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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 271 records · Page 15

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NASA NTRS1975

Interpretation of neutral particle analyzer measurements on plasmas having azimuthal drift

The theoretical model accounts for drift and cyclotron components of ion motion in a partially ionized plasma. Density and velocity distributions are systematically prescribed. The flux into the neutral particle analyzer (NPA) from this plasma is determined by summing over all charge exchange neutrals in phase space which are directed into apertures. Calculation of the process is continued through the NPA using appropriate cross section data to obtain analyzer output distributions. Theoretical results were compared with NPA measurements on four plasma heating devices having radial electric, E, and axial magnetic, B, fields. Drift velocity, in the azimuthal direction is identified with E/B. Selection of randomized cyclotron velocity distributions about mean azimuthal drift yield energy distributions which compare well with experiment.

Englert, G. W.↗

NASA NTRS1976

Effects of a magnetic field gradient on the lower hybrid drift instability

The effect of a magnetic field gradient on the lower hybrid drift instability is examined in the low drift velocity regime (i.e., of the order of the ion thermal velocity). The theoretical model includes density and temperature gradients, and considers only waves propagating perpendicular to the ambient magnetic field with wavelengths of the order of the electron Larmor radius. It is found, for the case of a finite ratio of the electron pressure to the magnetic field pressure, that a magnetic gradient drift-wave resonance can be important and is stabilizing or destabilizing depending upon the physical conditions. Substantial plasma heating and a large anomalous resistivity can also occur.

Huba, J. D.↗

NASA NTRS1977

Silicon material task. Part 3: Low-cost silicon solar array project

The feasibility of a process for carbon reduction of low impurity silica in a plasma heat source was investigated to produce low-cost solar-grade silicon. Theoretical aspects of the reaction chemistry were studied with the aid of a computer program using iterative free energy minimization. These calculations indicate a threshold temperature exists at 2400 K below which no silicon is formed. The computer simulation technique of molecular dynamics was used to study the quenching of product species.

Roques, R. A.↗

NASA NTRS1977

Analysis of ablation debris from natural and artificial iron meteorites

Artificial ablation studies were performed on iron and nickel-iron samples using an arc-heated plasma of ionized air. Experiment conditions simulated a meteoroid traveling about 12 km/sec at an altitude of 70 km. The artificially produced fusion crusts and ablation debris show features very similar to natural fusion crusts of the iron meteorites Boguslavka, Norfork, and N'Kandhla and to magnetic spherules recovered from Mn nodules. X-ray diffraction, electron microprobe, optical, and scanning electron microscope analyses reveal that important mineralogical, elemental, and textural changes occur during ablation. Some metal is melted and ablated. The outer margin of the melted rind is oxidized and recrystallizes as a discontinuous crust of magnetite and wustite. Adjacent to the oxidized metallic ablation zone is an unoxidized metallic ablation zone in which structures such as Widmannstatten bands are obliterated as the metal is transformed to unequilibrated alpha 2 nickel-iron. Volatile elements are vaporized and less volatile elements undergo fractionation.

Blanchard, M. B.↗

NASA NTRS1977

A hollow cathode hydrogen ion source

Sovey, J. S.↗

NASA NTRS1976

On tenuous plasmas, fireballs, and boundary layers in the earth's magnetotail

The plasma instrumentation (the Lepedea) and the magnetometer aboard IMP 8 performed correlative measurements of magnetic fields and plasmas within the geomagnetic tail at geocentric radial distances of about 23-46 R-E during March-October 1974. The hot tenuous plasmas within the plasma sheet were found to be in a state of almost continuous flow and were threaded with northward, or closed geomagnetic lines. The satellite encountered a region of acceleration in the magnetotail, the 'fireball' which exhibits strong jetting of plasmas in excess of 1000 km/s, proton temperatures of about 10 to the 7th K, disordered magnetic fields, southward magnetic fields during tailward jetting of plasmas, and northward magnetic fields for fast plasma flows toward earth. In addition, the magnetosheath plasmas within the boundary layers which are contiguous to the plasma sheet display evidence of plasma heating, great changes in bulk flow velocities, and acceleration of energetic electrons with an energy of greater than 45 keV.

Frank, L. A.↗

NASA NTRS1978

Analysis of ablation debris from natural and artificial iron meteorites

Iron and nickel-iron samples subjected to treatment by an arc-heated plasma of ionized air were used to model meteor ablation. The artificial ablation debris and fusion crusts were compared to the fusion crusts of three natural iron meteorities and to magnetic spherules from deep-sea manganese nodules. An outer discontinuous crust of magnetite and wuestite, followed by an unoxidized metallic zone, was observed in the artificially produced samples. Fractionation of less volatile elements was also noted.

