Evolution of Stimulated Raman into Stimulated Compton Scattering of Laser Light via Wave Breaking of Plasma Waves

Experimental evidence for the evolution of stimulated Raman backscatter instability of laser light into stimulated Compton scattering in an initially cold plasma is presented using time and wave number resolved spectra, $w(t)$ and $w(k)$, of Thomson scattered light from plasma fluctuations. Supporting particle simulations show that the key to the spectral evolution is wave breaking of Raman plasmons, which accelerates some electrons up to 4 times the phase velocity, and the consequent return current of the bulk plasma electrons in the opposite direction.