Dependence of stimulated Brillouin scattering on laser intensity, laser f number, and ion species in hohlraum plasmas

Stimulated Brillouin scattering has been studied in plasma conditions approaching those expected within laser-driven cavities (hohlraums) capable of driving a fusion capsule to ignition with x rays. These conditions are achieved using a gas-filled hohlraum design that was fielded at the Nova laser. As the intensity of an interaction beam (351 nm in wavelength) is increased above an onset value I-c, the measured Brillouin backscatter into the lens rises sharply and saturates. I-c decreases as the optic f number increases. The saturation level depends on the gas ion species.