Following the fuel ignition achieved at NIF in 2022, Inertial Confinement Fusion research entered a new era and is transitioning toward the investigation of schemes devoted to the efficient production of Inertial Fusion Energy. The impact of laser-plasma instabilities (LPI) remains however a great concern, since they can scatter a large amount of energy, increasing the energy requirements for the laser driver, and can generate large fluxes of suprathermal hot electrons (HEs), able to preheat the cold fuel preventing the ignition of the fuel.
The issue is particularly serious in the direct-drive Shock Ignition (SI) advanced scheme, where the final laser spike is expected to reach ~10¹⁶ W/cm², i.e. an order of magnitude higher than in the classical direct-drive scheme. Moreover, the spike impinges on a plasma corona with large density and velocity scalelength, where convective growth of LPI is strongly favoured.
Despite the intensive investigation in the last 30 years, a full understanding of laser-plasma interaction in direct-drive and SI conditions is still inadequate for the difficulty of performing full-scale and multi-beam experiments and simulations. Experiments aimed at investigating laser-plasma interaction in conditions as close as possible to those envisaged in DD and SI schemes are therefore needed.
At the same time, it is necessary identifying the proper ways to tune or mitigate the effects of such instabilities to reach an effective compression and ignition of the fuel. Recently, a large effort of the ICF community is devoted to the theoretical and experimental investigation of possible mitigation of LPI by using broadband laser pulses (). The mechanism relies on the reduction of the temporal coherence of the laser beam, which can become shorter than the growth time of LPI for sufficiently large bandwidths, and therefore inhibit their growth. Another approach is using chirped laser pulses, where laser frequency sweeps with time, modifying the interaction with the plasma.
In this talk recent experimental results obtained by the ILIL team in campaigns at VULCAN (RAL-CLF, UK) and PHELIX (GSI, Germany) laser facilities, where chirped and broadband laser pulses were used, will be summarized. Experiments were aimed at testing the effect of temporal coherence and frequency chirp on the growth of Back SRS, Side SRS, SBS and TPD as well as on the generation of HEs. Next experiments and perspectives of the ILIL team devoted to LPI will finally be presented.

laser-plasma instabilities, Inertial Confinement Fusion, broadband