Dense Electron-Positron Plasmas and Ultraintense γ rays from Laser-Irradiated Solids

In simulations of a 10 PW laser striking a solid, we demonstrate the possibility of producing a pure electron-positron plasma by the same processes as those thought to operate in high-energy astrophysical environments. A maximum positron density of ${10}^{26}text{ }text{ }{mathrm{m}}^{ensuremath{-}3}$ can be achieved, 7 orders of magnitude greater than achieved in previous experiments. Additionally, $35%$ of the laser energy is converted to a burst of $ensuremath{gamma}$ rays of intensity ${10}^{22}text{ }text{ }mathrm{W}text{ }{mathrm{cm}}^{ensuremath{-}2}$, potentially the most intense $ensuremath{gamma}$-ray source available in the laboratory. This absorption results in a strong feedback between both pair and $ensuremath{gamma}$-ray production and classical plasma physics in the new “QED-plasma” regime.