DYNAMIC EFFECTS ON SYMMETRIZATION IN INDIRECTLY DRIVEN INERTIAL CONFINEMENT FUSION HOHLRAUM TARGETS

A simple dynamic model is developed for the investigation of the hohlr aum symmetrization by estimating the time changes of the optical geome try of the components under the influence of hohlraum radiation. The e xpansion of the converters heated by ion beams is also included. By pe rforming dynamic simulations of the hohlraum target, it is found that the change in hohlraum geometry due to hydrodynamic expansion has a cr ucial effect on symmetrization. It is also found that the symmetry is now strongly dependent on time, and the optimal condition can only be satisfied for a limited time interval. An improved version of the hohl raum target is discussed, which may considerably increase the optimal time interval. This concept includes the suppression of the dynamic ex pansion by using low-Z gas in the hohlraum, the reduction of the optic al expansion of the converter by using low-Z material, and modificatio n of the shield configuration.