Magneto-Fluid Dynamics Seminar

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Collective regimes of stimulated Brillouin scatter and collapse turbulence in laser fusion

Speaker: Pavel Lushnikov, University of New Mexico

Location: Warren Weaver Hall 905

Date: Tuesday, February 11, 2020, 11 a.m.

Synopsis:

Laser fusion is intended to initiate the nuclear fusion reactions through compressing the thermonuclear target by powerful laser beams. These beams propagate through the surrounding plasma resulting in strongly nonlinear interactions. Perhaps the most important among these interactions is the stimulated Brillouin scattering (SBS) which couples the laser beam to the plasma density fluctuations and results in the numerous catastrophic collapse events during the laser beam propagation. The strong turbulence dominated by such nearly singular collapse event is considered. To suppress the number of such collapses, the expensive optical beams smoothing is used in the experimental laser fusion facilities which randomizes the phases of the laser beams. A statistical theory of SBS of such randomized laser beam propagation is developed. A collective regime of BSBS is found which has a much larger threshold than the classical threshold of a coherent beam in long-scale-length laser fusion plasma. The instability threshold is inside the typical parameter region of National Ignition Facility.