Indirectly driven target design for fast ignition with proton beams

The heavy ion beam (HIB) indirectly driven compression of a small amount of DT fuel, and its fast ignition by a beam of laser accelerated protons (PB) is considered (Roth M. et al 2001 Phys. Rev. Lett. 86 436). First, a representative working point (0.8 mg of DT at 400 g cm(-3)) has been derived analytically from the energy balance of an hypothetical power plant. Second, through self-consistent two-dimensional radiation hydrodynamic simulations with the MULTI code (Ramis R. et al 1988 Comput. Phys. Commun. 49 475) we define and optimize a HIB-driven hohlraum target to produce the above conditions; also, with ignition simulations, we determine the thermonuclear yield (similar or equal to83 MJ) and the minimum P13 energy (similar or equal to33 kJ) needed to ignite the asymmetrically compressed fuel. The target is found to be a factor 5 less sensitive to implosion asymmetries than a conventional central spot one. This allows us to reduce the hohlraum size (similar or equal to6 mm), improve the driver coupling, reduce the compression energy to the 0.8-1.2 MJ range, and have enough clearance for the installation of the PB converter foil at distances (3-4 mm) appropriate for an efficient ignition.