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Electron kinetic effects on Raman backscatter in plasmas
M S Hur1, R R Lindberg, A E Charman
1Center for Advanced Accelerators, KERI, Changwon, Kyongnam 641-120, Korea.
Physical Review Letters
|October 4, 2005
Summary
We introduce kinetic thermal corrections to Raman backscatter (RBS) equations. These corrections measure detuning and show trapped particles can significantly suppress RBS in plasma amplifiers.
Area of Science:
- Plasma physics
- Laser-plasma interactions
- Kinetic theory
Background:
- Raman backscatter (RBS) is a key process in laser-plasma interactions.
- Standard fluid models do not fully capture kinetic effects influencing RBS saturation.
- Understanding these effects is crucial for applications like inertial confinement fusion.
Purpose of the Study:
- To incorporate kinetic thermal corrections into three-wave equations for Raman backscatter.
- To analyze the impact of these corrections on RBS saturation and dynamical detuning.
- To identify optimal operating regimes for Raman plasma amplifiers to mitigate kinetic effects.
Main Methods:
- Augmenting standard three-wave cold-fluid equations with kinetic thermal corrections.
- Performing closed-form analysis using a homogeneous kinetic three-wave model.
- Conducting kinetic simulations for a more realistic pulsed laser scenario.
Main Results:
- The magnitude of kinetic thermal corrections quantifies dynamical detuning between waves.
- Trapped particles play a significant role in the saturation of Raman backscatter.
- A small fraction of trapped particles (approx. 6%) can substantially suppress backscatter.
Conclusions:
- Kinetic thermal effects are important for accurate modeling of Raman backscatter.
- Trapped particles offer a mechanism to control and reduce unwanted backscatter.
- Operating regimes can be optimized to minimize deleterious kinetic influences in plasma amplifiers.