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in subjects: "Beam-Plasma Systems"

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Mathematical models and illustrative results for the RINGBEARER II monopole/dipole beam-propagation code

RINGBEARER II is a linearized monopole/dipole particle simulation code for studying intense relativistic electron beam propagation in gas. In this report the mathematical models utilized for beam particle dynamics and pinch field computation are delineated. Difficulties encountered in code operations and some remedies are discussed. Sample output is presented detailing the diagnostics and the methods of display and analysis utilized.

Date: May 24, 1982

Creator: Chambers, F.W.; Masamitsu, J.A. & Lee, E.P.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Stability of space-charge neutralized beams

Consideration is given to the stability of negative ion beams which are neutralized through ionization of a background gas. Two types of instabilities are examined. First, beam-plasma instabilities are analyzed with the dispersion relation showing that they are unimportant if the beam velocity is less than the electron thermal velocity. Second, results of a computer simulation on the flow of a cylindrical beam and the resulting background plasma show that when the background neutral gas density… more

Date: September 22, 1977

Creator: Turnbull, R. J. & Hooper, E. B. Jr.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Stable propagation of a high-current electron beam: experimental observations and computational modeling

Experimental studies of self-focused, high-current electron-beam propagation phenomena are compared with the results of computational modeling. The model includes the radial structure of the beam-plasma system, a full electromagnetic field description, primary and secondary gas ionization processes, and a linear theory of the hose-like distortions. Good agreement between the experimental results and the computations strengthens the premise that hose instability is the principal limitation to pr… more

Date: August 1, 1977

Creator: Briggs, R.; Clark, J.; Fessenden, T.; Lee, E. & Lauer, E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Stable propagation of an electron beam in gas

Conditions for the stable propagation of a pinched electron beam in low pressure gas (p approximately 0.1 to 100 torr) are described. The observed window of good propagation around p approximately 2 torr air is interpreted as the quenching of the two-stream mode by sufficiently high plasma density and collision frequency, and the simultaneous suppression of the resistive hose mode by sufficiently rapid generation of electrical conductivity from breakdown ionization.

Date: September 30, 1977

Creator: Lee, E. P.; Chambers, F. W.; Lodestro, L. L. & Yu, S. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Hopf bifurcation and the beam-plasma instability

For finite mode instabilities in dissipative systems, invariant manifold methods allow the bifurcation analysis to be reduced to the locally attracting center manifold. In a kinetic model of electron plasma dynamics, these methods are applied to the one mode beam-plasma instability which occurs via Hopf bifurcation. The instability results in a nonlinear oscillation, and the amplitude equation can be solved to describe the time asymptotic state.

Date: January 1, 1984

Creator: Crawford, J. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Linear and non-linear calculations of the hose instability in the ion-focused regime

A simple model is adopted to study the hose instability of an intense relativistic electron beam in a partially neutralized, low density ion channel (ion focused regime). Equations of motion for the beam and the channel are derived and linearized to obtain an approximate dispersion relation. The non-linear equations of motion are then solved numerically and the results compared to linearized data.

Date: June 14, 1982

Creator: Buchanan, H.L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Electromagnetic Effects in Relativistic Electron Beam Plasma Interactions

Electromagnetic effects excited by intense relativistic electron beams in plasmas are investigated using a two-dimensional particle code. The simulations with dense beams show large magnetic fields excited by the Weibel instability as well as sizeable electromagnetic radiation over a significant range of frequencies. The possible relevance of beam plasma instabilities to the laser acceleration of particles is briefly discussed. 6 refs., 4 figs.

Date: February 13, 1985

Creator: Kruer, W. L. & Langdon, A. B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Propagation of a heavy ion beam in gas-filled reactor

A heavy ion beam traversing a gas-filled reactor is stripped of its electrons along its path. The propagation of the stripping beam with possible associated instabilities has been investigated.

