Evolution of stimulated Brillouin to stimulated ion Compton scattering in a CO2 laser – plasma interaction experiment

Strong backscatter [Formula: see text] has been observed in the interaction of focused CO2 laser radiation (I ~ 1012 W/cm2) with a hydrogen gas target plasma. Spectral measurements show it to arise from stimulated ion Compton scattering (SCS) at later times when the electron–ion temperature ratio is not large. The scattering growth rate γ was determined experimentally to be 3.4 × 1012 s−1, in good agreement with theoretical predictions for our plasma parameters. Temporal modulation of the backscatter clearly shows build-up and decay of SCS during the interaction time. It may be anticipated that such scattering will be important in laser–pellet fusion experiments.