Ion divergence in magnetically insulated diodes [electronic resource].
- Washington, D.C. : United States. Dept. of Energy, 1995.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
- Physical Description:
- 29 pages : digital, PDF file
- Additional Creators:
- Sandia National Laboratories
United States. Department of Energy
United States. Department of Energy. Office of Scientific and Technical Information
- 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 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 (>1GHz). Later, a low-frequency low-phase-velocity instability develops. This instability couples effectively to the ions, since the frequency is approximately the reciprocal of the ion transit time, and can generate unacceptably large ion divergences (>30 mrad). Linear stability theory reveals that this mode requires perturbations 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 the ions have a significant transverse temperature very close to the emission surface. Passive lithium fluoride (LiF) anodes have larger transverse beam temperatures than laser irradiated active sources. Calculations of source divergence expected from the roughness of LiF surfaces and the possible removal of this layer is presented.
- Published through SciTech Connect.
37. annual meeting of the American Physical Society Division of Plasma Physics, Louisville, KY (United States), 6-10 Nov 1995.
Johnson, D.J.; Bailey, J.; Lemke, R.W.; Slutz, S.A.; Desjarlais, M.P.; Filuk, A.; Pointon, T.D.; Mehlhorn, T.A.
- Funding Information:
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