Direct observation of stimulated-Brillouin-scattering detuning by a velocity gradient.
We report the first direct evidence of detuning of stimulated Brillouin scattering (SBS) by a velocity gradient, which was achieved by directly measuring the frequency shift of the SBS-driven acoustic wave relative to the local resonant acoustic frequency. We show that in the expanding part of the plasma, ion-acoustic waves are driven off resonance which leads to the saturation of the SBS instability. These measurements are well reproduced by fluid simulations that include the measured flow.
L-399, Lawrence Livermore National Laboratory, University of California, P.O. Box 808, CA 94551, USA.
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DH
Froula
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L
Divol
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A
MacKinnon
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G
Gregori
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SH
Glenzer