Ricerc@Sapienza

Parametric instabilities at laser intensities in the range (2-6) x 10(15) W/cm(2) (438 nm, 250 ps, 100-300 J) have been investigated in planar geometry at the Prague Asterix Laser System facility via calorimetry and spectroscopy. The density scalelength of the plasma was varied by using an auxiliary pulse to form a preplasma before the arrival of the main laser beam and by changing the delay between the two pulses.

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