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Results for “electron beam plasma”

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 55 records · Page 3
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NASA NTRS1980

Some features of inverted-V events as seen from simulated double layers

Results from a numerical simulation of a double layer show some features similar to those of inverted-V events. The strong heating of thermal and precipitating electrons is observed along with extremely low frequency fluctuations found during inverted-V events. It is suggested that after the acceleration of auroral electrons by the double layer, the precipitating free electrons are heated by the nonlinear effects of the electron beam plasma instability. Fluctuations and pulsations of auroral electron fluxes during auroral events are caused by a relaxation type of oscillation. The finite extent of one dimensional plasma is simulated by solving the Vlasov and Poisson equations as an initial and boundary value problem.

Singh, N.↗
NASA NTRS1987

Space charge effects during the injection of dense electron beams into space plasmas

One-dimensional electrostatic particle simulations are used to investigate the injection and propagation of intense electron beams and the plasma response to the beam injection. Beam densities greater than about the plasma density are considered. It is shown that if the injection is continuous, most of the beam electrons are drawn back into the spacecraft because of the buildup of positive charge on the spacecraft. Those electrons which are able to propagate away from the spacecraft are emitted periodically because of space charge oscillations induced by electric fields associated with the beam. A substantial increase in the fraction and average energy of electrons which can propagate away can be obtained if the injection is changed to periodic pulses having width and period matched to the induced space charge oscillations.

Winglee, R. M.↗
NASA NTRS1990

Electron beams and Langmuir turbulence in solar type III radio bursts observed in the interplanetary medium

Results are presented of in situ observations of electron beams, plasma waves, and associated solar type II radio emission in the interplanetary medium near 1 AU, which were provided by the ISEE-3 spacecraft. It is shown that electron beams are formed by the faster electrons arriving before the slower ones, following an impulsive injection at the sun. The resulting bump-on-tail in the reduced 1D distribution function is unstable to the growth of electrostatic electron plasma (Langmuir) waves. The Langmuir waves are observed to be highly impulsive in nature. The onset and temporal variations of the observed plasma waves are in good qualitative agreement with the wave growth expected from the evolution of the measured 1D distribution function. The lack of obvious plateauing of the bump-on-tail suggests that the waves were removed from resonance with the beam electrons by some wave-wave interaction.

Lin, R. P.↗
NASA NTRS1992

Nonlocal analysis of finite-beam-driven instabilities

The fully kinetic integral eigenmode equation in wave-number space is used to describe the nonlocal behavior of electrostatic waves in an electron-beam plasma, which are studied in the low-temperature-beam regime and the warm-beam regime. The case of strongly magnetized electrons and unmagnetized ions, which corresponds to the waves in a frequency range from the lower-hybrid to the electron plasma frequency, is examined. Three wave modes are found. The first group consists of modes that have dispersive properties similar to the uniform, infinite beam-plasma system. Depending on the beam width, the growth rates are strongly reduced. The second group, surface modes, are localized at the periphery of the beam region and are less unstable than the unstable modes of the first group. The third group represents natural oscillations of the background plasma. These modes are virtually unaffected by the beam.

Serizawa, Y.↗
NASA NTRS1990

Plasma heating, electric fields and plasma flow by electron beam ionospheric injection

The electric fields and the floating potentials of a Plasma Diagnostics Payload (PDP) located near a powerful electron beam injected from a large sounding rocket into the auroral zone ionosphere have been studied. As the PDP drifted away from the beam laterally, it surveyed a region of hot plasma extending nearly to 60 m radius. Large polarization electric fields transverse to B were imbedded in this hot plasma, which displayed large ELF wave variations and also an average pattern which has led to a model of the plasma flow about the negative line potential of the beam resembling a hydrodynamic vortex in a uniform flow field. Most of the present results are derived from the ECHO 6 sounding rocket mission.

Winckler, J. R.↗
NASA NTRS1989

Electron velocity distributions and plasma waves associated with the injection of an electron beam into the ionosphere

An electron beam was injected into earth's ionosphere on August 1, 1985, during the flight of the Space Shuttle Challenger as part of the objectives of the Spacelab 2 mission. In the wake of the Space Shuttle a magnetically aligned sheet of electrons returning from the direction of propagation of the beam was detected with the free-flying Plasma Diagnostics Package. The thickness of this sheet of returning electrons was about 20 m. Large intensifications of broadband electrostatic noise were also observed within this sheet of electrons. A numerical simulation of the interaction of the electron beam with the ambient ionospheric plasmas is employed to show that the electron beam excites electron plasma oscillations and that it is possible for the ion acoustic instability to provide a returning flux of hot electrons by means of quasi-linear diffusion.

