Investigation on the origin of hot electrons in laser plasma interaction at shock ignition intensities

Abstract

Shock Ignition is a two-step scheme to reach Inertial Confinement Fusion, where the precompressed fuel capsule is ignited by a strong shock driven by an intense laser pulse at intensity ∼ 1016 W/cm2. In this report we detail the results of an experiment designed to investigate the origin of hot electrons (HE) in laser-plasma interaction at intensities and plasma temperatures expected for Shock Ignition. A detailed time- and spectrally-resolved characterization of Stimulated Raman Scattering (SRS) and Two Plasmon Decay (TPD) instabilities, as well as of the generated HE, suggest that SRS is the dominant source of HE via the damping of daughter plasma waves. The temperature dependence of laser plasma instabilities was also investigated, enabled by the use of different ablator materials, suggesting that TPD is damped at earlier times for higher plasma temperatures, due to the Landau damping effect. The identification of the predominant HE source and the effect of plasma temperature on laser plasma interaction, here investigated, are extremely useful for developing the mitigation strategies for reducing the impact of HE on the fuel ignition.