High-gain shock ignition of direct-drive ICF targets for the Laser Megajoule

High-gain shock ignition is numerically investigated for specific marginally igniting targets-targets producing thermonuclear gain less than one-extracted from two distinct target families. Homothetic transformations keeping constant the implosion velocity, the adiabat, and the in-flight aspect ratio are used to draw target families. Conventional and fast ignition (FI) directly driven targets are considered for the Laser Megajoule. It is shown that high gain can be achieved with shock ignition for designs, which do not ignite only from the laser compression. Shock ignition is achieved for different targets of the FI family, which are driven by an absorbed energy between 100 and 500 kJ and deliver thermonuclear energies between 10 and 130 MJ.