Overview of new high gain target design for a laser fusion power plant

Abstract We have developed a new direct-drive target design that has a predicted energy gain of 127 using a 1.3 MJ KrF laser, and a gain of 155 using 3.1 MJ. The DT fuel is surrounded by an ablator consisting of a low density CH foam filled with frozen DT. The ablator is then surrounded by a thin CH coating and a very thin high-Z overcoat. The energy gain of 127–155 is possible through the use of (1) direct-drive laser-target coupling; (2) controlled levels of radiative preheating that keeps the DT fuel on a low isentrope; (3) a short 1/4 μm laser wavelength for maximum absorption and rocket efficiencies; (4) reduction of the laser beam focal spot size during the implosion (zooming) so that the focal spot size better matches the imploding target size; and (5) ISI optical smoothing to minimize the laser nonuniformities at both high and low mode numbers. In addition to its high energy gain, this target design has several other attractive features: a low target fabrication cost; the potential for a modest-size 300 MWe power plant; the physical strength to withstand the acceleration into the chamber; and a high infrared albedo to better protect the target from preheating during the injection into the chamber.