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Author(s):
Lj. Nikolic, M.M. Skoric, S. Ishiguro and T. Sato
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Title:
On Stimulated Scattering of Laser Light in Inertial Fusion Energy Targets
Date of publication:
Nov. 2002
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Key words:
laser-plasma instabilities, particle simulations
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Abstract:
Propagation of a laser light through regions of an underdense plasma is an active research topic in laser fusion. In particular, a large effort has been invested in studies of stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) which can reflect laser energy and produce energetic particles to preheat a fusion energy target. Experiments, theory and simulations agree on a complex interplay between various laser-plasma instabilities. By particle-in-cell simulations of an underdense electron-plasma, we have found, apart from the standard SRS, a strong backscattering near the electron plasma frequency at densities beyond the quarter critical. This novel instability, recognized in recent experiments as stimulated laser scattering on a trapped electron-acoustic mode (SEAS), is absent from a classical theory of laser-parametric instabilities. A parametric excitation of SEAS instability, is explained by a three-wave resonant decay of the incident laser light into a standing backscattered wave and a slow trapped electron-acoustic wave (omega < omega_p). Large SEAS pulsations, eventually suppressed by relativistic heating of electrons, are observed in our simulations. This phenomenon seems relevant to future hohlraum target and fast ignition experiments.
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