Exploring polarization smoothing parameters to improve laser propagation: experiment and simulations

In the context of inertial confinement fusion energy (IFE), laser beam smoothing (LBS) is a key element to mitigate laser-plasma instabilities. These techniques typically involve spectral broadening and frequency dispersion to break spatial and temporal laser coherency. Current LBS designs have proven to be partially efficient in mitigating laser-plasma instabilities such as Stimulated Brillouin Scattering (SBS), but at the price of degrading laser performances. In order to improve those trade-offs and to design future IFE facilities, it is necessary to review present technological compromises and to optimize LBS parameters.

A recent experiment [1] dedicated to polarization smoothing implementations and their effect on SBS has been carried out at the LULI2000 facility. We use the 3D HERA platform [2] to simulate the whole experiment. HERA solves the hydrodynamics evolution and heating of the plasma, with electron thermal conduction, coupled to waves equations describing the laser propagation. By performing 3D simulations for each laser shot, we are able to reprodue the SBS level for any polarization smoothing configuration. Using an adhoc formulation relying only on laser parameters, it is now possible to compare each polarization smoothing configuration efficiency regarding SBS and transmission. We will discuss the validity domain of this approach and its limits.