Target design activities for the European study group: heavy ion ignition facility

Target studies are an essential part of the activity of the Study Group proposed by several European institutions in order to assess the feasibility of heavy-ion-driven inertial confinement fusion ignition with beam energy below 2 MJ. The reference targets are two-side illuminated hohlraums enclosing a spherical fusion capsule. At present several codes are used to study various aspects of target evolution: hohlraum energetics and capsule implosion are studied by 1D radiation hydrocodes, symetrization in the hohlraum by viewfactor codes and implosion symmetry and stability aspects by 2D hydrodynamics simulations. It is found that achievment of ignition at the above energy level requires shaped radiation pulses (at least three steps) and good control of instabilities and that a crucial uncertainty concerns the trade-off between symmetrization and energy transfer in the hohlraum. Another essential aspect is the compatibility of the beam focusing scheme with the radiation converters. The study of such aspects requires the development of an integrated code that can simulate the entire evolution of a target with complex structure. The first steps for the construction of such a code are outlined. Results on Rayleigh-Taylor instabilities and on the physics of ignition and burn are also summarized.