Time-dependent saturation of cross-beam energy transfer relevant to indirect-drive ICF
ORAL
Abstract
Cross-beam energy transfer (CBET) allows crossing laser beams to exchange energy and is critically important for ICF/HED experiments. The nonlinear physics of CBET for multi-speckled laser beams is examined using particle-in-cell simulations for a range of plasma conditions, laser intensities, and crossing angles relevant to indirect-drive ICF experiments. The time-dependent growth and saturation of CBET involve complex, nonlinear ion and electron dynamics, including ion trapping-induced enhancement and detuning, ion acoustic wave (IAW) nonlinearity, oblique forward stimulated Raman scattering (FSRS), and backward stimulated Brillouin scattering (BSBS) in a CBET-amplified seed beam. Ion-trapping-induced detuning of CBET is captured in the kinetic linear response by a new δf-Gaussian-mixture algorithm, enabling an accurate characterization of trapping-induced non-Maxwellian distributions. Nonlinear effects lead to deviation of CBET gain from linear theory based on a single-Maxwellian distribution and are found to determine the time-dependent nature and level of CBET gain as the system approaches steady state.
*This work was supported by the Los Alamos National Laboratory Directed Research and Development (LDRD) Program. VPIC simulations were run on LANL Institutional Computing Clusters. This work was performed under the auspices of the U.S. Department of Energy by Triad National Security, LLC, operator of the Los Alamos National Laboratory under Contract No. 89233218CNA000001.
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Presenters
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Lin Yin
- Los Alamos Natl Lab