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Title: Convective Raman amplification of light pulses causing kinetic inflation in inertial fusion plasmas

Abstract

We perform 1D particle-in-cell (PIC) simulations using OSIRIS, which model a short-duration ({approx}500{omega}{sub 0}{sup -1} FWHM) scattered light seed pulse in the presence of a constant counter-propagating pump laser with an intensity far below the absolute instability threshold. The seed undergoes linear convective Raman amplification and dominates over fluctuations due to particle discreteness. Our simulation results are in good agreement with results from a coupled-mode solver when we take into account special relativity and the use of finite size PIC simulation particles. We present linear gain spectra including both effects. Extending the PIC simulations past when the seed exits the simulation domain reveals bursts of large-amplitude scattering in many cases, which does not occur in simulations without the seed pulse. These bursts can have amplitudes several times greater than the amplified seed pulse, and we demonstrate that this large-amplitude scattering is the result of kinetic inflation by examining trapped particle orbits. This large-amplitude scattering is caused by the seed modifying the distribution function earlier in the simulation. We perform some simulations with longer duration seeds, which lead to parts of the seeds undergoing kinetic inflation and reaching amplitudes several times more than the steady-state linear theory results. Simulations with continuousmore » seeds demonstrate that the onset of inflation depends on seed wavelength and incident intensity, and we observe oscillations in the reflectivity at a frequency equal to the difference between the seed frequency and the frequency at which the inflationary stimulated Raman scattering grows.« less

Authors:
 [1];  [2]; ;  [1]; ; ; ;  [3];  [3];  [4]
  1. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
  2. (United States)
  3. University of California, Los Angeles, California 90095 (United States)
  4. (Portugal)
Publication Date:
OSTI Identifier:
22068897
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 19; Journal Issue: 11; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ABSOLUTE INSTABILITIES; DISTRIBUTION FUNCTIONS; INERTIAL CONFINEMENT; INERTIAL FUSION DRIVERS; OPTICAL PUMPING; OSCILLATIONS; PLASMA; PLASMA SIMULATION; RAMAN EFFECT; RELATIVITY THEORY; SCATTERING; SPECTRA; STEADY-STATE CONDITIONS; TRAPPING; VISIBLE RADIATION; WAVELENGTHS

Citation Formats

Ellis, I. N., University of California, Los Angeles, California 90095, Strozzi, D. J., Williams, E. A., Winjum, B. J., Tsung, F. S., Mori, W. B., Fahlen, J. E., Grismayer, T., and Grupo de Lasers e Plasmas, Instituto Superior Tecnico, 1049-001 Lisboa. Convective Raman amplification of light pulses causing kinetic inflation in inertial fusion plasmas. United States: N. p., 2012. Web. doi:10.1063/1.4762853.
Ellis, I. N., University of California, Los Angeles, California 90095, Strozzi, D. J., Williams, E. A., Winjum, B. J., Tsung, F. S., Mori, W. B., Fahlen, J. E., Grismayer, T., & Grupo de Lasers e Plasmas, Instituto Superior Tecnico, 1049-001 Lisboa. Convective Raman amplification of light pulses causing kinetic inflation in inertial fusion plasmas. United States. doi:10.1063/1.4762853.
Ellis, I. N., University of California, Los Angeles, California 90095, Strozzi, D. J., Williams, E. A., Winjum, B. J., Tsung, F. S., Mori, W. B., Fahlen, J. E., Grismayer, T., and Grupo de Lasers e Plasmas, Instituto Superior Tecnico, 1049-001 Lisboa. Thu . "Convective Raman amplification of light pulses causing kinetic inflation in inertial fusion plasmas". United States. doi:10.1063/1.4762853.
@article{osti_22068897,
title = {Convective Raman amplification of light pulses causing kinetic inflation in inertial fusion plasmas},
author = {Ellis, I. N. and University of California, Los Angeles, California 90095 and Strozzi, D. J. and Williams, E. A. and Winjum, B. J. and Tsung, F. S. and Mori, W. B. and Fahlen, J. E. and Grismayer, T. and Grupo de Lasers e Plasmas, Instituto Superior Tecnico, 1049-001 Lisboa},
abstractNote = {We perform 1D particle-in-cell (PIC) simulations using OSIRIS, which model a short-duration ({approx}500{omega}{sub 0}{sup -1} FWHM) scattered light seed pulse in the presence of a constant counter-propagating pump laser with an intensity far below the absolute instability threshold. The seed undergoes linear convective Raman amplification and dominates over fluctuations due to particle discreteness. Our simulation results are in good agreement with results from a coupled-mode solver when we take into account special relativity and the use of finite size PIC simulation particles. We present linear gain spectra including both effects. Extending the PIC simulations past when the seed exits the simulation domain reveals bursts of large-amplitude scattering in many cases, which does not occur in simulations without the seed pulse. These bursts can have amplitudes several times greater than the amplified seed pulse, and we demonstrate that this large-amplitude scattering is the result of kinetic inflation by examining trapped particle orbits. This large-amplitude scattering is caused by the seed modifying the distribution function earlier in the simulation. We perform some simulations with longer duration seeds, which lead to parts of the seeds undergoing kinetic inflation and reaching amplitudes several times more than the steady-state linear theory results. Simulations with continuous seeds demonstrate that the onset of inflation depends on seed wavelength and incident intensity, and we observe oscillations in the reflectivity at a frequency equal to the difference between the seed frequency and the frequency at which the inflationary stimulated Raman scattering grows.},
doi = {10.1063/1.4762853},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 11,
volume = 19,
place = {United States},
year = {2012},
month = {11}
}