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High-Energy Radiation and Pair Production by Coulomb Processes in Particle-In-Cell Simulations

We present a Monte Carlo implementation of the Bremsstrahlung, Bethe-Heitler and Coulomb Trident processes into the particle-in-cell (PIC) simulation framework. In order to address photon and electron-positron pair production in a wide range of physical conditions, we derive Bremsstrahlung and Bethe-Heitler cross sections taking account of screening effects in arbitrarily ionized plasmas. Our calculations are based on a simple model for the atomic Coulomb potential that describes shielding due to both bound electrons, free electrons and ions. We then describe a pairwise particle interaction algorithm suited to weighted PIC plasma simulations, for which we perform several validation tests. Finally, we carry out a parametric study of photon and pair production during high-energy electron transport through micrometric solid foils. Compared to the zero-dimensional model of J. Myatt et al. [Phys. Rev. E 76, 066409 (2009)], our integrated one-dimensional simulations pinpoint the importance of the electron energy losses resulting from the plasma expansion.