Date: November 3, 1977

Creator: Yu, S. S.; Buchanan, H. L.; Chambers, F. W. & Lee, E. P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Relativistic electron beam plasma heating experiment

An intense (5 x 10/sup 5/ Amp/cm/sup 2/), relativistic (5 MeV), electron beam will be used to investigate the heating of small volumes (approx. 5 to 10 cm/sup 3/) of dense plasma (10/sup 17/ to 10/sup 18/ electrons/cm/sup 3/) to kilovolt temperatures via the electrostatic two-stream instability.

Date: April 1, 1980

Creator: Montgomery, M. D. & Parker, J. V.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Atomic data needs for beam transport in gas

Determination of the parameters Z/sub eff/, electrical conductivity, plasma density, and the plasma temperature is essential in the study of heavy ion beam transport in gas. The calculation of these parameters require input from atomic physics. This note is an attempt to make these needs known to atomic physicists.

Date: November 3, 1977

Creator: Yu, S. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Propagation of ion beams through a tenuous magnetized plasma

When an ion beam is propagated through a plasma, the question of charge neutralization is critical to its propagation. We consider such a problem where the plasma is magnetized with magnetic field perpendicular to the beam. The plasma-number density and beam-number density are assumed comparable. We reduce the problem to a two-dimensional model, which we solve. The solution suggests that it should be possible to attain charge neutralization if the beam density is properly varied along itself.

Date: October 1, 1985

Creator: Chrien, E. F.; Valeo, E. J.; Kulsrud, R. M. & Oberman, C. R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Knock-on electrons in the target chamber

It is virtually certain that heavy ion beams will produce massive quantities of knock-on electrons for target chamber pressures above 1 torr. It was shown that the magnitude of the resulting current is more than sufficient to pinch the knock-on beam in most cases, assuming that a substantial fraction of this beam actually gets out ahead of the ion beam pulse. Although at least some of the ion beam experiences this defocusing, the overall effect on beam propagation is minimal if field reversal i… more

Date: January 1, 1979

Creator: Hubbard, R. F.; Goldstein, S. A. & Tidman, D. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Comparisons of hydrodynamic beam models with kinetic treatments

Hydrodynamic models have been derived by Mark and Yu and by others to describe energetic self-pinched beams, such as those used in ion-beam fusion. The closure of the Mark-Yu model is obtained with adiabatic assumptions mathematically analogous to those of Chew, Goldberger, and Low for MHD. The other models treated here use an ideal gas closure and a closure by Newcomb based on an expansion in V/sub th//V/sub z/. Features of these hydrodynamic beam models are compared with a kinetic treatment.

Date: October 6, 1983

Creator: Boyd, J. K.; Mark, J. W.; Sharp, W. M. & Yu, S. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Focal spot size predictions for beam transport through a gas-filled reactor

Results from calculations of focal spot size for beam transport through a gas-filled reactor are summarized. In the converging beam mode, we find an enlargement of the focal spot due to multiple scattering and zeroth order self-field effects. This enlargement can be minimized by maintaining small reactors together with a careful choice of the gaseous medium. The self-focused mode, on the other hand, is relatively insensitive to the reactor environment, but is critically dependent upon initial b… more

Date: January 23, 1980

Creator: Yu, S. S.; Lee, E. P. & Buchanan, H. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Convective and nonconvective ion beam filamentation instabilities

The electromagnetic filamentation instability is expected to occur in heavy ion beam fusion target chambers. For a converging beam, the instability is expected to be convective with group velocity V/sub g/ approaching the beam velocity V/sub b/ until the beam is approx. 10-50 cm from the target. The number of e-foldings N/sub ..gamma../ is estimated by integrating the local growth rate along the beam trajectory. For a cold beam, the result agrees with the initial value problem solution of Lee, … more

Date: January 1, 1980

Creator: Hubbard, R.F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Energetic plasma-beam propagation in weak and strong magnetic fields