Blanchard, M. B.↗

NASA NTRS1977

A hollow cathode hydrogen ion source

High current density ion sources have been used to heat plasmas in controlled thermonuclear reaction experiments. High beam currents imply relatively high emission currents from cathodes which have generally taken the form of tungsten filaments. This paper describes a hydrogen ion source which was primarily developed to assess the emission current capability and design requirements for hollow cathodes for application in neutral injection devices. The hydrogen source produced ions by electron bombardment via a single hollow cathode. Source design followed mercury ion thruster technology, using a weak magnetic field to enhance ionization efficiency. A 1.3-cm-diam hollow cathode using a low work function material dispenser performed satisfactorily over a discharge current range of 10-90 A. Cylindrical probe measurements taken without ion extraction indicate maximum ion number densities on the order of 10 trillion/cu cm. Discharge durations ranged from 30 sec to continuous operation. Tests with beam extraction at 2.5 keV and 30 A discharge current yield average ion beam current densities of 0.1 A/sq cm over a 5-cm extraction diameter. Results of this study can be used to supply the baseline information needed to scale hollow cathodes for operation at discharge currents of hundreds of amperes using distributed cathodes.

Sovey, J. S.↗

NASA NTRS1978

Evaluation of performance of select fusion experiments and projected reactors

The performance of NASA Lewis fusion experiments (SUMMA and Bumpy Torus) is compared with other experiments and that necessary for a power reactor. Key parameters cited are gain (fusion power/input power) and the time average fusion power, both of which may be more significant for real fusion reactors than the commonly used Lawson parameter. The NASA devices are over 10 orders of magnitude below the required powerplant values in both gain and time average power. The best experiments elsewhere are also as much as 4 to 5 orders of magnitude low. However, the NASA experiments compare favorably with other alternate approaches that have received less funding than the mainline experiments. The steady-state character and efficiency of plasma heating are strong advantages of the NASA approach. The problem, though, is to move ahead to experiments of sufficient size to advance in gain and average power parameters.

Miley, G. H.↗

NASA NTRS1980

Solar wind flows associated with hot heavy ions

Solar wind heavy ion spectra measured with the Vela instrumentation are studied to determine the solar origins of various solar wind structures which contain anomalously high ionization states. The spectra indicating hot coronal conditions were found to occur in 1/7th of all measurements and almost exclusively in postshock flows, nonshock related helium abundance enhancements, or noncompressive density enhancements. The observation of several flared-related helium abundance enhancements suggests that the flare-heated plasma can evolve into the solar wind without producing a noticeable shock at 1 AU.

Fenimore, E. E.↗

NASA NTRS1981

Ionization states of heavy elements observed in the 1974 May 14-15 anomalous solar particle event

The charge states of heavy ions accelerated in the (3)He-Fe rich solar particle event of 1974 May 14-15 are determined using data from the Interplanetary Monitoring Platform-8. In addition to Fe(+11,12) both 0(+5) and Fe(+16,17,18) are also present suggesting variations in coronal temperatures over a range from approximately 400,000 to 5,000,000 K. The presence of 0(+5) and Fe(+16-18) may be explained by a resonant plasma heating mechanism proposed to account for the enhancements of (3)He and Fe.

Ma Sung, L. S.↗

NASA NTRS1981

X-ray emission from supernova remnants near gamma-ray sources

It is noted that the imaging proportional of the Einstein Observatory has been used to search for X-ray emission from eight radio supernova remnants which are near three of the Cos-B unidentified gamma-ray sources: 2CG 311-01, CG 327-0, and CG 333+0. Emissions are observed from three of the remnants and upper limits on the remainder which are consistent with the luminosity expected from a simple blast-wave heated plasma model of the process. Thus none of the remnants are superluminous as might be expected if the pattern of the Crab Nebula were followed. It is thought that the remnant RCW 103 may be Vela-like. It is noted that another of the remnants, Kes 27, has centrally peaked X-ray emission which is unlike the shell-like emission seen for many remnants and which does not correlate well with its asymmetric radio emission.

Lamb, R. C.↗

NASA NTRS1981

Ionization states of heavy elements observed in the 1974 May 14-15 anomalous solar particle event

The charge states of heavy ions accelerated in the (He-3)-Fe-rich solar particle event of May 14-15, 1974 have been determined by the use of using data from the University of Maryland/Max-Planck-Institut experiment on IMP 8. In addition to Fe(+11,12), it is found that both O(+5) and Fe(+16,17,18) are also present, suggesting variations in coronal temperatures over a range from approximately 400,000 to 5,000,000 K. The presence of O(+5) and Fe(+16-18) may be explained by a resonant plasma heating mechanism proposed by Fisk (1978) to account for the enhancements of He-3 and Fe.

