Experiments were performed with CH, Be, C, and SiO2 ablators interacting with high-intensity UV laser radiation (5 × 1015 W/cm2, λ = 351 nm) to determine the optimum material for hot-electron production and strong-shock generation. Significantly more hot electrons are produced in CH (up to ∼13% instantaneous conversion efficiency), while the amount is a factor of ∼2 to 3 lower in the other ablators. A larger hot-electron fraction is correlated with a higher effective ablation pressure. The higher conversion efficiency in CH is attributed to stronger damping of ion-acoustic waves because of the presence of light H ions.

Experiments on strong shock excitation in spherical plastic targets conducted at the Omega Laser Facility are interpreted with the radiationhydrodynamics code CHIC to account for parametric instabilities excitation and hot-electron generation. The eects of hot electrons on the shock-pressure amplication and upstream preheat are analyzed. It is demonstrated that both eects contribute to an increase in the shock velocity. Comparison of the measured laser reectivity and shock ash time with numerical simulations make it possible to reconstitute the time history of the ablation and shock pressures. Consequences of this analysis for the shock-ignition target design are discussed.2

The Shock Ignition scheme is an alternative approach, which aims to achieve ignition of fusion reactions in two subsequent steps: first, the target is compressed at a low implosion velocity and second, a strong converging shock launched during the stagnation phase ignites the hot spot. In this paper we describe the major elements of this scheme and recent achievements concerning the laser-plasma interaction, the crucial role of hot electrons in the shock generation, the shock amplification in the imploding shell and the ignition conditions.