Experimental observation of parametric instabilities at laser intensities relevant for shock ignition
We report measurements of parametric instabilities and hot electron generation in
a laser intensity regime up to 6 × 1015W/cm2, typical of the shock ignition approach to inertial
fusion. Experiments performed at the PALS laboratory in Prague show that the incident laser
energy losses are dominated by Stimulated Brillouin Scattering (SBS) rather than by Stimulated
Raman Scattering (SRS) or Two-Plasmon Decay (TPD). Results are compared to hydrodynamics
simulations using a code that includes self-consistent calculations of non-linear laser plasma
interactions and accounts for the laser intensity statistics contained in the beam speckles. Good
agreement is found for the backscattered SRS light, and for temperature and flux of hot electrons.
The effect of high-intensity speckles on backscattered SRS is also underlined numerically
and experimentally.