Positron--Electron, Pair-Plasma Production on OMEGA EP

It is shown that an e$^{+}$e$^{-}$ pair-plasma can be created on OMEGA EP, a feat yet to be achieved in the laboratory. We calculate that a yield of between 10$^{11}$ and 10$^{12}$ positrons can be produced on OMEGA EP by a combination of the Bethe--Heitler conversion of hard x-ray bremsstrahlung\footnote{ J. D. Bjorken and S. D. Drell, \textit{Relativistic Quantum Mechanics}, International Series in Pure and Applied Physics (McGraw-Hill, New York, 1964); D. A. Gryaznykh, Ya. Z. Kandiev, and V. A. Lykov, JETP Lett. \textbf{67}, 257 (1998); K. Nakashima and H. Takabe, Phys. Plasmas \textbf{9}, 1505 (2002).} and the trident process,\footnote{ E. P. Liang, S. C. Wilks, and M. Tabak, Phys. Rev. Lett. \textbf{81}, 4887 (1998).} assuming a total laser energy of 5~kJ. For this expanding e$^{+}$e$^{-}$ cloud to be a plasma, there must be many particles in a Debye sphere, and the cloud must be many Debye lengths in size. A magnetic field produced by a second OMEGA EP beam will provide the necessary confinement. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-92SF19460.