Frank, L. A.↗
NASA NTRS1982

Transient effects in beam-plasma interactions in a space simulation chamber stimulated by a fast pulse electron gun

Interest in the interaction of electron beams with plasma generated by ionization caused by the primary electron beam was stimulated by the need to develop special vacuum tubes to operate in the kMHz frequency region. The experiments of Getty and Smullin (1963) indicated that the interaction of an energetic electron beam with its self-produced plasma resulted in the emission of wave energy over a wide range of frequencies associated with cyclotron and longitudinal plasma instabilities. This enhanced the thermal plasma density in the vicinity of the beam, and the term Beam-Plasma Discharge (BPD) was employed to described this phenomenon. The present investigation is concerned with some of the transient phenomena associated with wave emission during the beam switch-on and switch-off periods. Results are presented on the changes in electron energy spectra on a time scale of tens of milliseconds following beam switch-on. The results are discussed in terms of the beam plasma discharge phenomenon.

Raitt, W. J.↗
NASA NTRS1990

Plasma instabilities of a finite-radius electron beam in a uniform plasma

To study electromagnetic radiation induced by electronn beam injection from the Space Shuttle, the electromagnetic dispersion equation or a finite-radius cold electron beam in a neutralizing background was solved numerically. The numerical solutions indicate that a keV electron beam can drive the beam and whistler modes unstable, regardless of whether the beam is homogeneous or has a finite radius. The results obtained were applied to explain the whistler waves radiated from the keV electron beam injected from Spacelab 2.

Wong, H. K.↗
NASA NTRS1988

Energy dependent pitch angle distributions of auroral primary electrons

Double-layer/parallel-electric field accelerations and the subsequent electron-beam plasma interactions involving Cerenkov and anomalous cyclotron resonances are considered. It is found that these phenomena yield pitch angle distributions as noted from rocket and satellite studies. Although the electron acceleration by weak parallel electric fields forming a runaway electron tail is limited to a critical parallel energy determined by the anomalous cyclotron resonance, such a limitation does not occur with acceleration by a localized parallel electric field such as that in a double layer.

Singh, N.↗
NASA NTRS1989

Coherent Cerenkov radiation from the Spacelab 2 electron beam

The plasma environment of the Spacelab 2 mission was investigated through the deployment of the Plasma Diagnostics Package (PDP) by the Space Shuttle Orbiter and the Orbiter's ejection of a continuous 1-keV/50-mA electron beam along a field line. As the PDP flew by the beam, its plasma-wave instrument detected intense whistler-mode radiation originating from the beam. A detailed model has been developed of the coherent Cerenkov emission process, using a one-dimensional computer simulation of the beam to model the expected phase space structure of the electrons. The power calculated for the modeled 200-m beam segment can easily account for the measured whistler mode wave power.

Farrell, W. M.↗
NASA NTRS1989

Electrostatic wave generation above and below the plasma frequency by electron beams

The unmagnetized electrostatic dispersion equation is solved numerically to study the growth of electrostatic waves near the plasma frequency resulting from a unstable electron beam. An attempt is made to find the dispersion relations, frequencies of maximum growth, and the resonant or nonresonant character of the waves for particular beam parameters. It is found that the unstable waves do not have the Langmuir dispersion relation except in the limit of a very dilute beam with growth on the connected mode of O'Neil and Malmberg. The properties of the unstable mode depend strongly on beam parameters such as beam density, speed, and temperature.

Cairns, Iver H.↗
NASA NTRS1985

Radiation from long pulse train electron beams in space plasmas

A previous study of electromagnetic radiation from a finite train of electron pulses is extended to an infinite train of such pulses. The electrons are assumed to follow an idealized helical path through a space plasma in such a manner as to retain their respective position within the beam. This leads to radiation by coherent spontaneous emission. The waves of interest in this region are the whistler slow (compressional) and fast (torsional) Alfven waves. Although a general theory is developed, analysis is then restricted to two approximations, the short and long electron beam. Formulas for the radiation per unit solid angle from the short beam are presented as a function of both propagation and ray angles, electron beam pulse width and separation and beam current, voltage, and pitch angle. Similar formulas for the total power radiated from the long beam are derived as a function of frequency, propagation angle, and ray angle. Predictions of the power radiated are presented for representative examples as determined by the long beam theory.

