Stimulated Raman backscattering in the presence of ion-acoustic fluctuations
Threshold conditions are analyzed for stimulated Raman backscattering (SRS) from an underdense plasma in the presence of ion-acoustic fluctuations. For typical ion-acoustic spectra which could result from a Brillouin instability occurring simultaneously with SRS, a reduced collisional threshold due to induced bremsstrahlung is found for the Raman instability. Similarly, for inhomogeneous plasma the phase mismatch created by a density gradient can be compensated for by an inhomogeneity in the ion-acoustic spectrum; as a consequence, the inhomogeneity threshold for absolute instability can be substantially reduced. Comparisons are made with experimental observations of stimulated Raman scattering in the presence of strong stimulated Brillouin scattering for CO/sub 2/ laser-plasma interaction. It is found theoretically that for fluctuation levels typical of that accompanying SBS, induced bremsstrahlung growth rates for Langmuir waves can be of the order of collisional damping rates.
- Research Organization:
- Department of Electrical Engineering, University of Alberta, Edmonton, Alberta, T6G 2G7, Canada
- OSTI ID:
- 6046694
- Journal Information:
- Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 26:4; ISSN PFLDA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
700108* -- Fusion Energy-- Plasma Research-- Wave Phenomena
AMPLITUDES
BACKSCATTERING
BASIC INTERACTIONS
BEAMS
COHERENT SCATTERING
DISPERSION RELATIONS
ELECTROMAGNETIC INTERACTIONS
ENERGY
EQUATIONS
FLUCTUATIONS
INTERACTIONS
ION ACOUSTIC WAVES
ION WAVES
PLASMA
PLASMA WAVES
POLARIZED BEAMS
RAMAN EFFECT
SCATTERING
THRESHOLD ENERGY
VARIATIONS