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Author Slutz, S. A. ♦ Lemke, R. W. ♦ Pointon, T. D. ♦ Desjarlais, M. P. ♦ Johnson, D. J. ♦ Mehlhorn, T. A. ♦ Filuk, A. ♦ Bailey, J.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword PLASMA PHYSICS AND FUSION ♦ PHYSICS ♦ ION BEAMS ♦ FLUCTUATIONS ♦ ICF DEVICES ♦ PLASMA SIMULATION ♦ BEAM DYNAMICS ♦ LITHIUM FLUORIDES ♦ LIGHT IONS ♦ PLASMA SHEATH ♦ DIODES
Abstract Magnetically insulated ion diodes are being developed to drive inertial confinement fusion. Ion beam microdivergence must be reduced to achieve the very high beam intensities required to achieve this goal. Three-dimensional particle-in-cell simulations [Phys. Rev. Lett. {bold 67}, 3094 (1991)] indicate that instability-induced fluctuations can produce significant ion divergence during acceleration. These simulations exhibit a fast growing mode early in time, which has been identified as the diocotron instability. The divergence generated by this mode is modest, due to the relatively high-frequency ({approx_gt}1 GHz). Later, a low-frequency low-phase-velocity instability develops with a frequency that is approximately the reciprocal of the ion transit time. This instability couples effectively to the ions, and can generate unacceptably large ion divergences ({approx_gt}30 mrad). Linear stability theory reveals that this mode has structure parallel to the applied magnetic field and is related to the modified two-stream instability. Measurements of ion density fluctuations and energy-momentum correlations have confirmed that instabilities develop in ion diodes and contribute to the ion divergence. In addition, spectroscopic measurements indicate that lithium ions have a significant transverse temperature very close to the emission surface. Passive thin-film lithium fluoride (LiF) anodes have larger transverse beam temperatures than laser-irradiated active sources. Calculations of the ion beam source divergence for the LiF film due to surface roughness and the possible loss of adhesion and fragmentation of this film are presented. {copyright} {ital 1996 American Institute of Physics.}
ISSN 1070664X
Educational Use Research
Learning Resource Type Article
Publisher Date 1996-05-01
Publisher Department Sandia National Laboratory
Publisher Place United States
Journal Physics of Plasmas
Volume Number 3
Issue Number 5
Organization Sandia National Laboratory


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