiO 2 ) surfaces. For the first time, the activation of carbonaceous surface species by a NTP on Ni and SiO 2 surfaces to form hydrogen gas and C 2 hydrocarbons was directly observed, where both PM-IRAS and OES measurements suggest that they may form through different pathways. Furthermore, this unique tool for studying plasma–surface interactions could enable more rational design of plasma-stimulated catalytic processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

A Zero-Emission Process for Direct Reduction of Iron by Hydrogen Plasma in a Rotary Kiln Reactor

This project’s goal was to demonstrate a hydrogen plasma (H-plasma)-rotary kiln process for reducing iron ore to iron as part of the steel manufacturing process. The H-plasma provides a greater thermodynamic driving force for reducing iron ores than thermal processes such as the DRI process, enabling lower reaction temperatures. We estimated that our process technology can reduce energy consumption by 45% compared to the blast furnace process and ~15% compared to the DRI process. Steel manufacturing produces about 1.8 tons of CO2/ton of steel with iron ore reduction accounting for about one-third of the CO2 produced in the overall manufacturing process. We estimated our process has the potential to reduce GHG emissions from ironmaking by 35% with today’s grid and by up to 88% with a future low-carbon grid while being cost competitive with the current blast furnace route. We demonstrated reduction of hematite and magnetite rich materials at temperatures from 600 to 800°C. We achieved 90-95% metallization on 100 gr samples in batch reduction experiments in the H-plasma rotary kiln furnace at 600-650°C. Attempts to perform tests in a continuous operation mode identified problems with the ore feed mechanism. We identified solutions but there was not time nor budget to correct these for this project

36 MATERIALS SCIENCE↗