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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Innovative techniques for the production of energetic radicals for lunar processing including cold plasma processing of local planetary ores

Hydrogen reduction of ilmenite has been studied by a number of investigators as a potential means for recovery of oxygen from lunar soil. Interest in this process has always rested with the simplicity of the flow diagram and the utilization of established technology. Effective utilization of hydrogen in the reduction process at temperatures of 1200 C and below has always been disappointing and, as such, has led other investigators to focus attention on other systems. Effective utilization of hydrogen in the reduction of ilmenite can be significantly enhanced in the presence of a non-equilibrium hydrogen plasma. Ilmenite at solid specimen temperatures of 600 C to 970 C were reacted in a hydrogen plasma. Those experiments revealed that hydrogen utilization can be significantly enhanced. At a specimen temperature of 850 C the fraction of H2 reacted was 24 percent compared to the 7 percent theoretical limit calculated with thermodynamic theory for the same temperature. An added advantage for a hydrogen plasma involves further reduction of TiO2. Reduction of the iron oxide in ilmenite yields TiO2 and metallic iron as by products. Titanium forms a number of oxides including TiO, Ti2O3, Ti3O5 and the Magneli oxides (Ti4O7 to Ti50O99). In conventional processing of ilmenite with hydrogen it is possible to reduce TiO2 to Ti7O13 within approximately an hour, but with poor utilization of hydrogen on the order of one mole of H2 per thousand. In the cold or non-equilibrium plasma TiO2 can be rapidly reduced to Ti2O3 with hydrogen utilization exceeding 10 percent. Based on design considerations of the plasma reactor greater utilization of the hydrogen in the reduction of TiO2 is possible.

Bullard, D.↗
NASA NTRS2000

Ionization Properties of Molecules Commonly Used for Plasma Processing of Semi-Conductors

Two types of processes are involved in plasma processing of semi-conductors. They are: plasma etching or cleaning and plasma deposition of the semi-conducting materials. For plasma etching of semi-conductors mostly halogen containing gases are used as additives to gases such as O2 and N2. For plasma deposition gases such as C2H2, SiH4, Si2H6 have been tested in the past. For an optimal performance of a reactor it is important to model the plasma. In this modeling effort electron impact excitation and ionization cross sections play a central role. For ionization balance calculations values of ionization cross sections are needed. Ion molecule reactions determine the ultimate composition of the plasma. Recently it has been discovered that the by products of many of these plasmas are per fluro hydrocarbons (PFCs) which are highly infrared absorbing species and have long life times in the atmosphere. They cause global warming. A lot of research is being pursued at the present time to find alternative molecules which do not produce global warming gases as the and product of the plasma processing reactor. There is also interest in the ionization and dissociative ionization properties of these molecules from the point view of the plasma abatement of the pollutant gases at the exhaust of the semi-conductor processing reactors. At the conference ionization and dissociative ionization properties of some of these molecules will be presented.

Srivastava, S. K.↗
NASA NTRS1987

Simulations of auroral plasma processes - Electric fields, waves and particles

Plasma processes driven by current sheets of finite thicknesses in an ambient magnetized plasma are studied using a 2 1/2 dimensional particle-in-cell code, and similarities are found between simulated plasma processes and those observed in the auroral plasma. Current sheets are shown to be bounded by large perpendicular electric fields occurring near their edges above the conducting boundary. Shaped potential structures form when the current sheets are narrow, and when the current sheets are wide, potential structures develop a significant parallel potential drop such that the electrons are accelerated upwards. Downward parallel electric fields of variable strength are noted in the downward current region, and double layer formation is seen in both narrow and wide current sheets. High frequency oscillations near the electron plasma frequency and its harmonic are seen, and low frequency waves are observed.

Singh, Nagendra↗
NASA NTRS2008

Plasma Processing of Lunar Regolith Simulant for Diverse Applications

Versatile manufacturing technologies for extracting resources from the moon are needed to support future space missions. Of particular interest is the production of gases and metals from lunar resources for life support, propulsion, and in-space fabrication. Deposits made from lunar regolith could yield highly emissive coatings and near-net shaped parts for replacement or repair of critical components. Equally important is development of high fidelity lunar simulants for ground based validation of potential lunar surface operations. Described herein is an innovative plasma processing technique for insitu production of gases, metals, coatings, and deposits from lunar regolith, and synthesis of high fidelity lunar simulant from NASA issued lunar simulant JSC-1. Initial plasma reduction trials of JSC-1 lunar simulant have indicated production of metallic iron and magnesium. Evolution of carbon monoxide has been detected subsequent to reduction of the simulant using the plasma process. Plasma processing of the simulant has also resulted in glassy phases resembling the volcanic glass and agglutinates found in lunar regolith. Complete and partial glassy phase deposits have been obtained by varying the plasma process variables. Experimental techniques, product characterization, and process gas analysis will be discussed.

