Nonlinear Behavior of Light-Driven Plasma Instabilities
A common feature of light-plasma coupling is the excitation of plasma instabilities by the intense laser light. The instabilities give rise to light absorption, reflection and the production of energetic particles. The nonlinear behavior of many of these instabilities has been examined in computer simulations and theory. We present a nonlinear theory for the turbulent heating due to parametric instabilities near the critical density (where the laser light frequency equals the electron plasma frequency). The linear instability is saturated by mode coupling of unstable electron plasma waves into Landau damped ones, and the electrons are heated by velocity space diffusion in the plasma waves. The theoretical predictions are in good agreement with computer simulation results. We also present computer simulations of laser light back-scattering in the underdense plasma outside the critical density due to the Raman and Brillouin instabilities. The light reflection is shown to decrease rapidly as the ratio of the light pressure to the plasma pressure is made small. Several techniques to suppress these reflective processes are demonstrated. Finally we briefly discuss recent simulations of the 2 ωpe decay instability and self-focusing.
KeywordsMicrowave Verse Zink Valeo
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