Implosion motion and fuel compression in direct or indirect driven target

Abstract

When a one-shell three-layer cryogenic target is irradiated by a driver beam of total energy 10 MJ and pulse width 30 ns, the pusher pressure increases to 1013 Pa, accelerating fuel toward target center, and the fuel implosion velocity reaches 3 × 105 m/s. A spherical hollow target plays the role of a supersonic converging nozzle, and the fuel is compressed to 269 times the solid density in the supersonic region and to 3·51 × 104 times in subsonic region. Nonuniform beam-energy-deposition in pusher layer causes nonuniform pusher pressure and hence nonuniform implosion, which reduces fuel compression significantly. The smoothing of pusher pressure by radiative energy transfer, or gas-filled target instead of cryogenic hollow target can be used to reduce the defect of nonuniform implosion. At last, the structure of an indirect driven target is proposed to smooth out pusher pressure in spite of nonuniform beam irradiation.