Schofield, Elizabeth C.↗
NASA NTRS1993

Numerical simulation of plasma processes driven by transverse ion heating

The plasma processes driven by transverse ion heating in a diverging flux tube are investigated with numerical simulation. The heating is found to drive a host of plasma processes, in addition to the well-known phenomenon of ion conics. The downward electric field near the reverse shock generates a doublestreaming situation consisting of two upflowing ion populations with different average flow velocities. The electric field in the reverse shock region is modulated by the ion-ion instability driven by the multistreaming ions. The oscillating fields in this region have the possibility of heating electrons. These results from the simulations are compared with results from a previous study based on a hydrodynamical model. Effects of spatial resolutions provided by simulations on the evolution of the plasma are discussed.

Singh, Nagendra↗
NASA NTRS1998

Plasma Processing of Metallic and Semiconductor Thin Films in the Fisk Plasma Source

The use of plasmas to process materials has become widespread throughout the semiconductor industry. Plasmas are used to modify the morphology and chemistry of surfaces. We report on initial plasma processing experiments using the Fisk Plasma Source. Metallic and semiconductor thin films deposited on a silicon substrate have been exposed to argon plasmas. Results of microscopy and chemical analyses of processed materials are presented.

Lampkin, Gregory↗
NASA NTRS2009

Two-Step Plasma Process for Cleaning Indium Bonding Bumps

A two-step plasma process has been developed as a means of removing surface oxide layers from indium bumps used in flip-chip hybridization (bump bonding) of integrated circuits. The two-step plasma process makes it possible to remove surface indium oxide, without incurring the adverse effects of the acid etching process.

Greer, Harold F.↗
NASA NTRS1988

Refilling of a plasmaspheric flux tube - Microscopic plasma processes

The paper elucidates those microscopic plasma processes (electrostatic shocks, pitch angle scattering of the ions, and ion perpendicular heating) which help in trapping and/or thermalizing the plasma in the flux tubes. The mechanism and conditions for electrostatic shock formation are discussed. It is shown that equatorial ion heating stops interhemispheric flow by setting up a potential barrier at the equator.

Singh, N.↗
NASA NTRS1997

Computational Modeling in Plasma Processing for 300 mm Wafers

Migration toward 300 mm wafer size has been initiated recently due to process economics and to meet future demands for integrated circuits. A major issue facing the semiconductor community at this juncture is development of suitable processing equipment, for example, plasma processing reactors that can accomodate 300 mm wafers. In this Invited Talk, scaling of reactors will be discussed with the aid of computational fluid dynamics results. We have undertaken reactor simulations using CFD with reactor geometry, pressure, and precursor flow rates as parameters in a systematic investigation. These simulations provide guidelines for scaling up in reactor design.

Meyyappan, Meyya↗
NASA NTRS1986

Plasma processes driven by current sheets and their relevance to the auroral plasma

Plasma processes dealing with ac and dc electric fields, the formation of ion beams and conics, and electron acceleration are considered, and similarities between simulation results and satellite-based observations are discussed. Electrostatic shock-type electric fields are found to occur near the current sheet edges, and double layers having upward electric fields form inside the sheet and are distinguishable from the large perpendicular electric fields only in wide sheets with thicknesses much greater than the ion Larmor radius. It is found that the most energetic ions have pitch angles near 90 deg, indicating a large perpendicular acceleration of the ions, and that the downward accelerating electrons inside the sheet are neither monoenergetic nor perfectly field aligned.

Singh, Nagendra↗
NASA NTRS1991

Plasma processes in the inner coma

The physical processes that determine the plasma behavior in the inner coma region of active comets are reviewed. Results of observations of the plasma and fields inside the cometopause of Comets Halley and Giacobini-Zinner by instruments on board several spacecraft are presented. Several plasma populations are found to exist in the inner coma. The characteristics of a particular population are largely determined by how far upstream the population was created. All particle populations in the inner coma are strongly affected by collisional processes, such as charge-transfer, ion-neutral chemistry, ion-neutral friction, and thermal cooling. Plasma processes, in the form of magnetohydrodynamics, are also important in the inner coma.

Cravens, T. E.↗
NASA NTRS1988

Review of microscopic plasma processes of occurring during refilling of the plasmasphere

Refilling of the plasmashere after geomagnetic storms involves both macroscopic and microscopic plasma processes. The latter types of processes facilitate the refilling by trapping the plasma in the flux tube and by thermalizing the interhemispheric flow. A review of studies on microscopic processes is presented. The primary focus in this review is on the processes when the density is low and the plasma is collisionless. The discussion includes electrostatic shock formation, pitch angle scatterring extended ion heating and localized ion heating in the equatorial region.