Harker, K. J.↗
NASA NTRS1982

Science on the Space Shuttle

On the Space Shuttle's third flight, scientific instruments will study the electromagnetic environment with charging and electron beams. Beam plasma discharge will be studied. The plasma diagnostics package contains electromagnetic and particle sensors to study the ionosphere. An attempt will be made to establish a more accurate base of solar UV irradiance measurements with an absolute error of 10 percent or less over the wavelength region 120-400 nm. The solar flare X-ray polarimeter will observe flare X-rays emitted between 5 and 30 keV and measure their polarization as a function of time and photon energy. A photopolarimeter will help study zodiacal light, and interplanetary dust will be sampled by a section of thick aluminum foil. Plant seedlings will be grown to research the effect of near-zero gravity on lignification. A thermal canister experiment will help determine whether instruments can be maintained at a fixed temperature under varying thermal loads.

Neupert, W. M.↗
NASA NTRS1990

Numerical solution of the time-dependent kinetic equation for electrons in magnetized plasma

A numerical solution is developed for the time-dependent kinetic equation describing the evolution of arbitrary distributions of electrons injected into a magnetized plasma. Included in the equation are pitch-angle scattering and energy loss because of Coulomb collisions and magnetic mirroring. The numerical code can be easily modified to include other scattering or radiation terms. The numerical results are shown to agree well with known analytic solutions for various simplified configurations such as homogeneous injection in a homogeneous plasma, electron beams moving with small pitch angle with respect to the magnetic field, and injection into a magnetic trap.

Hamilton, Russell J.↗
NASA NTRS2004

HiPEP Ion Optics System Evaluation Using Gridlets

Experimental measurements are presented for sub-scale ion optics systems comprised of 7 and 19 aperture pairs with geometrical features that are similar to the HiPEP ion optics system. Effects of hole diameter and grid-to-grid spacing are presented as functions of applied voltage and beamlet current. Recommendations are made for the beamlet current range where the ion optics system can be safely operated without experiencing direct impingement of high energy ions on the accelerator grid surface. Measurements are also presented of the accelerator grid voltage where beam plasma electrons backstream through the ion optics system. Results of numerical simulations obtained with the ffx code are compared to both the impingement limit and backstreaming measurements. An emphasis is placed on identifying differences between measurements and simulation predictions to highlight areas where more research is needed. Relatively large effects are observed in simulations when the discharge chamber plasma properties and ion optics geometry are varied. Parameters investigated using simulations include the applied voltages, grid spacing, hole-to-hole spacing, doubles-to-singles ratio, plasma potential, and electron temperature; and estimates are provided for the sensitivity of impingement limits on these parameters.

Willliams, John D.↗
NASA NTRS1992

Simulation study of interactions of Space Shuttle-generated electron beams with ambient plasmas

This report summarizes results obtained through the support of NASA Grant NAGW-1936. The objective of this report is to conduct large scale simulations of electron beams injected into space. The topics covered include the following: (1) simulation of radial expansion of an injected electron beam; (2) simulations of the active injections of electron beams; (3) parameter study of electron beam injection into an ionospheric plasma; and (4) magnetosheath-ionospheric plasma interactions in the cusp.

Lin, Chin S.↗
NASA NTRS1985

Electrostatic ion cyclotron, beam-plasma, and lower hybrid waves excited by an electron beam

It is pointed out that electrostatic ion cyclotron (EIC) waves have been extensively investigated in connection with both space and laboratory plasmas. The present investigation has the objective to study the excitation of low-frequency waves in a multiion plasma by electron beams. The frequencies considered range from below the lowest gyrofrequency of the heaviest ion to about the lower hybrid frequency. It is shown that electron-beam instabilities can produce peaks in the growth rate below the cyclotron frequency of each ion species if nonzero perpendicular wave number effects are included in the ion dynamics. The dispersion relations for neutralized ion Bernstein (NIB) and pure ion Bernstein (PIB) waves are considered along with an instability analysis for a cold plasma and warm electron beam, the electron beam-plasma mode, banded ion cyclotron (EIC) waves with small perpendicular wavelengths, and the growth lengths of the waves.

Singh, N.↗
NASA NTRS1984

Acceleration of electrons in strong beam-plasma interactions

The effects of strong beam-plasma interactions on the electron population of the upper atmosphere have been investigated in an electron acceleration experiment performed with a sounding rocket. The rocket carried the Several Complex Experiments (SCEX) payload which included an electron accelerator, three disposable 'throwaway' detectors (TADs), and a stepped electron energy analyzer. The payload was launched in an auroral arc over the rocket at altitudes of 157 and 178 km, respectively. The performance characteristics of the instruments are discussed in detail. The data are combined with the results of laboratory measurements and show that electrons with energies of at least two and probably four times the injection energy of 2 keV were observed during strong beam-plasma interaction events. The interaction events occurred at pitch angles of 54 and 126 degrees. On the basis of the data it is proposed that the superenergization of the electrons is correlated with the length of the beam-plasma interaction region.

Wilhelm, K.↗