Dynamical aspects of a relativistic plasma beam propagating across a magnetic field are investigated through two- and three-dimensional particle-in-cell numerical simulations. In the two-dimensional simulations, different aspects of the physics are revealed by placing the initial ambient field perpendicular to and within the plane of calculation. In the former case the expected beam polarization appears at early times in the simulations but is quickly dominated by collectively induced heating. … more

Date: January 1, 1983

Creator: Shanahan, W.R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Filamentation instability of ion acoustic waves driven by a scattered relativistic beam

Ion-acoustic instability driven by a scattered relativistic beam propagating in a plasma of hot electrons and cold ions is investigated. We have derived a fully electromagnetic dispersion relation and its cold beam limit and discussed the general features of the growth rate spectrum. We find that this instability is sensitively damped by th beam temperature. Particle trapping and nonlinear growth are studied by using particle-in-cell simulations.

Date: January 1, 1983

Creator: Lee, H. & Jones, M.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Simple model of beam transport in low-pressure ion-focused regimes

This paper presents a simple model of self-focused beam transport at very low gas pressures, where fractional electric neutralization is incomplete and secondary electrons are expelled from the beam region.

Date: September 1, 1981

Creator: Briggs, R. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Theory and simulations of current drive via injection of an electron beam in the ACT-1 device

One- and two-dimensional particle simulations of beam-plasma interaction have been carried out in order to understand current drive experiments that use an electron beam injected into the ACT-1 device. Typically, the beam velocity along the magnetic field is V = 10/sup 9/ cm/sec while the thermal velocity of the background electrons is v/sub t/ = 10/sup 8//cm. The ratio of the beam density to the background density is about 10% so that a strong beam-plasma instability develops causing rapid dif… more

Date: February 1, 1985

Creator: Okuda, H.; Horton, R.; Ono, M. & Wong, K. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Review of electron-beam heating of magnetic-mirror confined plasmas, with application to the Tandem Mirror Experiment

This report reviews results from early electron-beam heating experiments and more recent basic beam-plasma physics experiments as well as present theoretical understanding. We find tha rather simple electron-beams could be employed on the Tandem Mirror Experiment (TMX) at Lawrence Livermore Laboratory to carry out electron heating experiments.

Date: April 10, 1979

Creator: Seidl, M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Relativistic electron beam propagation: two-stream theory, January 1978-January 1979

Progress achieved in the theoretical understanding of the two-stream instability as it pertains to the propagation of relativistic electron beams through low pressure neutral gases is presented. Research has been performed on both aspects of the stability issue: linear stabilization of the two-stream mode and the nonlinear state of an unstable system.

Date: July 1, 1979

Creator: Newberger, B.S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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New concepts in particle acceleration

Accelerator concepts discussed include the wake-field accelerator, the two-beam accelerator, the inverse free electron laser, and the laser plasma wave accelerator. (GHT). 18 references, 12 figures.

Date: August 1, 1983

Creator: Sessler, Andrew M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Anomalous electron diffusion across a magnetic field in a beam-plasma system

The diffusion of electrons across a magnetic field in the presence of a beam-plasma instability has been studied by means of two-dimensional numerical simulations. It is found that the beam electrons can diffuse much faster across the magnetic field than the thermal electrons. This can be explained by the fact that the electrons in the beam are in resonance with the waves excited by the beam-plasma instability so that they experience a nearly dc electric field, causing large cE x B/B/sup 2/ exc… more

Date: October 1, 1987

Creator: Okuda, H.; Ono, M. & Armstrong, R.J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Scientific program and abstracts

The Fifth International Conference on High-Power Particle Beams is organized jointly by the Lawrence Livermore National Laboratory and Physics International Company. As in the previous conferences in this series, the program includes the following topics: high-power, electron- and ion-beam acceleration and transport; diode physics; high-power particle beam interaction with plasmas and dense targets; particle beam fusion (inertial confinement); collective ion acceleration; particle beam heating … more

Date: January 1, 1983

Creator: Gerich, C. (ed.)

Item Type: Article

Partner: UNT Libraries Government Documents Department