Influence of gases on direct-drive cryogenic targets in laser fusion reactor with wet wall

A design space of the injection velocity of a cryogenic target for the vapor pressure in a future laser fusion reactor with a wet wall is discussed. The discussion includes gain reduction due to X-ray preheat, sphericity degradation, and melting of the cryogenic layer due to adsorption of the metal vapor in the reactor. The preliminary estimation indicates that the injection velocity of a cryogenic target insulated with a 200-μm-thick, 250 mg/cc foam layer should be >130 m/s and the vapor pressure in the reactor must be <0.07 Torr.