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Multibeam stimulated brillouin scattering from hot, solid-target plasmas.
1Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, USA.
Physical Review Letters
|October 26, 2002
Summary
Experiments with six laser beams on plasma show stimulated Brillouin scattering (SBS) is seeded by electromagnetic waves. Shared ion waves and early SBS quenching due to plasma hydrodynamics were also observed in these direct-drive-ignition relevant studies.
Area of Science:
- Plasma physics
- Laser-plasma interactions
- Inertial confinement fusion
Background:
- Future direct-drive-ignition experiments require understanding complex laser-plasma interactions.
- Stimulated Brillouin scattering (SBS) is a key instability affecting laser propagation and energy coupling in plasmas.
- Preformed plasmas with critical density are crucial for simulating ignition conditions.
Purpose of the Study:
- To investigate multibeam laser-plasma interactions relevant to direct-drive-ignition.
- To identify the mechanisms seeding stimulated Brillouin scattering (SBS) in such plasmas.
- To analyze the role of shared ion waves and plasma hydrodynamics on SBS evolution.
Main Methods:
- Conducting multibeam (six beams) laser experiments on preformed plasmas.
- Utilizing diagnostics to observe stimulated Brillouin scattering (SBS) and associated wave phenomena.
- Analyzing experimental data for evidence of electromagnetic wave seeding and ion wave coupling.
Main Results:
- Strong evidence for electromagnetic wave seeding of SBS side- and backscattering.
- Data consistent with shared ion waves driven by multiple laser beams.
- Observation of early SBS quenching attributed to plasma hydrodynamics.
Conclusions:
- Electromagnetic waves play a significant role in seeding SBS in multibeam laser-plasma interactions.
- Shared ion waves are a likely consequence of symmetric multibeam illumination.
- Plasma hydrodynamics can lead to early suppression of SBS, impacting laser-plasma coupling.