Measurements of Short-Pulse Backscatter from a Gas Target

Measurements are reported of short-pulse (100 psec), 1.06-μm laser backscatter from a high-pressure nitrogen gas target. Spectral measurements clearly show the expected Brillouin red shift. The backscatter fraction saturated at ∼40% at 2×${10}^{15}$ W/${\mathrm{cm}}^2$ and what appears to be multiple Brillouin scattering in a long-gradient-length plasma is observed.