ABSTRACT
In inertial confinement fusion (ICF) a spherical shell filled with DT is compressed to very high densities and temperatures to achieve thermonuclear burn. An ignition target design in ICF relies on accurate control of the main fuel entropy and the asymmetry growth due to the hydrodynamic instabilities developed during the implosion (Atzeni and Meyer-Ter-Vehn, 2004). Both shell entropy and instability seeding are set during the early stage of implosion. The laser drive pulse for a direct-drive ignition target design (McKenty et al., 2001) consists of a low-intensity “foot” with I ∼ 2− 7× 1013 W/cm2 followed by the main drive pulse with peak intensity ∼ 1015 W/cm2. The shock wave launched at the beginning of the foot pulse controls the shell entropy. The shell asymmetry evolution during the shock transit determines the initial conditions for the Rayleigh-Taylor (RT) instability (Chandrasekhar, 1961) developed at the ablation surface during the shell acceleration. Thus, an accurate modeling of plasma conditions at the early stage is crucial for designing a robust ignition target.
