Measurement of Growth Rates and Temporal Behavior of Stimulated Raman Scattering in a CO2-Laser-Produced Plasma

The stimulated-Raman-scattering instability in a C${\mathrm{O}}_2$-laser-produced plasma is studied by picosecond-resolution Thomson scattering. The instability first appears near $\frac{0.25n}{n_c}$ and is observed to propagate to lower densities at the group velocity of electron plasma waves. Temporal growth rates are measured over the whole investigated density range ($0.15<~\frac{n}{n_c}<~0.25$) and are found to be 5 times smaller than absolute rates theoretically predicted for a finite plasma.