Defocusing of an ion beam propagating in background
plasma
due to two-stream instability
Authors: Erinc Tokluoglu and Igor Kaganovich
Abstract: The current and charge neutralization of
charged particle beams by background plasma enables ballistic beam
propagation and has a wide range of applications in inertial
fusion and high energy density physics. However, the beam-plasma
interaction can result in the development of collective
instabilities that may have deleterious effects on ballistic
propagation of an ion beam. In the case of fast, light-ion beams
non-linear fields created by instabilities can lead to significant
defocusing of the beam. We study an ion beam pulse propagating in
a background plasma, which is subject to two-stream instability
between the beam ions and plasma electrons, using PIC code LSP.
The defocusing effects of the instability on the beam can be much
more pronounced in small radius beams. We show through simulations
that a beamlet produced from an ion beam passed through an
aperture can be used as a diagnostic tool to identify the presence
of the two-stream instability and quantify its defocusing effects.
The effect can be observed on the National Drift Compression
Experiment-II (NDCX-II) facility by measuring the spot size of the
extracted beamlet propagating through several meters of plasma.
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Submitted to: Physics of Plasmas
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Download PPPL-5134 (pdf 4.5 MB 13pp)
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