Ma Sung, L. S.↗

NASA NTRS1980

Study of radiatively sustained cesium plasmas for solar energy conversion

The results of a study aimed at developing a high temperature solar electric converter are reported. The converter concept is based on the use of an alkali plasma to serve as both an efficient high temperature collector of solar radiation as well as the working fluid for a high temperature working cycle. The working cycle is a simple magnetohydrodynamic (MHD) Rankine cycle employing a solid electrode Faraday MHD channel. Research milestones include the construction of a theoretical model for coupling sunlight in a cesium plasma and the experimental demonstration of cesium plasma heating with a solar simulator in excellent agreement with the theory. Analysis of a solar MHD working cycle in which excimer laser power rather than electric power is extracted is also presented. The analysis predicts a positive gain coefficient on the cesium-xenon excimer laser transition.

Palmer, A. J.↗

NASA NTRS1981

Broadband electrostatic noise and field-aligned currents in Jupiter's middle magnetosphere

Voyager 1 plasma wave observations have revealed the presence of an impulsive electrostatic emission localized to the Jovian middle magnetosphere that appears on the edges of the plasma sheet. This plasma mode has the same spectral and morphological characteristics of an emission that has been extensively studied in the earth's magnetosphere and has been associated with the presence of field-aligned currents. The results of a detailed study of the properties of this Jovian emission are presented by using comparisons with terrestrial observations as a basis for mode identification. The occurrence regions of the waves are compared with the measured magnetic field configuration to establish a correspondence with the plasma sheet. It is argued that this is a quasi-permanent global system of field-aligned currents linking the ionosphere of Jupiter to the middle magnetosphere, which powers energetic plasma heating processes occurring there. On the basis of knowledge of the consequences of field-aligned currents in the terrestrial magnetosphere, a scenario for acceleration/precipitation of inverted V electrons, concomitant aurorae, and energetic (approximately 10 keV) proton deposition into the middle magnetosphere resulting from field-aligned potential drops associated with this current system is suggested.

Barbosa, D. D.↗

NASA NTRS1982

EUV spectroscopic plasma diagnostics for the solar wind acceleration region

Possibilities are considered for probing physical conditions in the solar corona with strong EUV resonance lines from ions such as N V, O VI, Ne VIII, Mg X, and Si XII. Through measurements of the intensities and profiles of EUV spectral lines with coronagraphic instrumentation employing normal incidence reflecting optics, it is possible to acquire information on electron, proton, and ion temperatures and velocity distributions; electron, H I, and ion densities; mass flow and nonthermal velocities; and chemical abundances. This information will provide critical empirical constraints on physical processes responsible for plasma heating, solar wind acceleration, and transport of mass, momentum, and energy in the solar corona, as well as providing constraints on theoretical models for solar and stellar coronae and mass loss.

Kohl, J. L.↗

NASA NTRS1982

Impulsive phase of flares in soft X-ray emission

Observations using the bent crystal spectrometer instrument on the Solar Maximum Mission show that turbulence and blue-shifted motions are characteristic of the soft X-ray plasma during the impulsive phase of flares, and are coincident with the hard X-ray bursts observed by the hard X-ray burst spectrometer. A method for analysing the Ca XIX and Fe XXV spectra characteristic of the impulsive phase is presented. Nonthermal widths and blue-shifted components in the spectral lines of Ca XIX and Fe XXV indicate the presence of turbulent velocities exceeding 100 km/s and upward motions of 300-400 km/s. The April 10, May 9, and June 29, 1980 flares are studied. The April 10 flare has two separated footpoints bright in hard X-rays. Plasma heated to temperatures greater than ten million K rises from the footpoints. During the three minutes in which the evaporation process occurs an energy of 3.7 x 10 to the 30th ergs. This is consistent with the above figures, allowing for loss by radiation and conduction.

Antonucci, E.↗

NASA NTRS1982

A high-resolution X-ray image of Puppis A - Inhomogeneities in the interstellar medium

Eleven HRI exposures from the Einstein Observatory are assembled into an 0.1-4 keV image of the Puppis A supernova remnant which displays a complex morphology that may reflect the structure of the shocked interstellar medium. In addition to showing a density gradient of a factor greater than four across the approximately 30 pc diameter of the remnant perpendicular to the galactic plane, a shell of X-ray emission is seen surrounding the northern half of Puppis A, coincident with the radio shell, whose edge brightness profile indicates direct hot plasma heating by the blast wave rather than evaporation from clouds. The interior structure of the supernova remnant suggests inhomogeneities whose sizes range over 0.1-5 pc, but with moderate density contrast. Although isolated clouds of 10-30/cu cm density are responsible for the two brightest X-ray features, they represent only a small fraction of the Puppis A mass.

Petre, R.↗