Design of a distributed radiator target for inertial fusion driven from two sides with heavy ion beams

We describe the status of a distributed radiator heavy ion target design. In integrated calculations this target ignited and produced 390–430 MJ of yield when driven with 5.8–6.5 MJ of 3–4 GeV Pb ions. The target has cylindrical symmetry with disk endplates. The ions uniformly illuminate these endplates in a 5 mm radius spot. We discuss the considerations which led to this design together with some previously unused design features: low-density hohlraum walls in approximate pressure balance with internal low-Z fill materials, radiation symmetry determined by the position of the radiator materials and particle ranges, and early time pressure symmetry possibly influenced by radiation shims. We discuss how this target scales to lower input energy or to lower beam power. Variant designs with more realistic beam focusing strategies are also discussed. We show the tradeoffs required for targets which accept higher particle energies. Finally, the impact of the fast ignitor concept on heavy ion fusion is discussed.