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in subjects: "Beam-Plasma Systems"  
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Hopf bifurcation and the beam-plasma instability

Description: 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.
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Partner: UNT Libraries Government Documents Department
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Knock-on electrons in the target chamber

Description: 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.
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Partner: UNT Libraries Government Documents Department
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Focal spot size predictions for beam transport through a gas-filled reactor

Description: 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.
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Partner: UNT Libraries Government Documents Department
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Convective and nonconvective ion beam filamentation instabilities

Description: 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.
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Partner: UNT Libraries Government Documents Department
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Energetic plasma-beam propagation in weak and strong magnetic fields

Description: 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.
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Partner: UNT Libraries Government Documents Department
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Filamentation instability of ion acoustic waves driven by a scattered relativistic beam

Description: 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.
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Partner: UNT Libraries Government Documents Department
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Scientific program and abstracts

Description: 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.)
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Partner: UNT Libraries Government Documents Department
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Determination of the radius of a self-pinched beam from its energy integral

Description: The total transverse energy (kinetic plus potential) of a self-pinched beam may be used to predict the final equilibrium radius when the beam is mismatched at injection. The dependence of potential energy on the current profile shape is characterized by a dimensionless parameter C(z), variations of which are correlated with the change of emittance.
Date: January 2, 1980
Creator: Lee, Edward P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Optical-emission studies in the ion-focused regime

Description: The utility of optical emissions for diagnostic purposes in the ion-focused regime is explored. Two possible uses of the emissions are examined: (1) the time delay of 337.1-nm emissions relative to 391.4-nm emissions is observed to scale with the beam-neutralization time, and (2) emissions at 391.4 nm may determine beam-current density at the front of the beam.
Date: January 5, 1983
Creator: Chong, Y. P.; Yu, S. S.; Masamitsu, J. A.; Fessenden, T. J. & Prono, D. S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Storage ring injection

Description: Some basic issues involved in injecting the beam into storage rings with the principal parameters of those studied at the workshop have been considered. The main conclusion is that straightforward adjustments of the storage ring parameters makes injection easy. The largest number of injected turns is fourteen, and the phase space dilution allowance seems adequate to ensure very small beam loss during injection. The adjustments also result in lower bending magnet fields, and high field supercond… more
Date: January 1, 1980
Creator: Burke, R.J.
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Partner: UNT Libraries Government Documents Department
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Beam propagation through a gaseous reactor: classical transport

Description: The present calculations are applicable to any beam geometry with cylindrical symmetry, including the converging beam geometry (large entrance port with radius > or approx. = 10 cm), as well as the pencil-shaped beam (small porthole with radius approx. mm). The small porthole is clearly advantageous from the reactor vessel design point of view. While the physics of the latter mode of propagation may be more complex, analyses up to this point have not revealed any detrimental instability effects… more
Date: January 17, 1979
Creator: Yu, S. S.; Buchanan, H. L.; Lee, E. P. & Chambers, F. W.
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Partner: UNT Libraries Government Documents Department
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Electromagnetic brake

Description: The interaction of a relativistic electron beam with a laser pulse in a target plasma is theoretically described. An analysis is given for the stimulated bremsstrahlung effect. (MOW)
Date: January 1, 1976
Creator: Sahlin, H. L.
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Partner: UNT Libraries Government Documents Department
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Nonlocal Boltzmann theory of plasma channels

Description: The mathematical framework for the LLNL code NUTS is developed. This code is designed to study the evolution of an electron-beam-generated plasma channel at all pressures. The Boltzmann treatment of the secondary electrons presented include all inertial, nonlocal, electric and magnetic effects, as well as effects of atomic collisions. Field equations are advanced simultaneously and self-consistently with the evolving plasma currents.
Date: January 3, 1983
Creator: Yu, S. S. & Melendez, R. E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Thomson-scattering measurements of electron temperature and density in a plasma channel created by a relativistic electron beam

Description: The electron density (n/sub e/) and temperature (T/sub e/) of the plasma channel created by the propagation of a relativistic electron beam in air have been measured by a ruby laser Thomson scattering diagnostic. The measurements were made at the MIMI electron beam accelerator (1.6 MV, 21 kA, 70 ns) at various times during the plasma channel development, with 25 ns temporal resolution and 2 mm radial resolution. For example, in 5 Torr air, at the time of maximum electron beam current, the resul… more
Date: January 1, 1983
Creator: Allen, G. R.; Parke Davis, H. & Brandenburg, J. E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Ion beam propagation simulations

Description: A series of numerical particle-in-cell simulations of ion beam propagation have been performed with the LASL two-dimensional electromagnetic code, CCUBE. A few results for each of two different simulations are presented. They are intended to illustrate plasma effects relevant to (1) ion propagation in a relatively dense plasma background, and (2) ion vacuum propagation with co-moving electrons.
Date: January 1, 1979
Creator: Lemons, Don S.
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Partner: UNT Libraries Government Documents Department
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Space-time evolution of the nonlinear two-stream instability

Description: A cold electron beam penetrating a cold plasma is electrostatically unstable. The instability produces a growing electric field that saturates when the beam electrons are suddenly trapped by a single wave. During trapping a significant amount of energy is transferred from the beam to the field and ultimately to the plasma. At Los Alamos experiments are being performed that demonstrate this anomalous beam-driven plasma heating. The heating efficiency is a function of the phase velocity of the tr… more
Date: January 1, 1983
Creator: Lemons, Don S.; Jones, Michael E. & Lee, Huan
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Partner: UNT Libraries Government Documents Department
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Simulations of the effects of mobile ions on the relativistic beam-plasma instability for intense beams

Description: Particle-in-cell simulations of the beam-plasma instability for intense relativistic electron beams in dense plasmas show rapid heating of the electrons to multi-kilovolt temperatures. The resulting hydrodynamic motion of the plasma results in density gradients that degrade the interaction. Heat flow out of the plasma is found in some instances to limit the gradient formation process.
Date: January 1, 1983
Creator: Jones, Michael E.; Lemons, Don S. & Lee, Huan
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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