Singh, N.↗
NASA NTRS2002

Double Layers in Expanding Plasmas and Their Relevance to the Auroral Plasma Processes

When a dense plasma consisting of a cold and a sufficiently warm electron population expands, a rarefaction shock forms. In the expansion of the polar wind in the magnetosphere, it has been previously shown that when a sufficiently warm electron population also exists, in addition to the usual cold ionospheric one, a discontinuity forms in the electrostatic potential distribution along the magnetic field lines. Despite the lack of spatial resolution and the assumption of quasi-neutrality in the polar wind models, such discontinuities have been called double layers (DLs). Recently similar discontinuities have been invoked to partly explain the auroral acceleration of electrons and ions in the upward current region. By means of one-dimensional Vlasov simulations of expanding plasmas, for the first time we make here the connection between (i) the rarefaction shocks, (ii) the discontinuities in the potential distributions, and (iii) DLs. We show that when plasmas expand from opposite directions into a deep density cavity with a potential drop across it and when the plasma on the high-potential side contains two electron populations, the temporal evolution of the potential and the plasma. distribution generates evolving multiple double layers with an extended density cavity between them. One of the DLs is the rarefaction-shock (RFS) and it forms by the reflections of the cold electrons coming from the high-potential side; it supports a part of the potential drop approximately determined by the hot electron temperature.

Singh, Nagendra↗
NASA NTRS2003

Double Layers in Expanding Plasmas and Their Relevance to the Auroral Plasma Processes

When a dense plasma consisting of a cold and a sufficiently warm electron population expands, a rarefaction shock forms [Bezzerides et al., 1978]. In the expansion of the polar wind in the magnetosphere, it has been previously shown that when a sufficiently warm electron population also exists, in addition to the usual cold ionospheric one, a discontinuity forms in the electrostatic potential distribution along the magnetic field lines [Barakat and Schunk, 1984]. Despite the lack of spatial resolution and the assumption of quasi-neutrality in the polar wind models, such discontinuities have been called double layers (DLs). Recently similar discontinuities have been invoked to partly explain the auroral acceleration of electrons and ions in the upward current region [Ergun et al., 2000]. By means of one-dimensional Vlasov simulations of expanding plasmas, for the first time we make here the connection between (1) the rarefaction shocks, (2) the discontinuities in the potential distributions, and (3) DLs. We show that when plasmas expand from opposite directions into a deep density cavity with a potential drop across it and when the plasma on the high-potential side contains hot and cold electron populations, the temporal evolution of the potential and the plasma distribution generates evolving multiple double layers with an ,extended density cavity between them. One of the DLs is the rarefaction-shock (RFS) and it forms by the reflections of the cold electrons coming from the high-potential side; it supports a part of the potential drop approximately determined by the hot electron temperature. The other DLs evolve from charge separations arising either from reflection of ions coming from the low-potential side or stemming from plasma instabilities; they support the rest of the potential drop. The instabilities forming these additional double layers involve electron-ion (e-i) Buneman or ion-ion (i-i) two-stream interactions. The electron-electron two-stream interactions on the high-potential side of the RFS generate electron-acoustic waves, which evolve into electron phase-space holes. The ion population originating from the low-potential side and trapped by the RFS is energized by the e-i and i-i instabilities and it eventually precipitates into the high-potential plasma along with an electron beam. Applications of these findings to the auroral plasma physics are discussed.

Singh, Nagendra↗
NASA NTRS1975

Plasma processes in the expansion of the solar wind and in the interplanetary medium

Recent research into plasma processes involved in the expansion of the solar wind and the interplanetary medium is reviewed. Emphasized topics deal primarily with processes that drive the solar wind, the gross expansion of the interplanetary medium between 0.5 and 5 AU, recent observational results in the vicinity of 1 AU, and the microstructure of the interplanetary medium. Satellite measurements of the radial profile of the interplanetary medium out to 5 AU are discussed together with model calculations of the solar wind and its possible driving mechanisms. Studies of Alfven and magnetoacoustic waves in the solar wind are summarized. Possible roles are considered for thermal conduction in coronal energy transport, and observations of ion velocity distributions near 1 AU are described.

Barnes, A.↗
NASA NTRS1986

Solar terrestrial and plasma processes experiments on space station

The currently planned utilization of the space station to perform investigations in solar terrestrial physics and plasma physics is outlined. The investigations and instrumentation planned for the Solar Terrestrial Observatory and its associated space station accommodation requirements are described. In addition, the planned placement of the Solar Terrestrial Observatory instruments are discussed along with typical operational scenarios. In the area of plasma physics, some preliminary plans for scientific investigations and for the accommodation of a plasma physics facility attached to the space station called the Plasma Processes Laboratory are outlined. These preliminary experiment concepts use the space environment around the space station as an unconfined plasma laboratory.

Roberts, W. T.↗