Wave Coupling Instabilities via Electron Plasma Waves

Abstract

This chapter describes the laser–plasma instabilities where one of the daughter wave is an electron-plasma weave (EPW) and the pump wave an intense laser: these are stimulated Raman scattering, two-plasma decay and ion acoustic decay instabilities. The description of each instability includes a discussion of the most unstable scattering geometries and a derivation of the key metrics to quantify the instability (coupled mode equations, growth rate, amplification factor). We discuss the measurement of light at half-harmonics of the laser frequency, which constitutes a key experimental signature of high amplitude electron plasma waves excited by these instabilities near the quarter-critical density. Another important consequence of these instabilities is the generation of suprathermal electrons, which are a crucial phenomenon for laser fusion experiments. The last section describes the measurement of these electrons via the bremsstrahlung radiation they emit during collisions with background plasma ions.