PAIR PRODUCTION BY ULTRAINTENSE LASERS

We consider the production of electron-positron pairs by the interacti on of relativistic superthermal electrons, generated by ultraintense l aser pulses, with high-Z material. We discuss the laser and target par ameters required in order to optimize the pair-production rate. We exp lore the regime when the pairs, if sufficiently confined, can start to exponentiate in number and explore the feasibility of achieving a pai r density approaching 10(21) cm(-3), 1/50 th that of solid-ion density . [S0031-9007(98)07766-7].