Coupled Modes Analysis of SRS Backscattering, with Langmuir Decay and Possible Cascadings
Name
Ante Salcedo TR662.pdf
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4.25 MB
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411cd1341728ea00f852b4b1daf51771
Author(s)
Salcedo, Ante
Date Issued
June 29, 2006
Series/Report no.
Technical Report (Massachusetts Institute of Technology, Research Laboratory of Electronics);
662
Abstract
Recent experiments aimed at understanding stimulated Raman scattering (SRS) in
ICF laser-plasma interactions, suggest that SRS is coupled to the Langmuir decay
interaction (LDI). The effects of LDI on the saturation of the SRS backscattering have
been investigated, considering typical parameters from recent experiments. Detailed
simulations with the coupled mode equations in a finite length plasma, with real wave
envelopes and no wave dephasing, are explored here for the first time. A detailed
description and analysis of such simulations is provided. The excitation of LDIis
found to reduce the SRS reflectivity; the reduction is appreciable in the weak EPW
damping limit. The reflectivity is also observed to increase with the damping of
ion acoustic waves, the length of the plasma, the intensity of the laser, and the
initial amplitude of the noise fluctuations. Possible cascadings of LDIha ve also been
investigated. While the cascading of LDIis found to increase the SRS backscattering,
the cascading of SRS is found to reduce it. Considering only the coupling to LDI, our
model fails to quantitatively predict the experimental SRS backscattering; however,
the calculated backscattering is found to vary in a manner similar to the experimental
observations, and our simulations explain interesting physics in the ICF laser-plasma
interactions.
Description
Thesis Supervisor: Abraham Bers
Title: Professor of Electrical Engineering & Computer Science
Subjects
SRS, LDI, ICF, EPW
MIT Department
Massachusetts Institute of Technology. Research Laboratory of Electronics
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