Pair Production by Ultraintense Lasers

We consider the production of electron-positron pairs by the interaction of relativistic superthermal electrons, generated by ultraintense laser pulses, with high- $Z$ material. We discuss the laser and target parameters required in order to optimize the pair-production rate. We explore the regime when the pairs, if sufficiently confined, can start to exponentiate in number and explore the feasibility of achieving a pair density approaching ${10}^{21}\mathrm{cm}{}^{-3\mathrm{}}$, $\frac{1}{50}\mathrm{th}$ that of solid-ion density.